JP2012191246A - High resolution imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high resolution imaging apparatus capable of improving MTF and resolution.SOLUTION: The high resolution imaging apparatus comprises: an optical system 11 which forms a subject image of a subject 1; at least one functional imaging elements 14 which comprises plural light-receiving elements for converting the subject image to an electric signal by each of plural divided regions; and an optical waveguide element 13 which is disposed between the optical system 11 and the functional imaging elements 14 and in which there are plural optical waveguides 12 for transmitting the subject image divided into the regions. The pitch of the light-receiving elements matches that of the functional imaging element 14 side of the optical waveguides 12.

Description

  The present invention relates to a high-resolution imaging apparatus, and more particularly to a high-resolution imaging apparatus including a functional imaging element.

  Until now, an imaging apparatus aimed at increasing the resolution has been proposed (see, for example, Patent Document 1). FIG. 10 shows a schematic configuration of the imaging apparatus 50 disclosed in Patent Document 1. In this method, the image of the subject 51 formed by the optical system 52 is guided to the imaging surfaces 54 a of the plurality of imaging elements 54 by the plurality of optical fiber bundles 53. The optical fiber bundle 53 is formed by bundling a plurality of optical fibers, and is configured such that a plurality of optical fibers are assigned to each pixel (light receiving element) of the image sensor 54.

  In recent years, functional imaging devices such as pixel peripheral recording type imaging devices have been proposed due to the progress of semiconductor technology (see, for example, Patent Document 2).

JP 2003-283906 A JP 2008-288449 A

  However, the number of optical fibers allocated to the pixels of the image sensor disclosed in Patent Document 1 is not uniform for each pixel, and it is considered that the optical fibers cannot actually be allocated equally. Furthermore, Patent Document 1 also shows that there is an optical fiber arranged across two pixels.

  In other words, in the imaging device disclosed in Patent Document 1, the optical waveguide that transmits the subject image and the light receiving element arranged for each pixel do not correspond one-to-one. In such a case, the absolute value (MTF: Modulation Transfer Function) and resolution of the optical transfer function are lowered. Here, the MTF expresses how faithfully the contrast of a subject can be reproduced as a spatial frequency characteristic. Further, although the input surfaces of the plurality of optical fiber bundles are divided into a plurality according to the number of image sensors, it is very difficult to align the input surfaces with each other with high accuracy.

  FIG. 11 is a conceptual diagram schematically showing a part of a region where pixels are arranged (hereinafter referred to as a pixel area) in the functional imaging device disclosed in Patent Document 2. In the pixel area 61, a plurality of pixels 62 (only six are shown in FIG. 11) are arranged. In the pixel 62, in addition to the light receiving element 63, a functional circuit 64 including a memory, an ADC circuit, and the like is disposed. This functional circuit 64 has most of the area of one pixel (for example, 80% or more). ).

As a result, the area of the pixel 62 increases, and the interval between the light receiving elements 63 adjacent to each other in the horizontal and vertical directions (hereinafter referred to as pixel pitches P _X and P _Y ) increases. If the area of the pixel 62 is large, the number of pixels that can be arranged in the image area defined by the optical system is reduced, so that it is difficult to increase the resolution.

  In the functional imaging device disclosed in Patent Document 2, in order to improve the MTF by making one-to-one correspondence between the optical waveguide that transmits the subject image and the light receiving element 63 arranged for each pixel 62, It is conceivable to process and combine a plurality of fiber optical plates (FOPs). As shown in the cross-sectional view of FIG. 12, the FOP 71 is manufactured by bundling a plurality of optical fibers composed of a core 72 and a clad 73, and melting and sintering each other. The cross-sectional areas of the core 72 and the clad 73 on the input surface 74 and the output surface 75 are not changed.

  As a modification of the FOP 71 shown in FIG. 12, a tapered FOP 81 with a taper as shown in FIG. 13 is actually commercialized. This is obtained by stretching one of the FOPs 71 in FIG. 12 while further heating. The cross-sectional areas of the core 82 and the clad 83 on the input surface 84 and the output surface 85 are different, but the area ratio is not changed.

