JP3103577B2 - Imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device used for an electronic video camera or the like, and to an imaging device provided with an imaging lens including a holographic optical element.

[Conventional technology]

FIG. 5 shows an imaging lens of this type of conventional imaging apparatus which is formed by combining a holographic optical element (hereinafter referred to as HOE) with a glass lens or a plastic lens, and which performs chromatic aberration correction on a spectrum in the visible region. It is shown. This is configured by arranging an HOE 1, a first achromatic lens 2, a second HOE 3, and a second achromatic lens 4 in order. In addition, 5 is an imaging surface.

For example, as shown in FIG. 6, the HOE 1 or 3 is formed by exposing a predetermined pattern to a photosensitive layer 7 formed on a transparent substrate 6 and using a diffraction of light by this pattern to form a specific wavefront. It is something to play. That is, in FIG. 6, a coherent spherical wave diverging from a point O (object position) separated by S from the photosensitive layer 7 and d + b (d is the thickness of the substrate 6, b is the rear surface of the substrate 6) Distance to point I described later)
A state is shown in which the photosensitive layer 7 is irradiated with a coherent spherical wave that converges on a point I (imaging position) separated by only a distance, and an interference pattern thereof is recorded. When a spherical wave emitted from a point O having the same wavelength as that used for producing the HOE 1 or 3 is incident on the HOE 1 or 3 having the pattern formed in this way, the spherical wave focused on the point I at the HOE 1 or 3 To act as a lens (Appl.Op by Bennet)
t. 15 P542 (1976)).

Here, assuming that the focal length of HOE 1 or 3 is f, Holds. Here, n is the refractive index of the transparent substrate 6. U is defined by u = ± λ _C / λ _R , λ _C is the wavelength at the time of reproduction, and λ _R is the wavelength at the time of HOE1 or 3 creation. Therefore, if f, d, and n are selected so that b = 0, an image can be formed on the rear end face of the transparent substrate 6.

[Problems to be solved by the invention]

By the way, the HOE includes an off-axis type (off-axis type) which has a high diffraction efficiency because the traveling directions of the 0th-order diffracted light and the 1st-order diffracted light are different from each other, so that the unnecessary diffracted light and the object light are easily separated. There is an in-line type having low diffraction efficiency because it is difficult to separate unnecessary diffraction light and object light because the traveling directions of the first-order diffraction light are the same. Then, when the HOE having a low diffraction efficiency is used, the relative intensity of the unnecessary diffracted light, that is, the 0th-order diffracted light is increased, so that the influence of the background caused by the diffracted light becomes remarkable,
There is a problem that the contrast of the entire image by the imaging lens is reduced. On the other hand, to use HOE as a lens, the off-axis type causes the optical system to bend,
An in-line type is preferred. Therefore, in the conventional imaging lens described above, the HOE 1 or 3 combines two off-axis HOEs into an in-line type in order to increase the diffraction efficiency and not to bend the optical system. There is a problem of becoming high. Also, if the diffraction efficiency of the HOE itself is increased, the production of the HOE itself becomes troublesome, which also increases the manufacturing cost, and also causes a problem that the performance change due to the incident angle of the imaging lens including the HOE becomes large. .

The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging apparatus that can obtain an image with good contrast, has a small change in performance due to an incident angle, and can easily manufacture an HOE at a low manufacturing cost. I have.

[Means and Actions for Solving the Problems]

An imaging apparatus according to the present invention includes: an imaging lens for forming an object image; electronic imaging means for receiving an image formed by the imaging lens; and a video signal based on an output signal from the electronic imaging means. A signal processing means for generating an image, wherein the imaging lens includes at least one optical element that reproduces a specific wavefront using diffraction of light by a pattern, wherein the electronic imaging means Unnecessary diffracted light generated by an optical element that receives light of an object image formed by the imaging lens, generates a signal of the object image light, and reproduces a specific wavefront using diffraction of light by the pattern. And the signal of the unnecessary diffracted light is also generated at the same time, and the signal processing means is configured to remove or reduce the signal of the unnecessary diffracted light from the output signal of the electronic imaging means. It is characterized in that it includes a correction means for correcting calculating the.

