WO2021059763A1 - 撮像光学系、および撮像装置 - Google Patents

撮像光学系、および撮像装置 Download PDF

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Publication number
WO2021059763A1
WO2021059763A1 PCT/JP2020/030000 JP2020030000W WO2021059763A1 WO 2021059763 A1 WO2021059763 A1 WO 2021059763A1 JP 2020030000 W JP2020030000 W JP 2020030000W WO 2021059763 A1 WO2021059763 A1 WO 2021059763A1
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Prior art keywords
optical system
imaging
imaging optical
image
aperture
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Ceased
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English (en)
French (fr)
Japanese (ja)
Inventor
直道 菊地
美希 中山
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Sony Corp
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Sony Corp
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Priority to JP2021548407A priority Critical patent/JP7501538B2/ja
Priority to US17/753,824 priority patent/US12270975B2/en
Priority to EP20868379.7A priority patent/EP4012471B1/en
Publication of WO2021059763A1 publication Critical patent/WO2021059763A1/ja
Anticipated expiration legal-status Critical
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/02—Telephoto objectives, i.e. systems of the type + - in which the distance from the front vertex to the image plane is less than the equivalent focal length
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
    • G02B23/24—Instruments or systems for viewing the inside of hollow bodies, e.g. fibrescopes
    • G02B23/2407—Optical details
    • G02B23/2423—Optical details of the distal end
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3083—Birefringent or phase retarding elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/0004—Microscopes specially adapted for specific applications
    • G02B21/0012—Surgical microscopes
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/18—Arrangements with more than one light path, e.g. for comparing two specimens
    • G02B21/20—Binocular arrangements
    • G02B21/22—Stereoscopic arrangements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/36—Microscopes arranged for photographic purposes or projection purposes or digital imaging or video purposes including associated control and data processing arrangements
    • G02B21/361—Optical details, e.g. image relay to the camera or image sensor
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
    • G02B23/24—Instruments or systems for viewing the inside of hollow bodies, e.g. fibrescopes
    • G02B23/26—Instruments or systems for viewing the inside of hollow bodies, e.g. fibrescopes using light guides
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/0075—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means for altering, e.g. increasing, the depth of field or depth of focus
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/005—Diaphragms

Definitions

  • the present disclosure relates to an imaging optical system and an imaging device capable of extending the depth of field.
  • Patent Documents 1 to 4 Various techniques for expanding the depth of field have been proposed (see Patent Documents 1 to 4).
  • the imaging optical system is composed of an aperture diaphragm, an imaging optical system for forming an image toward the imaging surface of the imaging element, and a substance having a birefringence, and is composed of imaging optics. It is equipped with an optical phase modulator that gives two pupil functions to the system, and satisfies the following conditional expression.
  • the image pickup apparatus includes an image pickup optical system and an image pickup element arranged at an imaging position of the image pickup optical system, and the image pickup optical system relates to the embodiment of the present disclosure. It is composed of an imaging optical system.
  • resolution is obtained by giving two pupil functions to the imaging optical system by an optical phase modulator while satisfying a predetermined condition.
  • the depth of field is expanded while suppressing the deterioration of performance.
  • FIG. 1 It is explanatory drawing which shows an example of the passing range of a central ray and the passing range of a peripheral ray in BM when there is vignetting in the image pickup optical system which concerns on one Embodiment. It is sectional drawing which shows an example of the central ray and the peripheral ray when there is vignetting in the image pickup optical system which concerns on one Embodiment. It is a top view which shows roughly the structure of the concentric pattern region of BM and the diameter of an aperture diaphragm in the image pickup optical system which concerns on Example 1. FIG. It is sectional drawing which shows the whole structure of the imaging optical system which concerns on Example 1. FIG. It is a characteristic diagram which shows the through-focus MTF of the imaging optical system which concerns on Example 1. FIG.
  • FIG. 1 It is a characteristic diagram which shows the frequency characteristic of MTF at the focus position of the imaging optical system which concerns on Example 1.
  • FIG. It is a top view which shows roughly the structure of the concentric pattern region of BM and the diameter of an aperture diaphragm in the image pickup optical system which concerns on Example 2.
  • FIG. It is sectional drawing which shows the whole structure of the imaging optical system which concerns on Example 2.