  However, it is not realistic to process the FOPs 71 and 81 made of a glass material with an accuracy corresponding to the cores 72 and 82 and the light receiving element 63 of the imaging element in a one-to-one correspondence. This causes a decrease in the aperture ratio of the FOPs 71 and 81 on the light receiving element 63 side in addition to the decrease in MTF and resolution. Furthermore, it is necessary to align a plurality of FOPs 71 and 81 in correspondence with a plurality of image sensors, but this is difficult in practice.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a high-resolution imaging apparatus capable of improving the MTF and the resolution as compared with the conventional technique.

  In order to solve the above-described problem, the high-resolution imaging apparatus of the present invention includes at least an optical system that forms a subject image and a plurality of light receiving elements that convert the subject image into electrical signals for each of the divided regions. One functional imaging device, and an optical waveguide device disposed between the optical system and the functional imaging device, and formed with a plurality of optical waveguides that transmit the subject image divided into a plurality of the regions. , And the pitch of the light receiving element and the pitch of the optical waveguide on the side of the functional imaging element coincide with each other.

  With this configuration, the light receiving element and the optical waveguide of the functional imaging element have a one-to-one correspondence, and the light receiving surface of each light receiving element and the output end face of each optical waveguide are opposed to each other. Can be improved.

The high-resolution imaging device of the present invention has a configuration in which the pitch of the optical waveguide on the optical system side is smaller than the pitch on the functional imaging device side.
With this configuration, it is possible to realize a high-resolution imaging device including an optical waveguide element that secures a sufficient aperture ratio.

  In the high-resolution imaging device of the present invention, the optical waveguide may be a self-forming optical waveguide, and the functional imaging device may be a pixel peripheral recording type imaging device.

  In the present invention, the light-receiving element and the optical waveguide of the functional imaging element have a one-to-one correspondence, and the light-receiving surface of each light-receiving element and the output end face of each optical waveguide face each other. It is an object of the present invention to provide a high-resolution imaging apparatus capable of improving

Schematic showing the configuration of a high-resolution imaging apparatus according to the present invention Front view and rear view showing a configuration of an optical waveguide element in which an optical waveguide is formed Top view showing the configuration of the functional image sensor Sectional view showing configuration of high-resolution image sensor Process drawing which shows the manufacturing method of the optical waveguide element of the high-resolution imaging device which concerns on this invention Sectional drawing which shows the structure of the optical waveguide formed using the reduction optical system Sectional drawing which shows the structure of several optical waveguide bundles formed using several parallel light from which an incident angle differs Sectional drawing which shows the structure of the several optical waveguide bundle formed using the reduction optical system Top view showing the configuration of a butted functional imaging device Schematic showing the configuration of a conventional imaging device using an optical fiber bundle Conceptual diagram showing a part of a pixel area of an imaging device Sectional view showing the configuration of the FOP Sectional drawing which shows structure of tapered FOP

  Hereinafter, embodiments of a high-resolution imaging apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a high-resolution imaging apparatus 10 according to the present invention. As shown in FIG. 1, the high-resolution imaging device 10 includes at least an optical system 11 that forms a subject image of the subject 1 and a plurality of light receiving elements that convert the subject image into electrical signals for each of the divided regions. Optical waveguide element in which a plurality of optical waveguides 12 that are disposed between one functional imaging element 14 and between the optical system 11 and the functional imaging element 14 and that divide and transmit a subject image into the plurality of regions are formed 13 and so on.

  The optical system 11 may be composed of a single lens as shown in FIG. 1, but may be composed of a combination lens.

  The optical waveguide 12 of the optical waveguide element 13 corresponds to the core of the optical fiber, and the periphery of the optical waveguide 12 corresponds to the cladding. Hereinafter, the periphery of the optical waveguide 12 is referred to as a cladding portion 15. Further, hereinafter, the optical waveguide element 13 and at least one functional imaging element 14 are referred to as a high resolution imaging element 20.

