JPH02170108A - Laser display device - Google Patents

Abstract

PURPOSE:To obtain an excellent distortionless image by deciding the distortion state of an image formed by deflecting a brightness-modulated laser beam from the deflection state of a reference beam and imposing brightness modulation by a video signal at timing based upon the position state of the beam. CONSTITUTION:Optical modulators 2a, 2b, and 2c impose brightness modulation upon laser beams of respective colors according to the video signal from an input terminal 41, the beam l1 composed of the modulated respective color beams is made incident on a rotary polygon mirror 10, and the horizontally deflected laser beam l2 is converted by a projection lens 6 into a projection beam l3, which is deflected vertically by a galvanomirror 7 to illuminate a screen 9. The reference laser beam ls1 is also made incident on the laser beam incidence point l3 of the polygon mirror 10 and the reflected beam ls2 of the beam ls1 is made incident on a cylindrical lens 13; and the reference laser beam ls3 is made incident on an optical position sensor 20 and the same scanning state as the scanning state of the beam l3 is reproduced on the laser beam incidence surface of the sensor 20 without any image distortion because the incidence point la is the same.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser display device that performs drawing by raster scanning using a laser beam.

[Summary of the invention]

The present invention provides a laser display device that performs drawing by raster scanning using a laser beam, in which a reference beam is incident on the laser beam incident point of a deflection means for deflecting the laser beam, and the deflection state of the reference beam is detected. By controlling the modulation timing of the laser beam by the brightness modulation means, drawing by the laser beam on the screen can be performed satisfactorily without distortion.

[Conventional technology]

Conventionally, as a projection type video display device using a laser beam, as shown in Utility Model Application Publication No. 56-152456 or Television Magazine Vol. Kimono is proposed.

In FIG. 4, (1a) and (1b) indicate laser light sources such as semiconductor lasers and gas lasers;
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 light source (1b) are reflected by a dichroic mirror (3a).
) and separate the laser beams of each color, 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. And each optical modulator (2a)
, (2b) and (2c) are supplied with a modulation signal corresponding to a primary color signal as a video signal of a display image, and each optical modulator (2a), (2b) and (2c) supplies a modulation signal based on the modulation signal. Intensity modulation of each color laser beam. and,
Laser beams I output from the optical modulators (2a), (2b) and (2c) are supplied to deflectors (5a), (5b) and (5c), respectively. Then, the blue laser beam outputted by the deflector (5c) is supplied to the dichroic mirror (3b) via the reflecting prism (4b), and
) 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 ink 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. 5 is a diagram showing this deflection state. For example, as shown in FIG. 5A, the plane mirror (11,
), the reflected laser beam 12out is directed downward in the figure.

Then, by rotating the reflecting part (11), the plane mirror (111)
The incident angle of the laser beam lin and the laser beam lin gradually change, the emission direction of the reflected laser beam changes, and as shown in No. 5iB, the reflection part (11) rotates by an angle θ, and the plane mirror
l, ) at the other end of the laser beam! ! , in begins to be incident, the reflected laser beam bout' begins to head upward in the figure. At this time, the laser beam j2
The angle θ2 between the laser beam Rout' and the laser beam Rout' 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 laser beam is deflected 25 times in one rotation of the reflecting section (11).

The reflected laser beam from the rotating polygon mirror (10) is then supplied to the galvano mirror (7) via the projection lens (6). This galvano mirror (7) is driven by a drive source (7a
), the galvanometer mirror (7) is rotated at predetermined intervals, and the laser beam supplied from the rotating polygon mirror (10) is deflected 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 reflecting mirror (8) to the screen (9).
irradiate the back side of the Then, the image drawn by the laser beam is viewed from the front side of this screen (9).

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 modulation signal supplied to the rotary polygon mirror (10) and the deflection period of the galvano mirror (7). 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 B to be Solved by the Invention] By the way, when an image is displayed using such a display device, there is an inconvenience that some kind of image distortion occurs in the displayed image. In other words, since the mass of the rotating part of a rotating polygon mirror that performs horizontal deflection is extremely large, it is difficult to control the rotation speed narrowly in synchronization with the horizontal synchronization signal of the video signal to be displayed. It is not possible to absorb fluctuations and distortions in the signal period, resulting in distortion of the displayed image. Further, image distortion occurs due to the mirror finishing accuracy of the rotating polygon mirror, the rotational accuracy of the rotating polygon mirror driving motor, and the like.

Furthermore, the deflection scan obtained with a rotating polygon mirror is a constant angular velocity scan, which does not have a constant velocity on the screen, and the scanning speed of the beam differs between the center and the edges of the screen, for example, the image at the edges is There was an inconvenience that it was distorted.

In view of these points, it is an object of the present invention to provide a laser display device of this type that can eliminate image distortion.

[Means for Solving the Problems] The laser display device of the present invention includes a luminance modulation means (2a) based on a video signal, as shown in FIGS. 1 and 3, for example.
, (2b), (2c) laser beam with intensity modulation! , is periodically deflected by a predetermined angle using a rotating polygon mirror (10) to reach a screen, and the laser of the rotating polygon mirror (10) Beam incidence point! A reference beam j2s different from the laser beam 2I is incident on a, and an optical position sensor (20) is arranged at the arrival position of this reference beam ff1s3 deflected by the rotating polygon mirror (10). Brightness modulation means (2a) for converting the video signal based on the detection signal of the sensor (20);
The timing of supplying to (2b) and (2c) is controlled.

Further, the laser display device of the present invention is provided with a storage means (42) for storing a video signal for at least one horizontal scanning line, and a clock signal synchronized with the phase of the detection signal of the optical position sensor (20) is sent to a PLL circuit (3o ), and based on this clock signal, the video signal is read out from the storage means (42) and supplied to the brightness modulation means (2a), (2b), and (2c).

[Effect]

According to the present invention, a laser beam whose brightness is modulated based on the polarization state of the reference beam ff1s3! 1 can be determined, and by performing brightness modulation with a video signal at a timing based on the position detection state of this reference beam βs3, a good image with distortion removed can be displayed. be done.

[Example] Hereinafter, an example of the laser display device of the present invention will be described with reference to FIGS.
Let's explain with reference to FIG. In FIGS. 1 to 3, parts corresponding to those in FIG. 4 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

The first part is the rotating polygon mirror (10) of the laser display device of this example.
This is a laser display device that draws images by raster scanning of a laser beam, similar to the laser display device in the example shown in FIG. 4, and other parts are constructed in the same manner as in FIG. 4.

In FIG. 1, (10) indicates a rotating polygon mirror, and this rotating polygon mirror (10) consists of a reflecting part (11) and a driving part (12), and the reflecting part (11) is a 20-sided plane mirror (11, ),
(11□)...(11□.) are arranged in an annular shape, and the reflecting part (11) is rotationally driven by a driving part (12).

And in this example, modulators (2a), (2b)
, a laser beam p whose brightness is adjusted by (2c),
1 is each plane mirror (11,), (11□
)...(11°). In this case, in this example, the reflective part (
The laser beam incident point in step 11) is set to la. And this incident laser beam! The reflected beam 12 by the reflecting part (11) of 1 is reflected by each plane mirror (1) according to the rotation of the reflecting part (11).
11,), (11°)...(11□.), and this reflected beam I! , 2, and place the projection lens (6) at a position where it can be reached.
) more projection beam! Get 3.

