JP2010128459A - Imaging optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging optical system which images an observation image by performing switching among a plurality of observation modes, such as the plurality of observation wavelengths with different use wavelength band areas, within one optical system, and whose entire size is reduced. <P>SOLUTION: The imaging optical system for imaging an observation object has an incident-face switching optical member 1 configured such that at least two light-transmitting incident faces 11a<SB>1</SB>and 11a<SB>2</SB>provided in a direction intersecting each other are provided, each incident face can intersect the incident optical axis O of the imaging optical system and can be turned around each of shaft members A1 and A2 perpendicular to the incident optical axis O, and the incident faces intersecting the incident optical axis O are switched by turning around the corresponding shaft members A1 and A2 perpendicular to the incident optical axis O. The incident faces 11a<SB>1</SB>and 11a<SB>2</SB>are different from each other in transmission wavelength characteristics. The incident faces 11a<SB>1</SB>and 11a<SB>2</SB>have brightness diaphragms S1 and S2 having different diameters. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging optical system that captures an observation image by switching to different observation modes such as a plurality of different observation wavelengths in one optical system, and particularly relates to an imaging optical system suitable for an endoscope. is there.

  Conventionally, in an imaging optical system, an observation image is captured by switching to an observation mode of a plurality of different observation wavelengths, such as normal white light observation and special wavelength observation such as fluorescence observation, in one optical system. In this case, the filter is inserted into and removed from the imaging optical path according to the observation mode. Examples of such an imaging optical system include those described in the following Patent Documents 1 to 3.

JP 2005-58620 A JP 2002-189238 A JP 2005-348901 A

  In Patent Document 1, a switching lever for switching between a normal observation mode and a fluorescence observation mode, a removal filter for removing an excitation light wavelength component, and a removal filter according to a switching operation of the switching lever are used as an objective lens and an imaging device. An imaging optical system of an endoscope provided with an insertion / extraction mechanism that inserts / extracts into / from the optical path is described. When the switching lever is switched to the fluorescence observation mode, the removal filter is inserted into the optical path via the insertion / extraction mechanism. When the switching lever is switched to the normal observation mode, the removal filter is pulled out from the optical path.

  In Patent Document 2, an optical filter that blocks or transmits light according to a wavelength is provided in at least one of a planar filter fixing plate having two openings in a lens barrel of a CCTV camera lens. As a filter driving means for inserting / removing the optical filter into / from the optical path, a configuration including a filter galvanometer for reciprocating a filter fixing plate is described. By rotating the filter galvanometer, the infrared cut filter is inserted and removed from the optical path in the lens barrel.

  Further, in Patent Document 3, a filter mounting plate that is rotatably arranged around an axis on an imaging optical path between an imaging lens and an imaging device, and a filter mounting plate that is attached to the filter mounting plate and selectively on the imaging optical path. There is described an imaging optical system of an endoscope apparatus that includes a visible light filter and an absorption light filter that are set so as to be capable of being arranged, and a switching lever that operates a filter mounting plate outside the filter. By operating the switching lever, one of the visible light filter and the absorbed light filter attached to the filter mounting plate is arranged on the imaging optical path.

  However, in any of the imaging optical systems described in Patent Documents 1 to 3, a space for retracting a filter for insertion into and removal from the optical path according to the observation mode in the direction perpendicular to the imaging optical path is required. The entire apparatus including the imaging optical system becomes large, and this increases the burden on the human body particularly in an endoscope including the imaging optical system in an insertion portion that requires a reduction in diameter. End up.

  The present invention has been made in view of the above-described conventional problems, and in one optical system, an observation image can be taken by switching to a plurality of different observation modes such as a plurality of observation wavelengths having different use wavelength bands, An object of the present invention is to provide an imaging optical system capable of downsizing the entire apparatus.

  In order to achieve the above object, an imaging optical system according to the present invention has at least two incident surfaces provided in directions intersecting with each other and capable of transmitting light in an imaging optical system for imaging an observation target. The incident surface can intersect the incident optical axis of the imaging optical system, and can rotate about an axis perpendicular to the incident optical axis of the imaging optical system, with respect to the incident optical axis of the imaging optical system And an incident surface switching optical member configured to switch the incident surface intersecting the incident optical axis of the imaging optical system by being rotated about a vertical axis.

  In the incident surface switching imaging optical system of the present invention, it is preferable that the at least one incident surface has optical characteristics different from those of the other incident surfaces.

  In the imaging optical system of the present invention, it is preferable that the incident surfaces have different optical characteristics.

  In the imaging optical system of the present invention, it is preferable that the at least one incident surface has a transmission wavelength characteristic different from other incident surfaces.

  In the imaging optical system of the present invention, it is preferable that the respective incident surfaces have different transmission wavelength characteristics.

  In the imaging optical system of the present invention, it is preferable that the incident surface switching optical member includes an aperture stop on each incident surface.

  In the imaging optical system of the present invention, it is preferable that the at least one brightness stop has a diameter different from that of other brightness stops.

  In the imaging optical system of the present invention, it is preferable that the respective aperture stops have different diameters.

  In the imaging optical system of the present invention, it is preferable that the incident surface switching optical member has a transparent column body whose bottom surface is formed in a quadrilateral, hexagonal or octagonal shape.

  Further, in the imaging optical system according to the present invention, the transparent column body is separated from each incident surface so that the air conversion length in the optical axis direction changes each time the incident surface intersecting the incident optical axis of the imaging optical system is switched. It is preferable that the thickness of the glass material up to the emission surface is different.

  Further, in the imaging optical system of the present invention, the entrance surface switching optical member includes a prismatic frame member having a bottom, a quadrilateral, a hexagonal shape, or an octagonal outline, and side portions of the frame member. It is preferable to have at least two parallel flat plates provided in different frames.

  In the imaging optical system of the present invention, the at least two parallel plates are thick so that the air conversion length in the optical axis direction changes each time the incident surface intersecting the incident optical axis of the imaging optical system is switched. It is preferable that they are formed differently.

  In the imaging optical system of the present invention, it is preferable that each of the incident surfaces is formed in a planar shape.

  In the imaging optical system of the present invention, it is preferable that each of the incident surfaces is formed in a curved shape.

  In the imaging optical system of the present invention, the incident surface switching optical member is configured such that an incident surface intersecting the incident optical axis of the imaging optical system can be tilted at a desired angle with respect to the incident optical axis. It is preferable.