Further, the invention is characterized in that the correction means has a subtraction circuit for subtracting a correction signal from an output signal of the electronic imaging means.

Further, according to the present invention, the correction means has a circuit for detecting the darkest part of the image from the output signal of the electronic imaging means,
It is characterized in that a value corresponding to the dark portion is input to the subtraction circuit as a correction signal.

Also, the present invention is configured such that the correction means receives an external input signal, changes a correction signal from the input signal, and inputs the changed correction signal to the subtraction circuit. Features.

 This will be described in detail.

FIG. 1 is a conceptual diagram of the present invention.
It comprises a positive lens 13 on which an HOE 12 is attached and which is configured to correct chromatic aberration, a negative lens 14, a stop 15, and a positive lens 16. Reference numeral 17 denotes a solid-state imaging device such as a CCD arranged on the imaging surface of the imaging lens 11, which is driven by a solid-state imaging device driving circuit 18. Reference numeral 19 denotes an imaging circuit including a process circuit, a matrix circuit, and the like, which subtracts a correction signal, which will be described later, from an output signal from the solid-state imaging device 17 and converts the resulting signal into a composite video signal.
And a correction signal generating circuit for generating a correction signal based on a signal from an external device or a signal from the outside (not shown). Reference numeral 22 denotes a display such as a CRT or a liquid crystal TV for displaying a video signal from the imaging circuit 19 as an image, and is driven by a display drive circuit 23. 24 is an eyepiece. Reference numeral 25 denotes recording means such as a magnetic tape for a TV camera for recording a video signal from the imaging circuit 19, a magnetic disk for an electronic still camera, and an optical disk. Needless to say, all circuits are synchronized.

According to the above configuration, an image formed by the imaging lens 11 is taken out as an electric signal by the solid-state imaging device 17, and the signal is converted into a video signal by the imaging circuit 19, and then displayed as an image on the display 22. Then, it is observed by the operator or recorded on the display 25. At this time, in the imaging circuit 19, the correction signal from the correction signal generation circuit 20 is subtracted from the signal from the solid-state imaging device 17, and the value of this correction signal is made closer to the bias value of the output signal from the solid-state imaging device 17. Then, a video signal with good contrast can be obtained. That is, unnecessary diffraction light by the HOE 12 appears as a bias component in the video signal, and the contrast is lowered by darkening the entire image, so that the bias component is removed or reduced as much as possible to lower the dark level of the image. If you do, the contrast will improve.

Therefore, according to the present invention, the effect of the background caused by the unnecessary diffracted light of the HOE is removed or reduced through the electronic circuit, so that an image with good contrast can be obtained. Also, since the diffraction efficiency of the HOE itself may be lowered, the change in performance due to the incident angle is reduced, and the HOE is easily manufactured and the manufacturing cost is reduced.

〔Example〕

Hereinafter, the present invention will be described in detail by assigning the same reference numerals to the same members as those shown in FIG. 1 based on the illustrated embodiment.

FIG. 2 is a diagram showing the configuration of the first embodiment, which is for correcting a video signal output from a frame memory.

26 is a process circuit, 27 is a luminance signal processing circuit, 28 is a chrominance signal processing circuit, 29 is a matrix circuit, 30 is a frame memory, 31 is a subtraction circuit, and 32 is an image based on image information stored in the frame memory 30. A bias instruction circuit for detecting a dark portion and causing a correction signal of a value (bias value) corresponding to the dark portion to enter a subtraction circuit 31. These components constitute the signal processing circuit 21, and the bias instruction circuit 32 A correction signal generation circuit 20 is provided.

