WO1991002278A1

WO1991002278A1 - Stereo viewer

Info

Publication number: WO1991002278A1
Application number: PCT/GB1990/001178
Authority: WO
Inventors: Godfrey Michael Cohen
Original assignee: Godfrey Michael Cohen
Priority date: 1989-08-01
Filing date: 1990-07-30
Publication date: 1991-02-21
Also published as: GB8917611D0

Abstract

A stereo viewer with a prism block (2), and a lens system (8) spaced from and thus separate to the prism block and through which a stereo image is viewed. Guide mounts for replaceable slide transparencies (a, b) of a stereo pair can be included, and the pictures can be illuminated by a light source (5) internal of a housing (3) locating the prism block. In alternative embodiments, pictures form connected television cameras or slide projectors can be viewed.

Description

STEREO VIEWER

This invention relates to a stereo viewer.

A stereo viewer is an instrument designed to provide from two-dimensional pictures emulation of normal sight in three-dimensions. Each eye of a person receives its own light from a respective one of a stereo subject pair; two slightly different images of the subject are relayed to the brain, which then fuses them together to create an image with depth and clarity of detail, compared to the subject image through one eye only or from a single two-dimensional picture.

The available personal stereo viewers (stereoscopes) are binocular instruments used for viewing pairs of drawings or photographs made from laterally displaced centres of perspective (stereo pairs). For still-life scenes or architectural subjects, suitable photographic stereo pairs may be obtained by successive exposures from laterally displaced positions of a standard camera; otherwise there is required a stereo-camera, or a pair of cameras that record the two views simultaneously. The stereo pair may be photographic transparencies (diapositives) viewed by light transmitted through the transparency, or opaque pictures or photographic prints viewed by reflected light.

A disadvantage of a binocular instrument is that the binocular eyepiece must be held up to, and close to, the eyes in order to ensure that each eye sees only its respective left and right picture view. A related disadvantage is that many people require adjustable eyepieces, particularly those who normally wear glasses; nevertheless it has been estimated that about 20% of the population are still unable to obtain the stereo effect.

Binocular instruments utilizing diapositive slide film are capable of good results for many individuals, particularly those with interpupillary separations of from 6cm to 7cm. A typical instrument will have a fixed interocular distance equal to the picture separation i.e to the separation between common infinity points on the stereo pair; to limit aberration when viewing adjacent the lens edges, the lenses will be both large and of good quality. _. There are however individuals having unusual interpupillary separations, of perhaps 5cm or 8cm; they may need to use a different stereoscope configuration, wherein both the interocular and picture separation are adjustable, such that the interocular .separation corresponds to the interpupillary separation of the user; a particular correlation may need to exist between each lens axis and its respective picture to ensure that the picture separation is slightly less than the interocular separation, rather than the reverse, so that an element of convergence will be possible, as may be necessary, in order that stereoscopic fusion of the stereo pair may occur, with the result providing comfortable viewing. t Another disadvantage of the binocular stereoscope is its inability to compensate if one of the elements of a stereo pair is inaccurately mounted in relation to the other. Thus if a salient point on one picture is not in vertical synchronization with the other, not only will an unrealistic image be produced, but there will probably be significant viewing discomfort if the user persists .

It is known that individual diapositives (slide transparencies) can be viewed in a personal hand held mono "slide" viewer, and one of my embodiments is designed to be of a size and configuration to utilise the existing housing of a hand held mono-viewer and some of its parts. The observer views an enlarged image using one or more concentrically arranged magnifying lenses. So that viewing can be independent of external lighting conditions, the picture can be illuminated by a dedicated lamp inside the viewer housing, energised from a mains electrical supply using a transformer, or from a battery.

With particular embodiments of my invention, I seek to provide a stereo viewer with the handling, viewing comfort and convenience advantages associated with a conventional "hand held" slide viewer, but which will accommodate the interpupillary separation requirements of individual observers, as well as a stereo viewer that will tolerate and compensate for some stereo mounting error. The three-dimensional image will be viewed as one would view a single slide within the known "two-dimensional" viewer, but without the need to hold the viewer close to the eyes to obtain an effective stereo reconstruction.

I am aware of a previous attempt at stereo presentation which did not involve the use of a binocular eyepiece, namely that disclosed in Swan GB Patent 324*5 of 4th December, 1862. The present invention and Swan both utilize a pair of prisms which, when placed together, form a prism block having parallel sides and having a thin intervening air space between the prisms.