Functional imaging device 14 is, for example, a storage image sensor has a pixel area P _A composed of a plurality of pixels. Further, each pixel in the pixel area P _A, with one light receiving element (e.g., photodiode). Each pixel has a functional circuit including a memory, an ADC circuit, and the like in addition to the light receiving element.

  FIG. 2 is a schematic diagram showing a configuration of the optical waveguide element 13 in which the optical waveguide 12 is formed. 2A is a front view showing a surface of the optical waveguide element 13 facing the optical system 11, and FIG. 2B is a rear view showing a surface of the optical waveguide element 13 facing the functional imaging element 14. As shown in FIG. is there.

  In order to avoid the complexity of the drawing, FIG. 2 shows the optical waveguide element 13 corresponding to the case where the number of the functional imaging elements 14 is four. Note that the optical waveguide element 13 in FIG. 1 corresponds to the cross section along line AA ′ in FIG. 2. Further, the number and arrangement positions of the functional imaging elements 14 are not limited to the examples shown in FIGS.

  The optical waveguide element 13 includes optical waveguide bundles 12-1, 12-2, 12-3, and 12-4 corresponding to the functional imaging elements 14. Each of the optical waveguide bundles 12-1 to 12-4 includes a plurality of optical waveguides 12. In order to obtain a sufficient aperture ratio for the optical waveguide element 13, the pitch of the optical waveguide 12 is preferably small on the optical system 11 side and large on the functional imaging element 14 side.

  Next, a detailed configuration of the high-resolution imaging device 20 including the optical waveguide device 13 in which the optical waveguide 12 is formed and a plurality of functional imaging devices 14 will be described. FIG. 3 is a top view illustrating the configuration of the functional image sensor 14, and FIG. 4 is a cross-sectional view illustrating the configuration of the high-resolution image sensor 20.

As shown in FIG. 3, the functional imaging element 14, around the pixel area P _A, and the peripheral circuit 14-1, and a bonding pad 14-2, a. As illustrated in FIG. 4, the high-resolution image sensor 20 includes a bonding wire 20-1, a package 20-2, and a cavity 20-3 in addition to the functional image sensor 14. The cavity 20-3 is provided in order to secure a space for placing the bonding wire 20-1 for connecting the package 20-2 and the bonding pad 14-2.

The optical Namijitaba 12-1 and 12-2, the peripheral circuits 14-1 surrounding the pixel area P _A, are preferably arranged in the form of a slanted roof so as to avoid the bonding pad 14-2.

Hereinafter, a method for manufacturing the optical waveguide element 13 having the optical waveguide 12 therein will be described. Here, the case where the optical waveguide 12 is a self-forming optical waveguide is taken as an example.
First, as shown to Fig.5 (a), the 1st photocurable resin solution and the 2nd photocurable resin solution from which a 1st photocurable resin solution differs in the refractive index after hardening start wavelength and hardening. The mixed solution 30 is prepared and filled in the transparent container 31 (mixed solution preparation stage).

  Examples of the first photocurable resin solution include an epoxy photocurable resin solution having a refractive index of 1.49, and examples of the second photocurable resin solution include an acrylic resin having a refractive index of 1.34. The photocurable resin solution can be used.

Next, a resist is placed on the liquid surface of the mixed solution 30, and a mask pattern having an opening 32 a corresponding to the light receiving surface of the light receiving element of the functional imaging element 14 is exposed and developed by photolithography. As a result, a mask 32 that matches the horizontal and vertical pixel pitches P _X and P _Y of the functional image sensor 14 is formed (mask formation stage).

Next, as shown in FIG. 5 (b), through a mask 32, of the first and second photo-curable resin solution, parallel wavelengths lambda ₁ to cure only the first photo-curable resin solution The mixed solution 30 is irradiated with light 33. At this time, only the parallel light 33 that has passed through the opening 32a of the mask 32 enters the mixed solution 30, and the optical waveguide 12 (core portion) is formed in the traveling direction of the parallel light 33 (self-forming optical waveguide formation stage). . At this time, the second photocurable resin solution present in the portion where the parallel light 33 is incident in the mixed solution 30 is pushed to the portion where the parallel light 33 is blocked by the mask 32.

