JPH02168219A - Image display device - Google Patents

Abstract

PURPOSE:To contrive the decrease, etc., of a rotating speed of a rotary polygon mirror by allowing a focusing light beam to be made incident on the rotary polygon mirror so that it is not shielded by a fixed plane mirror, reflecting repeatedly this focusing light beam between the rotary polygon mirror and the fixed plane mirror, and enlarging a deflection angle made by the rotary polygon mirror. CONSTITUTION:A fixed plane mirror 20 is placed so as to be opposed to a specular surface part 11 of a rotary polygon mirror 10, and a focusing light beam l1 is made incident on the rotary polygon mirror 10 at a prescribed elevation angle phi against a virtual plane being orthogonal to a rotation axis (m) of the rotary polygon mirror 10 so that it is not shielded by this fixed plane mirror 20. This focusing light beam l1 is reflected repeatedly between the rotary polygon mirror 10 and the fixed plane mirror 20 so as to enlarge a deflection angle made by the rotary polygon mirror 10. In such a way, by a simple constitution for only placing the fixed plane mirror in a prescribed position, the deflection angle can be enlarged satisfactorily, and the decrease, etc., of a rotating speed of the rotary polygon mirror can be contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image display device suitable for application to, for example, a laser disk play device that performs drawing by raster scanning of a laser beam.

[Summary of the invention]

The present invention provides an image display device that deflects a focused light beam such as a laser beam using a rotating polygon mirror to draw images by raster scanning or the like, in which a fixed plane mirror facing the mirror surface of the rotating polygon mirror is arranged under predetermined conditions. The focused light beam is made incident on the rotating polygon mirror so as not to be blocked by the fixed plane mirror, and this focused light beam is repeatedly reflected between the rotating polygon mirror and the fixed plane mirror to enlarge the deflection angle by the rotating polygon mirror. This makes it possible to slow down the rotation speed of the polygon mirror.

(Prior Art) Conventionally, as a projection type video display device using a laser beam, as shown in Japanese Utility Model Application Publication No. 56-152456 or Television Magazine Vol. 29 No. 2 (1975), Something like the one shown in the figure has been proposed.

In this FIG. 6, (1a) and (1b) indicate laser light sources such as semiconductor lasers and gas lasers, and the laser light sources (
The red laser light from 1a) is supplied to the optical modulator (2a). In addition, the green laser beam and blue laser beam from the laser beam 'tA (1b) are transferred to a dichroic mirror (
3a) to separate the laser beams into respective color laser beams, the green laser beam is supplied to the optical modulator (2b), and the blue laser beam is supplied to the optical modulator (2c) via the reflective prism (4a). supply to. Then, each optical modulator (2a
), (2b) and (2c) are supplied with a modulation signal according to the primary color signal as the video signal of the displayed image, and each optical modulator (2a), (2b) and (2C) is supplied with a modulation signal based on the modulation signal. to modulate the intensity of each color laser beam. The laser beams output from the optical modulators (2a), (2b) and (2c) are deflected by a deflector (5a), respectively.

(5b) and (5c). And deflector (5
Reflecting prism (4b) reflects the blue laser beam outputted by C).
) to the dichroic mirror (3b), and the green laser beam output from the deflector (5b) is supplied to the other surface of this dichroic mirror (3b) to combine the blue laser beam and the green laser beam. . Further, this combined laser beam is supplied to a dichroic mirror (3c), and the red laser beam outputted by the deflector (5a) is supplied to the other surface of this dichroic mirror (3C) to obtain a combined laser beam of the three primary colors. . This combined laser beam is then supplied to the reflecting section (11) of the rotating polygon mirror (10).

The rotating polygon mirror (10) has a reflecting section (11) formed by disposing plane mirrors in an annular shape at equal intervals, and the annular reflecting section (11) is rotated at high speed by a driving means.

In this case, the reflecting surface (11) is composed of, for example, 25 plane mirrors, and deflects the laser beam incident on each plane mirror.

