Abstract: An immersion type microscope objective lens OL includes, in order from a cover plate C side, a first lens group G1 having positive refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. The first lens group G1 includes at least one cemented lens. The second lens group G2 includes at least two achromatic lenses. The third lens group G3 includes, in order from the object side, an achromatic lens CL31 having a strong concave surface facing an image side, and an achromatic lens CL32 having a strong concave surface facing the object side.

Abstract: An objective lens includes multiple optical elements disposed between a first end and a second end, each optical element oriented along an optical axis. Each optical surface of the multiple optical elements provides an angle of incidence to a marginal ray that is above a minimum threshold angle. This threshold angle minimizes pupil ghosts that may enter an interferometer. The objective lens also optimizes wavefront delivery and pupil imaging onto an optical surface under test.

Abstract: An immersion microscope objective formed of thirteen or fewer lens elements includes, in order from the object side, first and second lens groups of positive refractive power, a third lens group, a fourth lens group having negative refractive power with its image-side surface being concave, and a fifth lens group having positive refractive power with its object-side surface being concave. The first lens group includes, in order from the object side, a lens component that consists of a lens element of positive refractive power (when computed as being in air) and a meniscus lens element having its concave surface on the object side. Various conditions are satisfied to ensure that images of fluorescence, obtained when the immersion microscope objective is used in a laser scanning microscope that employs multiphoton excitation to observe a specimen, are bright and of high resolution. Various laser scanning microscopes are also disclosed.

Abstract: A microscope apparatus efficiently supplies and collects a liquid for observation by local liquid immersion. The apparatus includes an objective of a liquid immersion system, a discharging member for discharging the liquid between a front edge of the objective and a substrate, and a sucking member for sucking the liquid. Inclined faces are provided respectively in two positions adjacent to the front edge in the periphery of the objective, and protruded portions are provided in positions adjacent to the inclined faces. An aperture portion bounded by the protruded portions and the substrate is formed at the side face. The discharging member includes a tubular member provided on the inclined face for discharging the liquid. The sucking member includes another tubular member for sucking the liquid while taking in air via the aperture portion.

Abstract: A tube unit for microscopes which has a tube lens, including two components with an intermediate, large air separation and an overall positive refractive power. The air separation is at least half the size of the focal length f of the tube lens. A roof edge mirror or another suitable deflection element is arranged between the two components of the tube lens. The roof edge mirror includes two mirrors which can be tilted with respect to one another, and which is able to be tilted around its roof edge. The tilting movement or the tilting angle of the tiltable mirror or deflection element corresponds to half the tilt or half the tilting angle of the tube or eyepiece viewing system.

Abstract: An objective lens OL includes, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having positive refractive power, a diffractive optical element GD forming a diffractive optical surface D thereon, and a third lens group G3 having negative refractive power. The first lens group G1 includes at least one cemented lens and the most object side surface thereof forms a concave surface facing the object. The second lens group G2 includes at least one cemented lens. The third lens group G3 includes at least one cemented negative lens. In the objective lens OL, a principal ray crosses an optical axis between the second lens group G2 and the third lens group G3, and in the diffractive optical element GD, the diffractive optical surface D is disposed in the vicinity of the position where the principal ray crosses the optical axis.

Abstract: The object is to provide an optical system with a wavelength selecting device. According to one aspect of the present invention, an optical system with a wavelength selecting device includes, in order from an object along an optical axis, an objective optical system composed of optical elements having refractive power and an aperture stop, a no-power optical group composed of optical elements having no refractive power, and an imaging device. The no-power optical group includes the wavelength selecting device for making short wavelength light be selectively substantially non-transparent. The wavelength selecting device preferably satisfies the predetermined conditional expressions.

Abstract: An endoscope objective lens for collecting combined bright field (white light) and fluorescence images includes a negative lens group, a stop, and a positive lens group. The lens has a combination of large entrance pupil diameter (?0.4 mm) for efficiently collecting weak fluorescence light, large ratio between the entrance pupil diameter and the maximum outside diameter (Dentrance/Dmax larger than 0.2), large field of view (FFOV?120°) and favorably corrected spherical, lateral chromatic and Petzval field curvature for both visible and near infrared wavelengths.

