Computer graphics processing and selective visual display system – Image superposition by optical means – Operator body-mounted heads-up display
Reexamination Certificate
1999-05-28
2002-05-28
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Image superposition by optical means
Operator body-mounted heads-up display
C345S007000, C345S009000, C345S032000, C359S013000, C359S015000, C359S019000, C359S020000, C359S022000, C359S027000, C348S051000, C348S053000, C348S115000
Reexamination Certificate
active
06396463
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image projection apparatus for projecting a high-definition picture image in a wide angle of view onto a retina.
2. Description of the Related Art
Hitherto, this kind of apparatus has been designed so as to become small and thin so that it can be used while being mounted on a human head. As an example, Japanese Patent Unexamined Publication No. Hei. 2-136818 discloses an image display apparatus. This apparatus is such that a picture image displayed on a display element is made to bypass an optical system of an eye of an observer, so that it is directly projected on a retina. Thus, in this apparatus, it is possible to observe an image in an angle of view corresponding to a converging angle of a lens. According to this method, it is not necessary to add a function such as diopter adjustment to the optical system. This apparatus is specifically constituted by a point light source such as a midget lamp, a picture image panel irradiated by this point light source, and a short focus convex lens integrated with this picture image panel. In this apparatus, an image on the picture image panel illuminated with light from the point light source is brought into focus at a pupil positioned in an eyeball lens. This focus is a light source image and becomes a diffraction image plane of the picture image displayed on the display element. This point is made a pinhole, and the picture image on the display element is directly projected on the retina. In this apparatus, although it is possible to observe an image in an angle of view corresponding to a converging angle, large aberration occurs in the case where only one short focus lens is used, so that it is impossible to observe a high-definition picture image.
An image display apparatus improving this point is disclosed in, for example, Japanese Patent Unexamined Publication No. Hei. 4-23579 (or U.S. Pat. No. 5,371,556). This apparatus is constituted by an illuminating lens for illuminating a picture image panel, and an objective lens for projecting a picture image of a display element onto a retina. Specifically, after an angle of divergence of a beam of light from a midget lamp (point light source) is once controlled by a lens, the direction of the beam of light is changed by two mirrors, and then, the beam is made a parallel beam by a convex lens to illuminate an LCD panel. The direction of the beam of light is controlled by a convex lens disposed immediately after the LCD panel and the picture image beam of light is condensed by a short focus convex lens. An image of the point light source is formed on the pupil of an observer, so that the picture image of the display element is projected on the retina of the observer.
Japanese Patent Unexamined Publication No. Hei. 5-328261 (or U.S. Pat. No. 5,499,138) discloses another improved image display apparatus. In this apparatus, a two-dimensional microlens array is disposed on a display element, and an image of a pixel formed there is formed on a retina. Specifically, the two-dimensional microlens array is disposed on a transmission liquid crystal display element illuminated by a two-dimensional LED array or surface light source, and an outgoing beam of light from each pixel of the display element is converted into a parallel beam of light by a condenser lens and is led into an eyeball. In this apparatus, since an image corresponding to each pixel is formed on the retina by the lens action of the eyeball, a clear image can be obtained.
On the other hand, U.S. Pat. No. 4,309,070 discloses a display apparatus using a large-off axis hologram optical element to miniaturize a display apparatus of a beam combiner. In this apparatus, a beam of light of a picture image displayed on a screen of a CRT is converted into a collimated beam of light through a lens, is incident from an end surface of a transparent substrate, is reflected in the substrate, and is diffracted by the hologram. Although an observer observes a virtual image, the observer can observe the outside at the same time through the transparent substrate and the hologram.
Among the related art, in the apparatus using the illuminating lens and the objective lens, as compared with an apparatus including only one short focus lens, an image with high resolution can be obtained. However, there has been a problem that the resolution is influenced by the size of the light source. Besides, in the apparatus using the illuminating lens and the objective lens, although it is possible to observe an image in a wide angle of view, at least two lenses are required and the optical system becomes complicated. Actually, for the purpose of correcting (color) aberration and spherical aberration, a combination lens of at least four lenses is required. Basically, the lens is used in a coaxial optical system. In order to prevent the size of the apparatus from increasing, contrivance of use with folding at a mirror is adopted. However, the number of optical parts becomes eight, and it has been difficult to miniaturize the apparatus any more.
In the apparatus using the two-dimensional microlens array, as compared with an apparatus of using only one short focus lens, an image corresponding to each pixel is obtained, so that clear display can be obtained. However, an optimum pixel size and a pixel pitch obtained from calculation are 6.5 &mgr;m square and 185×184 &mgr;m. That is, although the pixel size is small, the pixel pitch is large. For the purpose of obtaining high resolution, a display element of a large screen becomes necessary, and the increase of the size of the apparatus can not be avoided. Even if a large angle of view is obtained, since parallel beams of light are led into the eye and the optical system of the eye is used, the merit that the optical system of the eye can be bypassed is lost differently from the structure of the apparatus using only one short focus lens.
In the apparatus using one short focus lens or the illuminating lens and the objective lens, when the movement (direction of line of sight) of the eye of the observer and the mounting position of the apparatus are changed, distortion occurs in the image formed on the retina. The reason is that although the picture image panel and the retina are in conjugate relation through the large pinhole of the pupil, when the position of the line of sight and the apparatus is shifted, the lens function of the eyeball contributes. In order to solve this problem, such contrivance has been made that a focal position is controlled by a mechanical deviation so that the focal position at the rear side of the short focus convex lens comes to the center of the eyeball lens. However, the increase in the size of the apparatus itself can not be avoided also in this case.
On the other hand, the apparatus using the large-off axis hologram has been proposed for miniaturizing a beam combiner display apparatus. However, when a virtual image of the CRT image is observed, the position of the virtual image and the size thereof are limited. Particularly, since the light path difference between the display and the large-off axis hologram optical element is greatly changed according to the position by the large-off axis, aberration becomes apt to occur. Like this, although this apparatus can be made compact, there are problems that an angle of view is narrow and the resolution becomes low.
From the above, the problem of an image projection apparatus is to realize such an apparatus that
1) the apparatus is miniaturized (including a decrease in the number of parts) while maintaining high resolution and a wide angle of view,
2) the outside can be perceived at the same time, and
3) distortion does not occur on the retina image by a small shift at the time of mounting, and so on.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide an image projection apparatus which is small and in which a picture image can be stably observed while high resolution is maintained. Another object of the present invention i
Fuji 'Xerox Co., Ltd.
Hjerpe Richard
Oliff & Berridg,e PLC
Tran Henry N.
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