JP7106824B2 - Light irradiation device - Google Patents

Description

The present invention relates to a light irradiation device having a diffractive optical element.

In recent years, the applications of sensor systems have expanded. There are various kinds of sensors, and the information to be detected is also various. One of such means is to irradiate an object with light from a light source and obtain information from the reflected light. For example, pattern authentication sensors, infrared radars, etc. are examples.

The light sources of these sensors have a wavelength distribution, brightness, spread, etc., depending on the application. As for the wavelength of light, a range from visible light to infrared light is often used. In particular, infrared rays are widely used because they are not easily affected by external light, are invisible, and can be used to observe the inside of an object. As for the types of light sources, LED light sources, laser light sources, and the like are often used. For example, when detecting a distant place, a laser light source with little spread of light is preferably used, and when detecting a relatively close place, when irradiating an area with a certain extent of spread, an LED light source is suitable. used for

By the way, the size, shape, etc. of the target irradiation area do not necessarily match the spread (profile) of the light from the light source, and it is necessary to shape the light with a diffusion plate, lens, shielding plate, etc. be. A diffractive optical element (DOE) can be used as a means for shaping light. This applies the diffraction phenomenon when light passes through a place where materials with different refractive indices are arranged periodically. DOEs are designed primarily for light of a single wavelength, but theoretically they can shape light into almost any shape. Moreover, the DOE can control the uniformity of the light distribution within the irradiation area. Such characteristics of the DOE are advantageous in terms of high efficiency by suppressing irradiation to unnecessary areas, miniaturization of the apparatus by reducing the number of light sources, and the like.
DOEs can be used with both parallel light sources such as lasers and diffuse light sources such as LEDs, and can be applied to a wide range of wavelengths from ultraviolet light to visible light and infrared light.

For example, Patent Literature 1 discloses an optical element in which a plurality of substrates having an uneven structure formed on their surfaces are combined.

By the way, if the light irradiation device is configured as one part by combining the light emitting element and the DOE, and this is mounted on the substrate according to the application, it is easy to handle. In that case, the light irradiation device is one part together with other various parts, and after being placed on the board with solder paste (cream solder) sandwiched therebetween, the solder paste is melted in a high temperature environment and soldered. is assumed.

Here, assuming mass production of the DOE, it is desirable that the concave-convex shape is made of resin. There is a risk that the uneven shape will be deformed.

JP 2006-84635 A

An object of the present invention is to provide a light irradiation device with high heat resistance.

The present invention solves the above problems by means of the following solutions. In order to facilitate understanding, reference numerals corresponding to the embodiments of the present invention are used for description, but the present invention is not limited to these.

A first invention comprises a diffractive optical element (10, 50) that diffracts and emits incident light, and a light source section (30) that projects light onto the diffractive optical element (10, 50). In the light irradiation device (1), the diffractive optical element (10, 50) is arranged between a high refractive index portion (111) in which convex portions (111a) are arranged side by side and the convex portions (111a). at least one diffractive layer (115) having a low refractive index portion (114) comprising recesses (112) formed therein; and a glass layer (41) arranged on the side from which light from the light source part (30) is emitted.

A second invention is the light irradiation device (1) according to the first invention, characterized by comprising a reflection suppressing layer (42) laminated on the glass layer (41). ).

A third invention is the light irradiation device (1) according to the first invention or the second invention, wherein the glass layer (41) also serves as a base material of the diffraction layer (115). A light irradiation device (1) is characterized.

A fourth invention is based on the light irradiation device (1) according to the third invention, wherein all the diffraction layers (115) use the glass layer (41) as a base material, and the glass layer (41 ) is laminated with an antireflection layer (42) on the side opposite to the diffraction layer (115).

A fifth invention is the light irradiation device (1) according to any one of the first invention to the fourth invention, wherein the diffraction layer (115) is arranged on both surfaces of the substrate (12). A light irradiation device (1) characterized by comprising:

A sixth invention is the light irradiation device (1) according to any one of the first invention to the fifth invention, wherein the light source section (30) includes a substrate (32) and a It comprises a light-emitting element (31) mounted thereon and a frame-shaped holder (20) integrally fixed to the substrate (32) and holding the diffractive optical element (10, 50). It is a light irradiation device (1).

