JP7148981B2 - camera structure, imaging device - Google Patents

Description

The present invention relates to a camera structure provided in an imaging device.

2. Description of the Related Art At the beginning of this century, imaging devices using solid-state imaging devices (imaging devices), so-called digital cameras, have become mainstream. In addition, information communication devices such as personal computers (PCs), tablet PCs, and smart phones have become widespread and used on a daily basis. These information communication devices often incorporate a small camera module, and at present, some of them are equipped with high-performance imaging devices with more than 10,000,000 pixels. Information communication devices, especially smartphones, which are portable communication devices, tend to be thinner and lighter, and camera modules, which are components of these devices, are also required to be downsized and space-saving. In addition, since smartphones are often the only imaging device for users, there is a strong demand for better image quality even if camera modules are made smaller.

In recent years, the need for self-driving cars has increased, and in some car models, parking, automatic braking, and night driving assistance using on-board cameras have already been put to practical use. Camera modules used in in-vehicle cameras are becoming smaller and higher in performance, and there is a strong demand for removing noise such as ghosts from images for image recognition.

When the lens of the imaging device is directed toward a light source with high light intensity, light is repeatedly reflected on the lens surface, etc., and unwanted images are captured. This phenomenon is called flare or ghost. A phenomenon in which a portion of an image is overexposed is called a flare phenomenon, and a phenomenon in which light is repeatedly reflected on the lens surface and a clear unwanted image is reflected is called a ghost phenomenon.

As shown in FIG. 11A, a camera module 1 having a conventional camera structure is mainly composed of a lens unit 50, a lens carrier 40, a magnet holder 30, an optical filter 60, and an imaging device 70. It is fixed (for example, see JP-A-2013-153361). Among them, the optical filter 60 mainly serves to cut light in the near-infrared region. Human eyes are sensitive to light in the visible region (visible light) with a wavelength of 380 nm to 780 nm. On the other hand, an imaging device generally has sensitivity to light with a longer wavelength, ie, light with a wavelength of about 1.1 μm, including visible light. Therefore, if the image captured by the imaging device is photographed as it is, the color does not look natural to the human eye, which causes a sense of incongruity. Therefore, the camera module 1 is configured to incorporate an optical filter 60 (near-infrared light cut filter) that cuts light in the near-infrared region.

As the near-infrared light cut filter 60, for example, glass containing phosphate or fluorophosphate called blue glass that absorbs light in the near-infrared region is used.

For the cover glass 10 provided in the conventional camera structure, tempered glass or sapphire glass is used as a material.

In this specification, a camera module is defined as an internal mechanism of an imaging device that is essential for imaging, such as a lens unit including an optical lens group, a lens carrier, an imaging element, and a magnet holder. The camera structure is defined as a camera module including a cover glass that protects the internal mechanism of the imaging device from the outside world.

FIG. 11B shows an explanatory diagram for explaining the experimental method of the experiment conducted with the conventional camera structure. In the experiment, a light emitting diode having a specific central wavelength was used as a light source, and the light emission was imaged. In the experiment, a light emitting diode with a center wavelength of 460 nm was used as the light source 300 . In order to make the generated flare phenomenon and ghost phenomenon easier to see, the low-reflection material 320 is placed in the background of the light source 300 and the high-reflection material 310 is placed around the low-reflection material 320 .

A conventional camera structure includes a cover glass 10, an optical lens group 50, a near-infrared light cut filter 60, and an imaging device 70 in order from the light incident side. The near-infrared light cut filter 60 is arranged between the optical lens group 50 and the imaging device 70 .

FIG. 11C is a cross-sectional view of the cover glass 10. FIG. The cover glass 10 comprises a transparent glass 360 and an antireflection film 370 . The antireflection film 370 is provided on the optical lens group 50 side of the transparent glass 360 .

FIG. 11D is a cross-sectional view of the near-infrared light cut filter 60. FIG. The near-infrared light cut filter 60 has a near-infrared light reflecting film 390 on the incident side and an anti-reflection film 370 on the imaging element 70 side with respect to the blue glass 380 that is the base material. Here, the blue glass 380 has a function of absorbing near-infrared light.

FIG. 11(E) is an image captured by the image sensor 70 having the conventional camera structure described in FIGS. 11(A) to 11(D). A petal-like ghost G is generated centering on the light source 300, and it can be seen that the image quality is degraded. Such a ghost phenomenon can occur even if the center wavelength of the light source 300 is changed from 420 nm to 660 nm.

JP 2013-153361 A

In order to reduce the ghost phenomenon and flare phenomenon, it is generally necessary to make the optical lens group provided in the camera more advanced and complicated in structure and to improve the anti-reflection coating of the lens element itself. However, this is a difficult problem for camera modules for information communication equipment and camera modules for vehicle-mounted cameras, which are required to be small, light, and inexpensive.

A major cause of the ghost phenomenon is that a near-infrared cut filter including a near-infrared reflective film is located near the imaging element. Therefore, the ghost phenomenon can be greatly suppressed by arranging the near-infrared light reflecting section on the outer side of the camera module, for example, on the cover glass as much as possible. In addition, by bringing the near-infrared light reflecting part to the outside world side, in order to prevent a shift in the cutoff wavelength of the near-infrared light that can occur when light with a large incident angle enters the camera module, The spectral characteristics of the infrared light absorbing portion and the spectral characteristics of the near-infrared light reflecting portion are adjusted so that image quality does not depend on the angle of incident light.

(1) The present invention provides a camera structure for taking an image, comprising an optical lens group arranged on a light incident side, an image sensor for receiving light incident through the optical lens group, and a near-infrared region. and a near-infrared light absorbing portion that absorbs light in the near-infrared region, wherein the near-infrared light reflecting portion and the near-infrared light absorbing portion are , to provide a camera structure characterized by being separate.

According to the above invention (1), there is a degree of freedom in where to place the near-infrared light reflecting section and where to place the near-infrared light absorbing section. This has the remarkable effect of improving image quality.

(2) In the present invention, the near-infrared light reflecting portion and the near-infrared light absorbing portion are arranged in order from the light incident side. The camera structure described in (1) above is provided.

Light having a longer wavelength than light absorbed by the near-infrared light absorbing portion may be transmitted. Therefore, when the near-infrared light absorbing portion and the near-infrared light reflecting portion are arranged in order from the light incident side, the light with a longer wavelength than the light absorbed by the near-infrared light absorbing portion is absorbed by the camera. This makes it easier for the light to enter the module, and before it reaches the near-infrared light reflection section that can cut off the light on the long wavelength side, it reflects off the lens surface and becomes stray light, causing a drop in image quality.

According to the above invention (2), since the near-infrared light reflecting portion and the near-infrared light absorbing portion are arranged in order from the light incident side, the near-infrared light reflecting portion and the near-infrared light absorbing portion are arranged. , stray light on the long wavelength side can be suppressed.

(3) The present invention is characterized in that, in the camera structure, the near-infrared light reflecting portion includes a lens element that constitutes the optical lens group, and is arranged closer to the light incident side than the lens element. to provide a camera structure according to (1) or (2) above.

According to the above invention (3), the near-infrared light reflecting portion includes a lens element that constitutes the optical lens group, and is arranged on the light incident side of the lens element. The distance from the near-infrared light reflecting portion to the imaging device is greater than the position of the filter. When the incident angle of light deviates from the vertical to the axial direction, the near-infrared light reflecting portion may easily transmit light in the ultraviolet region. As the distance from the image pickup device increases, the angle at which the near-infrared light reflection section looks into the image pickup device becomes smaller. There is an effect that it can be reduced.

(4) The present invention is characterized in that, in the camera structure, the near-infrared light absorbing section includes a lens element that constitutes the optical lens group, and is arranged closer to the imaging device than the lens element. A camera structure according to any one of (1) to (3) above is provided.

According to the above invention (4), the transmittance of the near-infrared light absorbing portion does not depend on the incident angle of light in many cases. Therefore, the near-infrared light absorbing portion includes a lens element that constitutes an optical lens group in the camera structure, and is arranged closer to the image pickup device than the lens element, so that light tends to enter the image pickup device from various directions. A remarkable effect of being able to effectively suppress stray light is exhibited.

(5) The present invention is characterized in that an imaging device cover that covers at least part of the imaging device as viewed from the light incident side is disposed between the optical lens group and the imaging device ( A camera structure according to any one of 1) to 4) is provided.

Image quality deteriorates when dust that does not easily transmit light adheres to the image sensor. According to the above invention (5), the image pickup device cover that covers at least a part of the image pickup device as viewed from the light incident side is arranged at a position close to the image pickup device between the optical lens group and the image pickup device. Therefore, it is possible to reduce the amount of dust adhering to the image pickup device and prevent the image quality from deteriorating.

(6) The present invention provides the camera structure described in (5) above, wherein the image sensor cover is made of glass.

According to the above invention (6), it is possible to inexpensively manufacture an imaging device cover that is less deformed by temperature changes.

(7) The present invention provides the camera structure described in (5) above, wherein the imaging element cover is a synthetic resin film.

A synthetic resin film having a thickness of 100 μm or less can be easily produced. According to the above invention (7), there is an effect that a thin and inexpensive imaging device cover can be manufactured at low cost.

(8) The present invention provides the camera structure according to any one of (5) to (7) above, wherein the image sensor cover has a thickness of 0.2 mm or less.

According to the above invention (8), it is possible to provide a camera module that is thinner than the conventional one.

(9) The camera according to any one of (5) to (8) above, wherein the imaging device cover has an antireflection layer that prevents reflection of light in at least the visible region. Provide structure.

The imaging device cover is arranged at a position close to the imaging device between the optical lens group and the imaging device. Therefore, when the image pickup device cover reflects light, it causes significant deterioration in the image quality of the image acquired by the image pickup device.

According to the above invention (9), the imaging device cover has an antireflection layer that prevents reflection of light in at least the visible region, thereby achieving a remarkable effect of improving image quality.

(10) The present invention is characterized in that an antireflection layer for preventing reflection of light in at least the visible region is provided on both surfaces of the imaging device cover, according to any one of the above (5) to (8). provides a camera structure for

According to the above invention (10), more incident light can be taken in, and the reflected light caused by the imaging element cover, particularly the reflected light from the imaging element itself, is further reflected by the imaging element cover. It is possible to prevent the light from returning to the image pickup device, thereby improving the image quality.

(11) The camera according to (9) or (10) above, wherein the antireflection layer has a fine protrusion structure composed of fine protrusions formed on the surface of the imaging element cover. Provide structure.

An antireflection layer having a fine projection structure, a so-called moth-eye structure, formed on the surface of the image sensor cover prevents reflection of light over a wide band. Therefore, according to the above invention (12), by forming the antireflection layer with the moth-eye structure, the reflected light caused by the image sensor cover is significantly reduced over a wide band, and the image quality can be improved. Play.

(12) The present invention provides the camera structure described in (9) or (10) above, wherein the antireflection layer is a coating film formed on the surface of the inner transparent plate.

A multilayer film in which two kinds of thin films having different refractive indices for light are alternately laminated can form an antireflection film for light. It is also known that such a multilayer film can be obtained by applying a synthetic resin. According to the above invention (12), it is possible to inexpensively mass-produce the inner transparent plate provided with the antireflection film of stable quality.

(13) The present invention provides the camera structure according to any one of (5) to (12) above, wherein the imaging device cover includes the near-infrared light absorbing portion.

According to the above invention (13), since the image sensor cover includes the near-infrared light absorbing portion, there are remarkable effects such as a reduction in the number of parts and a reduction in the number of steps in manufacturing the camera structure.

