GB2379280A

GB2379280A - Stereoscopic microscope with re-imaging means and a mask

Info

Publication number: GB2379280A
Application number: GB0203226A
Authority: GB
Inventors: John Sharpe Ward
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-09-01
Filing date: 2002-02-12
Publication date: 2003-03-05
Also published as: GB0203226D0; GB0121243D0; AU2002321599A1

Abstract

A stereoscopic binocular microscope comprises an objective system for producing an enlarged real primary image of an object and a beam splitter (18) for directing pencils of light from the objective into each one of a pair of left and right optical subsystems for binocular viewing of the primary images. Each subsystem comprises re-imaging means (44) for forming a second primary image (52) from the first primary image (32) and enlarging means (50) for producing, as a secondary image, an enlarged virtual image of a said second primary image. Located in or near an aperture conjugate plane (34) between the beam splitter and the secondary virtual image producing means is a mask (60) for occluding a left or right lateral portion of the aperture disk (70). Also provided are a pair of left and right stereoscopic conversion elements, for a binocular microscope comprising the aforementioned optical subsystems and masks.

Description

STEREOSCOPIC MICROSCOPE This invention relates to a binocular stereoscopic microscope of the kind in which pencils of light from a single objective are directed to one each of a pair of eyepieces.

It is to be understood that although much of the following description refers to such vision-related terms as viewing, ocular, and eyepiece, these are not intended to apply only to real time viewing by a human observer, but on the contrary are intended to include equivalent structures for photographic and other image transmitting and processing and recording means whereby a pair of images can be transmitted or processed, or recorded for later transmission, processing or viewing, as a stereo pair.

The invention uses an optical system in which the respective left and right eyepieces are provided with light pencils originating, with or without overlap, from towards the opposite left and right sides of the objective, thereby giving the observer an apparent viewpoint from the position of the objective with a correspondingly short, but real, interpupillary separation, giving rise to parallax, perspective and stereoscopy. Various devices for this purpose have been known since the design of Riddell in 1852. All fail to a greater or lesser extent to combine ease and comfort of use with all the diverse optical characteristics required of a satisfactory general-purpose system.

It is an object of the invention to provide a microscope system of this general kind capable of a good variety of desirable characteristics, such as a high resolution three dimensional image, of controllable perspective, free of appreciable vignetting, with a high and unobstructed eyepoint, and compatible with a full range of lighting and contrast techniques. It is a further object to provide means for readily converting certain types of known binocular compound microscopes to benefit from the invention.

In accordance with the invention, in a stereoscopic binocular microscope having an objective and a pair of left and right optical

subsystems for binocular viewing of first real primary images of an object, there are provided re-imaging means to form in each subsystem second real primary images viewable through further enlarging imaging means; the re-imaging means providing for each subsystem an aperture plane conjugate with the objective aperture, and including mask means for occluding a respective left or right lateral portion of the aperture disk in or near said aperture conjugate plane whereby to achieve stereoscopic (including pseudoscopic) imaging.

In one aspect the invention comprises a stereoscopic binocular microscope, comprising an optical system including an objective system for producing an enlarged first real primary image of an

object ; a beam splitter for directing pencils of light from the kij L-, irec-cing penciis o objective into each one of a pair of left and right optical subsystems for binocular viewing of a pair of said primary images ; re-imaging means for forming in each subsystem a second real primary image from the first primary image; and enlarging means in each subsystem for producing, as a secondary image, an enlarged virtual image of a said second real primary image; wherein an exposed aperture conjugate plane is formed in each subsystem between the first and second primary images, and each said plane is available for respective left and right mask means provided in or near said plane to occlude a respective left or right lateral portion of the aperture disk.

The respective left and right mask means provided in or near said plane are advantageously adjustable across the respective aperture conjugate planes, and preferably are each independently adjustable across the corresponding plane.

The term'virtual image'which is applied to the secondary image is a customary usage. The secondary image producing means (for example an ocular lens) in normal adjustment may by itself produce no real image at all, hence the term virtual, a real image then only being formed on the retina of an observer's eye looking through the secondary image producing means.