A seventh invention is the light irradiation device (1) according to any one of the first invention to the sixth invention, wherein the diffraction layer (115) is provided at a position closest to the light source section (30). The light irradiation device (1) characterized in that the diffraction layer (115) is arranged such that the convex portions (111a) and the concave portions (112) face the light source portion (30) side. is.

ADVANTAGE OF THE INVENTION According to this invention, a light irradiation apparatus with high heat resistance can be provided.

It is an exploded perspective view of light irradiation device 1 of this embodiment. 1 is a perspective view of a light irradiation device 1; FIG. 1 is a cross-sectional view of a light irradiation device 1; FIG. 2A and 2B are diagrams illustrating a diffractive optical element 10; FIG. 2 is a cross-sectional view for explaining the configuration of the diffractive optical element 10; FIG. It is sectional drawing of the light irradiation apparatus 1 of 2nd Embodiment. It is sectional drawing of the light irradiation apparatus 1 of 3rd Embodiment. It is sectional drawing of the light irradiation apparatus 1 of 4th Embodiment. It is a figure which shows the modification of the light irradiation apparatus 1 of 4th Embodiment. It is sectional drawing of the light irradiation apparatus 1 of 5th Embodiment. It is a figure which shows the modification of the light irradiation apparatus 1 of 5th Embodiment. 4 is a diagram showing an example of a configuration including a diffractive optical element 70 having resin layers 11 on both sides of a glass layer 41. FIG. 4 is a diagram showing an example of a configuration including a diffractive optical element 70 having resin layers 11 on both sides of a glass layer 41. FIG. 4 is a diagram showing an example of a configuration including a diffractive optical element 70 having resin layers 11 on both sides of a glass layer 41. FIG. 4 is a diagram showing an example of a configuration including a diffractive optical element 70 having resin layers 11 on both sides of a glass layer 41. FIG. 4 is a diagram showing an example of a configuration including a diffractive optical element 70 having resin layers 11 on both sides of a glass layer 41. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is an exploded perspective view of a light irradiation device 1 of this embodiment.
FIG. 2 is a perspective view of the light irradiation device 1. FIG.
FIG. 3 is a cross-sectional view of the light irradiation device 1. As shown in FIG.
FIG. 4 is a diagram illustrating the diffractive optical element 10. FIG.
1 to 4 are schematic diagrams, and the size and shape of each part are exaggerated as appropriate to facilitate understanding.
Also, in the following description, specific numerical values, shapes, materials, and the like are shown and described, but these can be changed as appropriate.

In this specification, terms specifying shapes and geometrical conditions, such as parallel and orthogonal terms, have strict meanings, as well as similar optical functions to the extent that they can be regarded as parallel or orthogonal. It also includes states with errors.
In this specification, terms such as plate, sheet, and film are used, and as a general usage, they are used in the order of thickness, plate, sheet, and film. I use it in my book as well. However, since there is no technical meaning in such proper use, these words can be replaced as appropriate.
In this specification, the sheet surface refers to a surface of each sheet that is in the plane direction of the sheet when the sheet is viewed as a whole. It should be noted that the plate surface and the film surface are assumed to be the same.
In the present invention, the term "transparent" refers to a material that transmits at least the light of the wavelength used. For example, even if a material does not transmit visible light, if it transmits infrared light, it is treated as transparent when used for infrared applications.

As shown in FIG. 1 , the light irradiation device 1 includes a diffractive optical element 10 , a holder 20 , a light source section 30 and a cover glass 40 .
A diffractive optical element (optical element) 10 is an element that controls the traveling direction of light by a diffraction phenomenon. The diffractive optical element 10 has a diffraction grating group composed of a plurality of regions (partial periodic structures) having different periodic structures. The diffraction grating group has, for example, regions B to G as a partial periodic structure, as shown in FIG. The light incident on the diffraction grating group of the diffractive optical element 10 is irradiated as substantially uniform light in the range of 0 to 90 degrees due to the diffraction phenomenon in the B to G regions.

