Patent Publication Number: US-2016235299-A1

Title: Ophthalmic surgical microscope and ophthalmic surgical attachment

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-027489, filed 16 Feb. 2015; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to an ophthalmic surgical microscope and an ophthalmic surgical attachment. 
     BACKGROUND 
     In the ophthalmic field, various types of surgeries are performed. Among them are cataract surgery and vitreoretinal surgery, for example. An ophthalmic surgical microscope is used in such surgery. The ophthalmic surgical microscope is used for visual observation of an eye through an observation system illuminated by an illumination system or capturing of images. 
     There are such ophthalmic surgical microscopes that are provided with an optical coherence tomography (OCT) device (see, for example, Japanese Unexamined Patent Application Publication Nos. 2008-264488, 2008-264490, 2008-268852, 2009-230141, and 2008-264489). The OCT device is used to capture cross sectional images and three-dimensional images, measure the size of tissue (the thickness of a layer, etc.), acquire functional information (blood flow information, etc.), and the like. 
     The OCT device is required to be capable of obtaining an OCT signal of sufficient intensity as well as having a high resolution, a wide scan range, and a compact structure. To satisfy these requirements, an important factor is the position for coupling the OCT optical path with the optical path of the ophthalmic surgical microscope. 
     In the surgical microscope disclosed in Japanese Unexamined Patent Application Publication Nos. 2008-264488, 2008-264490, 2008-268852, and 2009-230141, the OCT optical path is connected to the observation optical path. In the surgical microscope disclosed in Japanese Unexamined Patent Application Publication No. 2008-264489, the OCT optical path is connected to the illumination optical path, and these optical paths are connected to the observation optical path. 
     As disclosed in Japanese Unexamined Patent Application Publication Nos. 2008-264488, 2008-264490, 2008-268852, and 2009-230141, if the OCT optical path is connected to the observation optical path, sufficient resolution cannot be achieved due to a restriction in the diameters of the lenses arranged in the observation optical path. The OCT optical path may be connected to the observation optical path at a position between the objective lens and the eye to avoid this problem. In this case, however, the device cannot be compact and may interfere with the manipulation or operation of the surgeon. Besides, in the configuration disclosed in Japanese Unexamined Patent Application Publication No. 2008-264489, the OCT optical path is connected to the illumination optical path at a position between lenses that constitute a lens unit for making illumination light into a parallel light flux. This results in a complicated optical design. Thus, it becomes difficult to downsize the surgical microscope and modularize the OCT device attachable to the surgical microscope. 
     SUMMARY 
     Embodiments are intended to solve the above problems, and the object is to provide an ophthalmic surgical microscope and an ophthalmic surgical attachment capable of wide-range and high-resolution OCT examination with a compact structure. 
     According to one embodiment, an ophthalmic surgical microscope includes an objective lens, illumination system, observation system, OCT system, and optical-path connecting member. The illumination system includes a diaphragm irradiated with light from an illumination light source and a lens unit including one or more lenses that make the light having passed through the diaphragm into a parallel light flux, and irradiates the light having passed through the lens unit to an eye through the objective lens. The observation system is configured for observing the eye being irradiated by the illumination system through the objective lens. The OCT system is configured for examining the eye by OCT through the objective lens. The optical-path connecting member is located between the diaphragm and the lens unit or between the lens unit and the objective lens to connect the optical path of the OCT system to that of the illumination system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an example of the configuration of an optical system of an ophthalmic surgical microscope according to a first embodiment. 
         FIG. 2  is a schematic diagram illustrating an example of the configuration of the optical system of the ophthalmic surgical microscope of the first embodiment. 
         FIG. 3  is a schematic diagram illustrating an example of the configuration of an optical system of an ophthalmic surgical microscope according to a second embodiment. 
         FIG. 4A  is a diagram illustrating an example of the operation of the ophthalmic surgical microscope of the second embodiment. 
         FIG. 4B  is a diagram illustrating an example of the operation of the ophthalmic surgical microscope of the second embodiment. 
         FIG. 5A  is a diagram illustrating an example of the operation of the ophthalmic surgical microscope of the second embodiment. 
         FIG. 5B  is a diagram illustrating an example of the operation of the ophthalmic surgical microscope of the second embodiment. 
         FIG. 6  is a schematic diagram illustrating an example of the configuration of an optical system of an ophthalmic surgical microscope according to a third embodiment. 
         FIG. 7  is a schematic diagram illustrating an example of the configuration of an optical system of an ophthalmic surgical microscope according to a fourth embodiment. 
         FIG. 8A  is a diagram illustrating an example of the operation of the ophthalmic surgical microscope of the fourth embodiment. 
         FIG. 8B  is a diagram illustrating an example of the operation of the ophthalmic surgical microscope of the fourth embodiment. 
         FIG. 9  is a schematic diagram illustrating an example of the configuration of an optical system of an ophthalmic surgical microscope according to a fifth embodiment. 
         FIG. 10  is a schematic diagram illustrating an example of the configuration of an optical system of an ophthalmic surgical microscope according to a sixth embodiment. 
         FIG. 11  is a schematic diagram illustrating an example of the configuration of an optical system of an ophthalmic surgical microscope according to a seventh embodiment. 
         FIG. 12A  is a diagram illustrating an example of the operation of the ophthalmic surgical microscope of the seventh embodiment. 
         FIG. 12B  is a diagram illustrating an example of the operation of the ophthalmic surgical microscope of the seventh embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, a description is given of examples of embodiments of an ophthalmic surgical microscope and an ophthalmic surgical attachment. The ophthalmic surgical microscope of the following embodiments is used in ophthalmic surgery. The ophthalmic surgical microscope is a device that illuminates an eye (a patient&#39;s eye) by an illumination system so that the light returning therefrom enters the observation system to capture an observation image of the eye. The ophthalmic surgical attachment is configured to be detachably attached to the ophthalmic surgical microscope. 
     In the following embodiments, the ophthalmic surgical microscope becomes capable of OCT examination when equipped with an ophthalmic surgical attachment that includes at least part of the OCT optical system. It is assumed herein that the OCT examination includes the acquisition of cross sectional images and/or three-dimensional images, the measurement of the size of tissue (the thickness of a layer, etc.), the acquisition of functional information (blood flow information, etc.), and the like. The target site to be examined by OCT may be any site of the eye. Examples of the site include the cornea, vitreous body, crystalline lens, and ciliary body in the anterior segment of the eye, and the retina, choroid, and vitreous body in the posterior segment. The target site may also be a periphery of the eye such as the eyelid and eye socket. By a known method, it is possible to form a cross sectional image or a three-dimensional image of the eye based on measurement light returning through the ophthalmic surgical attachment. 
     Hereinafter, the measurement light for OCT examination and the light returning from the eye may be collectively referred to as OCT light. In addition, images acquired by OCT may be collectively referred to as OCT images. Further, measurement for forming an OCT image may be referred to as OCT measurement. Incidentally, the contents of documents cited above may be incorporated by reference herein. 
     In the following embodiments, a configuration using a Fourier domain OCT is described. In particular, the ophthalmic surgical microscope (and ophthalmic surgical attachment) of the following embodiments is capable of the OCT examination of the eye using a known swept-source OCT technology. 
     The embodiments may be applied also to ophthalmic surgical microscopes other than those using a swept-source OCT, such as, for example, those using a spectral domain OCT. Although the following embodiments describe a device combining an OCT device that includes an optical system of OCT and an ophthalmic surgical microscope, the OCT device of the embodiments may be combined with an ophthalmologic observation device other than the ophthalmic surgical microscope, such as, for example, a scanning laser ophthalmoscope (SLO), a slit lamp, and a fundus camera. 
