Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2001-12-21
2003-12-02
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S208100
Reexamination Certificate
active
06657763
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image display apparatus for displaying an image formed by scanning a beam from a light source and, more particularly, to an image display apparatus suitable for scanning a beam by driving a reflecting surface using mechanical resonance.
2. Related Background Art
Various proposals including U.S. Pat. Nos. 5,355,181, 5,369,415, and 5,467,104, and Japanese Patent No. 2,874,208 have been made as an image display optical system (or image display apparatus) for forming an image on the observer's eye (retina) by scanning a beam from a light source.
FIG. 9
shows the arrangement of an image display optical system disclosed in U.S. Pat. No. 5,355,181. In this image display optical system, a beam from a light source
300
is modulated by an optical modulator
301
, enters horizontal and vertical optical deflectors
304
and
305
via optical systems
302
and
303
, and reaches an eye
310
via an eyepiece optical system
306
which constitutes a telescope system. The optical deflectors
304
and
305
deflect light incident on the eye
310
and scan an image formed on the retina. This allows the observer to observe a two-dimensional image.
FIG. 10
shows the arrangement of an image display optical system disclosed in U.S. Pat. No. 5,369,415. In this image display optical system, a two-dimensionally scanned beam from a light source
401
scans an eye (retina)
410
via a planar optical system
402
. The beam to be scanned is sequentially reflected at a plurality of planar reflecting points within the planar optical system
402
, and its optical path is changed toward the eye by a diffraction optical system
403
. With this arrangement, the diffracted beam directly scans the retina
410
to enable observing an image.
FIG. 11
shows the arrangement of an image display optical system disclosed in U.S. Pat. No. 5,467,104. In this image display optical system, red, green, and blue light sources
501
,
502
, and
503
are modulated by light source drivers
504
,
505
, and
506
, and beams from these light sources are combined by a color combining means
507
. The combined beam from the light sources passes through the pupil of an eye
510
via an optical system interposed between the color combining means
507
and the eye
510
, and is guided on the retina. Vertical and horizontal scanning means
508
and
509
are arranged between the eye and the light sources via an optical system, and scan the beam on the retina.
FIGS. 12A and 12B
show the arrangement of an image display optical system disclosed in Japanese Patent No. 2,874,208. As shown in
FIG. 12B
, a beam from a light source is deflected by a deflection means
602
comprising a polygon mirror, and enters an eye
610
via optical systems
601
b
and
601
c
.
FIG. 12A
shows an arrangement on the optical path from the light source to the eye. Beams from light sources
603
,
604
, and
605
driven by a data processing and drive signal
620
enter an optical fiber
618
via collimator lenses
606
, color combining systems
607
, and a lens
609
. After passing through the optical fiber
618
, the beam further passes through a wavefront curvature modulator
630
and beam deflector
640
via a lens
619
, and reaches the eye
610
.
These conventional image display optical systems display a two-dimensional image to the observer by forming light from a light source into an image on the retina serving as an image plane and scanning the image point by a scanning means inserted in the optical path.
An apparatus for displaying a two-dimensional image to the observer is, e.g., a liquid crystal panel which enlarges and displays a two-dimensional image as a virtual image via an optical system. To display a finer image, this arrangement requires a larger number of pixels of the image display element. However, a small-size image display element with many pixels is high in cost, increasing the cost of the whole apparatus.
Of the scanning image display apparatuses described above, those disclosed in U.S. Pat. Nos. 5,355,181 and 5,467,104 and Japanese Patent No. 2,874,208 use many lenses, which readily makes the optical system or apparatus bulky.
The image display apparatus disclosed in U.S. Pat. No. 5,369,415 has a relatively simpler arrangement using a flat optical system. However, light is diffracted to the observer's eye by only the diffraction optical element in front of the eye, so aberration may become difficult to correct for high image quality. Thus, the field angle is difficult to increase.
Japanese Patent No. 2,874,208 adopts a polygon mirror as a deflection (scanning) means, and the deflection means and whole apparatus become bulky.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a small-size, low-cost scanning image display apparatus with a simple arrangement that realizes high-speed beam scan.
To achieve the above object, an image display apparatus according to the present invention comprises scanning unit for scanning a beam by driving a reflecting surface for reflecting a beam from the light source part, an optical element having an incident surface which the reflected beam from the scanning unit enters, at least one inner reflecting surface which has a curved surface and reflects the beam coming from the incident surface, and an exit surface from which the beam reflected by the inner reflecting surface emerges, and a reflecting element for reflecting the beam emerging from the optical element and guiding the beam to an observer's eye.
Since a beam emitted by the light source unit is scanned by the scanning unit, the prevent invention can provide an image display apparatus which can easily increase the scanning speed and is suitable for displaying a fine image.
The use of the optical element with at least one inner reflecting surface enables deflecting the optical path and easily downsizing the apparatus. Since a beam emitted by the optical element is guided to the eyeball via the reflecting element, the degree of freedom for the layout of the optical system can be increased.
For example, the scanning unit and optical element are arranged on the side of the head with respect to the reflecting element positioned in front of the observer's eye so as to prevent the observer from feeling uncomfortable. The present invention can implement a scanning image display apparatus which can be used comfortably as if the observer wore glasses.
The inner reflecting surface of the optical element is formed into a curved surface. This structure can satisfactorily correct aberrations such as decentering aberration which readily occur owing to an optical layout capable of guiding a beam from the side of the head to the eyeball via the reflecting element in front of the eye. Accordingly, a high-quality image can be displayed.
The scanning unit is a device which utilizes an MEMS (Micro Electro Mechanical System) technique, is manufactured by a semiconductor process, and has a reflecting surface driven by mechanical resonance. The scanning unit itself can be downsized, scanning can be done at a very high speed, and a smaller-size image display apparatus capable of displaying a fine image can be implemented.
If the beam scanning angle of the scanning unit is enlarged by an optical system made up of an optical element and reflecting element, an image larger than the scanning angle of the scanning unit can be observed.
REFERENCES:
patent: 5355181 (1994-10-01), Ashizaki et al.
patent: 5369415 (1994-11-01), Richard et al.
patent: 5467104 (1995-11-01), Furness III et al.
patent: 6081304 (2000-06-01), Kuriyama et al.
patent: 6333820 (2001-12-01), Hayakawa et al.
patent: 392811 (2002-05-01), Lindau
patent: 2874208 (1999-01-01), None
patent: 11-125791 (1999-05-01), None
patent: 2001-004955 (2001-01-01), None
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