JP2021043230A - Wide-conversion lens and imaging apparatus - Google Patents

Abstract

To provide a wide-conversion lens which can provide an image having a different field angle and good image quality, when mounted on an imaging apparatus, and an imaging apparatus with this kind of a wide-conversion lens.SOLUTION: A wide-conversion lens according to one embodiment of the present invention is mounted to the object side of an imaging apparatus and satisfies conditional expressions (1) and (2). Expressions (1): 1.1<Ms/Cs, (2): 0.3<|Ff/DA|<2.0, where Cs represents the length in sagittal direction of on-axis luminous flux entering a face on the most object side of the wide-conversion lens, Ms represents the length in sagittal direction of luminous flux of maximum field angle entering a face on the most object side of the wide-conversion lens, DA represents a maximum air interval in the wide-conversion lens, and Ff represents the focal distance of a lens group closer to the object side than a position where the maximum air interval exists.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wide conversion lens and an imaging device to which a wide conversion lens is mounted.

In the field of imaging devices, wide conversion lenses that are attached to a main lens (lens of a main imaging device) to widen the angle of view (shorten the focal length) are known. For example, Patent Document 1 describes a wide-angle relay lens including a first lens having a negative refractive power and a second lens having a positive refractive power, and the characteristics of the lens satisfy the conditional expression. Further, Patent Document 2 describes a wide converter lens including a negative first lens having a meniscus power with a convex surface facing the object side and a positive second lens, and the characteristics of the lens satisfy the conditional expression.

On the other hand, in the field of imaging devices, a technique for acquiring an image of a subject without a lens has been developed in recent years. For example, in Non-Patent Document 1 below, a Fresnel zone plate is arranged close to an image sensor, and a projected image formed on the image sensor by light from a subject and a projection pattern corresponding to the Fresnel zone plate are superimposed. The image of the subject can be obtained without a lens by Fourier transforming the moire fringes. A technical report has been made on the technology of Non-Patent Document 1 by Non-Patent Document 2. Further, as in Non-Patent Documents 1 and 2, a lensless imaging technique using a Fresnel zone plate as a mask pattern is known (see Patent Document 3). In Patent Document 1, the image of the subject is reconstructed by Fourier transforming the moire fringes formed by incident light from the subject on two lattice patterns (Fresnel zone plates) arranged opposite to each other. ..

Japanese Unexamined Patent Publication No. 2012-93751 Japanese Unexamined Patent Publication No. 2014-56054 WO2016 / 203573

"Development of lensless camera technology that allows easy focus adjustment after video recording", [online], November 15, 2016, Hitachi, Ltd., [Search on May 8, 2017], Internet (http: //: www.hitachi.co.jp/New/cnews/month/2016/11/1115.html) "Lensless Light-field Imaging with Fresnel Zone Plate", Technical Report of the Institute of Image Information and Television Engineers, vol. 40, no. 40, IST2016-51, pp. 7-8, November 2016

Conventional wide conversion lenses have not been able to obtain images with different angles of view with good image quality when attached to an imaging device. For example, in the wide-angle relay lens described in Patent Document 1, according to the study by the inventors of the present application, the peripheral illumination ratio is improved, but the optical distortion is very large, about 44%, and the subject is too distorted when performing image recognition. I can't do it. Further, in the wide converter lens described in Patent Document 2, the off-axis luminous flux incident on the lens is thicker than the on-axis luminous flux, but the peripheral illumination ratio is low. In general, the peripheral illumination ratio of the lens decreases toward the periphery of the screen. Theoretically, the peripheral illumination ratio depends on the angle of view, and there is a relationship of RI = (cosγ) ^ 4 (RI (Relative Illumination) is the peripheral illumination ratio and γ is the half angle of view). For example, when the half angle of view is 30 deg, the RI is about 56.25%.

On the other hand, in the techniques described in Non-Patent Documents 1 and 2 and Patent Document 3 described above, refocusing (refocusing to a desired focusing distance afterwards by reconstructing an image) is possible, and the focal length (mm). ) Is f = 2 × β × d (β is the pitch of the Fresnel zone plate, and d is the distance (mm) between the image sensor and the Fresnel zone plate). When the angle of view (focal length) is changed in the image pickup apparatus having such a configuration, the pitch (β described above) and / or the position (d described above) of the Fresnel zone plate is changed. There are disadvantages to explain.

For example, in order to widen the angle (shorten the focal length), it is necessary to "(1) roughen the pitch of the FZP" or "(2) bring the Fresnel zone plate closer to the sensor (decrease the value of d)". In the case of (1), the angle of view resolution (resolution) decreases due to the decrease in the number of Fresnel zone plate stripes (a pattern composed of a region that transmits light and an region that blocks light), and in the case of (2). The closer the Fresnel zone plate is to the image sensor, the higher the required position accuracy of the Fresnel zone plate and the image sensor. On the other hand, in order to telephoto (longen the focal length), it is necessary to "(3) make the pitch of the Fresnel zone plate finer" or "(4) move the Fresnel zone plate away from the image sensor (increase the value of d)". There is. In the case of (3), the manufacturing difficulty increases due to the narrowing of the pitch, and in the case of (4), the image of the Fresnel zone plate is blurred on the image sensor due to the diffraction of light, and the image quality of the reconstructed image deteriorates. Considering the demerit of changing the angle of view due to such changes of β and d, it is conceivable to attach a wide conversion lens in front of the coded aperture (on the object side) to widen the angle of view. However, in conventional wide conversion lenses such as Patent Documents 1 and 2, images having different angles of view are good when mounted on an image pickup device having a coded aperture, as in the case of a general image pickup device using a lens. It was difficult to obtain good image quality.

As described above, in the conventional technique, it is difficult to obtain images having different angles of view with good image quality when the wide conversion lens is attached to the image pickup apparatus.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a wide conversion lens capable of obtaining images having different angles of view with good image quality when mounted on an imaging device. Another object of the present invention is to provide an image pickup apparatus capable of obtaining images having different angles of view with good image quality by using a wide conversion lens.

In order to achieve the above-mentioned object, the wide conversion lens according to the first aspect of the present invention is a wide conversion lens mounted on the object side of the image pickup apparatus, and the following conditional expressions (1) and (2) are used. Fulfill.

1.1 <Ms / Cs (1)
0.3 << Ff / DA | <2.0 (2)
However, Cs is the length in the sagittal direction of the axial light beam incident on the surface of the wide conversion lens on the most object side, and Ms is the sagittal direction of the light beam having the maximum angle of view incident on the surface of the wide conversion lens on the most object side. DA is the maximum air spacing in the wide conversion lens, and Ff is the focal length of the lens group on the object side of the position where the maximum air spacing exists.