  According to the present invention, there is provided an imaging optical system capable of imaging an observation image by switching to a plurality of different observation modes such as a plurality of observation wavelengths having different use wavelength bands within one optical system and miniaturizing the entire apparatus. can get.

Prior to the description of the embodiments, the effects of the present invention will be described in detail.
The imaging optical system of the present invention has at least two incident surfaces that are provided in directions intersecting each other and capable of transmitting light, and each incident surface can intersect the incident optical axis of the imaging optical system, The optical axis can be rotated about an axis perpendicular to the incident optical axis of the optical system, and can be rotated about an axis perpendicular to the incident optical axis of the imaging optical system. And an incident surface switching optical member configured to switch the incident surface intersecting with.
In this way, by configuring at least two incident surfaces of the incident surface switching optical member with different optical characteristics, there is no space for retracting a filter or the like in the direction perpendicular to the imaging optical path. In one optical system, it is possible to switch to a plurality of different observation modes, such as a plurality of observation wavelengths having different use wavelength bands, to take an observation image, and to reduce the size of the entire apparatus.

In the imaging optical system of the present invention, it is preferable that at least one incident surface of the incident surface switching optical member is different in optical characteristics from other incident surfaces. Alternatively, it is preferable that the respective incident surfaces of the incident surface switching optical member have different optical characteristics. More specifically, for example, it is preferable that at least one incident surface of the incident surface switching optical member has a transmission wavelength characteristic different from other incident surfaces. Alternatively, it is preferable that the respective incident surfaces of the incident surface switching optical member have different transmission wavelength characteristics.
In this way, by switching the incident surface intersecting the incident optical axis of the imaging optical system in the incident surface switching optical member, the observation image is captured by switching to a plurality of observation modes having different optical characteristics such as different observation wavelengths. can do.

In the imaging optical system of the present invention, it is preferable that the incident surface switching optical member includes an aperture stop on each incident surface. Further, it is preferable that at least one brightness stop has a diameter different from that of other brightness stops. Alternatively, it is preferable that each aperture stop has a different diameter.
For example, since fluorescence has a weak light intensity and an observation image tends to be dark, it is necessary to capture the fluorescence as much as possible by increasing the diameter of the aperture stop as much as possible when capturing the fluorescence observation image. On the other hand, normal white light has a strong light intensity and the observation image tends to be too bright. Therefore, when taking an observation image with normal white light, the diameter of the aperture stop is larger than that for fluorescence observation. Therefore, it is necessary to cut a predetermined amount of white light so that the brightness is reduced to an appropriate brightness.
Thus, if the wavelength used for imaging differs, it may be necessary to vary the diameter of the aperture stop each time in order to adjust the amount of light accordingly.
However, if an aperture stop with a different diameter is integrally provided on each entrance surface of the entrance surface switching optical member, it is not necessary to change the diameter of the aperture stop every time the observation wavelength is switched, and the amount of light adjustment is saved. be able to.

In the imaging optical system of the present invention, it is preferable that the incident surface switching optical member has a transparent column body whose bottom surface is formed in a quadrilateral, hexagonal or octagonal shape.
If the incident surface switching optical member is configured to have a transparent column having a bottom surface formed in a square shape, an observation image can be picked up by switching between two types of observation wavelengths. If the entrance surface switching optical member is configured to have a transparent column having a hexagonal or octagonal bottom surface, an observation image can be picked up by switching between three or four types of observation wavelengths. .

Further, in the imaging optical system of the present invention, the transparent column body constituting the incident surface switching optical member has a different air conversion length in the optical axis direction every time the incident surface intersecting the incident optical axis of the imaging optical system is switched. In addition, it is preferable that the thickness of the glass material from each entrance surface to the exit surface is different.
In general, a lens has the property that the observation image is formed at different positions when the observation wavelength is different.In the imaging optical system, if the observation image is observed by switching to a different observation wavelength, the axial chromatic aberration The image formation position is easily misaligned under the influence of.
For this reason, in the transparent column body constituting the incident surface switching optical member, when the thickness of the glass material from each incident surface to the exit surface is the same, the incident surface intersecting the incident optical axis of the imaging optical system is switched. If different observation wavelengths are emitted, the observation image may be blurred on the imaging surface depending on the observation wavelength used.
However, the transparent column body constituting the incident surface switching optical member is changed from each incident surface to the exit surface so that the air conversion length in the optical axis direction changes every time the incident surface intersecting the incident optical axis of the imaging optical system is switched. If the glass materials are formed with different thicknesses, it is possible to correct the imaging position and form observation images with different observation wavelengths emitted from the incident surface switching optical member at the same imaging position. The blur can be eliminated.

In the imaging optical system of the present invention, the entrance surface switching optical member includes a prismatic frame member whose bottom contour is formed in a quadrilateral, hexagonal or octagonal shape, and different frames on the sides of the frame member. It is preferable to be configured to have at least two parallel flat plates.
If it does in this way, an existing filter can be used for a parallel plate, and manufacturing cost can be reduced.
If the entrance surface switching optical member is configured to include a prismatic frame member having a rectangular outline at the bottom, a filter having different wavelength characteristics is provided on each of two different frames on the side of the frame member. An observation image can be taken by switching to two types of observation wavelengths. If the entrance surface switching optical member is configured to include a prismatic frame member whose bottom contour is formed in a hexagonal shape or an octagonal shape, three or four different side portions of the frame member are provided. By providing filters with different wavelength characteristics on the frames, it is possible to switch to three different types or four types of observation wavelengths to capture observation images.

Note that at least two parallel flat plates constituting the incident surface switching optical member have different thicknesses so that each time the incident surface intersecting the incident optical axis of the imaging optical system is switched, the air conversion length in the optical axis direction is different. Is preferably formed.
As described above, in general, a lens has a property that an imaging position of an observation image is different when an observation wavelength is different. In an imaging optical system, an observation image is observed by switching to an observation wavelength whose use wavelength band is greatly different. As a result, the imaging position is easily shifted due to the influence of axial chromatic aberration.
For this reason, if the thickness of at least two parallel flat plates constituting the incident surface switching optical member is the same, a different observation wavelength is emitted each time the incident surface intersecting the incident optical axis of the imaging optical system is switched. When configured as above, the observation image is blurred on the imaging surface depending on the observation wavelength used.
However, if at least two parallel flat plates constituting the incident surface switching optical member are formed with different thicknesses so that the air conversion length in the optical axis direction changes each time the incident surface is switched, the imaging position is corrected. As a result, observation images of different observation wavelengths emitted from the incident surface switching optical member can be formed at the same imaging position, and blurring of the observation image can be eliminated.