     First Embodiment 
       FIGS. 1 and 2  illustrate the optical system of an ophthalmic surgical microscope  1  according to the first embodiment.  FIG. 1  illustrates the configuration of the optical system of an observation system viewed from the operator side.  FIG. 2  illustrates a side view of the optical system of an illumination system and an interference optical system of  FIG. 1  viewed from the operator. Like reference numerals designate like parts in  FIGS. 1 and 2 . Incidentally, in addition to the configuration illustrated in  FIGS. 1 and 2 , the ophthalmic surgical microscope may be provided with an optical system (assistant microscope) for the operator&#39;s assistant to observe an eye E. 
     In the present embodiment, directions such as upper and lower, left and right, front and back, and the like are defined as viewed from the operator side unless otherwise noted. Regarding the upper and lower directions, the direction from the objective lens toward the observation object (eye E) is referred to as “lower”, and the opposite direction is referred to as “upper”. In general, patient undergoes surgery in the supine position, and thus the upper and lower directions correspond to the vertical direction. 
     The optical system of the ophthalmic surgical microscope  1  includes an illumination system  10 , an OCT system  20 , an optical-path connecting member  30 , a deflector  40 , an observation system  50 , and an objective lens  70 . The ophthalmic surgical microscope  1  further includes an ophthalmic surgical attachment  100  that is configured to be detachably attached to the ophthalmic surgical microscope  1 . At least part of the OCT system  20  (e.g., collimating lens  22 , optical scanner  23 , OCT lens  24 ) and the optical-path connecting member  30  are provided in the ophthalmic surgical attachment  100 . In the following, the illumination system  10 , the OCT system  20 , the optical-path connecting member  30 , and the deflector  40  are described mainly with reference to  FIG. 2 . The observation system  50  is described mainly with reference to  FIG. 1 . 
     The ophthalmic surgical microscope  1  may include a front lens  200  that is configured to be removably inserted into a position on the optical axis of the objective lens  70  as a main objective lens. The front lens  200  can be placed in a position between the front focal position of the objective lens  70  and the eye E. The front lens  200  focuses the light from the illumination system  10  to illuminate the inside of the eye E (the posterior eye segment such as the retina, vitreous body, etc.). The front lens  200  includes a plurality of lenses having different refractive powers (e.g.,  40 D,  80 D,  120 D, etc.), which are selectively used.  FIG. 1  illustrates the front lens  200  retracted from the position on the optical axis of the objective lens  70 .  FIG. 2  illustrates the front lens  200  inserted into the position on the optical axis of the objective lens  70 . 
     (Illumination System) 
     The illumination system  10  includes an illumination light source  11 , a condenser lens  12 , and a diaphragm  13  (illumination field diaphragm, visual field diaphragm), and a lens unit  14 . The illumination light source  11  emits illumination light including visible light. The condenser lens  12  condenses the illumination light emitted from the illumination light source  11 . The diaphragm  13  limits the illumination field of the illumination light condensed by the condenser lens  12 . The diaphragm  13  is located in a position optically conjugate with the front focal position of the objective lens  70 . The lens unit  14  includes one or more lenses that make the light having passed through the diaphragm  13  into a parallel light flux. While  FIG. 2  illustrates an example in which the lens unit  14  includes one lens, the lens unit  14  may include two or more lenses. The illumination light having passed through the lens unit  14  is irradiated onto the eye E through the objective lens  70  of the observation system  50 . 
     (OCT System) 
     The OCT system  20  includes an optical system for examining the eye E by using OCT through the objective lens  70 . The OCT system may have the same configuration as the conventional Fourier domain OCT device (e.g., swept-source OCT). The OCT system  20  includes an interference optical system  21 , a collimating lens  22 , a focus adjustment mechanism  22 A, an optical scanner  23 , and an OCT lens  24 . 
     The light from the OCT light source is split into measurement light and reference light. The interference optical system  21  emits the measurement light, and causes the measurement light returning from the eye to interfere with the reference light to generate interference light. The interference optical system  21  includes, for example, a splitter part, and an interference part. The splitter part splits the light from the OCT light source (e.g., wavelength-swept light source (wavelength tunable light source)) into measurement light and reference light. The OCT light source emits light at near-infrared wavelengths invisible to the human eye. The measurement light is emitted toward the eye E. The reference light is emitted toward a predetermined reference optical path. The interference part causes the measurement light returning from the eye E to interfere with the reference light having passed through the reference optical path, thereby generating interference light. The interference light generated by the interference optical system  21  is detected by a detector (not illustrated). The detector obtains detection signals and sends them to an arithmetic and control unit (not illustrated). Like conventional swept-source OCT devices, the arithmetic and control unit applies arithmetic processing such as Fourier transform to the detection signals. Note that the interference optical system  21  may include an OCT light source. 
     For example, one end of an optical fiber is connected to the interference optical system  21 . The other end of the optical fiber is located in a position facing the collimating lens  22 . The measurement light emitted from the interference optical system  21  is guided by the optical fiber to be incident on the collimating lens  22 . The return light of the measurement light that has passed through the collimating lens  22  is guided by the optical fiber to be incident on the splitter part of the interference optical system  21 . 
     The collimating lens  22  collimates the measurement light emitted from the interference optical system  21  into a parallel light flux. The focus adjustment mechanism  22 A moves the collimating lens  22  along the optical axis of the OCT system  20 . The focus adjustment mechanism  22 A includes, for example, a holding member, a slide mechanism, and an actuator. The holding member holds the collimating lens  22 . The slide mechanism is configured to move the holding member in the direction along the optical axis of the OCT system  20 . The actuator generates a driving force. The focus adjustment mechanism  22 A further includes a member configured to transmit the driving force to the slide mechanism. The focus adjustment mechanism  22 A can move the collimating lens  22  manually or automatically. In the case of manual operation, the focus adjustment mechanism  22 A controls the actuator based on operation on an operation unit (not illustrated) performed by a user (e.g., operator) to thereby move the collimating lens  22 . In the case of automatic operation, a control unit (not illustrated) controls the actuator so that the measurement light returning from the eye E, the interference light, and/or the detection signal has an intensity above a predetermined value, and thus the focus adjustment mechanism  22 A can move the collimating lens  22 . 
     The optical scanner  23  two-dimensionally deflects the measurement light, which has been collimated into a parallel light flux by the collimating lens  22 . Thereby, the optical scanner  23  scans the eye E with the measurement light collimated into a parallel light flux. The optical scanner  23  includes, for example, a first galvanometer mirror and a second galvanometer mirror. The first galvanometer mirror deflects the measurement light in a first direction in the scan plane set for the eye E. The second galvanometer mirror deflects the measurement light in a second direction perpendicular to the first direction. The optical scanner  23  further includes a mechanism for driving them independently. In this case, the optical scanner  23  can scan the eye E with the measurement light in arbitrary directions on a plane defined by the first and second directions. 
     The OCT lens  24  is arranged between the optical scanner  23  and the optical-path connecting member  30 , and functions as a variable power lens. The measurement light deflected by the optical scanner  23  passes through the OCT lens  24 , and is guided to the optical-path connecting member  30 . 