The mask means are most preferably provided in both the left and the right subsystem and are desirably arranged to mask the light substantially equally, but on the opposite left or right side as the case may be. The specific embodiments disclosed and described herein are symmetrical between left and right. However, the skilled man will recognise that masking only one side will still produce a stereoscopic effect, albeit with less separation between the left and right viewpoints, and such arrangements or other asymmetrical arrangements are within the ambit of the invention.

The mask means desirably include provision for unmasking the light path through the microscope whereby to convert the microscope to plane two dimensional viewing.

In a further aspect the invention provides a pair of left and right stereoscopic conversion elements for a binocular microscope with an optical system that includes an objective for producing an enlarged first real primary image of an object, and a beam splitter for directing pencils of light from the objective into each one of a pair of left and right optical subsystems for binocular viewing of a pair of said primary images, wherein each subsystem comprises reimaging means for forming a second real primary image from the first primary image, and enlarging means for producing, as a secondary image, an enlarged virtual image of said second real primary image ; which conversion elements each provide a supplement to each respective subsystem, at least one such supplement including mask means located in or near an aperture conjugate plane between the first and second primary images for occluding a respective left or right lateral portion of the aperture disk before the formation of the secondary image.

The supplements may include both the re-imaging means and the secondary virtual image producing means so that they replace original eyepieces completely; or the supplements may include the re-imaging means and use original eyepieces as secondary virtual image producing means ; or the supplements may include secondary virtual image producing means and use original eyepieces as reimaging means. The supplements may be in two or more pieces ; for

example, they may include devices such as spacer tubes to alter the spatial relation between an original eyepiece and the first primary image. other particular features of the invention are set out in the following description and in the appended claims.

It should be noted that optical systems using reflecting elements (mirror surfaces) as well as refracting elements (lenses, and in some cases prisms) may be used in the invention. Thus, the objective may comprise a reflecting element. The optical elements used in the invention may in general be simple or compound elements or combinations or assemblies of the same.

Embodiments of the invention are illustrated, by way of example only, in the accompanying drawings, in which: Figure 1 is an optical ray diagram of a conventional compound binocular microscope; Figure 2 is a component and optical ray diagram showing the changed elements of a similar microscope modified in accordance with the invention by supplements to the left and right optical subsystems ; Figure 3 is a component and optical ray diagram of the left and right optical subsystems of a second embodiment of the invention; Figures 4 and 5 are component diagrams of further embodiments of the invention, similar to the views shown in Figures 2 and 3 but omitting the ray paths, illustrating the use of additional optical elements ; Figures 6 to 9 are component diagrams of further embodiments of the invention, similar to the views shown in Figures 4 and 5, illustrating various supplements for converting plane viewing binocular microscope systems to stereoscopic viewing in accordance with the invention;

Figure 10 is a component and optical ray diagram of a further embodiment of the invention ; Figure 11 is a cross-sectional view illustrating how a conversion element or supplement may be constructed for attachment in place of an original microscope eyepiece; Figure 12 is an exploded view of the same; Figure 13 is an external view corresponding to Figure 11 ; and Figures 14a to 14g illustrate the forms of seven different masking means.

In the drawings, particularly Figures 1 to 10, the markings o----o are used to denote aperture conjugate planes, and the markings x----x are used to denote field conjugate planes.

As shown in Figure 1, a conventional binocular compound microscope without stereoscopic imaging has an overall optical system which includes an objective lens assembly 12 above a plane 14 in which an object to be viewed is supported on the microscope stage. Light for illuminating the object is provided from below plane 14 by condenser lens system 16. The source of light is not shown.

Pencils of light rays from the objective are directed to a prismatic beam-splitter 18 where the light is divided with substantially equal intensity into a pair of left and right binocular optical sub-systems 20L, 20R. Each sub-system includes an eyepiece 22 containing an ocular lens 26. A field lens may be included at or near position 24.

The optical system of the microscope may include a tube length determining lens at 25 or elsewhere for infinity corrected or other systems. Lens 25 is part of the objective system in that it cooperates with objective lens assembly 12 to form a real primary image of the object. Other vergent elements (convergent or divergent) such as magnification changers may be present.

The object may be a specimen illuminated by transmitted light which, passing through the object, is directed by the objective 12 through objective aperture conjugate plane 30, passes through the beam-splitter 18, and comes to a focus in each eyepiece to form a real primary image in the field conjugate plane 32. The left and right ocular lenses 26 then enable the observer to see enlarged virtual secondary images with the observer's eye ideally placed at the Ramsden disc or ocular aperture conjugate plane 34 of each eyepiece.

