Abstract: An aperture stop device is provided for use in a microscope with at least one adjustable observation parameter. The aperture stop device includes at least one aperture stop (50a, 50b) with an adjustable aperture, that is to say with an adjustable stop opening. The aperture stop (50a, 50b) is adapted to receive an aperture signal representative of an aperture to be adjusted. In addition the aperture stop device includes a control unit (52) for output of the aperture signal to the aperture stop (50a, 50b) in dependence at least on the respectively set value of the observation parameter of the microscope.

Abstract: A scanning microscope includes an objective lens for focusing illumination light onto a specimen; a scanning device for deflecting and scanning the illumination light; a pupil-projection optical system for illuminating a pupil of the objective lens with the scanned illumination light; and a total-magnification specifying unit for specifying a total magnification. An optical-system selecting unit changes at least one of the objective lens and the pupil-projection optical system such that a magnification of an optical system including the objective lens and the pupil-projection optical system is equal to or less than the total magnification specified by the total-magnification specifying unit and that the numerical aperture of the optical system is maximized. A deflection-angle determination unit determines a deflection angle of the illumination light deflected by the scanning device based on the ratio of the magnification of the optical system to the total magnification to achieve the total magnification.

Abstract: An ultra-broadband ultraviolet (UV) catadioptric imaging microscope system with wide-range zoom capability. The microscope system, which includes a catadioptric lens group and a zooming tube lens group, has high optical resolution in the deep UV wavelengths, continuously adjustable magnification, and a high numerical aperture. The system integrates microscope modules such as objectives, tube lenses and zoom optics to reduce the number of components, and to simplify the system manufacturing process. The preferred embodiment offers excellent image quality across a very broad deep ultraviolet spectral range, combined with an all-refractive zooming tube lens. The zooming tube lens is modified to compensate for higher-order chromatic aberrations that would normally limit performance.

Abstract: A lens system comprises a first lens group and a second lens group, and is configured to form an image at a first magnification and at a second magnification. The lens system has a common optical axis in both magnifications. The lens system is further configured to form an intermediate image between the first lens group and the second lens group at the first magnification. The intermediate image formed in the first magnification is further imaged onto an optical detector. In the first magnification, the second lens group acts as a relay lens imaging the intermediate image onto the optical detector. In the second magnification, the first and second lens groups together form an image on the optical detector without forming an intermediate image.

Abstract: A variable power relay optical system comprising: a variable power lens performing zooming a secondary image based on light from a primary image; and a rear group forming the secondary image based on the light passing through the variable power lens; the variable power lens consisting of, in order from the primary image side, a first group having positive power, a second group having negative power, a third group having positive power, and a fourth group having positive power, upon zooming from a high magnification end to a low magnification end, the fourth group being moved to the secondary image side, and a distance between the first group and the second group increasing, positions of the primary image and the secondary image, an entrance pupil of the variable power relay optical system, a pupil of the variable power lens, and an exit pupil of the variable power relay optical system being substantially kept constant, and the pupil of the variable power lens being disposed to the secondary image side of the

Abstract: A collection optics having variable magnification, and which enable changing magnification without stopping the spray cooling. The variable magnification is provided by a turret that carries several objectives of different magnifications. A frame is provided above the turret, wherein the spray cooling is provided. By rotating the turret and changing its elevation, different objectives of the turret can be “docked” to a docking port within the frame.

Abstract: An optical imaging system is described, comprising a zoom system for adjusting a variable magnification of the image, wherein the zoom system comprises at least one of a lens assembly and a first SLM optical unit, and an illumination system for illuminating an object to be imaged in an object plane. The illumination system has a second SLM optical unit for adjusting the focal length within the illumination system. This design allows coordinating zoom system and illumination system with one another in a simple manner and provides a compact design.

Abstract: A portable magnifying instrument useful for colposcopy is provided which may include in combination an optical system capable of providing a distortion free clear continuously varying 10× to 15× magnification of a three-dimensional wide object; an integrated energy efficient, low powered and intensity controlled illumination system; a power pack and mounting. The optical system may have an eyepiece lens system and an objective lens system. The illumination system may have a plurality of light emitting diodes (LEDs) connected to the power pack; mounted in such a manner that the angle between the LEDs is maintained with respect to the optical axis of the lens system and that the light beam from the said LEDs impinges on the wide object to be observed at the focus of the said lens system.