  • FIG. It is a characteristic diagram which shows the through-focus MTF of the imaging optical system which concerns on Example 2.
  • FIG. 1 It is a top view which shows roughly the structure of the concentric pattern region of BM and the diameter of an aperture diaphragm in the image pickup optical system which concerns on Example 3.
  • FIG. It is sectional drawing which shows the whole structure of the imaging optical system which concerns on Example 3.
  • FIG. It is a characteristic diagram which shows the through-focus MTF of the imaging optical system which concerns on Example 3.
  • FIG. It is a characteristic diagram which shows the frequency characteristic of MTF at the focus position of the imaging optical system which concerns on Example 3.
  • Patent Document 1 Japanese Unexamined Patent Publication No. 2015-5919 proposes a technique for expanding the depth of field by imparting spherical aberration to the imaging optical system.
  • this technique is premised on a bright F-number, and is effective only when the limit resolution of the imaging optical system has sufficient margin for the Nyquist frequency of the sensor. Since the optical system used in medical imaging equipment has a dark F value, its resolution performance is close to the diffraction limit. If spherical aberration occurs, the limit resolution is impaired.
  • Patent Document 2 Japanese Patent Laid-Open No. 2018-101065
  • Patent Document 3 Japanese Patent Laid-Open No. 2010-271689
  • WFC Wide Front Coding
  • AR Anti Reflection
  • Patent Document 4 (US Patent Application Publication No. 2012/0281280) proposes a phase modulation element using a birefringent material, thereby proposing a technique that enables depth expansion from a normal optical system. ..
  • the specific scope of application and the optimum design solution have not been specified.
  • the imaging optical system according to the embodiment includes an aperture diaphragm, an imaging optical system, and an optical phase modulator.
  • the imaging optical system forms an image toward the imaging surface of the image pickup device.
  • An optical phase modulator is an optical element composed of a material having a birefringence and giving two pupil functions to an imaging optical system by applying different phase modulations to two polarized lights having an orthogonal relationship with each other. Is.
  • FIG. 1 schematically shows a configuration example of an optical phase modulator in an imaging optical system according to an embodiment of the present disclosure.
  • FIG. 2 schematically shows another configuration example of the optical phase modulator in the imaging optical system according to the embodiment.
  • the optical phase modulator in the imaging optical system according to the embodiment is a depth expanding device (BM: Birefringent Mask), and has an effect of expanding the depth of field of the imaging optical system.
  • BM Birefringent Mask
  • the imaging optical system according to the embodiment is an EDOF (Extended Depth of Focus) optical system in which the depth of field is extended by mounting a BM.
  • EDOF Extended Depth of Focus
  • the technology of the BM device itself is also described in, for example, Patent Document 4 above.
  • the technology of the present disclosure is similar to WFC technology.
  • the BM is an optical element having no refractive power, and has an optical element substrate and a birefringent layer formed on the surface of the optical element substrate.
  • the BM10 shown in FIG. 1 it has a glass substrate 12 and a BM layer 11 as a birefringent layer formed on the surface of the glass substrate 12.
  • the BM may have a structure in which a birefringent layer is sandwiched between two optical element substrates.
  • a structure in which the BM layer 11 as a birefringent layer is formed between the two glass substrates 12 and 13 may be used. If the sandwich type structure is used, for example, in the structure shown in FIG. 2, it is easy to apply an AR coat or the like on the glass substrate 13, so that the concern about ghosts and flares is reduced.
  • FIG. 3 schematically shows a configuration example of a concentric pattern region of the BM10 in the imaging optical system according to the embodiment.
  • the BM10 does not have a structure such as an uneven shape for obtaining the effect.
  • the BM layer 11 has concentric pattern regions, which are oriented so that the relative angle of birefringence anisotropy between adjacent pattern regions is 90 °.
  • FIG. 3 shows an example in which the first concentric pattern region A1, the second concentric pattern region B1, and the third concentric pattern region A2 are formed in order from the center.
  • the number of concentric pattern regions is not limited to three, and two or four or more may be formed.
  • 4 (A) to 4 (D) schematically show the optical characteristics of the optical phase modulator (BM10).
