Abstract: In a microscope such as for the examination of specimens in specimen vessels, a device for changing objectives is provided. The microscope includes at least a first objective. The device comprises an arrangement for providing an operating control so that the at least first objective can be raised and lowered vertically and is displaceable horizontally vertical to an optical axis of the microscope.

Abstract: A device for switching the operating modes of a microscope tube between the observation position, recording position and simultaneous observation and recording position, with a fully reflecting first element for full deflection of the radiation coming from the microscope objective, and with a partially reflecting second element for splitting the radiation coming from the microscope objective, wherein the first element and second element are arranged on a first guide carriage and second guide carriage which are displaceable jointly as well as opposite to one another in a plane.

Abstract: A microscope includes a light source for emitting light, a light condenser lens for condensing the light from the light source onto an object, a wavelength selection unit arranged between the light source and the light condenser lens for selecting the wavelength of the light entering the light condenser lens from the light source, a detector for detecting light from the object through the light condenser lens, and an optical path length adjusting unit arranged between the light source and the detector for adjusting the optical path length between the light condenser lens and the detector in order to correct the chromatic aberration of the light condenser lens appearing depending on the wavelength of the light selected by the wavelength selection unit.

Abstract: An optical element for microscopic inspection of a surface. The optical element has an elongated body defining an optical axis, with a first end adjacent the surface and a second end directed toward an imaging instrument. The body has a curved reflective surface and an optical aperture at the first end, and defines first and second associated focal points on the optical axis. The first focal point is spaced apart from the first end of the body, such that positioning the surface at the first focal point generates an image of the surface at the second focal point. The reflective surface may be paraboloidal, with a concentrating lens focusing collimated rays to the second focal point, so that a conventional microscope may view the image generated at the second point.

Abstract: An arrangement for generating a defined longitudinal chromatic aberration in a beam path of a confocal microscope. The arrangement includes using a confocal microscope with a microscope objective, and supplementary optics which are arranged in the imaging beam path of the microscope objective. The supplementary optics include at least two dual lens optical elements for generating the longitudinal chromatic aberration.

Abstract: A multi-beam light source unit includes a light source section having a plurality of semiconductor lasers, a plurality of collimating lenses for collimating light beams emitted from the semiconductor lasers, and a supporting member for supporting the plurality of semiconductor lasers and the plurality of collimating lenses arranged in a main scanning direction. There is a relation expressed by D/d.noteq.1 relating to a distance D between adjacent ones of the semiconductor lasers and a distance d of adjacent ones of the collimating lenses, and the light source section is supported so that it can be angularly adjusted so as to change a rotational position of the light source section including the semiconductor lasers and the collimating lenses.

Abstract: The invention relates to a compact microscope 4 especially for medical routine applications. The microscope is configured as a closed housing 8 wherein the specimen 30 to be microscoped is drawn in via an input opening 25. All optical components of the microscope are mounted within the housing. Alternatively, the microscope can be mounted in a standard drive bay of a personal computer 3. All movable components of the microscope are motorically driven and controlled by software via the computer. The specimen can be moved in two mutually perpendicular directions within the microscope to select the object detail of interest. An overview diagram of the specimen is produced with a line sensor when the specimen is drawn in.

Abstract: An auxiliary optical unit AU, which is removable on an object side of an objective lens of a microscope, has a built-in auxiliary lens group 15 having a negative refractive power. The auxiliary optical unit AU is provided with a focal point adjustment mechanism which shifts the auxiliary lens group 15 in the optical axial direction. By adjusting the auxiliary lens group 15, the telephoto focal point is shifted substantially to infinity when mounted to the objective lens system. The auxiliary optical unit AU is mounted so that the image plane of the auxiliary lens group alone is positioned, while the focus adjustment mechanism is focused at a substantially infinite focal point, where the object for the microscope to be observed is located.

Abstract: An exchangeable condenser system for a phase-contrast illuminating system (12) for microscopes has a plurality of different light rings (5), arranged on a nosepiece plate (4), assigned to the condenser optical system (6). The condenser optical system (6) can be exchanged independently of the light rings (5), the focal lengths F.sub.n of the exchangeable condenser optical systems (6) being selected relative to one another in the ratio F.sub.n =F.sub.0 *X.sup.n and the average diameters D.sub.n of the light rings (5) being selected relative to one another in the ratio D.sub.n =D.sub.0 *X.sup.n, where X>0, n=0,1,2,3, . . . .

