WO2019131191A1

WO2019131191A1 - Wide conversion lens and image capture device

Info

Publication number: WO2019131191A1
Application number: PCT/JP2018/045990
Authority: WO
Inventors: 大樹小松; 慶延岸根
Original assignee: 富士フイルム株式会社
Priority date: 2017-12-26
Filing date: 2018-12-13
Publication date: 2019-07-04
Also published as: JP2021043230A

Abstract

The purpose of the present invention is to provide: a wide conversion lens with which images having differing angles of view are obtained with good image quality when the wide conversion lens is mounted on an image capture device; and an image capture device comprising such a wide conversion lens. A wide conversion lens according to a first embodiment of the present invention is mounted on the object side of the image capture device, and satisfies conditions (1) and (2). 1.1 < Ms/Cs (1) 0.3 < |Ff/DA| < 2.0 (2) Cs is the length in the sagittal direction of an on-axis luminous flux incident on the surface of the wide conversion lens closest to the object; Ms is the length in the sagittal direction of the luminous flux of the maximum angle of view incident on the surface of the wide conversion lens closest to the object; DA is the maximum air gap of the wide conversion lens; and Ff is the focal distance of the lens group on the objective side of the position at which the maximum air gap is present.

Description

Wide conversion lens and imaging device

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

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

On the other hand, in the field of imaging devices, in recent years, a technology for acquiring an image of a subject without a lens has been developed. For example, in Non-Patent Document 1 below, a Fresnel zone plate is disposed in proximity to an imaging device, and a projected image formed on the imaging device by light from an object is superimposed on a projection pattern corresponding to the Fresnel zone plate. By subjecting the moiré fringes to Fourier transform, it is possible to obtain an image of the subject without a lens. The technical report of Non-Patent Document 2 is made on the technology of Non-Patent Document 1. Moreover, the lensless imaging technique which uses a Fresnel zone plate for a mask pattern like

nonpatent literature

1 and 2 is known (refer to patent documents 3). In Patent Document 1, an image of a subject is reconstructed by Fourier-transforming a moiré fringe formed by incidence of light from the subject on two grating patterns (Fresnel zone plate) arranged to face each other. .

JP 2012-93751 A JP, 2014-56054, A WO 2016/203573

Conventional wide conversion lenses can not obtain images with different angles of view with good image quality when mounted on an imaging device. For example, in the wide-angle relay lens described in Patent Document 1, according to the study of the inventors of the present invention, although the peripheral light amount ratio is improved, the optical distortion is very large at about 44%. It will not be possible. Further, in the wide converter lens described in Patent Document 2, although the off-axis light beam incident on the lens is thicker than the on-axis light beam, the peripheral light amount ratio is low. In general, the peripheral light amount ratio of the lens decreases toward the periphery of the screen. Theoretically, the peripheral light amount ratio depends on the angle of view, and there is a relation of RI = (cos γ) ⁴ . Here, RI (Relative Illumination) is set as the peripheral light ratio, and γ is set as a half angle of view. For example, in the case of a half angle of view of 30 degrees, RI is about 56.25%.

On the other hand, refocusing is possible with the techniques described in

Non-Patent Documents

1 and 2 and Patent Document 3 described above, and the focal distance is f = 2 × β × d. Here, refocusing is to refocus the image to a desired focusing distance by image reconstruction, β represents the pitch of the Fresnel zone plate, and d represents the distance between the image sensor and the Fresnel zone plate. Represent. In the case of changing the angle of view (focal length) in the imaging apparatus having such a configuration, the pitch and / or the position of the Fresnel zone plate is changed, which brings about the demerit described below.

For example, when widening the angle (shortening the focal length), it is necessary to "(1) roughen the pitch of the Fresnel zone plate" or "(2) move the Fresnel zone plate closer to the sensor (decrease the value of d)" is there. In the case of (1), the field angle resolution (resolution) is lowered due to the decrease in the number of stripes which is a pattern constituted by the light transmitting region and the light shielding region in the Fresnel zone plate, and in the case of (2) The closer the Fresnel zone plate is to the image sensor, the higher is the demand for the positional accuracy of the Fresnel zone plate and the image sensor. On the other hand, in the case of telephoto (to increase the focal length), it is necessary to (3) make the pitch of the Fresnel zone plate finer or (4) release the Fresnel zone plate from the image sensor (increase the value of d). There is. In the case of (3), narrowing of the pitch is required, which increases the manufacturing difficulty. In the case of (4), the light diffraction causes the image of the Fresnel zone plate to be blurred on the image sensor and the image quality of the reconstructed image is deteriorated. Do. Considering the demerit of changing the angle of view due to the change of β and d, it is conceivable to widen the angle of view by mounting a wide conversion lens in front of the coding aperture (object side). However, in the conventional wide conversion lenses such as

Patent Documents

1 and 2, as in the case of a general imaging apparatus using a lens, images with different angle of view are excellent when mounted on an imaging apparatus having a coded aperture. It was difficult to obtain with good image quality.

As described above, in the related art, when a wide conversion lens is attached to an imaging device, it is difficult to obtain an image with different angle of view with good image quality.

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

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

1.1 <Ms / Cs (1)
0.3 <| Ff / DA | <2.0 (2)
Where Cs is the length in the sagittal direction of the axial light beam incident on the surface closest to the object side of the wide conversion lens, and Ms is the sagittal direction of the light beam with the largest angle of view incident on the surface closest to the object side in the wide conversion lens Where D.sub.A is the maximum air separation in the wide conversion lens, and F.sub.f is the focal length of the lens group on the object side of the position where the maximum air separation exists.

