Two-dimensional scanning apparatus and scanning type image displaying apparatus using the same Number:7,385,745 from the United States Patent and Trademark Office (PTO) owispatent The invention is to provide an optical scanning apparatus which scans light from a light source onto a surface to be scanned, comprising a light scanning optical system having at least one reflecting surface of non-rotation symmetrical shape, and guiding a deflected beam two-dimensionally deflected by a deflection optical system onto the surface to be scanned by using the one reflecting surface of non-rotation symmetrical shape, wherein a principal ray of a beam incident onto the center of an angle of view of the surface to be scanned is made inclined incident onto the surface to be scanned in the first scanning direction.<H dimensional, displaying, Two, dimensional, 7385745.html, Patent, pto, 7385745

Title: Two-dimensional scanning apparatus and scanning type image displaying apparatus using the same

Abstract: The invention is to provide an optical scanning apparatus which scans light from a light source onto a surface to be scanned, comprising a light scanning optical system having at least one reflecting surface of non-rotation symmetrical shape, and guiding a deflected beam two-dimensionally deflected by a deflection optical system onto the surface to be scanned by using the one reflecting surface of non-rotation symmetrical shape, wherein a principal ray of a beam incident onto the center of an angle of view of the surface to be scanned is made inclined incident onto the surface to be scanned in the first scanning direction.

Patent Number: 7,385,745 Issued on 06/10/2008 to Ishihara

Inventors: Ishihara; Keiichiro (Kanagawa-ken, JP)
Assignee: Canon Kabushiki Kaisha (Tokyo, JP)

Appl. No.: 11/061,929

Filed: February 18, 2005

Foreign Application Priority Data


Feb 19, 2004 [JP]			2004-042278

Current U.S. Class: 359/202 ; 359/205; 359/207; 359/208

Field of Search: 359/202

References Cited [Referenced By]

U.S. Patent Documents


4003080	January 1977	Maiman et al.
5025268	June 1991	Arimoto et al.
5359434	October 1994	Nakao et al.
5625613	April 1997	Kato et al.
6211988	April 2001	Engelhardt et al.
6282008	August 2001	Togino
6657763	December 2003	Kobayashi
2002/0125325	September 2002	Plesko
2003/0030897	February 2003	Suzuki
2004/0196571	October 2004	Shinohara

Foreign Patent Documents


19860017	Jun., 2000	DE
1291681	Mar., 2003	EP
1291681	Mar., 2003	EP
1450558	Aug., 2004	EP
5-127091	May., 1993	JP
5-208523	Aug., 1993	JP
5-289011	Nov., 1993	JP
6-246839	Sep., 1994	JP
6-294924	Oct., 1994	JP
7-234382	Sep., 1995	JP
9-80335	Mar., 1997	JP
11-84291	Mar., 1999	JP
11-101948	Apr., 1999	JP
11-119106	Apr., 1999	JP
11-149128	Jun., 1999	JP
11-267873	Oct., 1999	JP
2000-36085	Feb., 2000	JP
2001-281583	Oct., 2001	JP
2003-57554	Feb., 2003	JP
2003-149577	May., 2003	JP
2004252012	Sep., 2004	JP
2004341411	Dec., 2004	JP

Other References

"High-Resolution, Wide-Aspect, and Wide-Viewing Displays on DELL Portable Computers", May 2003, Dell's White Paper, pp. 1-5. cited by examiner .
European Search Report of EP Application No. EP05250975--Date of Completion of Search--Jun. 28, 2006. cited by other.

Primary Examiner: Stultz; Jessica T
Attorney, Agent or Firm: Morgan & Finnegan, L.L.P.

Claims

What is claimed is:

1. A two-dimensional scanning apparatus comprising: deflecting means for deflecting a beam emitted from light source means in a first scanning direction and a second scanning direction orthogonal to said first scanning direction; and a scanning optical system including, in order from the deflecting means, a first reflecting surface and a second reflecting surface, the first and second reflecting surfaces having rotationally asymmetrical shapes, and directing the deflected beam deflected by said deflecting means onto a surface to be scanned, said first and second reflecting surfaces being disposed so as to fold an optical path of said deflected beam in said first scanning direction; wherein a principal ray of a beam incident on the center of an angle of view of said surface to be scanned is inclined incident on said surface to be scanned in at least the first scanning direction of said first and second scanning directions, and wherein when the principal ray is set as a reference axis, said first scanning direction is in parallel with a plane containing the reference axis, wherein the first reflecting surface includes a first concave surface of which shape in a section in parallel with said second scanning direction is concave, and a first convex surface of which shape in a section in parallel with said second scanning direction is convex, wherein the second reflecting surface includes a second concave surface of which shape in a section in parallel with said second scanning direction is concave, and a second convex surface of which shape in a section in parallel with said second scanning direction is convex, wherein the beam emitted from the first concave surface is incident into said surface to be scanned through the second convex surface, and wherein the beam emitted from the first convex surface is incident into said surface to be scanned through the second concave surface.

2. A two-dimensional scanning apparatus according to claim 1, wherein the beam emitted from said light source means is made obliquely incident from said first scanning direction onto a deflecting surface of said deflecting means.

3. A two-dimensional scanning apparatus according to claim 2, wherein when in said first scanning direction, it is viewed in the optical path from said deflecting means to said scanning optical system, the beam emitted from said light source means is made obliquely incident from a side on which a deflected beam having a small incidence angle onto the surface to be scanned passes onto the deflecting surface of said deflecting means.

4. A two-dimensional scanning apparatus according to claim 1, wherein said scanning optical system has negative power as a whole, and a convergent beam having a natural converging point between said deflecting means and said surface to be scanned is condensed near said surface to be scanned by said scanning optical system.

5. A two-dimensional scanning apparatus according to claim 1, wherein a pupil of said scanning optical system is disposed near said deflecting means to thereby form a virtual image of said pupil.