Since the present embodiment is configured as described above, the output signal of the solid-state imaging device 17 is processed by the luminance signal processing circuit 27 and the color signal processing circuit 28 after passing through the process circuit 26, and then processed by the matrix circuit. The images are combined at 29 and become a color video signal, which is stored in the frame memory 30. Next, the bias instruction circuit 32 detects the darkest part of the image from the image information stored in the frame memory 30, and inputs a correction signal of a value (bias value) corresponding to the dark part to the subtraction circuit 31. Then, the subtraction circuit outputs a video signal from which the bias component has been almost removed from the video signal output from the frame memory 30. Therefore, the video signal sent to the display 22 is a signal in which the influence of the background due to the unnecessary diffraction light of the HOE 12 is almost eliminated, that is, a signal whose dark level is lowered, and the overall contrast is improved.

Thereafter, when the next color video signal is stored in the frame memory 30, the bias instruction circuit 32 detects the darkest portion of the next video again, and sets a correction signal of a new value (bias value) corresponding to the dark portion. Then, the same operation as described above is repeated, and a new image with good contrast is displayed on the display 22.

As described above, according to the present embodiment, the effect of the background caused by the unnecessary diffraction light of the HOE 12 is removed or reduced through the electronic circuit, so that an image with good contrast can be obtained. In addition, since the diffraction efficiency of the HOE 12 itself may be reduced, the change in performance due to the incident angle is reduced, and the HOE is easily manufactured and the manufacturing cost is reduced.

FIG. 3 is a diagram showing the configuration of the second embodiment, in which a video signal input to a frame memory is corrected.

That is, the frame memory 30 is provided before the process circuit 26, the subtraction circuit 31 is provided between the solid-state imaging device 17 and the frame memory 30, and the bias instruction circuit 32 is provided.
Detects the darkest part of the image from the image information stored in the frame memory 30 without doing anything, and corrects the next input video signal with a correction signal of a value (bias value) corresponding to the dark part. The signal is input to the subtraction circuit 31 for the sake of convenience.

 The operation principle of this embodiment is as follows.

First, if the solid-state imaging device drive circuit 18 is turned ON, a video signal is always output from the solid-state imaging device 17 at a predetermined timing. Therefore, before the image recording, the bias instruction circuit 32
Is reset, then the signal output from the solid-state imaging device 17 is stored in the frame memory 30 without doing anything. Therefore, the bias instruction circuit 32 detects the darkest part of the video signal stored in the frame memory 30, and sets a correction signal having a value (bias value) corresponding to the darkest part. Next, this correction signal is input to the subtraction circuit 31 to correct the next video signal. That is, in the present embodiment, the video signal of the subsequent screen is corrected by the correction signal of the value (bias value) obtained from the video signal of the previous screen, but if the screen is close in time ( In this embodiment, two continuous screens are used.) Since the bias values of these signals hardly change, this can be sufficiently corrected. If the imaging device is only one-shot imaging, such as an electronic still camera, the recording is completed by recording the corrected video signal by the recording means 25.

When the imaging device performs continuous shooting like a TV camera, the bias instruction circuit 32 detects the darkest part of the video signal stored in the frame memory 30 one after another. The corrected video signal is input to the frame memory 30, but the darkest part detected by the bias instruction circuit 32 should be at a constant level as long as the bias values are appropriate. Therefore, unlike the first embodiment in which a new correction value (bias value) is set for each detection, the bias instruction circuit 32 is of a type in which the correction value (bias value) remains without being cleared. belongs to. Further, if the correction value (bias value) becomes inappropriate, for example, too large, the darkest part of the video signal stored in the frame memory 30 becomes smaller than a predetermined value. Decrease the correction value (bias value). If the correction value (bias value) is too small, the reverse is true.

In both the one-shot shooting and the continuous shooting, if a step of clearing the bias instruction circuit 32 is inserted immediately before the start of the shooting operation, an appropriate correction value (bias value) can always be obtained, and therefore it is not always necessary. An image free from the influence of the diffracted light is obtained.