Abstract: A lens unit is equipped with a lens, through which light from an object enters, and a lens barrel for holding the lens. An optical extending member is employed when observing a focal image of the lens with a microscope. A receiving portion having a receiving surface, for receiving a front end facet of the optical path extending member within the lens barrel that faces toward the lens, is formed at a portion of the lens barrel. A mounting portion positioned further rearward from a rear end facet of the optical path extending member, having a guide insertion aperture that extends in a direction perpendicular to the receiving surface and a mounting surface that extends in a direction parallel to the receiving surface is formed at the periphery of the guide insertion aperture is formed at a portion of the lens barrel.

Abstract: Without setting an examination site, it is possible to easily position an end face of a narrow-diameter end portion at a suitable position with respect to an examination target, allowing an image of the examination site to be acquired quickly and easily. The invention provides an objective-lens guiding device comprising a support portion secured to an objective lens having a narrow-diameter end portion; and a cylindrical portion for accommodating the narrow-diameter end portion. The support portion supports the cylindrical portion such that a front end of the cylindrical portion is disposed at a location farther toward the front than an end face of the narrow-diameter end portion, and so as to be capable of moving in an optical axis direction.

Abstract: An immersion microscope objective includes a system of several optical lenses or lens groups between which air spaces are provided and an adjusting device for adapting the immersion microscope objective to different immersion mediums for correcting imaging errors when utilizing the immersion microscope objective in connection with a cover glass, which closes off a specimen holder, and/or for correcting longitudinal chromatic aberrations. The adjusting device is configured to change two air spaces and especially the air spaces (A1, A2) are linearly changeable.

Abstract: An immersion microscope objective lens of the present invention has: in order from an object, a first lens group G1 having positive refractive power and having a cemented lens of a plano convex lens having a plane facing the object and a meniscus lens having a concave surface facing the object, and a single meniscus lens having a convex surface facing the object; a second lens group having positive refractive power and having a plurality of cemented lenses; and a third lens group having negative refractive power and having a cemented meniscus lens having a concave surface facing an image, and a cemented meniscus lens having a concave surface facing the object. And the following conditional expressions 0.12<d0/f<0.25, 0.04<?Ct(p)??Ct(n)<0.09 and ?0.03<?hg(p)??hg(n)<0.00 are satisfied.

Abstract: A catadioptric objective includes a plurality of optical elements arranged along an optical axis to image a pattern from an object field in an object surface of the objective to an image field in an image surface region of the objective at an image-side numerical aperture NA with electromagnetic radiation from a wavelength band around a central wavelength ?. The optical elements include a concave mirror and a plurality of lenses. The projection objective forms an image of the pattern in a respective Petzval surface for each wavelength ? of a wavelength band, the Petzval surfaces deviating from each other for different wavelengths. In embodiments, a longitudinal departure p of the Petzval surface at a given wavelength from a planar reference surface at an edge field point of the image field (at maximum image height y?), measured parallel to the optical axis in the image surface region, varies with the wavelength ? according to dp/d?<(0.2?/NA2)/nm.

Abstract: A liquid lens includes a segmented electrode that allows the simultaneous application of different potentials across the lens's meniscus to obtain a predetermined aberration correction condition and to adjust focal length as necessary to conform to the topography of the object being scanned. The lens also includes a gas plenum interfacing with one of the liquids of the lens to allow for volume changes in the lens cell due to temperature variations. This combination of features produces a liquid-lens cell capable of maintaining substantially constant transverse magnification and diffraction-limited image quality over a useful range of focal length. As such, the lens is particularly suitable for incorporation in an array of micro-objectives used in a scanning microscope.

Abstract: An objective optical system for endoscopes has, in order form the object side, a single lens with negative power, a cemented lens with positive power, and an image sensor unit. The cemented lens has a plano-convex lens, located at the image-side end, with a convex surface facing the image side and an aperture stop placed proximate to a cemented portion and the image sensor unit includes an optically cemented body of at least one optical part, a path bending prism, and a solid-state image sensor to satisfy the following conditions: 1.5<TB/f<3.5 2.4<TC/f<4 where f is the focal length of the whole of the objective optical system, TB is the optical path length of the cemented lens, and TC is the optical path length of the image sensor unit.

Abstract: An optical system for arranging between a light source and a field diaphragm in an illumination beam path of a microscope comprises n imaging optical elements with focal lengths fi and Abbe numbers ?i (i=1, . . . , n). The following relationship is met for the optical system: ? i = 1 n ? h i f i · v i ? 0.07 , where hi is one half of the bundle diameter of a bundle of light rays proceeding from a point of the light source at the entrance to the imaging optical element i.