Many other designs of binocular compound microscope are, of course, known, but the kind illustrated in Figure 1, with its Jentzsch binocular prisms 18 and its positive eyepieces 22, will serve as a

conven4en-1--exar,-, Pl e. convenient example. A typical alternative beam splitter is the Siedentopf prism arrangement. Other equivalent devices will be known to the skilled man. The general requirement is to divide an incoming beam or pencil of rays of a given intensity and crosssectional area into the two outgoing beams or pencils, usually of respective areas substantially equal to one another and to the incoming area, and usually of substantially equal intensity as near as possible to half the incoming light intensity. The usual means comprise a part reflecting, part transmitting, interface.

The presence of one or more additional access points to the light path by means for instance of further beamsplitters provided for camera attachments, or for other purposes, does not in general interfere in any way with the operation of the device. Thus the binocular may form part of a trinocular, or of a multiple port photomicroscope, or of a microscope equipped with other binocular heads.

It should also be noted that the invention is beneficial in microscopes in which the specimen is illuminated by reflected light, since the stereoscopic imaging of surface features can then be particularly well seen. Although so-called epi illuminated microscopes have different optics for the lighting of the specimen as compared with transmitted light models, there is no practical

difference in the application of the present invention to the viewing optics.

The microscope of Figure 1 can be modified in accordance with the invention in the respective left and right optical sub-systems after beam splitter 18, as shown in Figure 2. Elements before the beam-splitter are unchanged.

Looked at simply, supplementary portions 40L, 40R are added to the original eyepieces 22L, 22R. The optical elements constituted by lenses 26 bring together the ray cones from the first primary images in the field conjugate planes 32 into a ray bundle 42. Lens 26 is operating as a first component of a composite relay lens system, and with substantially unequal conjugate foci, in which the object side conjugate focus is close, and the image side conjugate focus is distant. The beam 42 is received by lens 44, acting as the second component of the relay lens system, and which is also operating with unequal conjugate foci. In this case, the object side conjugate focus is distant and the image side conjugate focus is close. Acting together, elements 26 and 44 project or re-image the first primary images as second relayed primary images a few centimetres distant. By placing the first primary images in or near the first focal planes of the elements 26, the second primary images are formed in or near the second focal planes of the elements 44. Optical element 44 should be so placed that its entrance pupil and angular aperture include as much as is desired, and generally substantially all of, the exit pupil of element 26 and the beam of light transmitted through it.

The left and right optical subsystem supplements 40 each include a new ocular 50 which corresponds in function with the former ocular 26. Each second relayed primary image is formed in the respective field conjugate plane 52, and ocular 50 is so placed that its first focal plane lies coincident with, or near, field conjugate plane 52.

As thus far described, the left and right subsystems reduplicate the original eyepiece functions, but allow one great advantage.

The observer can place his eyes at the ideal viewing position, at the aperture conjugate plane or Ramsden disc 51 of each ocular 50, while an optically equivalent location, the aperture conjugate plane 34 of each optical element 26, is available for masking; notionally, the masks and the observer's eyes can simultaneously occupy the same virtual space in the optical train.

In each subsystem 40, above optical element 26 and approximately in its second focal plane, is located an image of the objective aperture. This image constitutes an additional or intermediate aperture conjugate plane. Mask means 60 are placed in or adjacent each of these intermediate aperture conjugate planes and adjusted so as to cut off part of the illuminated disc of the aperture. The further out of this plane that the mask means are located, the less precise will they be in selectively masking light from one side or the other of the aperture disc. In a conventional plane viewing compound light microscope the optical correction of the image of the objective aperture in an upper aperture conjugate plane is largely without significance. If, however, masking is to be performed in such a plane, then the presence of aberrations such as longitudinal chromatic aberration may make it difficult to obtain a relayed field conjugate image free from shading or colour casts graded in the X axis. The more completely that light passing through the objective aperture (rear equivalent plane) is brought to a focus in the intermediate aperture conjugate plane, then the more complete will be the control of vignetting which may be obtained by Z axis adjustment of the mask means.