     The optical-path connecting member  30  is arranged between the diaphragm  13  and the lens unit  14  on the optical path of the illumination system  10 , and connects the optical path of the OCT system  20  to the optical path of the illumination system  10 . Specifically, the optical-path connecting member  30  is arranged to face a lens of the one or more lenses constituting the lens unit  14 , which is optically closest to the illumination light source  11 . In the present embodiment, the optical axis of the OCT system  20  and that of the illumination system  10  are arranged coaxially. For example, the OCT system  20  and the illumination system  10  are arranged such that the positions of their optical axes match each other in the reflective surface of the optical-path connecting member  30 . As an example of the optical-path connecting member  30  may be cited a dichroic mirror. The collimating lens  22 , the focus adjustment mechanism  22 A, the optical scanner  23 , the OCT lens  24 , and the optical-path connecting member  30  are provided in the ophthalmic surgical attachment  100 . Further, at least part of the interference optical system  21  may be provided in the ophthalmic surgical attachment  100 . Furthermore, the OCT light source may be provided in the ophthalmic surgical attachment  100 . 
     The deflector  40  is arranged between the optical-path connecting member  30  and the objective lens  70 , and deflects the light in the optical paths of the illumination system  10  and the OCT system  20  toward the objective lens  70 . The deflector  40  may be included in the observation system  50 . Examples of the deflector  40  include a beam splitter, a half mirror, a dichroic mirror, and an epi-illumination mirror formed of one or more reflecting members.  FIG. 1  illustrates the deflector  40  as a beam splitter.  FIG. 2  illustrates the deflector  40  as an epi-illumination mirror formed of two reflecting members  40   a  and  40   b.    
     As a beam splitter, the deflector  40  is arranged in the optical path of the observation system  50 . In this case, the beam splitter (the deflector  40 ) coaxially connects the optical path of the observation system  50  and the optical path of the OCT system  20 . 
     As an epi-illumination mirror, the deflector  40  is desirably arranged outside the optical path of the observation system  50 . In  FIG. 2 , the light having passed through the lens unit  14  is reflected by the reflecting members  40   a  and  40   b . The reflecting member  40   a  is arranged to reflect the light having passed through the lens unit  14  and not reflected by the reflecting member  40   b.    
     (Observation System) 
     The observation system  50  includes an optical system for observing the eye E, through the objective lens  70 , being illuminated by the illumination system  10 . As illustrated in  FIG. 1 , the observation system  50  includes a pair of left and right observation systems  50 L and  50 R, and an imaging optical system  60 . Hereinafter, the observation system  50 L on the left side is referred to as “left observation system” (left observation optical axis  50 La), while the observation system  50 R on the right side is referred to as “right observation system” (right observation optical axis  50 Ra). The left and right observation systems  50 L and  50 R are arranged to sandwich the optical axis of the objective lens  70 . 
     The left and right observation systems  50 L and  50 R each include a variable power lens system  51 , an imaging lens  52 , an erecting prism  53 , a pupil distance adjustment prism  54 , a visual field diaphragm  55 , and an eyepiece  56 . The right observation system  50 R is provided with a beam splitter  57  between the variable power lens system  51  and the imaging lens  52 . 
     The variable power lens system  51  includes a plurality of zoom lenses  51   a ,  51   b , and  51   c . Each of the zoom lenses  51   a  to  51   c  is movable by a zooming mechanism (not illustrated) in a direction along the left observation optical axis  50 La or the right observation optical axis  50 Ra. Thereby, the magnification for observing or photographing the eye E is changed. 
     The beam splitter  57  separates part of observation light guided along the right observation optical axis  50 Ra from the eye E and leads it to the imaging optical system  60 . The imaging optical system  60  includes an imaging lens  61 , a reflecting mirror  62 , and an imaging unit  63 . 
     The imaging unit  63  includes an imaging device  63   a . The imaging device  63   a  may be formed of, for example, a charge coupled device (CCD) image sensor, a complementary metal oxide semiconductor (CMOS) image sensor, or the like. For the imaging device  63   a , those having a two-dimensional light receiving surface (area sensor) are used. 
     In the use of the ophthalmic surgical microscope  1 , for example, the light receiving surface of the imaging device  63   a  is located in a position optically conjugate with the surface of the cornea of the eye E, or a position optically conjugate with a position separated from the corneal apex in the depth direction by a half of the radius of curvature of the cornea. 
     The erecting prism  53  turns an image right-side up. The pupil distance adjustment prism  54  is an optical element for adjusting the distance between left observation light and right observation light according to the operator&#39;s eye width (distance between the left and right eyes). The visual field diaphragm  55  shields a peripheral region in the cross section of the observation light to limit the field of view of the operator. 
     In the above configuration, regardless of whether the ophthalmic surgical attachment  100  is being attached, the ophthalmic surgical microscope  1  irradiates the eye E with illumination light to enable the observation of the eye E. Specifically, the illumination light output from the illumination light source  11  is condensed by the condenser lens  12 . The illumination light then passes through the diaphragm  13  and the optical-path connecting member  30 , and is collimated into a parallel light flux by the lens unit  14 . The illumination light collimated into a parallel light flux is deflected by the deflector  40 . After passing through the objective lens  70 , the illumination light is irradiated to the eye E. When the front lens  200  is inserted to a position on the optical axis of the objective lens  70 , the illumination light deflected by the deflector  40  passes through the objective lens  70  and the front lens  200 , and then is irradiated to the eye E. 
     The illumination light (part of the illumination light) irradiated to the eye E is reflected by the cornea or within the eye. The illumination light reflected by the eye E (sometimes referred to as “observation light”) travels through the objective lens  70  (in some cases, the front lens  200 ) and is incident on the observation system  50 . With this configuration, a magnified image of the eye E can be observed through the eyepiece  56 . An image captured by the imaging unit  63  may be displayed on a display (not illustrated). 
     When the ophthalmic surgical attachment  100  is attached to the ophthalmic surgical microscope  1 , the optical-path connecting member  30  is located between the diaphragm  13  and the lens unit  14 . The measurement light obtained by dividing the light from the OCT light source travels through the collimating lens  22 , the optical scanner  23 , and the OCT lens  24 , and is reflected by the optical-path connecting member  30 . The measurement light reflected by the optical-path connecting member  30  travels through the lens unit  14 , and after being deflected by the deflector  40 , passes through the objective lens  70  (in some cases, also the front lens  200 ), thereby reaching the eye E. The measurement light reflected by the eye E returns therefrom through the same path as described above to the interference optical system  21 . The interference optical system  21  causes the measurement light returning from the eye to interfere with the reference light obtained by splitting the light from the OCT light source to generate interference light. The interference light generated by the interference optical system  21  is detected by a detector (not illustrated). The detector obtains detection signals and sends them to the arithmetic and control unit (not illustrated). Like conventional swept-source OCT devices, the arithmetic and control unit applies arithmetic processing such as Fourier transform to the detection signals. Based on the result of the arithmetic processing, the arithmetic and control unit forms a cross sectional image or a three-dimensional image of a predetermined site of the eye E, measures the size of tissue (the thickness of a layer, etc.), generates functional information (blood flow information, etc.), and the like. 
     In the present embodiment, the aperture (diameter) of the optical element, through which the measurement light of the OCT system  20  and the return light of the measurement light (OCT light) pass, can be increased. Accordingly, it is possible to enlarge the scan range by the measurement light and the numerical aperture affecting the resolution of the measurement light of the OCT system  20 . Besides, the optical path of the OCT system  20  is connected to the optical path of the illumination system  10  at a position between the diaphragm  13  and the lens unit  14 . Thereby, the illumination system  10  and the OCT system  20  can share the lens unit  14 . This results in a reduced number of optical elements, thus realizing a compact device. 
     In general, a relatively large physical space can be secured between the diaphragm  13  and the lens unit  14 . Therefore, by modularizing the collimating lens  22 , the optical scanner  23 , the OCT lens  24 , and the optical-path connecting member  30 , it is possible to achieve an ophthalmic surgical attachment ( 100 ) that can be easily attached to and detached from the ophthalmic surgical microscope  1  without influence on the optical system such as the positional deviation and the axial displacement of the diaphragm  13  due to vibration, or the like. Incidentally, there may be provided an adjustment mechanism for correcting the positional deviation and the axial displacement of the diaphragm  13 , or the like. 
     In the present embodiment, an example is described in which at least part of the OCT system  20  and the optical-path connecting member  30  are modularized as the ophthalmic surgical attachment  100 ; however, they are not necessarily be modularized. 
     Operations and Effects 
     Described below are the operations and effects of the ophthalmic surgical microscope and the ophthalmic surgical attachment according to the first embodiment. 
     According to the first embodiment, an ophthalmic surgical microscope (e.g., the ophthalmic surgical microscope  1 ) includes an objective lens (e.g., the objective lens  70 ), an illumination system (e.g., the illumination system  10 ), an observation system (e.g., the observation system  50 ), an OCT system (e.g., the OCT system  20 ), and an optical-path connecting member (e.g., the optical-path connecting member  30 ). The illumination system includes a diaphragm (e.g., the diaphragm  13 ) and a lens unit (e.g., the lens unit  14 ), and irradiates light having passed through the lens unit to an eye (e.g., the eye E) through the objective lens. The diaphragm is irradiated with light from a light source. The lens unit includes one or more lenses configured to collimate the light having passed through the diaphragm into a parallel light flux. The observation system is used to observe the eye being illuminated by the illumination system through the objective lens. The OCT system is used to examine the eye through the objective lens by using OCT. The optical-path connecting member is located between the diaphragm and the lens unit, and connects the optical path of the OCT system to the optical path of the illumination system. 
     With this configuration, in the ophthalmic surgical microscope used for the surgery of the eye, the aperture (diameter) of the optical element, through which the measurement light of the OCT system passes, can be increased. Accordingly, it is possible to widely design the scan range with the measurement light and the numerical aperture affecting the resolution of the measurement light of the OCT system. Besides, the optical path of the OCT system is connected to the optical path of the illumination system at a position between the diaphragm and the lens unit. Thereby, the illumination system and the OCT system can share the lens unit. This results in a reduced number of optical elements of the illumination system, thus realizing a compact device. Further, since the optical path of the OCT system is connected to the optical path of the illumination system, wide-range OCT examination can be performed with a high resolution. 
     The ophthalmic surgical microscope may further include a deflector (e.g., the deflector  40 ), which is located between the optical-path connecting member and the objective lens, and deflects light in the optical path of the illumination system and light in the optical path of the OCT system toward the objective lens. 
     With this configuration, the eye can be illuminated from the objective lens side, thus achieving a compact device. 
     Further, the deflector may include a beam splitter arranged on the optical path of the observation system. 
     With this configuration, the deflector for deflecting the illumination light and the light of the OCT system can be placed in the observation optical path, thus achieving a compact device. 
     The beam splitter may coaxially connect the optical path of the observation system and the optical path of the OCT system with each other. 
     With this configuration, OCT examination can be performed on the eye in a condition close to a state where the eye is observed by the observation system. 
     In addition, the OCT system may include an interference optical system (e.g., the interference optical system  21 ), a collimating lens (e.g., the collimating lens  22 ), an optical scanner (e.g., the optical scanner  23 ), and an OCT lens (e.g., the OCT lens  24 ). The light from the OCT light source is split into measurement light and reference light. The interference optical system emits the measurement light, and causes the measurement light returning from the eye to interfere with the reference light to generate interference light. The collimating lens collimates the measurement light emitted from the interference optical system into a parallel light flux. The optical scanner two-dimensionally deflects the measurement light, which has been collimated into a parallel light flux by the collimating lens. The OCT lens is located between the optical scanner and the optical-path connecting member. 
     With this configuration, OCT examination can be performed with the ophthalmic surgical microscope used for the surgery of the eye by employing a known method. 
     The ophthalmic surgical microscope may further include a focus adjustment mechanism (e.g., the focus adjustment mechanism  22 A) configured to move the collimating lens along the optical axis of the OCT system. 
     With this configuration, in the ophthalmic surgical microscope used for the surgery of the eye, high-resolution OCT examination can be performed in the optimum conditions. 
     The ophthalmic surgical microscope may further include an ophthalmic surgical attachment (e.g., the ophthalmic surgical attachment  100 ) configured to be detachably attached to the ophthalmic surgical microscope. The collimating lens, the optical scanner, the OCT lens, and the optical-path connecting member may be provided in the ophthalmic surgical attachment. 
     In this configuration, since the collimating lens, the optical scanner, the OCT lens, and the optical-path connecting member are modularized to be detachably attached to the ophthalmic surgical microscope, the ophthalmic surgical microscope can be switched to a device capable of OCT examination. 
     According to the first embodiment, an ophthalmic surgical attachment is configured to be detachably attached to an ophthalmic surgical microscope for examining the eye through the objective lens by OCT. The ophthalmic surgical attachment includes a collimating lens, an optical scanner, an OCT lens, and an optical-path connecting member. When the ophthalmic surgical attachment is attached to the ophthalmic surgical microscope, the optical-path connecting member may be located between the diaphragm and the lens unit. The ophthalmic surgical microscope includes an objective lens and an illumination system. The illumination system includes a diaphragm irradiated with light from a light source, and a lens unit having one or more lenses configured to collimate the light having passed through the diaphragm into a parallel light flux, and is configured to irradiate the light having passed through the lens unit to the eye through the objective lens. The ophthalmic surgical microscope includes an observation system used to observe, through the objective lens, the eye being illuminated by the illumination system. The interference optical system splits the light from the OCT light source into measurement light and reference light, emits the measurement light, and causes the measurement light returning from the eye to interfere with the reference light to generate interference light. The collimating lens collimates the measurement light emitted from the interference optical system into a parallel light flux. The optical scanner two-dimensionally deflects the measurement light, which has been collimated into a parallel light flux by the collimating lens. The measurement light deflected by the optical scanner passes through the OCT lens. The optical-path connecting member is used to connect the optical path of the measurement light having passed through the OCT lens to the optical path of the illumination system. 
     With this configuration, the collimating lens, the optical scanner, the OCT lens, and the optical-path connecting member can be modularized as an ophthalmic surgical attachment that is easily attached to and detached from the ophthalmic surgical microscope. In general, a relatively large physical space can be secured between the diaphragm and the lens unit as well as between the lens unit and the objective lens. Thus, it is possible to switch the ophthalmic surgical microscope to a device capable of OCT examination without influence on the optical system such as the positional deviation and the axial displacement of the diaphragm, or the like. 
     Second Embodiment 
     In the first embodiment, the illumination optical path and the OCT optical path are connected coaxially. Therefore, the deflector  40  and the iris (pupil) of the eye E may cause vignetting in the measurement light from the OCT system  20  and the like. In particular, if the deflector  40  is formed of an epi-illumination mirror, since a reflecting member that constitutes the epi-illumination mirror has a complicated shape, vignetting may occur in the measurement light from the OCT system  20 . When vignetting occurs in the measurement light, the range of OCT scan is limited, and the OCT system  20  cannot exert its full performance. 
     For this reason, in the second embodiment, the optical axis of the illumination system and the optical axis of the OCT system are arranged to be non-coaxial. The optical axis of the illumination system and the optical axis of the OCT system may be fixed to be non-coaxial, or they may be moved relatively to be adjusted as in the present embodiment. 
     An ophthalmic surgical microscope of the second embodiment has basically the same configuration as that of the first embodiment. In the following, the second embodiment is described with a focus on differences from the first embodiment. 
