GB1575851A - Apparatus for stereoscopic photography - Google Patents

Description

(54) APPARATUS FOR STEREOSCOPIC PHOTOGRAPHY (71) I, JAMES ERNEST IHMS, a citizen of the United States of America, of 1569 West Hazelwood, Phoenix, Arizona 85015, United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the c..llowing statement: The present invention relates to three dimensional photography, and a particular form of the invention relates to apparatus attachable to a camera for obtaining a single photographically recorded full colour content composite image containing the requisite information content to provide a three dimensional view of a photographed scene.

Stereoscopic photography has had intermittent public appeal since approximately 1839 when the first black and white stereo photographs were made. The stereo concept then employed can be traced to thoughts first propounded by Leonardo de Vinci in 1584.

Traditional stereo photography may be described as follows. Two laterally displaced substantially simultaneously exposed negatives,-positives, or impressions in the case of television, are taken to obtain two images of a scene. The images are slightly different because of the lateral displacement, resulting in slightly different lines of sight of the scene. For best real life simulation, the lateral displacement should be equivalent to the distance between the viewer's eyes. The negatives, positives, or impressions are viiwed through a stereo opticon device which permits each eye to see only one of the images portrayed by the negatives, prints, or impressions. The difference in the two images seen by a viewer Is translated by the viewer's brain into a sense of depth to give the viewed scene a three dimensional quality.

If coloured images, rather than black and white images, are feasible, image decoding techniques other than physical separation of two images when viewed can be used.

The separation may be effected by producing a first image along one line of sight of a scene which is limited in colour content by a filter to one half of the visible light spectrum and producing a second image along another line of sight of a scene which is limited in colour content by a filter to the remaining half of the visible light spectrum. The two images are combined to form an anaglyph and projected onto a common screen for a movie or slide show, or printed upon a printing medium.

The resulting anaglyph is viewed by placing a different colour filter in front of each eye. The filters, which are usually substantially but not completely mutually exclusive, permit each eye to see only one of the colour limited images of the scene.

As each eye only sees one of the images, each eye sees the same scene but as viewed along a slightly different line of sight. Thus, a slight discrepancy exists in the scene presented to each eye. This discrepancy is translated by the brain to provide a sense of depth and hence, provides a three dimensional effect to the scene photographed.

The advances since 1839 in both black and white and colour stereo photography have been essentially limited to improvements in equipment resulting in greater registration, better optics and improved projection systems. Despite the amount of work done and the many improvements generated, no significant substantive changes in the three dimensional image reproduction have been developed. That is to say, the methods for effecting stereo photography have remained substantially unchanged.

Because of the requirement of double negatives in early stereoscopic photography, various devices have been developed to portray the necessary information on a single negative. United States Patent No.

2,639,653 illustrates apparatus using a rotatable disc or sliding diaphragm adjacent the objective lens to obtain slightly different views of the same scene. A specially constructed viewing device displays one of the views to each eye of the observer. Thus, a stereoscopic effect is achieved.

In United States Patent No. 2,317,875, a plurality of rectangular prisms are employed to form a plurality of picture strips, each strip conveying a part of the picture.

Alternate ones of the strips from the total picture are transmitted through a first lens system. The remaining strips from the total picture are transmitted through a second lens system. The stereoscopic effect is obtained by viewing the composite strip through a special viewer which segregates one set of strips to impinge upon one eye and the other set of strips to impinge upon the other eye.

In the apparatus described in United States Patent Nos. 2,360,322 and 2,751,826, two colour segregated images taken along different lines of sight of the same scene are received and simultaneously recorded on the same piece of film. In operation, a first bundle of light rays are transmitted through and limited in colour content by a first filter and impinge on one surface of an angled semi-reflecting mirror with some of the light rays being reflected therefrom and the remaining light rays being transmitted therethrough. A second bundle of light rays are transmitted through and limited in colour content by a second filter, and reflected by a mirror to impinge upon the semi-reflecting mirror with some of the light rays being reflected therefrom and the remaining light rays being transmitted therethrough. The first and second filtered bundle of light rays are substantially mutually exclusive in colour content through the action of the first and second filters.