6. A two-dimensional scanning apparatus according to claim 1, wherein said scanning optical system has a prism including at least two reflecting surfaces of a non-rotation symmetrical shape.

7. A two-dimensional scanning apparatus according to claim 1, wherein when an angle of view in said first scanning direction is defined as .theta.d1, and an angle of view in said second scanning direction is defined as .theta.d2, and a width of the beam incident on said surface to be scanned in said first scanning direction is defined as Wi1, and the width thereof in said second scanning direction is defined as Wi2, a condition that .times..times..times..times..times.<.theta..times..times..times..times- ..theta..times..times..times..times.<.times..times..times..times..times- . ##EQU00009## be satisfied.

8. A two-dimensional scanning apparatus according to claim 1, wherein when a width of said scanning optical system in said second scanning direction is defined as Dx, and the width thereof in said first scanning direction is defined as Dy, and the width thereof in the direction of the Z-axis perpendicular to a horizontal scanning direction and a vertical scanning direction is defined as Dz, conditions that Dx.ltoreq.40 (mm) Dy.ltoreq.30 (mm) Dz.ltoreq.35 (mm) be satisfied.

9. A two-dimensional scanning apparatus according to claim 1, wherein said light source means emits a plurality of beams of different wavelengths.

10. A two-dimensional scanning apparatus according to claim 1, wherein said light source means has a light emitting element capable of effecting light modulation.

11. A scanning type image displaying apparatus comprising: light source means; and a two-dimensional scanning apparatus according to claim 1 for forming an image on said surface to be scanned by the use of light from said light source means.

12. A two-dimensional scanning apparatus in accordance with claim 1, wherein a beam, of which incident angle with respect to said surface to be scanned is larger than that of the principal ray with respect to said surface to be scanned, is incident into said surface to be scanned through the first convex surface and the second concave surface, and a beam, of which incident angle with respect to said surface to be scanned is smaller than that of the principal ray with respect to said surface to be scanned, is incident into said surface to be scanned through the first concave surface and the second convex surface.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a two-dimensional scanning apparatus and a scanning type image displaying apparatus using the same, and particularly is adapted to two-dimensionally scan a beam (deflected beam) deflected by deflecting means to thereby project and display a two-dimensional image on a surface to be scanned (a screen surface).

2. Related Background Art

There have been proposed various two-dimensional scanning apparatuses which two-dimensionally deflect a beam emitted from light source means by deflecting means, two-dimensionally optically scan on a surface to be scanned by a spot, and form a two-dimensional image by the afterimage effect thereof (see, for example, Japanese Patent Application Laid-open No. H11-084291 and Japanese Patent Application Laid-open No. 2001-281583).

Now, it is known that by a beam being two-dimensionally deflected and scanned, so-called distortion occurs to a two-dimensional image on a surface to be scanned. The distortion includes trapezoid distortion, distortion of a uniform speed scanning property, distortion of a rectilinear scanning property and further, TV distortion which refers to the curving of the frame of an image depicted on the surface to be scanned.

In Japanese Patent Application Laid-open No. H11-084291 and Japanese Patent Application Laid-open No. 2001-281583, there is disclosed a two-dimensional scanning apparatus using an optical element including a refracting surface and a reflecting surface, and adapted to turn back an optical path in the interior of the optical element (prism member), and in which in order to correct eccentric aberration, the refracting surface or the reflecting surface is constituted by a non-rotation symmetric surface having no rotation symmetry axis either inside or outside the surface.

This is a two-dimensional scanning apparatus constituted by the use of an optical element, and yet well corrects uniform velocity property of scanning light on the surface to be scanned over a wide scanning angle. It can also achieve telecentricity necessary for highly accurate image depiction.

However, the two-dimensional scanning apparatus disclosed in Japanese Patent Application Laid-open No. H11-084291 and Japanese Patent Application Laid-open No. 2001-281583 does not at all correct TV distortion. Further, when an image has been obliquely projected onto a surface to be scanned such as a screen, trapezoid distortion has occurred to thereby deteriorate the dignity of the image, the two-dimensional scanning apparatus disclosed in Japanese Patent Application Laid-Open No. H11-084291 and Japanese Patent Application Laid-open No. 2001-281583 neither correct trapezoid distortion.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a two-dimensional scanning apparatus which can well correct TV distortion caused by a beam being two-dimensionally deflected by deflecting means and trapezoid distortion caused by an image being obliquely projected onto a surface to be scanned. It is a further object of the present invention to provide a two-dimensional scanning apparatus in which a scanning optical system can be downsized and chromatic aberration does not occur, and a scanning type image displaying apparatus using the same.

In order to solve the above-noted problem, a two-dimensional scanning apparatus according to the present invention is provided with:

deflecting means for deflecting a beam emitted from light source means in a first scanning direction and a second scanning direction orthogonal to the first scanning direction; and

a scanning optical system for directing the deflected beam deflected by the deflecting means onto a surface to be scanned;

wherein the principal ray of the beam incident on the center of the angle of view of the surface to be scanned is incident obliquely with respect to the surface to be scanned, in at least the first scanning direction of the first and second scanning directions, and

the scanning optical system has at least two reflecting surfaces of a non-rotation symmetrical shape, and the at least two reflecting surfaces are disposed so as to fold the optical path of the deflected beam in the first scanning direction.

In the above-described two-dimensional scanning apparatus, it is preferable that when the optical path from after the principal ray of the deflected beam is reflected by one of the at least two reflecting surfaces until it arrives at the other reflecting surface is defined as a reference axis, the shapes of the at least two reflecting surfaces be asymmetric with respect to the reference axis in the first scanning direction.

Or it is preferable that when the optical path from after the principal ray of the deflected beam is reflected by one of the at least two reflecting surfaces until it arrives at the other reflecting surface is defined as a reference axis, in a first scanning section containing the reference axis and formed by the reference axis and the first scanning direction, the at least two reflecting surfaces be curvature monotonously changing anamorphic surfaces of which the curvature in the second scanning direction in the first scanning section gradually changes from great to small or from small to great as it moves along the first scanning direction.