  In the imaging optical system of the present invention, each incident surface of the incident surface switching optical member is preferably formed to be a flat surface. If it forms in a plane, processing of an entrance plane switching optical member will become easy. Further, it is easy to assemble the incident surface switching optical member into the imaging optical system at the time of manufacture.

  In the imaging optical system of the present invention, each incident surface of the incident surface switching optical member may be formed in a curved surface shape. In this way, a part of the power of the other optical member in the imaging optical system can be shared by each incident surface of the incident surface switching optical member, and the aberration is corrected by reducing the curvature of the other optical member. Or the optical path length of the entire imaging optical system can be shortened.

In the imaging optical system of the present invention, it is preferable that the incident surface switching optical member is configured such that an incident surface intersecting with the incident optical axis of the imaging optical system can be inclined at a desired angle with respect to the incident optical axis. .
Generally, the filter has a property that the transmittance characteristic shifts to the short wavelength side as the incident angle is changed to be larger. For this reason, the incident surface switching optical member configured with the filter surface having different wavelength transmission characteristics for each incident surface has the incident surface intersecting the incident optical axis of the imaging optical system at a desired angle with respect to the incident optical axis. When configured to be tiltable, the transmittance characteristics of the filter can be changed, and the observation wavelength can be adjusted and optimized in a desired observation mode. Further, it is possible to widen the wavelength band that can correspond to the excitation / fluorescence wavelength on one incident surface.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First Embodiment FIG. 1 is an explanatory view showing a schematic configuration of an imaging optical system according to a first embodiment of the present invention in a cross section along the optical axis, and (a) is in a WLI (white light imaging) mode. (B) is a diagram showing the state switched to the AFI (auto-fluorescence imaging) mode, respectively. 2 is an explanatory view of the incident surface switching optical member of the imaging optical system of FIG. 1 as viewed from the object side. FIG. 2A is a diagram showing a state when the first incident surface is switched in a direction orthogonal to the incident optical axis. (B) is a figure which shows a state when the 2nd entrance plane is switched to the direction orthogonal to an incident optical axis. 3 is a graph showing the transmission wavelength characteristic of the incident surface of the incident surface switching optical member of the imaging optical system of FIG. 1, and (a) is the transmission wavelength characteristic when the first incident surface is constituted by an infrared cut filter surface. (B) is a graph showing the transmission wavelength characteristics when the second entrance surface is configured by an excitation cut filter surface, (c) is the transmission wavelength of the entrance surface of the entrance surface switching optical member according to a modification. It is a graph which shows a characteristic, and is a graph which shows the transmission wavelength characteristic when a 2nd entrance plane is comprised by the narrow-band transmission filter surface.

  The imaging optical system of the first embodiment includes a first group G1, an incident surface switching optical member 1, and a second group G2 in order from the object side. In FIG. 1, FS is a field stop, CG is a cover glass, and IM is an image sensor.

The incident surface switching optical member 1 is configured to have a rectangular parallelepiped transparent column body 11 whose bottom surfaces 11c ₁ and 11c ₂ are formed in a square shape. The transparent column 11 has a first incident surface 11a ₁ , a second incident surface 11a ₂ , a first exit surface 11b _1, and a second exit surface 11b ₂ as side surfaces of a rectangular parallelepiped. .
The first incident surface 11a ₁ and the second incident surface 11a ₂ are provided so as to cross each other.

Further, the incident surface switching optical member 1 has shaft members A1 and A2 fixed on axes orthogonal to the incident optical axis O of the imaging optical system at the centers of the rectangular parallelepiped bottom surfaces 11c ₁ and 11c _2. ing. The shaft members A1 and A2 are rotatably supported by a shaft support portion (not shown) and are rotated via a rotation drive member (not shown).
The incident surface switching optical member 1 is rotated about the shaft members A1 and A2, so that the incident surface intersecting the optical axis O of the imaging optical system is the first incident surface 11a ₁ or the second incident surface 11a ₁ . so that the switching to the incident surface 11a _2.

As shown in FIG. 3A, the first incident surface 11a ₁ transmits infrared light having a visible wavelength band of 390 nm to 710 nm and has a transmission wavelength characteristic that cuts near infrared wavelengths longer than 720 nm. It is configured as an infrared cut filter surface coated with a wavelength cut film. The first entrance surface 11a ₁ is provided with a first brightness stop S1.
As shown by the solid line in FIG. 3B, the second incident surface 11a ₂ is coated with an excitation wavelength cut film showing a transmission wavelength characteristic that cuts a wavelength shorter than 480 nm and transmits a wavelength longer than 485 nm. Further, it is configured as an excitation cut filter surface. The second entrance surface 11a ₂ is provided with a second brightness stop S2.
The first brightness stop S1 and the second brightness stop S2 are fixed in diameter with the first brightness stop S1 diameter φ1 being smaller than the diameter φ2 of the second brightness stop. .
The thickness α1 of the glass material from the first incident surface 11a ₁ to the first emission surface 11b ₁ is larger than the thickness α2 of the glass material from the second incidence surface 11a ₂ to the second emission surface 11b _2. It is thick.

In the imaging optical system of the first embodiment configured as described above, when an observation image is taken in the WLI (white light observation) mode, a rotation driving member (not shown) is driven, and the incident surface together with the shaft members A1 and A2 The switching optical member 1 is rotated so that the first incident surface 11a ₁ comes to a position orthogonal to the optical axis O as shown in FIG.
Light from an observation target (not shown) passes through the first group G1 and enters the incident surface switching optical member 1. The light having a diameter of φ1 that has passed through the first brightness stop S1 is incident on the first incident surface 11a ₁ . Of the light incident on the first incident surface 11a ₁ , visible light having a wavelength band of 390 nm to 710 nm is transmitted through the first incident surface 11a _1, and near infrared light having a wavelength band longer than 720 nm is Cut by _one incident surface 11a ₁ . The visible light that has passed through the first incident surface 11a ₁ exits the first exit surface 11b ₁ , enters the second group G2, passes through the cover glass CG, and forms an image on the imaging surface of the image sensor IM. .