(14) The present invention is characterized in that the near-infrared light absorbing portion is a near-infrared light absorbing film that absorbs light in the near-infrared region, and contains an organic dye. ).

According to the above invention (14), the near-infrared light-absorbing portion has a near-infrared light-absorbing film, and the near-infrared light-absorbing film contains an organic dye that absorbs near-infrared light. It is possible to suppress light in the near-infrared region without using blue glass, which is generally used as a material for filters that absorb light in the near-infrared region, with little dependence on the incident angle of light. It has the effect of becoming

(15) The present invention is characterized in that the camera structure further includes a cover glass for protecting the internal mechanism of the imaging device from the outside world, and the cover glass includes the near-infrared light reflecting portion. ) to 14).

According to the above invention (15), since the cover glass has a near-infrared light reflecting film that reflects light, it is possible to prevent near-infrared light from the outside from entering the internal mechanism of the imaging device. In addition, since there is no need to put a member with a near-infrared light reflecting film in the area close to the imaging device, reflection of light incident on the internal mechanism of the imaging device can be suppressed, resulting in suppression of stray light. , can be effective in reducing the causes of ghosts and flares.

(16) The present invention provides a camera structure for taking an image, comprising an optical lens group arranged on a light incident side, an image sensor for receiving light incident through the optical lens group, and a near infrared region. and a near-infrared light absorbing portion that absorbs light in the near-infrared region, wherein the near-infrared light reflecting portion and the near-infrared light absorbing portion are , is included in an integral optical element included in the optical lens group.

According to the above invention (16), since the optical lens group includes an integral optical element including both the near-infrared light reflecting portion and the near-infrared light absorbing portion, the near-infrared light It is no longer necessary to insert a member with a reflective film. Therefore, it is possible to suppress the reflection of light incident on the internal mechanism of the imaging device, and as a result, it is possible to suppress the stray light and reduce the causes of ghost and flare.

(17) The present invention includes a near-infrared light absorbing portion that absorbs light in the near-infrared region and a near-infrared light reflecting portion that reflects light in the near-infrared region, wherein the near-infrared light absorbing portion has a light absorption wavelength region in which the light transmittance is less than 2% in the region of 685 nm to 755 nm as the wavelength of light, and although the wavelength of incident light to the near-infrared light reflecting portion increases, When the near-infrared light cutoff wavelength is defined as the wavelength at which the light transmittance decreases to 50%, the near-infrared light reflective part emits light having a wavelength longer than the near-infrared light cutoff wavelength. When the angle of incidence of light incident on the near-infrared light reflecting portion is changed in the range of 0° to 30°, the near-infrared light cutoff wavelength is always A camera structure is provided, characterized in that it falls within a light absorption wavelength range.

As a combined effect of the near-infrared light absorbing portion and the near-infrared light reflecting portion, when the transmittance of light at a predetermined wavelength is 1% or more, an acquired image is affected. Therefore, as the spectral characteristics of the near-infrared light absorbing portion, when the light transmittance of the near-infrared light reflecting portion reaches 50% in the light wavelength region in which the light transmittance is 2% or more, the image quality of the obtained image is visually impaired. The color will be different. Also, when the near-infrared light reflecting portion is formed of, for example, a dielectric multilayer film, the light transmittance varies depending on the incident angle of the incident light. are different, and a so-called "red dropout" phenomenon of deterioration of image quality occurs. In particular, when the infrared reflective section is arranged on the outside of the camera module, specifically on the cover glass, light with a large incident angle can enter the camera module, and this deterioration in image quality becomes significant.

According to the invention described in (17) above, the combined effect of the near-infrared light absorbing portion and the near-infrared light reflecting portion is light longer than the near-infrared light cutoff wavelength in the light wavelength region of 685 nm to 755 nm. Since the transmittance of light is less than 1% in the wavelength region, there is also the excellent effect of reducing the difference between the image quality of the obtained image and the image seen with the naked eye. In addition, when the incident angle of the incident light to the near-infrared light reflecting portion is changed in the range of 0° to 30°, the near-infrared light cutoff wavelength of the near-infrared light reflecting portion always has a light transmittance of 2. %, the incident angle dependence of spectral characteristics for light in the near-infrared region is reduced, and the light wavelength dependence of transmittance does not change between the peripheral and central parts of the acquired image. An excellent effect of improving image quality is exhibited.

(18) The present invention includes a near-infrared light absorbing portion that absorbs light in the near-infrared region and a near-infrared light reflecting portion that reflects light in the near-infrared region, wherein the near-infrared light absorbing portion has a light absorption wavelength range in which the light transmittance is less than 2% in the light wavelength range of 685 nm to 755 nm, and the near-infrared light reflecting portion has a light transmittance reduced to 50 % is defined as the near-infrared light cutoff wavelength, it has a characteristic of substantially totally reflecting light with a wavelength longer than the near-infrared light cutoff wavelength, and the incident light to the near-infrared light reflecting portion The above (1) to the above, wherein the near-infrared light cutoff wavelength is always included in the light absorption wavelength region when the incident angle of light is changed in the range of 0° to 30°. (16) to provide a camera structure according to any one of (16).

When the near-infrared light reflecting section is provided on the side of the camera structure near the outside, for example, on a cover glass, even light with a large incident angle enters the camera structure. When the near-infrared light reflecting portion is formed of, for example, a dielectric multilayer film, the light transmittance changes depending on the incident angle of the incident light. The optical wavelength dependence of the transmittance differs between the central portion and the central portion, and a so-called "red dropout" phenomenon of deterioration of image quality occurs.
According to the invention described in (18) above, when the incident angle of the incident light to the near-infrared light reflecting portion is changed in the range of 0° to 30°, the near-infrared light of the near-infrared light reflecting portion always Since the external light cutoff wavelength falls within the light absorption wavelength region where the light transmittance is less than 2%, the incident angle dependence of the spectral characteristics of light in the near-infrared region is reduced, and the peripheral and central portions of the acquired image are Since the wavelength of light that can be obtained does not change, the image quality is improved, which is an excellent effect.

In addition, as an effect of combining the infrared light absorbing portion and the near infrared light reflecting portion, the light transmittance is 1% in the light wavelength region longer than the near infrared light cutoff wavelength in the light wavelength region of 685 nm to 755 nm685 nm to 755 nm. Since it is less than 100 mm, there is also the excellent effect of reducing the difference between the image quality of the obtained image and that seen by the naked eye.

(19) The present invention provides a cover glass that protects the internal mechanism of an imaging device from the outside world, an optical lens group arranged on the cover glass side, and an imaging device that receives light incident through the cover glass and the optical lens group. The cover glass has a transparent substrate that transmits light, the near-infrared light absorbing portion, and the near-infrared light reflecting portion, and an optical path from the optical lens group to the imaging device Provided is the camera structure described in (17) above, characterized in that no near-infrared light cut filter for cutting light in the near-infrared region is disposed therebetween.

Since the near-infrared light reflecting portion is provided on the side of the camera structure closest to the outside, that is, on the cover glass, even light with a large incident angle enters the camera structure. When the near-infrared light reflecting portion is formed of, for example, a dielectric multilayer film, the light transmittance changes depending on the incident angle of the incident light. As a result, a so-called "red dropout" occurs, which deteriorates the image quality.

According to the invention described in (19) above, when the incident angle of the incident light to the near-infrared light reflecting portion is changed in the range of 0° to 30°, the near-infrared light Since the external light cutoff wavelength falls within the light absorption wavelength region where the light transmittance is less than 2%, the incident angle dependence of the spectral characteristics of light in the near-infrared region is reduced, and the peripheral and central portions of the acquired image are Since the light wavelength dependence of the transmittance does not change, the excellent effect of improving the image quality is exhibited.

In addition, as a combined effect of the infrared light absorbing portion and the near-infrared light reflecting portion, light is emitted in a light wavelength region longer than the near-infrared light cutoff wavelength in the light wavelength region of 685 nm to 755 nm. Since the transmittance is less than 1%, there is also the excellent effect of reducing the difference between the image quality of the captured image and what is seen with the naked eye.

Furthermore, since a near-infrared light cut filter for cutting light in the near-infrared region is not arranged between the optical paths from the optical lens group to the image pickup device, the height of the entire camera structure can be reduced.

(20) The present invention is a camera structure comprising a near-infrared light cut filter that cuts off light in the near-infrared region, wherein the near-infrared light cut filter cuts light when the wavelength of incident light is increased. If the wavelength at which the transmittance of decreases to 10% is defined as the near-infrared light cutoff wavelength, the near-infrared light cutoff wavelength when the incident angle of the incident light is changed in the range of 0 ° to 30 ° Provided is a camera structure characterized by an angular dependent change width of 5 nm or less.

When the near-infrared light cut filter has, for example, a near-infrared light reflecting portion including a dielectric multilayer film, the wavelength dependence of light transmittance in the near-infrared light reflecting portion changes depending on the incident angle of incident light. . That is, for example, the near-infrared light cut-off wavelength of the near-infrared light reflecting portion is about 700 nm when the incident angle of the incident light is 0°, but becomes about 675 nm when the incident angle of the incident light is 30°. Such incident angle dependence may occur. Then, assuming that the near-infrared light cut filter has a near-infrared light absorbing portion, the light transmittance realized by combining with the near-infrared light reflecting portion may change greatly depending on the incident angle of the incident light. . Specifically, a near-infrared light cut filter having a near-infrared light reflecting portion and a near-infrared light absorbing portion cuts off near-infrared light when the incident angle of incident light is changed in the range of 0° to 30°. The angle-dependent change width of the wavelength may be about 30 nm. Conversely, at a predetermined light wavelength in the near-infrared light region, the light transmittance of the near-infrared light cut filter largely fluctuates depending on the incident angle of the incident light. For example, if light with a wavelength of 660 to 690 nm is incident, the light transmittance is about 20% when the incident angle is small at the center of the acquired image, and the light transmittance is about 20% when the incident angle is large at the periphery of the acquired image. As a result, the optical wavelength dependence of the transmittance differs between the periphery and the center of the obtained image, resulting in a so-called "red spot", which deteriorates the image quality.

According to the invention described in (20) above, in the near-infrared light cut filter, the angle-dependent change width of the near-infrared light cutoff wavelength when the incident angle of the incident light is changed in the range of 0° to 30° is Since the thickness is 5 nm or less, it is difficult for a difference in color representation to occur in an acquired image, and an excellent effect of improving the image quality is exhibited.

(21) The present invention includes a near-infrared light absorbing portion that absorbs light in the near-infrared region and a near-infrared light reflecting portion that reflects light in the near-infrared region, wherein the near-infrared light absorbing portion The light transmittance of the light wavelength is less than 2% in the range of 700 nm to 750 nm, the light wavelength is in the range of 630 nm to 750 nm, and the light transmittance is 2% or more. The frequency dependence curve of the light transmittance of the light absorbing portion is obtained from the frequency dependence curve of the light transmittance of the near-infrared light reflecting portion when the incident angle of incidence on the near-infrared light reflecting portion is 0° to 30°. is on the short wavelength side.

According to the invention described in (21) above, even if a phenomenon occurs in which the wavelength dependence of light transmittance in the near-infrared light reflecting portion changes depending on the incident angle of incident light, the near-infrared light reflecting portion and the near-infrared light reflecting portion Since the spectral characteristics of the light transmittance in the near-infrared light region when considering the external light absorption part together are governed by the spectral characteristics of the light transmittance of the near-infrared light absorption part, the color in the acquired image It becomes difficult for the difference in expression to occur, and the excellent effect of improving the image quality is exhibited.

(22) The present invention provides an imaging apparatus having the camera structure according to any one of (1) to (21).

According to the above invention (22), it is possible to inexpensively realize an image pickup apparatus having a camera structure with improved image quality compared to the conventional one.