       FIG. 3  illustrates the configuration of an optical system of an ophthalmic surgical microscope  1   a  of the second embodiment. In  FIG. 3 , like reference numerals designate like parts as in  FIG. 2 , and the redundant explanation may be omitted as appropriate. 
     The ophthalmic surgical microscope  1   a  of the second embodiment is different in configuration from the ophthalmic surgical microscope  1  of the first embodiment in the presence of an optical-axis adjustment mechanism  21 A. An OCT system  20   a  includes the interference optical system  21 , the optical-axis adjustment mechanism  21 A, the collimating lens  22 , the focus adjustment mechanism  22 A, the optical scanner  23 , and the OCT lens  24 . An ophthalmic surgical attachment  100   a  includes the collimating lens  22 , the focus adjustment mechanism  22 A, the optical scanner  23 , the OCT lens  24 , and the optical-path connecting member  30 . The ophthalmic surgical attachment  100   a  may further include the interference optical system  21  and the optical-axis adjustment mechanism  21 A. The ophthalmic surgical attachment  100   a  may further include an OCT light source. 
     The optical-axis adjustment mechanism  21 A moves the optical axis of the illumination system  10  and that of the OCT system  20  relative to each other. For example, the optical-axis adjustment mechanism  21 A changes the direction of measurement light emitted from the interference optical system  21  to relatively move the optical axis of the illumination system  10  and that of the OCT system  20 . The direction of measurement light emitted from the interference optical system  21  may be changed by tilting the end of an optical fiber for emitting the measurement light from the interference optical system  21  or tilting the case that holds an optical element constituting the interference optical system  21 . When the end of the optical fiber is tilted, the optical-axis adjustment mechanism  21 A includes a holding member, an emission angle deflector, an actuator that generates a driving force, and a member that transmits the driving force to the emission angle deflector. The holding member is configured to movably hold one end of an optical fiber having the other end connected to the interference optical system  21 . The emission angle deflector is configured to move the holding member to change the emission angle of measurement light in reference to a predetermined emission direction. The optical-axis adjustment mechanism  21 A is capable of moving the optical axis of the OCT system  20  toward the center of the pupil of the eye E by the above mechanism. 
     The optical-axis adjustment mechanism  21 A moves the optical axis of the illumination system  10  (e.g., the center of a illumination light flux) and the optical axis of the OCT system  20  (e.g., the center of a measurement light flux) relative to each other such that they are located in different positions in the reflective surface of the deflector  40  (in the example of  FIG. 3 , the reflecting members  40   a  and  40   b ). As a result, the optical-path connecting member  30  connects the optical path of the OCT system  20  to the optical path of the illumination system  10  non-coaxially. 
       FIGS. 4A and 4B  are diagrams for explaining the operation to observe the fundus of the eye E. To observe the fundus of the eye E, the front lens  200  is inserted in a position between the objective lens  70  and the eye E as illustrated in  FIG. 3 .  FIG. 4A  schematically illustrates the pupil of each optical system incident on the pupil of the eye E when vignetting occurs in measurement light due to the deflector  40  (epi-illumination mirror).  FIG. 4B  schematically illustrates the pupil of each optical system incident on the pupil of the eye E when the optical-axis adjustment mechanism  21 A changes the direction of measurement light from the interference optical system  21 . Like reference numerals designate like parts in  FIGS. 4A and 4B , and the redundant explanation may be omitted as appropriate. 
     When the fundus of the eye E is observed, the illumination pupil (image) of the illumination system  10  and the observation pupil of the observation system  50  are placed in the pupil P of the eye E such that the iris R causes no vignetting. For example, an illumination pupil L 1  of illumination light reflected by the reflecting member  40   b  in illumination light emitted from the illumination system  10 , an illumination pupil L 2  of illumination light reflected by the reflecting member  40   a  in illumination light emitted from the illumination system  10 , an observation pupil B 1  of the left observation system  50 L, and an observation pupil B 2  of the right observation system  50 R are placed in the pupil P of the eye E as illustrated in  FIG. 4A . Here, if the deflector  40  is formed of an epi-illumination mirror having a complicated shape, and an OCT pupil of the OCT system  20  is placed in the pupil P, for example, an OCT pupil C 1  of the OCT system  20  may be arranged to overlap the illumination pupil L 1 , and an OCT pupil C 2  of the OCT system  20  may be arranged to overlap the illumination pupil L 2 . In this case, vignetting occurs in the measurement light of the OCT system  20  due to the deflector  40  (epi-illumination mirror). 
     In the present embodiment, when the optical-axis adjustment mechanism  21 A changes the direction of measurement light emitted from the interference optical system  21 , as illustrated in  FIG. 4B , an OCT pupil C 3  of the OCT system  20  can be arranged to overlap the illumination pupil L 1 . Thereby, it is possible to suppress the occurrence of vignetting of measurement light due to the deflector  40 . Thus, the OCT system  20  can exert its full performance without limiting the range of OCT scan. 
       FIGS. 5A and 5B  are diagrams for explaining the operation to observe the fundus of the eye E having a small pupil.  FIG. 5A  schematically illustrates the pupil of each optical system incident on the pupil of the eye E when the iris of the eye E as a small pupil causes vignetting in measurement light.  FIG. 5B  schematically illustrates the pupil of each optical system incident on the pupil of the eye E when the optical-axis adjustment mechanism  21 A changes the direction of measurement light from the interference optical system  21 . In  FIGS. 5A and 5B , like reference numerals designate like parts as in  FIGS. 4A and 4B , and the redundant explanation may be omitted as appropriate. 
     When the eye E has a small pupil, the OCT pupil C 3  of the OCT system  20  is arranged as illustrated in  FIG. 5A , and the iris R may cause vignetting in measurement light. Here, if the optical-axis adjustment mechanism  21 A changes the direction of measurement light emitted from the interference optical system  21 , as illustrated in  FIG. 5B , an OCT pupil C 4  of the OCT system  20  can be arranged to overlap the illumination pupil L 1  in the pupil P. Thereby, it is possible to suppress the occurrence of vignetting of measurement light due to the iris R. Thus, the OCT system  20  can exert its full performance without limiting the range of OCT scan. This is particularly effective when the pupil of the eye E is small at the time of observing the fundus, and the position adjustment of the device is not sufficient. 
     In the present embodiment, while the optical-axis adjustment mechanism  21 A is described as adjusting the optical axis of the OCT system  20 , the direction of illumination light emitted from the illumination system  10  may be changed to move the optical axis of the illumination system  10  and the optical axis of the OCT system  20  relative to each other. 
     Operations and Effects 
     According to the second embodiment, an ophthalmic surgical microscope may include an optical-axis adjustment mechanism (e.g., the optical-axis adjustment mechanism  21 A) configured to move the optical axis of the illumination system and that of the OCT system relative to each other. 
     With this configuration, it is possible to suppress the occurrence of vignetting in the light of the OCT system due to the deflector or the iris of the eye. Thus, the OCT system can exert its full performance without limiting the range of OCT scan. 
     According to the embodiment, the light from the OCT light source is split into measurement light and reference light. The interference optical system emits the measurement light, and causes the measurement light returning from the eye to interfere with the reference light to generate interference light. The optical-axis adjustment mechanism may change the direction of the measurement light emitted from the interference optical system to relatively move the optical axis of the illumination system and that of the OCT system. 
     With this, the ophthalmic surgical microscope of the embodiment having a relatively simple structure can be provided with an OCT system that can exert its full performance. 