The light rays of the first bundle transmitted through the semi-reflecting mirror are combined with the light rays of the second bundle reflected by the semireflecting mirror to form an anaglyph. The anaglyph is recorded on film and viewed through glasses having filters corresponding to the first and second filters. A disadvantage of this system is that neither image is of full colour content. Moreover, the images are not completely mutually exclusive in colour as reciprocally exclusive filters cannot be manufactured. Thus, colour cross-talk will be present. Furthermore, less than half of the light content of the light rays transmitted through the corresponding filters and less than half of the light content of the light rays is transtnitted through the semi-reflecting surface. Thus, the light content of the composite image striking the film is less than one half of the total light content of the two received light rays.

Semi-reflecting mirrors or surfaces are normally coated with a substance to render them semi-reflecting. The coating substance causes a deterioration in the quality of each image because of the impurities inherent within the coating substance.

A recent United States Patent No.

3,712,199, describes apparatus for producing an image to provide a psychophysiological illusion of depth. This system, contrary to two most stereoscopic systems, does not use two laterally displaced images. Instead, a single line of sight is employed in photographing the object. Within the lens system itself, one half of the received light rays are filtered by a first colour filter while the second half of the received light rays are filtered through a second colour filter.

Both filtered light rays are combined to form an anaglyph. The anaglyph is viewed through coloured glasses having a pair of lenses each of which correspond to a respective one of the colour filters. Thus, one eye of the viewer can detect only that portion of the anaglyph transmitted through the second colour filter of the lens system.

As there is no initial lateral separation of the two colour segregated images, the anaglyph is not a true three dimensional image but appears to present the illusion of a three dimensional image.

It may be noted that all of the above described apparatuses produce a pair of superimposed mutually exclusively coloured images through use of a pair of mutually exclusive colour filters and the resulting anaglyph is viewed through coloured glasses having lens corresponding to the colour filters.

Other United States patents directed to various three dimensional photographic apparatus includes: Nos. 475,084; 1,595,984; 2,045,119; 2,386,413; 2,749,820; 2,895,374; 3,642,349; 2,301,254; 2,568,327; and 3,846,810 (discussed further below).

According to the present invention there is provided an apparatus for simultaneously combining a first image of an object and a second image of the object to form a non-anaglyph coloured composite image having a three-dimensional quality after decoding, the first and second images being received by the apparatus along first and second light ray paths, respectively, the first and second light ray paths being angularly displaced from one another, the apparatus comprising: a light reflecting element for intercepting the first light ray path for transmitting the first image along a third light ray path to intersect the second light ray path; a colour filter other than a dichroic filter disposed at the intersection of the second light ray path and the third light ray path for combining the second image and the reflected first image, the colour filter being angularly orientated to transmit a part of the first image along a continuation of the third path and to reflect the remaining part of the first image along a continuation of the second path to become a portion of the composite image and to transmit a part of the second image through the colour filter means for colour filtering the said part of the second image along the said continuation of the second path to become the remaining portion of the said non-anaglyph composite image and to reflect the remaining part of the second image along the said continuation of the third path; and light sensitive means for recording the composite image thus produced.

In order to understand the present invention it may be helpful to refer here to an article entitled "An Astonishing New Theory of Color" appearing in the May, 1959 issue of Fortune. The article describes the exploratory work performed by Dr.

Edwin H. Land in 1955. In essence, Dr.

Land obtained a first transparency taken through a red filter and a second combined transparency taken through a green filter and blue filter. The image of the first transparency (first image) was projected on to a screen after being filtered through a red filter. The image of the second transparency (second image) was superimposed on the first image by projecting it with the aid of a white light source. Both projected images were carefully adjusted to be in registration with one another. The resulting composite image had a full colour content which Dr. Land could not explain. Instead, he considered it to be a physiological phenomenon as be could not capture it on a light sensitive medium, i.e. film. This work by Dr. Land helped form the basis of the present invention.

The present invention can be used for producing a composite image of a scene, which image has a three dimensional quality.