Here, in this example, the reflecting part (
11>, a reference laser beam fs is made incident on the laser beam incidence point βa. This reference laser beam ff5l
is the laser beam for drawing mentioned above! A beam of constant output is output from a laser source (not shown) different from laser beam 1, and is configured to be incident at a predetermined angle ψ with respect to the drawing laser beam ρ8. For this reason, the reference laser beam ls
The reflected reference laser beam J2s2 reflected by the reflecting part (11) is emitted at a different angle from the reflected beam 12 for drawing, and the reflected reference beam ff5z is emitted in the emission direction.
A cylindrical lens (13) is placed. This cylindrical lens (13) deflects the beam from the projection lens (6) described above so that the reflected reference laser beam j2sz is distributed and deflected into a fan-shaped optical path according to the rotation of the rotating polygon mirror (10). The reference laser beam j2sz is converted into a reference laser beam j2sz with a polarization state equal to that of the reference laser beam j2sz. Then, the reference laser beam ff53 on a predetermined optical path emitted by this cylindrical lens (]3) is transmitted to the optical position sensor (
20).

This optical position sensor (20) uses a reference laser beam I!
It detects the deflection position of s, and is constructed as shown in FIG. That is, this optical position sensor (20) has a transparent front plate (21) provided with grid-shaped light shielding parts (22) long at equal intervals in the lateral direction, and a casing to which this front plate (2I) is attached. A light receiving element (24) is arranged inside (23),
The laser beam transmitted through the front plate (21) is received and detected by this light receiving element (24). In this case, the light shielding part (22
) is displayed on the screen (9), for example.
Preferably, the spacing corresponds to an integral multiple or fraction of the pixel pitch. By doing this, the reference laser beam ρs3 that is deflected and moves is incident on the front plate (2I) provided with the light shielding portion (22). In this case, the arrangement direction (horizontal direction) of the grid-like stripes of the light shielding part (22) and the moving direction of the reference laser beam Esz are arranged to match.

In this example, as shown in FIG. 3, the detection signal of the light receiving element (24) of this optical position sensor (20) is
L L circuit (phase locked loop circuit) (30)
The comparison signal is supplied to one comparison signal input terminal of the phase comparator (31). This PLL circuit (30) includes a phase comparator (3
The phase difference signal of 1) is supplied to the voltage controlled oscillator (33) via the low pass filter (32).
3) is supplied to the other comparison signal input terminal of the phase comparator (31) via the 1/N frequency divider (34).

In this case, the voltage controlled oscillator (33) has an oscillation center frequency of 20 MHz, for example.

Further, the digital composite video signal obtained at the video signal input terminal (41) for modulating the laser beam is supplied to a line memory (42) that stores one horizontal line, and the digital composite video signal read from this line memory (42) is The video signal is supplied to a 7-trix circuit (44) via a digital/analog converter (43), and this matrix circuit (44) converts it into primary color signals of red, green, and blue, and each primary color signal is assigned a corresponding one. It is supplied as a modulation control signal to the optical modulators (2a), (2b) and (2c).

In this case, the continuous output of video signals from the line memory (42) is controlled by the voltage controlled oscillator (
33) in conjunction with the oscillation signal.

Next, to explain the operation when displaying an image using a video signal with the laser display device of this example, the input terminal (41
) according to the video signal obtained from the optical modulator (2a),
In (2b) and (2c), the brightness modulation of the laser beams of each color is performed, and the combined laser beam l, which is a combination of the brightness-modulated laser beams of each color, is sent to the rotating polygon mirror (10) as shown in Fig. 1. The incident and horizontally deflected reflected laser beam p,2 passes through the projection lens (6) and becomes a projection beam 13.
The light is converted into an image, vertically deflected by a galvanometer mirror (7), and then irradiated onto a screen (9).

Here, the laser beam incident point ρa of the rotating polygon mirror (10)
Since the reference laser beam ES+ is also incident on the
A reflected beam ff1sz of the reference laser beam ls is incident on the cylindrical lens (13), and a reference laser beam ff1s3 is incident on the optical position sensor (20).