FIG. 7 is a diagram showing this deflection state. For example, as shown in FIG. 7A, the plane mirror (111
), the reflected laser beam 1out is directed downward in the figure. Then, due to the rotation of the reflecting section (11), the plane 1! (111)
The incident angle between the laser beam fin and the laser beam fin gradually changes,
The emission direction of the reflected laser beam changes, and as shown in FIG. 7B, the reflection part (11) rotates by an angle θ1, and the plane mirror (
When the laser beam fin is incident on the other end of the laser beam 41I), the anti-1 laser beam Bout' is directed upward in the figure. At this time, the laser beam 1ou
The angle θ2 between t and the laser beam fout' is the deflection angle by this plane mirror (Ill). Deflection at a similar angle is also performed on other plane mirrors of the reflecting surface (11). Therefore, when the reflecting section (11) is composed of a plane mirror with 25 surfaces, the Rade beam is deflected 25 times in one rotation of the reflecting section (11).

Then, the reflected laser beam from this rotating polygon mirror (10) is transmitted to a galvano mirror (7) via a projection lens (6).
supply to. This galvano mirror (7) is driven by a drive source (7).
The rotation is controlled by (a), and the galvanometer mirror (7) is rotated at predetermined intervals to deflect the laser beam supplied from the rotating polygon mirror (10) by a predetermined angle at predetermined intervals.

In this case, the direction of deflection by the rotating polygon mirror (10) and the direction of deflection by the galvano mirror (7) are set to be orthogonal, and the deflection by the rotating polygon mirror (10) causes the horizontal deflection of the television receiver. A corresponding deflection takes place, and with the deflection by the galvanometer mirror (7) a deflection corresponding to the vertical deflection of the television receiver takes place.

The laser beam reflected by the galvanomirror (7) is then reflected via the reflector (8) to the screen (
9) Irradiate the back side. And this screen (9
) The image drawn by the laser beam is viewed from the surface side.

Here, each optical modulator (2a), (2b) and (2c
) by synchronizing the horizontal scanning period and vertical scanning period of the video signal that creates the modulating signal supplied to the The image is drawn by a laser beam in raster scanning, and one field of image is drawn in one field period of the video signal, thereby operating as a projection type video display device.

[Problem to be solved by the invention]

By the way, when considering actually operating a display device having such a configuration, for example, if the horizontal scanning line 112
In order to display five video signals, it was necessary to rotate the 25-sided rotating polygon mirror at 81,000 revolutions per minute, and it was necessary to use special drive motors and bearings designed for ultra-high-speed rotation. Moreover, when such high-speed rotation is performed, each plane mirror of the rotating polygon mirror moves at a high speed exceeding the speed of sound, which is not desirable from the viewpoint of the safety of the apparatus.

In order to solve this problem, it is conceivable to increase the number of plane mirrors in the reflecting part of the rotating polygon mirror to reduce the rotation speed, but if the diameter of the rotating part of the rotating polygon mirror is increased, the centrifugal force applied to the reflecting part The force becomes stronger, causing elastic distortion of the mirror surface, disrupting raster scanning, and requiring a motor with strong torque, which is impractical.Increasing the number of plane mirrors without changing the diameter will reduce the area of one plane mirror, causing the laser beam to become distorted. The deflection angle becomes very small due to the relationship with the diameter, and from this point of view as well, it is not practical.

To give an example in this regard, the width of each plane of a rotating polygon mirror with a diameter of 40 mm and a pentagonal reflecting surface is 2.
It will be 5mm. When a laser beam with a beam diameter of 1 mm is incident on this polygon mirror, if the laser beam hits both surfaces at the boundary between each plane mirror, so-called vignetting will occur. 40% of the surface
becomes an ineffective part, and only 60% can be used effectively, and the deflection angle becomes very small, making it impractical.

Note that if the beam diameter of the laser beam is made small, the resolution of the displayed image will be reduced, so it is not possible to reduce the invalid period by making the beam diameter small.