     Third Embodiment 
     In the first embodiment or the second embodiment, an example is described in which the optical-path connecting member  30  is arranged between the diaphragm  13  and the lens unit  14 ; however, the configuration of the ophthalmic surgical microscope of the embodiment is not limited to this. 
     In the third embodiment, the optical-path connecting member  30  is arranged between the lens unit  14  and the objective lens  70 . The optical axis of the illumination system and that of the OCT-system are positioned coaxially. 
     An ophthalmic surgical microscope of the third embodiment has basically the same configuration as that of the first embodiment. In the following, the third embodiment is described with a focus on differences from the first embodiment. 
       FIG. 6  illustrates the configuration of an optical system of an ophthalmic surgical microscope  1   b  of the third embodiment. In  FIG. 6 , like reference numerals designate like parts as in  FIG. 2 , and the redundant explanation may be omitted as appropriate. 
     The ophthalmic surgical microscope  1   b  of the third embodiment is mainly different in configuration from the ophthalmic surgical microscope  1  of the first embodiment in that the optical-path connecting member  30  is located between the lens unit  14  and the objective lens  70  (the deflector  40 ), and the presence of an OCT lens  24   b  formed of two or more lenses in place of the OCT lens  24 . 
     The optical-path connecting member  30  is located between the lens unit  14  and the objective lens  70  on the optical path of the illumination system  10  to connect the optical path of the OCT system  20  to the optical path of the illumination system  10 . Specifically, the optical-path connecting member  30  is arranged to face a lens of the one or more lenses constituting the lens unit  14 , which is optically closest to the objective lens  70 . Incidentally, in  FIG. 6 , the deflector  40  is arranged between the optical-path connecting member  30  and the objective lens  70 . 
     In the third embodiment, the measurement light of the OCT system  20  is irradiated to the eye E without passing through the lens unit  14 . Therefore, for example, by providing the OCT lens  24   b  as illustrated in  FIG. 6 , it is possible to achieve a design taking into account the transmission loss and the aberration of the measurement light. Thus, according to the present embodiment, OCT examination can be performed using measurement light from the OCT system  20  with improved accuracy as compared to the first embodiment in which the illumination system  10  and the OCT system  20  share the lens unit  14 . 
     Further, according to the embodiment, the optical-path connecting member  30  is located on the parallel optical path where the illumination light of the illumination system  10  is made into a parallel light flux. Therefore, it is possible to reduce the influence on the illumination system  10  associated with the attachment/detachment of an ophthalmic surgical attachment  100   b  to/from the ophthalmic surgical microscope  1   b  (e.g., the positional displacement of the optical element of the illumination system  10 , and the like). 
     Operations and Effects 
     According to the third embodiment, an ophthalmic surgical microscope includes an objective lens, and an illumination system. The an illumination includes a diaphragm irradiated with light from a light source, and a lens unit having one or more lenses configured to collimate the light having passed through the diaphragm into a parallel light flux, and is configured to irradiate, through the objective lens, the light having passed through the lens unit to the eye. The ophthalmic surgical microscope further includes an observation system, an OCT system, and an optical-path connecting member. The observation system is used to observe, through the objective lens, the eye being illuminated by the illumination system. The OCT system is used to examine the eye E through the objective lens by means of OCT. The optical-path connecting member is located between the lens unit and the objective lens on the optical path of the illumination system to connect the optical path of the OCT system to the optical path of the illumination system. 
     With this configuration, in the ophthalmic surgical microscope used for the surgery of the eye, the aperture (diameter) of the optical element, through which the measurement light of the OCT system  20  passes, can be increased. Accordingly, it is possible to increase the scan range by the measurement light and the numerical aperture affecting the resolution of the measurement light of the OCT system. Besides, the optical path of the OCT system is connected to the optical path of the illumination system at a position between the lens unit and the objective lens. Such a design takes into account only the OCT system, thereby improving the accuracy of OCT examination. In addition, optical elements including at least the objective lens and the like are used in common. This results in a reduced number of optical elements, thus realizing a compact device. Further, similarly to the first embodiment, wide-range OCT examination can be performed with a high resolution. 
     According to the third embodiment, an ophthalmic surgical attachment is configured to be detachably attached to an ophthalmic surgical microscope which includes an objective lens, an illumination system, and an observation system. The illumination system includes a diaphragm irradiated with light from a light source, and a lens unit having one or more lenses configured to collimate the light having passed through the diaphragm into a parallel light flux, and is configured to irradiate the light having passed through the lens unit to the eye through the objective lens. The observation system is used to observe, through the objective lens, the eye being illuminated by the illumination system. The ophthalmic surgical attachment is used for examining the eye through the objective lens by OCT. The ophthalmic surgical attachment further includes a collimating lens, an optical scanner, an OCT lens, and an optical-path connecting member. The light from the OCT light source is split into measurement light and reference light. The interference optical system emits the measurement light, and causes the measurement light returning from the eye to interfere with the reference light to generate interference light. The collimating lens collimates the measurement light emitted from the interference optical system into a parallel light flux. The optical scanner two-dimensionally deflects the measurement light, which has been collimated into a parallel light flux by the collimating lens. The measurement light deflected by the optical scanner passes through the OCT lens. The optical-path connecting member is used to connect the optical path of the measurement light having passed through the OCT lens to the optical path of the illumination system. When the ophthalmic surgical attachment is attached to the ophthalmic surgical microscope, the optical-path connecting member is located at a position between the lens unit and the objective lens. 
     In this configuration, since the collimating lens, the optical scanner, the OCT lens, and the optical-path connecting member are modularized, they can be easily attached to and detached from the ophthalmic surgical microscope as an attachment. In addition, a relatively large physical space can be secured between the lens unit and the objective lens. Thus, it is possible to switch the ophthalmic surgical microscope to a device capable of OCT examination without influence on the optical system such as the positional deviation and the axial displacement of the lens unit, or the like. 
     Fourth Embodiment 
     In the third embodiment, the illumination optical path and the OCT optical path are connected coaxially as in the first embodiment. Accordingly, vignetting may occur in the measurement light from the OCT system  20 . In such a case, the range of OCT scan is limited, and the OCT system  20  cannot exert its full performance. 
     For this reason, in the fourth embodiment, the optical axis of the illumination system and the optical axis of the OCT system are arranged to be non-coaxial as in the second embodiment. The optical axis of the illumination system and the optical axis of the OCT system may be fixed to be non-coaxial, or they may be moved relatively to be adjusted as in the present embodiment. 
     An ophthalmic surgical microscope of the fourth embodiment has basically the same configuration as that of the third embodiment. In the following, the second embodiment is described with a focus on differences from the third embodiment. 
       FIG. 7  illustrates the configuration of an optical system of an ophthalmic surgical microscope  1   c  of the fourth embodiment. In  FIG. 7 , like reference numerals designate like parts as in  FIG. 6 , and the redundant explanation may be omitted as appropriate. 
     The ophthalmic surgical microscope  1   c  of the fourth embodiment is different in configuration from the ophthalmic surgical microscope  1   b  of the third embodiment in the presence of the same optical-axis adjustment mechanism  21 A as in the second embodiment. An OCT system  20   c  includes the interference optical system  21 , the optical-axis adjustment mechanism  21 A, the collimating lens  22 , the focus adjustment mechanism  22 A, the optical scanner  23 , and the OCT lens  24   b . An ophthalmic surgical attachment  100   c  includes the collimating lens  22 , the focus adjustment mechanism  22 A, the optical scanner  23 , the OCT lens  24   b , and the optical-path connecting member  30 . The ophthalmic surgical attachment  100   c  may further include the interference optical system  21  and the optical-axis adjustment mechanism  21 A. The ophthalmic surgical attachment  100   c  may further include an OCT light source. 