If Ms / Cs ≦ 1.1, it becomes difficult to increase the peripheral light amount, and if 2.0 ≦ Ms / Cs, the pupil aberration becomes too large, and distortion and astigmatism increase. Further, if | Ff / DA | ≦ 0.3, the power of the front group becomes too strong, negative distortion may occur largely, or the overall length becomes long, and miniaturization can not be achieved. On the other hand, if Ms / Cs and | Ff / DA | are in the range defined in the first aspect, the peripheral light amount ratio can be made high and the optical distortion can be made small. As described above, the wide conversion lens according to the first aspect can obtain an image with different angle of view with good image quality when mounted on an imaging device.

In the first embodiment, it is more preferable that Ms / Cs <2.0 and 0.5 <│Ff / DA│ <1.5. By satisfying these conditional expressions, the peripheral light amount ratio is further improved, and the distortion is further reduced.

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

2.2 <Mt / Ct (3)
Where Ct is the length in the tangential direction of the axial light beam incident on the surface closest to the object side of the wide conversion lens, and Mt is the tangent of the light beam with the largest angle of view incident on the surface closest to the object side of the wide conversion lens. It is the length obtained by projecting the length in the principal direction on a plane perpendicular to the chief ray. If Mt / Ct ≦ 2.2, it will be difficult to cite the peripheral light ratio, but if the characteristic of the wide conversion lens is in the range specified in the second aspect, the peripheral light ratio is increased and the optical distortion is reduced. be able to. In the second aspect, preferably, Mt / Ct <3.0. If 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 furthest to the object side, and WCf is the focal length of the wide conversion lens. Is out of the range specified in the third aspect, the afocal system collapses, the shift from the back focus of the mounted optical system becomes large, and the focus shifts when the user uses it. It is preferable that | WCTL / WCf | is within the range defined 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 an optical distortion when the wide conversion lens is attached to the ideal lens. Since about 10% distortion can be recognized in object recognition in a sensing application or the like, an optical distortion of up to 10% is acceptable. In the fourth aspect, it is more preferable that | Dist | <5%. This is because distortion is further reduced.

In any one of the first to fourth aspects, the wide conversion lens according to the fifth aspect includes, in order from the object side, a front group of negative refractive power and a rear group of positive refractive power. By adopting the configuration of the fifth aspect, it is easy to achieve a wide angle.

In order to achieve the above-described object, the imaging device according to the sixth aspect is equipped with the wide conversion lens according to any one of the first to fifth aspects, and a wide conversion lens, a coded aperture, and the code And an imaging device main body having an imaging device for outputting a signal of a projected image formed by the aperture, and an image restoration unit for reconstructing an image of a spatial region based on the signal. According to the sixth aspect, with the wide conversion lens according to any one of the first to fifth aspects, images with different angle of view can be obtained with good image quality (improved peripheral light amount ratio and small distortion) be able to.

In an imaging device according to a seventh aspect, in the sixth aspect, the imaging device main body includes a coded aperture, an imaging element for outputting a signal of a projected image formed by the coded aperture, and a spatial region based on the signal. The wide conversion lens is mounted on the object side of the coding aperture, and a projection image is formed on the imaging device by the wide conversion lens and the coding aperture. An imaging apparatus using a coded aperture has a refocusing function, but if it is attempted to change the angle of view (focal length) by changing β and d, there are disadvantages such as image quality deterioration and manufacturing difficulty increase as described above. In addition, the peripheral light amount ratio decreases in accordance with the cosine fourth law (also referred to as “cos fourth 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. An image of image quality can be obtained.

In an imaging device according to an eighth aspect, in the seventh aspect, the image restoration unit corrects an aberration caused by the wide conversion lens in the image of the spatial region. According to the eighth aspect, since aberrations (such as astigmatism, spherical aberration, coma, distortion, axial chromatic aberration, lateral chromatic aberration, etc.) caused by the lens are corrected, it is possible to obtain an image of good image quality. . Aberration correction may be performed before or after the image is reconstructed. In the case of correcting the aberration before the reconstruction, for example, the shape and / or the size of the coded aperture by which the projection image is multiplied can be performed according to the type and / or the amount of the aberration to be corrected. On the other hand, when correcting the aberration after the reconstruction, for example, an image such as applying different filters (such as a filter for point image restoration) depending on conditions such as the type and / or degree of aberration to be corrected and the position in the image. It can be done by processing. However, the correction of the aberration in the present invention is not limited to such an aspect.

An imaging apparatus according to a ninth aspect of the present invention is, in the eighth aspect, provided with a lens information acquisition unit that acquires information of a wide conversion lens, and the image restoration unit corrects an aberration 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 lens information storage unit for storing information of the lens may be provided in the wide conversion lens, and the lens information acquisition unit may acquire information from the lens information storage unit. Such a lens information storage unit can be configured using a non-temporary recording medium.

In the imaging device according to the tenth aspect, in any one of the seventh to ninth aspects, the coding aperture is a Fresnel zone plate, and the image restoration unit is formed on the imaging element by the wide conversion lens and the Fresnel zone plate The projected image is multiplied by the Fresnel zone pattern corresponding to the Fresnel zone plate to generate a multiplied image, and the multiplied image is subjected to Fourier transform to reconstruct an image in the spatial domain. In the tenth aspect, it is preferable to generate a multiplied image using Fresnel zone patterns having different enlargement ratios according to the subject distance to be focused. Thereby, an image focused at a desired subject distance can be obtained.

In the tenth aspect, it is preferable to perform image reconstruction by two-dimensional complex Fourier transform of a complex image. This is because it is possible to obtain a high quality image with no overlapping of subject images. Specifically, the Fresnel zone pattern has a first Fresnel zone pattern and the first Fresnel zone pattern has the same local spatial frequency in each region, and the phase of the local spatial frequency is different. And the image restoration unit multiplies the projection image with the first Fresnel zone pattern and the second Fresnel zone pattern, respectively, to form a real image and an imaginary image as a multiplication image. Preferably, a complex image is generated, and the complex image is subjected to two-dimensional complex Fourier transformation to reconstruct an image in the spatial domain.