The deflection state of the reflected reference laser beam j2s3 at this time is the laser beam incidence point! Since a is the same, the projected laser beam! The projected laser beam on the screen (9), equal to the horizontal deflection state of 3! A scanning state similar to that of No. 3 is reproduced on the laser beam incident surface of the optical position sensor (20). Since there is a checkered light shielding part (22) on the laser beam surface of the optical position sensor (20), the incident state of the laser beams p and s3 on the light receiving element (24) is intermittent in conjunction with the checkered pattern. The laser beam detection signal from the light receiving element (24) becomes a pulse signal synchronized with the horizontal deflection state of the laser beam.

Then, in the PLL circuit (30), the oscillator (33) oscillates a frequency signal that is the same as +tJ+ with this pulse signal, so the PLL circuit (30) outputs the video signal Ht from the line memory (42) with a frequency signal synchronized with this pulse signal. , optical modulator (2
a).

(2b) and (2c) as modulation control signals.

Light modulator (2a), (2b),
Since the brightness modulation in (2c) is controlled, the laser beam ρ3 of the image at the corresponding coordinate position reaches the coordinate position of each horizontal scanning line on the screen (9), and the laser beam ρ3 of the image at the corresponding coordinate position reaches the coordinate position of each horizontal scanning line on the screen (9). Eliminates distortion of each horizontal scan line of the displayed image. That is, the image displayed on the screen (9) is horizontally deflected using the rotating polygon mirror (10), but at the same time, the reference laser beam ρs1 is also deflected, and the deflection state of the reflected reference laser beam j2s3 is Optical position sensor (20
), each optical modulator (2a) (2b) of the video signal
, (2c) is corrected, so that distortion of each horizontal scanning line of the displayed image is eliminated. In this case, various internal factors such as distortion due to the difference in scanning speed of the beam between the center and edge of the screen due to deflection by the rotating polygon mirror, mirror distortion and rotational unevenness of the rotating polygon mirror, etc. In addition to correcting distortion caused by external factors such as disturbance of the input video signal, distortion caused by external factors such as disturbance of the input video signal is also corrected. This is particularly effective when the horizontal deflection angle is widened.

In the above embodiment, the optical modulator was constructed separately from the laser source, but if a semiconductor laser is used as the laser source, the laser output from the semiconductor laser can be directly converted into a beam whose brightness is modulated by a video signal. It becomes possible to output. In addition, the reference laser beam was different from the drawing laser beam by changing the optical path by changing the incident angle to the rotating polygon mirror.
, superimposed on the incident laser beam, p,1, and the reflected laser beam! 2 or! 3, the infrared laser beam may be separated by a dichroic ink mirror and guided to the optical position sensor. Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist of the present invention.

FIG. 5 is a route map for explaining the example shown in FIG.

(2a), (2b), (2c) are optical modulators, (
10) is a rotating polygon mirror, (13) is a cylindrical lens, (20) is an optical position sensor, (30) is a PLL circuit, (
42) is line memory,! S'''z+j2S3 is a reference laser beam.

[Effects of the Invention] The laser display device of the present invention has the advantage that distortion of each horizontal scanning line of a displayed image can be removed with a simple configuration.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. A laser beam whose brightness is modulated by a brightness modulation means based on a video signal is periodically deflected by a predetermined angle using a deflection means to reach a predetermined surface, and the reaching beam is raster scanned. In the laser display device for drawing on the predetermined surface, a reference beam different from the laser beam is made incident on the laser beam incidence point of the deflection means, and the position where the reference beam deflected by the deflection means reaches. A laser display device characterized in that an optical position sensor is disposed at the optical position sensor, and the timing of supplying the video signal to the luminance modulation means is controlled based on the detection signal of the optical position sensor. 2. A storage means for storing the video signal for at least one horizontal scanning line is provided, a clock signal synchronized with the phase of the detection signal of the optical position sensor is created, and the video signal is stored from the storage means based on the clock signal. 2. The laser display device according to claim 1, wherein the readout signal is read out and supplied to the brightness modulation means.