Abstract: A microscope objective having at least four lenses or groups of lenses and which can be used to improve image contrast. According to the invention, a phase plate, aligned concentrically to the optical axis, can be integrated into and taken out of the air space between the first lens and the second lens, as viewed from the object side. The defined arrangement of the phase plate and the associated shift of the real pupil into the air space between the first two lenses or groups of lenses, respectively, of the microscope objective allows a microscope objective, initially designed as a bright-field variant, to be redesigned as a phase contrast variant with relative ease.

Abstract: An object lens includes a first optical system that obtains a magnified image of an object, a second optical system that guides dark field illumination light to the object, a barrel that contains the first optical system and the second optical system and has an optical path around the first optical system for the dark field illumination light, and a shield mechanism that is disposed on the optical path and that varies the incident area of the dark field illumination light to shield the dark field illumination light.

Abstract: Especially when observing brain tissue, damage inflicted on the brain tissue is reduced, and light from the brain tissue is collected to the utmost extent. The invention provides an objective lens in which a tip transparent member that is made to contact an observation object is formed to gradually narrow towards an end face thereof, a diameter d of the end face being defined by the following expression, and a maximum diameter D being 3 mm or less: 0 mm?d?FOV?2×WD×(NA/N)?0.3 mm where FOV is the observation field of view, WD is the working distance, NA is the numerical aperture, and N is the refractive index of the observation object.

Abstract: The invention is directed to an objective, particularly for telescope-type stereomicroscopes. The objective comprises two lens groups, a first lens group and a second lens group. The first lens group, which faces the object plane, has a positive refractive power and comprises a plurality of lenses of which at least two form a cemented component. The second lens group, which is on the image side, has a negative refractive power and comprises a collecting cemented component and a diverging lens. The objective is characterized in that the following conditions B1 and B2 are met: where DAP represents the diameter of the exit pupil of the objective and ?1 represents the maximum field angle.

Abstract: Far-field sub-diffraction optical lenses “FaSDOLs” comprise an anisotropic crystal having special dispersion characteristics such that it supports diffraction free propagation. An image with subwavelength features on the input surface is transferred through a propagation function to the output surface with effectively no, or minimal, loss in information. These special properties may be exploited in several ways, including but not limited to, magnification of an image at the input surface through the use an oblique cut at the output surface, magnification of an image at the input surface through use of a curved crystalline structure, and more generally near-field optical processing.

Abstract: The invention relates to a microscope objective with preferably anti-symmetric lenses or lens groups with an optical magnification of ?100 and a visual field factor of 20. According to the invention the microscope objective consists of 9 lenses with 3 cemented elements, starting from the object side (left), a lens which is almost a hemisphere L1 with positive refractive power, a meniscus lens L2 with positive refractive power, a two-part cemented element G1 with positive refractive power, another two-art cemented element G2 with positive refractive power, a two-part cemented element G3 with negative refractive power, and finally a meniscus lens L9 with negative refractive power. By using cemented elements and lens pairings of the same construction, production costs can be reduced compared with methods of the prior art while image contrast is improved.

Abstract: An immersion objective lens includes a front lens, a lens frame which supports the front lens, and a liquid preventive frame which is attached around the lens frame. The liquid preventive frame includes a liquid bulb holding wall which holds a liquid supplied onto the front lens. A distal end of the liquid bulb holding wall is located more inner in the front lens in a direction parallel to a center axis of the front lens than a distal end face of the front lens.

Abstract: A solid immersion lens has an inclined portion formed on at least a part thereof from the tip end portion of the objective side to a spherical portion and an inclination angle ? is expressed as ???i where ?i represents the angle of incidence of light incident on the solid immersion lens. There are provided a solid immersion lens capable of increasing a tilt margin between a lens and an optical recording medium and so on and which can decrease a diameter of a lens and a method for forming a solid immersion lens.

Abstract: A plurality of microscope-use components are provided for interconnection in a microscope system. Each of the microscope-use components includes a communication interface which enables communication with a control apparatus of the microscope system by a prescribed communication system; a connection component-related information obtainment unit for obtaining connection component-related information that is related to another microscope-use component from a connectable other microscope-use component; and a control unit for transmitting, to the control apparatus of the microscope system by way of the communication interface, the connection component-related information of the other microscope-use component obtained by the connection component-related information obtainment unit and microscope-use component itself-related information that is related to the present microscope-use component.