On the other hand, when an observation image is captured in the AFI (fluorescence observation) mode, a rotation driving member (not shown) is driven, and the incident surface switching optical member 1 is rotated together with the shaft members A1 and A2, thereby FIG. As shown in FIG. 4, the second incident surface 11a ₂ is positioned at a position orthogonal to the optical axis O.
Light including an excitation wavelength and a fluorescence wavelength from an observation target (not shown) passes through the first group G1 and enters the incident surface switching optical member 1. The light having a diameter of φ2 that has passed through the second brightness stop S2 enters the second incident surface 11a ₂ . Of the light incident on the second incident surface 11a ₂ , the light in the wavelength band including the excitation light shorter than 480 nm is cut by the second incident surface 11a ₂ , and the fluorescence in the wavelength band longer than 485 nm is transmitting the second incidence plane 11a _2. The fluorescence that has passed through the second incident surface 11a ₂ exits the second exit surface 11b ₂ , enters the second group G2, passes through the cover glass CG, and forms an image on the imaging surface of the image sensor IM.

Thus, according to the imaging optical system of the first embodiment, the incident surface switching optical member 1 is centered on the shaft members A1 and A2 arranged on the axis orthogonal to the incident optical axis O of the imaging optical system. It can be rotated.
For this reason, according to the imaging optical system of the first embodiment, the optical characteristics of the _two incident surfaces 11a ₁ and 11a _{2 in} the incident surface switching optical member 1 are configured to be different from each other, thereby making the direction perpendicular to the imaging optical path. Without providing a space for retracting the filter, it is possible to switch to two different observation modes in one optical system and take an observation image.
However, in the imaging optical system of the first embodiment, the incident surfaces 11a ₁ and 11a ₂ of the incident surface switching optical member 1 have different transmission wavelength characteristics. For this reason, according to the imaging optical system of the first embodiment, switching to the white light observation mode or the fluorescence observation mode is performed by switching the incident surfaces 11a ₁ and 11a ₂ intersecting the incident optical axis O of the imaging optical system. An image can be taken.

Moreover, according to the imaging optical system of the first embodiment, the incident surface switching optical member 1 includes the aperture stops S1 and S2 having different diameters on the incident surfaces 11a ₁ and 11a ₂ , respectively. The amount of light can be adjusted at the same time as switching, and the effort of adjusting the amount of light by adjusting the diameter of the aperture stop for each switching of the observation wavelength can be saved. In the imaging optical system of the first embodiment, since the fluorescence is weak in light intensity and the observation image is likely to be dark, when the observation image is captured in the fluorescence observation mode, the diameter of the aperture stop S2 is increased as much as possible. Therefore, the fluorescence is taken in as much as possible. On the other hand, normal white light has high light intensity and the observation image tends to be too bright. Therefore, when the observation image is captured in the observation mode using normal white light, the diameter of the aperture stop S1 is set in the case of fluorescence observation. Compared to, it cuts the light amount to an appropriate amount.

In addition, according to the imaging optical system of the first embodiment, the bottom surfaces 11c ₁ and 11c ₂ are configured to have the transparent columnar body (square column) 11 formed in a quadrangle, so that the two types of observation wavelengths are switched. Thus, an observation image can be taken.

Furthermore, in the imaging optical system of the first embodiment, the transparent column (quadrangular column) 11 constituting the incident surface switching optical member 1 has incident surfaces 11a ₁ and 11a ₂ intersecting the incident optical axis O of the imaging optical system. It is formed by varying the thickness of the glass material from each incident surface to the exit surface so that the air-converted length in the optical axis direction is different each time it is switched. That is, in the imaging optical system of the first embodiment, the thickness α1 of the glass material from the first incident surface 11a ₁ to the first exit surface 11b ₁ is such that the second entrance surface 11a ₂ to the second exit surface 11b. It is longer than the thickness α2 of the glass material up to ₂ .
In the imaging optical system of the first embodiment, an observation image with normal white light is captured when switched to the first incident surface 11a ₁ , and a fluorescence observation image is captured when switched to the second incident surface 11a _2. In the configuration described above, when the air conversion length is the same, the image formation position of the fluorescence observation image is shorter than that of the white observation image, so that the observation image of any observation wavelength is blurred on the imaging surface.
However, in the imaging optical system of the first embodiment, the thickness α1 of the glass material from the first incident surface 11a ₁ to the first exit surface 11b ₁ is such that the second entrance surface 11a ₂ leads to the second exit surface 11b. _Since it is made longer than the thickness α2 of the glass material up to ₂ , the imaging position is corrected and observation images of different observation wavelengths emitted from the incident surface switching optical member 1 are formed at the same imaging position. Can do.

In the imaging optical system of the first embodiment, the transmission wavelength characteristics of the incident surfaces 11a ₁ and 11a ₂ of the incident surface switching optical member 1 are limited to the combinations shown in FIGS. 3 (a) and 3 (b). Is not to be done. For example, the second incident surface 11a ₂ may be coated with a film having narrow band transmission characteristics (transmitting only wavelengths of 390 nm to 450 nm and 530 nm to 555 nm) as shown in FIG. In this case, when switching to the second incident surface 11a ₂ , observation images with narrow band wavelengths of B (blue) and G (green) can be taken. In this case, since the light intensity is not weak like fluorescence, the diameter of the diaphragm S2 may be formed to be the same as the diameter α1 of the diaphragm S1.
In the imaging optical system of the first embodiment, the shaft members A1 and A2 are provided on the axis orthogonal to the incident optical axis O of the imaging optical system. However, the shaft members A1 and A2 are arranged on the incident optical axis O. However, it may be provided on an axis that does not intersect the incident optical axis O as long as the axis is perpendicular to the axis.

Second Embodiment FIG. 4 is an explanatory view showing a schematic configuration of an imaging optical system according to a second embodiment of the present invention in a cross section along the optical axis. In addition, the same code | symbol is attached | subjected to the member with the same basic structure as 1st embodiment, and detailed description is abbreviate | omitted.
In the imaging optical system of the second embodiment, in addition to the configuration of the imaging optical system of the first embodiment, the incident surface switching optical member 1 has an incident surface 11a ₁ or 11a ₂ that intersects the incident optical axis O of the imaging optical system. Is tiltable at a desired angle with respect to the incident optical axis O.
Specifically, the second incident surface 11a ₂ is steplessly inclined from an incident angle of 0 ° (ie, an angle with respect to the optical axis O is 90 °) to an incident angle of 45 ° (ie, an angle with respect to the optical axis O is 45 °). It is configured to be able to.