FIG. 5 is a cross-sectional view for explaining the configuration of the diffractive optical element 10. As shown in FIG.
The diffractive optical element 10 has a resin layer 11 and a base material 12 .
For the resin layer 11, an original plate having an uneven shape corresponding to a diffraction grating is used, for example, an ultraviolet curable resin applied on a base material is molded to transfer the uneven shape, and the resin layer 11 is cured by irradiating with ultraviolet rays. can be formed by

As the ultraviolet curable resin, for example, urethane acrylate, polyester acrylate, epoxy acrylate, polyether acrylate, polythiol, butadiene acrylate, and the like can be used. In addition, the material for forming the resin layer 11 is not limited to the ultraviolet curable resin. The resin layer 11 may be formed of, for example, an electron beam curable resin. Also, the resin layer 11 may be configured using a thermosetting or ultraviolet curing SOG (Spin on Glass). Further, the concave-convex shape corresponding to the diffraction grating is not limited to the example of transferring from the original plate by molding, but may be formed using a resin intermediate plate produced from the original plate having the concave-convex shape.

The base material 12 is a member that serves as a base for shaping the resin layer 11 . Examples of the base material 12 include polycarbonate (PC) resin, polyethylene terephthalate (PET) resin, methyl methacrylate-butadiene-styrene (MBS) resin, methyl methacrylate-styrene (MS) resin, and acrylic-styrene (AS) resin. A transparent resin such as acrylonitrile-butadiene-styrene (ABS) resin can be used.
The adhesion layer 13 is a layer that is applied on the base material 12 to improve adhesion with an ultraviolet curable resin or the like.

As shown in FIG. 5, the uneven shape of the diffraction grating has a high refractive index portion 111 in which a plurality of convex portions 111a are arranged in a cross-sectional shape. The high refractive index portion 111 extends in the depth direction of the cross section.
FIG. 5 shows an example of the high refractive index portion 111 in which the convex portion 111a has a 2-level shape of a bottom portion and a top portion. good.

In addition, air exists in the upper region including the recesses 112 formed between the protrusions 111a and the spaces 113 near the tops of the protrusions 111a. Therefore, the concave portion 112 and the space 113 form a low refractive index portion 114 having a lower refractive index than the high refractive index portion 111 . The periodic structure in which the high refractive index portions 111 and the low refractive index portions 114 are alternately arranged constitutes a diffraction layer 115 having a function of shaping light.

The diffraction layer 115, as shown in FIG. 4, has a plurality of regions B to G having different periodic structures. Since the light incident on the diffraction layer 115 is diffracted in a plurality of directions by the regions B to G, the light can be shaped into an arbitrary shape and irradiated.
The diffraction layer 115 is designed using various simulation tools such as GratingMOD (manufactured by Rsoft) using a rigorous coupled wave analysis (RCWA) algorithm and Virtuallab (manufactured by LightTrans) using an iterative Fourier transform algorithm (IFTA). can be done.

When the diffractive optical element 10 is for infrared rays, the depth of the concave portion 112 is desirably 650 nm or more. More specifically, for example, when calculating with a wavelength of 780 nm and a refractive index of 1.6, a depth of 650 nm is required for 2-level, 975 nm for 4-level, and 1137 nm for 8-level.
For example, for a laser beam of 980 nm, when designing a rectangular diffusion shape with a refractive index of 1.6 and a long side of ±50° × short side of ±3.3° with 2-level design, diffraction optics The optimum depth of the element 10 is 1087 nm, the width of the finest irregularities is 250 nm, and the maximum aspect ratio exceeds 4.
As described above, the longer the wavelength of the incident light, the deeper the optimum depth of the diffractive optical element 10. However, when using an infrared wavelength of 780 nm or more, the depth of the concave portion 112 of the diffraction layer 115 should be 650 nm or more. Preferably, it is 900 nm or more in view of optical properties.
Although the upper limit of the depth of the concave portion 112 depends on the aspect ratio of the uneven shape, if it is 3 μm or less, more preferably 2 μm or less, the mold can be formed with good transfer accuracy.

Next, the thickness of the resin layer 11 will be described.
In FIG. 5, the thickness t1 obtained by removing the depth d1 of the uneven shape from the resin layer 11 depends on the depth of the pattern formed by the mold forming, but from the viewpoint of the filling property of the uneven shape formed by the mold forming, d1 It is preferable to set it as above.
Moreover, if the thickness t2 of the resin layer 11 is too thick, the resin layer tends to warp, so it is preferable to set the thickness t2 to 20 μm or less. The lower limit of the thickness depends on the depth of the concave portions 112 of the diffraction layer 115 to be formed, but can be 2 μm or more, preferably 4 μm or more.