When in use the masks of the two eyepieces are so arranged, with respect to one another and to the microscope axis, as to mask off an outboard or abaxial portion of the illuminated aperture discs in the intermediate aperture conjugate plane (hereinafter also'ACP').

The appearances of these respective masked disks are illustrated at 70L, 70R.

Because of the inverting action of the optical elements 44 and 50 the Ramsden discs at the observer's eyepoint 51 will therefore have the inboard or adaxial parts of the apertures masked off,

illustrated at 72L, 72R. Such masking gives a parallactic difference between left and right eyepoints in the correct sense for normal stereoscopic, rather than pseudoscopic, vision. If the outboard or abaxial parts of the apertures are masked off, pseudoscopic vision will result.

Masking is adjustable in the X axis (the interoptic axis) to suit the numerical aperture (NA) of the objective in use. Half of the aperture may be masked for objectives of NA 0.35 or less. Masking may be progressively reduced (as shown in Figures 13a to 13c), for example, when using objectives of higher NA; this conserves resolution in the X axis and maintains a moderate perspective angle, avoiding hyperstereoscopism.

The location of mask means 60 is adjustable (but could be pre-set) in the Z axis (the main or longitudinal optical axis of the microscope) for coincidence with the image of the objective aperture in the intermediate ACP. This is to control vignetting.

Each optical element 50 acts as a conventional microscope eyepiece allowing the observer to see a magnified virtual image of the second, relayed, primary image. When both eyepieces are used simultaneously, stereoscopic perception of the single, fused, magnified image arises from the parallax differences between the respective left and right relayed primary images imparted by masking.

Figure 3 shows an embodiment of the invention that differs from the embodiment of Figure 2 in the location of convergent optical elements within the two optical subsystems. Relay lens 27 is located with its first or lower focal plane above the plane of the first primary image 32 so that it is operating with similar or equal object and image conjugate foci. It thus projects the second relayed primary image a short distance above itself in field conjugate plane 52. Such a working position allows lens 27 in Figure 3 to perform the combined functions of lenses 26 and 44 of the composite relay lens system shown in Figure 2. Ocular lens 50 functions in the same way in each of these embodiments.

The embodiments of Figures 2 and 3 achieve similar ends with three and two lenses respectively in their binocular optical subsystems.

Both can be elaborated with additional convergent elements.

Figures 4 and 5 are examples. Figure 4 is the three lens type of Figure 2, with the addition of field lenses 62 and 64 below the field conjugate planes 32 and 52, either to alter the extent of the field of view, or for general purpose optical correction of the image, or for both these purposes. Likewise, Figure 5 is the two lenses type of Figure 3, with the addition of field lenses 66 and 68 for similar purposes.

In Figure 5, increasing the powers of field lenses 68L and 68R (decreasing their focal lengths) and lowering their positions would cause the system to operate more like a three lens embodiment. The number and location of optical elements used to perform the invention may accordingly be varied, but in all cases re-imaging means are provided such that each left and right optical subsystem includes a relayed primary image and an additional aperture conjugate plane where mask means may be located, and means for producing a virtual secondary image for magnified viewing of the relayed primary image.

In Figures 2 to 5 the supplements include both the re-imaging means and the secondary virtual image producing means so that they replace original eyepieces completely. Figures 6 to 9 illustrate some further supplement configurations, using the same reference numbers as in Figures 2 to 5 where appropriate. It should be understood that the same numbers refer to components with the same functionality, not necessarily being identical. In Figures 6 supplement 76 includes re-imaging means 26 and 44 and uses original eyepieces 22 as secondary virtual image producing means. In Figure 7 supplement 77 includes virtual image producing means 50 and reimaging means 44 and uses original eyepieces 22 as re-imaging means. In Figure 8 supplement 78 includes re-imaging means 27 and uses original eyepieces 22 as secondary virtual image producing means. In Figure 9 supplement 79 includes secondary virtual image producing means 50 and uses original eyepieces 22 as re-imaging means. Figure 9 shows the supplement 79 in two pieces 79a and 79b,

where 79b signifies means such as spacer tubes which alter the distance between original eyepiece 22 and the first primary image at 32.