As the parallel light 33, for example, laser light having a wavelength λ ₁ of about 300 nm to 500 nm is preferably used. When irradiating the collimated beam 33 to the mixed solution 30 may be irradiated simultaneously laser light source and a plurality prepared for emitting a laser beam having a wavelength lambda _1, a laser for emitting a plurality of laser light having a wavelength lambda ₁ Irradiation may be performed using an array. Alternatively, irradiation may be performed sequentially by moving one or more laser light sources at the pixel pitch P _X or P _Y of the functional imaging element 14.

Next, the periphery of the optical waveguide 12 is cured by irradiating the entire mixed solution 30 on which the optical waveguide 12 is formed with ultraviolet light having a wavelength λ ₂ that cures both the first and second photocurable resin solutions. Thus, the clad portion 15 is formed (cladding portion forming stage). Finally, the mask 32 and the transparent container 31 are removed to complete the optical waveguide element 13.

Through the above-described steps, the optical waveguide element 13 in which the pitch of the output end face of the optical waveguide 12 (the side on which the mask 32 is formed) matches the pixel pitches P _X and P _{Y of the} functional imaging element 14 is formed. The As a result, the light receiving surface of the light receiving element of the functional imaging device 14 and the output end surface of the optical waveguide 12 can be arranged to face each other on a one-to-one basis.

  In addition, the shape of the optical waveguide 12 can be changed by irradiating the mixed solution 30 with the parallel light 33 through an appropriate optical system. FIG. 6 is a cross-sectional view showing the configuration of the optical waveguide 12 formed by irradiating the parallel light 33 through the reduction optical system 41. This is a configuration for producing the optical waveguide element 13 shown in FIGS. The parallel light 33 passes through the reduction optical system 41, and becomes a focused light 34 and enters the mixed solution 30. Thereby, the reverse tapered optical waveguide 12 can be formed.

At this time, similarly to the example shown in FIG. 5, the mask 32 that matches the pixel pitches P _X and P _Y of the functional image sensor 14 is used. Needless to say, if a magnifying optical system is used as the optical system 11, a tapered optical waveguide 12 can be formed, contrary to the example shown in FIG.

  FIG. 7 is a cross-sectional view showing a configuration of a plurality of optical waveguide bundles 12-1 and 12-2 formed by a plurality of parallel lights 33-1 and 33-2 having different incident angles. This is a configuration in the case where the high-resolution image sensor 20 has a plurality of functional image sensors 14. As shown in FIG. 7, a mask 32 having an opening 32b corresponding to the light receiving surfaces of the light receiving elements of the plurality of functional imaging elements 14 is formed on the liquid surface of the mixed solution 30, and parallel light 33-1, 33- is formed. A plurality of optical waveguide bundles 12-1 and 12-2 can be produced by irradiating the mixed solution 30 with 2 at different incident angles.

  As shown in FIG. 4, since the functional imaging device 14 includes a peripheral circuit 14-1 and bonding pads 14-2 related to wiring, the plurality of optical waveguide bundles 12-1 and 12-2 are appropriately connected to each other. It is preferable to form them separated by a distance D. In order to obtain the desired distance D, the incident angles of the parallel lights 33-1 and 33-2 may be adjusted as appropriate.

  FIG. 8 is a cross-sectional view showing a configuration of a plurality of optical waveguide bundles 12-1 and 12-2 formed by adding a reduction optical system 41 to the configuration of FIG. 7. As shown in FIG. 8, the parallel lights 33-1 and 33-2 having different incident angles are transmitted through the reduction optical system 41 to become the focused lights 34-1 and 34-2, as shown in FIG. It enters the mixed solution 30 through a mask 32. Thereby, the reverse-tapered optical waveguide bundles 12-1 and 12-2 can be formed.