Abstract: A laser scanning microscope comprises: an objective lens for observing a specimen; a focal plane scan lens placed on the opposite side of the objective lens from the specimen and which generates an intermediate image; a mirror placed near to the position of the intermediate image of the focal plane scan lens; a scan unit scanning the mirror in the optical axis direction; and a pupil projection optical system which projects the pupil of the objective lens onto the pupil of the focal plane scan lens and of which the pupil projection magnification ratio is variable.

Abstract: It is an object to provide a zoom microscope of a simple structure which can expand a variable-power range. In order to achieve the object thereof, the zoom microscope includes a replaceable infinity correction objective lens, an aperture stop, an afocal zoom system, and an imaging optical system which are arranged in this order from a specimen side. Further, the aperture stop is disposed on or near a rear focal plane of the objective lens.

Abstract: An optical apparatus minimizes autofluorescence and stray light as well as leakage of excitation light and efficiently utilizes illuminating light from a fluorescence illumination optical system to allow observation of a bright fluorescence image. An observation apparatus has an objective, an observation optical system unit including a variable magnification optical system, and an imaging optical system unit including an imaging lens and an eyepiece. A fluorescence illumination apparatus, which is provided separately, is removably attached to the observation apparatus. The fluorescence illumination apparatus has a light source, a collector lens unit, and a reflecting member placed between the objective and the observation optical system unit at a position displaced from the optical axis of the objective to make light from the light source incident on the objective. An excitation filter is provided between the light source and the reflecting member.

Abstract: The purpose is to move an observation field of view of a microscope without moving or changing an objective lens without varying position or state of a sample. A microscope optical system according to the present invention has a mirror that changes the direction of the optical path by reflection and locates in the optical path between an objective lens of the microscope and an image to be observed. The mirror is able to be tilted with changing the position of a reflecting surface of the mirror. Accordingly, the observation field of view is moved by tilting the mirror. In other words, the observation field of view can be moved without changing positional relation between the objective lens of the microscope and the sample.

Abstract: An observation field of view of a microscope can be moved without moving or changing an objective lens and without varying position or state of a sample. A microscope optical system has a mirror that changes the direction of the optical path by reflection. The mirror is located in the optical path between an objective lens of the microscope and an image to be observed. The mirror can be tilted to change the position of a reflecting surface of the mirror. Accordingly, the observation field of view is moved by tilting the mirror without changing a positional relation between the objective lens of the microscope and the sample.

Abstract: It is an object to provide a zoom microscope of a simple structure which can expand a variable-power range. In order to achieve the object thereof, the zoom microscope includes a replaceable infinity correction objective lens, an aperture stop, an afocal zoom system, and an imaging optical system which are arranged in this order from a specimen side. Further, the aperture stop is disposed on or near a rear focal plane of the objective lens.

Abstract: An optical image system surface resolution calibration method is provided herein, which utilizes a calibration standard and an image sensor device. The surface of the calibration standard is provided with a plurality of interleaving bright lines and dark lines, the calibration standard is disposed in a plane to be measured, and the image sensor device is provided with an imaging means, a memory means, and a logic-arithmetic means, that is used to fetch the image information of the calibration standard and store the image information thus obtained. Meanwhile, the image sensor device is used to select and calculate the linear equations of the bright lines, and finally calculate the magnification factor of the image fetched by the image sensor device through the geometric mathematical means by making use of the slope and intersection distance of the linear equation and the average distance between the adjacent bright lines calculated from the intersection distance.

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: 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: An apparatus for setting a divergence and/or convergence of a light beam includes at least one optical component for influencing the divergence and/or convergence of the light beam. A positioning device is provided for positioning the optical component. The positioning device includes at least one piezoelectric element.