Abstract: An observation or measurement device has, at least, an infinity-corrected objective lens and an imaging lens, and satisfies a condition, 4.56?D·NA??30 (mm), where D is the parfocal distance of the objective lens and NA? is the numerical aperture of the imaging lens. It is desirable to make a distance from the mount position of the objective lens to the most object-side surface of the imaging lens variable and to satisfy a condition, 0.5 FL<W<1.2 FL (mm), where W is the variable amount of the distance from the mount position of the objective lens to the most object-side surface of the imaging lens, and FL is the focal length of the imaging lens. It is more desirable to satisfy conditions, 0.4<D/FL<5 and 1?D/?d<3, where ?d is the outside diameter of a connection at the mount of the objective lens.

Abstract: A microscope has an oil immersion system objective and an imaging lens to make observations by charging oil between a cover glass protecting a sample and the most sample-side lens surface. At least one of a plurality of lens units, placed on the image side of the most sample-side lens in the oil immersion system objective, is moved along the optical axis, and thereby a front focal distance and a front focal position can be adjusted so that a predetermined depth position of the sample is focused in a state where a working distance WD between the cover glass and the most sample-side lens surface in the oil immersion system objective is set to a condition, 0<WD?0.03 mm.

Abstract: A device driving a corrector ring of a corrector ring mounting objective lens mounted to an objective mounting and dismounting section of a revolver includes a rotation driving mechanism having a motor and a turning effort transmitting section which transmits a turning effort of the motor to the corrector ring of the corrector ring mounting objective lens mounted to the revolver to drive the corrector ring; and a connection unit for connecting the turning effort transmitting section to the corrector ring of the corrector ring mounting objective lens introduced into an observation optical path in association with a switching operation performed by the revolver and disconnecting the turning effort transmitting section from the corrector ring of the corrector ring mounting objective lens removed from the observation optical path.

Abstract: The invention relates to a microscope having an optics system which represents an object on an image sensor and a screen that shows the image data provided by the image sensor and which is the only output medium for visually observing the object, wherein the representation capability of the optics system and the resolution (A) of the image sensor complies with the following correlation: F×N/M=0.5 A, wherein F indicates a factor, N indicates the numerical aperture of the optics systems, M is the magnification factor and A indicates the resolution of the image sensor in pixels per millimeter.

Abstract: A stereomicroscope has, in order form the object side, a single objective lens system; afocal relay optical systems, each including a front lens unit with positive refracting power and a rear lens unit with positive refracting power and having an intermediate image between the front lens unit and the rear lens unit; variable magnification optical systems; a plurality of aperture stops including at least aperture stops for right and left eyes, located at positions decentered from the optical axis of the objective lens system; and a plurality of imaging lens systems located at positions corresponding to the plurality of aperture stops. In this case, when each of the variable magnification optical systems lies at the low-magnification position, an entrance pupil of an optical system ranging from the objective lens system to each of the imaging lens systems is located closest to the objective lens system to satisfy the following condition: 0<L—enp—w/f—ob<0.

Abstract: An imaging module for endoscopes includes a convex lens and an image sensor in which mutual positions are fixed and a plurality of optical modules that are selectively mountable with respect to the fundamental module so that the observation condition is switched in accordance with an optical module selectively mounted. The imaging module for endoscopes is constructed so that when each of the optical modules is mounted to the fundamental module, an image position and an angle of oblique incidence of light of an observation image on the image sensor are practically unchanged.

Abstract: A microscope objective system including an objective, which includes an illumination beam path via which illumination radiation from a source is directed onto an object to be examined, as well as a partial detection beam path surrounding at least part of the illumination beam path and, together with the illumination beam path, forms a detection beam path via which radiation to be detected and coming from the sample is guided towards a detector.

Abstract: The invention is directed to an objective for telescope-type stereomicroscopes with magnification that can be adjusted at post-magnification systems. The objective, which comprises two lens groups LG1 and LG2, satisfies the two conditions DAP?42 mm, and tan(?)?0.16, where DAP is the diameter of the exit pupil and ? is the field angle of the objective at the lowest possible magnification setting. When this condition is met, the optical axis of the objective lies midway between the center lines of the two post-magnification systems. In preferred constructions, the total focal length f?objective of the objective is between 40 mm and 160 mm, and the relationship of the focal length f?LG2 of the second lens group LG2 to the total focal length f?objective is expressed by 0.1?1.8723/f?objective?1/f?LG2?0.2?1.8723/f?objective.