In the light irradiation device 1 of the first embodiment, the diffraction optical element 10 is arranged such that the diffraction layer 115 is positioned on the light exit side (upper side in FIG. 3).

The holder 20 is a frame-shaped member for mounting the diffractive optical element 10 thereon. The holder 20 is made of, for example, engineering plastic such as polyamide or polycarbonate. In order to make the holder 20 difficult to deform, polycarbonate or the like may contain glass fibers.
The holder 20 has an opening penetrating through the center. The holder 20 has a top portion 20a on which the peripheral portion of the diffractive optical element 10 is placed. The diffractive optical element 10 is mounted and fixed on the top portion 20a with an adhesive 60 interposed therebetween. In addition, although the top portion 20a of the holder 20 of the present embodiment is configured as a flat surface, a groove may be further provided.

The light source unit 30 projects light onto the diffractive optical element 10 . The light source unit 30 has a light emitting element 31 that emits infrared light, blue light, or the like. As the light emitting element 31, for example, a laser light source such as a vertical cavity surface emitting laser (VCSEL) may be used, or an LED (light emitting diode) may be used. The light emitting element 31 is mounted on the substrate 32 . In addition, depending on the form of the light emitting element 31, the wiring 33 can be used to connect to the substrate.
The light source unit 30 is attached to the back side of the holder 20 (lower side in FIG. 3) using an adhesive or the like (not shown).

The cover glass 40 is a member arranged on the side from which the light from the light source section 30 is emitted from the diffraction layer 115 of the diffractive optical element 10 , and includes a glass layer 41 and an antireflection layer 42 .
The glass used for the glass layer 41 is desirably glass having a low coefficient of thermal expansion and heat resistance. Further, in this embodiment, the thickness of the glass layer 41 is set to 0.2 mm to 0.7 mm.
Antireflection layers 42 are formed on both surfaces of the cover glass 40 . As the antireflection layer 42, a commonly used single-layer or multi-layer coating can be suitably used. good.
By providing the anti-reflection layer 42, it is possible to suppress reflection at the interface of the glass layer 41, thereby enhancing the efficiency of light utilization.

In this embodiment, as described above, the cover glass 40 is further provided on the exit side of the diffractive optical element 10 . The reason for this will be explained.
As shown in FIG. 2, the light irradiation device 1 of this embodiment is configured as one component by combining the light emitting element 31 and the diffractive optical element 10 . This light irradiation device 1 is used by being mounted on a substrate depending on the application. The light irradiation device 1 is arranged as one part on substrates (not shown) of various devices with a solder paste (cream solder) sandwiched therebetween, and then soldered by melting the solder paste in a high-temperature environment. .

The diffraction layer 115 of the diffraction optical element 10 is composed of the resin layer 11 . If the cover glass 40 were not present, there is a risk of deformation due to direct exposure to the high-temperature environment during mounting of the light irradiation device 1 . Since the cover glass 40 is provided, the resin layer 11 does not come into direct contact with high-temperature air, so that the resin layer 11 can be prevented from becoming hot. Since the substrate 32 is provided on the light emitting element 31 side of the diffractive optical element 10, it is not directly exposed to high-temperature air.

A space surrounded by the holder 20 in which the light emitting element 31 is provided is a closed space. The light irradiation device 1 is assembled in a dry, low-humidity environment, but if the cover glass 40 is not present, moisture may enter the space through the diffractive optical element 10 . In this case, internal condensation may occur, and in such a case, appropriate light irradiation cannot be performed. However, in the present embodiment, since the cover glass 40 is provided, it is possible to prevent moisture from entering the space surrounded by the holder 20 and to prevent internal condensation.

Furthermore, the provision of the cover glass 40 can prevent physical damage such as crushing of the uneven shape due to collision of an external object with the resin layer 11 .