  • FIG. 5 schematically shows a configuration example of an imaging optical system (normal optical system 102) according to a comparative example.
  • FIG. 6 schematically shows a configuration example of the imaging optical system (EDOF optical system) 101 according to the embodiment.
  • the imaging optical system according to the comparative example shown in FIG. 5 includes an aperture diaphragm St and an imaging optical system 20.
  • the imaging optical system according to the comparative example shown in FIG. 5 is a normal optical system 102 that does not include BM10 as a component.
  • the imaging optical system 101 according to the embodiment shown in FIG. 6 is an EDOF optical system provided with a BM 10 in the vicinity of the aperture stop St with respect to the configuration of the normal optical system 102.
  • FIG. 6 shows a configuration example in which the BM10 is arranged on the imaging surface Sip side of the aperture stop St, a configuration in which the BM10 is arranged on the object side of the aperture stop St is also possible.
  • FIG. 6 shows a configuration example in which the imaging optical system 20 is arranged on the imaging surface Sip side of the aperture diaphragm St, but a part of the optics of the imaging optical system 20 is located on the object side of the aperture diaphragm St.
  • the system may be arranged.
  • An image pickup device equipped with such an image pickup optical system 101 has a PSF (Point Spread Function, point image distribution) described later with respect to an image pickup element arranged at an imaging position by the image pickup optical system 101 and an image taken by the image pickup element. It includes an image processing unit 110 that performs image processing using the deconvolution derived from the function).
  • PSF Point Spread Function, point image distribution
  • FIG. 4A shows an example of the refractive index acting on two orthogonal polarized lights (X polarized light and Y polarized light) in BM10.
  • FIG. 4B shows an example of phase modulation in which BM10 acts on X-polarized light and Y-polarized light, respectively.
  • FIG. 4C shows a through-focus MTF (Modulation transfer function) for a plurality of spatial frequencies for each of the X-polarized light and the Y-polarized light.
  • FIG. 4D shows through-focus MTFs for a plurality of spatial frequencies for each of the normal optical system 102 and the imaging optical system (EDOF optical system) 101 according to the embodiment.
  • EEOF optical system imaging optical system
  • the first concentric pattern region A1 and the third concentric pattern region A2 are oriented in the Y direction, and the second concentric pattern region B1 is oriented in the X direction. It is assumed that there is.
  • the refractive index of n acts on Y-polarized light, but the BM10 is birefringent. Since it has a rate, a refractive index of n + ⁇ n acts on X-polarized light.
  • a refractive index of n + ⁇ n acts on Y-polarized light
  • a refractive index of n acts on X-polarized light.
  • the refractive indexes acting on the first and third concentric pattern regions A1 and A2 and the second concentric pattern region B1 are different for each of the X-polarized light and the Y-polarized light. Therefore, as shown in FIG. 4B, the first and third concentric pattern regions A1 and A2 and the second concentric pattern region B1 are formed by the distance (thickness of the BM10) when the BM10 is transmitted. , The phase of the transmitted light is out of phase.
  • the guideline for retardation is approximately ⁇ / 4 with respect to the main wavelength ⁇ .
  • the light that has passed through the BM 10 has different wave planes for X-polarized light and Y-polarized light, and is imaged by the imaging optical system 20. Since the X-polarized light and the Y-polarized light have different wave planes, as shown in FIG. 6, the X-polarized light ray Lb and the Y-polarized light ray La are located before and after the image formation position P1 of the normal optical system 102, respectively. An image is formed on Pb and Pa. The respective through-focus MTFs of X-polarized light and Y-polarized light are as shown in FIG. 4 (C).
  • the overall imaging performance of the EDOF optical system is the average value of X-polarized light and Y-polarized light.
  • the through-focus MTF obtained by averaging the respective through-focus MTFs of X-polarized light and Y-polarized light in the EDOF optical system has a gentler shape than the through-focus MTF of the normal optical system 102. ..
  • the wave surface in the EDOF optical system is not an ideal wave surface, the peak MTF decreases.
  • X-polarized light and Y-polarized light are conjugated and imaged with different wave planes. Therefore, it can be said that the EDOF optical system equipped with the BM10 "has two pupil functions".