Also, in this case, it is more preferable that one of the at least two reflecting surfaces be convex in the shape thereof in the second scanning direction in the first scanning section, and the other reflecting surface be concave in the shape thereof in the second scanning direction in the first scanning section.

Or it is preferable that one of the at least two reflecting surfaces be such that a side thereof on which the power thereof in the second scanning direction in the first scanning section is strong as compared with the power of the other reflecting surface and a side thereof on which the power of the other reflecting surface in the second scanning direction in the first scanning section is weak as compared with the power of the other reflecting surface are arranged properly.

Also, in the above-described two-dimensional scanning apparatus, it is preferable that the beam emitted from the light source means be made incident obliquely from the first scanning direction onto the deflecting surface of the deflecting means.

Further, in this case, it is preferable that when in the first scanning direction, it is viewed in an optical path from the deflecting means to the scanning optical system, the beam emitted from the light source means be made obliquely incident from a side on which a deflected beam small in the incidence angle onto the surface to be scanned passes onto the deflecting surface of the deflecting means.

Also, in the above-described two-dimensional scanning apparatus, it is preferable that the scanning optical system have negative power as a whole, and a convergent beam having a natural converging point between the deflecting means and the surface to be scanned be condensed near the surface to be scanned by the scanning optical system.

Also, in the above-described two-dimensional scanning apparatus, it is preferable that the pupil of the scanning optical system be disposed near the deflecting means to thereby form the virtual image of the pupil.

Also, in the above-described two-dimensional scanning apparatus, it is preferable that the scanning optical system have two reflecting surfaces of a non-rotation symmetrical shape.

Also, in the above-described two-dimensional scanning apparatus, it is preferable that the scanning optical system have a prism including at least two reflecting surfaces of a non-rotation symmetrical shape.

Also, in the above-described two-dimensional scanning apparatus, it is preferable that when an angle of view in the first scanning direction is defined as .theta.d1, and an angle of view in the second scanning direction is defined as .theta.d2, and a width of the beam incident on the surface to be scanned in the first scanning direction is defined as Wi1, and the width thereof in the second scanning direction is defined as Wi2, a condition that

.times.<.theta..times..times.d.theta..times..times.d<.times. ##EQU00001## be satisfied.

Also, in the above-described two-dimensional scanning apparatus, it is preferable that when the width of the scanning optical system in the second scanning direction is defined as Dx, and the width thereof in the first scanning direction is defined as Dy, and the width thereof in the Z-axis direction perpendicular to a horizontal scanning direction and a vertical scanning direction is defined as Dz, conditions that Dx.ltoreq.40 (mm) Dy.ltoreq.30 (mm) Dz.ltoreq.35 (mm) be satisfied.

Also, in the above-described two-dimensional scanning apparatus, it is preferable that the light source means emit a plurality of beams of different wavelengths.

Also, in the above-described two-dimensional scanning apparatus, it is preferable that the light source means have a light emitting element capable of effecting light modulation.

Further, in order to solve the above-noted problem, a scanning type image displaying apparatus according to the present invention is provided with:

light source means; and

the above-described two-dimensional scanning apparatus for forming an image on the surface to be scanned by the use of light from the light source means.

In order to solve the above-noted problems, an optical scanning apparatus which is a further aspect of the present invention is provided with:

deflecting means for deflecting a beam from a light source; and

a scanning optical system for imaging the deflected beam from the deflecting means as a spot on a surface to be scanned;

wherein the scanning optical system has a scanning mirror and folds in a first scanning direction, and positions at which beams arriving at the same position on the surface to be scanned in a second scanning direction orthogonal to the first scanning direction are reflected by the scanning mirror are disposed on a straight line when viewed in the second scanning direction, and optical paths after emerging from the scanning optical system are made incident on the surface to be scanned in superposed relationship with one another.

Also, a scanning type image displaying apparatus which is a further aspect of the present invention is provided with:

a light source; and

the above-described optical scanning apparatus for displaying an image on the surface to be scanned with light from the light source.

Also, an optical scanning apparatus for scanning a surface to be scanned with light from a light source which is a further aspect of the present invention is provided with:

a deflecting optical system for deflecting a beam from light source means in a first scanning direction and a second scanning direction orthogonal to the first scanning direction; and

a scanning optical system including at least one reflecting surface of a non-rotation symmetrical shape and for directing the deflected beam deflected by the deflecting optical system onto a surface to be scanned by the use of the aforementioned at least one reflecting surface of a non-rotation symmetrical shape;

wherein the principal ray of the beam incident on the center of the angle of view of the surface to be scanned is incident while being inclined with respect to the surface to be scanned in at least the first scanning direction of the first and second scanning directions.

In the above-described optical scanning apparatus, it is preferable that the aforementioned at least one reflecting surface of a non-rotation symmetrical shape be formed so that along the direction of a line of intersection between a plane including an optical path of the optical paths of the principal ray which is incident on the reflecting surface and an optical path emergent from the reflecting surface and the reflecting surface, optical power in a plane perpendicular to the line of intersection may gradually become great.

Or it is preferable that the aforementioned at least one reflecting surface of a non-rotation symmetrical surface be such that optical power on one end side along the direction of a line of intersection between a plane including an optical path of the optical paths of the principal ray which is incident on the reflecting surface and an optical path emergent from the reflecting surface and the reflecting surface and in a plane perpendicular to the line of intersection is greater than optical power on the other end side and in the plane perpendicular to the line of intersection.

Or it is preferable that the aforementioned at least one reflecting surface of a non-rotation symmetrical shape include two reflecting surfaces of a non-rotation symmetrical shape.

Or it is preferable that the two reflecting surfaces of a non-rotation symmetrical shape be disposed in opposed relationship with each other.