Abstract: A microscope includes a switching mechanism which has a plurality of lens units, and which inserts a selected lens unit of the plurality of lens units into an observation light path and disposes the non-selected other lens units outside the observation light path. A control unit controls a movement speed of a stage, onto which a sample is placed, in an optical axis direction according to an observation power of the selected lens unit inserted into the observation light path. The plurality of lens units include: (i) a plurality of fixed-power lens units which are lens units including a combination of imaging lenses and objective lenses, and whose observation powers when observing the sample mutually differ, and (ii) a zoom lens unit which has a continuously changeable observation power.

Abstract: The invention concerns a method for operating an optical system (1) as well as an optical system. In the method an object of study is spatially imaged in an image plane using a microscope (2) comprised in the optical system (1), wherein the microscope (2) comprises at least one lens system which is assigned to a respective optical path (3, 4) and a collecting lens arrangement (11) which is assigned to the optical paths or optical paths (3, 4), wherein the at least one lens system comprises a first lens arrangement (3a; 4a) and a second lens arrangement (3b; 4b) positioned between the first lens arrangement (3a; 4a) and the collecting lens arrangement (11).

Abstract: A stereoscopic microscope according to the invention includes an observing optical unit 10 that has a zoom optical system 501 having variable zoom power and an objective lens 63 optically connected to the zoom optical system 501, and that receives observing light emitted from a specimen 2. The stereoscopic microscope also includes an illuminating unit 7 that emits illuminating light to illuminate the specimen 2. The microscope further includes a near co-axial epi-illuminatory optical system that has a reflecting mirror 13 disposed in the observing optical unit 10 but out of the optical path of the zoom optical system 501, and that illuminates the specimen 2 with illuminating light via the reflecting mirror and objective lens 6.

Abstract: A surgical observation system provided with a supporting arm movable in the three-dimensional direction includes an endoscope objective unit having a tubular insertion section and provided with objective optical systems, a microscope objective unit provided with objective optical systems having a focusing optical system and variable magnification optical systems, and a mounting and dismounting section provided in the supporting arm, mountable and dismountable with respect to the objective units by having interchangeability.

Abstract: A zoom microscope includes an observation optical system having an exchangeable objective lens, an aperture diaphragm, an afocal zoom system, and an image forming optical system; and a zoom epi-illumination optical system. The zoom epi-illumination optical system has an optical path which is also the optical path of the observation optical system between the objective lens and the afocal zoom system so as to illuminate an object by incident light. In the zoom epi-illumination optical system, an image of a light source is formed in the vicinity of the pupil position of the objective lens. This realizes a zoom microscope capable of performing fluorescent epi-illumination without shading in all the magnification ranges.

Abstract: An optical arrangement having an optical assembly (1) for generating an intermediate image (2) in a beam path is configured and further developed such that an optical element (3) having a plurality of optical waveguides (4) is arranged in the beam bath after the intermediate image (2) to enable the imaging of the intermediate image (2) in a plane on a zone-by-zone or point-by-point basis. Further, a microscope exhibiting such an optical arrangement is specified.

Abstract: For a confocal scanning electron microscope (1) an optical zoom system (41) with linear scanning is provided, which not only makes a zoom function possible, in that a variable magnification of an image is possible, but rather which additionally produces a pupil image in the illuminating beam path (IB) [BS] and thereby makes a variable imaging length possible (distance between the original pupil (En.P) [EP] and the imaged/reproduced pupil (Ex.P) [AP]) so that axially varying objective pupil positions can thereby be compensated.

Abstract: A microscope having a night vision apparatus, which apparatus can be impinged upon by beam paths proceeding from a specimen or object to be observed.

Abstract: A scanning microscope includes an objective lens for focusing illumination light onto a specimen; a scanning device for deflecting and scanning the illumination light; a pupil-projection optical system for illuminating a pupil of the objective lens with the scanned illumination light; and a total-magnification specifying unit for specifying a total magnification. An optical-system selecting unit changes at least one of the objective lens and the pupil-projection optical system such that a magnification of an optical system including the objective lens and the pupil-projection optical system is equal to or less than the total magnification specified by the total-magnification specifying unit and that the numerical aperture of the optical system is maximized. A deflection-angle determination unit determines a deflection angle of the illumination light deflected by the scanning device based on the ratio of the magnification of the optical system to the total magnification to achieve the total magnification.