  • P1 (u, v)
  • P2 (u, v)
  • U and v are the coordinates in the X and Y directions on the pupil
  • ⁇ (u and v) are the wave surface aberrations of the imaging optical system 20 in the state where the BM 10 is not mounted.
  • FIG. 7 shows a comparison between the optical characteristics of the imaging optical system (normal optical system 102) according to the comparative example and the optical characteristics of the imaging optical system (EDOF optical system) 101 according to the embodiment.
  • FIG. 7 shows an example of the frequency characteristics of PSF and MTF as optical characteristics.
  • FIG. 8 shows a comparison between the through-focus MTF of the imaging optical system (normal optical system 102) according to the comparative example and the through-focus MTF of the imaging optical system (EDOF optical system) 101 according to the embodiment.
  • FIG. 8A shows an example of a through-focus MTF of the imaging optical system (normal optical system 102) according to the comparative example.
  • FIG. 8B shows an example of the through-focus MTF of the imaging optical system (EDOF optical system) 101 according to the embodiment.
  • the peak value of the MTF of the EDOF optical system is lower than that of the normal optical system 102. Therefore, in the image pickup apparatus according to the embodiment, a deconvolution filter (deconvolution filter) for image processing is created from the PSF of the EDOF optical system, and the image processing unit 110 (FIG. 6) captures images via the EDOF optical system. It is desirable to perform arithmetic processing by the deconvolution filter on the resulting image. By performing this process, as shown in FIG. 8B, the MTF can be restored to the same level as that of the normal optical system 102.
  • a deconvolution filter deconvolution filter
  • the BM10 can keep the high-frequency MTF at 0 or more at the just focus position, if the deconvolution process for resolving the resolution is added, the BM10 is just focused as shown in FIGS. 8 (A) and 8 (B). At the position, it is possible to realize a limit resolution comparable to that of the normal optical system 102.
  • the imaging optical system 101 can be applied to, for example, an endoscope camera head such as a rigid endoscope or an imaging camera unit for a microscope. Further, it can be used as an optical system for capturing an image by another afocal optical system or a substantially afocal optical system.
  • FIG. 9 schematically shows an application example 1 of the imaging optical system 101 according to the embodiment to an imaging device.
  • FIG. 9 shows a configuration example in which the imaging optical system 101 according to the embodiment is applied to the endoscope camera head 30.
  • the endoscope 31 is, for example, a rigid endoscope or a fiberscope.
  • An eyepiece 32 is attached to the endoscope 31.
  • the camera head 30 for an endoscope is attached to the eyepiece 32.
  • the endoscope camera head 30 includes an image pickup optical system 101 and an image pickup element 100. Image processing using deconvolution derived from the point image distribution function is added to the image captured by the image sensor 100 in the image processing unit 110 (FIG. 6).
  • FIG. 10 schematically shows an application example 2 of the imaging optical system 101 according to the embodiment to an imaging device.
  • FIG. 10 shows a configuration example in which the imaging optical system 101 according to the embodiment is applied to the imaging camera unit 40 for a surgical microscope.
  • the surgical microscope includes an eyepiece 41, an imaging optical system 42, a prism 43, a zoom system 44, and an objective system 45. This surgical microscope can be observed with the naked eye through the eyepiece 41.
  • the imaging camera unit 40 for a surgical microscope is arranged on an optical path branched by, for example, a prism 43.
  • the imaging camera unit 40 for a surgical microscope includes an imaging optical system 101 and an imaging element 100.
  • the imaging camera unit 40 for a surgical microscope is used to image the affected area through the surgical microscope.
  • Image processing using deconvolution derived from the point image distribution function is added to the image captured by the image sensor 100 in the image processing unit 110 (FIG. 6).
  • the permissible arrangement position of the BM 10 is defined by the conditional expression (1), for example, from the angle of incidence of the light beam on the aperture stop St.
  • FIG. 11 shows an outline of a central ray and a peripheral ray passing through the imaging optical system 101 according to the embodiment.
  • FIG. 12 shows an outline of a passing range of a central ray and a passing range of a peripheral ray in the optical phase modulator (BM10) of the imaging optical system 101 according to the embodiment.