Swan proposed applying transparent pictures to adjacent sides of the prism block; whilst observing the viewing face of the prism block, there is seen a three dimensional impression, apparently solid and embedded within the block, the light from one picture coming from it through the two prisms and direct to one of the eyes of the observer, whilst the light from the other picture, laterally reversed, is reflected at the surfaces of the prisms which are in contact and is then directed to the other eye of the observer, thus ensuring that each eye sees only its respective left and right picture view.

The teaching of Swan was to use rightangle prisms but with the other twp angles 40 degrees and 50 degrees respectively, or thereabouts. Such prisms are not readily available, and the adjacent sides^"had different dimensions. Λn observer using the Swan teaching is presented with a miniature (photographic) image view that gives an impression of depth only when the prism block is held at a particular angle. A magnified three-dimensional impression is achieved in the Swan teaching by the adoption of an alternative prism specification with an integrated convex viewing face on one of the prisms.

The proposal of Swan GB 3249 was put forward as a novelty item, not as an arrangement suitable for the studious observation of diapositives, or illuminated opaque pictures. No means of replacing or supplementing the naturally available light was taught. No means for using the prism block to view other stereo pairs was suggested.

We now seek to provide a stereo viewer which will have widespread utility, but without the need for binocular eyepieces. In particular we propose a stereo viewer using a prism block, with an external lens system between the viewing face of the prism block and the observer, whereby small or large pictures (relative to the interpupillary distance) of a stereo pair can alternatively be viewed. The viewing surface can be in a plane parallel to the observer's eyes, or angled slightly (usually up to 5 degrees). The readily-available rightangle prisms with the other two angles at 45 degrees can be used. The prism block can be mounted in a housing with an internal illumination source. Different stereo pairs can be viewed, including pictures replaced at more than sixteen frames each second as from film or a television screen.

Thus according to one feature of our invention we provide a stereo viewer which includes a prism block having a viewing face, and two adjacent prism sides through each of which one picture of a stereo pair can be viewed, the stereo image being viewed from a viewing position aligned with the viewing face characterised by a lens system between the viewing face and the viewing position. Preferably the lens system is both replaceable by another lens system, and adjustable in spacing towards and away from the viewing face.

According to another feature of our invention we provide a stereo viewer which includes a prism block having a viewing face, the prism block providing an optical assembly having a first external surface, a second external surface, a third external surface and an internal transmitting and reflecting assembly, the surfaces and assembly being arranged so that a stereo image can be viewed through the third external surface from a viewing position aligned with the third external surface, said third external surface being a stereo image viewing face, the stereo image being derived simultaneously from a first stereo picture of a stereo pair, on the first external surface and from a second stereo picture of the stereo pair on the second external surface, the first stereo picture being viewed in reverse by reflection at said assembly and the second stereo picture being viewed directly characterised by a lens system spaced adjacent to but spaced from the stereo viewing face, by mounting means for the stereo pair adjacent to but spaced from the prism block, and by a common support for the prism block, the mounting means and the lens system. Preferably the common support is an enclosed housing, usefully a hand-holdable housing.

In a preferred housing arrangement there is light reflecting means between a dedicated light source and the respective first and second pictures of a stereo pair e.g. diapositives which are illuminated to throw a picture on the first or second surface, each diapositive (transparency) being spaced from its surface.

The housing can be designed to utilise both an internal and an external light source (including natural daylight) in order to illuminate the stereo pairs; but alternative embodiments use only one of these light sources. Light diffusers can be provided, for more even illumination, as from point light sources.

Embodiments of the present invention will now be described by way of example, with reference to the accompanying schematic drawings in which:-

Fig.1 is of a prism block according to Swan GB 3249/1862, indicating the views seen by the left and right eyes;

Fig.2 is of the prism block of Fig.1 , but with a reversed reflecting angle;

Fig.3 is of an assembly according to the invention;

Fig.4 is of an alternative assembly according to the invention; Fig .5 is of an alternative prism block ;

Fig .6 is of a further alternative prism block ;

Fig.7 is a perspective view of an alternative embodiment , with connected stereo pairs;

Fig. is of an alternative assembly, with a single light source and parabolic reflector;

