JPH03116088A - Laser display device - Google Patents

Abstract

PURPOSE:To correct the luminance distortion and the hue balance of an image on a screen by storing in advance a luminance correction coefficient in a memory, reading it out successively by synchronizing with a raster scan of a laser beam, and controlling the gain of an optical modulator for modulating the luminance of the laser beam. CONSTITUTION:Read-only memories 40a - 40c provided with an address corresponding to a coordinate position on a screen for displaying an image are allowed to store in advance a luminance correction coefficient, and by synchronizing with a raster scan of a laser beam, the stored luminance correction coefficient is read out, and by bringing this luminance correction coefficient and a luminance modulating signal of a laser beam to multiplication 60a - 60c, the luminance correction is executed. In such a way, a luminance distortion of an image displayed on the screen can be eliminated, and also, by only correcting the luminance correction data stored in the read-only memories 40a, 40b and 40c, a luminance difference of a screen boundary on the screen can also be eliminated, and the adjustment of the color balance extending over the whole area on a screen image can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser display device that displays television images and the like using a laser beam.

[Summary of the invention]

In a laser display device, a brightness correction coefficient is stored in advance in a read-only memory (ROM) having an address corresponding to a coordinate position on a screen where an image is displayed, and the brightness correction coefficient is stored in advance in synchronization with raster scanning of a laser beam. By sequentially reading the brightness correction coefficients stored in the ROM and controlling the gain of the optical modulator that modulates the brightness of the laser beam, the brightness distortion and hue balance of the image on the screen can be corrected. This is what I did.

[Conventional technology]

There is a laser display device that modulates the intensity of three-color laser beams of red, green, and blue, and scans the intensity-modulated laser beams onto a screen using, for example, a rotating polygon mirror to display an image such as a television image. .

FIG. 4 is an overall perspective view of an example of the laser display device described above.

In the figure, (la), (lb) and (Ic) are red, green and blue laser light sources, respectively, and the laser beams from these laser light sources (la), (lb) and (Ic) are transmitted to the optical modulator (2a). ) (2b) and (2C). Then, modulation signals R, G, and B corresponding to the video signal are supplied to optical modulators (2a), (2b), and (2C), respectively, and each laser beam is intensity-modulated according to these modulation signals R, G, and B. Ru. And each optical modulator (2a) (
The laser beams output from 2b) and (2C) are transmitted through beam diameter adjustment lenses (3a) (3b) and (3), respectively.
After being transmitted through the dielectric mirror (4a)
(4b) and (4C). The blue laser beam reflected by the dielectric mirror (4C) is supplied to the dielectric mirror (4b), combined with the green laser beam, and supplied to the dielectric mirror (4a). Then, in this dielectric mirror (4a), it is combined with the red laser beam to obtain a composite laser beam l of three primary colors. This combined laser beam 2I is then supplied to the reflecting section (11) of the rotating polygon mirror (9).

The reflecting section (11) of the rotating polygon mirror (9) has a structure in which plane mirrors are arranged in a ring shape at equal intervals, and the reflecting section (11) is rotated at high speed by a driving means (not shown). The incident laser beam is deflected by this reflection section (11). For example, when the reflecting section (11) is composed of a 25-sided plane mirror, one plane mirror performs one deflection, and one of the rotating polygon mirrors (9)
The rotation results in 25 deflections of the laser beam.

The laser beam horizontally deflected into a fan shape by the rotating polygon mirror (9) is supplied to the relay lens (12a) and converted into parallel scanning light. This parallel scanning light is then supplied to a relay lens (12b) and focused on a galvano mirror (13) placed at the focal point of this relay lens (12b). This galvano mirror (
Reference numeral 13) deflects and scans the laser beam in the vertical direction, and its rotation is controlled by a driving means (13a>).

The laser beam reflected by the galvanometer mirror (13) is irradiated onto the back surface of the screen (15) via the projection lens (14). This projection lens (14
) is a parallel scanning laser beam that is passed through a screen (15
) to increase the resolution of the image. The image is then observed from the front side of this screen (15).

Here, by synchronizing the deflection period of the laser beam by the rotating polygon mirror (9) and the deflection period by the galvanometer mirror (13) with the horizontal scanning period and vertical scanning period of the video signal, respectively, an image based on the video signal is created. The image is raster-scanned and drawn on the screen (15) by a laser beam.

In order to display a television image on the screen (15), it is necessary to modulate the brightness of the laser beam in synchronization with raster scanning as described above. In order to achieve horizontal synchronization, a pulse signal corresponding to the rotation speed of the rotating polygon mirror (9) is generated, and the pulse signal is synchronized with the horizontal synchronization signal of the video signal. ) rotation speed must be controlled.