Abstract: A revolver assembly of a microscope, for switching a current objective lens to one of a plurality of lenses by manual rotary operation of the revolver assembly, includes a revolver main body and a revolver rotary section rotatably coupled to the revolver main body for removably mounting thereon a plurality of objective lenses of the microscope. A holding member extends in a direction crossing a rotary axis of the revolver rotary section, and is immovable with respect to the revolver main body. A manually operable rotary operation section is arranged approximately parallel to the rotary axis of the revolver rotary section, and is coupled to the holding member so as to be manually rotatable around an axis which is separated from the rotary axis of the revolver rotary section by a predetermined distance.

Abstract: An optical-path switching apparatus for an optical microscope, which is simple structure, has a plurality of optical devices to be inserted and removed to and from at least two or more switching positions provided for optical paths so as to switch the optical paths. A drive force generator generates a drive force, and an insertion/removal device transmits the drive force generated by the drive force generator so as to insert and remove the plural optical devices to and from the switching positions while relating the plural optical devices to one another. A control unit controls switching of the optical devices to be performed by the insertion/removal device in order to obtain a required optical path.

Abstract: In a reflection type angle of view transforming optical apparatus for transforming an angle of view in an image apparatus and so forth, sufficient strength can be provided and process is facilitated by using reflecting mirrors in a wide angle optical system. The reflection type angle of view transforming optical apparatus includes a primary mirror 8 having a reflecting surface provided in an axisymmetric form to reflect incident light 12 as primary reflected light 13, a secondary mirror 10 having a reflecting surface provided in an axisymmetric form about the same axis of rotational symmetry 9 as that of the primary mirror 8, opposed to the primary mirror 8 so as to reflect the primary reflected light 13 and to get secondary reflected light 14 for focusing on a view point, and a transparent case 11 to support the primary mirror 8 and the secondary mirror 10, and transmit the incident light 12.

Abstract: The invention relates to a stereoendoscope having a sight line folded relative to the tube axis. The endoscope includes a distal front optic having a deflecting prism 4b. The deflecting prism 4b is mounted between a component 4a having a negative refractive power and a proximal component 4c having a positive refractive power. The inlet pupils 11 of the viewing component are imaged demagnified in the reflecting prism 4b by field optics (7, 7', 13) and transmitting optics (8, 8', 14). In this way, the beam can be guided free of vignetting without field cropping for both stereo channels through the endoscope tube and through the reflecting prism 4b even for a large object field angles and without image cropping. The endoscope tube 2 and the viewing component 1 are rotatable with respect to each other about the optical axis 12 within the endoscope tube 2 so that the line of sight can be changed for a viewing component fixed in space. The stereo basis remains for a rotation of the endoscope tube 2 fixed in space.

Abstract: A novel computer-controlled video microscopy system, features a rotatable objective lens turret. The lens turret is a rotatable cylindrical drum having an open end and closed end. A plurality of light-transmitting objective lenses are evenly spaced about the side wall of the cylindrical drum. The objective lenses are each directed perpendicularly to the axis of rotation of the cylindrical drum. A computer is used to select a desired objective lens and signal a motor to rotate the cylindrical drum about its axis of rotation, so as to move the selected objective lens into the path of an approaching light beam. When the light beam enters the drum through the objective lens, a prism or mirror inside the cylindrical drum bends the light beam at a right angle and directs it out of the drum through its open end. An image carried by the light beam is then focused onto the imaging plane of a video camera.

Abstract: A telescope is composed of an ocular (11), a roof prism (12) and a first objective lens (14). A microscope is composed by adding a second objective lens (22) in front of the first objective lens (14). By operating a lens shifting ring (5), the second objective lens (22) is rotated. A mirror (32) is provided in front of the second objective lens (22). By operating a mirror shifting ring (6), the mirror (32) is rotated. When both the second objective lens (22) and the mirror (32) are at their respective retreated positions, the equipment can be used as a telescope to look in the forward direction. When the mirror (32) alone is at the advanced position, the equipment can be used as a telescope to look laterally. When both the second objective lens (22) and the mirror (32) are at their respective advanced positions so that the light entering from the side can be used, the equipment is capable of magnifying an object (26) to be observed, which is placed on a slide (25) supported by slide insertion slots.