In general, a filter has oblique incidence characteristics in which the transmittance characteristic shifts to the short wavelength side as the incident angle is changed to be larger. For example, when the second incident surface 11a ₂ is inclined by 45 °, the excitation cut wavelength band is shifted to the short wavelength side by about 35 nm as shown by a two-dot chain line in FIG. In this state, when the second incident surface 11a ₂ intersects the incident optical axis, blue light can be transmitted.
In the imaging optical system according to the second embodiment, since the inclination angle of the incident surface can be adjusted steplessly, the cut wavelength region can be continuously changed.
For this reason, according to the imaging optical system of the second embodiment, the observation wavelength can be adjusted and optimized in a desired observation mode. Moreover, the wavelength band which can respond | correspond to an excitation and fluorescence wavelength with one incident surface can be expanded.
In addition, since the aperture stops S1 and S2 are provided on the incident surfaces 11a ₁ and 11a ₂ , the brightness using the effect of vignetting (ie, reduction in peripheral light amount) by tilting the incident surfaces. The height adjustment can be performed simultaneously with the adjustment and optimization of the observation wavelength in the desired observation mode.
Other configurations and operational effects are substantially the same as those of the imaging optical system of the first embodiment.
In the imaging optical system of the second embodiment, the shaft members A1 and A2 are provided on the axis orthogonal to the incident optical axis O of the imaging optical system. However, the shaft members A1 and A2 are arranged on the incident optical axis O. However, it may be provided on an axis that does not intersect the incident optical axis O as long as the axis is perpendicular to the axis.

Third Embodiment FIG. 5 is an explanatory diagram showing a schematic configuration of an imaging optical system according to the third embodiment of the present invention in a cross section along the optical axis, and shows a state in which the mode is switched to the NBI (Narrow Band imaging) mode. It is a figure shown, respectively. In addition, the same code | symbol is attached | subjected to the member with the same basic structure as 1st embodiment, and detailed description is abbreviate | omitted.
In the imaging optical system of the third embodiment, the transparent column body 11 of the incident surface switching optical member 1 is configured to have a hexagonal column whose bottom surfaces 11c ₁ and 11c ₂ are formed in a hexagonal shape. The transparent column 11 includes a first incident surface 11a ₁ , a second incident surface 11a ₂ , a third incident surface 11a ₃ , a first exit surface 11b _1, and a second hexagonal column as side surfaces. The emission surface 11b ₂ and the third emission surface 11b ₃ are provided.
The first incident surface 11a ₁ , the second incident surface 11a ₂ , and the third incident surface 11a ₃ are provided in directions that intersect each other.
The incident surface switching optical member 1 is rotated about the shaft members A1 and A2, so that the incident surfaces intersecting the optical axis O of the imaging optical system are the first incident surface 11a ₁ and the second incident surface. The incident surface 11a ₂ or the third incident surface 11a ₃ is switched.

As shown in FIG. 3A, the first incident surface 11a ₁ transmits a wavelength in the visible light band of 390 nm to 710 nm and has a transmission wavelength characteristic that cuts a near infrared wavelength longer than 720 nm. The infrared cut filter surface is coated with an outer wavelength cut film. The first entrance surface 11a ₁ is provided with a first brightness stop S1.
As shown by the solid line in FIG. 3B, the second incident surface 11a ₂ is coated with an excitation wavelength cut film that cuts a wavelength shorter than 480 nm and transmits a wavelength longer than 485 nm. The excitation cut filter surface is configured. The second entrance surface 11a ₂ is provided with a second brightness stop S2.
As shown in FIG. 3C, the third incident surface 11a ₃ is a narrow band transmission filter coated with a film having a narrow band transmission characteristic (transmitting only wavelengths of 390 nm to 450 nm and 530 nm to 555 nm). It is configured as a surface. The third entrance surface 11a ₃ is provided with a third brightness stop S3.
The first brightness stop S1, the second brightness stop S2, and the third brightness stop S3 have a diameter φ1 of the first brightness stop S1 and a diameter φ3 of the third brightness stop S3. The diameter of each aperture stop S2 is smaller than the diameter φ2 of the aperture stop S2, and the diameter is fixed.
Further, the thickness of the glass material from the first incident surface 11a ₁ to the first exit surface 11b ₁ and the thickness of the glass material from the third entrance surface 11a ₃ to the third exit surface 11b ₃ are thicker. ing.
Other configurations are substantially the same as those of the imaging optical system of FIG.

In the imaging optical system of the third embodiment configured as described above, when taking an observation image in the WLI (white light observation) mode, a rotation driving member (not shown) is driven, and the incident surface together with the shaft members A1 and A2 The switching optical member 1 is rotated so that the first incident surface 11a ₁ comes to a position orthogonal to the optical axis O.
Light from an observation target (not shown) passes through the first group G1 and enters the incident surface switching optical member 1. The light having a diameter of φ1 that has passed through the first brightness stop S1 is incident on the first incident surface 11a ₁ . Of the light incident on the first incident surface 11a ₁ , visible light having a wavelength band of 390 nm to 710 nm is transmitted through the first incident surface 11a _1, and near infrared light having a wavelength band longer than 720 nm is Cut by _one incident surface 11a ₁ . The visible light that has passed through the first incident surface 11a ₁ exits the first exit surface 11b ₁ , enters the second group G2, passes through the cover glass CG, and forms an image on the imaging surface of the image sensor IM. .

Further, when an observation image is taken in the AFI (fluorescence observation) mode, a rotation driving member (not shown) is driven, and the incident surface switching optical member 1 is rotated together with the shaft members A1 and A2, as shown in FIG. The second incident surface 11a ₂ is positioned at a position orthogonal to the optical axis O.
Light including an excitation wavelength and a fluorescence wavelength from an observation target (not shown) passes through the first group G1 and enters the incident surface switching optical member 1. The light having a diameter of φ2 that has passed through the second brightness stop S2 enters the second incident surface 11a ₂ . Of the light incident on the second incident surface 11a ₂ , the light in the wavelength band including the excitation light shorter than 480 nm is cut by the second incident surface 11a ₂ , and the fluorescence in the wavelength band longer than 485 nm is transmitting the second incidence plane 11a _2. The fluorescence that has passed through the second incident surface 11a ₂ exits the second exit surface 11b ₂ , enters the second group G2, passes through the cover glass CG, and forms an image on the imaging surface of the image sensor IM.