Abstract: A microscope illumination apparatus includes a light source, a collector lens for converting a light ray from the light source into an almost collimated light flux, a field stop provided in the almost collimated light flux from the collector lens, a field lens for converting a light ray from the field stop into an almost collimated light flux, and a condenser lens for collecting the almost collimated light flux from the field lens on a sample surface. The distance between the condenser lens and the field lens is variable.

Abstract: A projection optical system comprises a plurality of lenses disposed along an optical axis of the projection optical system; wherein the plurality of lenses is dividable into four non-overlapping groups of lenses of positive and negative refractive powers, wherein the following relation is fulfilled: 2 · y · NA · 1 k · ? i = 1 k ? ? ? i ? ? V 1 wherein: y is half a diameter in mm of a maximum image field imaged by the projection optical system, NA is a maximum numerical aperture on a side of the second object, ?i is a refractive power in mm?1 of the ith lens, k is a total number of lenses of the projection optical system, and wherein V1 is greater than 0.045.

Abstract: A vision enhancing device for a person having macular degeneration of the retina, comprises a lens and a light diverging surface on the lens that symmetrically diverges away from the eye at an angle relative to an optic axis to redirect incident light away from the optic axis outwardly toward an un-diseased region of the retina. The light diverging surface can be a smooth surface, which can be a continuous curved surface, and can be a diverging conical surface. The lens can be an eyeglass lens, contact lens, intraocular lens, telescopic lens, correction lens, or magnification lens. A light diverging insert having a conical surface and, optionally, an end surface can be used in a lens for redirecting light to the un-diseased region of the retina.

Abstract: An immersion type microscope objective is configured by, in order from the object side to an image side, a positive lens group Ga including a cemented lens obtained by cementing a plano-convex lens whose plane surface faces the object side to a meniscus lens whose concave surface faces the object side, and a positive single lens, a positive lens group Gb including a cemented lens, a lens group Gc including at least one cemented lens, a lens group Gd having a meniscus lens having a strongly concave surface that faces the image side, and a lens group Ge having a negative lens having a strongly concave surface that faces the object side.

Abstract: An immersion microscope objective formed of thirteen or fewer lens elements includes, in order from the object side, first and second lens groups of positive refractive power, a third lens group, a fourth lens group having negative refractive power with its image-side surface being concave, and a fifth lens group having positive refractive power with its object-side surface being concave. The first lens group includes, in order from the object side, a lens component that consists of a lens element of positive refractive power (when computed as being in air) and a meniscus lens element having its concave surface on the object side. Various conditions are satisfied to ensure that images of fluorescence, obtained when the immersion microscope objective is used in a laser scanning microscope that employs multiphoton excitation to observe a specimen, are bright and of high resolution. Various laser scanning microscopes are also disclosed.

Abstract: The invention concerns an objective (1) for an observation device (10), whereby the objective comprises an objective-lens-system, which consists of a first optical subcomponent (11, 14) on the object side and a second, optical subcomponent (12, 15), whereby the second optical subcomponent (12, 15) is arranged at a distance (d2) to the first optical subcomponent (11, 14) on the optical axis of the objective, and one of the subcomponents (12, 14) possesses a positive refractive power and the other subcomponent (11, 15) possesses a negative refractive power, which is hereby characterized in that the objective (1) has a zooming device. In addition, the invention concerns a microscope, which contains such an objective. Finally, a method for adjusting an objective (1) of an observation device (10) is provided with the invention.

Abstract: A liquid lens includes a segmented electrode that allows the simultaneous application of different potentials across the lens's meniscus to obtain a predetermined aberration correction condition and to adjust focal length as necessary to conform to the topography of the object being scanned. The lens also includes a gas plenum interfacing with one of the liquids of the lens to allow for volume changes in the lens cell due to temperature variations. This combination of features produces a liquid-lens cell capable of maintaining substantially constant transverse magnification and diffraction-limited image quality over a useful range of focal length. As such, the lens is particularly suitable for incorporation in an array of micro-objectives used in a scanning microscope.

Abstract: An objective lens comprises a housing, an iris diaphragm and a plurality of lens groups. For focusing the objective lens while minimizing the variation of the image angle at least two lens groups are adapted to be moved relative to the housing. The one lens group is arranged in front of the iris diaphragm. The other lens group is arranged at least partially behind the iris diaphragm.