According to the present invention, there is a degree of freedom in where to place the near-infrared light reflecting section and where to place the near-infrared light absorbing section. , a remarkable effect of improving the image quality in the imaging device can be obtained.

1A is a cross-sectional view of a camera structure applied to a mobile communication device A, which is an imaging device according to a first embodiment of the present invention; FIG. (B) is a structural diagram of a cover glass with a near-infrared light reflecting function including a near-infrared light reflecting portion. (C) is a structural diagram of an imaging device cover with a near-infrared light absorbing function including a near-infrared light absorbing portion. (A) is a structural diagram of a cover glass with an optical filter function. (B) is a diagram showing incident angle dependency of spectral transmittance of a near-infrared light reflective film. (C) is an explanatory diagram for explaining the definition of an incident angle. FIG. 4 is a diagram showing incident angle dependency of spectral transmittance in a cover glass with an optical filter function having a near-infrared light absorbing film and a near-infrared light reflecting film. FIG. 3 is a diagram comparing spectral transmittances of a cover glass with an optical filter function, a glass provided with a near-infrared light absorbing film, and a glass provided with a near-infrared light reflecting film. FIG. 4 is an explanatory diagram illustrating spectral transmittance of a dual-band cover glass; (A) is a cross-sectional view of a camera structure applied to a mobile communication device A, which is an imaging device according to a third embodiment of the present invention. (B) is a structural diagram of a cover glass with a near-infrared light reflecting function including a near-infrared light reflecting portion. (C) A structural diagram of a plate with a near-infrared light absorption function. (D) is a structural diagram of an imaging device cover including a plurality of antireflection layers using transparent glass as a base material. (E) is a structural diagram of an imaging cover using a transparent synthetic resin film as a base material having a moth-eye structure exhibiting an antireflection function on both sides. (A) A cross-sectional view of a camera structure applied to a mobile communication device A, which is an imaging device according to a fourth embodiment of the present invention. (B) is a cross-sectional view of a lens unit including an optical lens element having a near-infrared light absorbing portion; (C) is a cross-sectional view of a lens unit including an optical lens element having a near-infrared light absorbing portion. (A) is a cross-sectional view of a camera structure applied to an imaging device according to a fifth embodiment of the present invention; (B) is a cross-sectional view of a lens unit including an optical lens element including a near-infrared light reflecting portion and an optical lens element including a near-infrared light absorbing portion; (A) is a cross-sectional view of a camera structure applied to an imaging device according to a sixth embodiment of the present invention; (B) is a cross-sectional view of a lens unit provided with an optical element with a near-infrared light absorbing function that includes a near-infrared light absorbing portion. (C) is a structural diagram of an optical element with a near-infrared light absorption function. (A) is a cross-sectional view of a camera structure applied to an imaging device according to a seventh embodiment of the present invention; (B) is a cross-sectional view of a lens unit provided with an optical element with an optical filter function including a near-infrared light reflecting portion and a near-infrared light absorbing portion. (C) is a structural diagram of an optical element 530 with an optical filter function. (A) is a cross-sectional view of a conventional camera structure in a mobile communication device; (B) is an explanatory diagram for explaining an experimental method of an experiment conducted with a conventional camera structure. (C) is a cross-sectional view of a conventional cover glass. (D) is a cross-sectional view of a conventional near-infrared cut filter. (E) Image taken with a conventional camera configuration. (A) is a graph showing the spectral characteristics of the light transmittance in a near-infrared light absorbing portion using a conventional light-absorbing ink, and the dependence of the spectral characteristics of the light transmittance in the near-infrared light reflecting portion on the incident light angle. . (B) is a graph showing incident light angle dependence of spectral characteristics of light transmittance when a near-infrared light absorbing portion and a near-infrared light reflecting portion are combined. (A) Spectral characteristics of light transmittance in the near-infrared light absorbing portion using light-absorbing ink with a wider light absorption band than conventional in the near-infrared light region, and light transmittance spectroscopy in the near-infrared light reflecting portion It is a graph which shows the incident light angle dependence of a characteristic. (B) is a graph showing incident light angle dependence of spectral characteristics of light transmittance when a near-infrared light absorbing portion and a near-infrared light reflecting portion are combined. (A) is a cross-sectional view of a camera structure applied to a mobile communication device A, which is an imaging device according to a ninth embodiment of the present invention; (B) is a structural diagram of a cover glass with an optical filter function provided with a plurality of antireflection films.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 to 10 and 12 to 14 are examples of embodiments for carrying out the invention, and parts with the same reference numerals in the figures represent the same parts.

FIG. 1A is a cross-sectional view of a camera structure applied to a mobile communication device A, which is an imaging device according to the first embodiment of the present invention.

The camera structure includes a cover glass 215 with a near-infrared light reflecting function that protects the internal mechanism of the imaging device from the outside world, and the camera module 1 . The camera module 1 includes an optical lens group that is an internal mechanism of an imaging device, that is, a lens unit 50, a lens carrier 40 that holds the lens unit 50, and an axial movement of the lens unit 50 to realize an autofocus function. The magnet holder 30, the cover glass 215 with a near-infrared light reflecting function, and the imaging device 70 that receives incident light via the lens unit 50, are arranged between the lens unit 50 and the imaging device 70, and transmit the light. An imaging device cover 244 with a near-infrared light absorbing function is provided, which uses transparent glass as a base material. The image sensor cover 244 with a near-infrared light absorption function covers at least part of the surface of the image sensor 70 when the image sensor 70 is viewed from the lens unit 50 side in the axial direction.

FIG. 1B is a structural diagram of a cover glass 215 with a near-infrared light reflecting function including a near-infrared light reflecting portion. The cover glass 215 with near-infrared light reflecting function uses crystallized glass 130 as a transparent substrate that transmits light, and has an antireflection film 120 that reflects light in the ultraviolet region and suppresses reflection of light in the visible region. is formed on the light incident side with the crystallized glass 130 as a reference. An antifouling coating film 110 for preventing contamination from the outside is provided on the outermost side of the light incident side. On the light exit side, an antireflection film 120 and a near-infrared light reflecting film 150, which is a near-infrared reflecting portion that reflects light in the near-infrared region, are formed in order from the farthest side with respect to the crystallized glass 130. do.

In addition, in the cover glass 215 with a near-infrared light reflecting function, the antireflection film 120 closest to the imaging device 70 may be omitted.

FIG. 1(C) has a plurality of antireflection layers 230 that prevent reflection of light in at least the visible region, and further includes a near-infrared light absorbing film 140 that is a near-infrared light absorbing portion. 4 is a structural diagram of an imaging device cover 244. FIG. That is, the imaging element cover 244 with near-infrared light absorption function is provided on both sides with the antireflection layers 230 that prevent reflection of at least light in the visible region. The antireflection layer 230 has a material and structure similar to those of the antireflection film 120, and the manufacturing method is also the same.

The imaging element cover 244 with near-infrared light absorbing function has a transparent glass 220 as a base material, and the near-infrared light absorbing film 140 is provided adjacent to the transparent glass 220 . The antireflection layer 230 is formed on the light incident side with respect to the transparent glass 220, and on the light exit side with respect to the transparent glass 220, the antireflection layer 230 and the near-infrared light absorption film are arranged in this order from the farthest side with respect to the transparent glass 220. 140 are provided.

That is, the camera structure applied to the mobile communication device A, which is the imaging device according to the first embodiment of the invention, includes an optical lens group (optical unit 50) arranged on the incident side of light, and an incident light through the lens unit 50. an imaging element 70 that receives the light that has been emitted, a near-infrared light reflecting film 150 that is a near-infrared light reflecting portion that reflects light in the near-infrared region, and a near-infrared light absorption that absorbs light in the near-infrared region The camera structure is characterized in that it includes a near-infrared light absorbing film 140 that is a portion, and that the near-infrared light reflecting portion and the near-infrared light absorbing portion are formed separately. The near-infrared light reflecting film 150, which is the near-infrared light reflecting portion, and the near-infrared light absorbing film 140, which is the near-infrared light absorbing portion, are arranged in order from the light incident side. It is arranged with the infrared light absorbing film 140 . A near-infrared light reflecting film 150, which is a near-infrared light reflecting portion, includes a lens element that constitutes the lens unit 50 in the camera structure, and is arranged on the light incident side of the lens element. A near-infrared light absorbing film 140, which is a near-infrared light absorbing portion, includes a lens element that constitutes the lens unit 50 in the camera structure, and is arranged closer to the imaging device 70 than the lens element. An image pickup device cover 244 with a near-infrared light absorption function that covers at least part of the image pickup device 70 when viewed from the light incident side is arranged between the lens unit 50 and the image pickup device 70 . The image sensor cover 244 with a near-infrared light absorbing function includes the image sensor near-infrared light absorbing portion. The near-infrared light absorbing portion is a near-infrared light absorbing film 140 that absorbs light in the near-infrared region, and contains an organic dye. The camera structure further has a cover glass 215 with a near-infrared light reflecting function that protects the internal mechanism of the imaging device from the outside world, and the cover glass has a near-infrared light reflecting film 150 that is a near-infrared light reflecting part. include.

As a means for realizing the image sensor cover 244 with a near-infrared light absorption function, for example, a synthetic resin thin plate containing at least a part of an organic dye that absorbs light in the near-infrared region is used as a base material. Also good. Also, a so-called blue glass plate that absorbs light in the near-infrared region may be used as in the conventional near-infrared light cut filter. It is also conceivable to attach a film that cuts near-infrared light to a transparent plate.

In general, crystallized glass has large crystal grains, making it difficult for light to pass through. However, recent advances in technology have made it possible to control crystal grains to nanometer sizes, such as the shock-resistant, high-hardness clear glass-ceramics manufactured by Ohara Co., Ltd., increasing light transmittance. By using such crystallized glass, a cover glass having both impact resistance and crack-resistant fracture toughness can be produced. By forming the above laminated structure on such a cover glass, the cover glass 215 with a near-infrared light reflecting function is realized. It is theoretically conceivable to use blue glass as the cover glass 215 with the near-infrared light reflecting function, but it is not suitable because of its low impact resistance and lack of crack-resistant fracture toughness. It is conceivable to form a near-infrared light reflecting film 150, which will be described later, on tempered glass to form the cover glass 215 with a near-infrared light reflecting function. have low deficiencies. It is also conceivable to form the near-infrared light reflecting film 150 on the sapphire glass having high hardness to form the cover glass 215 with the near-infrared light reflecting function, but the cost increases remarkably and the crystallized glass 130 is used. Machinability is lower than that of the case.

The antifouling coating film 110 prevents fingerprint stains and sebum stains, and facilitates wiping off stains. The antifouling coating film 110 is formed of a fluorine-based coating agent or the like, and is formed on the outermost side of the laminated structure of the cover glass on the light incident side by coating or spraying.

The antireflection film 120 reflects light in the ultraviolet region and suppresses reflection of light in the visible region. The anti-reflection film 120 is a dielectric multilayer film, and is constructed by alternately laminating a nitride film and an oxide film. A dielectric film forming the antireflection film 120 is formed by alternately laminating a plurality of nitride films and oxide films. Silicon nitride, silicon oxynitride, aluminum nitride, or the like can be used as the nitride film. When silicon oxynitride is used, the stoichiometric ratio of oxygen and nitrogen (oxygen/nitrogen) is desirably 1 or less. As the oxide film, silicon oxide (SiO2), aluminum oxide (Al2O3), or the like can be used. By using silicon nitride or silicon oxynitride as the film of the antireflection film 120, the antireflection film 120 can be formed using the same film formation method and film formation apparatus as the near-infrared light reflection film 150, which will be described later. It is advantageous in terms of process.