Or it is preferable that the two reflecting surfaces of a non-rotation symmetrical shape be disposed so as to fold the principal ray.

Also, a scanning type image displaying apparatus which is a further aspect of the present invention is provided with:

a light source; and

the above-described optical scanning apparatus for displaying an image on the surface to be scanned with light from the light source.

Also, an optical scanning apparatus which is a further aspect of the present invention is provided with:

an optical system for two-dimensionally scanning a surface to be scanned with light from a light source;

wherein when the principal ray of a beam incident on the substantial center of an angle of view in the surface to be scanned is defined as a reference axis ray, the reference axis ray is obliquely incident on the surface to be scanned, and

wherein in a case where the direction of a line of intersection between a plane including the reference axis ray incident on the surface to be scanned and a normal to the surface to be scanned at the incidence position of the reference axis ray and the surface to be scanned is defined as a first direction,

a direction perpendicular to the first direction in the surface to be scanned is defined as a second direction,

beams incident on two different points differing in the coordinates of the first direction from each other and substantially coincident with each other in the coordinates of the second direction, in the surface to be scanned, are defined as a first beam and a second beam, and

the principal ray of the first beam is defined as a first principal ray, and the principal ray of the second beam is defined as a second principal ray,

the first principal ray emergent from the optical system and the second principal ray emergent from the optical system substantially overlap each other when viewed from the first direction.

In the above-described optical scanning apparatus, it is preferable that the optical system include:

a deflecting optical system for deflecting the light from the light source; and

a scanning optical system including at least one reflecting surface and for directing the light deflected by the deflecting optical system to the surface to be scanned.

Also, a scanning type image displaying apparatus which is a further aspect of the present invention is provided with:

a light source; and

the above-described optical scanning apparatus for displaying an image on the surface to be scanned with light from the light source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of the essential portions of a two-dimensional scanning apparatus according to First Embodiment of the present invention, and FIG. 1B is an enlarged perspective view of a part of apparatus shown in FIG. 1A.

FIGS. 2A and 2B are cross-sectional views of the essential portions of the two-dimensional scanning apparatus according to First Embodiment of the present invention.

FIG. 3 is a schematic view of the essential portions of an MEMS device.

FIGS. 4A and 4B are schematic views of the essential portions of a scanning optical system in First Embodiment of the present invention.

FIGS. 5A and 5B are illustrations of the shapes of scanning mirrors in First Embodiment of the present invention.

FIGS. 6A and 6B are illustrations of changes in the curvature of a first scanning mirror in First Embodiment of the present invention.

FIGS. 7A and 7B are illustrations of changes in the curvature of a second scanning mirror in First Embodiment of the present invention.

FIG. 8 is an illustration of a scanning image (grating) in First Embodiment of the present invention.

FIGS. 9A and 9B are illustrations of methods of calculating TV distortion and trapezoid distortion.

FIG. 10 is an illustration of a scanning image (grating) in a comparative example.

FIG. 11 is a schematic view of the essential portions of the scanning type image displaying apparatus of the present invention.

FIG. 12 is a schematic view of the essential portions of the scanning type image displaying apparatus of the present invention.

FIG. 13 is a schematic view of the essential portions of the scanning type image displaying apparatus of the present invention.

FIGS. 14A and 14B are cross-sectional views of the essential portions of a two-dimensional scanning apparatus according to Second Embodiment of the present invention.

FIG. 15 is a schematic view of the essential portions of three color light sources for color display.

FIG. 16 is a schematic view of the essential portions of an MEMS device capable of resonating in a two-dimensional direction.

FIGS. 17A and 17B are illustrations of the shapes of scanning mirrors in Second Embodiment of the present invention.

FIGS. 18A and 18B are illustrations of a change in the curvature of a first scanning mirror in Second Embodiment of the present invention.

FIGS. 19A and 19B are illustrations of a change in the curvature of a second scanning mirror in Second Embodiment of the present invention.

FIG. 20 is an illustration of a scanning image (grating) in Second Embodiment of the present invention.

FIG. 21 is a perspective view of the essential portions of a two-dimensional scanning apparatus according to Third Embodiment of the present invention.

FIGS. 22A and 22B are cross-sectional views of the essential portions of the two-dimensional scanning apparatus according to Third Embodiment of the present invention.

FIG. 23 is a schematic view of the essential portions of a scanning optical system in Third Embodiment of the present invention.

FIGS. 24A and 24B are illustrations of the shapes of scanning mirrors in Third Embodiment of the present invention.

FIGS. 25A and 25B are illustrations of a change in the curvature of a first reflecting surface of a prism in Third Embodiment of the present invention.

FIGS. 26A and 26B are illustrations of a change in the curvature of a second reflecting surface of the prism in Third Embodiment of the present invention.

FIG. 27 is an illustration of a scanning image (grating) in Third Embodiment of the present invention.

FIG. 28 is a schematic view of the essential portions of the two-dimensional scanning apparatus according to First Embodiment of the present invention.

FIG. 29 is a perspective view of the essential portions of two-dimensional scanning apparatus according to the modified Embodiment of the present invention (numerical Embodiment).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some embodiments of the present invention will hereinafter be described with reference to the drawings.

First Embodiment

FIG. 1 is a perspective view of the essential portions of a two-dimensional scanning apparatus according to First Embodiment of the present invention, FIG. 2A is a cross-sectional view (horizontal scanning sectional view, or XZ cross section) of the essential portions of First Embodiment of the present invention in a horizontal scanning direction, and FIG. 2B is a cross-sectional view (vertical scanning sectional view, or YZ cross section) of the essential portions of First Embodiment of the present invention in a vertical scanning direction.