In order to solve this problem, for example, as shown in Figure 8,
A laser beam from a laser source (1) is transmitted through a rotating polygon mirror (1).
0) and in a direction perpendicular to the rotation axis of the rotating polygon mirror (
At the same time, the reflected beam from the reflecting section (11) is reflected by a fixed plane mirror (13) and reflected again by the rotating polygon mirror (10). It is conceivable to make the beam incident on the reflecting section (11) and supply the re-reflected beam to the optical path downstream from the rotating polygon mirror (10). In this way, for example, when the reflecting part (11) of the rotating polygonal boundary (10) rotates by Δω, the deflection angle of the reflected beam will be α if there is no plane mirror (13) and the beam is reflected only once. , plane mirror (1
3), and when it is reflected twice at the reflecting part (11), the deflection angle becomes α.
Expanded to 2. A plane mirror fixed in this way (1
3), the deflection angle for each rotation of the rotating polygon It (10) is expanded accordingly, and for example, the number of surfaces of the reflecting portion (11) can be increased without changing the radius of the rotating polygon mirror (10).

However, in the case of this example in Fig. 8, the rotating polygon mirror (10
), the positional relationship between the primary incident point a and the secondary incident point A on each surface of the reflecting part (11) changes, and the secondary incident point may end up on the adjacent surface. Ta. That is, FIG. 9 is a diagram showing changes in the loci of the incident points a and b, and as the primary incident point a approaches the end of the predetermined surface (n+) of the reflecting section (11), the secondary incident point a changes. The incident point moves to the adjacent surface (112), and the deflection angle is disturbed. In addition, as shown in FIG. 10, the incident angle of the laser beam from the laser source (1) is slightly tilted with respect to the direction perpendicular to each surface of the reflecting part (11), and the primary incident point and secondary incident point are It is also possible to prevent the reflected beam from the plane mirror (13) from reaching the adjacent surface by bringing the planes closer to each other, but in this case, the reflected beam deflected to the section S on the back side of the plane mirror (13) The beam will no longer reach you, and the beam will be cut off in the middle.

In view of the above, an object of the present invention is to provide an image display device of this type that can satisfactorily enlarge the deflection angle of a rotating polygon mirror.

[Means to solve the problem]

As shown in FIG. 1, for example, the image display device of the present invention deflects a focused light beam whose brightness is modulated based on an image signal to reach a predetermined surface using a rotating polygon mirror (10), and the arriving beam In an image display device that draws images on a predetermined surface by raster scanning, a mirror surface portion (1
A fixed plane mirror (20) facing the fixed plane mirror (20) is arranged, and a rotating polygon mirror (10) is arranged so as not to be blocked by the fixed plane mirror (20).
) at a predetermined elevation angle ψ with respect to a virtual plane perpendicular to the rotation axis m
Have a focused light beam 1. is incident on the rotating polygon mirror (10), and this focused light beam! , is repeatedly reflected between a rotating polygon mirror (10) and a fixed plane mirror (20) to enlarge the deflection angle by the rotating polygon mirror (10).

Further, according to the image display device of the present invention, as shown in FIGS. 3 and 4, for example, the normal direction of each surface of the rotating polygon mirror (lO) when the light is incident on the center of each surface is used as a reference. , the angle between this reference direction and the incident focused light beam is θ°, the angle between this reference direction and the fixed plane mirror (20) is ψ°, and the radius of the inscribed circle of the rotating polygon mirror (10) is R. When the number of mirror surfaces (11) of the rotating polygon mirror (10) is N, and the shortest distance from the rotation center of the rotating polygon mirror (10) to the fixed plane mirror (20) is y, then ψ and y are [ψ] in the following equations (1) to (6) on the coordinates formed with orthogonal axes. ,yo
) (ψt+)'+) (ψz, yz) The angle ψ and the distance y are selected so that they fall within the range surrounded by the three points.

5 ψ, -gate (9-items x θ) x N - (280 items x θ)
...(3))' + = R...(4) ψ2=-gate (9mo4×θ)XN+(28-item×θ)...
...(5) yz=R...(6) (However, N22) [Operation] According to the present invention, the focused light beam is reflected on each surface of the mirror surface portion (11) of the rotating polygon mirror (10). However, since the focused light beam reflected from the first burning surface part (11) is reflected by the fixed plane mirror (20) and then reflected again by the mirror part (11), the reflection at the mirror part (11) is In proportion to the number of times, the deflection angle increases to more than twice the deflection angle of one time, and the deflection angle increases significantly.