An imaging device according to an eleventh aspect of the present invention is the interchangeable lens that is attached to and removed from the imaging device in any one of the seventh to tenth aspects. According to the eleventh aspect, it is possible to attach a lens with a different angle of view and focal length according to the purpose of imaging and imaging conditions, and to capture under desired conditions.

As described above, according to the wide conversion lens of the present invention, it is possible to obtain an image with different angle of view with good image quality when mounted on an imaging device. Further, according to the imaging device of the present invention, an image with different angle of view can be obtained with good image quality by the wide conversion lens.

FIG. 1 is a block diagram showing the configuration of an imaging apparatus according to the first embodiment. FIG. 2 is a view showing another example of the configuration of the lens apparatus. 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 lens configurations of Examples 1 to 4. FIG. 7 is a view showing the optical paths 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 Example 4. FIG. 10 is a diagram showing the aspheric coefficients of the first, second, and fourth embodiments. FIG. 11 is a diagram showing the longitudinal aberration of Example 1. FIG. 12 is a diagram showing the longitudinal aberration of Example 2. FIG. 13 is a diagram showing the longitudinal aberration of Example 3. FIG. 14 is a diagram showing the longitudinal aberration of Example 4. FIG. 15 is a table showing the specifications of the first to fourth embodiments. FIG. 16 is a table showing peripheral light amount calculation conditions of the first to fourth embodiments. FIG. 17 is a diagram showing the definition of parameters. FIG. 18 is a table showing peripheral light amounts of Examples 1 to 4. FIG. 19 is a graph showing the peripheral lens ratio of the ideal lens and Examples 1 to 4. FIG. 20 is a flowchart showing the process of image reconstruction. FIG. 21 is a diagram showing an example of Fresnel zone plates having different phases. FIG. 22 is a view showing a Fresnel zone pattern of an enlargement factor according to the focusing distance.

Hereinafter, embodiments for implementing a wide conversion lens and an imaging device according to the present invention will be described in detail with reference to the attached drawings.

First Embodiment
<Configuration of Imaging Device>
FIG. 1 is a block diagram showing the configuration of an imaging device 10 (imaging device) according to the first embodiment. The imaging device 10 includes a lens device 100 (wide conversion lens, interchangeable lens) and an imaging device main body 200 (imaging device main body). Although the imaging device 10 can be applied to a smart phone, a tablet terminal, a surveillance camera, an inspection camera, and the like in addition to the digital camera, the application target is not limited to these devices.

<Configuration of Lens Device>
The lens apparatus 100 includes a lens 300 (wide conversion lens, interchangeable lens). The lens 300 is a lens (wide conversion lens) that is mounted on the imaging device main body 200 (on the object side relative to the Fresnel zone plate 210) to make the photographing angle of view wider than in the non-mounted state. The lens apparatus 100 and the imaging apparatus main body 200 are mounted (attached) via the lens side mount 130 and the main body side mount 270 (lens mounting portion), and when mounted, the lens side terminal 132 and the body side terminal 272 contact with each other. Thus, communication between the lens apparatus 100 and the imaging apparatus main body 200 becomes possible. Information of the lens 300 is stored in the memory 120 (lens information storage unit), and the stored information is acquired by an instruction from the image processing unit 230 (information acquisition unit 230E; see FIG. 4). For example, the lens configuration of the lens 300, the focal length, the shooting angle of view, the F value, the type and value of aberration, and the like can be stored in the memory 120. These pieces of information may be measured after manufacturing of the lens 300 (lens apparatus 100) and stored in the memory 120, or design values may be stored. Further, information input by the operation of the operation unit 260 may be used.

The lens apparatus 100 can be attached to and detached from the imaging apparatus main body 200 by the operation of the user, whereby a lens with a different angle of view and focal length can be attached according to the photographing purpose, photographing conditions, etc. and photographed under desired conditions. 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 mounted on the imaging device 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. 1 and 2 describe the case where the

lens devices

100, 102, 104, and 106 are attached to the imaging apparatus main body 200 via the lens side mount 130 and the main body side mount 270, the attachment to the imaging apparatus main body 200. Is not limited to such an embodiment. Besides, for example, a screw thread (lens attachment portion) provided on one of the

lens devices

100, 102, 104, 106 and the imaging device main body 200, and a screw groove (lens attachment portion provided on the other corresponding to the screw thread And may be carried out. The

lenses

300, 400, 500, and 600 are attached to the subject side (object side) of the Fresnel zone plate 210.

<Configuration of Imaging Device Body>
The imaging device body 200 includes a Fresnel zone plate 210 (Fresnel zone plate, coded aperture) and an imaging device 220 (imaging device), and light from an object is a lens 300 (or

lenses

400, 500, 600) and the Fresnel zone A projection image formed through the plate 210 is acquired by the imaging device 220. The Fresnel zone plate 210 is disposed on the imaging surface side of the imaging element 220 in a state where the center coincides with the center of the imaging element 220 and is parallel to the imaging surface 220 A (light receiving surface) of the imaging element 220. The Fresnel zone plate 210 may be replaceable with respect to the imaging device body 200. By using different Fresnel zone plates having different characteristics (size, pitch, phase, distance to the image sensor, etc.), the characteristics (field angle, depth (distance measurement accuracy, etc.), etc.) of the acquired projection image can be controlled and desired. The image of the characteristic can be reconstructed. In the following description, a Fresnel zone plate may be described as "FZP".