Abstract: An ultra-broadband ultraviolet (UV) catadioptric imaging microscope system with wide-range zoom capability. The microscope system, which comprises a catadioptric lens group and a zooming tube lens group, has high optical resolution in the deep UV wavelengths, continuously adjustable magnification, and a high numerical aperture. The system integrates microscope modules such as objectives, tube lenses and zoom optics to reduce the number of components, and to simplify the system manufacturing process. The preferred embodiment offers excellent image quality across a very broad deep ultraviolet spectral range, combined with an all-refractive zooming tube lens. The zooming tube lens is modified to compensate for higher-order chromatic aberrations that would normally limit performance.

Abstract: A projection electronic microscope is provided for improving geometric aberration and a space charge effect within a zooming range using a zoom type transfer lens system in a projection/image formation optical system. The projection electronic microscope comprises an irradiation system for emitting a primary electron beam irradiated to a sample, and a projection/image formation optical system for guiding a second electron beams emitted from the sample with the irradiation of the primary electron beam to a detection system. The projection/image formation optical system includes a zoom type transfer lens system having a first zoom lens and a second zoom lens. The first zoom lens includes a plurality of electrodes.

Abstract: For a confocal scanning electron microscope (1) an optical zoom system (41) is provided, which not only makes a zoom function possible, in that a variable magnification of an image is possible, but rather which additionally produces a pupil image in the illuminating beam path (IB) [BS] and thereby makes a variable imaging length possible (distance between the original pupil (En.P) [EP] and the imaged/reproduced pupil (Ex.P) [AP]) so that axially varying objective pupil positions can thereby be compensated.

Abstract: A zoom lens system for a microscope includes, in the following order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. Magnification of the zoom lens system is varied by moving the second lens group and the third lens group. The zoom lens system has an entrance pupil on the object side of the first lens group, and the following conditions are satisfied: ?1.3<?2H<?0.7 ?0.1<1/?3L<0 where ?2H is the magnification of the second lens group in the highest magnification state, and ?3L is the magnification of the third lens group in the lowest magnification state.

Abstract: The invention is directed to an immersion microscope objective. An objective of this kind has an adjusting element, for example, a correction ring, by which it can be adjusted to different immersion media. In an advantageous manner, the objective can also be adjusted to different temperatures of the solutions and different coverslip thicknesses of object vessels by the correction ring.

Abstract: Apparatus and method for viewing a target. A primary lens produces an image plane of the target, and an optical magnifier in an optical path of the primary lens magnifies a region of the image plane, providing a magnified image. A detector receives the magnified image.

Abstract: A method and apparatus for dynamically focusing an imaging mechanism on a moving target surface having a variable geometry is herein disclosed. Apparatus for focusing an imaging mechanism may include an objective, a prism, or another optical device that forms part of an optical train of an imaging mechanism, a sensor for measuring a distance to the target surface, and a mechanism for modifying the depth of focus of the objective, prism or other optical device. Data from the sensor may be used to create a predictive model of the target surface. Data from the sensor is also used to fit or correlate the generated model to an exemplary target. Data from the correlated model is used to drive the mechanism for modifying the depth of focus of the objective, prism, or other optical device to maintain the surface of the exemplary target in focus.

Abstract: An observation state obtainment unit obtains an observation state of a microscope at the time of obtaining the microscopic image of a specimen obtained by using the microscope. A motion image data generation unit generates data of a motion image from the microscopic images of a time series. A correlation addition unit adds, to data of the motion image, information that correlates microscopic images constituting the motion image with an observation state of the microscope at the time of obtaining the microscopic images. A record unit records data of the motion image and an observation state of the microscope correlated with the data.