In these figures, the reference numeral 101 designates light source means having a semiconductor laser capable of effecting light modulation (which need not be a semiconductor laser if it is a light emitting element), for example, a red semiconductor laser (or a green semiconductor laser, or a blue semiconductor laser or a semiconductor laser emitting light of other color within a visible light area). However, a red semiconductor laser alone can display (project) only a red image and therefore, this light source means 101 may be designed to have a red semiconductor laser, a blue semiconductor laser, a green semiconductor laser, etc., and a color combining system (a color combining prism or the like) for color-combining lights emitted from these lasers, and be capable of displaying a color image. Also, the light source means may have a semiconductor laser emitting white light (modulation is effected by the semiconductor laser, and it is desirable that the two-dimensional scanning apparatus in that case be designed to have a filter (such as a color wheel) time-divisionally transmitting lights of different colors (red, green and blue) therethrough. Also, it may be designed to have a color resolving optical system for color-resolving white light into red, green and blue lights, light modulating elements for modulating the respective color lights (light modulating elements corresponding to red, green and blue lights, respectively), and a color combining system for color-combining the lights from the light modulating elements. When it is designed to have a color combining system, it is desirable that the color combining system be disposed more adjacent to the semiconductor laser side than to a condensing lens which will be described later.

The reference numeral 102 denotes a condensing lens (collimator lens) which converts a divergent beam emitted from the light source means 101 into a parallel beam (or a convergent beam or a divergent beam). The reference numeral 103 designates an aperture stop which limits the beam passing therethrough and shapes a beam shape. The reference numeral 104 denotes a convergent light converting optical system which comprises a single condensing lens and converts the beam passed through the aperture stop 103 into a convergent beam.

The reference numeral 105 designates deflecting means (two-dimensional deflecting means) having a first deflector 105a having a reflecting surface capable of resonating (vibrating) in a one-dimensional direction (here, a rotational direction about a predetermined first axis), and a second deflector 105b having a reflecting surface rotatable in a rotational direction about a second axis substantially perpendicular to the aforementioned predetermined first axis. Here, the reflecting surface the first deflector 105a has substantially singly vibrates in the rotational direction about the first axis, and the reflecting surface the second deflector 105b has effects rotating motion (here, reciprocal motion in the rotational direction) at a frequency differing from that of the reflecting surface the aforedescribed first deflector 105a has, in the rotational direction about the second axis. Also, the reflecting surface the second deflector 105b has effects uniform velocity motion with respect to the rotational direction about the second axis. Also, the reflecting surface the second deflector 105b has may be designed to effect rotating motion so that the interval between lights (lights condensed in a dot shape) directed onto a projection surface (such as a screen) may be substantially equal intervals (in other words, the lights may move at a uniform velocity on the projection surface with respect to a direction perpendicular to the aforedescribed second axis).

In the present embodiment, the beam emitted from the light source means 101 is deflected in a horizontal scanning direction (a second scanning direction or the direction of the X-axis) by the rotation of the first deflector 105a, and the beam (deflected beam) from the first deflector 105a is deflected in a vertical scanning direction (a first scanning direction or the direction of the Y-axis) perpendicular to the horizontal scanning direction by the rotation of the second deflector 105b, whereby the beam emitted from the light source means 101 is two-dimensionally deflected.

The reference numeral 106 denotes a scanning optical system (two-dimensional scanning optical system which has two first and second scanning mirrors 106a and 106b comprising reflecting surfaces of a non-rotation symmetrical shape, and causes the deflected beam deflected in a two-dimensional direction by the deflecting means 105 to be imaged as a spot near a surface 107 to be scanned.

The reference numeral 107 designates a screen surface as the surface to be scanned. Here, this screen surface is substantially an imaging surface, i.e., a position at which the image of light modulated by a light modulating element is formed (the light modulating element and the screen surface are substantially conjugate with each other).

In the present embodiment, the divergent beam emitted from the light source means 101 is converted into a parallel beam by the condensing lens 102, and has its beam width limited by the aperture stop 103. The beam passed through the aperture stop 103 is converted into a convergent beam having a desired degree of convergence by the convergent beam converting optical system 104. The converted beam is deflected in the horizontal scanning direction by the first deflector 105a, and is further deflected in the vertical scanning direction by the second deflector 105b, whereby the beam emitted from the light source means 101 is deflected in a two-dimensional direction. The deflected beam deflected by the deflecting means 105 is directed onto the screen surface 107 through the scanning optical system 106, and optically scans on the screen surface 107. As described above, the deflected beam optionally scans in the horizontal scanning direction at a high speed by the first deflector 105a to thereby describe a scanning line, and optically scans in the vertical scanning direction at a low speed by the second deflector 105b and displays a two-dimensional image on the screen surface 107.

In the present embodiment, as the first deflector 105a, use is made of an MEMS device manufactured by micro electro-mechanical systems (MEMS) technique or the like.

In the present embodiment, as shown in FIG. 2B, the deflected beam deflected by the first deflector 105a and the second deflector 105b optically scans on the screen surface 107 through the scanning optical system 106. At this time, of the deflected beam deflected in the two-dimensional direction by the deflecting means 105, the principal ray of the deflected beam at the central angle of view which is the center of the horizontal scanning direction (the direction of the X-axis) and the vertical scanning direction (the direction of the Y-axis) (the center of an area and an angle range in which an image is projected, or the center of an area and an angle range in which the projection of an image is possible) is defined as the "reference ray Lvc".

The scanning line in the horizontal direction by the reference ray Lvc corresponds to the X-axis, and the scanning line in the vertical direction by the reference ray Lvc corresponds to the Y-axis. A plane containing the reference ray Lvc and the horizontal direction (the direction of the X-axis) is defined as a horizontal scanning section (a second scanning section, or XZ section), and a plane containing the reference ray Lvc and the vertical direction (the direction of the Y-axis) is defined as a vertical scanning section (a first scanning section, or YZ section).

FIG. 3 shows a schematic view of the essential portions of the MEMS device.