<Configuration of Fresnel zone plate>
Part (a) of FIG. 3 is a view showing FZP1 which is an example of the Fresnel zone plate 210. As shown in FIG. In FZP1, the transmittance of incident light varies continuously according to the FZP1 pattern according to the distance from the center, and the region closer to white (transmission region) has higher light transmittance and a region closer to black ( The light transmission rate is lower as the light shield region is). As a whole, the transmission areas and the light shielding areas are alternately arranged concentrically, and the transmission areas and the light shielding areas constitute a Fresnel zone plate. The distance between concentric circles narrows from the center of FZP1 toward the periphery. Such a concentric pattern (local change in spatial frequency) is expressed by the equations (2), (3), (7) etc. described later, and the fineness of the concentric circles in these equations is called "pitch". . The pitch is determined by the value of β described above, and 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 imaging apparatus main body 200 to store pitch information (a 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 passing through the center of the FZP and the imaging device 220 and perpendicular to the FZP and the imaging surface 220A of the imaging device 220. The FZP is disposed close to the imaging device 220. Depending on the distance to the image sensor 220, it is preferable that the projected image be blurred due to the diffraction of light, so it is preferable not to separate too much.

Part (b) of FIG. 3 is a view showing FZP2 which is another example of the Fresnel zone plate. FZP2 sets the threshold for the transmittance to the pattern of FZP1, and the region where the transmittance exceeds the threshold is the transmission region (white part) with 100% transmittance, and the region below the threshold is the transmission A light shielding area (black portion) with a rate of 0% is used, and the transmittance changes discontinuously (in two steps of 0% or 100%) according to the distance from the center. As a whole, the transmission areas and the light shielding areas are alternately arranged concentrically, and the transmission areas and the light shielding areas constitute a Fresnel zone plate. Thus, the "Fresnel zone plate" in the present invention includes an aspect such as FZP1 and an aspect such as FZP2 and, correspondingly, the "Fresnel zone pattern" in the present invention changes the transmittance continuously. Pattern and the pattern in which the transmittance changes discontinuously. A light shielding portion (a region not transmitting light as well as 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 being incident on the peripheral portion of the imaging element 220. You may

<Configuration of Image Sensor>
The imaging element 220 is an image sensor having a plurality of pixels formed of photoelectric conversion elements arranged in a two-dimensional direction. A microlens may be provided for each pixel to increase the light collection efficiency. In addition, color filters (for example, red, blue, and green) may be provided for each pixel so that a color image can be reconstructed. In this case, at the time of acquiring a projection image, interpolation processing according to the arrangement pattern of the color filter is performed as in the case of demosaicing processing (also referred to as synchronization processing) in color image generation in a normal digital camera. By this interpolation processing, a signal of a deficient color in each pixel (light receiving element) is generated, and a signal of each color (for example, red, blue, and green) is obtained in all the pixels. Such processing can be performed by the image processing unit 230.

The imaging device main body 200 includes an image processing unit 230, a storage unit 240, a display unit 250, and an operation unit 260, in addition to the above-described Fresnel zone plate 210 and imaging device 220, the Fresnel zone plate 210 and imaging device An image restoration or the like of the subject is performed based on the projection image acquired by 220.

<Configuration of Image Processing Unit>
FIG. 4 is a diagram showing the configuration of the 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 230E (lens information acquisition unit) and a display control unit 230F. The projected image input unit 230A controls the imaging device 220 to acquire, from the imaging device 220, a projected image formed on the imaging device 220 by the light from the subject being incident on the FZP. The multiplication image generation unit 230B multiplies the projection 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 frequency. , A complex image consisting of an image of the real part and an image of the imaginary part. The Fourier transform unit 230C reconstructs an image in the spatial domain by performing a two-dimensional complex Fourier transform on the complex image. The aberration correction unit 230D corrects an aberration (such as astigmatism, spherical aberration, coma, distortion, axial chromatic aberration, lateral 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 (for example, lens configuration, focal length, shooting angle of view, F value, type and value of aberration, etc.) of the lens 300 stored in the memory 120 of the lens device 100. Further, the information acquisition unit 230E acquires information (information on pitch) of the Fresnel zone plate 210 used for acquiring the projection image. The display control unit 230F controls display of a projection image, a complex image, a reconstructed image and the like on the display unit 250. In the ROM 230G (non-temporary recording medium), computer (processor) readable codes of various programs for operating the imaging device 10, such as a program for reconstructing an image, are recorded.

The functions of the image processing unit 230 described above can be realized using various processors. The various processors include, for example, a central processing unit (CPU) that is a general-purpose processor that executes software (programs) to realize various functions. The various processors described above also include a programmable logic device (PLD) which is a processor whose circuit configuration can be changed after manufacturing an FPGA (Field Programmable Gate Array) or the like. Furthermore, dedicated electric circuits and the like which are processors having a circuit configuration specially designed to execute specific processing such as application specific integrated circuits (ASICs) are also included in the various processors described above.

The function of each unit may be realized by one processor or may be realized by combining a plurality of processors. Also, multiple functions may be realized by one processor. As an example in which a plurality of functions are configured by one processor, first, one processor or more is configured by a combination of one or more CPUs and software, as represented by computers such as clients and servers; Is realized as a plurality of functions. Second, as typified by a system on chip (SoC) or the like, there is a mode using a processor that realizes the functions of the entire system with one integrated circuit (IC) chip. Thus, various functions are configured using one or more of the various processors described above as a hardware-like structure.

Furthermore, the hardware-like structure of these various processors is, more specifically, an electrical circuit (circuitry) combining circuit elements such as semiconductor elements.

When the processor (or electric circuit) described above executes software (program), computer readable code of software to be executed (for example, software for acquiring a projection image, acquiring lens information, restoring an image, etc.) It is stored in a non-transitory recording medium such as the ROM 230G, and the processor refers to the software. At the time of processing using software, for example, RAM (Random Access Memory) is used as a temporary storage area, and data stored in, for example, EEPROM (Electronically Erasable and Programmable Read Only Memory) is referred to. In FIG. 4, devices such as a RAM and an EEPROM are not shown.