  • BM10 optical phase modulator
  • the peripheral light rays are eccentrically incident on the concentric pattern region of the BM 10. Therefore, the phase modulation by the BM10 does not become concentric with respect to the peripheral rays, and the MTF changes significantly as compared with the center. In the eccentric direction, the peak value of MTF decreases at high frequencies. Assuming that the permissible value for lowering the peak value of the MTF is 70% or more at the spatial frequency where the central MTF is 10% or more and the ratio of the central MTF to the peripheral MTF is 70% or more, this permissible value is a conditional expression. It is established by satisfying (1).
  • FIG. 13 shows an example of a through-focus MTF for a plurality of spatial frequencies of the imaging optical system 101 according to the embodiment.
  • conditional expression (2) is optimal for the retardation of BM10. This is because if the upper limit of the conditional expression (2) is exceeded, the focus positions of the X-polarized light and the Y-polarized light are separated too much in the front-rear direction, and as shown in FIG. 13, the through-focus MTF becomes Futatsuyama depending on the spatial frequency. This is because it becomes. In such a state, the focus position cannot be defined in the first place, and it becomes difficult to focus by electronic calculation such as AF (autofocus). Further, if it falls below the lower limit of the conditional expression (2), it becomes difficult to exert the desired effect of BM10.
  • the focal length of the imaging optical system 101 is a medium telephoto lens of 100 mm or more in terms of 35 mm. Satisfying the conditional expression (3) corresponds to the imaging optical system 101 being such a medium telephoto lens.
  • h / f2 ⁇ 0.50 ...... (3)
  • h Maximum image height in the diagonal direction on the imaging surface Sip f2: The focal length of the optical system on the imaging surface Sip side of the aperture stop St of the imaging optical system 20.
  • FIG. 14 shows an outline of flare and ghost generation in the imaging optical system 101A according to the embodiment.
  • FIG. 15 shows a configuration example for suppressing the generation of flare and ghost in the imaging optical system 101B according to the embodiment.
  • the imaging optical system 101A shown in FIG. 14 shows, for example, a configuration example applied to the endoscope camera head 30.
  • An endoscope cover glass 33 and a camera head cover glass 34 are arranged on the object side of the imaging optical system 101A.
  • the camera head cover glass 34 is tilted.
  • the optical filter FL and the seal glass SG are arranged on the optical path between the image pickup optical system 20 and the image pickup element 100.
  • the flat plate-shaped BM10 is vertically arranged (not inclined) with respect to the optical axis.
  • the BM10 is tilted.
  • the configuration of the imaging optical system 101B is the same as that of the imaging optical system 101A except that the BM10 is tilted.
  • w1 The angle of incidence of the light beam formed on the image height in the short side direction of the imaging surface Sip on the aperture diaphragm St: ⁇ : the inclination angle of BM10.
  • the inclination of the BM 10 is arranged so that the inclination direction is opposite to that of the optical element such as the camera head cover glass 34 which is inclined on the object side of the BM 10.
  • Imaging optical systems 101 applied to endoscopes and surgical microscopes are telephoto lenses.
  • the lens used in these applications is preferably small, and it is desirable that the imaging optical system 101 satisfies the following conditional expression.
  • L_all / f2 ⁇ 2.5 > (5)
  • L_all Distance from the object-side surface of the lens having the most power on the object side to the imaging surface Sip in the optical system on the imaging surface Sip side from the aperture stop St
  • f2 Focus of the optical system on the imaging surface Sip side from the aperture stop St Distance (see Fig. 11)
  • the lens group on the most object side has a positive power and then the lens group having a negative power on the imaging surface Sip side of the aperture stop St. Is preferably arranged.
  • the configuration is a telephoto type, and the image pickup optical system 101 can be miniaturized.
  • FIG. 16 shows an example of the passing range of the central ray and the passing range of the peripheral rays in the optical phase modulator (BM10) when there is vignetting in the imaging optical system 101 according to the embodiment.
  • FIG. 17 shows an example of a central ray and a peripheral ray when there is vignetting in the imaging optical system 101 according to the embodiment.
  • the passing range of the peripheral light in the BM 10 becomes smaller than the passing range of the central light, and the passing range of the peripheral light is not circularly symmetric.
  • the diameter of the aperture structure is such that the light rays formed in the effective image circle have an aperture structure. It is desirable that it is sufficiently larger than the optical effective diameter when passing through.