The apparatus of the invention may superimpose two images of differing content but full colour of the same scene taken along different lines of sight.

The invention may be used to provide a dual input aperture filter system for a camera, which filter system combines a filtered image and a white light image of a photographed scene and transmits the combined image to a light sensitive medium.

In an embodiment of the present invention two full intensity but different colour content images corresponding to two views along different lines of sight of the same object are combined to produce a composite decodable image, which image has a three dimensional quality after decoding.

The present invention may be in the form of an attachment for a camera to combine two full colour content images into a decodable composite image recordable on the light sensitive medium of the camera.

The present invention may be used to transform two white light images of a scene into a non-anaglyph composite image formed of two segregatable images with a single colour filter.

In one embodiment of the present invention two black and white images, each image corresponding to one of two views taken along different lines of sight of the same object are combined to produce a composite decodable image, which decodable image has a three dimensional quality after decoding.

In an embodiment of the invention a black and white image is combined with a colour filtered black and white image, each image corresponding to one of two views taken along different lines of sight of the same object to produce a composite decodable image, which decodable image has a three dimensional full colour quality after decoding.

In the accompanying drawings, Figure 1 illustrates an embodiment of the present invention attached to the lens of a camera; Figure la is a diagrammatic illustration of the present invention; Figure '2 illustrates the basic image combining system of the present invention Figure 3 is a perspective view of focusing and alignment apparatus usable with the present invention; and The appearance of three dimensionality in images can be created by superimposing two different views of the same scene to form a composite image. The illusion of depth is often enhanced if the composite image is viewed through an image decoding device. If the two views are laterally displaced from one another by an amount approximately equal to the distance between a viewer's eyes, the resulting image will have essentially the same three dimensional appearance as if the viewer were seeing the scene personally. Where the separation is greater than that between the viewer's eyes, the three dimensional effect is exaggerated. Similarly, if the distance is less the three dimensional effect is minimized.

The composite is in register at the point where the two lines of sight cross one another. Those elements of the scene being closer or further away, will be out of register. This situation is similar to that which occurs in real life.

Referring to Figure 1, there is shown apparatus incorporating the present invention and used in conjunction with a camera for obtaining a composite image of a scene which is viewed along two different lines of sight. A camera 1, which may be a highly complex instrument or a very simple camera, such as those cameras sold by the Eastman Kodak Company under the trademark "Instamatic", includes a lens system 2. A housing 3 is detachably secured to the lens system. The exact mode of attaching the housing may, of course, be varied to suit the lens system.

Housing 3 includes a light transmissive element 4, which element is a colour filter and a light reflective element 5, which may be a mirror. The distance between the centres of the elements 4 and 5 is approximately two and one half inches, which is the average distance between a person's pupils. For special needs or effects, the distance may be increased or decreased.

An illustration of the operation of the present invention is shown in Figure la.

A first bundle of light rays from object 9 will impinge upon the front surface of the light transmissive element 4. At least a part 7 of the first bundle of light rays will be transmitted therethrough into lens system 2 into camera 1. The transmitted first bundle of light rays will define a first image 9' of the object 9. A second bundle of light rays, identified by numeral 8, will impinge upon the light reflective element 5.

The second bundle of light rays 8 is reflected as light rays 6 by the light reflective element 5 to the rear surface of the light transmissive element 4 and defines a second image identified by numeral 9".

The light transmissive element shown in Figure la is a colour filter such as a red or blue content filter. Hence, the first bundle of light rays impinging upon the red filter is modified in colour content by the filtering action of the red filter. Thus, two bundles of light rays, which differ in colour content, intersect one another at the light transmissive element 4.

When two light beams intersect one another at a light transmissive surface (i.e.

light transmissive element 4), an interaction of the light beams will occur. That is, the light beams will serve as mutual colour filters for one another such that each of the reflected and transmitted beams of light of each impinging beam of light will be altered in colour content. Thus, the images 9' and 9" corresponds to the image presented by the first and second bundle of light rays, respectively, except that they are modified in colour content by the light interaction occurring at the transmissive element 4.