An oxide film may be used instead of the nitride film for the antireflection film 120 . As materials for such an oxide film, in addition to silicon oxide, titanium oxide (TiO2), aluminum oxide (Al2O3), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), and the like can be used. can. When the antireflection film 120 is composed of a plurality of kinds of oxide films having different refractive indices, the oxide is appropriately selected from the above oxides.

The antireflection film 120 is formed by a known film formation method such as a vacuum deposition method, a sputtering method, an ion beam assisted deposition method (IAD method), an ion plating method (IP method), an ion beam sputtering method (IBS method), or the like. be able to. It is desirable to use a sputtering method or an ion beam sputtering method for forming the nitride film.

The near-infrared light absorption film 140 has a function of transmitting light in the visible region and absorbing a part of light in the red region to the near-infrared region. The near-infrared light absorption film 140 contains an organic dye and is composed of a resin film having a maximum absorption wavelength in the range of 650 nm to 750 nm (see broken line in FIG. 4). Since the near-infrared light absorption film 140 is adjacent to the crystallized glass 130, it is desirable to reduce the refractive index difference between the two to reduce the reflectance at the interface. By having such a near-infrared light absorbing film 140, it is possible to reduce the dependency of the spectral transmittance characteristics on the incident angle and to have excellent near-infrared light cutting properties.

As organic dyes, azo-based compounds, phthalocyanine-based compounds, cyanine-based compounds, diimmonium-based compounds, and the like can be used. Polyacryl, polyester, polycarbonate, polystyrene, polyolefin, or the like can be used as a resin material as a binder (binding agent for dye) that constitutes the near-infrared light absorbing film 140 . The resin material may be a mixture of a plurality of resins, or may be a copolymer using monomers of the above resins. Moreover, the resin material may be any material as long as it has a high transmittance for light in the visible region, and is selected in consideration of compatibility with the organic dye, film formation process, cost, and the like. In order to improve the ultraviolet resistance of the near-infrared light absorption film 140, a quencher (quenching dye) such as a sulfur compound may be added to the resin material.

For example, the following method can be used to form the near-infrared light absorbing film 140 . First, a resin binder is dissolved in a known solvent such as methyl ethyl ketone or toluene, and the above-described organic dye is added to prepare a coating liquid. Next, this coating liquid is applied to the crystallized glass 130 in a desired film thickness by, for example, spin coating, and dried and cured in a drying oven.

The near-infrared light reflecting film 150 is a dielectric multilayer film formed by alternately laminating a plurality of dielectrics having different refractive indices, like the antireflection film 120 . However, the dielectric multilayer film constituting the near-infrared light reflecting film 150 is formed by stacking a plurality of types of oxide films having different refractive indices, and the adjacent oxide films are different types of oxide films. . In the first embodiment, the near-infrared light reflecting film 150 is formed by alternately laminating two kinds of oxide films in several tens of layers. As the oxide film, titanium oxide (TiO2), aluminum oxide (Al2O3), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), etc. are used in addition to silicon oxide.

In the near-infrared light reflecting film 150, each oxide film has a thickness of λ/4, where λ is the wavelength of light to be reflected. By doing this, the light reflected from all the interfaces of the alternating layers will have the same phase when it reaches the incident surface, and the light will be constructive. Function. In this embodiment, the film should be designed so that λ reflects light in the near-infrared region. The near-infrared light reflecting film 150 is also formed using the same film forming method and film forming apparatus as those for the antireflection film 120 described above.

Human eyes are sensitive to so-called visible light with wavelengths of 380 nm to 780 nm. On the other hand, an imaging device generally has sensitivity to longer wavelength light, ie, light with a wavelength of about 1.1 μm, including visible light. Therefore, if the image captured by the imaging device is photographed as it is, the color does not look natural, which causes a sense of incongruity.

When the integrated cover glass 100 with an optical filter function having a near-infrared light reflecting portion and a near-infrared light absorbing portion is formed as a laminated structure as shown in FIG. Since the external light reflecting film 150 is provided, light with a wavelength of 700 nm or longer, which cannot be absorbed by the near-infrared light absorbing film 140, is cut, and an image with natural colors can be acquired. Also, if it is attempted to cut light in the near-infrared region only with the near-infrared light reflecting film 150, the reflectance will change greatly depending on the incident angle of the incident light, as will be described later. By combining the near-infrared light reflecting film 150 and the near-infrared light absorbing film 140 whose light absorption rate does not depend on the incident angle, the light transmittance can be reduced to a near-infrared light with little dependence on the light incident angle. It becomes possible to configure an infrared light cut filter.

In addition, since the cover glass 100 that protects the camera in the smartphone housing 20 from the outside world can cut the light in the ultraviolet region with the antireflection film 120, the optical lens group formed of synthetic resin that is a component of the camera (Lens unit 50) can be prevented from being degraded by ultraviolet rays, and the near-infrared light absorbing film 140 containing an organic dye can also be prevented from being degraded by ultraviolet rays. In addition, the anti-reflection function for light in the visible region captures more incident light, enabling acquisition of brighter images.

The anti-reflection film 120 is formed by alternately laminating nitride films and oxide films. Nitride films generally have a higher hardness than oxide films, reaching a hardness of 9H or more in a pencil hardness test. Therefore, by forming the antireflection film 120 including the nitride film, it is possible to improve the scratch resistance. In addition, the nitride film has a higher packing density and is denser than the oxide film. Since it does not contain oxygen as a component, it does not serve as a source of oxygen. Therefore, by providing the nitride film outside the near-infrared light absorption film 140, it is possible to prevent oxygen and moisture from entering the near-infrared light absorption film 140, thereby suppressing deterioration of the near-infrared light absorption film 140. .

Optical filters generally have a large number of optical interfaces. On the other hand, the lens has an advanced anti-reflection coating. It is difficult to achieve a transmittance comparable to that of a lens with an optical filter that cuts light in the near-infrared region, and reflected light may be returned to the lens side. This causes stray light that produces ghost images. In the conventional camera structure, since the optical filter 60 is placed in the immediate vicinity of the image sensor 70 on the optical path between the lens unit 50 and the image sensor 70, it was difficult to avoid the occurrence of the above ghost. However, according to the camera structure according to the present embodiment, there is no stray light as described above, so there is a remarkable effect of improving image quality.

Next, for reference, the spectral transmittance characteristics of the integrated cover glass 100 with an optical filter function having a near-infrared light reflecting portion and a near-infrared light absorbing portion will be described. Even if the functions of the cover glass 100 with an optical filter function are divided into, for example, a separate cover glass 215 with a near-infrared light reflecting function and an imaging device cover 244 with a near-infrared light absorbing function, the same effect can be obtained. is obtained.

FIG. 2(B) shows experimental results on how the spectral transmittance characteristics of a near-infrared light reflecting film formed of a dielectric film depend on the incident angle of light. The incident angle A is defined as shown in FIG. 2(C). "T" on the vertical axis indicates spectral transmittance, and the unit is % (percent). "λ" on the horizontal axis indicates the wavelength of light, and the unit is nm (nanometer) (the same applies to the following figures). The sample was made by alternately laminating 40 layers of titanium dioxide (TiO2) and silicon dioxide (SiO2) with a predetermined film thickness on glass. The solid line indicates the spectral transmittance when the incident angle of light is 0 degrees, and the dashed line indicates the spectral transmittance when the incident angle of light is 30 degrees. From FIG. 2B, it was confirmed that there is a significant difference in spectral transmittance between incident angles of 0 degrees and 30 degrees for light with a wavelength of around 700 nm, which is in the red region. If there is such a difference, the color tone of the image greatly changes between the image center and the peripheral portion, which ultimately causes the image quality to deteriorate.

FIG. 3 is an experiment on how the spectral transmittance of the cover glass 100 with an optical filter function having both a near-infrared light absorbing film and a near-infrared reflecting film depends on the incident angle of light. Show the results. A resin film containing an organic dye and having a thickness of 5 μm or less is used as the near-infrared light absorbing film, and the near-infrared light reflecting film has the same structure as in FIG. The solid line indicates the spectral transmittance when the incident angle of light is 0 degrees, the dashed line indicates the spectral transmittance when the incident angle of light is 15 degrees, and the one-dot chain line indicates the spectral transmittance when the incident angle of light is 30 degrees. It can be confirmed that the incident angle dependency is smaller than in the case of FIG.

FIG. 4 shows a cover glass 100 (solid line) with an optical filter function provided with a near-infrared light absorbing film 140 and a near-infrared light reflecting film 150, and a cover glass (broken line) formed with only the near-infrared light absorbing film 140. and a cover glass (one-dot chain line) on which only the near-infrared light reflecting film 150 is formed. The configurations of the near-infrared light absorbing film 140 and the near-infrared light reflecting film 150 are the same as those shown in FIGS. 2 and 3, so the description thereof is omitted. However, the incident angle of all light is 0 degree. When the near-infrared light absorption film 140 alone is used, light of 650 to 750 nm is strongly absorbed, but light of 800 nm or more is almost transmitted. As described above, the human eye is mainly sensitive to so-called visible light with a wavelength of 380 nm to 780 nm. results in an unnatural image. The near-infrared light reflecting film 150 is designed to cut off light with a wavelength of 700 nm or more, and a sharp decrease in spectral transmittance was actually measured near 700 nm. The cover glass 100 with an optical filter function is configured by combining the near-infrared light absorbing film 140 and the near-infrared light reflecting film 150. As shown by the solid line in FIG. Regarding 650 nm, it can be confirmed that high transmittance is realized and light with a wavelength of 700 nm or longer is cut.

According to the camera structure according to the embodiment of the present invention, there is a degree of freedom in the place where the near-infrared light reflecting section is arranged and the place where the near-infrared light absorbing section is arranged. It becomes possible to place it at any position, and a remarkable effect of improving the image quality is produced.

Light having a longer wavelength than light absorbed by the near-infrared light absorbing portion may be transmitted. Therefore, when the near-infrared light absorbing portion and the near-infrared light reflecting portion are arranged in order from the light incident side, the light with a longer wavelength than the light absorbed by the near-infrared light absorbing portion is absorbed by the camera. This makes it easier for the light to enter the module, and before it reaches the near-infrared light reflection section that can cut off the light on the long wavelength side, it reflects off the lens surface and becomes stray light, causing a drop in image quality.

According to the camera structure according to the embodiment of the present invention, the near-infrared light reflecting portion and the near-infrared light absorbing portion are arranged in order from the light incident side as the near-infrared light reflecting portion and the near-infrared light absorbing portion. Therefore, there is an effect that stray light on the long wavelength side can be suppressed.

According to the camera structure according to the embodiment of the present invention, the near-infrared light reflecting section includes the lens element that constitutes the optical lens group, and is arranged on the light incident side of the lens element. The distance from the near-infrared light reflecting section to the imaging device is greater than the position of the external light cut filter. When the incident angle of light deviates from the vertical to the axial direction, the near-infrared light reflecting portion may easily transmit light in the ultraviolet region. As the distance from the image pickup device increases, the angle at which the near-infrared light reflection section looks into the image pickup device becomes smaller. There is an effect that it can be reduced.

According to the camera structure according to the embodiment of the present invention, the transmittance of the near-infrared light absorption part does not depend on the incident angle of light in many cases. Therefore, the near-infrared light absorbing portion includes a lens element that constitutes an optical lens group in the camera structure, and is arranged closer to the image pickup device than the lens element, so that light tends to enter the image pickup device from various directions. A remarkable effect of being able to effectively suppress stray light is exhibited.