  • the BM 10 gives two pupil functions to the image pickup optical system 20 while satisfying a predetermined condition. , It is possible to extend the depth of field while suppressing the deterioration of the resolution performance.
  • the optimum depth of field can be expanded with resolution performance comparable to that of the normal optical system 102.
  • the imaging optical system 101 according to one embodiment if appropriate ghost countermeasures are taken, it is possible to suppress adverse effects such as contrast reduction and double image, and improve image quality.
  • the imaging optical system 101 since the BM 10 does not have a complicated uneven structure, it is possible to provide a depth magnifying optical system having high medical reliability and manufacturability. By using the imaging optical system 101 according to the embodiment for a medical imaging device, it can be expected that highly accurate and efficient treatment will be possible.
  • Each of the imaging optical systems 1 to 3 according to the following Examples 1 to 3 includes an aperture aperture St, a BM10, and an imaging optical system 20 in this order from the object side toward the imaging surface Ship side.
  • An optical filter FL and a seal glass SG are arranged on an optical path between the imaging optical system 20 and the imaging surface Ship.
  • the BM10s are tilted in each of the imaging optical systems 1 and 2 according to the first and second embodiments.
  • the BM10 is not tilted.
  • the BM 10 has a first concentric pattern region A1 and a second concentric pattern region B1.
  • the imaging element 100 is arranged on the imaging surface Ship. Image processing using an inverse conversion filter is added to the image captured by the image sensor 100 in the image processing unit 110 (FIG. 6).
  • FIG. 18 schematically shows the concentric pattern region of the BM10 and the diameter of the aperture stop St in the imaging optical system 1 according to the first embodiment.
  • FIG. 19 shows the overall configuration of the imaging optical system 1 according to the first embodiment.
  • the imaging optical system 20 has the first lens G1, the second lens G2, the third lens G3, and the fourth lens in order from the object side toward the imaging surface Ship side. It is composed of a lens G4, a fifth lens G5, and a sixth lens G6.
  • the first lens G1 and the second lens G2 are joined to each other.
  • the fourth lens G4 and the fifth lens G5 are joined to each other.
  • the junction lens composed of the first lens G1 and the second lens G2 is a lens group having positive power.
  • the third lens G3 is a group of lenses having negative power.
  • [Table 1] shows the basic lens data of the imaging optical system 1 according to the first embodiment.
  • "Si” indicates a surface number meaning the i-th surface counting from the object side. The attributes of the surface are added to the surface number.
  • “G1R1” indicates the lens surface of the first lens G1 on the object side
  • “G1R2” indicates the lens surface of the first lens G1 on the imaging surface Ship side.
  • “G2R1” indicates the lens surface of the second lens G2 on the object side
  • “G2R2” indicates the lens surface of the second lens G2 on the imaging surface Ship side. The same applies to other lens surfaces and optical surfaces.
  • “Ri” indicates the radius of curvature of the i-th surface counting from the object side (unit: mm).
  • the portion where the value of "ri” is “ ⁇ ” indicates the aperture stop St, a plane, or a virtual surface.
  • “Di” indicates the distance on the upper surface of the shaft between the i-th surface and the i + 1-th surface counting from the object side (unit: mm).
  • “Ndi” indicates the refractive index of the glass material or material having the i-plane on the object side with respect to the d-line (wavelength 587.6 nm).
  • “ ⁇ di” indicates the Abbe number with respect to the d-line of the glass material or material having the i-th plane on the object side. The same applies to the lens data in the other examples thereafter.
  • the focal length (f) of the entire system, the aperture diameter (D) of the aperture stop St, and the open F value (Fno) in the imaging optical system 1 according to the first embodiment are shown.
  • the image height (IH) value is shown.
  • the radius (Ring1) of the first concentric pattern region A1 of the optical phase modulator (BM10) and the radius (Ring2) of the second concentric pattern region B1 are shown in FIG. 18) and the value of the retardation (Re) are shown.
  • FIG. 20 shows the through-focus MTF of the imaging optical system 1 according to the first embodiment.
  • FIG. 20 shows a through-focus MTF with respect to the spatial frequency (100 (Lp / mm)) in which the BM10 has the strongest influence.