Fig.9 is of an alternative assembly, with a single light source and 45 degree reflector;

Fig.10 is of a further embodiment using stereo monitor pairs, with simultaneously moving images;

Fig.11 is a perspective view of an alternative transportable embodiment;

Fig.12 shows, in perspective a exploded view of another embodiment of the stereo viewer, depicting a typical arrangement of its salient features;

Fig.13 is a plan view of the stereo viewer of Fig.12; and

Fig.14 is a plan view of an alternative embodiment of stereo viewer, depicting an alternative diapositive illumination arrangement.

in the stereoscope taught by Swan (Fig 1 ) two prisms 10,12 are used, placed together to produce a solid having parallel sides. One angle of each prism is a right angle, and the other two _ Q

angles 40 degrees and 50 degrees respectively, or thereabouts. One picture is mounted on first surface 14, and the other picture of the stereo pair is mounted on second surface 16, the stereo image being viewed through third surface 1B. Internal transmitting and reflecting assembly 20 comprises a pair of glass faces in contact, but nevertheless with an air gap 22 therebetween. Left eye LE and right eye RE are in a plane defining the viewing position for that person. The (reversed) picture on surface 14 is reflected and seen by the left eye LE, and the picture on surface 16 is seen by direct vision by the right eye RE.

In Fig.2, the pictures are respectively on first and second surfaces 24,16, that from surface 1 to left eye LE being seen by light transmitted directly through the internal transmitting and reflecting assembly 20, and that from surface 24 to right eye RE being seen by reflection.

In the embodiment of the invention shown in Fig.3, the prism block 30 comprises two identical prisms 32,34 which each have as one angle a right angle and the other two angles at 45 degrees or thereabouts. The prism block 30 has a first external surface 35, a second external surface 36, a third external surface 37 forming the viewing face, and an internal transmitting and reflecting assembly 20a.

A stereo pair of diapositives 45,46 are spaced from the respective surfaces 35,36 so that the picture received thereon is by way of transmitted light. The stereo pair 45,46 are not physically mounted on the prism block 30, and can thus be replaced."

Adjacent to but spaced from viewing face 37 is a lens assembly 38a. Lens assembly 38a is located between viewing face 37 and the plane which when the viewer is in use includes left eye LE and right eye RE i.e. a viewing plane defining a viewing position for the observer.

In this embodiment the prisms 32,34 are of glass; but in alternative embodiments they are each of a transparent plastics material", or they are of triangular glass containers filled with water to the height at least of the light path through the prism block. In a further alternative embodiment as seen in Fig. 5 the prism block 50 is solid, but has a central slot 52. In the alternative embodiment of Fig.6 the prism block 60 comprises a glass or plastics container 62, in this embodiment square in plan, filled with water and with an internal sub-assembly 64 of a pair of glass or plastics plates 66 sealed around their periphery 68 to retain air between the plates; the glass partition may extend fully or partly across the diagonal of glass vessel 62, depending upon the extent of the required light path, and although shown spaced apart, the plates can be touching.

The embodiment of Fig.4 is of a larger prism block 40, of a size for viewing pictures 16b,24b which individually are larger than the interpupillary distance. Lens assembly 48a thus regulates the light path to the required angle, for comfortable viewing, with each eye receiving only the picture ntended for it, as easily determined by experiment or calculation; whereas for the smaller pictures of Fig.3 the lens assembly may provide magnification, this magnification will be needed for the larger pictures of Fig 4. It will be understood that commercially, the viewer can include one or more mountings 41 , each mounting suited to a different picture size, so that the lens assembly fitted will accord with the selected picture size; in a further alternative embodiment the lens assembly can be changed for another lens assembly, for viewer use with differently-sized pictures. The prisms can be solid (glass or plastics) or hollow but filled with a transparent liquid eg water from which the air bubbles have been removed prior to the prisms being sealed.

In an alternative embodiment the position of the lens assembly can be changed, towards or away from the viewing face 47.

Although the pictures are shown positioned for viewing by light transmitted therethrough, opaque pictures viewed by light reflected therefrom can be used, with mountings 41 also adjustable away from the prism block to allow even light reflection from across the respective pictures.