Image quality deteriorates when dust that does not easily transmit light adheres to the image sensor. According to the camera structure according to the embodiment of the present invention, the image pickup device cover that covers at least a part of the image pickup device as viewed from the light incident side is positioned between the optical lens group and the image pickup device, which is close to the image pickup device. Since it is arranged, there is a remarkable effect of reducing dust that may adhere to the image sensor and preventing deterioration of image quality.

According to the camera structure according to the embodiment of the present invention, it is possible to inexpensively manufacture an imaging device cover that is less deformed due to temperature changes.

The imaging device cover is arranged at a position close to the imaging device between the optical lens group and the imaging device. Therefore, when the image pickup device cover reflects light, it causes significant deterioration in the image quality of the image acquired by the image pickup device. According to the camera structure according to the embodiment of the present invention, the imaging device cover includes the anti-reflection layer that prevents reflection of light in at least the visible region, thereby achieving a remarkable effect of improving image quality.

According to the camera structure according to the embodiment of the present invention, it is possible to take in more incident light, and the reflected light caused by the image pickup element cover, particularly the reflected light from the image pickup element itself, is further reduced by the image pickup element cover. This prevents the light from being reflected back to the imaging element, thereby improving the image quality.

According to the camera structure according to the embodiment of the present invention, since the imaging element cover includes the near-infrared light absorbing portion, there are remarkable effects such as a reduction in the number of parts and a reduction in the number of steps in manufacturing the camera structure.

According to the camera structure according to the embodiment of the present invention, the near-infrared light absorbing portion has the near-infrared light absorbing film, and the near-infrared light absorbing film contains an organic dye that absorbs the near-infrared light. Therefore, without using blue glass, which is generally used as a filter material for absorbing light in the near-infrared region, the light in the near-infrared region can be suppressed with little dependency on the incident angle of light. It has the effect of making it possible.

According to the camera structure according to the embodiment of the present invention, since the cover glass has a near-infrared light reflecting film that reflects light, there is an effect that near-infrared light from the outside world does not enter the internal mechanism of the imaging device. sell. In addition, since there is no need to put a member with a near-infrared light reflecting film in the area close to the imaging device, reflection of light incident on the internal mechanism of the imaging device can be suppressed, resulting in suppression of stray light. , can be effective in reducing the causes of ghosts and flares.

FIG. 5 is a diagram showing spectral transmittance of a cover glass with an optical filter function included in the camera structure according to the second embodiment of the present invention. This embodiment provides a so-called dual-band optical filter cover glass and camera structure that can capture images even at night. The basic configuration of the camera structure is the same as in the first embodiment, but instead of the cover glass 215 with a near-infrared light reflecting function, a cover with an optical filter function is provided with a near-infrared light absorbing film 140 and a near-infrared light reflecting film 150. The glass 100 is arranged, and the imaging element cover 244 with near-infrared light absorbing function is omitted (not shown).

Further, the cover glass 215 with a near-infrared light reflecting function includes a near-infrared light reflecting film D that has a high light transmittance for part of light in the near-infrared region. Since the film structure of the near-infrared light reflecting film D is a well-known technique, the explanation thereof is omitted.

Combining the near-infrared light absorbing film 140 indicated by the dashed line in FIG. 5 and the near-infrared reflective film D with increased light transmittance for part of the light in the near-infrared region indicated by the dashed-dotted line in FIG. A dual-band cover glass that transmits light in the visible region and part of the light in the near-infrared region can be realized as indicated by the solid line in . However, in FIG. 5, for the spectral transmittance of the near-infrared light reflecting film D and the dual band cover glass, calculated values are shown at wavelengths of 750 nm or more. A camera structure having such a dual-band cover glass is suitable for an in-vehicle camera because it has a remarkable effect of making it easier to see lane boundaries and roadway lines on roads at night.

FIG. 6A is a cross-sectional view of a camera structure applied to a mobile communication device A, which is an imaging device according to the third embodiment of the present invention. This camera structure includes a cover glass 215 with a near-infrared light reflecting function that reflects near-infrared light, a plate 217 with a near-infrared light absorbing function that absorbs near-infrared light, and transparent glass as base materials for imaging. An element cover 240 is provided. Other configurations are the same as those of the above-described first embodiment, so the description is omitted.

FIG. 6B is a structural diagram of a cover glass with a near-infrared light reflecting function including a near-infrared light reflecting portion. The cover glass 215 with near-infrared light reflecting function uses crystallized glass 130 as a transparent substrate that transmits light, and has an antireflection film 120 that reflects light in the ultraviolet region and suppresses reflection of light in the visible region. is formed on the light incident side with the crystallized glass 130 as a reference. An antifouling coating film 110 for preventing contamination from the outside is provided on the outermost side of the light incident side. On the light exit side, in order from the farthest side with respect to the crystallized glass 130, an antireflection film 120 that prevents reflection of at least light in the visible region and a near-infrared light reflection film that reflects light in the near-infrared region. form 150;

In addition, in the cover glass 215 with a near-infrared light reflecting function, the antireflection film 120 closest to the imaging device 70 may be omitted.

FIG. 6C is a structural diagram of the plate 217 with near-infrared light absorption function. The plate 217 with near-infrared light absorption function includes a plurality of antireflection layers 230 that prevent reflection of light in at least the visible region, and further includes a near-infrared light absorption film 140 . The plate 217 with near-infrared light absorbing function has a transparent glass 220 as a base material, and a near-infrared light absorbing film 140 is provided adjacent to the transparent glass 220 . The antireflection layer 230 is formed on the light incident side with respect to the transparent glass 220, and the antireflection layer 230 and the near-infrared light absorption film are formed on the light exit side with respect to the transparent glass 220 in order from the farthest side. 140 are provided.

The plate 217 with near-infrared light absorbing function is arranged on the inner structure side, ie, the lens unit 50 side, from the cover glass 215 with near-infrared light reflecting function.

As a means for realizing the near-infrared light absorbing function plate 217, for example, a synthetic resin thin plate containing at least a part of an organic dye that absorbs light in the near-infrared region may be used as the base material. good. Also, a so-called blue glass plate that absorbs light in the near-infrared region may be used as in the conventional near-infrared light cut filter. It is also conceivable to attach a film that cuts near-infrared light to a transparent plate.

FIG. 6D is a structural diagram of an imaging element cover 240 using transparent glass as a base material, which includes a transparent glass 220 as a base material and a plurality of antireflection layers 230 . The imaging device cover 240 has antireflection layers 230 on both sides of the transparent glass 220 .

FIG. 6E shows a camera structure applied to a mobile communication device A, which is an imaging device according to the third embodiment, in which an imaging element cover 240 made of transparent glass as a base material is replaced with a transparent synthetic resin film 222 as a base material. It is a part of a modified embodiment in which the image sensor cover 242 is replaced with the image pickup element cover 242 as shown in FIG. That is, it is a structural diagram of an imaging element cover 242 having a transparent synthetic resin film 222 as a base material and a transparent synthetic resin film having a moth-eye structure that exerts an antireflection function on both sides as a base material. The thickness of the imaging element cover 242 whose base material is a transparent synthetic resin film is 0.2 mm or less. An imaging element cover 242 made of a transparent synthetic resin film as a base material has a moth-eye structure 232 on both sides for preventing reflection of light in at least the visible region.

The moth-eye structure does not reduce reflection using an interference effect like a dielectric multilayer film, but reduces reflection by eliminating a boundary surface where the refractive index changes abruptly. Specifically, a fine protrusion structure consisting of a large number of fine protrusions having a height of about several hundred nm is formed on the surface, and the repetition period of the protrusions is related to the wavelength range in which the effect of reducing reflection appears. The description of the moth-eye structure is omitted because it is a well-known technique, but in the case of this modified embodiment, for example, a transparent acrylic resin is used as the transparent synthetic resin film 222, and the moth-eye structure is formed by transfer or molding, thereby providing an antireflection function. Realize

That is, the so-called moth-eye structure 232 formed on the surface of the imaging device cover 242 made of a transparent synthetic resin film prevents light reflection over a wide band. The moth-eye structure 232 has an antireflection function at least for light in the visible region, and desirably also has an antireflection function for light in the ultraviolet region and light in the near-infrared region.

A synthetic resin film having a thickness of 100 μm or less can be easily produced. According to the camera structure according to the embodiment of the present invention, there is an effect that a thin and inexpensive imaging device cover can be manufactured at low cost.

According to the camera structure according to the embodiment of the present invention, it is possible to provide a camera module that is thinner than the conventional one.

An antireflection layer having a fine projection structure, a so-called moth-eye structure, formed on the surface of the image sensor cover prevents reflection of light over a wide band. Therefore, according to the camera structure according to the embodiment of the present invention, by forming the antireflection layer with the moth-eye structure, the reflected light caused by the image sensor cover can be significantly reduced over a wide band, and the image quality can be significantly improved. effect.

Furthermore, as another modified embodiment of the inner transparent plate 240, it is conceivable that a multilayer film obtained by applying a synthetic resin is formed as an antireflection layer on the surface of the transparent synthetic resin film 222 which is the base material. . In general, a multilayer film obtained by alternately laminating two types of thin films having different refractive indices for light can form an antireflection film for light. It is also known that such a multilayer film can be obtained by applying a synthetic resin.

For example, two kinds of synthetic resins having different refractive indices for light, which are both larger than the refractive index of air and smaller than the refractive index of the transparent synthetic resin film 222, are prepared. By alternately applying these to the transparent synthetic resin film 222, the inner transparent plate 240 having an antireflection film of stable quality can be manufactured at low cost. As a method of applying the synthetic resin to the transparent synthetic resin film 222, for example, a roller coating method can be considered. According to this modified embodiment, the inner transparent plate provided with the antireflection film can be produced in large quantities with stable quality at low cost.

FIG. 7A is a cross-sectional view of a camera structure applied to a mobile communication device A, which is an imaging device according to a fourth embodiment of the present invention. The camera structure includes a cover glass 215 with a near-infrared light reflecting function and a camera module 1 . The camera module 1 includes a lens unit 50 , a lens carrier 40 holding the lens unit 50 , an imaging device 70 , and an imaging device cover 240 . The structures of the cover glass 215 with a near-infrared light reflecting function and the imaging element cover 240 are the same as those described in the third embodiment, and therefore are omitted. Also, the method of manufacturing the near-infrared reflective film 150 and the antireflection film 120 is the same as that of the first embodiment, so the description thereof is omitted.

FIG. 7B is a cross-sectional view of a lens unit including lens elements having near-infrared light absorbing portions. A lens unit 50, ie, an optical lens group, is composed of a plurality of lens elements. A lens element arranged closest to the imaging element 70 in the optical lens group is the lens element 250 having a near-infrared light absorbing portion. The near-infrared light absorbing portion is an organic dye, and is uniformly contained in the synthetic resin forming the lens element 250 having the near-infrared light absorbing portion.

FIG. 7C is a cross-sectional view of a lens unit including a lens element having a near-infrared light absorbing portion. In this modified embodiment, the lens element having the near-infrared light absorbing portion is realized by providing the near-infrared light absorbing film 140 on the surface of the transparent lens element 255 closest to the imaging device 70 side. The method of manufacturing the near-infrared light absorbing film 140 is the same as that described in the first embodiment, and therefore will be omitted.

An antireflection layer 230 may be provided on the near-infrared light absorption film 140 on the imaging device 70 side.

According to the embodiment of the present invention, since the near-infrared light reflecting section that reflects light is provided, it is possible to prevent near-infrared light from the outside from entering the internal mechanism of the imaging device. In addition, since there is no need to put a member having a near-infrared light reflecting portion in the area close to the imaging device, reflection of light incident on the internal mechanism of the imaging device can be suppressed, resulting in suppression of stray light. , can be effective in reducing the causes of ghosts and flares.

