Computer graphics processing and selective visual display system – Image superposition by optical means – Operator body-mounted heads-up display
Reexamination Certificate
2000-04-12
2003-03-25
Lao, Lun-Yi (Department: 2774)
Computer graphics processing and selective visual display system
Image superposition by optical means
Operator body-mounted heads-up display
C345S009000, C359S631000, C359S632000, C351S158000
Reexamination Certificate
active
06538624
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image display apparatus for virtual enlargement and viewing of images displayed by an image display means, and relates particularly to a head-mounted image display apparatus for viewing images with the display apparatus itself worn on the head.
2. Description of the Related Art
An apparatus which is worn on the head for viewing images is described, for example, in Japanese patent laid-open number 1993-100192. This apparatus comprises an eyeglasses-type frame which is worn on the head similarly to eyeglasses. As frequently experienced by eyeglasses users, fatigue and discomfort can occur in the nose and ears where the apparatus touches due to a slight increase in weight, and the functionality that can be provided in the image display apparatus and the viewing time are therefore limited. In addition, the apparatus may shift when the head or body is moved because the method of mounting on the head is unstable, and it is therefore not possible to view the images in a stable condition. Moreover, when the head or body is moved greatly, the apparatus may fall from the head and break.
With the head-mounted image display apparatus described in Japanese patent laid-open number 1992-22358, a pair of side frames extending to the sides of the head is provided on the apparatus, and the apparatus is mounted to the head by connecting the ends of these side frames with an elastic band and wrapping the side frames around the head. However, while this method prevents the apparatus from falling off the head by means of the elastic band, its effectiveness preventing the apparatus from falling off is insufficient because of the narrow width of the elastic band. Furthermore, even if the width of the elastic band is increased, there is still no change in the instability of the apparatus insofar as it is held only by an elastic band, and problems such as image blurring, fatigue, and discomfort remain.
Thus, the first problem with this conventional head-mounted image display apparatus is the poor user comfort resulting from the part to which the apparatus is mounted being the head, which varies in size and shape from person to person, and the difficulty of mounting the apparatus in a stable manner on the head.
Next, because the head-mounted image display apparatus is for personal use, it is possible to adjust the image display conditions according to the visual acuity and pupil distance (of the user) with the head-mounted image display apparatus described in Nikkei Electronics, No. 571, p. 119. However, this head-mounted image display apparatus is constructed to illuminate a pair of left and right optical units, each comprising a liquid crystal light valve, reflecting mirror, and enlarging lens, using one backlight, and the user experience is therefore poor. More specifically, if only the liquid crystal light valve, which is formed separately to the backlight, is moved along the optical axis of the optical unit to change the distance between the backlight and the liquid crystal light valve when the imaging position is adjusted according to the visual acuity of the user, illumination of the liquid crystal light valve also changes because divergent light is irradiated from the fluorescent tube used as the backlight, and image quality deteriorates. In particular, the right and left virtual images (luminance) will differ if the visual acuity of the user differs between the right and left eyes, and this will be a cause of asthenopia. Moreover, as the distance between the backlight and the liquid crystal light valve increases, the lighting efficiency of the backlight decreases, increasing the brightness of the image is inhibited, and attempts to overcome this become a hindrance to achieving low power consumption.
Furthermore, there are individual differences in the pupil distance, which is generally considered to be in the range of approximately 58 mm to approximately 72 mm. As a result, it is necessary for the right and left optical units to have a range of relative movement of approximately 14 mm. However, if this type of adjustment is performed separately for the right and left optical units in the conventional head-mounted image display apparatus, each eye must be separately adjusted, and more time is required. It is also possible that while this relative distance is acceptable, one of the optical units has moved too far, and use in this condition can lead to asthenopia.
With the head-mounted image display apparatus described in Japanese patent laid-open number 1993-48991, the optical axis formed by the image display apparatus, the enlargement optics, and the eye will be on the horizontal visual axis of the eye. As a result, because the viewer must view the images with the visual axis fixed in the horizontal direction, the eyelids feel forced open, the eyes and eyelids feel burdened, and this condition can lead to asthenopia if it continues for long.
The second problem is therefore the poor user comfort resulting from these conventional apparatuses not giving sufficient consideration to the characteristics of visual appreciation of information
Another head-mounted image display apparatus is described in U.S. Pat. No. 5,162,828, and others; this apparatus provides an image display element, enlargement optics for the image displayed thereby, and a holding means for positioning the enlargement optics and display element in front of the eyes of the viewer. Of these component parts, the display element has the greatest structural influence on the other parts, and is an important component; because compactness, light weight, and low power consumption are generally required in this display element, liquid crystal display elements of minimum three inches diagonally or liquid crystal display elements of a maximum one inch diagonally are used. However, major problems may result if the liquid crystal display element is either too large or too small.
First, when the liquid crystal display element is too large, the display element itself not only becomes large, the enlargement optics for enlarging and displaying the image also increase in size. As a result, the head-mounted image display apparatus becomes extremely bulky and heavy, greatly burdening the viewer. Problems relating to addressing the liquid crystal display element also occur. Specifically, because the liquid crystal display element modules are too large in the right and left optical units, they hit each other if placed in front of the eyes, and the center of the image display plane cannot be placed on the optical axis connecting the eye and the enlargement lens. In this case, the position occupied by the enlarged image is different in the viewer's right and left visual fields, and when the brain attempts to join the right and left images when viewing television or video, the images will not completely coincide. In addition, to be recognized as a single image, it is necessary to display different images in the right and left liquid crystal display modules, making it necessary to add the circuitry and other components needed to divide and display the source image in the right and left liquid crystal display modules. The resulting problem is that it is not possible to achieve a compact, lightweight, and low cost head-mounted image display apparatus.
On the other hand, it is not possible to improve the image quality when the liquid crystal display element is too small. To improve image quality in the liquid crystal display module, it is necessary to increase the number of picture elements in the liquid crystal display element. With respect to this, however, the picture elements must be made smaller if the same number of picture elements used in the large size liquid crystal display element is to be used because the display area is small in a compact liquid crystal display element. More specifically, if the size of the liquid crystal display element is ½, the picture element size also becomes ½. Therefore, if a clear enlarged display image is to be obtained
Ishizawa Shoichi
Karasawa Joji
Miyazawa Yoko
Uchiyama Shoichi
Lao Lun-Yi
Seiko Epson Corporation
Watson Mark P.
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