All embodiments of the invention described above use paired reimaging optics located above the beam splitter in each of the binocular subsystems. These re-imaging optics relay the primary images to form second primary images. Also, each provides an additional ACP in which mask means may be provided to give left or right parallax displacement to each said second primary image, which second primary images are viewed through secondary enlarging virtual image producing means. By using paired re-imaging optics with one item or set in each binocular subsystem the invention may be performed for instance with certain beam-splitting binocular prism arrangements of established design such as Jentzsch or Siedentopf.

The invention can also be performed with binocular beam splitting means of different designs in such a way that some paired optical elements, for instance relay elements on each side together with any associated optics such as field lenses, can be removed and replaced with an unpaired element or elements located below the beam-splitter.

Figure 10 for example shows a design similar to that of Figure 3 but with the paired relay elements 27 combined as one element 28 in the common light path. In this case all the primary image relay optics are located before the beam splitter since they consist of a single element, group or assembly.

Parameters of the relay element including focal length, position of rear principal (or equivalent) plane, and its aperture, both angular and in diameter, need to be matched to the relevant parameters of the beam-splitting means employed to ensure that the intermediate ACP is formed external to it, so as to be accessible for masking over a range, if required, of Z axis adjustment.

The additional tube lens 29 shown in this embodiment may desirably be included at some point in the common light path between the objective and the first primary image to assist in the formation and location of the first primary images and in the general achievement of a compact and convenient instrument.

The figure shows an embodiment of the invention with a finite tube length objective on a compound light microscope of unitary or integral design. The invention may also be implemented with certain compound light microscopes of modular design or having infinity corrected objectives or both.

The arrangements just described use unpaired re-imaging optics but

4-T in such a way as to reproduce the essential operating features of the invention.

Thus an intermediate aperture conjugate plane is provided for each of the left and right binocular subsystems.

The image of the objective aperture in each of these intermediate aperture conjugate planes is an image of substantially the whole aperture and is undivided though it may be reduced in overall size as compared with the objective aperture itself.

Mask means may be located in or near both left and right intermediate aperture conjugate planes and may be adjustable (or preset) in the X and Z axes.

Masking can therefore be used to give parallax displacements to both the left and right relayed, second primary images which may be viewed by an observer through further enlarging imaging means which produce, as secondary images, enlarged virtual images of said left and right second primary images.

Provided these features are reproduced, the formation of the left and right second primary images and their associated intermediate aperture conjugate planes may be performed with vergent optical elements located before the beamsplitter or after it or both.

Figures 11,12 and 13 illustrate a particular device constructed according to the foregoing principles, which is described below, by way of example only. This example is that of the three lens type and corresponds to Figure 2 with the addition of the field lenses 62 of Figure 4 (but not the field lenses 64).

A microscope eyepiece 122 of low power Huyghenian form has a field lens 124 and an ocular 126. These elements 124 and 126 may be chromatically matched to the objective employed, whether correction free, compensating as used here, or ordinary.

A collar 80 is fitted at the ocular end of eyepiece 122 and extends from below the rim of the ocular mount 128 a short way down the body of the eyepiece.

The collar 80 is of such a length as to hold the eyepiece 122 in the microscope's binocular body tubes such that a first primary image formed at the correct mechanical tube length for the objective system being used will lie in or near the first or lower focal plane of lens 126. The upper part of the collar 80 is externally screw-threaded at 80'. Fitting on to the collar by a matching female thread 82'is the lower end of a short cylinder 82.

This thread is of an internal diameter greater than the diameter of the ocular mount 128, allowing cylinder 82 to be fitted over the mount.

Just above the lower threaded part of cylinder 82 its wall is broached by two flat slots 84 placed diametrically opposite one another. Located in the slots is a guide 86. Cylinder 82 is made in two parts (82a, 82b) in this example to facilitate the placement of guide 86.

Thus when a long flat masking strip 90 of metal or other suitable material is placed in the guide 86, the strip lies across the centre of the cylinder with its length at right angles to the long axis of the cylinder and its width lying flat in a (notional) transverse section of the cylinder.

The strip 90 is pierced by a central aperture 92 which may be of square, rectangular or other form. When the cylinder 82 is screwed onto the threaded collar 80 then the intermediate ACP above optical element 126 is covered by strip 90. The strip is moved along in the guide 86 (X axis adjustment) until the desired part of the intermediate ACP is exposed in aperture 92. The remainder is masked by the strip 90.