According to an embodiment of the present invention, since the near-infrared light absorbing part contains an organic dye that absorbs near-infrared light, blue glass, which is generally used as a filter material for absorbing light in the near-infrared region, can be used. It is possible to suppress the light in the near-infrared region while the incident angle dependence of the light is small without using .

FIG. 8A is a cross-sectional view of a camera structure applied to an imaging device according to the fifth embodiment of the invention. The camera module 1 having the camera structure has a lens unit 50 , a lens carrier 40 holding the lens unit 50 , and an imaging device 70 , and is fixed to the vehicle body 22 . That is, the camera structure is a so-called vehicle-mounted camera structure.

FIG. 8B is a cross-sectional view of a lens unit including an optical lens element 270 including a near-infrared light reflecting portion and an optical lens element 250 including a near-infrared light absorbing portion. A near-infrared light reflecting film 150 is provided on the light incident side surface of the lens element 270 having the near-infrared light reflecting portion. In the lens element 250 having a near-infrared light absorbing portion, the near-infrared light absorbing portion is an organic dye, and is uniformly contained in the synthetic resin forming the lens element 250 having a near-infrared light absorbing portion. As a modified embodiment, the lens element 250 having the near-infrared light absorbing portion may be a transparent lens element 255 in which the near-infrared light absorbing film 140 is provided closest to the imaging device 70 (FIG. 7C). reference). In this embodiment, dust is less likely to be generated because mechanically moving members such as actuators are not included. Also, since the surface of the imaging device 70 is substantially perpendicular to the ground, dust is less likely to adhere to the imaging device 70 . Therefore, the imaging element cover 240 is omitted. The light incident side of the lens unit 50 may be provided with a cover glass for protection against contamination. Of course, the imaging element cover 240 may be provided close to the imaging element 70 .

With such a structure, the number of parts can be reduced, and the number of production steps can be significantly reduced, so that the device can be manufactured at low cost. Of course, since it has a near-infrared light reflecting portion and a near-infrared light absorbing portion, it also has the effect of improving image quality.

As a modified example, the lens element 270 having the near-infrared light reflecting portion in the camera structure is left as it is, and the image sensor cover has the near-infrared light absorbing function shown in FIG. 1(C) of the first embodiment. By using the image sensor cover 244, it is conceivable that the lens element does not have a light absorption function in the near-infrared region.

FIG. 9A is a cross-sectional view of a camera structure applied to an imaging device according to the sixth embodiment of the invention. The camera structure includes a cover glass 215 with a near-infrared light reflecting function and a camera module 1 . The camera module 1 includes a lens unit 50 , a lens carrier 40 holding the lens unit 50 , an imaging device 70 , and an imaging device cover 240 . The structures of the cover glass 215 with a near-infrared light reflecting function and the imaging element cover 240 are the same as those described in the third embodiment, and therefore are omitted.

FIG. 9B is a cross-sectional view of a lens unit provided with an optical element 500 with a near-infrared light absorbing function that includes a near-infrared light absorbing portion. The lens unit 50 has an optical element 500 with a near-infrared light absorption function on the light incident side. However, the optical element 500 with near-infrared light absorption function may be located anywhere on the axis as long as it is inside the lens unit 50 .

FIG. 9C is a structural diagram of an optical element 500 with a near-infrared light absorption function. The optical element 500 with near-infrared light absorption function includes a plurality of antireflection layers 230 that prevent reflection of light in at least the visible region, and further includes a near-infrared light absorption film 140 . The plate 217 with near-infrared light absorbing function has a transparent glass 220 as a base material, and a near-infrared light absorbing film 140 is provided adjacent to the transparent glass 220 . The antireflection layer 230 is formed on the light incident side with respect to the transparent glass 220, and the antireflection layer 230 and the near-infrared light absorption film are formed on the light exit side with respect to the transparent glass 220 in order from the farthest side. 140 are provided.

As a means for realizing the optical element 500 with a near-infrared light absorption function, for example, a synthetic resin thin plate containing at least a part of an organic dye that absorbs light in the near-infrared region is used as a base material. Also good. Also, a so-called blue glass plate that absorbs light in the near-infrared region may be used as in the conventional near-infrared light cut filter. It is also conceivable to attach a film that cuts near-infrared light to a transparent plate.

Note that the method of manufacturing the near-infrared reflective film 150, the antireflection film 120, and the near-infrared light absorbing film 140 is the same as in the first embodiment, so description thereof is omitted.

FIG. 10A is a cross-sectional view of a camera structure applied to an imaging device according to a seventh embodiment of the invention. The camera structure comprises a cover glass 550 and a camera module 1 . The camera module 1 includes a lens unit 50 , a lens carrier 40 holding the lens unit 50 , an imaging device 70 , and an imaging device cover 240 . The structure of the image pickup device cover 240 is the same as that described in the third embodiment, and is therefore omitted.

The cover glass 550 may use conventional tempered glass, sapphire glass, or the like as a base material. Of course, crystallized glass may also be used. The cover glass 550 has an anti-reflection film 120 (not shown) that reflects light in the ultraviolet region and suppresses reflection of light in the visible region on the surface on the image sensor 70 side.

FIG. 10B is a cross-sectional view of a lens unit including an optical element 530 with an optical filter function including a near-infrared light reflecting portion and a near-infrared light absorbing portion. The lens unit 50 has an optical element 530 with an optical filter function on the light incident side. However, the optical element 530 with an optical filter function may be located anywhere on the axis as long as it is inside the lens unit 50 .

FIG. 10C is a structural diagram of an optical element 530 with an optical filter function. The optical element 530 with an optical filter function includes a plurality of antireflection layers 230 that prevent reflection of light in at least the visible region, and further includes a near-infrared light absorption film 140 . The optical element 530 with an optical filter function has a transparent glass 220 as a base material, and a near-infrared light absorbing film 140 is provided adjacent to the transparent glass 220 . The antireflection layer 230 is formed on the light incident side with respect to the transparent glass 220, and the antireflection layer 230 and the near-infrared light reflecting film are formed on the light exit side with respect to the transparent glass 220 in order from the farthest side. 150 and a near-infrared light absorbing film 140 are provided.

As means for realizing the optical element 530 with an optical filter function, for example, a synthetic resin thin plate containing at least a part of an organic dye that absorbs light in the near-infrared region may be used as a base material. Also, a so-called blue glass plate that absorbs light in the near-infrared region may be used as in the conventional near-infrared light cut filter. It is also conceivable to attach a film that cuts near-infrared light to a transparent plate.
The method of manufacturing the near-infrared light absorbing film 140, the near-infrared reflecting film 150, and the anti-reflection film 120 is the same as in the first embodiment, and therefore description thereof is omitted.

According to the camera structure, it is only necessary to add the optical element 530 with an optical filter function to the lens unit 50, and conventional members can be used for other configurations. In addition, since the optical lens group includes an integral optical element including both a near-infrared light reflecting portion and a near-infrared light absorbing portion, it is necessary to insert a member having a near-infrared light reflecting film in the immediate vicinity of the imaging device. is gone. Therefore, it is possible to suppress the reflection of light incident on the internal mechanism of the imaging device, and as a result, it is possible to suppress the stray light and reduce the causes of ghost and flare.

As a result of further intensive research by the inventor, it has been found that the conventional camera structure has another problem that a color difference occurs between the central portion and the peripheral portion of the captured image. This problem is particularly noticeable when the incident angle of incident light can be large in a mode in which the cover glass is provided with the near-infrared reflective portion.

FIG. 12A shows the spectral characteristics of the light transmittance in the near-infrared light absorbing portion using the conventional light-absorbing ink, and the incident light angle dependence of the spectral characteristics of the light transmittance in the near-infrared light reflecting portion. It is a graph showing. The vertical axis indicates the light transmittance T (in units of %), and the horizontal axis indicates the wavelength of incident light (in units of nm). Specifically, an imaging element cover 244 with a near-infrared light absorbing function (see FIG. 1C) having a near-infrared light absorbing film 140 as a near-infrared light absorbing portion and a near-infrared light absorbing film 140 as a near-infrared light reflecting portion. Consider an optical system that includes a cover glass 215 with a near-infrared light reflecting function that has an infrared light reflecting film 150 (see FIG. 1B).

In FIG. 12A, the solid line A1 indicates the spectral characteristics of the light transmittance of the imaging element cover 244 with near-infrared light absorption function alone. A dotted line R1 indicates the spectral characteristics of the light transmittance of the near-infrared light reflecting cover glass 215 alone when the incident angle of incident light is 0°, and a broken line R2 indicates when the incident angle of incident light is 30°. 2 shows the spectral characteristics of the light transmittance of the single cover glass 215 with a near-infrared light reflecting function. A curve A1 representing the spectral characteristics of the conventional near-infrared light absorbing ink and a dashed line R2 representing the spectral characteristics of the conventional near-infrared reflecting portion at an incident angle of 30° are in the light wavelength range of 660 to 700 nm. The solid line A1, which almost overlaps and indicates the spectral characteristics of the conventional near-infrared light absorbing ink, and the dotted line R1, which indicates the spectral characteristics of the conventional near-infrared reflecting portion at an incident angle of 0°, extend to the intersection point near 720 nm. No overlap.

FIG. 12B is a graph showing the incident light angle dependence of the spectral characteristics of the light transmittance when the near-infrared light absorbing portion and the near-infrared light reflecting portion are combined. Specifically, the dotted line C1 is the spectral characteristic when the incident angle is 0°, and the dashed line C2 is the spectral characteristic when the incident angle is 30°. In other words, the dotted line C1 represents the spectral characteristics of the optical system combining the solid line A1 and the dotted line R1 in FIG. be. A gap G1 is generated between the dotted line C1 and the dashed line C2 in the range of 660 nm to 690 nm.

Here, the wavelength at which the light transmittance decreases to 10% when the wavelength of incident light is increased is defined as the near-infrared cutoff wavelength. Considering a near-infrared light cut filter having a near-infrared light reflecting portion and a near-infrared absorbing portion, the angle of the near-infrared cutoff wavelength when the incident angle of incident light is changed in the range of 0° to 30° The width of the dependent change may become about 30 nm. Conversely, at a predetermined light wavelength in the near-infrared light region, the light transmittance of the near-infrared light cut filter varies greatly depending on the incident angle of the incident light. Specifically, for example, if light with a wavelength of 660 to 690 nm is incident, the light transmittance is about 20% when the incident angle is small at the center of the acquired image, and the incident angle is When is large, a phenomenon occurs in which the light transmittance becomes almost 0%, and as a result, the light wavelength dependence of the transmittance differs between the peripheral part and the central part of the acquired image, resulting in a so-called "red spot" in the image quality. An aggravation phenomenon occurs.

As a camera structure according to the eighth embodiment of the present invention, a combination of a near-infrared light absorbing portion using a new light-absorbing ink whose spectral characteristics are shown in FIG. 13(A) and a new near-infrared light reflecting portion Consider a camera structure comprising: The configuration of the near-infrared light absorbing portion is the same as that of the imaging element cover 244 with near-infrared light absorbing function shown in FIG. 1(C), and the configuration of the near-infrared light reflecting portion is shown in FIG. 1(B). It is the same as the cover glass 215 with a near-infrared light reflecting function. Specifically, an imaging element cover 244 with a near-infrared light absorbing function (see FIG. 1C) having a near-infrared light absorbing film 140 as a near-infrared light absorbing portion and a near-infrared light absorbing film 140 as a near-infrared light reflecting portion. It is an optical system including a cover glass 215 with a near-infrared light reflecting function having an infrared light reflecting film 150 (see FIG. 1B).