As described above, according to the first embodiment, since the cover glass 40 is provided, the diffraction layer 115 of the resin layer 11 is not directly exposed to high-temperature air, and the heat resistance of the light irradiation device 1 is improved. can be improved.
In addition, the light irradiation device 1 can prevent internal condensation.
Furthermore, the light irradiation device 1 can prevent the diffraction layer 115 from being physically damaged.

(Second embodiment)
FIG. 6 is a cross-sectional view of the light irradiation device 1 of the second embodiment.
In addition, in each embodiment shown below, the same code|symbol is attached|subjected to the part which achieves the same function as 1st Embodiment mentioned above, and the overlapping description is abbreviate|omitted suitably.
In the light irradiation device 1 of the second embodiment, three diffractive optical elements 10 are arranged in an overlapping manner. Each diffractive optical element 10 is adhered using an adhesive 60 at the peripheral portion thereof.
When a plurality of diffractive optical elements 10 are stacked in this manner, the cover glass 40 should be placed closest to the light exit side (uppermost in FIG. 6).
It should be noted that the diffractive optical element 10 can have different specific forms (characteristics) for shaping light for each of the plurality of stacked diffractive optical elements.

Also in the second embodiment described above, since the cover glass 40 is arranged at the position closest to the surface, the same effect as in the first embodiment can be obtained.

(Third Embodiment)
FIG. 7 is a cross-sectional view of the light irradiation device 1 of the third embodiment.
The light irradiation device 1 of the third embodiment includes a diffractive optical element 50 instead of the diffractive optical element 10 and the cover glass 40 of the first embodiment.
The diffractive optical element 50 includes a glass layer 41 , an antireflection layer 42 and a resin layer 11 . This diffractive optical element 50 has a form in which the substrate 12 of the diffractive optical element 10 in the first embodiment is replaced with a glass layer 41 . Therefore, the structures of the glass layer 41, antireflection layer 42, and resin layer 11 are the same as those of the glass layer 41, antireflection layer 42, and resin layer 11 of the first embodiment.
The antireflection layer 42 is not provided on the resin layer 11 side. This is because this position is not an air interface and therefore has a low reflectance. Further, an adhesion layer 13 may be further provided between the glass layer 41 and the resin layer 11 .
In the third embodiment, the glass layer 41 is arranged on the light emitting side of the resin layer 11 . With such an arrangement, the glass layer 41 can protect the diffraction layer 115 of the resin layer 11 as in the first embodiment. Also, depending on the thickness of the glass layer 41 , it is possible to prevent the position of the diffraction layer 115 from being too far from the light emitting element 31 due to the thickness of the glass layer 41 .

In the third embodiment described above, since the glass layer 41 is used as the base material of the diffractive optical element 50, the same effects as in the first embodiment can be achieved with a simpler configuration.

(Fourth embodiment)
FIG. 8 is a cross-sectional view of the light irradiation device 1 of the fourth embodiment.
The light irradiation device 1 of the fourth embodiment has a configuration in which three diffractive optical elements 50 are laminated and a cover glass 40 is arranged on the most light exiting side. Note that the cover glass 40 and the diffractive optical element 50 are the same as those in the previous embodiment.
In this embodiment, the diffractive optical element 50 closest to the light emitting element 31 is arranged with the resin layer 11 facing the light emitting element 31 side, and the other two diffractive optical elements 50 have the resin layer 11 on the light output side. placed towards.
FIG. 9 is a diagram showing a modification of the light irradiation device 1 of the fourth embodiment.
As shown in FIG. 9, the central diffractive optical element 50 may be arranged such that the resin layer faces the light emitting element 31 side.

As in the fourth embodiment described above, a plurality of diffractive optical elements 50 may be stacked and used. Further, since the resin layer 11 of the diffractive optical element 50 arranged closest to the light exit side is arranged facing the light exit side, in the present embodiment, the cover glass 40 is further arranged on the light exit side, and the first embodiment is arranged so as to face the light exit side. achieves the same effect.