Abstract: A wide-angle viewing attachment for an ocular microscope includes a first lens attached to the microscope and a second lens independently mountable with respect to the microscope. The second lens is positionable proximal to an eye of a surgical patient and is maintained in the proximal position by an attachment system including a support member coupled in a fixed position to an operating table on which the patient is reclined. A first support rod extends vertically from the support member and a clamp member is adjustably mounted on the support rod. A horizontally extending second support rod is adjustably coupled to the clamp member and terminates at one end in a generally flat plate. A lens carrier includes a spring clamp for holding the second lens and a support arm extending generally horizontally with respect to the first support rod. The carrier terminates in a magnet assembly which holds the lens carrier to the flat plate.

Abstract: A reflecting illumination optical system for microscopes has a light source, a lamp house section including a collector lens with a focal length corresponding to the light source, and a reflecting projection tube section including a projection optical system for projecting the image of the light source at a position adjacent to the pupil of an objective lens. Further, a variable magnification section composed of a nearly afocal variable magnification lens unit is removably inserted between the reflecting projection tube section and the lamp house section, or in the interior of the reflecting projection tube section. Thus, when the lamp house section is replaced by another, the magnification of projection of the light source at the position adjacent to the pupil of the objective lens can be changed.

Abstract: A lens-barrel optical system of the present invention is a lens-barrel optical system for guiding a beam emerging from an objective optical system in a focused state to an eyepiece optical system, which includes (i) a deflecting prism having three internal reflecting surfaces arranged in a triangular prism, the deflecting prism successively reflecting a beam incident in a first direction parallel to the optical axis of the objective optical system by the three reflecting surfaces to let the beam travel in a substantially M-shaped optical path, thereby letting the beam emerge in a second direction opposite to the first direction; and (ii) a reflector for reflecting the beam emerging from the deflecting prism to guide the beam to the eyepiece optical system.

Abstract: An illuminating device for a stereo microscope having an objective with variable imaging focal intercept includes first coupling mechanism, which effects a coupling between the imaging focal intercept of the objective and the likewise adjustable focal intercept of the illuminating optical system, separate from the observation optics, in such a manner that the illuminating focal intercept is in agreement with the imaging focal intercept of the objective. Moreover, adjusting mechanism is provided for the defined adjustment of the diameter of the illuminated field. In particular, the illuminating device is suitable for a surgical microscope.

Abstract: An optical illuminator assembly for an analytical instrument, such as a clinical hematology or a flow cytometer instrument, and method of aligning the components of the illuminator assembly and orienting the illuminator assembly. The illuminator assembly includes a plurality of optical components, such as a laser source, e.g., a laser diode, optionally a spatial filter, a beam shaping aperture, and a focussing lens. The optical components are mounted in or to a housing and are internally oriented with respect to the housing to produce a focussed laser beam output. The housing is in turn mounted on an alignment mechanism which can move the focussed beam in four degrees of freedom, thereby to direct the focussed beam to a particular location. Thus, a factory alignment and a low cost prealigned optical illuminator assembly is obtained, which can be easily oriented for use in an instrument.

Abstract: The device for stereoscopic visualization according to the present invention enables an observer to see both an image from a stereomicroscope and an image from a stereoscopic fiberscope without removing his eyes from the eyepieces. The device for stereoscopic visualization may be used in surgical procedures.

Abstract: A revolver control device of this invention includes a revolver rotatably formed and having a plurality of mounting holes which contain a specified mounting hole corresponding to a specified objective and in which a plurality of objectives containing the specified objective are respectively mounted, recognition circuit for recognizing at least one of one of the plurality of objectives and one of the plurality of mounting holes which lies on an observation optical axis, driving circuit for giving the rotation driving force to the revolver to move one of the plurality of objectives onto the observation optical axis, and control circuit for controlling the driving circuit to prevent the specified objective mounted on the revolver or the specified mounting hole from being passed through the observation optical axis by rotation of the revolver when at least one of the objective and mounting hole recognized by the recognition circuit is replaced by at least one of the plurality of objectives and mounting holes whic

Abstract: A confocal microscope equipped with a light source, a rotary disk having holes, a highly sensitive image receiver or camera, an immersion lens, and a contact endpiece for contacting the skin and in which is engaged at least a lower part of the lens. The endpiece includes a central opening and abuts the skin about the central opening. The microscope allows for relative axial displacement of the contact endpiece relative to the lens.