Abstract: A magnification correction device 1 includes magnification correction optics 2, a pressure adjustment device 3 and a controller 4. The magnification correction optics 2 is formed in a shape of a box with a glass plate 20 and a bottom plate 11 positioned parallel to the glass plate 20 and a frame 10. The inside of the box is an air room 24 connected to a pressure adjustment device 3 via a connecting pipe 12 so that the pressure of the inside can be changed. The cylinder 30 is driven by a motor 35 via a linear movement unit 36 such as a ball screw and the motor 35 is controlled by a controller 4. The moving distance of cylinder 30, which is equal to the moving distance of the piston, is decided by the number of the revolutions of the motor 35, and the capacity of the closed circuit of the pressure adjustment device 3 is also decided.

Abstract: A stereoscopic microscope including a light source section, an illumination optical system, and an observation optical system. The illumination optical system has an optical axis and includes a projection optical system. The projection optical system forms an intermediate image and irradiates a light flux from the light source section onto an observation object. The observation optical system includes an objective lens, a pair of left and right zooming optical systems for changing the magnification of the observation optical system, and a pair of left and right eyepiece optical systems. A center position of the light source section is de-centered from the optical axis of the illumination optical system. Also, the illumination optical system includes a reflecting member which has two rounded notches and is inserted into and removed from a space on the object side of the objective optical system in conjunction with a zooming operation.

Abstract: Illumination systems which are designed to illuminate a field in a field plane and simultaneously illuminate a pupil plane with radiation from a light source are disclosed.

Abstract: An observation device including an intermediate tube that houses two relay optical systems and an image rotator, each relay optical system having an exit axis that is substantially parallel to the exit axis of the other relay optical system, and an ocular tube that houses two image formation optical systems and two eyepiece optical systems. The intermediate optical tube has a connecting portion that connects to a connector at the top of a stereoscopic microscope body at one end and is rotatably connected to the ocular tube at the other end, the ocular tube is extendable from, and collapsible into, the intermediate tube over a movement range in the direction of the exit optical axes of the pair of relay optical systems, and exit pupils of the pair of relay optical systems are arranged near a middle position of the range of movement of the ocular tube.

Abstract: An optical magnification device for varying the distance between an observer's eye (1) and an object (7), e.g., for a binocular magnifier or a microscope, in which focusing onto the object (7) is accomplished by means of progressive lenses (3) displaceable perpendicular to the observation beam(s) (2).

Abstract: A stereo microscope includes two oculars mounted at one end of a housing and an objective lens mounted at an opposite end of the housing. Between the opposite ends of the housing is a rotatably mounted lens magnification changer with three series of bores extending diametrically therethrough. For each ocular, a line of sight extends to a prism assembly, through one of the bores of a series which contains a lens assembly and through the objective lens. Both lines of sight lie in a common plane. A LED light source is located adjacent the objective lens. Light entering through the objective lens and one of the series of bores in the lens magnification changer is received by a digital camera.

Abstract: A microscopic image capturing apparatus and method are provided. First, the entire area of a slide glass on a stage is divided into field size sections (low-magnification sections) of a low-powered objective lens. The stage is transferred perpendicular to an optical axis, and image information is sequentially obtained for each low-magnification section. Each low-magnification section is divided into high-magnification size sections (high-magnification sections), and a high-magnification image is captured using a high-powered objective lens only in high-magnification sections corresponding to a sample. A high-magnification image is generated by correctly maintaining the relative position between the obtained image information and an area corresponding to high-magnification sections which are not captured, and high-magnification composite image information of the sample is generated.

Abstract: A microscope optical system comprises an objective lens and an intermediate magnification varying part disposed just after the image side of the objective lens. A microscope objective lens according to another aspect of the invention comprises a first lens group and a second lens group in the mentioned order from the object side. The first lens group includes a positive meniscus lens with the concave surface facing the object side and one or more cemented lenses, the first lens group having a positive refractive power as a whole, at least one of the cemented lenses includes a lens made of a material having an Abbe's number equal to or larger than 80, and conditions 0.3?wd/f?0.45 and 0.6?NA are satisfied, where f represents the focal length of the microscope objective lens as a whole, wd represents the working distance of the microscope objective lens, and NA represents the numerical aperture of the microscope objective lens.