In FIG. 3, the reference character 105a designates the MEMS device as a one-dimensional deflector. A reflecting surface 105a-1 is supported on a housing 105a-3 by a torsion bar 105a-2, and a magnet provided on the back of the reflecting surface 105a-1 reacts on a magnetic force generated from a coil, not shown, and vibrates in a one-dimensional direction (effects reciprocal movement, i.e., vibrates in a rotational direction about a predetermined axis. Ideally, it is desirable that the magnet effect simple harmonic oscillation substantially in the rotational direction about the predetermined axis in accordance with a predetermined natural frequency.) By this vibration, the direction of the MEMS device 105a is adjusted so that the deflected beam may be deflected in the horizontal scanning direction.

Also, as the second deflector 105b, use is made of a plane mirror mounted on a stepping motor displaced at a uniform angular speed. In the present embodiment, the MEMS device 105a which is the first deflector and the deflecting mirror 105b which is the second deflector are disposed in proximity to each other, and the interval therebetween is 7.0 (mm). Of course, this second deflector 105b may also be constituted by an MEMS device (MEMS mirror).

It is desirable that the scanning image described on the screen surface 107 by the two-dimensional scanning apparatus be displayed as per an inputted image signal. In the two-dimensional scanning apparatus, however, in addition to the distortion of the scanning optical system 106 and isometric distortion, TV distortion occurs and image strain occurs from a desired shape given by the image signal and deteriorates the dignity of the scanning image, and this has posed a problem. Particularly, TV distortion attributable to two-dimensional scanning is a frame line which usually ought to be of a rectangular shape or a grating-shaped image displayed curvedly, and has remarkably deteriorated the dignity of the image.

Also, the two-dimensional scanning apparatus according to the present embodiment displays the scanning image on the screen surface 107 by an oblique projecting process.

In the two-dimensional scanning apparatus according to the present embodiment, in the vertical scanning direction (a plane parallel to the vertical direction), the reference ray Lvc is made incident on the screen surface 107 at a finite angle .theta.vc (.noteq.0 deg.). Particularly, with regard to all beams, the incidence angle in the vertical scanning direction (the incidence angle of each ray onto the screen surface in a plane parallel to the vertical direction and containing each ray) is .theta.vi.ltoreq.0 (deg.) or greater.

Thus, by the oblique projecting process, the scanning image displayed on the screen surface 107 can be upwardly shifted to thereby display the scanning image at a position easy for an observer to see. Also, when a scanning type image displaying apparatus carrying this two-dimensional scanning apparatus thereon is placed on a stand such as a desk, all images are designed to be capable of being displayed above the desk, namely, on the screen surface 107, without the scanning image being displayed at the same height as the desk.

In the present embodiment, the scanning image is displayed on the screen surface 107 as the surface to be scanned by the use of the oblique projecting process, and it is in the vertical scanning section that the scanning image is obliquely projected. At this time, in the vertical scanning section, the reference ray Lvc is obliquely incident on the screen surface 107, and the incidence angle is 15.1 (deg.). Here, when a side on which the angle at which the deflected beam (the beam deflected by the aforedescribed first and second deflectors and emitted) is incident on the screen surface 107 is great is defined as upper, and a side on which the incidence angle is small is defined as lower, the principal ray of the beam incident on the uppermost portion of the screen surface 107 is incident on the screen surface 107 at an incidence angle .theta.vu=28.2 (deg.), and the principal ray of the beam incident on the lowermost portion of the screen surface 107 is incident on the screen surface 107 perpendicularly thereto, i.e., at an incidence angle .theta.v1=0.00 (deg.). Consequently, in the present embodiment, with regard to all beams, the incidence angle in the vertical scanning direction is .theta.vi.ltoreq.0.00 (deg.). On the other hand, in the horizontal scanning section, the reference ray Lvc is incident on the screen surface 107 perpendicularly thereto.

When as described above, an image is displayed on the screen surface 107 by the oblique projecting process, there arises the problem that trapezoid distortion occurs greatly and reduces the dignity of the displayed image.

Also, in the present embodiment, the beam (incident beam) emitted from the light source means 101 to the first deflector 105a for deflecting the beam in the horizontal scanning direction at an angle from the vertical scanning direction which is a direction perpendicular to the deflecting direction thereof is made incident on the deflecting surface of the first deflector 105a, and the construction of so-called oblique incidence is adopted.

In the case of the incidence in the deflecting surface in which the incident beam is made incident from the horizontal scanning direction which is the deflecting direction of the first deflector 105a onto the first deflector 105a, the width of the beam which can be deflected differs depending on the direction of the first deflector 105a, and particularly when the beam is deflected in a direction away from the incidence direction, the incident beam comes to be greatly eclipsed, whereby the loss of the light amount becomes a problem.

The incidence angle at which the beam is made incident from the light source means 101 onto the deflecting means 105 is defined by the angle formed between the principal ray of the incident beam and the reference ray Lvc.

Description will be made here of the case of the incidence in the deflecting surface.

When supposing an angle of view similar to that in the present embodiment, the horizontal angle of view of the scanning optical system is 37.80 (deg.) and the vertical angle of view thereof is 21.17 (deg.), and the incidence angle from in the deflecting surface is 30 (deg.), the width of the deflectable beam changes at 98-66% relative to the width of the reflecting surface of the first deflector 150a with a change in the direction of the reflecting surface of the first deflector 105a. The width of the deflectable beam decreases, whereby the light amount of the deflected beam also decreases and the loss of the light amount occurs.

On the other hand, when as in the present embodiment, the beam is made obliquely incident from the vertical scanning direction, the width of the deflectable beam is hardly affected by the direction of the reflecting surface of the first deflector 105a. In the present embodiment, the incidence angle in oblique incidence is 20 (deg.), and if the width of the deflectable beam is 94-93% relative to the width of the reflecting surface of the first deflector 105a (if it is of the order of 88-99%, there is no problem, but yet if possible, 93 to 94% is desirable). Thus, the reflecting surface of the first deflector 105a becomes effectively usable, and the decrease in the width of the deflectable beam becomes extremely small and the problem of the loss of the light amount is improved.