The axial distance between optical element 126 and aperture 92 can be varied by means of thread 80', 82' (Z axis adjustment) so that aperture 92 and the intermediate ACP can both be brought into the same plane.

The Z axis adjustment may in some cases be pre-set, for instance for the highest power objective in a set, and used at that adjustment with all other (lower) power objectives.

The upper end 82a of cylinder 82 is threaded internally (or otherwise adapted) to receive an externally threaded supplementary extension tube 140. This tube is threaded internally (or otherwise adapted) at its lower end to retain a relay lens, optical element 144. This is also a converging element and is of sufficient aperture to avoid cut-off of the image area. Its spherical correction should be for unequal conjugate foci, object side distant. As an example, an ocular lens may be used in a reversed orientation, plane side down.

The top end of supplementary extension tube 140 holds optical element 146 which is of the general form of a microscope eyepiece ; a x16 positive eyepiece is used here. Tube 140 is of sufficient length to hold optical element 146 with its field diaphragm in or near the second focal plane of optical element 144.

The assemblies as described above in relation to Figures 11 to 13 are taken and put in place of the eyepieces of a binocular compound microscope, to convert it to stereoscopic viewing in accordance with the invention. To give stereoscopic perspective they are

oriented with respect to one another and to the microscope so that the masks operate as shown in Figures 2,3 and 14a to 14g.

Illustrations 72 in Figures 2 and 3 are plan views of the Ramsden discs 51 (or ocular aperture conjugate planes) as seen from above, and illustrations 70 are the same views but of the masked intermediate aperture conjugate planes 34. Various shapes of mask that can be used to shade parts of the aperture conjugate plane are shown in Figures 14a to 14g, as seen at the Ramsden discs 72. The actual shapes of the edges of the apertures 92 located at the intermediate ACP in each system will be their laterally inverted counterparts; that is to say, they will be the mirror images thereof.

For use with objectives of aperture about NA 0.35 or less, the device works well with half aperture straight edged (chordal) masking. Figure 14a shows this in Ramsden discs 72a.

Figures 14b and 14c show lesser chordal masking 72b and 72c for medium and high power use respectively. Reduced masking is very suitable for use with the invention.

A straight edge may be pre-set for example on a selecting device such as a disc or slider (eg slide 90), or it may be continuously adjustable. The setting is made to obtain the perspective or parallax angle required, from the NA of the objective in use.

The chordal mask offers a wide amount of control of the stereo image and is of a good general purpose geometry. However, it has its own particular characteristics including: 1) The straight edge obscures the central and peripheral areas of the aperture in a particular ratio, and this ratio changes as the mask setting is changed. Maskings 72c obscure a higher proportion of periphery than do 72a. If the aperture is not evenly illuminated then other mask geometries that differ in this respect may be useful.

2) Straight edged masking causes characteristic patterns of resolution loss which are directional, depending on azimuth.

Resolution is thus anisotropic. Other mask geometries have different effects on resolution, including some which are isotropic for resolution with respect to azimuth.

Figure 14d shows a pair of convex arcuately masked Ramsden discs 72d which are slightly more anisotropic for resolution than maskings 72c, but which will produce stereo parallax with less masking of the periphery. Techniques giving an aperture conjugate plane with a strongly lit central area and a weakly lit periphery may benefit from such a mask profile. High NA lenses when used translit with a stopped down condenser are a particular but widely used technique of this sort.

Figure 14e shows sector maskings 72e which give a similar approach to producing stereo parallax from medium and high powered phase contrast objectives with a minimum effect on the weaker diffracted rays.

Figure 14f shows arcuate concave or crescentic maskings 72f which are less anisotropic than the straight edge. This may have advantages of reliability of recognition: structures look more the same in whatever azimuth they lie. Masking of this type is more suited to techniques giving an aperture conjugate plane with a weakly lit central area and a strongly lit peripheral area such as dark ground epi-or trans-illumination. It is also suitable for use with techniques giving an evenly illuminated ACP.

Figure 14g shows 3600 arcuate maskings 72g to give stereo parallax with large aperture lenses which is entirely isotropic for resolution against azimuth. A structure will have exactly the same appearance in whatever azimuth it lies, subject to any constraints imposed by lighting or other variables. It is applicable as in Figure 14f; the entirely isotropic operation may offer advantages in working with any automated functions of the instrument.

