Optical: systems and elements – Single channel simultaneously to or from plural channels
Reexamination Certificate
2003-04-01
2004-09-28
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
C359S202100
Reexamination Certificate
active
06798575
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scanning type display optical system displaying an image by scanning light.
2. Description of the Related Art
A lot of image display apparatuses each apparatus, modulates light by a two-dimensional light modulation device such as a liquid crystal panel, and enlarges and projects the modulated light transmitted through or reflected by the light modulation device on a screen through an optical system, are proposed.
On the other hand, scanning image display apparatuses which displays an image on a screen by scanning a light beam or light beams at high speed, is proposed.
This scanning type image display apparatus can display an image with high color reproducibility in high resolution by using light sources with high directivity such as lasers and selecting appropriate wavelength regions of light beams emitted from the light sources.
Japanese Patent Laid-Open No. 1990-25831, and Japanese Patent Laid-Open No. 1995-168123, propose their specific structure.
In addition, as a scanning type image display apparatus, as proposed in Japanese Patent Laid-Open No. 2001-194617, there is an apparatus that makes an image observable by scanning a light beam in observer's eyes (his/her retinas).
FIG. 13
shows the structure of the scanning image type display apparatus proposed in the above-described Japanese Patent Laid-Open No. 1995-168123. In this figure, light beams
412
,
422
, and
432
that have three different wavelength regions and are emitted from rare gas laser sources
410
,
420
, and
430
are modulated respectively by modulators
414
,
424
, and
434
, and are combined by dichroic mirrors
416
, and
426
. A combined beam
440
is scanned on a screen
454
in a two-dimensional direction by optical scanning mirrors
444
and
446
, and forms a color image on the screen
454
.
FIG. 14
shows the structure of an apparatus proposed in the above-described Japanese Patent Laid-Open No. 1990-25831. In this figure, reference numeral
510
shows a He—Ne laser light source and reference numeral
520
shows an Ar laser light source. A light beam in a red system from the He—Ne laser source
510
is modulated by an optical modulator
513
. In addition, a light beam from the Ar laser light source
520
is split into a green component and a blue component by a beam splitting element
522
. And the green and blue components are modulated respectively by different optical modulators
525
and
533
.
Thereafter, these three color beams are combined by the dichroic mirrors
528
and
536
, and the combined beam enters into a scanning optical system
504
. The scanning optical system
504
scans the combined beam two-dimensionally by optical scanning mirrors
542
and
545
, and displays a color image on a screen
547
.
FIGS.
15
(A) and
15
(B) show the structure of an optical system that is applied to a head-mounted image display apparatus, proposed in Japanese Patent Laid-Open No. 2001-194617. FIG.
15
(A) shows the outline of the optical system, where a light flux from a light source
614
is reflected on a reflecting surface
628
of a prismatic optical system
632
and enters into a scanning mirror
613
after passing through a surface
624
of the prismatic optical system. The scanning mirror
613
scans the incident light. The scanned light enters into the prismatic optical system
632
again, and is reflected on a plurality of surfaces to be emitted from a surface
621
to observer's pupils
611
.
In addition, though the light source
614
is shown like one light source in FIG.
15
(A), a dichroic prism
614
′ that is a color combining element shown in FIG.
15
(B) is actually arranged. Owing to this, three colors of light from light sources
651
R,
651
G, and
651
B corresponding to red, green, and blue are combined by the dichroic prism
614
′, and the combined light is emitted toward the prismatic optical system
632
.
Nevertheless, since each color combining system in the optical systems proposed in the above-described Japanese Patent Laid-Open No. 1995-168123 and Japanese Patent Laid-Open No. 1990-25831 is formed by combining and arranging a plurality of dichroic mirrors, an optical path route becomes large so that the entire optical system is enlarged. In addition, structure of the color combining system becomes complex since there are a lot of parts.
In addition, though it is possible to miniaturize the optical system, proposed in the above-described Japanese Patent Laid-Open No. 2001-194617, in some measure by using a dichroic prism, in general, the dichroic prism is expensive. Furthermore, since three color light beams are combined by reflective and transmissive actions to a plurality of dichroic surfaces, a shape of the prism becomes complex and it becomes easy to cause displacement of the color light beams on a scan surface.
BRIEF SUMMARY OF THE INVENTION
The present invention aims to provide a scanning type display optical system that can reduce the number of parts and can achieve miniaturization.
In order to achieve the above-described object, the scanning type display optical system according to the present invention includes a plurality of light sources emitting light having wavelength regions mutually different, a light combining element combining the light from the plurality of light sources, and a scanning optical system scanning the light, combined by the light combining element on a scan surface. Then, it is made that the light combining element is a diffraction optical element.
The features of the present invention will become clear by the explanation of the following specific embodiments with referring to drawings.
REFERENCES:
patent: 5027359 (1991-06-01), Leger et al.
patent: 5892556 (1999-04-01), Deter
patent: 6542245 (2003-04-01), Toida
patent: 2-25831 (1990-01-01), None
patent: 7-168123 (1995-07-01), None
patent: 2001-194617 (2001-07-01), None
Canon Kabushiki Kaisha
Mack Ricky
Morgan & Finnegan , LLP
LandOfFree
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