     The optical-axis adjustment mechanism  21 A moves the optical axis of the illumination system  10  and that of the OCT system  20   c  relative to each other. For example, the optical-axis adjustment mechanism  21 A changes the direction of measurement light emitted from the interference optical system  21  to relatively move the optical axis of the illumination system  10  and that of the OCT system  20   c . The optical-axis adjustment mechanism  21 A is basically the same as that of the second embodiment, and the same description is not repeated. The optical-axis adjustment mechanism  21 A may change, for example, the direction of illumination light emitted from the illumination system  10  to move the optical axis of the illumination system  10  and that of the OCT system  20   c  relative to each other. 
       FIGS. 8A and 8B  are diagrams for explaining the operation to observe the fundus of the eye E.  FIG. 8A  schematically illustrates the pupil of each optical system incident on the pupil of the eye E when vignetting occurs in measurement light due to positional deviation.  FIG. 8B  schematically illustrates the pupil of each optical system incident on the pupil of the eye E when the optical-axis adjustment mechanism  21 A changes the direction of measurement light from the interference optical system  21 . Like reference numerals designate like parts in  FIGS. 8A and 8B , and the redundant explanation may be omitted as appropriate. 
     For example, when the position of the eye E has deviated with respect to the optical axis of the objective lens  70 , the OCT pupil C 4  of the OCT system  20   c  is arranged as illustrated in  FIG. 8A , and vignetting may occur in the measurement light. Here, if the optical-axis adjustment mechanism  21 A changes the direction of measurement light emitted from the interference optical system  21 , as illustrated in  FIG. 8B , OCT an pupil C 5  of the OCT system  20   c  can be arranged to overlap the illumination pupil L 1  in the pupil P. Thereby, it is possible to suppress the occurrence of vignetting of measurement light due to the positional deviation. Thus, the OCT system  20   c  can exert its full performance without limiting the range of OCT scan. 
     As described above, according to the fourth embodiment, in addition to the effects of the third embodiment, the effects by adjusting the optical axis can be achieved as in the second embodiment. 
     Fifth Embodiment 
     In the fourth embodiment, an example is described in which the direction of measurement light emitted from the interference optical system is changed to shift the optical axis of the OCT system with respect to the optical axis of the illumination system; however, the configuration of the ophthalmic surgical microscope of the embodiment is not limited to this. 
     In the fifth embodiment, the optical scanner  23  and the OCT lens  24   b  are moved integrally in parallel to shift the optical axis of the OCT system with respect to the optical axis of the illumination system. 
     An ophthalmic surgical microscope of the fifth embodiment has basically the same configuration as that of the third embodiment. In the following, the fifth embodiment is described with a focus on differences from the third embodiment. 
       FIG. 9  illustrates the configuration of an optical system of an ophthalmic surgical microscope  1   d  of the fifth embodiment. In  FIG. 9 , like reference numerals designate like parts as in  FIG. 6 , and the redundant explanation may be omitted as appropriate. 
     The ophthalmic surgical microscope  1   d  of the fifth embodiment is different in configuration from the ophthalmic surgical microscope  1   b  of the third embodiment in that the optical scanner  23  and the OCT lens  24   b  are integrated as a scanner unit  25 , and in the presence of an optical-axis adjustment mechanism  25 A configured to move the scanner unit  25  in parallel. An OCT system  20   d  includes the interference optical system  21 , the collimating lens  22 , the focus adjustment mechanism  22 A, the scanner unit  25  that includes the optical scanner  23  and the OCT lens  24   b , and the optical-axis adjustment mechanism  25 A. An ophthalmic surgical attachment  100   d  includes the collimating lens  22 , the focus adjustment mechanism  22 A, the scanner unit  25  that includes the optical scanner  23  and the OCT lens  24   b , the optical-axis adjustment mechanism  25 A, and the optical-path connecting member  30 . The ophthalmic surgical attachment  100   d  may further include the interference optical system  21  and the optical-axis adjustment mechanism  21 A. The ophthalmic surgical attachment  100   d  may further include an OCT light source. 
     The optical-axis adjustment mechanism  25 A is configured to move the scanner unit  25  in parallel. For example, the optical-axis adjustment mechanism  25 A moves the scanner unit  25  in parallel along a third direction that is parallel to the optical axis of the illumination system  10  and a fourth direction that is perpendicular to the third direction. Thus, the optical axis of the illumination system  10  and that of the OCT system  20   d  can be moved relatively to be arranged in different positions in the reflective surface of the deflector  40 . In the fifth embodiment, the optical-path connecting member  30  is located on the parallel optical path where the illumination light is made into a parallel light flux. Therefore, the position of the scan plane in the eye E can be adjusted with a high precision, without being affected by the refraction of the lens unit  14 . Moreover, as compared to the second embodiment or the fourth embodiment, the optical axis can be shifted in a wide range. 
     Operations and Effects 
     According to the fifth embodiment, an ophthalmic surgical microscope includes an optical-axis adjustment mechanism (e.g., the optical-axis adjustment mechanism  25 A) configured to move the optical axis of the illumination system (e.g., the illumination system  10 ) and the optical axis of the OCT system (e.g., the OCT system  20   d ) relative to each other. The optical-path connecting member is arranged in a position between the lens unit and the objective lens. The optical-axis adjustment mechanism changes the positions of the optical scanner and the OCT lens to move the optical axis of the illumination system and that of the OCT system. 
     In this configuration, the optical-path connecting member is located on the parallel optical path where the illumination light is made into a parallel light flux. Therefore, the position of the scan plane in the eye can be adjusted with a high precision, without being affected by the refraction of the lens unit. Further, it is possible to suppress the occurrence of vignetting of light in the OCT system. Thus, the OCT system can sufficiently exert the performance without limiting the range of OCT scan. 
     Sixth Embodiment 
     The configuration, in which the optical axis of the OCT system can be shifted with respect to the optical axis of the illumination system, is not limited to that described in the fourth embodiment or the fifth embodiment. 
     In the sixth embodiment, there is provided a plane-parallel plate that can be arranged at a position between the optical scanner and the optical-path connecting member such that the incident surface is inclined with respect to the optical axis of the OCT system to, thereby, shift the optical axis of the OCT system with respect to the optical axis of the illumination system. 
     An ophthalmic surgical microscope of the sixth embodiment has basically the same configuration as that of the third embodiment. In the following, the sixth embodiment is described with a focus on differences from the third embodiment. 
       FIG. 10  illustrates the configuration of an optical system of an ophthalmic surgical microscope  1   e  of the sixth embodiment. In  FIG. 10 , like reference numerals designate like parts as in  FIG. 6 , and the redundant explanation may be omitted as appropriate. 
     The ophthalmic surgical microscope  1   e  of the sixth embodiment is different in configuration from the ophthalmic surgical microscope  1   b  of the third embodiment in the presence of a plane-parallel plate  26  and an optical-axis adjustment mechanism  26 A. The plane-parallel plate  26  is removably inserted to a position between the optical scanner  23  and the optical-path connecting member  30 . The optical-axis adjustment mechanism  26 A is configured to move the plane-parallel plate  26 . An OCT system  20   e  includes the interference optical system  21 , the collimating lens  22 , the focus adjustment mechanism  22 A, the optical scanner  23 , the OCT lens  24   b , the plane-parallel plate  26 , and the optical-axis adjustment mechanism  26 A. An ophthalmic surgical attachment  100   e  includes the collimating lens  22 , the focus adjustment mechanism  22 A, the optical scanner  23 , the OCT lens  24   b , the plane-parallel plate  26 , the optical-axis adjustment mechanism  26 A, and the optical-path connecting member  30 . The ophthalmic surgical attachment  100   e  may further include the interference optical system  21  and the optical-axis adjustment mechanism  21 A. The ophthalmic surgical attachment  100   e  may further include an OCT light source. 