However, since the mass of the rotating polygon mirror (9) is extremely large, it is impossible to control the rotation speed of the rotating polygon mirror (9) for each scanning line, so a portion of the horizontally scanned light is received by the light receiving element. The brightness modulation start position is determined by generating a trigger signal.

References: JP-A-48-38997, JP-A-61-
Publication No. 90112 Publication No. 152456 of Utility Model Publication No. 1125 system Caesar color display ■, ■" (
(Journal of the Society of Television Engineers, Vol. 29, No. 2, 1975) [Problems to be Solved by the Invention] Incidentally, in a laser display device, the horizontal scanning of the laser beam by the rotating polygon mirror (9) is constant angular velocity scanning. On (15), the scanning speed is not uniform. Therefore, the horizontal scanning speed is different between the central part and the end part of the screen (15), and the brightness of each part is also different, resulting in uneven brightness on the screen.

This is because, when the incident angle of the laser beam on the screen (15) is φ, the horizontal scanning speed is proportional to tanφ. For example, when the scanning surface is small as in a laser printer, it is possible to correct this using a correction lens, but when using a large screen such as a laser display device, it is possible to correct this using a correction lens. It is extremely difficult to correct this.

Therefore, it is conceivable to correct the image distortion caused by the difference in the horizontal scanning speed of the laser beam on the screen (15) described above by changing the image information capture speed according to the scanning speed. However, at the edges of the screen (15) where the horizontal scanning speed is high, the light energy density decreases, resulting in a low average brightness.

Particularly in the case of a thin rear projection type, this effect becomes significant because of the wide-angle deflection. In the case of this rear projection type, the directivity is made stronger at the center of the screen (15) in accordance with the case where the image is observed at the center of the screen (15). However, such directivity improvement alone cannot correct the above-mentioned decrease in optical energy density.

In addition, in the case of so-called multi-screens, where multiple laser display devices are lined up to create a large screen, differences in directivity occur depending on the position from which the image is viewed, resulting in significant differences in brightness between the screens. Put it away. Furthermore, there is a problem in that the color balance of the three colors of laser beams is not uniform on the scanning line, resulting in partial deviations. This is because the chromatic aberration and efficiency of the optical system vary depending on the wavelength, and also vary depending on the deflection scanning angle.

[Means to solve the problem]

Therefore, the present invention provides a read-only memory (40a) having an address corresponding to a coordinate position on a screen (15) for displaying an image in a laser display device.
> (40b) (40c) A brightness correction coefficient is stored in advance in the read-only memory (40a) (40b) (4) in synchronization with the raster scanning of the laser beam.
The brightness correction coefficient stored in 0c) is read out, and the brightness correction coefficient is multiplied by the brightness modulation signal of the laser beam to perform brightness correction.

[Effect]

It is possible to eliminate brightness distortion of the image displayed on the screen (15), and the ROM (40a) (40b
) (40C) By simply modifying the brightness correction data stored in , it is possible to eliminate the brightness difference at the screen boundary on a so-called multi-screen, and it is possible to adjust the color balance over the entire screen image.

〔Example〕

FIG. 1 is a block diagram of one embodiment of the present invention.

In the figure, a composite video signal, which is drawing information, is supplied from an input terminal (21) to an RGB demodulation circuit (20). Then, the output terminal (
22a) (22b) (22c) to video signal R
, G, B are multiplication circuits (60a) (60b) (60c
) are supplied respectively. In addition, the RGB demodulation circuit (
A horizontal synchronizing signal H is supplied from the output terminal (23) of the V counter (30) to the counting input terminal (31) of the V counter (30), and the number of horizontal scanning lines is counted by the V counter (30). Also, the output terminal (24) of the RGB demodulation circuit (20)
A vertical synchronizing signal V is supplied from the V counter (30) to the reset input terminal (32). Then this V counter (
30) resets the counted number of horizontal scanning lines every field scan according to the supplied vertical synchronizing signal V, and repeats the counting. Then, the count value counted by the V counter (30) is supplied from the V counter (30) to the upper bit position of the read address port of the ROM (40a) (40b) (40c).

Further, the clock signal CL is supplied from the output terminal (25) of the RG-B demodulation circuit (20) to the counting input terminal (37) of the H counter (35), and the beam position of the horizontal scanning line is determined by the H counter (35). A clock count value corresponding to is obtained. In addition, the output terminal of the RGB demodulation circuit (20) (
The horizontal synchronizing signal H from the H counter (35) is supplied to the reset input terminal (36) of the H counter (35).
The clock count value obtained in step 35) is reset every time a horizontal scan ends. And this H counter (35)
The clock count value counted by ROM (40a
) (40b) (40c) are supplied to the lower bit positions of the address port. By doing this, the ROM (40a) (40b) (40
c) The addresses of these ROMs (4
0a) (40b) (40C) Data of brightness correction values stored in advance can be read out in response to raster scanning.