It is desirable that the mask means 60 (masking strips 90 with apertures 92 in Figures 11 to 13) should be removable from the light path altogether, and replaceable therein, to permit simple conversion between stereoscopic and conventional non-stereoscopic binocular use. For this purpose, the aperture 92 in mask strip 90 may be larger than the light path, so that it can be positioned fully across the intermediate aperture conjugate plane, or the strip 90 may be removable from the guide 86, or the guide 86 may itself be removable and replaceable. Replaceable masks are in any event desirable in order to allow choice between the different masks illustrated in Figure 14.

Claims

CLAIMS 1 A stereoscopic binocular microscope having an objective and a pair of left and right optical subsystems for binocular viewing of first real primary images of an object, comprising re-imaging means to form in each subsystem second real primary images viewable through further enlarging imaging means ; the re-imaging means providing for each subsystem an aperture plane conjugate with the objective aperture, and including mask means for occluding a respective left or right lateral portion of the aperture disk in or near said aperture conjugate plane whereby to achieve stereoscopic imaging.
2 7% s-ereoscop4 c binocular pt Cal 2 A stereoscopic binocular microscope, comprising an optical system including an objective system for producing an enlarged first real primary image of an object ; a beam splitter for directing pencils of light from the objective into each one of a pair of left and right optical subsystems for binocular viewing of a pair of said primary images; re-imaging means for forming in each subsystem a second real primary image from the first primary image; and enlarging means in each subsystem for producing, as a secondary image, an enlarged virtual image of a said second real primary image; wherein an exposed aperture conjugate plane is formed in each subsystem between the first and second primary images, and each said plane is available for respective left and right mask means provided in or near said plane to occlude a respective left or right lateral portion of the aperture disk.
3 A microscope according to claim 2 wherein the respective left and right mask means provided in or near said plane are adjustable across the respective aperture conjugate planes.
4 A microscope according to claim 2 wherein the respective left and right mask means provided in or near said plane are each independently adjustable across the corresponding plane.
5 A microscope according to any one of claims 2 to 4 wherein all primary images are formed behind the beam splitter.

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6 A microscope according to any one of the preceding claims wherein the said enlarging means comprise an ocular lens.
7 A microscope according to any one of the preceding claims wherein each subsystem comprises a relay lens in the re-imaging means and an ocular lens in the enlarging means.
8 A microscope according to claim 7 wherein the relay lens is a composite relay lens system including a first component adapted to form the said aperture conjugate plane within the subsystem and a second component located behind the mask means.
9 A microscope according to claim 8 wherein the said first component of the relay lens system is operative with substantially unequal conjugate foci, the object side conjugate being close, the image side conjugate being distant, and the said second component is operative with substantially unequal conjugate foci, the object side conjugate being distant, the image side conjugate being close.
10 A microscope according to claim 7 wherein the relay lens is wholly located before the mask means and itself forms the said aperture conjugate plane and the second primary image.
11 A microscope according to any one of the preceding claims wherein the first real primary image is projected by a field lens.
12 A microscope according to any one of the preceding claims wherein the second real primary image is projected by a field lens.
13 A microscope according to any one of the preceding claims wherein the said mask means are located in both optical subsystems.
14 A microscope according to claim 13 wherein the mask means in the pair of optical subsystems occlude respective left and right portions of the aperture discs whereby to achieve normal stereoscopic imaging of the object.

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15 A microscope according to claim 13 wherein the mask means in the pair of optical subsystems occlude respective left and right portions of the aperture discs whereby to achieve pseudoscopic imaging of the object.
16 A microscope according to any one of the preceding claims wherein the mask means include provision for unmasking the light path through the microscope whereby to convert the microscope to plane two dimensional viewing.
17 A microscope according to any one of claims 13 to 16 wherein the mask means occlude the respective aperture disks in the pair of optical subsystems chordally.
18 A microscope according to any one of claims 13 to 16 wherein the mask means occlude sectors of the respective aperture disks in the pair of optical subsystems.
19 A microscope according to any one of claims 13 to 16 wherein the mask means occlude the respective aperture disks in the pair of optical subsystems as convex arcs.
20 A microscope according to any one of claims 13 to 16 wherein the mask means occlude the respective aperture disks in the pair of optical subsystems as concave arcs.
21 A microscope according to any one of the preceding claims wherein the mask means are adjustable in the X axis of the field of view.
22 A microscope according to any one of the preceding claims wherein the mask means are adjustable in the Z axis of the field of view.
23 A pair of left and right stereoscopic conversion elements for a binocular microscope with an optical system that includes an objective system for producing an enlarged first real primary image of an object, and a beam splitter for directing pencils of light