〔Example〕

Hereinafter, one embodiment of the image display device of the present invention will be described with reference to FIGS. 1 to 5. In FIGS. 1 to 5, parts corresponding to those in FIG. 6 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

The image display device of this example performs drawing by raster scanning of a laser beam, similar to the laser display device of the example shown in FIG. 6, and FIG. 1 shows the vicinity of the rotating polygon 1 (10).
The other parts are constructed in the same manner as in FIG.

In Fig. 1, (10) shows the entire rotating polygon mirror, and the reflecting part (11) of this rotating polygon mirror (10) is a 20-sided plane mirror (111), (11□)... (11□ ) are arranged in an annular shape at equal intervals, and a driving part (12) rotates the reflecting part (11) at high speed.

In this example, as shown in FIGS. 1 and 2,
A fixed plane mirror (20) is placed opposite the reflecting portion (11) of the rotating polygon mirror (10). In this case, the reflecting surface (21) of the fixed plane mirror (20) is replaced by the rotating polygon mirror (10).
side, and are arranged in a predetermined positional relationship that will be described later. and,
The intensity-modulated laser beam l is transmitted through a rotating polygon mirror (10
) is made incident on the reflecting section (11) from slightly below the reflecting section (11). At this time, assuming that the rotation axis of the rotating polygon mirror (10) is m, the laser beam j2. The reflective part (
11). Then, as shown in FIG.
) side is reflected three times at three points, point 23, point 16, and point lc, and is reflected twice at the fixed plane mirror (20) side. Finally, an output beam it is obtained from the fc point of the reflection section (11) to be supplied to a subsequent optical path such as a projection lens.

Here, the rotating polygon mirror (10), the fixed plane tU (20), and the incident beam! To explain the positional relationship with , the third
As shown in the figure, the incident beam 2. is incident on the center of each surface of the reflecting portion (11) of the rotating polygon mirror (10), and the normal direction of each surface is defined as a reference direction X, and this reference direction X and the incident beam 2. The angle between the reference direction X and the fixed plane 1'1 (20) is ψ.

The radius of the inscribed circle of the reflecting part (11) of the rotating polygon mirror (10) is R, the number of surfaces of the reflecting part (11) of the rotating polygon mirror (10) is N, and the radius of the inscribed circle of the reflecting part (11) of the rotating polygon mirror (10) is N. When the shortest distance from the center of rotation m to the fixed plane mirror (20) is y, the following equations (1) to (6) are obtained.

ψ. =-θ×(1-) ・・・(1)
t ψ, = Todoroki (9 - each × θ) XN - (28 + Todoroki × θ)...
・(3) y + = R・・・・(4) ψ2=−mon (9+Todoroki×θ) X N + (28−each×
θ)...(5) 3'z=R...(6) (However, N22) Then, considering the coordinates formed with ψ and y as orthogonal axes, as shown in Figure 4, this From the values of equations (1) to (6) [
The coordinates of the three points ψo, yo) (ψ+, y+) (ψz+yz) are calculated, and each value is selected so that it falls within the range of the triangle surrounded by the coordinates of these three points.

By selecting in this way, the laser beam 1 that is incident on a predetermined surface (for example, a plane mirror (11,)) of the reflecting part (11)
The changes in the trajectories of the three incident points fa, fb, and lc in 1 are:
It changes as shown in FIG. That is, when the primary incidence point 1a is located at one end of the plane mirror (11,), the secondary incidence point 1a
b and the tertiary incidence point 1c are located near the other end of the plane mirror (IL). Then, as time passes and the rotation of the rotating polygon mirror (10) causes the primary incident point la to move sequentially toward the other end,
Secondary incidence point on the way! b and the trajectory of the tertiary incidence point 1c, and when the primary incidence point 1a is located at the other end, the secondary incidence point! b and the tertiary incidence point 1c are located closer to one end than the primary incidence point 2a.