Further, when an observation image is taken in the NBI (narrow band observation) mode, a rotation driving member (not shown) is driven, and the incident surface switching optical member 1 is rotated together with the shaft members A1 and A2, thereby providing a third incident. The surface 11a ₃ is positioned at a position orthogonal to the optical axis O.
Light from an observation target (not shown) passes through the first group G1 and enters the incident surface switching optical member 1. The light having a diameter of φ1 that has passed through the third brightness stop S3 is incident on the third incident surface 11a ₃ . Of the light incident on the third incident surface 11a ₃ , blue light of 390 nm to 450 nm, green light of 530 nm to 555 nm is transmitted through the third incident surface 11a _3, and light of other wavelengths is the third light. The incident surface 11a ₃ is cut. The B (blue) and G (green) light that has passed through the third incident surface 11a ₃ exits the third exit surface 11b ₃ , enters the second group G2, and passes through the cover glass CG to take an image. An image is formed on the imaging surface of the element IM.

Thus, according to the imaging optical system of the third embodiment, the incident surface switching optical member 1 has the transparent column body 11 whose bottom surface is formed in a hexagonal shape, so that the observation is switched to three types of observation wavelengths. An image can be taken.
Other functions and effects are substantially the same as those of the imaging optical system of FIG.
In the imaging optical system of the third embodiment, the shaft members A1 and A2 are provided on the axis orthogonal to the incident optical axis O of the imaging optical system. However, the shaft members A1 and A2 are arranged on the incident optical axis O. However, it may be provided on an axis that does not intersect the incident optical axis O as long as the axis is perpendicular to the axis.

Fourth Embodiment FIG. 6 is an explanatory view showing an optical configuration of an image pickup optical system according to the fourth embodiment of the present invention in a cross section along the optical axis, and is switched to an NBI (Narrow Band Imaging) mode. FIG. FIG. 7 is a perspective view showing a configuration of a frame member that constitutes a part of the incident surface switching optical member in the imaging optical system of FIG. In addition, the same code | symbol is attached | subjected to the member with the same basic structure as 1st embodiment, and detailed description is abbreviate | omitted.

In the imaging optical system according to the fourth embodiment, the incident surface switching optical member 1 has a rectangular parallelepiped frame member 13 whose bottom portions 13c ₁ and 13c ₂ are formed in quadrangular outlines, and frame members 13 at different frame positions. It has two parallel flat plates 12a and 12b provided.
The frame member 13 includes a first filter mounting frame 13a ₁ , a second filter mounting frame 13a ₂ , a first output side frame 13b _1, and a second output side frame 13b ₂ on the side of the rectangular parallelepiped shape. have.
The first filter mounting frame 13a ₁ and the second filter mounting frame 13a ₂ are provided so as to cross each other.

The entire bottom portions 13c ₁ and 13c ₂ are formed in a plate shape. At the center of the bottom portions 13c ₁ and 13c ₂ , shaft members A1 and A2 are fixed on an axis orthogonal to the incident optical axis O of the imaging optical system. The shaft members A1 and A2 are rotatably supported by a shaft support portion (not shown) and are rotated via a rotation drive member (not shown).
The entrance surface switching the optical member 1, by being rotated around the shaft member A1, A2, frame intersects the optical axis O of the imaging optical system, the mounting frame 13a ₁ or the second first filter so that the switching to the filter mounting frame 13a _2.

As shown in FIG. 3 (a), the first parallel plate 12a transmits a wavelength in the visible light band of 390 nm to 710 nm and cuts a near infrared wavelength longer than 720 nm on the incident surface 12a ₁ . It is configured as an infrared cut filter coated with an infrared wavelength cut film having transmission wavelength characteristics. The first parallel flat plate 12a is attached to the first filter attachment frame 13a ₁ . A first brightness stop S1 is provided on the incident surface 12a1 of the _first parallel plate 12a.

As shown by the solid line in FIG. 3B, the second parallel plate 12b has a transmission wavelength characteristic that cuts a wavelength shorter than 480 nm and transmits a wavelength longer than 485 nm on the incident surface 12b ₁ . It is composed of an excitation cut filter coated with an excitation wavelength cut film. The second parallel plate 12b is attached to the second filter mounting frame 13a _2. In addition, the incident surface 12b ₁ of the second parallel flat plate 12b, the second aperture stop S2 is provided.
The first brightness stop S1 and the second brightness stop S2 are fixed in diameter with the first brightness stop S1 diameter φ1 being smaller than the diameter φ2 of the second brightness stop. .
Further, the thickness of the glass material of the first parallel plate 12a is larger than the thickness of the glass material of the second parallel plate 12b.
Other configurations are substantially the same as those of the imaging optical system of FIG.

In the imaging optical system of the fourth embodiment configured as described above, when taking an observation image in the WLI (white light observation) mode, a rotation driving member (not shown) is driven, and the incident surface together with the shaft members A1 and A2 The switching optical member 1 is rotated so that the incident surface 12a ₁ of the infrared cut filter 12a comes to a position intersecting the optical axis O.
Light from an observation target (not shown) passes through the first group G1 and enters the incident surface switching optical member 1. The light having a diameter of φ1 that has passed through the first brightness stop S1 is incident on the incident surface 12a ₁ of the infrared cut filter 12a. Of the light incident on the incident surface 12a ₁ , visible light having a wavelength band of 390 nm to 710 nm passes through the incident surface 12a _1, and near infrared light having a wavelength band longer than 720 nm is cut by the incident surface 12a _1. The The visible light that has passed through the incident surface 12a ₁ exits from the exit surface 12a ₂ , enters the second group G2, passes through the cover glass CG, and forms an image on the imaging surface of the image sensor IM.

On the other hand, when an observation image is taken in the AFI (fluorescence observation) mode, a rotation driving member (not shown) is driven, and the incident surface switching optical member 1 is rotated together with the shaft members A1 and A2, as shown in FIG. In addition, the incident surface 12b ₁ of the excitation cut filter 12b is positioned at a position orthogonal to the optical axis O.
Light including an excitation wavelength and a fluorescence wavelength from an observation target (not shown) passes through the first group G1 and enters the incident surface switching optical member 1. The light having a diameter of φ2 that has passed through the second brightness stop S2 enters the incident surface 12b ₁ of the excitation cut filter 12b. Of the light incident on the incident surface 12b _1, shorter than 480 nm, light of a wavelength band including the excitation light is cut by the incident surface 12b _1, the fluorescence of the wavelength band longer than 485 nm, transmitted through the entrance surface 12b ₁ To do. The fluorescence that has passed through the incident surface 12b ₁ exits the output surface 12b ₂ , enters the second group G2, passes through the cover glass CG, and forms an image on the imaging surface of the image sensor IM.