<Configuration of Storage Unit>
The storage unit 240 is composed of non-temporary recording media 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. . The lens information 240A is information of 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 240 B is a projected image acquired from the imaging element 220. The Fresnel zone plate information 240 C 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 240 C may be information acquired from the imaging device 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 local spatial frequency phases. The multiplication image 240E (multiplication image) is obtained by multiplying the projected image by the Fresnel zone pattern (first and second Fresnel zone patterns) indicated by the Fresnel zone pattern information 240D, and an image of the real part and an image of the imaginary part And a complex image consisting of The reconstructed image 240F is an image of a spatial region obtained by performing two-dimensional complex Fourier transform on the multiplied image 240E.

<Configuration of Display Unit and Operation Unit>
The display unit 250 includes a display device such as a liquid crystal display (not shown), and displays a projected image, a multiplied image, a reconstructed image and the like, and for UI (User Interface) when inputting an instruction via the operation unit 260 It is also used for screen display of The operation unit 260 includes devices such as a keyboard, a mouse, a button, and a switch (not shown), and the user uses these devices to issue a projection image acquisition instruction, an image reconstruction instruction, focusing distance conditions, 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 the operation unit 260 in addition to image display.

<Specific configuration of lens>
Example 1
Part (a) of FIG. 6 is a view showing the arrangement of the lens 300, the Fresnel zone plate 210, and the imaging surface 220A of the imaging device 220. The lens 300 is a wide conversion lens composed of a front group 310 having negative power (refractive power, hereinafter the same) in order from the object side (object side) and a rear group 320 having positive power. , 306, 308. The Fresnel zone plate 210 is disposed at the position of the pupil of the lens 300 (the position of the stop).

Example 2
Part (b) of FIG. 6 is a view showing the arrangement of the lens 400, the Fresnel zone plate 210, and the imaging surface 220A of the imaging device 220. The lens 400 is a wide conversion lens including a front group 410 having negative power and a rear group 420 having positive power in order from the object side (subject side), and includes

lenses

402, 404, 406, and 408. Ru. The Fresnel zone plate 210 is disposed at the position of the pupil of the lens 400 (the position of the stop).

Example 3
Part (c) of FIG. 6 is a view showing the arrangement of the lens 500, the Fresnel zone plate 210, and the imaging surface 220A of the imaging device 220. The lens 500 is a wide conversion lens including a front group 510 having negative power and a rear group 520 having positive power in order from the object side (subject side), and includes

lenses

502, 504, 506, and 508. Ru. The Fresnel zone plate 210 is disposed at the position of the pupil of the lens 500 (the position of the stop).

Example 4
Part (d) of FIG. 6 is a view showing the arrangement of the lens 600, the Fresnel zone plate 210, and the imaging surface 220A of the imaging device 220. The lens 600 is a wide conversion lens including a front group 610 having negative power and a rear group 620 having positive power in order from the object side (subject side), and includes

lenses

602, 604, 606, and 608. Ru. The Fresnel zone plate 210 is disposed at the position of the pupil of the lens 600 (the position of the stop).

Although the angle of view of the

lenses

300, 400, 500, and 600 is fixed, the lens attached to the imaging apparatus main body in the imaging apparatus of the present invention may be a zoom lens having a variable angle of view (focal length).

<Optical path diagram>
Part (a) of FIG. 7 shows the optical paths of the axial light beam B1 and the light beam B2 of the maximum angle of view with respect to the lens 300 in a state where the ideal lens I1 (lens with zero aberration) is arranged at the pupil position of the lens 300. FIG. In fact, since the Fresnel zone plate 210 is disposed at the position of the ideal lens I1 and the light beam travels as a wavefront, the light from the Fresnel zone plate 210 (on the side of the imaging device 220) does not necessarily have an optical path like a dotted line. For reference, an optical path when the ideal lens I1 is disposed 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 in the case where 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 normalization. The lens data of the ideal lenses I2 to I4 shown below are the same as that of the ideal lens I1. Here, mm represents a millimeter, and deg represents an angle.

Similarly, part (b) of FIG. 7 shows axial luminous flux B3 with respect to lens 400 and luminous flux B4 of the maximum angle of view in a state where ideal lens I2 (lens with zero aberration) is disposed at the pupil position of lens 400. Is a diagram showing an optical path of In fact, since the Fresnel zone plate 210 is disposed at the position of the ideal lens I2 and the light beam travels as a wave front, the light from the Fresnel zone plate 210 (the image sensor 220 side) does not necessarily have an optical path like a dotted line portion. For reference, an optical path when the ideal lens I2 is disposed is shown.

Similarly, part (c) of FIG. 7 shows axial luminous flux B5 with respect to lens 500 and luminous flux B6 of the maximum angle of view in a state where ideal lens I3 (lens with zero aberration) is disposed at the pupil position of lens 500. Is a diagram showing an optical path of In fact, since the Fresnel zone plate 210 is disposed at the position of the ideal lens I3 and the light beam travels as a wavefront, the light from the Fresnel zone plate 210 (on the side of the imaging device 220) does not necessarily have an optical path like a dotted line. For reference, an optical path when the ideal lens I3 is disposed is shown.

Similarly, part (d) of FIG. 7 shows axial luminous flux B7 with respect to lens 600 and luminous flux B8 of the maximum angle of view in a state where ideal lens I4 (lens with zero aberration) is disposed at the pupil position of lens 600. Is a diagram showing an optical path of In fact, since the Fresnel zone plate 210 is disposed at the position of the ideal lens I4 and the light beam travels as a wave front, the light from the Fresnel zone plate 210 (the image sensor 220 side) does not necessarily have an optical path like a dotted line. For reference, an optical path when the ideal lens I4 is disposed is shown.