(Fifth embodiment)
FIG. 10 is a cross-sectional view of the light irradiation device 1 of the fifth embodiment.
In this embodiment, the diffractive optical element 50 closest to the light emitting element 31 is arranged with the resin layer 11 facing the light emitting element 31 side, and the second diffractive optical element 50 from the light emitting element 31 side is the resin layer 11 is arranged toward the exit side, and the resin layer 11 of the diffractive optical element 50 closest to the light exit side is arranged toward the light emitting element 31 side.
The light irradiation device 1 of the fifth embodiment has three laminated diffractive optical elements 50 and does not have a cover glass 40 . However, in the light irradiation device 1 of the fifth embodiment, the resin layer 11 of the diffractive optical element 50 closest to the light output side is arranged toward the light emitting element 31 side. Therefore, the glass layer 41 is arranged closest to the light output side (excluding the antireflection layer 42). Thereby, heat resistance can be improved without providing the cover glass 40 .
FIG. 11 is a diagram showing a modification of the light irradiation device 1 of the fifth embodiment.
As shown in FIG. 11, the central diffractive optical element 50 may be arranged such that the resin layer faces the light emitting element 31 side.

As in the fifth embodiment described above, when a plurality of diffractive optical elements 50 are stacked and used, the resin layer 11 of the diffractive optical element 50 arranged closest to the light output side faces the light emitting element 31 side. That is, by arranging the glass layer 41 on the light exit side, the same effect as in the first embodiment is realized.

(deformed form)
Various modifications and changes are possible without being limited to the embodiments described above, and they are also within the scope of the present invention.

(1) In each embodiment, the number of diffractive optical elements 10 or 50 is not limited to the illustrated number, and can be changed as appropriate.

(2) In each of the embodiments, the diffractive optical element 10 or the diffractive optical element 50 has been described by exemplifying a diffraction grating having a two-level concavo-convex structure. It is not limited to this, and may be configured by, for example, a diffraction grating having a multi-stage concave-convex structure.

(3) In each embodiment, an example in which the resin layer 11 is formed only on one surface of the glass layer 41 has been described. For example, a configuration in which the resin layers 11 are provided on both sides of the glass layer 41 and diffraction gratings are configured on both sides of the glass layer 41 may be included.
12 to 16 are diagrams showing examples of configurations including the diffractive optical element 70 having the resin layers 11 on both sides of the glass layer 41. FIG. It should be noted that the same reference numerals are provided for the same configurations as those of the above-described embodiments. In addition, in the examples shown in FIGS. 12 to 16, the glass layer 41 is arranged on the light exit side, and the same effects as those of the above embodiments can be expected.

Although the first to third embodiments and modifications can be used in combination as appropriate, detailed description thereof will be omitted. Moreover, the present invention is not limited to each embodiment described above.

1 Light irradiation device 10 Diffraction optical element 11 Resin layer 12 Base material 13 Adhesion layer 14 Glass layer 20 Holder 20a Top part 30 Light source part 31 Light emitting element 32 Substrate 33 Wiring 40 Cover glass 41 Glass layer 42 Antireflection layer 50 Diffraction optical element 60 Adhesion Material 70 Diffractive optical element 111 High refractive index portion 111a Convex portion 112 Concave portion 113 Space 114 Low refractive index portion 115 Diffractive layer

Claims (5)

a diffractive optical element that diffracts and emits incident light;
a light source unit that projects light onto the diffractive optical element;
A light irradiation device comprising
The diffractive optical element is
a diffraction layer having a high refractive index portion in which convex portions are arranged side by side, and a low refractive index portion including concave portions formed between the convex portions;
a glass layer disposed on a side of the diffraction layer from which the light from the light source part is emitted from any of the diffraction layers;
with
The light irradiation device, wherein the diffraction layer is arranged on both sides of a substrate. In the light irradiation device according to claim 1,
comprising an antireflection layer laminated on the glass layer;
A light irradiation device characterized by: In the light irradiation device according to claim 1 or claim 2,
the glass layer also serves as a base material for the diffraction layer;
A light irradiation device characterized by: In the light irradiation device according to any one of claims 1 to 3,
The light source unit
a substrate;
a light emitting element attached to the substrate;
a frame-shaped holder integrally fixed to the substrate and holding the diffractive optical element;
A light irradiation device characterized by: In the light irradiation device according to any one of claims 1 to 4,
The diffraction layer provided closest to the light source part among the diffraction layers is arranged such that the convex part and the concave part face the light source part side,
A light irradiation device characterized by:

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