If Ms / Cs ≦ 1.1, it becomes difficult to increase the amount of peripheral light, and if 2.0 ≦ Ms / Cs, the pupil aberration becomes too large and distortion and astigmatism increase. Further, when | Ff / DA | ≤0.3, the power of the front group becomes too strong and negative distortion occurs greatly, or the total length becomes long and miniaturization cannot be performed. On the other hand, if Ms / Cs and | Ff / DA | are in the range specified in the first aspect, the peripheral illumination ratio can be increased and the optical distortion can be reduced. As described above, the wide conversion lens according to the first aspect can obtain images having different angles of view with good image quality when attached to an imaging device.

In the first aspect, it is preferable that Ms / Cs <2.0 and 0.5 << Ff / DA | <1.5. This is because satisfying these conditional expressions further improves the peripheral illumination ratio and further reduces the distortion.

The wide conversion lens according to the second aspect satisfies the following conditional expression (3) in the first aspect.

2.2 <Mt / Ct (3)
However, Ct is the length of the axial light beam incident on the surface of the wide conversion lens on the most object side in the tangential direction, and Mt is the length of the light beam having the maximum angle of view incident on the surface of the wide conversion lens on the most object side. It is the length projected on the plane perpendicular to the main ray. If Mt / Ct ≦ 2.2, it is difficult to raise the peripheral illumination ratio, but if the characteristics of the wide conversion lens are within the range specified in the second aspect, the peripheral illumination ratio is increased and the optical distortion is decreased. be able to. In the second aspect, it is preferable that Mt / Ct <3.0. This is because when 3.0 ≦ Mt / Ct, the pupil aberration becomes too large, and distortion and astigmatism increase.

The wide conversion lens according to the third aspect satisfies the following conditional expression (4) in the first or second aspect.

| WCTL / WCf | <0.1 (4)
However, WCTL is the length from the first surface, which is the surface closest to the object side of the wide conversion lens, to the final surface, which is the surface farthest from the object side, and WCf is the focal length of the wide conversion lens. If | WCTL / WCf | exceeds the range specified in the third aspect, the afocal system collapses, the deviation from the back focus of the attached optical system becomes large, and the focus shifts when the user uses it. , | WCTL / WCf | is preferably within the range specified in the third aspect.

The wide conversion lens according to the fourth aspect satisfies the following conditional expression (5) in any one of the first to third aspects.

| Dist | <10 (5)
However, Dist is the optical distortion [%] when the wide conversion lens is attached to the ideal lens. Since distortion of about 10% can be recognized in object recognition in sensing applications, optical distortion can be tolerated up to 10%. In the fourth aspect, | Dist | <5 is preferable. This is because the distortion is further reduced.

The wide conversion lens according to the fifth aspect is composed of a front group of negative refractive power and a rear group of positive refractive power in order from the object side in any one of the first to fourth aspects. This is because the wide-angle lens can be easily widened by adopting the configuration of the fifth aspect.

In order to achieve the above-mentioned object, the image pickup apparatus according to the sixth aspect includes a wide conversion lens according to any one of the first to fifth aspects, and an image pickup apparatus main body to which the wide conversion lens is mounted. .. According to the sixth aspect, the wide conversion lens according to any one of the first to fifth aspects obtains images having different angles of view with good image quality (peripheral illumination ratio is improved and distortion is small). be able to.

In the sixth aspect, the image pickup device according to the seventh aspect has a coded aperture, an image sensor that outputs a signal of a projected image formed by the coded aperture, and a spatial region based on the signal. It has an image restoration unit for reconstructing an image, a wide conversion lens is mounted on the object side of the coded aperture, and a projected image is formed on the image sensor by the wide conversion lens and the coded aperture. An image pickup device using a coded aperture has a refocus function, but if an attempt is made to change the angle of view (focal length) by changing β and d, there are disadvantages such as deterioration of image quality and increase in manufacturing difficulty as described above. In addition, the peripheral illumination ratio decreases according to the cos4 law. However, according to the seventh aspect, by providing the wide conversion lens according to any one of the first to fifth aspects, it is possible to change the angle of view while eliminating these disadvantages, and it is also good. An image of high quality can be obtained.

In the seventh aspect of the image pickup apparatus according to the eighth aspect, the image restoration unit corrects aberrations caused by the wide conversion lens in the image in the spatial region. According to the eighth aspect, aberrations caused by the lens (astigmatism, spherical aberration, coma, distortion, axial chromatic aberration, chromatic aberration of magnification, etc.) are corrected, so that an image with good image quality can be obtained. .. Aberration correction may be performed before the image is reconstructed or after the image is reconstructed. When the aberration is corrected before the reconstruction, for example, the shape and / or size of the coded aperture to be multiplied by the projected image can be changed according to the type and / or amount of the aberration to be corrected. On the other hand, when correcting aberrations after reconstruction, for example, an image in which different filters (filters for point image restoration, etc.) are applied depending on conditions such as the type and / or degree of aberrations to be corrected and the position in the image. It can be done by processing. However, the correction of aberrations in the present invention is not limited to such an aspect.

In the eighth aspect, the image pickup apparatus according to the ninth aspect of the present invention includes a lens information acquisition unit that acquires information on a wide conversion lens, and the image restoration unit corrects aberrations based on the acquired information. According to the ninth aspect, the aberration can be corrected accurately and easily based on the information of the lens. The wide conversion lens may be provided with a lens information storage unit for storing lens information, and the lens information acquisition unit may acquire information from the lens information storage unit. Such a lens information storage unit can be configured by using a non-temporary recording medium.

In any one of the seventh to ninth aspects, the image pickup apparatus according to the tenth aspect has a coded aperture of a Fresnel zone plate, and an image restoration unit is formed on the image pickup element by a wide conversion lens and a Fresnel zone plate. A multiplied image is generated by multiplying the projected image to be a Fresnel zone pattern corresponding to the Fresnel zone plate, and the multiplied image is Fourier-transformed to reconstruct the image in the spatial region. In a tenth aspect, it is preferable to generate a multiplied image using a Fresnel zone pattern having a different magnification depending on the subject distance to be focused. This makes it possible to obtain an image in focus at a desired subject distance.

In the tenth aspect, it is preferable to reconstruct the image by the two-dimensional complex Fourier transform of the complex image. This is because a high-quality image without overlapping of subject images can be obtained. Specifically, in the Fresnel zone pattern, the first Fresnel zone pattern and the first Fresnel zone pattern have the same local spatial frequency in each region, and the second phase of the local spatial frequency is different. The image restoration unit is composed of a real part image and an imaginary part image as a multiplication image by multiplying the projected image by the first Fresnel zone pattern and the second Fresnel zone pattern, respectively. It is preferable to generate a complex image and reconstruct the image in the spatial region by performing a two-dimensional complex Fourier transform on the complex image.

The image pickup apparatus according to the eleventh aspect of the present invention is an interchangeable lens attached to and detached from the image pickup apparatus in any one of the seventh to tenth aspects. According to the eleventh aspect, lenses having different angles of view and focal lengths can be attached according to the purpose of shooting and shooting conditions, and shooting can be performed under desired conditions.