More specifically, the first bundle of light rays is limited in colour content to one segment of the visible light spectrum. This first bundle of light's rays, interacting with the second bundle of light rays will tend to modify the colour content of the latter.

Conversely, the second bundle of light rays, being initially essentially white light, will modify or add to the colour content of the first bundle of light rays because of the light interaction occurring at the transmissive element 4. Thus, the images 9' and 9" are not limited in colour content to one or another half of the visible light spectrum.

Instead, each image 9' and 9" contains a full range of colours.

By experiment, it has been learned that the composite image formed by images 9' and 9" contains two full colour images, one corresponding in subject content to the first bundle of light rays and the other corresponding in subject content to the second bundle of light rays. The two images, after being recorded on a photo sensitive medium as the composite image, can be segregated from one another by viewing the composite image through a pair of glasses having a red and a cyan lens.

When so viewed, the composite image has the depth of a three dimensional representation.

The light paths within the housing 3 are shown schematically in Figure 2. A first light ray 10 emanating from an object to be photographed is received by and transmitted through light transmissive element 14, a colour filter. The element 14 transmits the filtered light rays of the first light ray 10 which form a part of the bundle of light rays identified as composite ray 13.

A second light ray 11 represents the light rays emanating from the same object as light ray 10. However, light ray 11 is angularly displaced from light ray 10, which displacement results in some differences in information between the two rays. The whole of light ray 11 is reflected by a light reflective element 15 to the light transmissive element 14. If the light transmissive element 14 is a red colour filter, it will reflect some of the light rays of the second light ray 11 which form a part of the bundle of light rays identified as the composite ray 13. Numeral 12 identifies the light rays of light ray 10 and the transmitted light rays of light ray 11.

From the above description, it may be understood that the colour content of the contributions to composite ray 13 of light rays 10 and 11 are altered in colour content such that each of the images represented therein is of full colour content.

In the preferred embodiment, the light transmissive element has been selected as a red colour filter. However, it is to be understood that other non-dichroic colour filters may be employed instead in the present invention.

The information contained in the composite light ray 13 is sufficient to produce two superimposed images of an object where each image portrays the object as seen along one of two angularly displaced views. One image is formed by the light rays transmitted through the filter while the other image is formed by the light rays reflected by the same filter. These images are recorded upon a light sensitive medium.

The illumination provided by either of the light rays 10 and 11 is diminished by the light transmissive element 14. However, as the light rays of light ray 10 that are filtered by the red filter are combined with the reflected light rays of light ray 11, the composite light ray 13 includes substantially the same illumination as either of light rays 10 or 11. Thus, the aperture of the lens system 2 of the camera 1 (see Figure 1) using the present invention may not need to be adjusted to accommodate the filtering of the incoming light rays.

The photographic recording medium, either positive or negative colour film, within the camera exposed by the composite light ray 13 will respond to the composite light ray and record both images thereon as a composite image. The images will be substantially in registration and the resulting positive or print will be of acceptable quality for general viewing purposes. When the positive is projected on to a screen for viewing or when a print of the negative or positive is viewed, the viewer may or may not obtain a sensation of third dimensionality. If the sensitivity of the viewer's eyes are mis-matched in colour sensitivity, a sense of three dimensionality may be readily apparent. To obtain the full effect of a third dimension of the photographed object, the viewer should don a pair of glasses having a blue content lens and a red content lens. The red content lens should be used in front of the eye corresponding to light ray 10 while the blue content lens should be used in front of the eye corresponding to the light ray 11. With this arrangement, one of the eyes eyes will see the object as conveyed by the light ray 10 and the other eye will se the objected as conveyed by the light ray 11. As each eye sees the object from a different view point, or line of sight, the object will appear to be three-dimensional, that is to say, the composite image will have depth.

Although the light ray interaction process which occurs at the intersection of the two intersectiig light rays is not fully and wholly understood, a hypothesis has been developed. It is known that the light rays from a light source are changed or altered in colour and/or tone content to one range of the visible light spectrum when the light rays are reflected from the surface of a colour filter. Similarly, the light rays are changed or altered in colour and/or tone content to another range of the visible light spectrum when the light rays are transmited through colour filters. As a result, a colour filter is capable of producing two different colour content images, depending on whether the received image is reflected from or tranmitted through the colour filter. Based upon the above knowledge, it is hypothesized that the following phenomenon occurs at the plane of interaction between the two intercepting light rays.