Abstract: The invention relates to a one-hand control unit for controlling movements in optical instruments. The control unit corresponds in its configuration essentially to a computer mouse and has a mouse roller ball 2 on its lower side, an additional rotational transducer 3 at the thumb position and two or three keys (5, 6, 7) on the side of the mouse lying opposite to the rotational transducer 3. The keys (5, 6, 7) are for actuation by the middle finger, index finger and little finger, respectively. The mouse roller ball 2 and the rotational transducer 3 preferably function to drive continuously movable elements such as the illuminating field diaphragm 13, the aperture diaphragm 12, the motorized focus 20 or a motorized object stage 21. The keys (4, 5, 6, 7) are provided for driving discretely adjustable elements such as the objective-lens turret 14 or the incident-light reflector turret 15 or for switching over between coarse drive and fine drive for a motor-driven focus drive.

Abstract: An automatic focus detection device for microscopes includes an optical system for forming an image of a sample; an image sensor for photoelectrically converting an optical image derived from the optical system; a device for storing image data such that an electric signal obtained from the image sensor is converted from analog to digital form and for processing the image data to compute contrast values; a device for comparing the contrast values; a device for moving an objective lens or a stage for the sample; and a device for storing the position of the objective lens or the stage.

Abstract: An electrically driven type microscope may include an interchanging device which interchanges a plurality of objective lenses, a determination device for determining which of the lenses is disposed in an optical path of the microscope, an adjusting system of which adjustment is effected during observation of a sample, a manually settable operating system for drivingly operating the adjusting system, a data recording portion for recording plural sets of manual setting information, each set corresponding to a different objective lens and containing information indicating at least one manual setting of the operating system for the corresponding objective lens, an electrical driving system for driving the adjusting system, and a driving control circuit for controlling the electrical driving system based on information from the set of manual setting information corresponding to an objective lens determined to be in the optical path by the determination device in association with an interchange effected by the inte

Abstract: A microscope apparatus includes a light source for generating illumination light, an illumination optical system for illuminating an object to be observed with the illumination light, and an observation optical system for conducting an observation image of the illuminated object to an observation site. An objective change unit is arranged in the observation optical system for holding a plurality of objectives and for selectively inserting one of the objectives onto an optical path of the observation optical system. An optical system controller, which independently controls an optical element arranged in the illumination optical system and independently controls an optical element arranged in the observation optical system, includes a frame controller for controlling the objective change unit to insert one of the plurality of objectives selected onto the optical path of the observation optical system.

Abstract: A stereoscopic-vision endoscope having an objective optical system consisting of a front optical system having a single optical axis including a field conversion optical system, and a rear optical system including optical systems that have a plurality of optical axes. A light beam is received from the front optical system so as to form images on the optical axes, and thus form a plurality of images. The front and rear optical systems can be turned relative to each other. Thus, a magnitude of parallax permitting a sufficient sense of three-dimensionality can be provided, and the postures of images can be corrected responsively to a change in direction of view resulting from the rotation of an insertional part.

Abstract: Before the exposure of a film, the brightness of the miscroscope image is determined with a sensor by multiple constant (.tau.) which characterizes the dependence of the microscope image with time is determined. The film is subsequently exposed for a single exposure time (D.sub.c) which takes into account the dependence with time of the microscope image. The process is particularly suitable for microphotography of fluorescence pictures with fluorescence which bleaches out (fading). By the display of both the time constant (.tau.) and also the required exposure time, it can be estimated in advance, before exposure of the film, whether the dependence of the fluorescence on time permits microphotography with a sufficient exposure of the film, in the microscope conditions which have been set. A multiple exposure of the film is not required.

Abstract: A microscope includes a revolver on which are mounted at least three objective lenses having different magnifications, a driving device for revolving the revolver to switch the objective lens disposed in an optical path of the microscope, an operating device capable of giving a plurality of drive commands for disposing a desired objective lens in the optical path of the microscope to the driving device and an invalidating element for invalidating a specified drive command among the drive commands. The specified drive command serves to switch the objective lens disposed in the optical path of the microscope from a first objective lens having a minimum magnification to a second objective lens having a maximum magnification among the objective lenses.