     The plane-parallel plate  26  is, for example, an optical element that is arranged such that the incident surface and the exit surface are parallel to each other, and transmits measurement light or return light thereof in the OCT system  20   e . The plane-parallel plate  26  is configured to be removably inserted between the optical scanner  23  and the optical-path connecting member  30 . When the plane-parallel plate  26  is inserted at a position between the optical scanner  23  and the optical-path connecting member  30 , the incident surface is inclined with respect to the optical axis of the OCT system  20   e . In  FIG. 10 , the plane-parallel plate  26  is configured to be removably inserted between the OCT lens  24   b  and the optical-path connecting member  30 . 
     The optical-axis adjustment mechanism  26 A is configured to move the plane-parallel plate  26  to insert/remove it to/from a position on the optical axis of the OCT system  20   e  between the OCT lens  24   b  and the optical-path connecting member  30 . Thereby, the light having passed through the plane-parallel plate  26  is refracted, and the optical axis of the illumination system  10  and that of the OCT system  20   e  can be moved relatively to be arranged in different positions in the reflective surface of the deflector  40 . In the sixth embodiment, the optical-path connecting member  30  is located on the parallel optical path where the illumination light is made into a parallel light flux. Therefore, the position of the scan plane in the eye E can be adjusted in stages without being affected by the refraction of the lens unit  14 . 
     Incidentally, if the optical-axis adjustment mechanism  26 A is configured to be capable of changing the direction of the incident surface of the plane-parallel plate  26  located between the OCT lens  24   b  and the optical-path connecting member  30 , the position of the scan plane in the eye E can be adjusted more finely. In addition, the plane-parallel plate  26  may be fixed at a position between the OCT lens  24   b  and the optical-path connecting member  30  in advance. The optical-axis adjustment mechanism  26 A may be capable of changing the direction of the incident surface of the plane-parallel plate  26 . 
     Operations and Effects 
     As described above, according to the sixth embodiment, an ophthalmic surgical microscope includes a plane-parallel plate (e.g., the plane-parallel plate  26 ) and an optical-axis adjustment mechanism (e.g., the optical-axis adjustment mechanism  26 A). The plane-parallel plate is configured to be removably inserted to a position between the optical scanner and the optical-path connecting member and is arranged such that the incident surface is inclined with respect to the optical axis of the OCT system (e.g., the OCT system  20   e ). The optical-axis adjustment mechanism is configured to insert/remove the plane-parallel plate to/from the position between the optical scanner and the optical-path connecting member. The optical-path connecting member is located between the lens unit and the objective lens. The optical-axis adjustment mechanism inserts/removes the plane-parallel plate to/from between the optical scanner and the optical-path connecting member to move the optical axis of the illumination system and the optical axis of the OCT system relative to each other. 
     Besides, the ophthalmic surgical microscope of the embodiment may include a plane-parallel plate (e.g., the plane-parallel plate  26 ) and an optical-axis adjustment mechanism (e.g., the optical-axis adjustment mechanism  26 A). The plane-parallel plate is arranged between the optical scanner and the optical-path connecting member, and has an incident surface the direction of which can be changed with respect to the optical axis of the OCT system. The optical-axis adjustment mechanism is configured to change the direction of the incident surface. The optical-path connecting member is located between the lens unit and the objective lens. The optical-axis adjustment mechanism changes the direction of the incident surface to move the optical axis of the illumination system and that of the OCT system relative to each other. 
     In any of the configurations described above, the optical-path connecting member is located on the parallel optical path where the illumination light is made into a parallel light flux. Therefore, the position of the scan plane in the eye can be adjusted with a high precision, without being affected by the refraction of the lens unit. Further, it is possible to suppress the occurrence of vignetting of light in the OCT system. Thus, the OCT system can sufficiently exert the performance without limiting the range of OCT scan. 
     Seventh Embodiment 
     If provided with a beam splitter arranged on the observation optical axis in at least part of the deflector  40 , the ophthalmic surgical microscope having the optical-axis adjustment mechanism as described above becomes capable of switching between the coaxial state where the optical axis of the OCT system and the observation optical axis are coaxial and the non-coaxial state where they are non-coaxial. 
     An ophthalmic surgical microscope of the seventh embodiment has basically the same configuration as that of the sixth embodiment. In the following, the seventh embodiment is described with a focus on differences from the sixth embodiment. 
       FIG. 11  illustrates the configuration of an optical system of an ophthalmic surgical microscope if of the seventh embodiment. In  FIG. 11 , like reference numerals designate like parts as in  FIG. 10 , and the redundant explanation may be omitted as appropriate. 
     The ophthalmic surgical microscope if of the seventh embodiment is different in configuration from the ophthalmic surgical microscope  1   e  of the sixth embodiment in the presence of a deflector  40 A provided in place of the deflector  40 . The deflector  40 A includes a reflecting member  40   f  and a beam splitter  40   g . The beam splitter  40   g  is arranged on the observation optical axis of the observation system  50  (the left observation optical axis  50 La or the right observation optical axis  50 Ra), and connects the optical path of the illumination system  10  and that of the observation system  50  to each other. Note that the deflector  40 A may connect the optical path of the illumination system  10  and that of the observation system  50  by using another optical element such as a dichroic mirror, a half mirror, or the like instead of the beam splitter  40   g.    
     In this configuration, the optical-axis adjustment mechanism  26 A adjusts the optical axis of the OCT system  20   e  with respect to the optical axis of the illumination system  10 . Thereby, the optical axis of the OCT system  20   e  can be adjusted to be coaxial or non-coaxial with the observation optical axis. 
       FIGS. 12A and 12B  are diagrams for explaining the operation to observe the fundus of the eye E.  FIG. 12A  schematically illustrates the pupil of each optical system incident on the pupil of the eye E when the optical axis of the OCT system  20   e  is adjusted to be coaxial with the observation optical axis.  FIG. 12B  schematically illustrates the pupil of each optical system incident on the pupil of the eye E when the optical axis of the OCT system  20   e  is adjusted to be non-coaxial with the observation optical axis. Like reference numerals designate like parts in  FIGS. 12A and 12B , and the redundant explanation may be omitted as appropriate. 
     When the optical axis of the OCT system  20   e  is adjusted to be coaxial with the observation optical axis, as illustrated in  FIG. 12A , an OCT pupil C 6  of the OCT system  20   e  is arranged to overlap the observation pupil B 1  of the left observation system  50 L. At this time, it becomes possible to perform an examination by OCT under conditions similar to those in the observation by the observation system  50 . 
     On the other hand, when the optical axis of the OCT system  20   e  is adjusted to be non-coaxial with the observation optical axis, as illustrated in  FIG. 12B , an OCT pupil C 7  of the OCT system  20   e  is arranged between the observation pupil B 1  of the left observation system  50 L and the observation pupil B 2  of the right observation system  50 R. In this case, the occurrence of vignetting can be suppressed as described above. Thus, the OCT system  20   e  can sufficiently exert the performance without limiting the range of OCT scan. 
     MODIFICATIONS 
     The embodiments described above are mere examples for embodying or carrying out the present invention, and therefore susceptible to several modifications and variations (omission, substitution, addition, etc.), all coming within the scope of the invention. 
     The various features of the above embodiments may be combined in arbitrary ways. For example, in a system which can use two or more of the first to seventh embodiments, desired one of the two or more embodiments can be selectively used by switching the operation mode. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.