The light or image transmitted through the colour filter contains areas having the colour of the colour filter and non-light areas representative of the reflected complementary colour (i.e. if the colour filter is red, the transmitted image contains red and not light areas representative of blues, greens and yellows of the original image).

The light rays from the white light image intercept the filtered light rays. Due to the interaction of the intercepting light rays, the colours complementary to that of the colour filter (i.e. blues, greens and yellows) impinging upon the non-light areas of the filtered light ray are reflected. Thus, the filtered image striking the recording medium contains the colour of the light transmitted through the colour filter and the complementary colours introduced by the non-filtered image and reflected by the non-light areas at the plane of interaction.

A similar but reversely operating colour discrimination process occurs for the received non-filtered image. That is to say, all of the colours of the non-filtered image are reflected at the plane of interaction to form one image of the composite, which colours are complementary to that of the filter. The non-complementary colours are not reflected, as they are transmitted through the filter. Hence, they represent non-light areas of the image.

These non-light areas will, however, appear to have colour due to the addition of colour provided by the colours of the filtered image transmitted through the filter at the locations of the non-light areas. Thus, the image contributed by the received and initially filtered image and the received initially non-filtered image to the composite image each contains full colour. Each image of the composite image will have full colour and can be selectively viewed through a coloured eye-piece (red for the initially filtered image and blue for the initially non-filtered eye-piece if the filter is red coloured).

In further explanation, one could categorize the colour combining phenomenon as employing both additive and subtractive colour processes. That is to say, a nonlight area will appear as the complementary colour of the filter yet the light areas will appear in various colours and transmit the correct amount of light through the colour filter (non-light areas appearing as blue will appear black when added to a red filter, subtractive colour, red areas of the same image will appear as light through the same red filter, additive colour).

It will be apparent that the present invention differs from the prior art in that in the prior art a composite image was formed as an anaglyph (two mutually exclusive colour content images superimposed on one another) and viewed through eye pieces complementary to the filters.

As described in United States Letters Patent No. 3,846,810, various means may be incorporated for colour correction and light path length extension or attenuation, and attention is directed thereto for a description thereof.

From experimentation with the apparatus of the present invention, it has been learned that a full colour decodable composite image having a three dimensional quality can be obtained from two black and white positive. A first one of the black and white positives of an object is obtained by conventional means. The second one of the black and white positives of the object is taken through a colour filter and along a slightly laterally spaced line of sight. To obtain the composite image, the first positive is placed in light path 11, and the second positive is placed in light path 10 (see Figure 2). A light source placed rearwardly of each positive projects the image of the respective positive along one of the identified light paths. The first and second images produced from the first and second positive are combined in an interacting relationship at element 14.

The resulting composite image, light ray 13, has a full- colour content which is directly viewable or recordable upon a colour sensitive recording medium. Moreover, the same interaction can also be applied to pairs of previously non-filtered black and white or coloured images which have been obtained of a scene along slightly divergent lines of sight (i.e. by conventional double image stereoscopic cameras).

It is to be understood that the separate elements shown in Figures 2 may be combined in a single monolithic structure, such as prism. Similarly, anti-reflective coatings may be employed on the surfaces of the light reflecting and light transmitting elements to reduce distortion created by refraction.

l'he housing is shown in further detail in Figure 3. It is formed by a casing 80 containing the various previously discussed light transmissive and light reflective elements. An aperture 82 is disposed in the rear surface 81 to receive the lens system of a camera. Retaining elements 83 secure the housing 3 to the lens system.

It is to be understood that the retaining elements 83 may be varied to suit particular applications.

The light transmissive element 4 (identi- fied in Figure 2 as element 14) is normally firmly lodged within the casing 80 to intersect the viewing angle of the lens system 2.

