This invention relates to an image pickup device and a display device for stereoscopic television.
In general, a stereoscopic television system is designed as shown in FIG. 1. On the image pickup side, two television cameras 1R and 1L disposed on both sides of an object form a video signal for right eye and a video signal for left eye (hereinafter referred to as "a right eye video signal" and "a left eye video signal", respectively, when applicable). These video signals are encoded by an encoder 2 into an encoded video signal which is applied to a transmission path 3. On the image reception side, the encoded video signal transmitted through the transmission path 3 is decoded into the right eye video signal and the left eye video signal.
The right eye video signal outputted by the decoder 4 is stored in a frame memory 5R. Similarly, the left eye video signal outputted by the decoder 4 is stored in a frame memory 5L. In response to addresses supplied from refresh counters 6R and 6L, the video signals stored in the frame memories 5R and 5L are simultaeously read and applied to a picture projecting tube 7R for right eye and a picture projecting tube 7L for left eye (hereinafter referred to as "a right eye picture projecting tube 7R" and "a left eye picture projecting tube 7L", respectively, when applicable). The right eye picture projecting tube 7R and the left eye picture projecting tube project the picture for right eye and the picture for left eye, respectively, onto a stereoscopic picture displaying screen 8, so that a person in front of the screen 8 can observe the stereoscopic picture.
The above-described stereoscopic television system handles the binocular sight similarly as in the eyesight of man. Therefore, the system suffers from a difficulty that the resultant picture appears unnatural because of a double-picture phenomenon.
The difficulty caused by the double-picture phenomenon will be described with reference to FIG. 2. FIG. 2 shows the image pickup side where a right eye camera IR for forming a right eye video signal and a left eye camera IL for forming a left eye video signal are used to photograph an object O. The object O is at the intersection of the optical axis of the right eye camera IR and the optical axis of the left eye camera 1L. Therefore, the object O is positioned not only at the center of the right eye picture formed by the right eye camera but also at the center of the left eye picture formed by the left eye camera. Accordingly, the object O can be observed as a clear stereoscopic picture on the image reception side. The above-described intersection of the two optical axes will be referred to as "a camera's observation point", when applicable.
It is assumed that, in FIG. 2, the cameras 1R and 1L have the fields of visions defined by the dotted lines and the solid lines, respectively, and there is a wall S behind the object O (the camera's observation point). In this case, a picture formed by the left eye camera 1L has the left end A and the right end B, while a picture formed by the right eye camera 1R has the left end a and the right end b. On the image reception side, the left ends A and a and the right ends B and b are displayed in such a manner that the left ends overlap each other and the right ends overlap each other. As a result, double images appear on the screen, and the resultant picture on the screen is unnatural. Observation of such a picture for a long time strains the eyes.
For instance, the image of an object point P on the wall S is shifted to the left from the center of the horizontal scanning line HL formed by the left eye camera 1L and to the right from the center of the horizontal scanning line HR formed by the right eye camera 1R, as shown in FIG. 3. Therefore, if the horizontal scanning lines formed by the right and left eye cameras are supplied to the picture projecting tubes on the image reception side so as to be observed simultaneously, then this is equivalent to the case where images are displayed with one horizontal scanning line, i.e., the resultant picture is unnatural because of the double images.
As is apparent from the above description, when an object is remoter from the cameras than the camera's observation point, the image of the object observed by the left eye camera is shifted to the left from its actual position, while the image of the object observed by the right eye camera is shifted to the right from its actual position. These images are referred to as "same-side double images". On the other hand, when an object is located between the camera's observation point and the cameras, the image of the object observed by the left eye camera is shifted to the right from its actual postion, while the image of the object observed by the right eye camera is shifted to the left from tis actual postion. These images are referred to as "different-side double images".
As is apparent from the above description, with the conventional stereoscopic television display device, an object located away from the camera's observation point form double images, which makes the resultant picture unnatural. This difficulty relates to the fact that an observer cannot freely select a point other than the camera's observation point as his own observation point.
It is assumed that FIG. 2 shows the case where a concert is being photographed, and the object O is a main performer while the object point P is an accompanist. The camera's observation point is placed on the main performer which is playing enthusiastically, while the stereoscopic image of the main performer is satisfactorily reproduced on the image reception side. At the same time, the accompanist behind the main performer is observed as double images. Therefore, observation of the resultant picture for a long time will strain the eyes.
In the stereoscopic television system in FIG. 1, one example of the stereoscopic picture displaying screen 8 is made up of a half-mirror which combines images projected by the picture projecting tubes. In this case, the observers wears special spectacles to observe stereoscopic images. The special spectalces allow the right eye to observe an image formed by the right eye video signal and the left eye to observe an image formed by the left eye video signal. In this case also, difficulties similar to those which have been described with reference to FIG. 1 are caused.