  Similar to the example shown in FIG. 7, the mask 32 is formed so that the plurality of optical waveguide bundles 12-1 and 12-2 are formed at an appropriate distance D, and the reduction optical system 41 is interposed. The pitch of the input end face of the optical waveguide 12 is narrowed. Thereby, the optical waveguide element 13 suitable when the image area prescribed | regulated by the optical system 11 with which the high-resolution imaging device 10 is provided is narrow can be produced. Also in this case, in order to secure an appropriate distance D and a constant pitch, the parallel lights 33-1 and 33-2 are incident on the mixed solution 30 at an angle.

  As described above, the high-resolution imaging device according to the present invention has a one-to-one correspondence between the light receiving elements of the functional imaging elements and the optical waveguides, and the light receiving surfaces of the respective light receiving elements and the output end faces of the respective optical waveguides. Since they face each other, the MTF and the resolution can be improved as compared with the prior art.

  Usually, the yield of the image sensor decreases as the area of the pixel area increases. For this reason, a large area image sensor generally has a low yield. In contrast, the present invention can be manufactured by combining a plurality of small-area functional imaging elements that can ensure a sufficient yield.

  Further, according to the present invention, even in a functional image sensor having a relatively large pixel pitch, it is possible to obtain a high-resolution image sensor by connecting a plurality of functional image sensors without any device in layout. Become.

Conventionally, as a method of manufacturing the high-resolution image sensor 20 using a plurality of functional image sensors, a method in which functional image sensors capable of batting are connected and arranged in a mosaic pattern has been used. In order to realize this, it is necessary to connect a plurality of functional imaging elements 44 (four in the figure) as shown in FIG. That is, the layout of the functional image pickup device 44 needs to be special, such as combining the peripheral circuit 44-1 and the bonding pad 44-2 of the functional image pickup device 44 on one side. Further, in order to batting functional imaging element 44 to each other, functional imaging device 44 needs to be cut in the last pixel area P _A.

  For this reason, the above-described conventional method has a problem of unnecessary wiring delay caused by a special layout and a problem of noise due to dark current from an end face caused by cutting near the pixel.

  However, in the high-resolution imaging device 10 according to the present invention, the functional imaging elements 14 having a general layout as shown in FIG. 3 are arranged at a desired interval, and the optical waveguide 12 suitable for the arrangement is used. it can. For this reason, the high-resolution imaging device 10 according to the present invention can also avoid the problem of dark current seen in the functional imaging device that can be batting.

DESCRIPTION OF SYMBOLS 1 Subject 10 High-resolution imaging device 11 Optical system 12 Optical waveguide 12-1, 12-2, 12-3, 12-4 Optical waveguide bundle 13 Optical waveguide element 14, 44 Functional imaging element 14-1, 44-1 Circuit 14-2, 44-2 Bonding pad 15 Clad part 20 High-resolution imaging device 20-1 Bonding wire 20-2 Package 20-3 Cavity 30 Mixed solution 31 Transparent container 32 Mask 32a, 32b Opening 33 Parallel light 34 Focused light 41 Reduction optical system

Claims (4)

An optical system for forming a subject image;
At least one functional imaging element having a plurality of light receiving elements for converting the subject image into electrical signals for each of the divided areas;
An optical waveguide element disposed between the optical system and the functional imaging element, and formed with a plurality of optical waveguides that divide and transmit the subject image into the plurality of regions, and
A high-resolution imaging apparatus in which a pitch of the light receiving element and a pitch of the optical waveguide on the functional imaging element side coincide with each other.   The high-resolution imaging apparatus according to claim 1, wherein a pitch of the optical waveguide on the optical system side is smaller than a pitch on the functional imaging element side.   The high-resolution imaging device according to claim 1, wherein the optical waveguide is a self-forming optical waveguide.   The high-resolution imaging device according to any one of claims 1 to 3, wherein the functional imaging device is a pixel peripheral recording type imaging device.

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