Description will now be made of the two first and second scanning mirrors 106a and 106b constituting the scanning optical system 106.

FIG. 4A is a schematic view of the essential portions of the two-dimensional scanning apparatus according to the present embodiment in the horizontal scanning direction, and FIG. 4B is a schematic view of the essential portions in the vertical scanning direction of FIG. 4A. FIG. 28 is a schematic view of the essential portions of the two-dimensional scanning apparatus according to the present embodiment.

In the present embodiment, the scanning optical system 106 comprises two scanning mirrors, i.e., the first scanning mirror 106a and the second scanning mirror 106b in succession from the deflecting means 105 side. Of course, the optical elements this scanning optical system has are not restricted to the two mirrors, but may be three or more mirrors, or the scanning optical system may have a refractive lens, a diffracting optical element or the like besides the mirrors.

The optical path from after the reference ray Lvc is reflected by the reflecting surface of the first scanning mirror 106a of the scanning optical system 106 until it arrives at the reflecting surface of the second scanning mirror 106b is defined as the "reference axis BA" of the scanning optical system 106.

The first and second scanning mirrors 106a and 106b are tilted (and shifted) only in the vertical scanning section (in YZ cross section), and in the vertical scanning direction, they are disposed so as to fold the optical path of the deflected beam (so as to face each other in the vertical direction, or in other words, so that the ray may reciprocally move in the vertical direction when viewed from the horizontal direction). Also, in the horizontal scanning section, they are disposed symmetrically with respect to a plane including the reference axis BA, and further the shape of the reflecting surfaces of the first and second scanning mirrors 106a and 106b is made into a shape symmetrical with respect to a plane including the reference axis BA.

The term "fold" means that the angle of the reference ray Lvc reflected from the first scanning mirror and incident on the second scanning mirror with respect to the reference ray Lvc incident on the first scanning mirror and the angle of the reference ray Lvc emergent from the second scanning mirror with respect to the reference ray Lvc reflected from the first scanning mirror and incident on the second scanning mirror are of different signs, or in other words, the direction in which the reference ray Lvc is deflected by the first scanning mirror and the direction in which the reference ray Lvc is deflected by the second scanning mirror are opposite to each other. Also, it is preferable that the angle formed between the reference ray Lvc incident on the first scanning mirror and the reference ray Lvc emergent from the second scanning mirror be smaller than the angle formed between the reference ray Lvc incident on the first scanning mirror and the reference ray Lvc reflected from the first scanning mirror and incident on the second scanning mirror, and/or smaller than the angle formed between the reference ray Lvc reflected from the first scanning mirror and incident on the second scanning mirror and the reference ray Lvc emergent from the second scanning mirror.

Here, it is desirable that the angle formed between the reference ray Lvc incident on the first scanning mirror and the reference ray Lvc emergent from the second scanning mirror be 0 degree or greater and 40 degrees or less (preferably 25 degrees or less). Further, it is desirable that the angle formed between the reference ray Lvc incident on the first scanning mirror and the reference ray Lvc emergent from the first scanning mirror and incident on the second scanning mirror, and/or the angle formed between the reference ray Lvc emergent from the second scanning mirror and the reference ray Lvc emergent from the first scanning mirror and incident on the second scanning mirror be 60 degrees or greater (preferably 85 degrees or greater) and within 160 degrees (preferably within 120 degrees).

In FIG. 4B, the reference numeral 104 designates the convergent light converting optical system constituted by a single-piece condensing lens as previously described. This convergent light converting optical system 104 has positive power which converges the incident beam at a position separate by 239.71 (mm) from the first deflector 105a. The distance from the first deflector 105a to the surface 107 to be scanned is 357.90 (mm) along the reference axis BA, and the natural converging point of the incident beam converted into a convergent beam by the convergent light converting optical system 104 is disposed between the first deflector 105a and the surface 107 to be scanned. Further, the distance between the first deflector 105a and the last surface of the scanning optical system 106 (the reflecting surface of the second scanning mirror 106b) is 31.70 (mm) along the reference axis BA, and the natural converging point of the incident beam is disposed between the scanning optical system 106 and the surface 107 to be scanned.

The scanning optical system 106 has negative power as a whole, and converts the deflected beam meeting the natural converging point on this side of the surface 107 to be scanned into a weak convergent beam and causes it to be imaged near the surface 107 to be scanned.

Table 1 below shows the construction of the scanning optical system 106 in the present embodiment.

TABLE-US-00001 TABLE 1 Construction of Scanning Optical System surface vertex coordinates coordinates inclination lens surface surface shape Ry Rx thickness Nd .nu.d x y z a b c convergent light incidence spherical surface 123.47 123.47 converting optical surface system 104 emergence flat surface flat flat 2.00 1.51633 64.1 surface first deflector 105a reflecting flat surface flat flat 0.00 5.52 4.31 72.00 0.00 0.00 second deflector surface 105b reflecting flat surface flat flat 0.00 0.00 0.00 -31.76 0.00 0.00 surface first scanning mirror reflecting XY polynominal flat* flat* 0.00 -0.42 18.85 65.39 0.00 0.00 106a surface second scanning reflecting XY polynominal flat* flat* 0.00 -13.85 30.83 57.73 0.00 0.00 mirror 106b surface surface 107 to be flat surface flat flat 0.00 77.11 332.97 0.00 0.00 0.00 scanned The mark * is an aspherical surface shape, and indicates the radius of the base curved surface. Aspherical Surface Coefficients lens surface surface shape K C.sub.01 C.sub.20 C.sub.02 first scanning reflecting XY polynominal 0.0000E+00 8.2514E-02 -2.9326E-03 -2.8905E-03 mirror 106a surface C.sub.04 C.sub.41 C.sub.23 C.sub.05 -2.1065E-05 4.7882E-07 -1.5387E-07 1.7319E-06 lens surface surface shape K C.sub.01 C.sub.20 C.sub.02 second reflecting XY polynominal 0.0000E+00 8.2514E-02 -2.9326E-03 -2.8905E-03 scanning surface C.sub.04 C.sub.41 C.sub.23 C.sub.05 mirror 106b -2.1065E-05 4.7882E-07 -1.5387E-07 1.7319E-06 surface surface shape C.sub.21 C.sub.03 C.sub.40 C.sub.22 first scanning reflecting XY polynominal -1.9746E-05 1.0062E-04 4.6042E-06 9.4047E-06 mirror 106a surface C.sub.60 C.sub.42 C.sub.24 C.sub.06 -2.5514E-08 -1.0474E-07 1.0481E-07 -4.6873E-08 lens surface surface shape C.sub.21 C.sub.03 C.sub.40 C.sub.22 second reflecting XY polynominal -1.9746E-05 1.0062E-04 4.6042E-06 9.4047E-06 scanning surface C.sub.60 C.sub.42 C.sub.24 C.sub.06 mirror 106b -2.5514E-08 -1.0474E-07 1.0481E-07 -4.6873E-08