FIG. 13A shows the spectral characteristics of the light transmittance in the near-infrared light absorbing portion using the new light-absorbing ink, and the incident light angle dependence of the spectral characteristics of the light transmittance in the new near-infrared light reflecting portion. It is a graph showing the nature. The vertical axis indicates the light transmittance T (in units of %), and the horizontal axis indicates the wavelength of incident light (in units of nm). Specifically, an imaging element cover 244 with a near-infrared light absorbing function (see FIG. 1C) having a near-infrared light absorbing film 140 as a near-infrared light absorbing portion and a near-infrared light absorbing film 140 as a near-infrared light reflecting portion. Consider an optical system that includes a cover glass 215 with a near-infrared light reflecting function that has an infrared light reflecting film 150 (see FIG. 1B).

In FIG. 13A, the solid line A2 indicates the spectral characteristics of the light transmittance of the imaging device cover 244 with near-infrared light absorption function alone. A dotted line R3 indicates the spectral characteristics of the light transmittance of the near-infrared light reflecting cover glass 215 alone when the incident angle of incident light is 0°, and a broken line R4 indicates when the incident angle of incident light is 30°. 2 shows the spectral characteristics of the light transmittance of the single cover glass 215 with a near-infrared light reflecting function.

Specifically, the camera structure according to the eighth embodiment of the present invention includes a near-infrared light absorbing portion 140 that absorbs light in the near-infrared region, and a near-infrared light absorbing portion 140 that reflects light in the near-infrared region. The near-infrared light absorbing portion 140 has a light absorption wavelength region 700 with a light transmittance of less than 2% in a light wavelength region of 685 nm to 755 nm. When the wavelength at which the light transmittance decreases to 50% as the wavelength of light incident on the light reflecting portion 150 increases is defined as the near-infrared light cutoff wavelength, the near-infrared light reflecting portion 150 has the characteristic of substantially totally reflecting light with a wavelength longer than the near-infrared light cutoff wavelength, and the incident angle of the incident light to the near-infrared light reflecting part 150 is changed in the range of 0° to 30° Sometimes, the near-infrared light cutoff wavelength is always characterized as falling within the light absorption wavelength region 700 .

In other words, the near-infrared light cutoff wavelength CF1 of the near-infrared light reflecting portion 150 when the incident angle of incident light is 0° and the near-infrared light cutoff wavelength CF1 of the near-infrared light reflecting portion 150 when the incident angle of incident light is 30° Optical cutoff wavelength CF2 is included in optical absorption wavelength region 700 .

In the near-infrared light reflecting section 150, the spectral characteristic for light with a wavelength longer than the near-infrared light cutoff wavelength is desirably a light transmittance of less than 1% at about 750 nm to 1000 nm.
In the wavelength range longer than about 1000 nm, there may be some light transmission, eg a few percent.

FIG. 13B is a graph showing the incident light angle dependence of the spectral characteristics of the light transmittance when the near-infrared light absorbing section 140 and the near-infrared light reflecting section 150 are combined. Specifically, the dotted line C3 is the spectral characteristic when the incident angle is 0°, and the dashed line C4 is the spectral characteristic when the incident angle is 30°. In other words, the spectral characteristics of the optical system combining the solid line A2 and the dotted line R3 in FIG. 13A are indicated by the dotted line C3, and the spectral characteristics of the optical system combining the solid line A2 and the broken line R4 in FIG. be.

Here, the wavelength at which the light transmittance decreases to 10% when the wavelength of incident light is increased is defined as the near-infrared cutoff wavelength.

Considering a near-infrared light cut filter having a near-infrared light reflecting portion 150 and a near-infrared absorbing portion 140, the near-infrared light cutoff wavelength when the incident angle of incident light is changed in the range of 0° to 30° is 5 nm or less. That is, the light transmittance of the near-infrared cut filter is less likely to depend on the incident angle of incident light.

When the near-infrared light cut filter has the near-infrared light reflection section 150 including, for example, a dielectric multilayer film, the frequency dependence of the light transmittance in the near-infrared light reflection section 150 depends on the incident angle of the incident light. Change. That is, for example, the near-infrared light cutoff wavelength of the near-infrared light reflecting portion 150 is approximately 700 nm when the incident angle of the incident light is 0°, but becomes approximately 675 nm when the incident angle of the incident light is 30°. Such incident angle dependence may occur. Then, assuming that the near-infrared light cut filter has the near-infrared light absorbing portion 140, the light transmittance realized by combining with the near-infrared light reflecting portion 150 may change greatly depending on the incident angle of the incident light. could be. Specifically, the near-infrared light cut filter having the near-infrared light reflecting portion 150 and the near-infrared absorbing portion 140 cuts the near-infrared light when the incident angle of the incident light is changed in the range of 0° to 30°. The angle-dependent change width of the light cutoff wavelength may be about 30 nm. Conversely, at a predetermined light wavelength in the near-infrared light region, the light transmittance of the near-infrared light cut filter largely fluctuates depending on the incident angle of the incident light. For example, if light with a wavelength of 660 to 690 nm is incident, the light transmittance is about 20% when the incident angle is small at the center of the acquired image, and the light transmittance is about 20% when the incident angle is large at the periphery of the acquired image. As a result, the optical wavelength dependence of the transmittance differs between the periphery and the center of the obtained image, resulting in a so-called "red spot", which deteriorates the image quality.

According to the camera structure according to the eighth embodiment of the present invention, in the near-infrared light cut filter, the angular dependence of the near-infrared cutoff wavelength when the incident angle of the incident light is changed in the range of 0° to 30° Since the width of change is 5 nm or less, it is difficult for differences in color expression to occur in the acquired image, and an excellent effect of improving the image quality is exhibited.

As a combined effect of the near-infrared light absorbing portion 140 and the near-infrared light reflecting portion 150, when the transmittance of light at a predetermined wavelength is 1% or more, an acquired image is affected. Therefore, as the spectral characteristics of the near-infrared light absorbing portion 140, when the light transmittance of the near-infrared light reflecting portion 150 reaches 50% in a light wavelength region in which the light transmittance is 2% or more, the image quality of the obtained image becomes visible to the naked eye. The color will be different than what you see. When the near-infrared light reflecting section 150 is formed of, for example, a dielectric multilayer film, the light transmittance varies depending on the incident angle of the incident light. This results in a phenomenon of deterioration in image quality called "red dropout".

According to the camera structure according to the eighth embodiment of the present invention, the combined effect of the near-infrared light absorbing portion 140 and the near-infrared light reflecting portion 150 is a light transmittance of 1% in the light wavelength range of 685 nm to 755 nm. Since it is less than 100 mm, there is also the excellent effect of reducing the difference between the image quality of the obtained image and that seen by the naked eye. Further, when the incident angle of the incident light to the near-infrared light reflecting portion 150 is changed in the range of 0° to 30°, the near-infrared light cutoff wavelength of the near-infrared light reflecting portion 150 is always the light transmittance is less than 2% in the light absorption wavelength region 700, the incident angle dependence of the spectral characteristics of light in the near-infrared region is reduced, and the light wavelength that can be obtained in the peripheral and central portions of the obtained image does not change. Therefore, an excellent effect of improving image quality is exhibited.

FIG. 14A is a cross-sectional view of a camera structure applied to a mobile communication device A, which is an imaging device according to the ninth embodiment of the present invention. In the case of this embodiment, the solid-state imaging device is an information communication device, a mobile communication device A. FIG. The camera structure has a cover glass 400 with an optical filter function and a camera module 501 housed in a housing 520 of a mobile communication device A such as a smart phone from the light incident side. The camera module 501 includes a lens unit 450 which is an optical lens group arranged on the side of the cover glass 400 with an optical filter function, and an imaging element 570 which receives light incident through the cover glass 400 with an optical filter function and the lens unit 450. , and is characterized in that no near-infrared light cut filter for cutting light in the near-infrared region is arranged between the optical path from the lens unit 450 to the image sensor 570 . Specifically, as shown in FIG. 14A, a cover glass 400 with an optical filter function, a lens unit 450, a lens carrier 540, and a magnet holder 430 are provided. It mainly consists of an imaging device 570 and a substrate 580 and is fixed to the smartphone housing 520 . The imaging element 570 and the substrate 580 may be connected by wire bonding or by flip-chip mounting.

The major difference from the conventional camera structure shown in FIG. 11(A) is that the optical filter 60 (see FIG. 11(A)) for cutting near-infrared light, which was conventionally necessary for improving image quality, is omitted. . Instead, the cover glass 10, which has conventionally mainly played the role of protecting the camera module 1, is added with a filter function for cutting light in the near-infrared region. By adopting such a structure, the overall length of the camera structure can be made shorter than before, and since the optical filter 60 is not arranged near the imaging device 70, the filter can be removed during the manufacturing process of the optical filter 60. It is possible to prevent the granular dust (particles) adhering to the surface of the imaging device 70 from falling on the surface of the imaging device 70 and deteriorating the image. In addition, in the assembly process of the camera module 1, there is no need for a process for arranging and assembling the near-infrared light cut filter 60, which contributes to further cost reduction, yield improvement, and work efficiency.

Moreover, by providing the camera structure shown in FIG. 14A, the portable communication device A can be made smaller, thinner, and manufactured at a lower cost.

FIG. 14(B) shows a laminated structure of a cover glass 400 with an optical filter function that is continuously installed on the housing of the mobile communication device A and protects the camera module, which is an internal mechanism, from the outside world. The cover glass 400 with an optical filter function uses a crystallized glass 630 as a transparent substrate that transmits light, and an antireflection film 620 that reflects light in the ultraviolet region and suppresses reflection of light in the visible region is a crystal. It is formed on the light incident side with reference to the tempered glass 630 . An antifouling coating film 610 for preventing contamination from the outside is provided on the outermost side of the light incident side. On the light exit side, a near-infrared light reflecting film 650 as a near-infrared reflecting portion that reflects light in the near-infrared region and light in the near-infrared region are arranged in order from the farthest side with respect to the crystallized glass 630 . A near-infrared light absorbing film 640 is formed as a near-infrared light absorbing portion that absorbs . An antireflection film 620 may be further formed on the farthest side of the light exit side.

In general, crystallized glass has large crystal grains, making it difficult for light to pass through. However, recent advances in technology have made it possible to control crystal grains to nanometer sizes, such as the shock-resistant, high-hardness clear glass-ceramics manufactured by Ohara Co., Ltd., increasing light transmittance. By using such crystallized glass, a cover glass having both impact resistance and crack-resistant fracture toughness can be produced. Then, the cover glass 400 with an optical filter function is realized by forming the above laminated structure on such a cover glass. It is theoretically conceivable to use blue glass as the cover glass 400 with the optical filter function, but it is not suitable because of its low impact resistance and lack of crack-resistant fracture toughness. It is also conceivable to form a near-infrared light absorbing film 640 and a near-infrared light reflecting film 650, which will be described later, on tempered glass to form the cover glass 400 with an optical filter function. It has the disadvantage of low impact resistance. It is also conceivable to form the near-infrared light absorbing film 640 and the near-infrared light reflecting film 650 on sapphire glass having high hardness to form the cover glass 400 with an optical filter function. The workability is lower than when the tempered glass 630 is used.

The antifouling coating film 610 prevents fingerprint smudges and sebum smudges and facilitates wiping off the smudges. The antifouling coating film 610 is formed of a fluorine-based coating agent or the like, and is formed on the outermost side of the laminated structure of the cover glass on the light incident side by coating or spraying.