In the embodiment of Fig.7 the stereo viewer 70 has open-ended mountings connected to receive a set of stereo pairs 70a,70b etc mounted upon a Backing sheet 72 which can be folded at 90 degrees as shown, to pass (vertically as illustrated in Fig.7) across the respective faces of the prism block. The stereo image is viewed through magnifying lens 74; for the smaller pictures for which the Fig.7 embodiment is likely to be used, of a size less than the interpupillary distance, a magnifying lens may not be needed e.g if the prism block (of glass, and square in plan) is mounted slightly angled (anticlockwise rotation if 70a is the reflected picture) to the viewing plane of the left and right eyes.

Fig.8 indicates an internal dedicated light source 80, with a parabolic reflector 82 illuminating both diapositiveε 84,86 of a stereo-pair. The embodiment of Fig. also utilises one light source, usefully flourescent lamp 90 with light falling directly on transparency 96, and indirectly on transparency -**>4 (from the silvered surface 93 of 45 degree reflector 92). These light source arrangements can be used in conjunction with light diffusing means, though for most applications this will not be necessary. In alternative embodiments, more than one light source can be used, perhaps with a different reflector e.g a whitened strip or sheet, and perhaps of a reflector shape other than parabolic or planar; one or more diffusers can be used.

In the embodiment of Fig.10, the pictures are obtained from monitors 100,101. These can display, or in an alternative embodiment project, a sequence of "still" stereo pairs such as those indicated in Fig. 7, but preferably will be television type screens showing "moving" pictures "shot" respectively from inter-connected cameras 102,103, for the viewer to perceive continuous motion pictures in three dimensions through lens assembly 1 4; usefully the camera lenses will become closer or will converge in viewing angle automatically as the cameras "zoom in" on a subject. In an alternative arrangement, respective banks of slide projectors, coupled in pairs, can project simultaneous images onto the respective first and second surfaces, for unusual multiplex effects but in three dimensions. It will be understood that the projected pictures to the first prism block surface 105 will need to be reversed, as by suitable circuitry in or associated with camera 102 or monitor 100.

For portable study or recreation the unit 110 of Fig. 11 can be used, with a pair of liquid crystal screen units 111,112 carrying respective stereo-pair pictures received from video unit 113. Usefully the video unit can be replaced to permit stereo viewing of alternative scenes, through lens assembly 114. There can be an accessible control unit 115.

Referring to the accompanying larger-scale drawings, in Fig.12 the stereo viewer includes an optical assembly 2 having a first external surface A, a second external surface R, a third external surface C, and a fourth internal reflective surface E. The surface C is the viewing surface; in an alternative embodiment surface D can be the viewing surface, with surface B as the first external surface and surface A as the second external surface.

As seen in Figs. 12,13 and 14, the stereo viewer has a configuration that will enable a stereo pair, depicted as transparency slide films a and b and each held in a transparency mount, to be inserted through their respective slot a1 and b2, in the body top 1. Each slide may be located parallel to its corresponding prism face A and B between rear wall 6 and the surface A,B; and yet be spaced from respective surface A,B by engagement in this embodiment of the transparency mount with the corresponding surface A,B. In normal use, the slides will be upright.

The optical arrangement comprises a pair of plane prisms 2, placed together to form a parallelepiped, one angle of each prism being a right angle and the other two angles being 45 degrees or thereabouts; in alternative embodiments the other two angles may be between 40 degrees and 50 degrees. The optical arrangement is located within the main body 3 of the stereo viewer so that either face C or D may be chosen to be the viewing face; in Figs 12,13,1 face C is depicted as the viewing face; the slide a, therefore, will represent the right eye view, to be seen by reflection at the diagonal interface E, of the prisms, necessitating the lateral reversal of the image on slide a, prior to its insertion through slot a1.

Provision may be made within the body 3, for the location of an electrical power source 4, shown as dry batteries, and an associated light source 5 such as an electric filament bulb or a halogen or flourescent lamp; the latter may be positioned at the far end of the diagonal interface E, or thereabout, formed by the pair of prisms 2, in order that light may be evenly distributed between slides a and b via, in this embodiment a light diffusing arrangement 6, and light reflecting surfaces 7.

Each slide of a stereo pair may be illuminated by its own individual light source, whereby the observed stereo impression, seemingly located within the prism block, may be viewed to good effect, through one or more magnifying lenses 8, located concentrically in this embodiment, or nearly so in an alternative embodiment, with the viewing face C of the parallelepiped formed by prisms 2.