Thus, according to the imaging optical system of the fourth embodiment, the incident surface switching optical member 1 is placed on an axis orthogonal to the incident optical axis O of the imaging optical system, as in the imaging optical system of the first embodiment. It can be rotated around the arranged shaft members A1, A2.
For this reason, according to the imaging optical system of the fourth embodiment, the optical characteristics of the two incident surfaces 12a ₁ and 12b _{1 in} the incident surface switching optical member 1 are made different from each other, thereby making the direction perpendicular to the imaging optical path. Without providing a space for retracting the filter, it is possible to switch to two different observation modes in one optical system and take an observation image.
However, in the imaging optical system of the fourth embodiment, the incident surfaces 12a ₁ and 12b ₁ of the incident surface switching optical member 1 have different transmission wavelength characteristics. Therefore, according to the imaging optical system of the fourth embodiment, the observation is switched to the white light observation mode or the fluorescence observation mode by switching the incident surfaces 12a ₁ and 12b ₁ intersecting the incident optical axis O of the imaging optical system. An image can be taken.

In addition, according to the imaging optical system of the fourth embodiment, the incident surface switching optical member 1 includes the aperture stops S1 and S2 having different diameters on the incident surfaces 12a ₁ and 12b ₁ , respectively. The amount of light can be adjusted at the same time as switching, and the effort of adjusting the amount of light by adjusting the diameter of the aperture stop for each switching of the observation wavelength can be saved. In the imaging optical system of the fourth embodiment, since the fluorescence is weak in light intensity and the observation image tends to be dark, when the observation image is captured in the fluorescence observation mode, the diameter of the aperture stop S2 is increased as much as possible. Therefore, the fluorescence is taken in as much as possible. On the other hand, normal white light has high light intensity and the observation image tends to be too bright. Therefore, when the observation image is captured in the observation mode using normal white light, the diameter of the aperture stop S1 is set in the case of fluorescence observation. Compared to, it cuts the light amount to an appropriate amount.

Further, according to the imaging optical system of the fourth embodiment, the bottom portions 13c ₁ and 13c ₂ are configured to have the prismatic frame member 13 whose outline is formed in a quadrilateral shape, so that the two types of observation wavelengths are switched. Thus, an observation image can be taken.

Further, in the imaging optical system of the fourth embodiment, the prismatic frame member 13 constituting the incident surface switching optical member 1 is switched every time the incident surfaces 13a ₁ and 13a ₂ intersecting the incident optical axis O of the imaging optical system are switched. In addition, the thickness of the glass material from each incident surface to the exit surface is made different so that the air conversion length in the optical axis direction is different. That is, in the imaging optical system of the fourth embodiment, the thickness of the glass material from the incident surface 12a ₁ to the exit surface 12a ₂ of the infrared cut filter 12a is from the entrance surface 12b ₁ to the exit surface 12b ₂ of the excitation cut filter. It is longer than the thickness of the glass material.
In the imaging optical system of the fourth embodiment, in the configuration in which an observation image with normal white light is switched to the infrared cut filter 12a and a fluorescence observation image is captured when the excitation cut filter 12b is switched, When the air-converted length is the same, the image formation position of the fluorescence observation image is shorter than that of the white observation image, so that the observation image of any observation wavelength is blurred on the imaging surface.
However, in the imaging optical system of the fourth embodiment, the thickness of the glass material from the incident surface 12a ₁ to the exit surface 12a ₂ of the infrared cut filter 12a is from the entrance surface 12b ₁ to the exit surface 12b ₂ of the excitation cut filter. Since it is made longer than the thickness of the glass material, it is possible to correct the imaging position and form observation images with different observation wavelengths emitted from the incident surface switching optical member 1 at the same imaging position.

In the imaging optical system of the fourth embodiment, the parallel plates 12a and 12b provided on the frame member 13 of the incident surface switching optical member 1 have transmission wavelength characteristics of the incident surfaces 12a ₁ and 12b ₁ as shown in FIG. It is not limited to the combination of filters shown in FIG. For example, the parallel plate 12b attached to the second filter attachment frame 13a ₂ has a coating having narrow band transmission characteristics (transmitting only wavelengths of 390 nm to 450 nm and 530 nm to 555 nm) as shown in FIG. A narrow band transmission filter coated on the surface may be used. In that case, when switching to the narrow band transmission filter, observation images of narrow band wavelengths of B (blue) and G (green) can be taken. In this case, since the light intensity is not weak like fluorescence, the diameter of the diaphragm S2 may be the same as the diameter α1 of the diaphragm S1.
In the imaging optical system of the fourth embodiment, the shaft members A1 and A2 are provided on the axis orthogonal to the incident optical axis O of the imaging optical system. However, the shaft members A1 and A2 are arranged on the incident optical axis O. However, it may be provided on an axis that does not intersect the incident optical axis O as long as the axis is perpendicular to the axis.

While the embodiments of the imaging optical system of the present invention have been described above, the imaging optical system of the present invention is not limited to the configurations of the above embodiments.
For example, each incident surface of the incident surface switching optical member 1 in each of the above embodiments may be formed in a curved surface shape. In this way, a part of the power of other optical members constituting the imaging optical system can be shared by the respective incident surfaces of the incident surface switching optical member 1, and the aberration of the other optical members can be reduced by reducing the curvature. Can be easily corrected, and the optical path length of the entire imaging optical system can be shortened.
In addition, you may form each entrance plane of the entrance plane switching optical member 1 in each embodiment in a plane. If it forms in a plane, the process of the entrance plane switching optical member 1 will become easy. Further, it is easy to assemble the incident surface switching optical member 1 into the imaging optical system at the time of manufacture.

  In addition, the imaging optical system of each of the above embodiments has a configuration that can be switched between a normal white light observation mode, a fluorescence observation mode, and a narrow-band observation mode as an observation mode using different observation wavelengths. However, the imaging optical system of the present invention is not limited to application in an observation mode at these observation wavelengths.