A free curved surface shape expressed by the following XY polynominal (A) is used for the first and second scanning mirrors 106a and 106b in the present embodiment.

.kappa..times..SIGMA..times..times..times..times..times..times..times..tim- es..times..times..times..times..times..times..times..times..kappa..times..- times..times..times..times. ##EQU00002##

Each of the reflecting surfaces of the first and second scanning mirrors 106a and 106b comprises a non-rotation symmetrical surface not having a rotation symmetrical axis having, in the horizontal scanning direction, a shape symmetrical with respect to the reference axis BA, having, in the vertical scanning direction, a shape asymmetrical with respect to the reference axis BA, and further in the vertical scanning direction, is disposed while being shifted or tilted.

In the case of a scanning type image displaying apparatus in which as in the present embodiment, the beam is obliquely projected in the vertical scanning direction, the trapezoid distortion of the scanning image displayed on the screen surface 107 is of a shape in which the width of the scanning image in the horizontal scanning direction gradually widens from below toward above (as it faces in a direction in which the incidence angle becomes greater).

So, in the present embodiment, the scanning optical system 106 is made to include two or more scanning mirrors having reflecting surfaces formed into a non-rotation symmetrical shape, and at least two of these reflecting surfaces are tilted (and shifted) in the vertical scanning direction and are disposed so as to fold the optical path of the deflected beam to thereby correct the trapezoid distortion well.

FIG. 5A is an illustration typically showing the shape of the first scanning mirror 106a, and FIG. 5B is an illustration typically showing the shape of the second scanning mirror 106b. The shape of the first scanning mirror 106a of FIG. 5A is a shape as it is viewed from the deflecting means 105 side, and the lower surface thereof is a reflecting surface. The shape of the second scanning mirror 106b of FIG. 5B is a shape as it is viewed from the deflecting means 105 side, and the upper surface thereof is a reflecting surface.

FIG. 6A is an illustration showing a change in the curvature of the first scanning mirror 106a in the horizontal scanning direction (the direction of the X-axis), and FIG. 6B is an illustration showing a change in the curvature of the first scanning mirror 106a in the vertical scanning direction (the direction of the Y-axis).

FIG. 7A is an illustration showing a change in the curvature of the second scanning mirror 106b in the horizontal scanning direction (the direction of the X-axis), and FIG. 7B is an illustration showing a change in the curvature of the second scanning mirror 106b in the vertical scanning direction (the direction of the Y-axis).

At this time, each illustration of the change in curvature represents the case where the first scanning mirror 106a or the second scanning mirror 106b is viewed from the screen surface 107 side.

Description will now be made of the surface shape of the first scanning mirror 106a.

The reflecting surface of the first scanning mirror 106a in the present embodiment is formed by a curvature monotonously changing anamorphic surface which will be described later.

The first scanning mirror 106a, in the vertical scanning section containing the reference axis BA, is negative in the curvature in the vertical scanning direction (the direction of the Y-axis), and the shape of the reflecting surface thereof is a concave surface, and this scanning mirror has positive power. In the vertical scanning section containing the reference axis BA, the curvature in the horizontal scanning direction (the direction of the X-axis) is deformed from negative to positive when it moves along the vertical scanning direction, and the shape of the reflecting surface is also deformed from a concave surface to a flat surface, and is further deformed to a convex surface. That is, the reflecting surface of the first scanning mirror 106a is a surface deformed from a barrel type toric surface to a saddle type toric surface depending on the position in the vertical scanning direction.

In this surface shape, when it moves from one end to the other end of the reflecting surface in the vertical scanning direction, the curvature in the horizontal scanning direction monotonously (gradually) changes from small to great (or from great to small). This surface shape will hereinafter be referred to as the "curvature monotonously changing anamorphic surface".

The curvature monotonously changing anamorphic surface refers to a surface shape in which when in the vertical scanning direction (first scanning direction) in which the reference ray Lvc is inclinedly incident on the surface 107 to be scanned, it moves from one end to the other end of the reflecting surface, the curvature in the horizontal scanning direction (second scanning direction) orthogonal to the vertical scanning direction monotonously increases from small to great or monotonously decreases from great to small. Therefore, the shape of the reflecting surface in the vertical scanning direction is a shape asymmetrical with respect to the reference axis BA, and is an anamorphic surface differing in curvature between the vertical scanning direction and the horizontal scanning direction, and is formed by a non-rotation symmetrical surface not having a rotation symmetrical axis.

Description will now be made of the surface shape of the second scanning mirror 106b.

The reflecting surface of the second scanning mirror 106b is formed by a curvature monotonously changing anamorphic surface.

The second scanning mirror 106b is such that in the vertical scanning section containing the reference axis BA, the surface shape thereof in the horizontal scanning direction, when it moves along the vertical scanning direction, is a surface deformed from a convex surface to a flat surface, and is further deformed to a concave surface, and the power thereof also changes from