Abstract: An optical system enables images of a wide range of natural subjects to be well reproduced with their colors, and provides an image pickup system including, at least, an image pickup optical system, an electronic image pickup device having three or more different spectral characteristics to obtain a color image, and a controller for implementing signal processing or image processing on the basis of an output from the electronic image pickup device. The optical element that takes part in the determination of a focal length in said image pickup system includes an optical element making use of a refraction phenomenon alone.

Abstract: A projection objective of a microlithographic projection exposure apparatus has a last optical element on the image side which is plane on the image side and which, together with an image plane of the projection objective, delimits an immersion space in the direction of an optical axis of the projection objective. This immersion space can be filled with an immersion liquid. At least one liquid or solid volume having plane-parallel interfaces can be introduced into the beam path of the projection objective, the optical thickness of the at least one volume being at least substantially equal to the optical thickness of the immersion space. By introducing and removing the volume, it is possible to convert the projection objective from dry operation to immersed operation in a straightforward way, without extensive adjustments to the projection objective or alignment work.

Abstract: A multiple-axis imaging system having optical elements whose optimal image positions can be individually adjusted, comprising a plurality of optical array elements having respective optical axes and being individually disposed with respect to one another to image respective sections of an object; and a plurality of image position shifting devices corresponding to respective optical elements for separately establishing the image positions for a plurality of the optical array elements. The multi-axis imaging system preferably comprises a miniaturized microscope array. The shifting devices may comprise wavelength filters or optical-path-length-altering elements, such as a plane parallel plates. The devices may also comprise a pair of wedges that adjustably overlap one another, the wedges having apexes that point in opposite directions and respective corresponding planar surfaces that are parallel to one another.

Abstract: The invention is directed to a high-aperture optical imaging system, particularly for microscopes, which comprises an objective and a tube lens unit and in which the objective has a magnification of less than or equal to 40× and a numerical aperture of greater than or equal to 1.0 and is chromatically corrected up to the infrared.

Abstract: A reticle-masking (REMA) objective for imaging an object plane onto an image plane has a condenser portion, an intermediate portion, and a field lens portion. The three portions together have no more than 10 lenses with a combined total of no more than five aspheric lens surfaces. Each of the three portions of the REMA objective has one or two aspheric lens surfaces.

Abstract: A lens module (10) includes a lens barrel (11), at least one fixed focus lens (12) fixed in the lens barrel, and at least two variable focus lenses (13) fixed in the lens barrel. Each variable focus lens includes two electrodes (151) and an electro-optical material (153) between the electrodes. Each electrode is electrically connected to a voltage supply so as to be able to selectively apply a voltage to the electro-optical material and to thus selectively control the refractive index of that material. By changing the refractive index, a concordant change in the focus of a given variable focus lens is possible, without modifying the position and/or shape thereof.

Abstract: Provided is a microscope having an immersion objective lens, a nozzle, and a liquid supplying mechanism. The immersion objective lens condenses light from a sample through liquid. The nozzle supplies the liquid to an upper surface of the immersion objective lens. The liquid supplying mechanism cooperates with one of a lens moving mechanism that moves the immersion objective lens and a sample moving mechanism that maintains and moves the sample, and moves the nozzle relative to the immersion objective lens to supply the liquid.

Abstract: A method of adjusting a projection objective permits the projection objective to be adjusted between an immersion configuration and a dry configuration with few interventions in the system, and therefore to be used optionally as an immersion objective or as a dry objective. The projection objective has a multiplicity of optical elements which are arranged along an optical axis of the projection objective, the optical elements comprising a first group of optical elements following the object plane and a last optical element following the first group, arranged next to the image plane and defining an exit surface of the projection objective which is arranged at a working distance from the image plane. The last optical element is substantially without refracting power and has no curvature or only slight curvature.

Abstract: A microscope system includes a light source and an objective unit. The objective unit includes an objective optical system, including a small-diameter distal optical system arranged at an end brought near to or into contact with a specimen, for focusing light from the light source onto the specimen; a threaded mount at a coupling position; and an outer cylinder enclosing the small-diameter distal optical system. The microscope system further includes an imaging optical system for forming an image of light from the specimen through the objective optical system and a microscope main body for housing the imaging optical system. The objective unit is detachable from and attachable to the microscope main body with the threaded mount. Conditional expression Df/Da?0.3 is satisfied, where Df represents the outer diameter of the outer cylinder and Da represents the outer diameter of the threaded mount.