<Lens data>
Parts (a) to (c) of FIG. 8 are tables showing lens data of the

lenses

300, 400, and 500. In the table, the surface with “*” attached to the surface number indicates that the surface is aspheric. Similarly, FIG. 9 is a table showing lens data of the lens 600. The lens data in FIGS. 8 and 9 is data in the case where 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 normalization. If the distance is k times by changing the focal length, the radius of curvature and the surface distance are also k times.

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

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

<Specifications of Example>
FIG. 15 is a table showing specifications of Examples 1 to 4. With the configuration described above, in Example 1 (when the lens 300 is mounted), the angle of view is changed (wider to 60.0 degrees) than the original optical system (the angle of view is 20.6 degrees). I understand. Similarly, in Example 2 (when the lens 400 is mounted), the angle of view changes with respect to the original optical system (the angle of view is 46.5 degrees) (wide as 80.0 degrees). Similarly, in Example 3 (when the lens 500 is mounted), the angle of view changes with respect to the original optical system (the angle of view is 24.5 degrees) (wide as 60.0 degrees). Similarly, in Example 4 (when the lens 600 is mounted), the angle of view changes with respect to the original optical system (the angle of view is 20.2 deg.) (Wide as 60.0 deg). The “original optical system” in the first to fourth embodiments is an optical system (a focal length is 1.0 mm) using a coded aperture such as the Fresnel zone plate 210.

<Edge light>
FIG. 16 is a table showing conditional expressions for calculating the peripheral light amount in Examples 1 to 4. The meanings of the parameters in the table are as follows. Any of the examples satisfies the numerical range in each aspect of the present invention. The definitions of Cs, Ct, Mt and Ms are shown in parts (a), (b) and (c) of FIG. 17 (shown as a representative example for Example 1). The part (b) of FIG. 17 is a figure which shows the plane P1, and the (c) part of FIG. 17 is a figure which shows the plane P2. The planes P1 and P2 are planes perpendicular to the chief ray L1 of the axial light beam B1 and the chief ray L2 of the light beam B2 having the largest angle of view.

Cs: Length in the sagittal direction (tangent direction) of axial luminous flux incident on the surface closest to the object side Ms: Length in sagittal direction of luminous flux of maximum angle of view incident on the surface closest to the object DA: Wide conversion lens ( Maximum air gap in lens 300, 400, 500, 600) Ff: Focal length of lens group on the object side from DA Ct: Length of tangential direction (radial direction) of axial light beam incident on surface closest to object side M t: The length in the tangential direction of the light flux with the largest angle of view incident on the surface closest to the object side, projected on the surface perpendicular to the chief ray WCTL: The first surface to the final surface of the wide conversion lens Length to WCf: Focal length of wide conversion lens Dist: Optical distortion when the wide conversion lens is mounted on the ideal lens Figure 18 Is a table showing the peripheral light amount ratio (indicated on the optical axis as 100% and represented by the fourth power of (cos γ) to the half angle of view γ) for (Wide conversion lens of Example 1 to 4 + ideal lens) FIG. 19 is a graph showing the peripheral light amount ratio for the ideal lens and (wide conversion lens of the examples 1 to 4 + ideal lens). The peripheral light ratio of the ideal lens when the half angle of view γ is 30 deg is about 56%, and it is about 34% for 40 deg, but in the case of (wide conversion lens of Examples 1 to 4 + ideal lens) The peripheral light amount ratio is about 78% to 99%, and it can be seen that the peripheral light amount ratio is improved (not reduced).

<Reconstruction of image>
The reconstruction of an image by the imaging device 10 configured as described above will be described. FIG. 20 is a flowchart showing image reconstruction processing.

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

<Local spatial frequency information>
In step S110, information (a pitch of the Fresnel zone plate 210) of the local spatial frequency of the Fresnel zone plate 210 used for the projection image acquisition by the image processing unit 230 (the information acquisition unit 230E) is input. 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. In addition, 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 the equations (2) to (4), (7) etc. described later), specifically, the value of β may be input. When a known subject (for example, point light source at infinite distance) is photographed, the pitch (value of β) can be acquired by analyzing the photographed image. In addition, image reconstruction may be repeated while changing the pitch (the value of β) to obtain a value capable of obtaining a clear image.

<Generation of complex image>
In step S120, the image processing unit 230 (multiplication image generation unit 230B) multiplies the projection image by the first and second Fresnel zone patterns to generate a complex image consisting of a real part image and an imaginary part image. Do. The Fresnel zone pattern to be multiplied in step S120 can be a pattern selected according to the pitch (value of β) input in step S110 among the patterns (Fresnel zone pattern information 240D) stored in the storage unit 240. . 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 in the storage unit 240 as a multiplication image 240E.

<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 (the phase at the center is 0 deg), and this is multiplied by the projected image to obtain an image of the real part. Is obtained. Also, the second Fresnel zone pattern can be, for example, the pattern shown in part (b) of FIG. 21 (the pitch is the same as the first Fresnel zone pattern, and the phase is shifted by 90 degrees). An image of the imaginary part is obtained by multiplication. As described above for the equation (7) etc., the phase shift of the first and second Fresnel zone patterns is preferably 90 degrees, but a positive or negative range of 70 deg or more and 110 deg or less reconstructs a clear image can do. The phase of the local spatial frequency of the first Fresnel zone pattern or the second Fresnel zone pattern may be identical to the phase of the Fresnel zone plate 210.