Abstract: An optical instrument comprising a housing having an optical path and a lens turret carrying at least two different optical components. At least three supporting devices are carried by the housing and engage the outer cylindrical wall of the lens turret at circumferentially spaced positions to support the turret for rotation about the longitudinal axis of the outer cylindrical wall to position a selected optical component in the optical path. Rotation of the turret is effected by a motor with a rotatable output pulley and a flexible drive element passing around the pulley and the outer cylindrical wall of the turret. One of the optical components is a rearwardly facing mirror, and the turret has a relatively large open area to enable light to pass therethrough for reflection by a mirror on the housing to the rearwardly facing mirror.

Abstract: A modular microscope system includes a plurality of stackable housing modules each having a plurality of inwardly pointing protuberances provided with one or more precision stop surfaces thereon for removably mounting and positioning a plurality of prealigned functional element carriers having corresponding precision stop surfaces thereon for engagement with the precision stop surfaces of the housing module protuberances.

Abstract: The microscope stand foot serves to accommodate an illumination device having optical components and having an aperture diaphragm and field diaphragm. The latter are assembled in a cylindrical tube held by a carrier, the tube being able to be fastened in the stand foot as a prefabricated unit. In this way, the assembly of the illumination device is simplified. When fastening the carrier in the stand foot, the tube rests under tension on mating surfaces, as a result of which an adjustment of the tube and thus of the optical components is dispensed with.

Abstract: A universal folding condenser (1) with a support plate (4), which is fastened on the microscope and has an arm (4') angled off through 90.degree., is described. Arranged in the support plate (4) is a fixed lens (5). Above the support plate (4) there is provided a first, rectangularly shaped swivel arm (7) with a condenser head and a lens element (2) for optional introduction into the path of the illuminating beam (11). Arranged underneath the support (4) is a second, rectangularly shaped swivel arm (8) with a second lens element (3). The two swivel arms (7, 8) are forcibly coupled by means of a shifting linkage (6) in such a way that, for objectives with low magnification, the two lens elements (2, 3) are introduced into the path of the illuminating beam (11) and, for objectives with high magnification, only the condenser head is introduced into the path of the illuminating beam (11).

Abstract: In a microscope with a laser illumination, the laser beam is coupled in over the reflected light illumination beam path from the rear side of the microscope stand. The reflected light illumination reflectors are received in a slide with several switching positions. In one switching position, the slide is fitted with a fully reflecting mirror. The position of the fully reflecting mirror is monitored by sensors. The sensors are coupled to a shutter, such that the laser beam is only released when the fully reflecting mirror is inserted. The microscope is constructed as a laser scanning microscope of the inverted type. Sensors are also provided on a pivotable arm that supports a housing. The housing holds a transmitted light condensor and folding mirror above the object stage, and protects against inadvertently looking into the laser light.

Abstract: An afocal field of view and focal length converter for an optical lens system includes a cube-shaped frame that is interposed on an optical axis of the lens system. Lenses are mounted in four faces of the frame to provide two reversible afocal pairs and two faces are left empty. The frame is rotatable about a first axis to position the afocal pairs in the optical axis for one of four conversion positions, and about a second axis, perpendicular to the first axis, to rotate the empty faces in the optical axis for a no conversion position.

Abstract: A method and device for measurement of exposure times in optical devices are disclosed. Specifically, a measuring diaphragm plate and a mask plate are associated with a measurement path and a projection path of the optical device and include a plurality of corresponding measuring diaphragms and masks, respectively. A graticule having markings corresponding to the contours of the measuring diaphragms is provided in the projection path proximate the mask plate and conjugate to an intermediate image plane, and a motor for selectively positioning a measuring diaphragm on the measuring path is synchronized with a motor for positioning a corresponding mask on the projection path, such that a selected measuring diaphragm and its corresponding contour markings are simultaneously imaged at the intermediate image plane.

Abstract: A microscope having an interchangable objective revolver holding a plurality of objectives and supported on a microscope body. The direction of the revolver can be changed by rotating a rotary member through 180.degree. so that a rotation plane surface of the revolver may be inclined downwardly toward the stand side or the operator side of the microscope selectively.

