GB2183900A

GB2183900A - Stereoscopic cathode ray tube display

Info

Publication number: GB2183900A
Application number: GB08530159A
Authority: GB
Inventors: Maurice Clifford Heard
Original assignee: General Electric Co PLC
Current assignee: General Electric Co PLC
Priority date: 1985-12-06
Filing date: 1985-12-06
Publication date: 1987-06-10
Also published as: GB8530159D0; GB2184286A; GB8604340D0

Abstract

In an arrangement for producing an integral stereogram or a parallax panoramagram by displaying two pictures simultaneously in the form of interleaved strips on the screen 6 of a cathode ray tube and viewing the display through a lenticulate sheet 7, the latter is disposed either within, or on the inner surface of, the tube envelope, to avoid the limitation on the focal length of the lenticular lenses otherwise imposed by the thickness of the envelope glass. <IMAGE>

Description

SPECIFICATION A cathode ray tube This invention relates to a cathode ray tube comprising a phosphor layer on which two or more images are created and a lenticular member enabling an integral stereogram or a parallax panoramagram to be produced from those images.

It is known to superimpose different pictures by subdividing each of them into strips and interleaving the strips to form a combined picture in which one set of alternate strips belong to one picture and the other set of alterate strips belong to the other picture. If the combined picture is placed behind a suitable lenticular member an angular displacement of light emitted from the different images can be obtained so that a viewer sees a different image for different positions of observation. If several suitable pictures are superimposed, this technique can be used to produce a so called parallax panoramagram whereby an observer sees different images of a subject as he moves his head from side to side; just as if he were viewing a real object.

With just two suitable pictures the technique can also be used to produce a stereogram in which an observer positioned at the correct place sees different images with different eyes to give a stereoscopic effect.

The use of a lenticular member to produce a stereogram is described in U.S. Patent No.

725567 and by Herman in ''Principles of Binocular 3-D Displays with Applications to Television" Journal of SMPTE July 1971.

We have now realised that this technique can be applied to an image on a cathode ray screen.

The finite thickness of the faceplate of the tube (necessary for physical strength) means that the image on the fluorescent layer of the cathode ray tube is necessarily spaced some distance away from a lenticulate sheet fitted to the outer surface of the faceplate. This is of significance because the spacing is inversely related to the aforementioned angular displacement. Thus a large spacing between the fluorescent layer and the lenticular sheet means that the angular displacement is relatively small. This in turn means that the observer's eyes need to be placed an inordinate distance from the screen for a correct stereo picture or panoramagram. This difficulty cannot be overcome by making the tube bigger since that would necessitate an even thicker faceplate which would increase rather than resolve the problem. Possibly for these reasons this technique has remained unexploited.

This invention provides a cathode ray tube comprising a phosphor layer on which two or more images are created, and a series of lenticles enabling an integral stereogram or a parallax panoramagram to be produced from the said images; characterised in that the lenticles are inside or on an inside surface of the tube.

The focal length of each lenslet of the lenticulate member is preferably such that its focal point is coincident with the phosphor. This means that point sources on the phosphor produce parallel rays which are focussed by the relaxed eye to form a point image on the retina.

If the phosphor is inside the focal point, producing a divergent beam, the system will still work but the eye must be focussed, possibly resulting in eye strain. However such a system would be possible within the scope of the invention.

By empioying the invention the aforementioned problem can be avoided because the phosphor layer can be placed in the ideal position. This will preferably be on the rear surface of the lenticulate member (see Fig. 1), or on a separate glass plate (see Fig. 2) if reversed lenticles are built into the CRT faceplate.

Since the production of large cathode ray tubes is relatively expensive it is an advantage to have a small cathode ray tube which produces a large image and, to that end, cathode ray tubes constructed in accordance with the invention may incorporate a front faceplate modified or shaped to define a lens of positive power to produce an image which is considerably larger than the size of the cathode ray tube itself.

Two ways in which the invention may be performed will now be described by way of example with reference to the accompanying drawings which show horizontal cross-sections through cathode ray tubes constructed in accordance with the invention.

The illustrated cathode ray tubes comprise a glass envelope 1 containing an electron gun 2 and anode 3 which produce a beam of electrons which is deflected by X and Y deflection coils, only the Y deflection coils 4 being shown. The brightness input 5 to the cathode ray tube is controlled by a system (not shown) so as to produce, on a phosphor layer 6, two pictures appropriate to the left eye LE and right eye RE respectively. The left eye image is formed by strips L and the right eye image is formed by strips R interleaved with the strips L. In the drawing a left hand strip L and and a right hand strip R are shown directly behind each lenslet with no spacing between them. However in practice there may be a spacing and the points between adjacent L & R strips need not be immediately behind the centres of the lenslets.The precise arrangement of the L & R strips is as would be obtained using the photographic process described on page 197 of the book stereoscopy by N. A. Valyus published by Focal Press.

In Fig. 1 the phosphor layer 6 is formed on the rear side of a lenticulate plate 7 which notably is located inside the glass envelope 1.

The lenticules are shaped so that their focal points lie on the phosphor layer. The plate 7 is supported by struts 8.

The effect of the lenticulate plate 7 is to ensure that the left eye LE of the observer sees all the strips L but not any of the strips R whilst the right eye RE sees all the strips R but not any of the strips L. The observer thus sees a stereoscopic image.

In a variation of the embodiment which has been described the front face of the cathode ray tube incorporates, at the position of the broken line 9, a lens of positive power. The effect of this is to provide an enlarged image which may in practice be more economical than building a large custom tube.

In Fig. 2 parts similar to those of Fig. 1 are denoted by the same reference numerals. In Fig. 2 the phosphor layer is formed on the rear side of a separate relatively thin transparent supporting plate 10 which is mounted behind a lenticular screen incorporated into the CRT faceplate. In this variation the sense of the lenticles is reversed with respect to Fig. 1.

However, the effect is identical in that integral lenticles are being used to create a stereoscopic image from a pattern formed on a phosphor layer.

The illustrated examples are for the purpose of producing a stereoscopic image but it is also possible for it to produce a parallax panoramagram such that the observer sees different images of an object when he moves his eye to different positions just as if the object really existed. This can be done by providing a multiplicity of stereo pairs of images across the width of the phosphor screen in a manner well known.

Claims

1. A cathode ray tube comprising a phosphor layer on which two or more images are created and a series of lenticles enabling an integral stereogram or a parallax panoramagram to be produced from the said images; characterised in that the lenticles are inside or on an inside surface of the tube.

2. A cathode ray tube according to claim 1 in which the series of lenticles are defined by a transparent sheet located in the tube and having the phosphor layer on one side thereof.

3. A cathode ray tube according to claim 1 in which the series of lenticles is formed on an inner surface of a faceplate of the tube and in which the phosphor layer is carried on a relatively thin transparent supporting plate located in the tube adjacent the faceplate.

4. A cathode ray tube according to claim 1,2 or 3 in which the cathode ray tube has a faceplate defining a lens of positive power.

5. A cathode ray tube substantially as described with reference to the accompanying drawings and substantially as illustrated therein.

CLAIMS Amendments to the claims have been files, and have the following effect: Claim 1 above has been deleted or textually amended.

New or textually amended claims have been filed as follows:

1. A cathode ray tube comprising a phosphor layer on w.hich two or more images are created and a seies of lenticles enabling an integral stereogram or a parallax panoramagram to be produced from the said images; characterised in that the lenticles are inside or on an inside surface of a faceplate of the tube and have a focal length shorter than the thickness of the faceplate.