Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Combined
Patent
1995-06-22
1998-04-14
Dang, Hung X.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Combined
G02C 100
Patent
active
057398933
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to an image display apparatus for virtual enlargement and viewing 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 flames 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
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Ishizawa Shoichi
Karasawa Joji
Miyazawa Yoko
Uchiyama Shoichi
Dang Hung X.
Seiko Epson Corporation
Watson Mark P.
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