Therefore, when the primary incidence point 1a is on this plane mirror (111), the secondary incidence point zb and the tertiary incidence point IC are also located on this plane mirror (111), and as shown in FIG. Output beam 1 with continuous uninterrupted deflection
2 is obtained. In this case, in this example, the rotated polyhedral boundary (
Since the reflecting part (11) of 10) consists of 20 surfaces, the deflection angle of one surface is (360/
20) X 2 = 36°, while the reflecting part (1
Since the same laser beam is incident three times on 1), the deflection angle is doubled at each of the secondary incidence point and the tertiary incidence point, and the total deflection angle is expanded to 36X2X2-1446.

In this way, the deflection angle can be expanded four times compared to the conventional one, thereby widening the left and right deflection angles of the image drawn on the screen (9) as shown in FIG. Moreover, when the size of the screen (9) is the same as before and the deflection angle is the same, the reflecting part (11) of the rotating polygon &U (10)
(Even if the width of each surface is narrowed by increasing the number of surfaces, the deflection angle on each surface can be widened and the same as before, so the rotation polygon mirror (10) can be reduced by the increased number of surfaces. The rotation speed can be lowered, for example, the conventionally required rotation of about 80,000 rotations per minute can be reduced to about 20,000 rotations per minute, leaving a significant burden on the drive mode and bearings.For example, In addition to reducing the size of the motor, it is now possible to use bearings such as normal ball bearings, which previously required air bearings.

Note that the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations may be adopted without departing from the gist of the present invention.

〔Effect of the invention〕

According to the image display device of the present invention, it is possible to satisfactorily expand the deflection angle with a simple configuration of simply arranging a fixed plane mirror at a predetermined position, and it is possible to reduce the rotation speed of the rotating polygon mirror. There are profits that can be made.

[Brief explanation of the drawing]

FIG. 1 is a front view showing essential parts of an embodiment of the image display device of the present invention, and FIGS. 2, 3, 4, and 5 are route maps for explaining the example in FIG. 1, respectively. , FIG. 6 is a block diagram showing an example of a conventional image display device, and FIGS. 7, 8, 9, and 1θ are route maps showing examples of the conventional display device. (lO) is a rotating polygon mirror, (11) is a reflecting part, (111)
, mff1)...(l1g.) is a plane mirror, (20)
2. is a fixed plane mirror; (21) is a reflective surface; 2. is an incident laser beam, and Ilz is an output laser beam.

Claims (1)

[Claims] 1. A focused light beam whose brightness is modulated based on an image signal,
In an image display device that uses a rotating polygon mirror to deflect the beam to reach a predetermined surface, and performs raster scanning of the arriving beam to draw images on the predetermined surface, a fixed plane mirror is disposed opposite to the mirror surface of the rotating polygon mirror, The focused light beam is incident on the rotating polygon mirror at a predetermined elevation angle with respect to a virtual plane perpendicular to the rotation axis of the rotating polygon mirror so as not to be blocked by the fixed plane mirror, and the focused light beam is directed to the rotating polygon mirror. An image display device characterized in that the deflection angle by the rotating polygon mirror is enlarged by repeated reflection between a mirror and the fixed plane mirror. 2. When the focused light beam is incident on the center of each surface of the rotating polygon mirror, the normal direction of each surface is used as a reference, and the angle between this reference direction and the incident focused light beam is θ°, The angle between this reference direction and the fixed plane mirror is ψ°, the radius of the inscribed circle of the rotating polygon mirror is R, the number of mirror surfaces of the rotating polygon mirror is N, and the rotation of the rotating polygon mirror is When the shortest distance from the center to the fixed plane mirror is y, the following (1) on the coordinates formed with ψ and y as orthogonal axes
Equation ~ (6) [ψ_0, y_0] [ψ_1, y_1]
The image display device according to claim 1, wherein the angle ψ and the distance y are selected so that they fall within a range surrounded by three points [ψ_2, y_2]. ψ_0=-θ×(1-55/N^2) (1) y_0=1.51×(1-1.18/10000×θ^
2)×R‥‥(2) ψ_1=1/50×(9-3/10×θ)×N-(28
+3/10×θ)‥(3) y_1=R‥(4) ψ_2=-1/50×(9+3/10×θ)×N+(2
8-3/10×θ) (5) y_2=R (However, N≧8)