For example, the incident surface switching optical member 1 may be configured to switch between any of the above observation modes and an IRI (Infra Red Imaging) mode.
In that case, for example, a characteristic of transmitting a predetermined infrared wavelength (for example, 790 nm to 820 nm, 905 nm to 970 nm) to the second incident surface 11a ₂ of the incident surface switching optical member 1 in the imaging optical system shown in FIG. You may make it coat the infrared transmission film which has.

Furthermore, in the imaging optical system of the present invention, the incident surface switching optical member is not limited to the configuration for switching the observation mode at different observation wavelengths as described above, and is further in an observation mode such as polarization imaging or molecular imaging. You may comprise as a surface which changed the characteristic of each entrance plane so that it may switch.
That is, each incident plane may be configured as a polarization plane with different polarization characteristics or an interference plane with different transmission wavelengths.
Alternatively, the transmittance may be varied on each incident surface without changing the transmission wavelength band.
Furthermore, the image formation position may be made different by changing the surface power at each incident surface.

  The imaging optical system of the present invention is useful in fields such as medical, medical, and biology in which an observation image is captured by switching to a plurality of observation modes having different optical characteristics within one optical system.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows schematic structure of the imaging optical system concerning 1st embodiment of this invention in the cross section along an optical axis, (a) is the state switched to WLI (white light imaging) mode, (b) These are figures which each show the state switched to AFI (auto-fluorescence imaging: fluorescence observation) mode. FIG. 2 is an explanatory view of the incident surface switching optical member of the imaging optical system of FIG. 1 as viewed from the object side, where (a) is a diagram illustrating a state when the first incident surface is switched in a direction orthogonal to the incident optical axis; ) Is a diagram showing a state when the second incident surface is switched in a direction orthogonal to the incident optical axis. FIG. 3 is a graph showing the transmission wavelength characteristics of the incident surface of the incident surface switching optical member of the imaging optical system in FIG. 1, wherein (a) is a graph showing the transmission wavelength characteristics when the first incident surface is constituted by an infrared cut filter surface; , (B) is a graph showing the transmission wavelength characteristics when the second incident surface is configured by an excitation cut filter surface, (c) shows the transmission wavelength characteristics of the incident surface of the incident surface switching optical member according to one modification. It is a graph which shows the transmission wavelength characteristic when a 2nd incident surface is comprised with a narrow-band transmission filter surface in a graph. FIG. 4 is an explanatory diagram showing a schematic configuration of the imaging optical system according to the second embodiment of the present invention in a section along the optical axis. FIG. 5 is an explanatory diagram showing a schematic configuration of the imaging optical system according to the third embodiment of the present invention in a section along the optical axis, and shows a state in which the mode is switched to an NBI (Narrow Band imaging) mode. is there. FIG. 6 is an explanatory view showing the optical configuration of the imaging optical system according to the fourth embodiment of the present invention in a section along the optical axis, and shows the state switched to the NBI (Narrow Band imaging) observation mode, respectively. It is. It is a perspective view which shows the structure of the frame member which comprises a part of entrance plane switching optical member in the imaging optical system of FIG.

Explanation of symbols

1 incident plane switching optical member 11 transparent columnar body 11c _1, 11c ₂ bottom 11a ₁ first incident surface 11a ₂ second incidence plane 11a ₃ third incidence surface 11b ₁ first output surface 11b ₂ second exit Surface 11b ₃ Third exit surface 12a First parallel plate 12a ₁ entrance surface 12b Second parallel plate 12b ₁ entrance surface 13 Frame member 13a ₁ First filter attachment frame 13a ₂ Second filter attachment frame 13b ₁ One exit side frame 13b ₂ Second exit side frame 13c ₁ , 13c ₂ bottom A1, A2 Shaft member CG Cover glass FS Field stop G1 First group G2 Second group IM Imaging element O Incident optical axis S1 of imaging optical system 1st brightness stop S2 2nd brightness stop S3 3rd brightness stop

Claims (15)

In an imaging optical system that images an observation target,
There are at least two incident surfaces that transmit light and are arranged in directions that intersect each other, and each of the incident surfaces can intersect the incident optical axis of the imaging optical system, and the incident light of the imaging optical system It can be rotated about an axis perpendicular to the axis, and is rotated about an axis perpendicular to the incident optical axis of the imaging optical system, thereby intersecting the incident optical axis of the imaging optical system. An imaging optical system comprising an incident surface switching optical member configured to switch an incident surface.   The imaging optical system according to claim 1, wherein the at least one incident surface has optical characteristics different from those of the other incident surfaces.   The imaging optical system according to claim 1, wherein the incident surfaces have different optical characteristics.   The imaging optical system according to claim 2, wherein the at least one incident surface has transmission wavelength characteristics different from those of the other incident surfaces.   The imaging optical system according to claim 3, wherein the incident surfaces have different transmission wavelength characteristics.   The imaging optical system according to claim 1, wherein the incident surface switching optical member includes an aperture stop on each incident surface.   The imaging optical system according to claim 6, wherein the at least one brightness stop has a diameter different from that of other brightness stops.   The imaging optical system according to claim 6, wherein the respective aperture stops have different diameters.   The imaging according to any one of claims 1 to 8, wherein the incident surface switching optical member has a transparent column body whose bottom surface is formed in a quadrilateral, hexagonal or octagonal shape. Optical system.   The transparent column body varies the thickness of the glass material from each incident surface to the exit surface so that the air conversion length in the optical axis direction changes each time the incident surface intersecting the incident optical axis of the imaging optical system is switched. The imaging optical system according to claim 9, wherein the imaging optical system is formed.   The entrance surface switching optical member has a prismatic frame member whose bottom contour is formed in a quadrilateral, hexagonal or octagonal shape, and at least two parallel frames provided on different frames on the sides of the frame member. The imaging optical system according to claim 1, comprising a flat plate.   The at least two parallel plates are formed with different thicknesses so that the air-converted length in the optical axis direction changes each time the incident surface intersecting the incident optical axis of the imaging optical system is switched. The imaging optical system according to claim 11.   The imaging optical system according to claim 1, wherein each of the incident surfaces is formed in a planar shape.   The imaging optical system according to claim 1, wherein each of the incident surfaces is formed in a curved surface shape.   15. The incident surface switching optical member is configured such that an incident surface intersecting with an incident optical axis of the imaging optical system can be inclined at a desired angle with respect to the incident optical axis. The imaging optical system according to any one of the above.

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