When using a Fresnel zone pattern, data of a plurality of Fresnel zone patterns different in phase can be stored as Fresnel zone pattern information 240D in the storage unit 240, 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 information of pitch and phase. Since such a Fresnel zone pattern is stored in the storage unit 240 as the Fresnel zone pattern information 240D, which is electronic data, it is possible to quickly and easily select and generate a desired pattern. In addition, the size of the apparatus is increased by holding the plates (substrates) corresponding to a plurality of patterns as an entity, the manufacturing cost is increased, and the characteristic variation among the plurality of patterns (manufacturing variation, temporal change, temperature change) There is no problem such as image quality deterioration due to

<Magnification factor of Fresnel zone pattern>
When the subject (light source) is at infinity, parallel light is incident on the Fresnel zone plate 210, and the projected image formed on the imaging device 220 has the same size as the Fresnel zone plate 210, but the subject is finite. When the light is present at a distance, light having a spread is incident, and the projected image becomes larger as the distance is shorter. Therefore, an image focused at a desired distance can be obtained by using, as the first and second Fresnel zone patterns, patterns having different enlargement ratios according to the subject distance to be focused. For example, a plurality of patterns corresponding to the subject distance may be stored in the storage unit 240 as the Fresnel zone pattern information 240D, and read and used. Also, one Fresnel zone pattern may be stored as a reference pattern, and may be enlarged at a different enlargement factor according to the subject distance. In this case, a pattern corresponding to the subject distance infinity 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 according to the subject distance.

The focus evaluation value of the reconstructed image (for example, the luminance signal in the focus evaluation area set in the image) is repeatedly generated while repeating the complex image generation (step S120) and the image reconstruction (step S130) while changing the enlargement ratio. A clear image may be acquired by maximizing the integral value of.

Thus, the imaging device 10 according to the first embodiment can perform refocusing using the Fresnel zone plate 210 (coded aperture) and the Fresnel zone pattern.

<Reconstruction of image>
In step S130, the image processing unit 230 (Fourier transform unit 230C) performs two-dimensional complex Fourier transform on the complex image to reconstruct an image of the subject (image in the spatial region) (described later). Furthermore, the image processing unit 230 (aberration correction unit 230D) causes the aberration (the astigmatism, the lens 300, the lens 400, and the like) attached to the imaging device main body 200 in the reconstructed image (the image in the space region) Aberration, spherical aberration, coma, distortion, axial chromatic aberration, lateral chromatic aberration, etc. are corrected. The correction is performed based on the lens information 240A acquired from the memory 120. Also, aberration correction may be performed before or after the image is reconstructed. When correcting the aberration before reconstruction, for example, by changing the shape and / or size of the Fresnel zone pattern (coded aperture) to be multiplied to the projection image according to the type and / or amount of aberration to be corrected be able to. On the other hand, when correcting the aberration after the reconstruction, for example, an image such as applying different filters (such as a filter for point image restoration) depending on conditions such as the type and / or degree of aberration to be corrected and the position in the image. It can be done by processing. However, the correction of the aberration 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 in the storage unit 240 as a reconstructed image 240F.

<Details of image restoration>
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 equation (2).

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

It is assumed that this coding aperture (Fresnel zone plate) is disposed at a distance d from the sensor surface of the imaging device. At this time, assuming that light (parallel light) is incident at an incident angle θ from a point light source at infinite distance, the shadow of the coded aperture (Fresnel zone plate) moves in parallel by Δr (= d × tan θ) and the sensor It looks up. The translated shadow S (r) is expressed by equation (4).

Although I2 (r) and S (r) are originally two-dimensional images and are two-variable functions, here, for the sake of simplicity, only focusing on one-dimensional images on a cross section cut at a plane including the center and the incident light source Think. However, it can be easily extended to the two-dimensional case 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 with the non-displaced Fresnel zone aperture image (Fresnel zone pattern). Here, regarding the function to be internally multiplied, the case of two functions represented by the following formulas (6) and (7) will be considered. The imaginary unit is j.

Mr (r) is the same real 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) is equivalent to the case where the projection image of the real aperture is multiplied by the Fresnel zone pattern represented by the real function Mr (r) Do. Mc (r) is a complex number ^{function, Mc (r) = cosβr 2} + j × sinβr 2 = cosβr 2 -j × cos (βr 2 + π / 2) because the real part, imaginary part phase (π / 2) That is, it corresponds to the Fresnel zone pattern shifted by 90 degrees. The real part (cos β r ² ) of Mc (r) is the same as Mr (r). In the first embodiment, the projected image is multiplied by the two Fresnel zone patterns (first and second Fresnel zone patterns) corresponding to the real part and imaginary part of the complex function and having different phases as described above. A complex image consisting of an image of a part and an image of an imaginary part is generated.

The image after multiplication (multiplied 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), which is a case where Mr (r) and Mc (r) are used for the internally multiplied image. The second term is the moiré interference fringes in which the “difference frequency” between the superimposed Fresnel zone apertures (corresponding to cos (α−φ when the two apertures are represented by cos α and cos φ) is extracted, Since this corresponds to the basis of the Fourier transform, it is converted to a delta function by applying the Fourier transform to become a "point" and a component contributing to imaging. The third term corresponds to the “sum frequency” (corresponding to cos (α + φ)), which is a component that does not contribute to image formation even when subjected to Fourier transform and acts as noise.

The offset correction is appropriately applied to each of Fr (r) and Fc (r), and images with the first term eliminated are set 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 formulas (10) and (11) as fr (k) and fc (k).

Here, ξ (k, β, Δr) is a real number polynomial. If the absolute value of a complex number is taken with respect to these, a restored image can be obtained, but in the case of fr (k) (in the case of the prior art), the first term and the second term produce two symmetrical points at the origin , It becomes a restored image that is overlapped point-symmetrically. 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 reconstructed normally. Common to both is the fact that the third term of fr (r) and the second term of fc (r) act as noise, and due to this term, the modulation transfer function (MTF) Can not be 100%, which means that the MTF will not be 100% in the absence of noise from the sensor. However, since this noise decreases as the value of β increases, it is possible to reduce the effect by increasing the value of β (to make the pattern finer).