The stereo viewer may be adapted in order to utilize a mains electricity supply in conjunction with an accessory transformer. In the embodiment of Fig.12 an internal light source 5 and/or an external light source, such as the sky can be selected and utilized as required within their sole or shared configuration, to be evenly distributed between slides a and b. If an external light source only is required, then access is through an aperture F (Fig.14). An external light diffusing element may be attached to such aperture F, in addition to the light diffusing strip 6, or it may be utilized instead of the diffusing strip 6. If the option of a shared internal light source arrangement is required, then it will be desirable to adapt the body 3 in Fig.14, and incorporate a cover or hinged flap or equivalent faciity, in order to close external light access to the slides a and b whilst the internal light source is in operation, either at aperture F, or at an adapted alternative slide illumination access point on the body.

In order that the observer will conveniently view an effective three-dimensional impression, particularly when the external light source is selected, slide a will receive its light via the translucent diffuser strip 6 and reflector 9, respectively, whilst slide b, at face B, will receive its light directly via the said diffuser strip.

We thus provide a stereo viewing device that utilizes a combined pair of plane prisms, in order to present to an observer an enlarged three-dimensional impression, via one or more individual magnifying lenses 8, that will ensure the observer need not realise a particular viewing angle for the apparatus, in order to secure an apparent stereo impression; and so that its viewing face is concentric, or nearly so, with the magnifying lenses.

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Claims

1. A stereo viewer which includes a prism block having a viewing face, and two adjacent prism sides through each of which one picture of a stereo pair can be viewed, a stereo image being viewed from a viewing position aligned with the viewing face characterised by a lens system between the viewing face and the viewing position.

2. A stereo viewer according to Claim 1 characterised in that the lens system is adjustable in position, and replaceable.

3. A stereo viewer which includes a prism block having a viewing face, the prism block providing an optical assembly having a first external surface, a second external surface, a third external surface and an internal transmitting and reflecting assembly, the surfaces and assembly being arranged so that a stereo image can be viewed through the third external surface from a viewing position aligned with the third external surface, said third external surface being a stereo image viewing face, the stereo image being derived simultaneously from a first stereo picture of a stereo pair on the first external surface and from a second stereo picture of the stereo pair on the second external surface, the first stereo picture being viewed in reverse by reflection at said assembly and the second stereo picture being viewed by directly characterised by a lens system adjacent to but spaced from the stereo viewing face, by mounting means for the stereo pair adjacent to but spaced from the prism block, and by a common support for the prism block, the mounting means and the lens system.

4. A stereo viewer according to Claim 3 characterised in. that the common support is an enclosed housing, and in that the housing.-is sized to be hand-held, and further characterised by means to magnify the stereo image by a separate magnifying lens arrangement.

5. A stereo viewer according to Claim 3 characterised by releasable mounting means for the stereo picture pair, the picture pair after release from said mounting means being replaceable by another stereo picture pair, and further characterised by first and second light diffusing means between a light source and the respective first and second pictures.

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6. A stereo viewer- according to Claim 4 characterised in that the releasable first and second stereo pictures are film transparencies held in a transparency frame, and in that the releasable mounting means holds the frame ^■•but not the film transparencies against part of the respective first and secβϊid external _.surfaces.

7. A stereo viewer according to Claim 3 characterised in that the first and second stereo pictures are film transparencies located in pairs on a mounting strip, the viewer having an entrance and an exit whereby the strip can pass from the entrance to the exit, with the successive formation of different stereo images.

8. A stereo viewer according to Claim 1 characterised in that an internal electric light bulb, powered by dry batteries, provides a dedicated light source illuminating each respective picture.

9. A stereo viewer according to Claim 1 characterised by at least one pair of slide projectors adapted respectively to project the first and second pictures, and characterised by a pair of display units usable alone or in conjunction with the slide projectors and adapted respectively to create the first and second pictures, and further characterised in that the display units are a pair of television screens.

10. A stereo viewer according to Claim 1 characterised in that the prism sides are larger than the pupil spacing of a viewer, in that each respective picture is larger than said pupil spacing, and in that the lens system includes a magnifying lens selected from a group including a Fresnel lens to regulate the light from each picture so that light rays emergent from said lens from said respective pictures

SUBSTITUTE SHE C i have a pupil spacing separation.