Computer graphics processing and selective visual display system – Image superposition by optical means – Operator body-mounted heads-up display
Patent
1995-08-30
1997-10-28
Tung, Kee M.
Computer graphics processing and selective visual display system
Image superposition by optical means
Operator body-mounted heads-up display
348 53, 359630, G04G 500
Patent
active
056821735
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an image display device, particularly a TV image display device, wearable on head.
Head worn TV image display devices are known in the art. One part of said devices has a stereoscopic system, i.e. the viewer sees two different images or screens with the left and right eye, respectively. Stereoscopic devices are described in U.S. Pat. Nos. 5,123,726, 5,129,716, 4,897,715, 4,706,117, and in German Patent Specification No. 1103961, especially in the part relating to FIG. 5. The drawback of head worn TV devices is that two image display units should be built in, practically resulting in double expenses, weight, volume and failure rate. On the other hand, it is an advantage that the image can be seen with both eyes.
Head worn TV sets having only one screen are also known. Such devices are described e.g. in the above mentioned German Patent Specification No. 1103961 (FIG. 2), and in the USA product catalog "Sharper Image" (June, 1993) relating to a device called "Virtual Vision Sport". A major drawback of said devices results from the fact that the single screen can be viewed with only one eye, i.e. while one eye is fixed on the screen, the other one sees the surroundings in the same direction, which is rather disturbing. And if the user of the device closes the other eye while viewing the TV picture, he/she is forced to blink, which is tiring.
It is also known from the above-mentioned German Patent Specification No. 1103961 (claim 9 and the corresponding disclosure) that a cathode-ray tube is built in one of the side-pieces of a spectacle-like device, and the picture produced by the cathode-ray tube is reflected into both eyes of the user by an optical system having a semi-permeable mirror. The disadvantage of this device arises from that the TV picture and the background behind the mirror are superimposed on the semi-permeable mirror arranged in front of the eye, which is disturbing and, on the other hand, the semi-permeable mirror causes a light-loss of about 50%.
A common drawback of all the above-mentioned known head worn TV image display devices is the strange appearance; they are relatively bulky and cumbersome as compared with a pair of glasses, and attract attention among people.
It is therefore the object of this invention to provide a small, light weight and compact head worn image display device, particularly a TV image display device, by means of which an image or screen can be viewed with both eyes without any loss of light intensity caused by a semi-permeable mirror. Preferably, the device should be suitable for being fixed to ordinary spectacles and carried together.
The invention is based on the recognition that an image or screen of small size placed between the two eyes in front of the nose or the middle of the forehead can be made visible for both eyes if the light rays starting from the image or screen are reflected in two directions by means of dividing mirrors fixed sufficiently distant from said image or screen, in other words the light beam--light path--starting from the screen is split into two part-beams (branches), and then said part-beams are reflected to the eyes by means of further mirrors. (The dividing mirrors--two mirrors--are preferably placed side by side forming an angle of 90.degree..+-.35.degree. with each other.) If the dividing mirrors, having expediently about the same size as the image or screen has, are placed too close to the image or screen, the image--because it is seen excessively from the side--is deformed into a trapezium, and even in opposite manner for the two eyes. Although the human brain can compensate the deformed images to a certain extent and therefore perceive them as a single image, this is, however, tiring for a long time and straining the eyes, and beyond a certain limit the two images cannot be united. It has been found advantageous if the angle of dividing the light paths does not exceed 15.degree.. (This angle corresponds to the angle of "comparison" of the optical axes of the eyes when reading a book held at a distance of
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patent: 4021846 (1977-05-01), Roese
patent: 5299063 (1994-03-01), Fritz et al.
patent: 5392158 (1995-02-01), Tosaki
patent: 5418584 (1995-05-01), Larson
patent: 5477385 (1995-12-01), Freeman
Holakovszky Laszlo
Kezi Laszlo
Nagykalnai Endre
Luu Matthew
Tung Kee M.
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