Regarding the first term of fc (k) (in the case of the first embodiment), the phase is rotated depending on the incident angle of light, but when the absolute value of the complex number is taken with respect to this, infinite distance light It can be confirmed that the image is formed into a delta function (point) in response to the arrival of. Since all calculations from the angular spectrum of the incident light to the imaged image are linear, superposition is established, which can explain the imaging of the image.

Incidentally, when calculated for the two-dimensional case, the peripheral light amount is (4) to (cos γ), and the distortion is 2 × β × d × tan γ. γ represents a half angle of view.

<Effect of 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 with different angles of view when mounted on an imaging device It can be obtained with good image quality. In addition, the imaging device 10 according to the first embodiment includes the wide conversion lens (

lens

300, 400, 500, 600) according to the first embodiment so that images with different angle of view have good image quality (peripheral light ratio) High optical distortion). Further, the angle of view can be changed while maintaining the refocusing function by 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 complex Fourier transformed to reconstruct an image in the spatial domain. However, the reconstruction of the image in the imaging device of the present invention is not limited to the aspect using a complex image. As described above for equations (6), (8), (10) etc., the projection image is multiplied by a real function such as Mr (r) to obtain a multiplication image, and this multiplication image is subjected to Fourier transform May be reconfigured. In this case, although overlapping of subject images occurs in the restored image, it is possible to cope by displaying the reconstructed image in half and displaying it. Further, even in the case of multiplying by a real number function, it is possible to obtain an image focused at a desired distance by using a Fresnel zone pattern in which the enlargement ratio is different according to the object 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.

DESCRIPTION OF SYMBOLS 10

Imaging device

100, 102, 104, 106 Lens device 120 Memory 130 Lens side mount 132 Lens side terminal 200 Imaging device main body 210 Fresnel zone plate 220 Imaging element 220A Imaging surface 230 Image processing part 230A Projection image input part 230B Multiplication image generation part 230C Fourier transform unit 230D aberration correction unit 230E information acquisition unit 230F display control unit 230G ROM
240 storage unit 240A lens information 240B projected image 240C Fresnel zone plate information 240D Fresnel zone pattern information 240E multiplied image 240F reconstructed image 250 display unit 260 operation unit 270 body side mount 272

body side terminals

300, 302, 304, 306, 308, 400, 402, 404, 406, 408, 500, 502, 504, 506, 508, 600, 604, 606, 608

Lenses

310, 410, 510, 610

Front Group

320, 420, 520, 620 Rear Group B1, B3, B5, B7 On-axis luminous flux B2, B4, B6, B8 luminous flux Fr multiplied image FZP1 Fresnel zone plate FZP2 Fresnel zone plate I Pattern I1, I2, I3, I4 Ideal lens L Optical axis L1, L2 chief ray M Real function P1, P2 plane S steps d distance γ half angle θ the angle of incidence of shadow S100 ~ S140 reconstruction process

Claims

A wide conversion lens mounted on the object side of the imaging device, the wide conversion lens satisfying the following conditional expressions (1) and (2):
1.1 <Ms / Cs (1)
0.3 <| Ff / DA | <2.0 (2)
Where Cs is the length in the sagittal direction of the axial luminous flux incident on the surface closest to the object side of the wide conversion lens, and Ms is the luminous flux of the largest angle of view incident on the surface closest to the object side of the wide conversion lens. The length in the sagittal direction is, DA is the maximum air gap 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 gap exists.
The wide conversion lens according to claim 1, satisfying the following conditional expression (3):
2.2 <Mt / Ct (3)
Where Ct is the length in the tangential direction of the axial luminous flux incident on the surface closest to the object side of the wide conversion lens, and Mt is the luminous flux at the maximum angle of view incident on the surface closest to the object on the wide conversion lens It is the length which projected the length of the tangential direction of to the surface perpendicular to the chief ray.
The wide conversion lens according to claim 1 or 2, satisfying the following conditional expression (4):
| WCTL / WCf | <0.1 (4)
Here, 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 furthest to 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, wherein the following conditional expression (5) is satisfied:
| Dist | <10% (5)
However, Dist is an optical distortion when the wide conversion lens is attached to an ideal lens.
The wide conversion lens according to any one of claims 1 to 4, comprising a front group of negative refractive power and a rear group of positive refractive power in order from the object side.
A wide conversion lens according to any one of claims 1 to 5;
An imaging device main body having an imaging element and to which the wide conversion lens is attached;
An imaging device comprising:
The image pickup apparatus main body has a coded aperture, an image pickup element which outputs a signal of a projected image formed by the coded aperture, and an image restoration unit which reconstructs an image of a spatial region based on the signal. The imaging device according to claim 6.
7. The imaging device body according to claim 6, wherein the wide conversion lens is mounted on the object side relative to the encoding aperture, and the projection image is formed on the imaging element by the wide conversion lens and the encoding aperture. The imaging device according to 7.
The imaging device according to claim 7, wherein the image restoration unit corrects an aberration caused by the wide conversion lens in the image of the space area.
A lens information acquisition unit that acquires information of the wide conversion lens;
The imaging device according to claim 9, wherein the image restoration unit corrects the aberration based on the acquired information.
The coding aperture is a Fresnel zone plate,
The image restoration unit multiplies the projected image formed on the imaging device by the wide conversion lens and the Fresnel zone plate by a Fresnel zone pattern corresponding to the Fresnel zone plate to generate a multiplied image, and the multiplication is performed. The imaging apparatus according to any one of claims 7 to 10, which performs Fourier transform on an image to reconstruct an image of the spatial region.
The imaging device according to any one of claims 7 to 11, wherein the wide conversion lens is an interchangeable lens attached to and removed from the imaging device.