The reflecting element 5 (identified in Figure 2 as element 15) is normally pivotally mounted within the casing 80 by a mounting mechanism 85. It is to be understood that the elements 4 and 5 could be permanently, removably or adjustably mounted within the housing.

The mounting mechanism 85 may be formed by a yoke 86 pivotally secured to a base 87 by a pivot point 88. A spring biassed adjustment screw mechanism is disposed intermediate a flange 90 extending upwardly from the base of yoke 86 and a side of the casing 80. As is well known to those skilled in the art, the turning of screw 92 will cause the yoke 86 to pivot about its pivot point 88. Thus, the adjustment mechanism may be used to obtain registration between the two received images.

The rear surface of the reflecting element 5 includes a pair of flanges 93 and 94 extending rearwardly therefrom and forming a part of the mounting mechanism 85. Each of these ranges is pivotally mounted upon one of the arms of the yoke 86. A second adjustment mechanism may be disposed intermediate flange 90 extending from the base of the yoke 86 and the rear surface of reflecting element 5. By turning the screw 97 of the second adjustment mechanism, the reflecting surface 5 pivots ab eye receives the other image. As discussed above, the person's brain will attribute a sense of three dimensionality to the image viewed because of the two similar but not identical images.

WHAT IS CLAIM IS:- 1. An apparatus for simultaneously combining a first image of an object and a second image of the object to form a nonanaglyph coloured composite image having a three-dimensional quality after decoding, the first and second images being received by the apparatus along first and second light ray paths, respectively, the first and second light ray paths being angularly displaced from one another, the apparatus comprising: a light reflecting element for intercepting the first light ray path for transmitting the first image along a third light ray path to intersect the second light ray path; a colour filter other than a dichroic filter disposed at the intersection of the second light ray path and the third light ray path for combining the second image and the reflected first image, the colour filter being angularly orientated to transmit a part of the first image along a continuation of the third path and to reflect the remaining part of the first image along a continuation of the second path to become a portion of the composite image and to transmit a part of the second image through the colour filter means for colour filtering the said part of the second image along the said continuation of the second path to become the remaining portion of the said nonanaglyph composite image and to reflect the remaining part of the second image along the said continuation of the third path; and light sensitive means for recording the composite image thus produced.

2. An apparatus as claimed in claim 1, wherein the filter comprises a red content colour filter.

3. An apparatus as claimed in claim 1, wherein the colour filter comprises a blue content colour filter.

4. An apparatus as claimed in any preceding claim, wherein the light sensitive means comprises a colour sensitive photographic film.

5. An apparatus for forming a composite image, substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. eye receives the other image. As discussed above, the person's brain will attribute a sense of three dimensionality to the image viewed because of the two similar but not identical images. WHAT IS CLAIM IS:-

1. An apparatus for simultaneously combining a first image of an object and a second image of the object to form a nonanaglyph coloured composite image having a three-dimensional quality after decoding, the first and second images being received by the apparatus along first and second light ray paths, respectively, the first and second light ray paths being angularly displaced from one another, the apparatus comprising: a light reflecting element for intercepting the first light ray path for transmitting the first image along a third light ray path to intersect the second light ray path; a colour filter other than a dichroic filter disposed at the intersection of the second light ray path and the third light ray path for combining the second image and the reflected first image, the colour filter being angularly orientated to transmit a part of the first image along a continuation of the third path and to reflect the remaining part of the first image along a continuation of the second path to become a portion of the composite image and to transmit a part of the second image through the colour filter means for colour filtering the said part of the second image along the said continuation of the second path to become the remaining portion of the said nonanaglyph composite image and to reflect the remaining part of the second image along the said continuation of the third path; and light sensitive means for recording the composite image thus produced.

2. An apparatus as claimed in claim 1, wherein the filter comprises a red content colour filter.

3. An apparatus as claimed in claim 1, wherein the colour filter comprises a blue content colour filter.

4. An apparatus as claimed in any preceding claim, wherein the light sensitive means comprises a colour sensitive photographic film.

5. An apparatus for forming a composite image, substantially as herein described with reference to the accompanying drawings.