Abstract: A microscope illuminating apparatus includes a light-shielding tube surrounding an objective lens, detachably mounted on a revolver of a system microscope in order to guide illumination light to irradiate an observation field, thus separating an illumination optical path and an observation optical path. An annular illuminating section serving as a light source of the illumination light is provided at a position to oppose an end portion aperture of the illumination optical path in the revolver.

Abstract: An ophthalmoscopic attachment 1 for a surgical microscope 13 accommodates an optical system 14 which erects an inter-image of the fundus (or other particular area of the vitreous body of the eye) produced by at least one ophthalmoscopic lens 8 and interchanges the optical viewing paths. The optical system 14 is located directly behind the produced inter-image at a point where the stereoscopic optical viewing paths are still intertwined. The optical system 14 is configured either as a triplet with field lenses or as a straight-view inversion prism. The attachment also includes a lens 15 that is (a) positioned between the optical system 14 and the lens end of the attachment, and (b) movable along the optical axis of the attachment to put the critical section of the eye into focus.

Abstract: A high sensitivity microscope is applicable to observe a dark specimen image or an image of a specimen unsuitable for irradiation by strong illumination light, through the use of an image intensifier capable of being inserted into a viewing optical system. The viewing optical system comprises an objective and an eyepiece, and an image intensifier may be disposed in the viewing optical system such that an acceptance plane thereof is located at an image plane of the objective and such that an optical output plane thereof is conjugate with an image plane of the eyepiece. Also, an optical path switch mechanism may be provided to guide light from the objective selectively through an optical path including the image intensifier or through an optical path not including the image intensifier. Alternatively, the image intensifier or a relay lens may be selectively inserted into the viewing optical system.

Abstract: A method of, and apparatus for, automatically focussing a microscope objective (18). The apparatus includes an image detector (26) for obtaining an image, through the microscope objective, of a surface having at least one visual feature. The apparatus further includes a processor (28) for determining, from the image, a plurality of overlapping curves, each of which represents a quality of focus for different areas of the feature. The apparatus also includes an actuator (32), controlled by the processor, for positioning the microscope objective at an optimum focus position, relative to the surface, based upon the shape, specifically the sign of the slope, of the overlapping curves.

Abstract: A turret condenser for microscopes is equipped with two turrets which are capable of interposing combinations of numerous types of optical elements on the optical axis and rotatably arranged in overlapped positions in the vicinity of the pupil of a condenser lens. Most of the optical elements are removably accommodated in each of the turrets. This turret condenser makes it possible to perform microscopy in various modes by simple operations.

Abstract: A documentation illumination module by which full illumination of a properly oriented image of a microscope's field-of-view is returned to a documenting camera or the like. The module includes a cavity with a forming and field-of-view controlling lens system, channel for returning the image, focusing and magnifying lenses in the image channel, and an iris across the image channel. Fiber optics light is transmitted through the cavity and its lens system to a microscope and its field-of-view, then returned to module and to binoculars for an observer (surgeon), without need of beam splitting optical elements. Full light is available to camera and observer. The focusing and magnifying lenses are mounted in an alternatively positionable lens system, while a zoom lens assembly can be substituted therefor.

Abstract: A microscopic preparation marker includes a tape carrying a series of self-bonding marks which in use become preferentially bonded to the preparation. The device includes a spool with a supply of the marker-carrying substrate tape and another spool that drives the tape so that the tape leaves on the surface of the cover slide of the preparation, surrounding an area of interest that is to be later examined in more detail, a new mark each time the substrate tape is advanced and pressed against the cover glass. The device can be applied in scientific fields that use optical microscopes.

Abstract: A split-image, multi-power microscopic image display system and method wherein the image of an object positioned on a slide is split into two optical paths, and is magnified to a varying degree in each optical path, the resulting respective magnifications being displayed on respective monitor devices. The initial optical path includes an objective and a splitter; the path of lower magnification includes a converging lens, diverging lens, reduction lens, bending prism, TV camera and TV monitor; the path of higher magnification includes a trinocular microscope head, TV camera, and TV monitor.

Abstract: A split-image, multi-power microscopic image display system and method wherein the image of an object positioned on a slide is split into two optical paths, and is magnified to a varying degree in each optical path, the resulting respectively magnified images being displayed on respective monitor devices. The initial optical path includes an objective and a splitter; the paths of lower magnification and higher magnification each include a TV camera and a TV monitor, and may include various optical elements in accordance with the four disclosed embodiments.