As described above, according to the present embodiment, the video signal
Since the correction is made before the data is stored in the memory 30 (the bias component is almost removed), even if the video signal is amplified thereafter, a high quality image utilizing the dynamic range of the frame memory 30 by 100% can be obtained.

FIG. 4 is a diagram showing the configuration of the third embodiment, which is capable of arbitrarily changing the correction value (bias value) of the bias instruction circuit by an external instruction such as an operator's instruction without having a frame memory. It was made.

That is, in the present embodiment, the bias component of the video signal from the solid-state imaging device 17 is almost completely eliminated in the subtraction circuit 31 by the correction signal from the bias instruction circuit 32 instructed from outside in real time, and the subsequent video signal is as described above. Similarly, the display 22 or the recording means 25 is passed through a usual signal processing means.
Sent to

Therefore, according to the present embodiment, the bias instruction circuit 32 can immediately and arbitrarily set a correction value (bias value) by an instruction from the outside, so that a video signal can be corrected in real time. In addition, the contrast of the image can be adjusted by changing the correction value.
Further, since the frame memory is omitted, the size and weight of the device are reduced, and the manufacturing cost is reduced.

〔The invention's effect〕

As described above, the imaging device according to the present invention has important practical advantages that a high-contrast image can be obtained, the performance change due to the incident angle is small, and the HOE can be easily manufactured and the manufacturing cost can be reduced. doing.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an image pickup apparatus according to the present invention, FIGS. 2 to 4 are diagrams showing the configuration of the first to third embodiments, respectively, and FIG. 5 is a diagram showing the configuration of a conventional imaging lens. FIG. 6 is a diagram showing the principle of HOE. 12… HOE, 13,16… Positive lens, 14… Negative lens, 15…
... Aperture, 17 ... Solid-state image sensor, 18 ... Solid-state image sensor drive circuit, 19 ... Imaging circuit, 20 ... Correction signal generation circuit, 21
... signal processing means, 22 ... display, 23 ... display drive circuit, 24 ... eyepiece, 25 ... recording means,
26 …… Process circuit, 27 …… Luminance signal processing circuit, 28 ……
A color signal processing circuit, 29 a matrix circuit, 30 a frame memory, 31 a subtraction circuit, 32 a bias instruction circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-126606 (JP, A) JP-A-1-284729 (JP, A) JP-A-1-178154 (JP, A) JP-A-2- 73301 (JP, A) JP-A-59-127 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/225 G02B 5/32 H04N 5/243

Claims (4)

(57) [Claims] An imaging lens for forming an object image, an electronic imaging means for receiving an image formed by the imaging lens, and a video signal generated based on an output signal from the electronic imaging means. An image pickup apparatus, comprising: an optical element that reproduces a specific wavefront by using at least one diffraction of light by a pattern, wherein the electronic image pickup unit includes: While receiving the light of the object image formed by the imaging lens and generating a signal of the object image light, unnecessary diffracted light generated by an optical element that reproduces a specific wavefront using diffraction of light by the pattern is also generated. Receiving and simultaneously generating an unnecessary diffracted light signal, the signal processing means corrects the signal so as to remove or reduce the unnecessary diffracted light signal from the output signal of the electronic imaging means. Imaging apparatus characterized by containing the that correction means. 2. The imaging apparatus according to claim 1, wherein said correction means has a subtraction circuit for subtracting a correction signal from an output signal of said electronic imaging means. 3. The correction means has a circuit for detecting the darkest part of the image from the output signal of the electronic image pickup means, and a value corresponding to the dark part is input to the subtraction circuit as a correction signal. The imaging device according to claim 2, wherein the imaging device is configured. 4. The apparatus according to claim 1, wherein said correction means receives an external input signal, changes a correction signal from the input signal, and inputs the changed correction signal to the subtraction circuit. The imaging device according to claim 2, wherein: