WO2012169369A1 - 光学ユニットおよび内視鏡 - Google Patents
光学ユニットおよび内視鏡 Download PDFInfo
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- WO2012169369A1 WO2012169369A1 PCT/JP2012/063433 JP2012063433W WO2012169369A1 WO 2012169369 A1 WO2012169369 A1 WO 2012169369A1 JP 2012063433 W JP2012063433 W JP 2012063433W WO 2012169369 A1 WO2012169369 A1 WO 2012169369A1
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- Prior art keywords
- image plane
- image
- optical unit
- formula
- coating surface
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- 230000003287 optical effect Effects 0.000 title claims abstract description 129
- 238000000576 coating method Methods 0.000 claims abstract description 34
- 239000011248 coating agent Substances 0.000 claims abstract description 33
- 238000003384 imaging method Methods 0.000 claims abstract description 26
- 238000010521 absorption reaction Methods 0.000 claims abstract description 13
- 238000005286 illumination Methods 0.000 claims description 9
- 230000001225 therapeutic effect Effects 0.000 claims description 2
- 238000003698 laser cutting Methods 0.000 abstract 2
- 230000000737 periodic effect Effects 0.000 description 17
- 239000006059 cover glass Substances 0.000 description 12
- 230000000694 effects Effects 0.000 description 9
- 230000004048 modification Effects 0.000 description 7
- 238000012986 modification Methods 0.000 description 7
- 238000011282 treatment Methods 0.000 description 6
- 238000003780 insertion Methods 0.000 description 4
- 230000037431 insertion Effects 0.000 description 4
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000007888 film coating Substances 0.000 description 1
- 238000009501 film coating Methods 0.000 description 1
- 238000013532 laser treatment Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000002310 reflectometry Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
Images
Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
- A61B1/00002—Operational features of endoscopes
- A61B1/00004—Operational features of endoscopes characterised by electronic signal processing
- A61B1/00006—Operational features of endoscopes characterised by electronic signal processing of control signals
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
- A61B1/00064—Constructional details of the endoscope body
- A61B1/00071—Insertion part of the endoscope body
- A61B1/0008—Insertion part of the endoscope body characterised by distal tip features
- A61B1/00096—Optical elements
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
- A61B1/00163—Optical arrangements
- A61B1/00186—Optical arrangements with imaging filters
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
- A61B1/00163—Optical arrangements
- A61B1/00188—Optical arrangements with focusing or zooming features
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
- A61B1/04—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor combined with photographic or television appliances
- A61B1/05—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor combined with photographic or television appliances characterised by the image sensor, e.g. camera, being in the distal end portion
- A61B1/051—Details of CCD assembly
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0002—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network
- A61B5/0031—Implanted circuitry
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- 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
- G02B23/243—Objectives for endoscopes
-
- 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
- G02B27/0018—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means for preventing ghost images
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/18—Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
- G02B5/208—Filters for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
Definitions
- the present invention relates to an optical unit and an endoscope having the optical unit.
- Endoscope is used for observation inside the subject that cannot be observed from the outside.
- a CCD Charge-Coupled Device
- an optical unit imaging optical system
- the CCD has a relatively high sensitivity to infrared light
- an optical unit having an infrared light cut filter is used to perform proper color reproduction.
- endoscopes are used not only for observation but also for treatment.
- the affected part is excised with a laser.
- the reflected light from the treatment site is so strong that it cannot be cut sufficiently with the infrared light cut filter, and the observation screen becomes extremely bright, making it difficult to observe the subject image. May be.
- a laser light cut filter for cutting (blocking) the therapeutic laser light is arranged in the optical unit.
- Japanese Patent Application Laid-Open No. 2009-93198 discloses generation of a periodic pattern ghost caused by a plurality of light receiving elements constituting an imaging element being arranged in a predetermined periodic pattern in a general video camera or the like. In order to reduce this, it is disclosed to use an optical system (optical unit) having a predetermined specification.
- An object of the present invention is to provide an optical unit that reduces the occurrence of a periodic pattern ghost and an endoscope having the lens unit.
- the optical unit of the embodiment is provided with a plurality of lenses that form a subject image on an image plane that is a light receiving surface of a solid-state imaging device, an aperture stop, and the image plane side of the aperture stop.
- the distance ⁇ d between the paraxial imaging position of the ghost optical path that is reflected by the image plane and then reflected by the coating surface and reaches the image plane again satisfies the formula (1).
- An endoscope includes the optical unit, a solid-state imaging device, and an illumination optical system.
- the endoscope 30 constitutes an endoscope system 40 together with a light source device 41 and a processor 42.
- the endoscope 30 has an insertion portion 31 that is inserted into the body of a subject.
- the light source device 41 generates illumination light that illuminates the inside of the body.
- the processor 42 performs various kinds of signal processing and controls the endoscope system 40.
- a light guide fiber 45 that guides illumination light from the light source device 41 to the distal end portion 32 is inserted into the insertion portion 31 of the endoscope 30 to illuminate the inside of the body via the illumination optical system 46.
- the illumination optical system 46 shows only the object side lens.
- the processor 42 can be used as an endoscope system suitable for the purpose by combining with various endoscopes and various light source devices. Furthermore, the endoscope system 40 includes a monitor 43 that displays an endoscopic image and the like, and an input unit 44 such as a keyboard that is set by an operator.
- the endoscope 30 includes a CCD 33 that is a solid-state imaging device that captures a color endoscope image at a distal end portion 32 of an insertion unit 31 connected to an operation unit 37, a preprocess (P / P) unit 34, an A This is an electronic endoscope having a / D conversion unit 35 and a parallel / serial conversion (P / S) unit 36.
- An optical unit 10 that is an imaging optical system for forming an optical image and a CCD 33 that captures the inside of the subject's body are disposed at the distal end portion 32, and an endoscopic image captured by the CCD 33 is converted into a digital signal. To the processor 42.
- the CCD 33 has a light receiving surface (image surface) in which light receiving elements corresponding to the number of pixels are arranged in a matrix (vertical / horizontal) at a predetermined pitch (pixel pitch) p.
- the optical unit 10 includes, in order from the object side, a front lens group LF (a plano-concave first negative lens L1, a biconvex second positive lens L2), and an aperture stop BI. , A rear lens group LB which is a positive lens group (a biconvex third positive lens L3, a fourth negative lens L4 convex to the image surface side), an infrared absorption filter F, a cover glass G1, and a CCD cover glass G2. And having. The third positive lens L3 and the fourth negative lens L4, and the cover glass G1 and the CCD cover glass G2 are respectively joined.
- FI1 is a flare stop.
- the infrared absorption filter F is a parallel plate optical member that absorbs and cuts light in the infrared region. Further, a YAG laser cut film (coating) FA is disposed on the object side of the infrared absorption filter F, and an LD laser cut film (coating) FB is disposed on the image plane side.
- the YAG laser cut film FA and the LD laser cut film FB are multilayer interference films that transmit visible light and cut off specific wavelength light, that is, specific laser light outside the visible light.
- the YAG laser cut film FA cuts YAG laser light (wavelength 1060 nm) incident on the CCD 33 when treatment is performed with a YAG laser.
- the LD laser cut film FB cuts LD laser light (wavelength 810 nm) incident on the CCD 33 when treatment is performed with an LD laser.
- Each of the YAG laser cut film FA and the LD laser cut film FB has a multilayer structure, and the transmittance in a predetermined wavelength region is low due to the light interference effect, but on the other hand, the reflection of light of other wavelengths is reflected. Due to the high rate, strong reflection occurs on the coating surface.
- a part of the light incident on the CCD 33 is reflected by the light receiving surface (image surface). Since a plurality of light receiving elements are regularly arranged in a two-dimensional manner on the light receiving surface of the CCD 33, the reflected light is two-dimensionally expressed as a first-order light, a second-order light,. A plurality of specific directions result in bright diffracted light. When this diffracted light is reflected again on the coating surface and enters the CCD 33, a periodic pattern ghost is generated.
- the optical unit 10 since the diffracted light from the CCD 33 is strongly reflected by the laser cut films FA and FB having high reflectivity in the visible light region, the optical unit 10 has a periodic pattern in which a plurality of circular ghosts are regularly arranged in the vertical and horizontal directions. ghost is likely to occur.
- the reason why the individual ghost shapes constituting the periodic pattern ghost are circular is that the shape of the aperture stop BI is imaged. That is, a periodic pattern ghost is generated by the positional relationship between the aperture stop BI, the light receiving surface (image surface) of the CCD 33, and the coating surface of the laser cut film. In other words, with the aperture stop BI as an object point, a periodic pattern is formed by the imaging relationship of a ghost optical path in which light rays emitted from the aperture stop BI are reflected on the image plane and then reflected on the coating surface and reach the image plane again. A ghost occurs.
- the light beam emitted from the aperture stop BI is reflected by the image surface of the CCD 33, and further reflected by the coating surface (YAG laser cut film FA and LD laser cut film FB), and again the image surface.
- the amount of light in the ghost optical path that reaches is likely to increase.
- the periodic pattern ghost is not only a sense of incongruity for the user compared with a normal ghost or flare, but also occurs in a relatively wide range, which causes a problem in observation.
- the periodic pattern ghost is simply referred to as a ghost.
- the optical unit 10 of the endoscope 30 unlike a general video camera or the like, strong light is often generated on the imaging screen, that is, strong light is often incident on the image plane of the CCD 33.
- the optical unit 10 has the illumination optical system 46 for illuminating the inside of the body cavity.
- strong light is generated on the screen. That is, since the endoscope 30 has the illumination optical system 46, strong light is likely to enter the optical unit 10.
- r is the radius of curvature of each surface
- d is the thickness or air spacing of each optical member
- n is the refractive index of each optical member at the e-line
- ⁇ is the Abbe number of each optical member at the e-line
- FNO is F number is shown.
- the unit of r and d is mm.
- FNO 7.794, half angle of view is 81.27 degrees, maximum image height IH is 1.226 mm, pixel bitch p is 0.0032 mm (3.2 ⁇ m), and the diameter Ds of the aperture stop BI is 0. .426 mm, the difference ⁇ d between the image plane and the paraxial imaging position in the ghost optical path is ⁇ 10.13 mm (FA), ⁇ 9.7 mm (FB), and the paraxial coupling magnification ⁇ is 1.795 (FA, FB) ),
- the rear lens group RL is a positive lens group, and its focal length f1 is 4.09 mm.
- the optical unit 10 of the first embodiment had the coatings FA and FB on both sides of the infrared absorption filter F.
- the optical unit 10a of the endoscope 30a of Modification 1 shown in FIG. 4 has the laser cut film FA only on the object side of the infrared absorption filter F.
- the optical unit 10b of the endoscope 30b of Modification 2 shown in FIG. 5 has a laser cut film FA only on the image plane side of the infrared absorption filter F.
- the optical unit 10A of the endoscope 30A includes, in order from the object side, the front lens group FL (a plano-concave first negative lens L1 and a convex on the image plane side).
- a sixth negative lens L6) convex to the image surface side, an infrared absorption filter F1, a filter F2, a cover glass G1, and a CCD cover glass G2.
- the fifth positive lens L5 and the sixth negative lens L6, and the cover glass G1 and the CCD cover glass G2 are respectively joined.
- FI1 to FI4 are flare stops.
- the LD laser light cut film FA is formed on the object side of the filter F2, and the YAG laser light cut film FB is formed on the image plane side.
- the third positive lens L3 is movable in the optical axis direction and performs focusing.
- FNO is 8.023 (at the far point focus) to 7.733 (at the near point focus), and the half angle of view is 71.61 degrees (at the far point focus) to 71.25 degrees (at the near point focus).
- the maximum image height IH is 1.604 mm
- the pixel pitch p is 2.8 ⁇ m
- the diameter Ds of the brightness stop BI is 0.514 mm
- the difference ⁇ d between the image plane and the paraxial imaging position in the ghost optical path is ⁇ 10 .69 mm (FA, far point focus and near point focus), -10.19 mm (FB, far point focus and near point focus)
- paraxial coupling magnification ⁇ is 1.628 (FA, FB)
- the rear lens group RL is a positive lens group, and its focal length f1 is 2.86 mm.
- the optical unit 10B of the endoscope 30B includes, in order from the object side, a front lens group FL (a plano-concave first negative lens L1) and an infrared absorption filter.
- F1 a second positive lens L2 convex toward the object side, an aperture stop BI, a rear lens group RL (a biconvex third positive lens L3, a biconvex fourth positive lens L4, and an image plane side)
- a convex fifth negative lens L5 A convex fifth negative lens L5
- a filter F2 a cover glass G1, and a CCD cover glass G2.
- the fourth positive lens L4 and the fifth negative lens L5, and the cover glass G1 and the CCD cover glass G2 are respectively joined.
- FI1 to FI5 are flare stops.
- An LD laser light cut film FA is formed on the object side of the filter F2, which is a transparent parallel plate, and a YAG laser light cut film FB is formed on the image plane side.
- the second positive lens L2 is movable in the optical axis direction and performs focusing.
- FNO is 7.872 (at the far point focus) to 7.582 (at the near point focus), and the half angle of view is 77.51 degrees (at the far point focus) to 73.29 degrees (at the near point focus).
- the maximum image height IH is 1.486 mm
- the pixel pitch p is 0.00265 mm (2.65 ⁇ m)
- the diameter Ds of the aperture stop BI is 0.478 mm
- the difference between the image plane and the paraxial imaging position in the ghost optical path ⁇ d is ⁇ 9.93 mm (FA, during far point focus and near point focus), ⁇ 8.85 mm (FB, during far point focus and near point focus), and paraxial coupling magnification ⁇ is 1.554 ( FA, FB)
- the rear lens group RL is a positive lens group
- its focal length f1 is 2.33 mm.
- the optical unit reflects the light emitted from the F number FNO, the maximum image height IH, and the brightness stop BI on the image plane, and further reflects on the coating surface and returns to the image plane again.
- the distance ⁇ d between the paraxial imaging position of the ghost optical path to reach and the image plane needs to satisfy (Equation 1).
- the optical unit preferably makes the ghost inconspicuous by setting the position of the ghost on the same side of the light source image that caused the ghost and the screen center point. Furthermore, it is preferable to disperse the amount of ghost light by enlarging and forming a large image of individual ghosts constituting the periodic pattern ghost.
- the optical unit reflects the maximum image height IH, the diameter Ds of the aperture stop BI, and the light beam emitted from the aperture stop BI on the image plane, and further reflects on the coating surface and returns to the image plane again.
- the paraxial lateral magnification ⁇ of the arriving ghost optical path preferably satisfies (Equation 2).
- the paraxial lateral magnification ⁇ that satisfies the above equation is a positive value.
- the paraxial lateral magnification ⁇ is a positive value (+)
- the ghost occurs on the same side of the light source image and the screen center point that caused the ghost
- the paraxial lateral magnification ⁇ is negative.
- the value (-) occurs on the opposite side across the screen center point.
- the optical unit can appropriately set the in-focus position and the magnification simultaneously.
- the optical unit 10 satisfy
- the reflection angle of the diffracted light from the image surface of the CCD 33 depends on the pixel pitch p.
- the rear lens group RL is a positive lens group, and it is further preferable that a coating surface is disposed on the image plane side with respect to the rear lens group RL. It is preferable that the distance D1 from the BI to the coating surface and the pixel pitch p of the image sensor satisfy (Equation 5).
- an optical unit in which a parallel plate is disposed on the image plane side from the aperture stop BI and the coating surface of the laser cut film is provided only on the surface of the parallel plate is preferable because the above problem does not occur.
- the optical unit preferably has an infrared absorption filter F.
- the laser cut film has a large change in the imaging magnification (paraxial lateral magnification ⁇ ) and in-focus position of the ghost optical path. Since it does not give, it is preferable.
- the optical unit having the laser cut film FB also has the same effect as the optical unit 10a or the optical unit 10b.
- the effect of the present invention can be obtained if at least ⁇ Condition 1> is satisfied, but it is particularly preferable to satisfy ⁇ Condition 2> at the same time.
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Abstract
Description
また、別の実施形態の内視鏡は、上記光学ユニットと、固体撮像素子と、照明光学系と、を具備する。
最初に第1実施形態の光学ユニット10および光学ユニット10を具備する内視鏡30について説明する。図1に示すように、内視鏡30は、光源装置41およびプロセッサ42とともに、内視鏡システム40を構成している。内視鏡30は被検者の体内に挿入される挿入部31を有する。光源装置41は体内を照明する照明光を発生する。プロセッサ42は、各種の信号処理を行うとともに、内視鏡システム40の制御を行う。
<第1実施形態の変形例>
第1実施形態の光学ユニット10は、赤外吸収フィルタFの両面にコーティングFAおよびFBを有していた。これに対して、図4に示す変形例1の内視鏡30aの光学ユニット10aは、赤外吸収フィルタFの物体側にのみレーザーカット膜FAを有する。また、図5に示す変形例2の内視鏡30bの光学ユニット10bは、赤外吸収フィルタFの像面側にのみレーザーカット膜FAを有する。
図6および図7に示すように、第2実施形態の内視鏡30Aの光学ユニット10Aは、物体側から順に、前レンズ群FL(平凹の第1負レンズL1と、像面側に凸の第2正レンズL2と、物体側に凸の第3正レンズL3)と、明るさ絞りBIと、後レンズ群RL(両凸の第4正レンズL4と、両凸の第5正レンズL5と、像面側に凸の第6負レンズL6)、赤外吸収フィルタF1と、フィルタF2と、カバーガラスG1と、CCDカバーガラスG2と、を有する。第5正レンズL5と第6負レンズL6、および、カバーガラスG1とCCDカバーガラスG2は、それぞれ接合されている。また、FI1~FI4はフレア絞りである。
<第3実施形態>
図8および図9に示すように、第3実施形態の内視鏡30Bの光学ユニット10Bは、物体側から順に、前レンズ群FL(平凹の第1負レンズL1)と、赤外吸収フィルタF1と、物体側に凸の第2正レンズL2と、明るさ絞りBIと、後レンズ群RL(両凸の第3正レンズL3と、両凸の第4正レンズL4と、像面側に凸の第5負レンズL5)と、フィルタF2と、カバーガラスG1と、CCDカバーガラスG2と、を有する。第4正レンズL4と第5負レンズL5、およびカバーガラスG1とCCDカバーガラスG2は、それぞれ接合されている。また、FI1~FI5はフレア絞りである。
ゴーストの合焦位置を像面から離れた位置とすること、すなわち、ゴーストを、いわゆる「ピンぼけ」とすることで、ゴースト光を拡散することが最も重要である。このために、光学ユニットは、FナンバーFNO、最大像高IH、および、前記明るさ絞りBIから発した光線が前記像面で反射して、さらに前記コーティング面で反射して再び前記像面に到達するゴースト光路の近軸結像位置と前記像面との距離Δd、が、(式1)を満足する必要がある。
(式1)の上限未満であれば光学ユニットの全長が長くなることがなく、下限を超えているとゴーストが非合焦状態であるため、視認性が悪化することがなく、小さい患部との認識間違いなどがない。
0.90<|FNO・IH/Δd|<1.4 (式1B)
<条件2>
次に、光学ユニットは、ゴーストの画面上の位置を、ゴーストの原因となった光源像と画面中心点をはさんで同じ側とすることで、ゴースト目立たなくすることが好ましい。さらに、周期パターンゴーストを構成する個々のゴーストを、拡大して大きく結像することで、ゴーストの光量を分散させることが好ましい。
上式の上限未満であれば、光学ユニットの全長が長くなったり、レンズの加工性が悪くなったりすることがない。上式の下限を超えていれば、像面におけるゴーストは、倍率が大きいため、光度が弱く目立ちにくい。
0.35<β・Ds/IH<0.7 (式2B)
特に、<条件1>と<条件2>とを満たすことにより、光学ユニットは、合焦位置と倍率とを同時に適切に設定することができる。
さらに光学ユニットは、コーティング面から像面までの距離D2、および明るさ絞りBIよりも像面側に配置された後レンズ群RLの焦点距離f1が、(式3)を満足することが好ましい。
上式の上限未満であれば、光学ユニットの全長が長くなることがなく、下限を超えていれば非合焦状態のため、ゴーストが目立つことがなく、かつ、バックフォーカスが小さくなりすぎることがないため、ピント調整ができなくなってしまうことがない。
0.50<D2/f1<1.1 (式3B)
<条件4>
さらに光学ユニットは、明るさ絞りBIから像面までの距離D、および、明るさ絞りBIからコーティング面までの距離D1が、(式4)を満足することが好ましい。
上式の範囲内であれば、回折光が像面に戻りにくいため、ゴーストが発生しにくい。
なお、光学ユニットは、前記効果がより顕著となるため、(式4A)を満たすことが、より好ましく、(式4B)を満たすことが特に好ましい。
0.50<D1/D<0.72 (式4B)
<条件5>
CCD33の像面からの回折光の反射角度は、画素ピッチpに依存する。このため、さらに光学ユニットは、後レンズ群RLが正レンズ群であることが好ましく、さらに、後レンズ群RLよりも像面側にコーティング面が配置されていることが好ましく、さらに、明るさ絞りBIからコーティング面までの距離D1および撮像素子の画素ピッチpが、(式5)を満足することが好ましい。
上式の範囲内であれば、回折光が像面に戻ることがなく、ゴーストが発生しない。
0.9<D1/(p×1000)<1.8 (式5B)
<条件5>
コーティング面がある平行平板を、明るさ絞りBIの物体側に配置した光学ユニットでは、CCD33の反射光による周期パターンゴーストを防ぐごとができるが、逆に光学面同士の反射等による通常のゴーストが発生しやすくなる。さらに、画角が大きい光学ユニットでは、明るさ絞りBIよりも物体側の光線はコーティング面への入射角度が大きくなる傾向があり、レーザーカット膜の角度特性によってレーザー光のカット率が低下してしまうこともある。
(表4)に示すように、実施形態の光学ユニット10、10A、10Bおよび変形例の光学ユニット10a、10bは、いずれも(式1)~(式5)等を満たしているため、周期パターンゴーストの発生が軽減されていた。それぞれが光学ユニット10、10A、10Bまたは変形例の光学ユニット10a、10bを具備する実施形態の内視鏡は、周期パターンゴーストにより観察が困難になることがなかった。
Claims (11)
- 被写体像を固体撮像素子の受光面である像面に結像する複数のレンズと、
明るさ絞りと、
前記明るさ絞りよりも、前記像面側に配設された、可視光を透過し特定の波長光をカットする多層干渉膜が成膜されたコーティング面のある光学部材と、を具備し、
FナンバーFNO、最大像高IH、および、前記明るさ絞りから発した光線が前記像面で反射して、さらに前記コーティング面で反射して再び前記像面に到達するゴースト光路の近軸結像位置と前記像面との距離Δd、が、(式1)を満足することを特徴とする光学ユニット。
0.75<|FNO・IH/Δd|<2.0 (式1) - 前記最大像高IH、前記明るさ絞りの径Ds、および前記ゴースト光路の近軸横倍率βが、(式2)を満足することを特徴とする請求項1に記載の光学ユニット。
0.1<β・Ds/IH<1.2 (式2) - 前記明るさ絞りよりも前記像面側に配置された後レンズ群の焦点距離f1、および、前記コーティング面から前記像面までの距離D2が、(式3)を満足することを特徴とする請求項2に記載の光学ユニット。
0.40<D2/f1<1.5 (式3) - 前記明るさ絞りから前記像面までの距離D、および、前記明るさ絞りから前記コーティング面までの距離D1が、(式4)を満足することを特徴とする請求項3に記載の光学ユニット。
0.20<D/D1<0.75 (式4) - 前記明るさ絞りよりも前記像面側に配置された複数のレンズからなる後レンズ群が正レンズ群であり、
前記後レンズ群よりも前記像面側に前記コーティング面があり、
前記明るさ絞りから前記コーティング面までの距離D1および前記撮像素子の画素ピッチpが、(式5)を満足することを特徴とする請求項4に記載の光学ユニット。
0.20<D1/(p×1000)<2.5 (式5) - 前記光学部材が前記明るさ絞りよりも前記像面側に配置された平行平板であり、前記平行平板にのみ前記コーティング面があることを特徴とする請求項5に記載の光学ユニット。
- 前記光学部材の両面に、それぞれ、カットする光の波長が異なる多層干渉膜が成膜されたコーティング面があることを特徴とする請求項6に記載の光学ユニット。
- 前記光学部材が、赤外領域の光をカットする吸収側フィルタであることを特徴とする請求項7に記載の光学ユニット。
- 被写体像を固体撮像素子の受光面である像面に結像する複数のレンズと、
明るさ絞りと、
前記明るさ絞りよりも、前記像面側に配設された、可視光を透過し特定の波長光をカットする多層干渉膜が成膜されたコーティング面のある光学部材と、を具備し、
前記明るさ絞りよりも前記像面側に配置された複数のレンズからなる後レンズ群が正レンズ群であり、
前記後レンズ群よりも前記像面側に前記コーティング面があり、
FナンバーFNO、最大像高IH、および、前記明るさ絞りから発した光線が前記像面で反射して、さらに前記コーティング面で反射して再び前記像面に到達するゴースト光路の近軸結像位置と前記像面との距離Δd、前記最大像高IH、前記明るさ絞りの径Ds、および前記ゴースト光路の近軸横倍率β、前記明るさ絞りよりも前記像面側に配置された後レンズ群の焦点距離f1、および、前記コーティング面から前記像面までの距離D2、前記明るさ絞りから前記像面までの距離D、および、前記明るさ絞りから前記コーティング面までの距離D1、および前記撮像素子の画素ピッチpが、(式1B)、(式2B)、(式3B)、(式4B)、(式5B)を満足することを特徴とする光学ユニット。
0.90<|FNO・IH/Δd|<1.4 (式1B)
0.35<β・Ds/IH<0.7 (式2B)
0.50<D2/f1<1.1 (式3B)
0.50<D1/D<0.72 (式4B)
0.9<D1/(p×1000)<1.8 (式5B) - 請求項1から請求項9のいずれか1項に記載の光学ユニットと、
固体撮像素子と、
照明光学系と、を具備することを特徴とする内視鏡。 - 前記コーティング面が、治療用のレーザー光をカットすることを特徴とする請求項10に記載の内視鏡。
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