The antireflection film 620 reflects light in the ultraviolet region and suppresses reflection of light in the visible region. The antireflection film 620 is a dielectric multilayer film, and is configured by alternately laminating a nitride film and an oxide film. A dielectric film forming the antireflection film 620 is formed by alternately stacking a plurality of nitride films and oxide films. Silicon nitride, silicon oxynitride, aluminum nitride, or the like can be used as the nitride film. When silicon oxynitride is used, the stoichiometric ratio of oxygen and nitrogen (oxygen/nitrogen) is desirably 1 or less. Silicon oxide (SiO2), aluminum oxide (Al2O3), or the like can be used as the oxide film. By using silicon nitride or silicon oxynitride as the film of the antireflection film 620, the antireflection film 620 can be formed using the same film formation method and film formation apparatus as for the near-infrared light reflection film 150, which will be described later. It is advantageous in terms of process.

An oxide film may be used instead of the nitride film for the antireflection film 620 . As materials for such an oxide film, in addition to silicon oxide, titanium oxide (TiO2), aluminum oxide (Al2O3), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), and the like can be used. can. When the antireflection film 120 is composed of a plurality of kinds of oxide films having different refractive indices, the oxide is appropriately selected from the above oxides.

The antireflection film 620 is formed by a known film formation method such as a vacuum deposition method, a sputtering method, an ion beam assisted deposition method (IAD method), an ion plating method (IP method), an ion beam sputtering method (IBS method), or the like. be able to. It is desirable to use a sputtering method or an ion beam sputtering method for forming the nitride film.

The near-infrared light absorption film 640 is formed on the surface of the crystallized glass 630 opposite to the antireflection film 620 described above, that is, on the imaging element 570 side of the cover glass 400 with optical filter function (see FIG. 14A). be done. The near-infrared light absorption film 640 has a function of transmitting light in the visible region and absorbing a part of light in the red region to the near-infrared region. The near-infrared light absorption film 640 contains an organic dye and is composed of a resin film having a maximum absorption wavelength in the range of 700 nm to 750 nm (see solid line A2 in FIG. 13A). Since the near-infrared light absorbing film 640 is adjacent to the crystallized glass 630, it is desirable to reduce the refractive index difference between the two to reduce the reflectance at the interface. By having such a near-infrared light absorbing film 640, it is possible to reduce the dependency of the spectral transmittance characteristics on the incident angle and to have excellent near-infrared light cutting properties.

As organic dyes, azo-based compounds, phthalocyanine-based compounds, cyanine-based compounds, diimmonium-based compounds, and the like can be used. Polyacryl, polyester, polycarbonate, polystyrene, polyolefin, or the like can be used as a resin material as a binder (binding agent for dye) that constitutes the near-infrared light absorbing film 640 . The resin material may be a mixture of a plurality of resins, or may be a copolymer using monomers of the above resins. Moreover, the resin material may be any material as long as it has a high transmittance for light in the visible region, and is selected in consideration of compatibility with the organic dye, film formation process, cost, and the like. In order to improve the ultraviolet resistance of the near-infrared light absorption film 640, a quencher (quenching dye) such as a sulfur compound may be added to the resin material.

For example, the following method can be used to form the near-infrared light absorption film 640 . First, a resin binder is dissolved in a known solvent such as methyl ethyl ketone or toluene, and the above-described organic dye is added to prepare a coating liquid. Next, this coating liquid is applied to the crystallized glass 630 to a desired film thickness by, for example, spin coating, and dried and cured in a drying oven.

The near-infrared light reflecting film 650 is a dielectric multilayer film formed by alternately laminating a plurality of dielectrics having different refractive indices, similar to the antireflection film 620 . However, the dielectric multilayer film that constitutes the near-infrared light reflecting film 650 is formed by stacking multiple types of oxide films having different refractive indices, and the adjacent oxide films are different types of oxide films. . In the first embodiment, the near-infrared light reflecting film 650 is formed by alternately laminating two kinds of oxide films in several dozen layers. As the oxide film, titanium oxide (TiO2), aluminum oxide (Al2O3), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), etc. are used in addition to silicon oxide.

In the near-infrared light reflecting film 650, each oxide film has a thickness of λ/4, where λ is the wavelength of light to be reflected. By doing this, the light reflected from all the interfaces of the alternating layers will have the same phase when it reaches the incident surface, and the light will be constructive. Function. In this embodiment, the film should be designed so that λ reflects light in the near-infrared region. The near-infrared light reflecting film 650 is also formed using the same film forming method and film forming apparatus as those for the antireflection film 620 described above.

Human eyes are sensitive to so-called visible light with wavelengths of 380 nm to 780 nm. On the other hand, an imaging device generally has sensitivity to longer wavelength light, ie, light with a wavelength of about 1.1 μm, including visible light. Therefore, if the image captured by the imaging device is photographed as it is, the color does not look natural, which causes a sense of incongruity.

If the cover glass 400 with an optical filter function has a laminated structure as shown in FIG. It is possible to cut light with a wavelength of 700 nm or more and acquire an image with natural colors.

The light wavelength dependence of the light transmittance of the near-infrared light reflecting film 650 is shown in FIG. 13(A). Specifically, the dotted line R3 indicates the spectral characteristics of the light transmittance of the near-infrared light reflecting film 650 alone when the incident angle of incident light is 0°, and the dashed line R4 indicates the spectral characteristics of the light transmittance when the incident angle of incident light is 30°. 6 shows the spectral characteristics of the light transmittance of the single near-infrared light reflecting film 650 when .

In this embodiment, when the wavelength at which the light transmittance decreases to 50% as the wavelength of light incident on the near-infrared light reflecting film 650 increases is defined as the near-infrared light cutoff wavelength. ,
Even if the incident angle of the incident light to the near-infrared light reflecting portion 650 is changed in the range of 0° to 30°, the near-infrared light cutoff wavelength of the near-infrared light reflecting portion 650 always has light transmittance. Since it falls within the light absorption wavelength region 700, which is less than 2%, the incident angle dependence of the spectral characteristics of the light in the near infrared region becomes small, and the light wavelength that can be acquired in the peripheral part and the central part of the acquired image does not change. An excellent effect of improving image quality is exhibited.

That is, by combining the near-infrared light reflecting film 650 and the near-infrared light absorbing film 640 whose light absorption rate does not depend on the incident angle, the light transmittance is less dependent on the light incident angle. A near-infrared light cut filter can be configured (see FIG. 13B).

In addition, since the cover glass 400 that protects the camera in the smartphone housing 520 from the outside world can cut the light in the ultraviolet region with the antireflection film 620, the optical lens group formed of synthetic resin that is a component of the camera (Lens unit 450) can be prevented from being degraded by ultraviolet rays, and the near-infrared light absorption film 640 containing an organic dye can also be prevented from being degraded by ultraviolet rays. In addition, the anti-reflection function for light in the visible region captures more incident light, enabling acquisition of brighter images.

The anti-reflection film 620 is formed by alternately laminating nitride films and oxide films. Nitride films generally have a higher hardness than oxide films, reaching a hardness of 9H or more in a pencil hardness test. Therefore, by forming the antireflection film 120 including the nitride film, it is possible to improve the scratch resistance. In addition, the nitride film has a higher packing density and is denser than the oxide film. Since it does not contain oxygen as a component, it does not serve as a source of oxygen. Therefore, by providing the nitride film outside the near-infrared light absorption film 640, it is possible to prevent oxygen and moisture from entering the near-infrared light absorption film 640, thereby suppressing deterioration of the near-infrared light absorption film 640. .

Optical filters generally have a large number of optical interfaces. On the other hand, the lens has an advanced anti-reflection coating. It is difficult to achieve a transmittance comparable to that of a lens with an optical filter that cuts light in the near-infrared region, and reflected light may be returned to the lens side. This causes stray light that produces ghost images. In the conventional camera structure, since the optical filter 60 is placed in the immediate vicinity of the image pickup device 70 on the optical path between the lens unit 50 and the image pickup device 70, it was difficult to avoid the above-described ghost ( See FIG. 11(A)). However, according to the camera structure according to the present embodiment, there is no stray light as described above, so there is a remarkable effect of improving image quality.

According to the ninth embodiment of the present invention, it is possible to inexpensively realize an imaging apparatus having a camera structure with improved image quality compared to the conventional one.

It should be noted that the camera structure and imaging device according to the embodiments of the present invention are not limited to the above-described embodiments, and of course various modifications can be made without departing from the gist of the present invention.

1 camera module
REFERENCE SIGNS LIST 10 cover glass 20 smart phone housing 22 vehicle body 30 magnet holder 40 lens carrier 50 lens unit 60 optical filter 70 imaging element 80 substrate 100 cover glass with optical filter function 110 antifouling coating film 120 antireflection film 130 crystallized glass 140 near infrared Light absorbing film 150 Near-infrared light reflecting film 160 Incidence surface 170 Output surface 180 Measurement target 190 Incident light 200 Vertical axis 210 Cover glass with optical filter function 215 Cover glass with near-infrared light reflection function 217 With near-infrared light absorption function Plate 220 Transparent glass 222 Transparent synthetic resin film 230 Antireflection layer 232 Moth-eye structure 240 Image sensor cover 242 Image sensor cover using transparent synthetic resin film as base material 244 Image sensor cover with near-infrared light absorption function 250 Near-infrared light absorption Lens Element 255 Transparent Lens Element 270 Lens Element 270 Lens Element 300 Light Source 310 High Reflective Material 320 Low Reflective Material 360 Transparent Glass 370 Antireflection Film 380 Blue Glass 390 Near Infrared Light Reflective Film 400 Optics Cover glass with filter function 430 Magnet holder 450 Lens unit 500 Optical element with near-infrared light absorption function 501 Camera module 520 Smart phone housing 530 Optical element with optical filter function 540 Lens carrier 550 Cover glass 570 Image sensor 580 Substrate 610 Antifouling coat Film 620 Antireflection film 630 Crystallized glass 640 Near-infrared light absorbing film (near-infrared light absorbing portion)
650 near-infrared light reflecting film (near-infrared light reflecting part)
700 Light absorption wavelength range A Portable communication equipment A1 Spectral characteristics of conventional near-infrared absorbing ink A2 Spectral characteristics of new near-infrared absorbing ink C1 Spectral characteristics at an incident angle of 0° C2 At an incident angle of 30° Spectral characteristics C3 Spectral characteristics at an incident angle of 0° C4 Spectral characteristics at an incident angle of 30° G Ghost R1 Spectral characteristics of a conventional near-infrared reflector at an incident angle of 0° R2 At an incident angle of 30° Spectral characteristics of the conventional near-infrared reflective part R3 Spectral characteristics of the new near-infrared reflective part when the incident angle is 0° R4 Spectral characteristics of the new near-infrared reflective part when the incident angle is 30°

Claims (1)

a near-infrared light absorbing portion that absorbs light in the near-infrared region;
a near-infrared light reflecting portion that reflects light in the near-infrared region;
with
The near-infrared light absorbing portion has a light transmittance of less than 2% at 700 nm in a light wavelength region defined as a light wavelength of 685 nm to 755 nm,
The wavelength at which the light transmittance decreases to 50% as the wavelength of light incident on the near-infrared light reflecting portion increases is defined as the near-infrared light cutoff wavelength of the near-infrared light reflecting portion. When defined, the near-infrared light reflecting portion has a characteristic of substantially totally reflecting light having a wavelength longer than the near-infrared light cutoff wavelength,
When the incident angle of the light incident on the near-infrared light reflecting portion is changed in the range of 0° to 30°, the near-infrared light cutoff wavelength of the near-infrared light reflecting portion is always the light is included in the wavelength range ,
When defining a configuration including the near-infrared light absorbing portion and the near-infrared light reflecting portion as a near-infrared light cut filter, the transmittance of all light in the light wavelength region in the near-infrared light cut filter is less than 1% .

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