  • the through-focus MTF of the imaging optical system 1 according to the first embodiment the characteristics when the image processing is not performed (with depth expansion (without image processing)) and the image processing by the inverse conversion filter are performed. The characteristics of the case (with depth expansion (with image processing)) are shown.
  • FIG. 20 shows a through-focus MTF of an optical system (without depth expansion) that does not use BM10 as a comparative example.
  • the peak of the through-focus MTF is significantly reduced as compared with the optical system in which the BM10 is not used.
  • the peak of the through focus MTF can be returned to the same level as the optical system without BM10. And the depth can be greatly expanded.
  • FIG. 21 shows the frequency characteristics of the MTF at the focus position of the imaging optical system 1 according to the first embodiment.
  • the characteristics when image processing is not performed are shown by solid lines.
  • FIG. 21 shows the frequency characteristics of the MTF of the optical system (without depth expansion) that does not use the BM10 as a comparative example.
  • FIG. 21 shows the frequency characteristics of the inverse conversion filter for applying an ideal deconvolution process for returning to the same resolution as the optical system without using the BM 10. The same applies to the frequency characteristics of the MTF in the other examples thereafter.
  • the frequency characteristic of the MTF is lower than that in the optical system not using the BM10.
  • the frequency characteristics of MTF can be substantially equal to that of the optical system without BM10. Can be returned.
  • FIG. 22 schematically shows the concentric pattern region of the BM10 and the diameter of the aperture stop St in the imaging optical system 2 according to the second embodiment.
  • FIG. 23 shows the overall configuration of the imaging optical system 2 according to the second embodiment.
  • the image pickup optical system 2 according to the second embodiment has substantially the same configuration as the image pickup optical system 1 according to the first embodiment, but the aperture diameter (D) of the aperture stop St is relative to the image pickup optical system 1 according to the first embodiment. ) Is changing.
  • the imaging optical system 2 according to the second embodiment shows that the effect of depth expansion changes by changing the diaphragm diameter of the aperture diaphragm St.
  • [Table 3] shows the basic lens data of the imaging optical system 2 according to the second embodiment.
  • [Table 4] shows the focal length (f) of the entire system, the aperture diameter (D) of the aperture stop St, and the open F value (Fno) in the imaging optical system 2 according to the second embodiment.
  • the image height (IH) value is shown.
  • the radius (Ring1) of the first concentric pattern region A1 of the optical phase modulator (BM10) and the radius (Ring2) of the second concentric pattern region B1 are shown in FIG. 22) and the value of the retardation (Re) are shown.
  • FIG. 24 shows the through-focus MTF of the imaging optical system 2 according to the second embodiment.
  • FIG. 24 shows a through-focus MTF with respect to the spatial frequency (100 (Lp / mm)) in which the BM10 has the strongest influence.
  • the through-focus MTF of the imaging optical system 2 according to the second embodiment the characteristics when the image processing is not performed (with depth expansion (without image processing)) and the image processing by the inverse conversion filter are performed. The characteristics of the case (with depth expansion (with image processing)) are shown.
  • FIG. 24 shows a through-focus MTF of an optical system (without depth expansion) that does not use BM10 as a comparative example. As shown in FIG.
  • the peak of the through-focus MTF is significantly reduced as compared with the optical system without the BM10.
  • the peak of the through focus MTF can be returned to the same level as the optical system without BM10. And the depth can be greatly expanded.
  • FIG. 25 shows the frequency characteristics of the MTF at the focus position of the imaging optical system 2 according to the second embodiment.
  • the frequency characteristic of the MTF is lowered as compared with the optical system not using the BM10.
  • the frequency characteristics of MTF can be substantially equal to that of the optical system without BM10. Can be returned.
  • FIG. 26 schematically shows a concentric pattern region of the optical phase modulator (BM10) and the diameter of the aperture stop St in the imaging optical system 3 according to the third embodiment.
  • FIG. 27 shows the configuration of the imaging optical system 3 according to the third embodiment.
  • the imaging optical system 20 has the first lens G1, the second lens G2, the third lens G3, and the fourth lens in order from the object side to the imaging surface Ship side. It is composed of a lens G4 and a fifth lens G5. Each lens is a single lens.
  • the first lens G1 is a lens group having a positive power.
  • the second lens G2 is a group of lenses having negative power.
  • [Table 5] shows the basic lens data of the imaging optical system 3 according to the third embodiment. Further, in [Table 6], the focal length (f) of the entire system, the aperture diameter (D) of the aperture stop St, and the open F value (Fno) in the imaging optical system 3 according to the third embodiment are shown. , And the image height (IH) value. Further, in [Table 6], the radius of the first concentric pattern region (Ring1) of the optical phase modulator (BM10) (see FIG. 26) and the radius of the second concentric pattern region (Ring2) (see FIG. 26). ), And the value of the retardation (Re).
  • FIG. 28 shows the through-focus MTF of the imaging optical system 3 according to the third embodiment.
  • FIG. 28 shows the through-focus MTF with respect to the spatial frequency (40 (Lp / mm)) in which the BM10 has the strongest influence.
  • the through-focus MTF of the imaging optical system 3 according to the third embodiment the characteristics when the image processing is not performed (with depth expansion (without image processing)) and the image processing by the inverse conversion filter are performed. The characteristics of the case (with depth expansion (with image processing)) are shown.
  • FIG. 28 shows a through-focus MTF of an optical system (without depth expansion) that does not use BM10 as a comparative example. As shown in FIG.
  • the peak of the through-focus MTF is significantly reduced as compared with the optical system without the BM10.
  • the peak of the through focus MTF can be returned to the same level as the optical system without BM10. And the depth can be greatly expanded.
  • FIG. 29 shows the frequency characteristics of the MTF at the focus position of the imaging optical system 3 according to the third embodiment.
  • the frequency characteristic of the MTF is lowered as compared with the optical system not using the BM10.
  • the frequency characteristics of MTF can be substantially equal to that of the optical system without BM10. Can be returned.
  • [Other numerical data of each embodiment] [Table 7] shows the values related to each of the above conditional expressions summarized for each embodiment. As can be seen from [Table 7], the conditional expressions of Examples 1 and 2 are satisfied. In Example 3, each conditional expression is satisfied except for the conditional expression (4).
  • the present technology may have the following configuration.
  • two pupil functions are given to the imaging optical system by the optical phase modulator while satisfying a predetermined condition, so that the deterioration of the resolution performance is suppressed. It is possible to extend the depth of field.
  • the optical phase modulator It is an optical element that does not have refractive power. It has an optical element substrate and a birefringent layer formed on the surface of the optical element substrate.
  • the birefringence layer has at least two or more concentric pattern regions for providing phase modulation, and the relative angle of birefringence anisotropy between two adjacent concentric pattern regions is 90 °.
  • the imaging optical system according to any one of the above [1] to [3].
  • the optical phase modulator It is an optical element that does not have refractive power. It has two optical element substrates and a birefringent layer formed between the two optical element substrates.
  • the birefringence layer has at least two or more concentric pattern regions for providing phase modulation, and the relative angle of birefringence anisotropy between two adjacent concentric pattern regions is 90 °.
  • the imaging optical system according to any one of the above [1] to [3].
  • the imaging optical system according to one. [11] The imaging optical system has a lens group having a positive power and a lens group having a negative power in order from the object side on the imaging surface side of the aperture diaphragm [1] to [10]. The imaging optical system according to any one of the above. [12] The imaging optical system according to any one of the above [1] to [11], which satisfies the following conditional expression.
  • L_all / f2 ⁇ 2.5 ?? (5)
  • L_all Distance from the object-side surface of the most powerful lens arranged on the object side to the imaging surface in the optical system on the imaging surface side of the aperture diaphragm
  • f2 Focal length of the optical system on the imaging surface side from the aperture diaphragm And.
  • Imaging optical system according to any one of the above [1] to [13], which is configured as an optical system for a camera head of a rigid endoscope.
  • Imaging optics and Includes an image sensor arranged at the imaging position by the image pickup optical system.
  • the imaging optical system is Aperture aperture and An imaging optical system that forms an image toward the imaging surface of the image sensor, It is composed of a substance having a birefringence and includes an optical phase modulator that gives two pupil functions to the imaging optical system.
  • An image pickup device that satisfies the following conditional expression.

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