Abstract: The present invention concerns a microscope 1. The microscope 1 encompasses a microscope stand 2, an objective 4 having an optical axis 5, a microscope stage 6 serving to receive a specimen 7, and a focusing device 20 serving to focus the specimen 7. With the focusing device 20, the objective or the microscope stage 6 is positionable relative to the microscope stand 2 in the direction of the optical axis 5 of the objective 4. The focusing device 20 comprises at least one operating element 8 with which an operator controls the positioning of the objective 4 or of the microscope stage 6. For adaptation of the spatial arrangement of the operating element 8 to the needs of an operator, the microscope 1 according to the present invention is characterized in that the spatial arrangement of the operating element 8 relative to the microscope stand 2 is modifiable.

Abstract: For a semiconductor device S as a sample of an observed object, there are provided an image acquisition part 1 for carrying out observation of the semiconductor device S, and an optical system 2 comprising an objective lens 20. A solid immersion lens (SIL) 3 for magnifying an image of the semiconductor device S is arranged movable between an insertion position where the solid immersion lens includes an optical axis from the semiconductor device S to the objective lens 20 and is in close contact with a surface of the semiconductor device S, and a standby position off the optical axis. Then an image containing reflected light from SIL 3 is acquired with the SIL 3 at the insertion position, and the insertion position of SIL 3 is adjusted by SIL driver 30, with reference to the image.

Abstract: A Combinatorial Optical Processor and method for the architecture of optical systems utilizes one or more optical modules, each module including a number of individually addressable optical elements. The optical elements are arranged and addressed in a combinatorial-arithmetic fashion such that a set of optical filter functions are defined, and can be performed, by the optical modules. The number of optical filter functions may be an exponential function of the number of addressable optical elements. Additionally, each of the optical filter functions may be addressed at random and a plurality of such functions may be addressed simultaneously. Apparatus, such as imaging systems, may employ the Combinatorial Optical Processor in order to include without limitation the features of being solid-state, projection of images into free space and random addressability of the filter functions of the system.

Abstract: A CPU determines an optical-axis direction moving interval of a focal point of a microscope based on a wavelength of light used for sample observation by the microscope and a numerical aperture of an object lens mounted on the microscope, and controls the microscope so as to sequentially move a position of the focal point of the microscope with respect to a sample position in the optical-axis direction at determined moving intervals. Every time the control moves the position, with respect to the sample position, of the focal point at the moving interval, the microscope is so controlled as to sequentially obtain a microscopic image produced when the position of the focal point is at a position after the moving.

Abstract: A real image type zoom finder that, albeit being reduced in size and thickness, can gain high enough zoom ratios and an imaging system equipped with such a real image type zoom finder. The real image type zoom finder comprises an objective optical system, an image-erection optical system and an eyepiece optical system. The objective optical system comprises a negative first lens group, a positive second lens group, a negative third lens group and a positive fourth lens group. Upon zooming, the first lens group and the fourth lens group remain fixed, the second lens group moves toward the object side at the telephoto, not the wide-angle end, and the third lens group moves toward the image side at the telephoto, not the wide-angle end. The first lens group consists of one single lens of double-concave shape, and that single lens satisfies condition regarding a shape factor.

Abstract: The invention concerns a stereomicroscope (1) for magnifying an object (T), having at least one zoom (22) through which, in the operating state, an object beam (K1) emitted from the object (T) is directed, the stereomicroscope (1) comprising a first deflection device (P4), arranged physically behind (after) the zoom (22) in the light path, for deflecting the light beam directed through the zoom (22) into a direction (A3) that deviates by less than 45° from the direction opposite to the object beam (K1). The light beam (A1) directed through the zoom (22) is advantageously deflected substantially into the direction opposite to the object beam (K1).

Abstract: The invention is directed to an afocal zoom system, particularly for use in microscopes, comprising at least four optical assemblies, two of which assemblies are movable relative to one another and to the rest of the assemblies for the purpose of changing the magnification. It is the object of the invention to develop an afocal zoom system which enables a relatively small structural size for a microscope also in combination with a suitable drive mechanism. This object is met by an afocal zoom system of the type described above in which every adjustable magnification can be achieved by a displacing movement of the two movable optical assemblies in the same direction.