As described above, according to the wide conversion lens of the present invention, images having different angles of view can be obtained with good image quality when mounted on an imaging device. Further, according to the image pickup apparatus of the present invention, images having different angles of view can be obtained with good image quality by using a wide conversion lens.

FIG. 1 is a block diagram showing a configuration of an imaging device according to the first embodiment. FIG. 2 is a diagram showing another example of the configuration of the lens device. FIG. 3 is a diagram showing an example of a Fresnel zone plate. FIG. 4 is a block diagram showing the configuration of the processing unit. FIG. 5 is a diagram showing information stored in the storage unit. FIG. 6 is a diagram showing a lens configuration of Examples 1 to 4. FIG. 7 is a diagram showing an optical path of Examples 1 to 4. FIG. 8 is a diagram showing lens data of Examples 1 to 3. FIG. 9 is a diagram showing lens data of the fourth embodiment. FIG. 10 is a diagram showing aspherical coefficients of Examples 1, 2 and 4. FIG. 11 is a diagram showing the longitudinal aberration of the first embodiment. FIG. 12 is a diagram showing the longitudinal aberration of the second embodiment. FIG. 13 is a diagram showing the longitudinal aberration of the third embodiment. FIG. 14 is a diagram showing the longitudinal aberration of the fourth embodiment. FIG. 15 is a diagram showing specifications of Examples 1 to 4. FIG. 16 is a table showing the peripheral illumination calculation conditions of Examples 1 to 4. FIG. 17 is a diagram showing the definition of parameters. FIG. 18 is a table showing the amount of peripheral light of Examples 1 to 4. FIG. 19 is a graph showing the ideal lens and the peripheral illumination ratio of Examples 1 to 4. FIG. 20 is a flowchart showing an image reconstruction process. FIG. 21 is a diagram showing an example of Fresnel zone plates having different phases. FIG. 22 is a diagram showing a Fresnel zone pattern of the enlargement ratio according to the focusing distance.

Hereinafter, a mode for carrying out the wide conversion lens and the image pickup apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

<First Embodiment>
<Configuration of imaging device>
FIG. 1 is a block diagram showing a configuration of an image pickup apparatus 10 (imaging apparatus) according to the first embodiment. The image pickup device 10 includes a lens device 100 (wide conversion lens, interchangeable lens) and an image pickup device main body 200 (image pickup device main body). The image pickup device 10 can be applied to smartphones, tablet terminals, surveillance cameras, inspection cameras, and the like in addition to digital cameras, but the application target is not limited to these devices.

<Structure of lens device>
The lens device 100 includes a lens 300 (wide conversion lens, interchangeable lens). The lens 300 is a lens (wide conversion lens) that is attached to the image pickup apparatus main body 200 (on the subject side of the Fresnel zone plate 210) to widen the shooting angle of view as compared with the state in which the lens 300 is not attached. The lens device 100 and the image pickup device main body 200 are attached (attached) via the lens side mount 130 and the main body side mount 270 (lens attachment portion), and when attached, the lens side terminal 132 and the main body side terminal 272 come into contact with each other. Communication between the lens device 100 and the image pickup device main body 200 becomes possible. The information of the lens 300 is stored in the memory 120 (lens information storage unit), and the stored information is acquired by a command from the image processing unit 230 (information acquisition unit 230E; see FIG. 4). For example, the lens configuration, focal length, shooting angle of view, F value, aberration type and value of the lens 300 can be stored in the memory 120. These pieces of information may be measured after the lens 300 (lens device 100) is manufactured and stored in the memory 120, or the design values may be stored. Further, the information input by the operation of the operation unit 260 may be used.

The lens device 100 is attached to and detached from the image pickup apparatus main body 200 by the user's operation, so that lenses having different angles of view and focal lengths can be attached and photographed under desired conditions according to the purpose of photography, shooting conditions, and the like. it can. For example, instead of the lens device 100, lens devices 102, 104, 106 (see FIG. 2) having lenses 400, 500, 600 can be attached to the image pickup device main body 200. The lenses 400, 500, and 600 are also wide conversion lenses similar to the lens 300. In FIGS. 1 and 2, the configurations of the lenses 300, 400, 500, and 600 are simplified and displayed. The specific configuration of the lenses 300, 400, 500, 600 will be described later. Further, in FIGS. 1 and 2, the case where the lens devices 100, 102, 104, and 106 are attached to the image pickup apparatus main body 200 via the lens side mount 130 and the main body side mount 270 has been described, but the attachment to the image pickup apparatus main body 200 has been described. Is not limited to such an aspect. In addition to this, for example, a screw thread (lens mounting portion) provided on one of the lens devices 100, 102, 104, 106 and the image pickup device main body 200, and a screw groove (lens mounting portion) provided on the other side corresponding to the screw thread. ) And may be used. The lenses 300, 400, 500, 600 are attached to the subject side (object side) of the Fresnel zone plate 210.

<Structure of the main body of the imaging device>
The image pickup apparatus main body 200 includes a Fresnel zone plate 210 (Fresnel zone plate, coded aperture) and an image pickup element 220 (imaging element), and light from a subject is emitted from a lens 300 (or lenses 400, 500, 600) and a Fresnel zone. The image pickup element 220 acquires a projected image formed through the plate 210. The Fresnel zone plate 210 is arranged on the image pickup surface side of the image pickup element 220 in a state where the center coincides with the center of the image pickup element 220 and is parallel to the image pickup surface 220A (light receiving surface) of the image pickup element 220. The Fresnel zone plate 210 may be replaceable with respect to the image pickup apparatus main body 200. By properly using Fresnel zone plates with different characteristics (size, pitch, phase, distance from the image sensor, etc.), the characteristics (angle of view, depth (distance measurement accuracy), etc.) of the projected image to be acquired can be controlled and desired. The image of the characteristic can be reconstructed. In the following description, the Fresnel Zone Plate may be referred to as "FZP".

<Composition of Fresnel zone plate>
Part (a) of FIG. 3 is a diagram showing FZP1 which is an example of the Fresnel zone plate 210. In FZP1, the transmittance of incident light continuously changes according to the distance from the center. The region closer to white (transmission region) has higher light transmittance, and the region closer to black (light-shielding region) Low light transmittance. As a whole, the transmission region and the light-shielding region are alternately arranged concentrically, and these transmission region and the light-shielding region form a Fresnel zone plate. The interval between concentric circles becomes narrower from the center of FZP1 toward the periphery. Such a concentric pattern (change in local spatial frequency) is expressed by equations (2), (3), (7) and the like described later, and the fineness of the concentric circles in these equations is called "pitch". .. The pitch is determined by the above-mentioned value of β. When β is small, a coarse pattern is obtained, and when β is large, a fine pattern is obtained. A memory may be provided in the image pickup apparatus main body 200 to store pitch information (value of β), and the image processing unit 230 (information acquisition unit 230E) may acquire and use this information.

The optical axis L (see FIG. 1) of the Fresnel zone plate 210 is an axis that passes through the center of the FZP and the image sensor 220 and is perpendicular to the image pickup surface 220A of the FZP and the image sensor 220. Although the FZP is arranged close to the image sensor 220, it is preferable not to separate the FZP too much because the projected image is blurred due to the diffraction of light depending on the distance from the image sensor 220.

Part (b) of FIG. 3 is a diagram showing FZP2 which is another example of the Fresnel zone plate. FZP2 sets a threshold value for the transmittance for FZP1, and the region where the transmittance exceeds the threshold value is the transmittance region (white part) with 100% transmittance, and the region below the threshold value has the transmittance 0. It is a light-shielding region (black part) of%, and the transmittance changes discontinuously (in two stages of 0% or 100%) depending on the distance from the center. As a whole, the transmission region and the light-shielding region are alternately arranged concentrically, and these transmission region and the light-shielding region form a Fresnel zone plate. As described above, the "Fresnel zone plate" in the present invention includes an aspect such as FZP1 and an aspect such as FZP2, and correspondingly, the transmittance of the "Fresnel zone pattern" in the present invention is continuously changed. Includes patterns to be processed and patterns in which the transmittance changes discontinuously. A light-shielding portion (a region through which light does not pass, like the light-shielding region) is provided in the peripheral portion of the Fresnel zone plate as shown in FIG. 3 to prevent unnecessary light from entering the peripheral portion of the image sensor 220. You may.

<Structure of image sensor>
The image sensor 220 is an image sensor having a plurality of pixels composed of photoelectric conversion elements arranged in a two-dimensional direction. A microlens may be provided in each pixel to increase the light collection efficiency. Further, a color filter (for example, red, blue, and green) may be arranged in each pixel so that the color image can be reconstructed. In this case, when acquiring the projected image, interpolation processing according to the arrangement pattern of the color filter is performed in the same manner as the demosaic processing (also referred to as simultaneous processing) at the time of color image generation in a normal digital camera. As a result, signals of insufficient colors are generated in each pixel (light receiving element), and signals of each color (for example, red, blue, and green) are obtained in all pixels. Such processing can be performed by the image processing unit 230.

In addition to the Fresnel zone plate 210 and the image sensor 220 described above, the image pickup device main body 200 includes an image processing unit 230, a storage unit 240, a display unit 250, and an operation unit 260, and includes the Fresnel zone plate 210 and the image sensor. Image restoration of the subject based on the projected image acquired by 220 is performed.

<Structure of image processing unit>
FIG. 4 is a diagram showing a configuration of an image processing unit 230 (image restoration unit). The image processing unit 230 includes a projection image input unit 230A, a multiplication image generation unit 230B (image restoration unit), a Fourier transform unit 230C (image restoration unit), an aberration correction unit 230D (image restoration unit), and an information acquisition unit. It has a 230E (lens information acquisition unit) and a display control unit 230F. The projected image input unit 230A controls the image sensor 220 to acquire a projected image formed on the image sensor 220 by incident light from the subject on the FZP from the image sensor 220. The multiplication image generation unit 230B multiplies the projected image by a plurality of Fresnel zone patterns (first and second Fresnel zone patterns) having the same local spatial frequency and different phases of the local spatial frequencies. , Generates a complex image consisting of a real part image and an imaginary part image. The Fourier transform unit 230C reconstructs an image in the spatial region by performing a two-dimensional complex Fourier transform on the complex image. The aberration correction unit 230D corrects aberrations (astigmatism, spherical aberration, coma, distortion, axial chromatic aberration, magnification chromatic aberration, etc.) caused by the lens 300 or the lens 400 in an image in a spatial region. The information acquisition unit 230E acquires information on the lens 300 (for example, lens configuration, focal length, shooting angle of view, F value, type and value of aberration, etc.) stored in the memory 120 of the lens device 100. Further, the information acquisition unit 230E acquires information (pitch information) of the Fresnel zone plate 210 used for acquiring the projected image. The display control unit 230F controls the display of the projected image, the complex image, the reconstructed image, and the like on the display unit 250. The ROM 230G (non-temporary recording medium) records computer (processor) readable codes of various programs for operating the image pickup apparatus 10, such as a program for reconstructing an image.

The function of the image processing unit 230 described above can be realized by using various processors. Various processors include, for example, a CPU (Central Processing Unit), which is a general-purpose processor that executes software (programs) to realize various functions. In addition, the various processors described above include a programmable logic device (PLD), which is a processor whose circuit configuration can be changed after manufacturing, such as an FPGA (Field Programmable Gate Array). Further, the above-mentioned various processors also include a dedicated electric circuit, which is a processor having a circuit configuration specially designed for executing a specific process such as an ASIC (Application Specific Integrated Circuit).

The functions of each part may be realized by one processor, or may be realized by combining a plurality of processors. Further, a plurality of functions may be realized by one processor. As an example of configuring a plurality of functions with one processor, first, one processor is configured by a combination of one or more CPUs and software, as represented by a computer such as a client and a server, and this processor is configured. Is realized as a plurality of functions. Secondly, as typified by System On Chip (SoC), there is a form in which a processor that realizes the functions of the entire system with one IC (Integrated Circuit) chip is used. As described above, various functions are configured by using one or more of the above-mentioned various processors as a hardware structure.

Further, the hardware structure of these various processors is, more specifically, an electric circuit (circuitry) in which circuit elements such as semiconductor elements are combined.

When the above-mentioned processor (or electric circuit) executes software (program), the computer-readable code of the software to be executed (for example, software that acquires a projected image, acquires lens information, restores an image, etc.) is used. It is stored in a non-temporary recording medium such as ROM 230G, and the processor refers to the software. During processing using software, for example, RAM (Random Access Memory) is used as a temporary storage area, and data stored in EEPROM (Electronically Erasable and Programmable Read Only Memory) is referred to, for example. Note that in FIG. 4, the illustration of devices such as RAM and EEPROM is omitted.

<Structure of storage unit>
The storage unit 240 is composed of a non-temporary recording medium such as a CD (Compact Disk), a DVD (Digital Versatile Disk), a hard disk (Hard Disk), and various semiconductor memories, and stores the images and information shown in FIG. 5 in association with each other. .. The lens information 240A is information on the lens 300 acquired from the lens device 100 (for example, lens configuration, focal length, shooting angle of view, F value, type and value of aberration, etc.). The projected image 240B is a projected image acquired from the image sensor 220. The Fresnel zone plate information 240C is information on the local spatial frequency of the Fresnel zone plate 210 (including pitch information such as the value of β). The Fresnel zone plate information 240C may be information acquired from the image sensor 220 or information input via the operation unit 260. The Fresnel zone pattern information 240D is information indicating a Fresnel zone pattern, and it is preferable to record a plurality of Fresnel zone patterns having different phases of local spatial frequencies. The multiplied image 240E (multiplied image) is an image of the real part and an image of the imaginary part obtained by multiplying the projected image by the Frenel zone pattern (first and second Frenel zone patterns) indicated by the Frenel zone pattern information 240D. It is a complex image consisting of. The reconstructed image 240F is an image of a spatial region obtained by performing a two-dimensional complex Fourier transform on the multiplication image 240E.

<Structure of display unit and operation unit>
The display unit 250 includes a display device such as a liquid crystal display (not shown), displays a projected image, a multiplied image, a reconstructed image, etc., and is used for a UI (User Interface) at the time of inputting an instruction via the operation unit 260. It is also used for screen display of. The operation unit 260 is composed of devices such as a keyboard, a mouse, a button, and a switch (not shown), and the user uses these devices to give a projection image acquisition instruction, an image reconstruction instruction, a focusing distance condition, and local spatial frequency information ( Pitch, phase) etc. can be input. The display device of the display unit 250 may be configured by a touch panel and used as an operation unit 260 in addition to the image display.

<Specific configuration of lens>
<Example 1>
Part (a) of FIG. 6 is a diagram showing the arrangement of the lens 300, the Fresnel zone plate 210, and the image pickup surface 220A of the image pickup element 220. The lens 300 is a wide conversion lens composed of a front group 310 having a negative power (refractive power, the same applies hereinafter) and a rear group 320 having a positive power in order from the object side (subject side), and the lenses 302 and 304. , 306, 308. The Fresnel zone plate 210 is arranged at the position of the pupil (aperture position) of the lens 300.

<Example 2>
Part (b) of FIG. 6 is a diagram showing the arrangement of the lens 400, the Fresnel zone plate 210, and the image pickup surface 220A of the image pickup element 220. The lens 400 is a wide conversion lens composed of a front group 410 having a negative power and a rear group 420 having a positive power in order from the object side (subject side), and is composed of lenses 402, 404, 406, 408. To. The Fresnel zone plate 210 is arranged at the position of the pupil (aperture position) of the lens 400.

<Example 3>
Part (c) of FIG. 6 is a diagram showing the arrangement of the lens 500, the Fresnel zone plate 210, and the image pickup surface 220A of the image pickup element 220. The lens 500 is a wide conversion lens composed of a front group 510 having a negative power and a rear group 520 having a positive power in order from the object side (subject side), and is composed of lenses 502, 504, 506, 508. To. The Fresnel zone plate 210 is arranged at the position of the pupil (aperture position) of the lens 500.

<Example 4>
Part (d) of FIG. 6 is a diagram showing the arrangement of the lens 600, the Fresnel zone plate 210, and the image pickup surface 220A of the image pickup device 220. The lens 600 is a wide conversion lens composed of a front group 610 having a negative power and a rear group 620 having a positive power in order from the object side (subject side), and is composed of lenses 602,604,606,608. To. The Fresnel zone plate 210 is arranged at the position of the pupil (aperture position) of the lens 600.

Although the angles of view of the lenses 300, 400, 500, and 600 are fixed, the lens attached to the image pickup device main body in the image pickup device of the present invention may be a zoom lens having a variable angle of view (focal length).

<Optical path map>
Part (a) of FIG. 7 shows the optical paths of the axial luminous flux B1 and the maximum angle of view luminous flux B2 with respect to the lens 300 in a state where the ideal lens I1 (lens having zero aberration) is arranged at the position of the pupil of the lens 300. It is a figure which shows. In reality, since the Fresnel zone plate 210 is arranged at the position of the ideal lens I1 and the luminous flux travels as a wave surface, the optical path after the Fresnel zone plate 210 (on the imaging element 220 side) is not the same as the dotted line portion. For reference, the optical path when the ideal lens I1 is arranged is shown. The characteristics of the ideal lens I1 are f'= 1 mm, IH = 9.407, FNo. = 2.88, 2ω = 41.2 deg. The lens data of the ideal lens I1 is data when the distance between the pupil and the imaging surface 220A is 1 mm (that is, the distance between the ideal lens I2 and the imaging surface 220A is 1 mm) by standardization. The lens data of the ideal lenses I2 to I4 shown below are the same as those of the ideal lens I1.

Similarly, the portion (b) in FIG. 7 shows the axial luminous flux B3 and the maximum angle of view light flux B4 with respect to the lens 400 in a state where the ideal lens I2 (lens having zero aberration) is arranged at the position of the pupil of the lens 400. It is a figure which shows the optical path of. In reality, since the Fresnel zone plate 210 is arranged at the position of the ideal lens I2 and the luminous flux travels as a wave surface, the optical path after the Fresnel zone plate 210 (on the image pickup element 220 side) is not the same as the dotted line portion. For reference, the optical path when the ideal lens I2 is arranged is shown.

Similarly, the portion (c) of FIG. 7 shows the axial luminous flux B5 and the maximum angle of view light flux B6 with respect to the lens 500 in a state where the ideal lens I3 (lens having zero aberration) is arranged at the position of the pupil of the lens 500. It is a figure which shows the optical path of. In reality, since the Fresnel zone plate 210 is arranged at the position of the ideal lens I3 and the luminous flux travels as a wave surface, the optical path after the Fresnel zone plate 210 (on the image pickup element 220 side) is not the same as the dotted line portion. For reference, the optical path when the ideal lens I3 is arranged is shown.

Similarly, the portion (d) in FIG. 7 shows the axial luminous flux B7 and the maximum angle of view light flux B8 with respect to the lens 600 in a state where the ideal lens I4 (lens having zero aberration) is arranged at the position of the pupil of the lens 600. It is a figure which shows the optical path of. In reality, since the Fresnel zone plate 210 is arranged at the position of the ideal lens I4 and the luminous flux travels as a wave surface, the optical path after the Fresnel zone plate 210 (on the imaging element 220 side) is not the same as the dotted line portion. For reference, the optical path when the ideal lens I4 is arranged is shown.

<Lens data>
The portions (a) to (c) of FIG. 8 are tables showing lens data of lenses 300, 400, and 500. In the table, the surface numbered with "*" indicates that it is an aspherical surface. Similarly, FIG. 9 is a table showing lens data of the lens 600. The lens data in FIGS. 8 and 9 is data when the distance between the pupil and the imaging surface 220A is 1 mm (that is, the distance between the Fresnel zone plate 210 and the imaging surface 220A is 1 mm) by standardization. When the interval becomes k times due to changing the focal length or the like, the radius of curvature and the surface interval also increase k times.

FIG. 10 is a table showing the aspherical coefficients of the lens 300. When the center is the lens surface and the optical axis is the x-axis, the aspherical shape of the lens surface is expressed by the following equation (1). Note that c is the reciprocal of the paraxial radius of curvature (paraxial curvature), hi is the height from the optical axis, κ is the conical multiplier, and Ai is the aspherical coefficient.

<Vertical aberration diagram>
The portions (a) to (d) of FIG. 11 are diagrams showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the lens 300, respectively. Similarly, portions (a) to (d) of FIG. 12 are diagrams showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the lens 400, respectively. Similarly, portions (a) to (d) of FIG. 13 are diagrams showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the lens 500, respectively. Similarly, portions (a) to (d) of FIG. 14 are diagrams showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the lens 600, respectively.

<Specifications of Examples>
FIG. 15 is a table showing specifications of Examples 1 to 4. Due to the above configuration, in Example 1 (when the lens 300 is attached), the angle of view is changed (widened to 60.0 deg) with respect to the original optical system (angle of view is 20.6 deg). I understand. Similarly, in Example 2 (when the lens 400 is attached), the angle of view is changed (widen to 80.0 deg) with respect to the original optical system (angle of view is 46.5 deg). Similarly, in Example 3 (when the lens 500 is attached), the angle of view is changed (widened to 60.0 deg) with respect to the original optical system (angle of view is 24.5 deg). Similarly, in Example 4 (when the lens 600 is attached), the angle of view is changed (widened to 60.0 deg) with respect to the original optical system (angle of view is 20.2 deg). The "original optical system" in Examples 1 to 4 is an optical system using a coded aperture such as the Fresnel zone plate 210 (focal length is 1.0 mm).

<Peripheral Illumination>
FIG. 16 is a table showing conditional expressions for calculating peripheral illumination for Examples 1 to 4, and the meanings of the parameters in the table are as follows. Each example satisfies the numerical range in each aspect of the present invention. The definitions of Cs, Ct, Mt, and Ms are shown in the parts (a), (b), and (c) of FIG. 17 (shown in Example 1 as a representative example). The portion (b) of FIG. 17 is a diagram showing a plane P1, and the portion (c) of FIG. 17 is a diagram showing a plane P2. The planes P1 and P2 are planes perpendicular to the main ray L1 of the axial luminous flux B1 and the main ray L2 of the luminous flux B2 having the maximum angle of view, respectively.

Cs: Length in the sagittal direction (tangential direction) of the axial light beam incident on the surface closest to the object Ms: Length in the sagittal direction of the light beam with the maximum angle of view incident on the surface closest to the object DA: Wide conversion lens ( Maximum air spacing in lenses 300, 400, 500, 600) Ff: Focal length of the lens group on the object side of DA Ct: Length of the axial light beam incident on the surface closest to the object in the tangential direction (radiation direction) Mt: The length of the light beam with the maximum angle of view incident on the surface closest to the object in the tangential direction when projected onto the surface perpendicular to the main ray WCTL: The first to final surfaces of the wide conversion lens. Length up to WCf: Focal length of wide conversion lens Dist: Optical distortion when the wide conversion lens is attached to the ideal lens [%]
FIG. 18 shows the peripheral illumination ratio (indicated by the fourth power of (cosγ) with respect to the half angle of view γ, where 100% is on the optical axis) for (wide conversion lens of Examples 1 to 4 + ideal lens). It is a table, and FIG. 19 is a graph showing a peripheral illumination ratio for an ideal lens and (wide conversion lens + ideal lens of Examples 1 to 4). When the half-angle of view γ is 30 deg, the peripheral illumination ratio of the ideal lens is about 56%, and when it is 40 deg, it is about 34%, but in the case of (wide conversion lens of Examples 1 to 4 + ideal lens). The peripheral illumination ratio is about 78% to 99%, and it can be seen that the peripheral illumination ratio is improved (not decreased).

<Image reconstruction>
Reconstruction of an image by the image pickup apparatus 10 having the above-described configuration will be described. FIG. 20 is a flowchart showing an image reconstruction process.

<Input of projected image>
In step S100, the image processing unit 230 (projected image input unit 230A) acquires the projected image of the subject from the image sensor 220. The projected image to be acquired is a projected image formed on the image pickup device 220 by incident light from the subject on the Fresnel zone plate 210.

<Local spatial frequency information>
In step S110, the image processing unit 230 (information acquisition unit 230E) inputs information on the local spatial frequency of the Fresnel zone plate 210 (pitch of the Fresnel zone plate 210) used for acquiring the projected image. This information may be input from a memory (not shown) or may be input according to the user's operation on the operation unit 260. Further, the information acquisition unit 230E may analyze and input the projection image acquired in step S100. Since the pitch is determined by the value of β (see equations (2) to (4), (7) and the like described later), the value of β may be specifically input. When a known subject (for example, a point light source at an infinity distance) is photographed, the pitch (value of β) can be acquired by analyzing the photographed image. Further, the image may be reconstructed repeatedly while changing the pitch (value of β) to obtain a value at which a clear image can be obtained.

<Generation of complex image>
In step S120, the image processing unit 230 (multiplication image generation unit 230B) multiplies the projected image by the first and second Fresnel zone patterns to generate a complex image composed of a real part image and an imaginary part image. To do. As the Fresnel zone pattern to be multiplied in step S120, a pattern selected from the patterns (Fresnel zone pattern information 240D) stored in the storage unit 240 according to the pitch (value of β) input in step S110 can be used. .. Further, it is also possible to use a pattern in which the pattern stored in the storage unit 240 is changed (may be enlarged or reduced as necessary) according to the pitch (value of β). The image processing unit 230 (multiplication image generation unit 230B) stores the generated complex image as the multiplication image 240E in the storage unit 240.

<Phase of Fresnel zone pattern>
The first Fresnel zone pattern used in image restoration can be, for example, the pattern shown in part (a) of FIG. 21 (phase at the center is 0 deg), and by multiplying this by the projected image, the image of the real part is obtained. Is obtained. Further, the second Fresnel zone pattern can be, for example, the pattern shown in the portion (b) of FIG. 21 (the pitch is the same as that of the first Fresnel zone pattern and the phase is 90 deg out of phase), and this is used as a projection image. An image of the imaginary part is obtained by multiplying. As described above for the formula (7) and the like, the phase shift of the first and second Fresnel zone patterns is preferably 90 deg, but if the phase shift is positively or negatively in the range of 70 deg or more and 110 deg or less, a clear image is reconstructed. can do. The phase of the local spatial frequency of the first Fresnel zone pattern or the second Fresnel zone pattern may be the same as the phase of the Fresnel zone plate 210.

When using the Fresnel zone pattern, data of a plurality of Fresnel zone patterns having different phases can be stored in the storage unit 240 as Fresnel zone pattern information 240D, and a desired pattern can be selected and used. Further, the image processing unit 230 (multiplication image generation unit 230B) may generate a desired pattern based on the pitch and phase information. Since such a Fresnel zone pattern is stored in the storage unit 240 as Fresnel zone pattern information 240D which is electronic data, it is possible to quickly and easily select and generate a desired pattern. In addition, by holding a plate (board) corresponding to a plurality of patterns as a tangible object, the size of the device is increased, the manufacturing cost is increased, and the characteristics are varied among the multiple patterns (variations during manufacturing, changes over time, and changes in temperature). There is no problem such as deterioration of image quality due to (including).

<Fresnel zone pattern expansion rate>
When the subject (light source) exists at an infinity distance, parallel light is incident on the Fresnel zone plate 210, and the projected image formed on the image pickup element 220 has the same size as the Fresnel zone plate 210, but the subject is finite. When it exists at a distance, light with a spread is incident, and the closer the distance, the larger the projected image. Therefore, by using a pattern having a different enlargement ratio depending on the subject distance to be focused as the first and second Fresnel zone patterns, it is possible to obtain an image focused at a desired distance. For example, a plurality of patterns according to the subject distance can be stored in the storage unit 240 as Fresnel zone pattern information 240D, and this can be read out and used. Further, one Fresnel zone pattern may be stored as a reference pattern and enlarged at different enlargement ratios according to the subject distance. In this case, a pattern corresponding to the infinite subject distance and having the same size as the Fresnel zone plate can be used as the reference pattern. FIG. 22 is a diagram showing how the enlargement ratio of the Fresnel zone pattern differs depending on the subject distance.

It should be noted that the generation of the complex image (step S120) and the reconstruction of the image (step S130) are repeated while changing the enlargement ratio, and the focusing evaluation value of the reconstructed image (for example, the luminance signal in the focus evaluation region set in the image). A clear image may be obtained by maximizing (integral value of).

As described above, the image pickup apparatus 10 according to the first embodiment can perform refocusing using the Fresnel zone plate 210 (coded aperture) and the Fresnel zone pattern.

<Image reconstruction>
In step S130, the image processing unit 230 (Fourier transform unit 230C) reconstructs the image of the subject (image in the spatial region) by performing a two-dimensional complex Fourier transform on the complex image (described later). Further, the image processing unit 230 (aberration correction unit 230D) has an aberration (non-point) caused by a lens (lens 300, lens 400, etc.) mounted on the image pickup apparatus main body 200 in the reconstructed image (image of the spatial region). Aberration, spherical aberration, coma aberration, distortion, axial chromatic aberration, chromatic aberration of magnification, etc.) are corrected. The correction is performed based on the lens information 240A acquired from the memory 120. Further, the aberration correction may be performed before the image is reconstructed, or may be performed after the reconstructed image. When correcting aberrations before reconstruction, for example, the shape and / or magnitude of the Fresnel zone pattern (coded aperture) to be multiplied by the projected image is changed according to the type and / or amount of aberrations to be corrected. be able to. On the other hand, when correcting aberrations after reconstruction, for example, an image in which different filters (filters for point image restoration, etc.) are applied depending on conditions such as the type and / or degree of aberrations to be corrected and the position in the image. It can be done by processing. However, the correction of aberrations in the present invention is not limited to such an aspect. The image processing unit 230 (display control unit 230F) displays the reconstructed image on the display unit 250 (step S140). Further, the image processing unit 230 (Fourier transform unit 230C) stores the reconstructed image as the reconstructed image 240F in the storage unit 240.

<Details of image restoration>
The details of the image restoration in the first embodiment will be described in more detail. The pattern I (r) of the coded aperture (Fresnel zone plate) is expressed by the equation (2).

The larger the value of I (r), the higher the transmittance of light in the predetermined wavelength band. r is the radius of the Fresnel zone plate, and β (> 0) is a constant that determines the fineness (pitch) of the pattern. Hereinafter, in order to avoid a negative value, I2 (r) with an offset and within the range of 0 to 1 as in the equation (3) will be considered.

It is assumed that the coded aperture (Fresnel zone plate) is arranged at a distance d from the sensor surface. At this time, assuming that light (parallel light) is incident from a point light source at an infinity distance at an incident angle θ, the shadow of the coding aperture (Fresnel zone plate) moves in parallel by Δr (= d × tan θ) and the sensor It is reflected on the top. The translated shadow S (r) is expressed by Eq. (4).

I2 (r) and S (r) are originally two-dimensional images and are two-variable functions, but for the sake of simplicity, we focus only on the one-dimensional images on the cross section cut by the plane including the center and the incident light source. Think. However, it can be easily extended in the case of two dimensions by calculating as the following equation (5).

The captured shadow image (projected image) is image-restored (reconstructed) on a computer and output. In the image restoration process, the shadow image is multiplied by the Fresnel zone aperture image (Fresnel zone pattern) that is not misaligned. Regarding this function to be internally multiplied, here we consider the case of two functions expressed by the following equations (6) and (7). The imaginary unit is j.

Mr (r) is the same real-valued function as I (r), but with the offset (DC component) removed. The image reconstruction in the prior art (Non-Patent Documents 1 and 2 and Patent Document 1 described above) corresponds to the case of multiplying the projected image of the real number aperture by the Fresnel zone pattern represented by the real number function Mr (r). To do. Since Mc (r) is a complex number function and Mc (r) = cosβr ² + j × sinβr ² = cosβr ² −j × cos (βr ² + π / 2), the phases of the real part and the imaginary part are (π / 2). That is, it corresponds to the Fresnel zone pattern shifted by 90 deg. The real part (cosβr ² ) of Mc (r) is the same as Mr (r). In the first embodiment, the projected image is multiplied by two Fresnel zone patterns (first and second Fresnel zone patterns) corresponding to the real part and the imaginary part of the complex number function and having different phases. A complex image consisting of an image of a part and an image of an imaginary part is generated.

The image after internal multiplication (multiplication image) is expressed by the following equations (8) and (9) in each case.

The first term is a component that can be removed by offset correction or the like for each of the multiplied images Fr (r) and Fc (r) when Mr (r) and Mc (r) are used for the internal multiplication image. The second term is the moiré interference fringes from which the "difference frequency" between the superimposed Fresnel zone openings (corresponding to cos (α−φ) when the two openings are represented by cosα and cosφ) is extracted. Since this coincides with the basis of the Fourier transform, it is transformed into a delta function by applying the Fourier transform to become a "point", which is a component that contributes to imaging. The third term corresponds to the "sum frequency" (corresponding to cos (α + φ)), which is a component that does not contribute to imaging even after Fourier transform and acts as noise.

The offset correction is appropriately applied to Fr (r) and Fc (r), respectively, and the images in the state where the first term is erased are designated as Fr2 (r) and Fc2 (r). When the Fourier transform is actually applied to these, the Fourier transforms of Fr (r) and Fc (r) are expressed by the equations (10) and (11) as fr (k) and fc (k).

Here, ξ (k, β, Δr) is a real polynomial. A restored image can be obtained by taking the absolute value of a complex number with respect to these, but in the case of fr (k) (in the case of the prior art), the first term and the second term generate two points symmetrical to the origin. , The restored image is point-symmetrically overlapped. On the other hand, in the case of fc (k) (in the case of the first embodiment), such a problem does not occur and the image is normally reconstructed. What they have in common is that the third term of fr (r) and the second term of fc (r) act as noise, and because of this term, the MTF (Modulation Transfer Function) is 100%. Cannot be (this means that the MTF will not be 100% in the absence of sensor noise). However, since this noise becomes smaller as the β value is increased, it is possible to reduce the influence by increasing the β value (making a fine pattern).

Regarding the first term of fc (k) (in the case of the first embodiment), the phase rotates depending on the incident angle of light, but if the absolute value of the complex number is taken, infinite light It can be confirmed that the image is formed in the delta function (point) corresponding to the arrival of. Since all the operations from the angle spectrum of the incident light to the imaged image are linear, superposition is established, which can explain the image formation.

When calculated for the two-dimensional case, the peripheral illumination is (cosγ) ^ 4, and the distortion is 2 × β × d × tanγ (γ is a half angle of view).

<Effect of the first embodiment>
As described above, according to the wide conversion lenses 300, 400, 500, 600 (lens devices 100, 102, 104, 106) according to the first embodiment, images having different angles of view when mounted on an imaging device can be displayed. It can be obtained with good image quality. Further, the image pickup apparatus 10 according to the first embodiment is provided with the wide conversion lenses (lenses 300, 400, 500, 600) according to the first embodiment, so that images having different angles of view can be imaged with good image quality (peripheral illumination ratio). Can be obtained with high and low optical distortion). In addition, the angle of view can be changed while maintaining the refocus function of the coded aperture (Fresnel zone plate 210).

<Other aspects>
In the first embodiment described above, the projected image is multiplied by the first and second Fresnel zone patterns to generate a complex image, and the complex image is subjected to complex Fourier transform to reconstruct the image in the spatial region. However, the reconstruction of the image in the image pickup apparatus of the present invention is not limited to the mode in which the complex image is used. As described above for equations (6), (8), (10), etc., the projected image is multiplied by a real number function such as Mr (r) to obtain a multiplied image, and this multiplied image is Fourier transformed to obtain an image. May be reconstructed. In this case, the subject images may overlap in the restored image, but this can be dealt with by cutting out the reconstructed image in half and displaying it. Further, even in the case of multiplying by a real number function, an image focused at a desired distance can be obtained by using a Fresnel zone pattern having a different magnification depending on the subject distance to be focused.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

10 Imaging device 100 Lens device 102 Lens device 104 Lens device 106 Lens device 120 Memory 130 Lens side mount 132 Lens side terminal 200 Fresnel zone plate 220 Imaging element 220A Imaging surface 230 Image processing unit 230A Projection image input unit 230B Multiplication Image generation unit 230C Fourier conversion unit 230D Aberration correction unit 230E Information acquisition unit 230F Display control unit 230G ROM
240 Storage unit 240A Lens information 240B Projection image 240C Frenel zone plate information 240D Frenel zone pattern information 240E Multiply image 240F Reconstructed image 250 Display unit 260 Operation unit 270 Main unit side terminal 300 Main unit side terminal 300 Lens 302 Lens 304 Lens 306 Lens 308 Lens 310 Front group 320 Rear group 400 Lens 402 Lens 404 Lens 406 Lens 408 Lens 410 Front group 420 Rear group 500 Lens 502 Lens 504 Lens 506 Lens 508 Lens 510 Front group 520 Rear group 600 Lens 602 Lens 604 Lens 606 Lens 608 Lens 610 Front Group 620 Rear group B1 On-axis light beam B2 Light beam B3 On-axis light beam B4 Light beam B5 On-axis light beam B6 Light beam B7 On-axis light beam B8 Light beam Fr Multiplied image FZP1 Frenel zone plate FZP2 Frenel zone plate I Pattern I1 Ideal lens I2 Ideal lens Lens I4 Ideal lens L Optical axis L1 Principal ray L2 Principal ray Mr Real number Function P1 Plane P2 Plane S Shadow S100 to S140 Steps of reconstruction processing d Distance γ Half angle θ Incident angle

Claims (11)

A wide conversion lens mounted on the object side of an image pickup apparatus and satisfying the following conditional expressions (1) and (2).
1.1 <Ms / Cs (1)
0.3 << Ff / DA | <2.0 (2)
However, Cs is the length in the sagittal direction of the axial light beam incident on the surface of the wide conversion lens on the most object side, and Ms is the length of the light beam having the maximum angle of view incident on the surface of the wide conversion lens on the most object side. The length in the sagittal direction, DA is the maximum air spacing in the wide conversion lens, and Ff is the focal length of the lens group on the object side of the position where the maximum air spacing exists. The wide conversion lens according to claim 1, which satisfies the following conditional expression (3).
2.2 <Mt / Ct (3)
However, Ct is the length in the tangential direction of the axial light beam incident on the surface of the wide conversion lens on the most object side, and Mt is the light beam having the maximum angle of view incident on the surface of the wide conversion lens on the most object side. The length in the tangential direction of is projected onto the plane perpendicular to the main ray. The wide conversion lens according to claim 1 or 2, which satisfies the following conditional expression (4).
| WCTL / WCf | <0.1 (4)
However, WCTL is the length from the first surface, which is the surface closest to the object side of the wide conversion lens, to the final surface, which is the surface farthest from the object side, and WCf is the focal length of the wide conversion lens. The wide conversion lens according to any one of claims 1 to 3, which satisfies the following conditional expression (5).
| Dist | <10 (5)
However, Dist is the optical distortion [%] when the wide conversion lens is attached to the ideal lens. The wide conversion lens according to any one of claims 1 to 4, which is composed of a front group having a negative refractive power and a rear group having a positive refractive power in order from the object side. The wide conversion lens according to any one of claims 1 to 5.
The image pickup device main body to which the wide conversion lens is mounted and
An imaging device comprising. The image pickup device main body includes a coded aperture, an image pickup element that outputs a signal of a projected image formed by the coded aperture, and an image restoration unit that reconstructs an image in a spatial region based on the signal. And
The imaging device according to claim 6, wherein the wide conversion lens is mounted on the object side of the coded aperture, and the projected image is formed on the image sensor by the wide conversion lens and the coded aperture. The imaging device according to claim 7, wherein the image restoration unit corrects aberrations caused by the wide conversion lens in an image in the spatial region. A lens information acquisition unit for acquiring information on the wide conversion lens is provided.
The image pickup apparatus according to claim 8, wherein the image restoration unit corrects the aberration based on the acquired information. The coded aperture is a Fresnel zone plate.
The image restoration unit multiplies the projected image formed on the image sensor by the wide conversion lens and the Fresnel zone plate by the Fresnel zone pattern corresponding to the Fresnel zone plate to generate a multiplied image, and the multiplication is performed. The image pickup apparatus according to any one of claims 7 to 9, wherein the image is Fourier transformed to reconstruct the image in the spatial region. The imaging device according to any one of claims 7 to 10, wherein the wide conversion lens is an interchangeable lens attached to and detached from the imaging device.

Images