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from the objective into each one of a pair of left and right optical subsystems for binocular viewing of a pair of said primary images, wherein each subsystem comprises re-imaging means for forming a second real primary image from the first primary image, and enlarging means for producing, as a secondary image, an enlarged virtual image of said second real primary image ; which conversion elements each provide a supplement to each respective subsystem, at least one such supplement including mask means located in or near an aperture conjugate plane between the first and second primary images for occluding a left or right lateral portion of the aperture disk before the formation of the secondary image.
24 A pair of left and right stereoscopic conversion elements according to claim 23 adapted so that all primary images are formed within the conversion elements.
25 A pair of left and right stereoscopic conversion elements according to claim 23 or 24 in each of which the enlarging means comprises an ocular lens.
26 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 25 wherein each subsystem comprises a relay lens in the re-imaging means and an ocular lens in the enlarging means.
27 A pair of left and right stereoscopic conversion elements according to claim 26 in each of which the relay lens is a composite relay lens system including a first component adapted to form the said aperture conjugate plane within the subsystem and a second component located behind the mask means.
28 A pair of left and right stereoscopic conversion elements according to claim 27 in each of which the said first component of the relay lens system is operative with substantially unequal conjugate foci, the object side conjugate being close, the image side conjugate being distant, and the said second component is

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operative with substantially unequal conjugate foci, the object side conjugate being distant, the image side conjugate being close.
29 A pair of left and right stereoscopic conversion elements according to claim 26 in each of which the relay lens is wholly located before the mask means and itself forms the said aperture conjugate plane and the second primary image.
30 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 29 in each of which the first real primary image is projected by a field lens.
31 A pair of left and right stereoscopic conversion elements

according to any one of claims 23 to 30 in each of which the seconS u I -L-L u 11 li 11 ll real primary image is projected by a field lens.
32 A pair of left and right stereoscopic conversion elements according to any one of the preceding claims wherein the said mask means are located in each conversion element.
33 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 32 wherein the mask means in the pair of optical subsystems occlude respective left and right portions of the aperture disks whereby to achieve normal stereoscopic imaging of the object.
34 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 32 wherein the mask means in the pair of optical subsystems occlude respective left and right portions of the aperture disks whereby to achieve pseudoscopic imaging of the object.
35 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 34 wherein the mask means include provision for unmasking the light path whereby to convert the microscope to plane two dimensional viewing.

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36 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 35 wherein the mask means occlude the respective aperture disks in the pair of optical subsystems chordally.
37 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 35 wherein the mask means occlude sectors of the respective aperture disks in the pair of optical subsystems.
38 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 35 wherein the mask means occlude the respective aperture disks in the pair of optical subsystems as convex arcs.
39 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 35 wherein the mask means occlude the respective aperture disks in the pair of optical subsystems as concave arcs.
40 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 39 wherein the mask means are adjustable in the X axis of the field of view.
41 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 40 wherein the mask means are adjustable in the Z axis of the field of view.
42 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 41 wherein the supplements include both the re-imaging means and the secondary virtual image producing means and are thereby adapted to replace eyepieces of the unconverted microscope.
43 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 41 wherein the supplements include the re-imaging means and are adapted to use eyepieces from

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the unconverted microscope as secondary virtual image producing means.
44 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 41 wherein the supplements include secondary virtual image producing means and are adapted to use eyepieces from the unconverted microscope as re-imaging means.
45 A pair of left and right stereoscopic conversion elements according to any one of claims 23 to 44 wherein the supplements include spacer tubes.
46 A stereoscopic binocular microscope substantially as herein

described ith reference to and as illustrated in any of the accompanying drawings.
47 A pair of left and right stereoscopic conversion elements for a binocular microscope substantially as herein described with reference to and as illustrated in any of the accompanying drawings.