In addition, in this case, the V counter (30) and the H counter (
35) without connecting the lower bits of the count output digital data, only the upper bits are stored in the ROM (40a> (40b
) (40c) If you connect to the address human port,
The correction values of a plurality of adjacent pixels on a raster-scanned screen can be regarded as the same value and can be represented by ROM (40a).
(40b) The storage capacity of (40c) can be reduced. For example, if the lower 3 bits of the count output data of each counter (30) and (35) are ignored without being connected, the same correction value will represent 8 pixels each horizontally and vertically on the screen, that is, 8×8 pixels. I can do it,
The storage capacity of the ROM (40a) (40b) (40c) can be saved to 1764, which is the number of pixels of the screen.

And ROM (40a) (40b) (40c)
The read data from each D/A conversion circuit (50
a) (50b) (50c) 1. :Supplied,RO
The correction voltage corresponding to the brightness correction value stored in M (40a) (40b) (40c) is applied to the D/A conversion circuit (5
0a) (50b) (50c). And the D/A conversion circuit (50a) (50b) (
50c) The correction voltage signal is sent to the multiplier circuit (60a)
(60b) (60c) are supplied. And these multiplication circuits (60a) (60b) (60c)
As a result, the signals R, G, and B supplied from the RGB demodulation circuit (20) are multiplied by the correction voltage signal, and the brightness is corrected in accordance with the screen position. Then, the corrected signals R, G, and B are transmitted to the multiplication circuits (60a) (60b) (
60c) to the drive circuit (70a) (70b) (70
c) supplied to. This drive circuit (70a
) (70b) (70c) are the supplied signals R, G,
The ultrasonic oscillation output signal in accordance with B is supplied to optical modulators (2a) (2b) (2c) consisting of acousto-optic elements. The intensity of the laser beam is modulated by these optical modulators (2a), (2b), and (2c).

Note that the above-mentioned ROM (40a) (40b) (
40c) The brightness correction value stored in advance is determined by inputting a video signal of the same brightness as an adjustment value when assembling the laser display device, measuring the brightness of the three colors red, edge, and blue on the screen. It is obtained by calculating the reciprocal value of the measured luminance value.

According to the above-described embodiment, the luminance distortion caused by color unevenness on the screen and the difference in the horizontal scanning speed of the laser beam can be reduced to ROM (40a) (40b) (40C
) can be corrected simply by changing the brightness correction value stored in .

FIG. 2 is a block diagram of another embodiment of the invention,
Components equivalent to the example in FIG. 1 are given the same reference numerals.

The difference between the example in Figure 1 and the example in Figure 2 is that
The example in the figure shows ROM (40a) (40b) <40 based on the synchronization signal and clock signal extracted from the video signal.
c) It reads out the correction data of
The example in Figure 2 shows the ROM (40a) (40b) based on the actual position of the laser beam spot on the screen.
(40c) This is to read out the correction data.

Then, the actual position of the laser beam spot on the screen is detected as shown in FIG.

That is, in FIG. 3, (28) is a gicroic mirror that reflects infrared light but transmits the laser beam lt as it is, and (26) is an infrared laser light source. A reference infrared laser beam 1r is emitted from this light source (26), and this beam lr is supplied to a mirror (28) through a collimator lens (27) and combined into a display beam 11.

Therefore, the beam 1 obtained from the rotating polygon mirror (9),
contains beam ir, which is horizontally deflected simultaneously and equally with beam 11.

In addition, on the optical path of the laser beam 11 (including beam 1r) between the relay lenses (12&) and (12b), infrared light is reflected in the same manner as the Gui-Kui lock mirror (28), but the laser beam 11 is A diquilock mirror (29) that transmits the light as is is provided, and this mirror (29) separates the original display beam l and the reference beam lr, and the beam l is directly passed through the lens as described above. (12b), while the beam 1r is fed to the grating plate (33).

The lattice plate (33) is, for example, a rectangular transparent glass substrate on which a light-shielding film is formed, and a light-transmitting pattern in a predetermined shape is formed on the light-shielding film.

That is, for example, the light shielding film is made of Cr, Ti, Ni
Metal films such as laser beam I! The light-shielding film is formed by a vacuum film forming method to a thickness that is opaque to r, and this light-shielding film is photo-etched to form a light-transmitting pattern.

In this case, the light-transmitting pattern each has a plurality of linear light-transmitting parts arranged in the length direction of the substrate, and the width of the pattern (length in the arrangement direction) is the length of the mirror (29).
The horizontal scanning width of the laser beam 11r separated by the horizontal scanning width is set equal to or slightly smaller than the horizontal scanning width of the laser beam 11r.

These patterns are used to obtain clock signals during horizontal scanning, and the transparent part is connected to the screen (1
They are formed at equal intervals over a range corresponding to at least the effective horizontal scanning range in 5) and corresponding to the horizontal curvature of the screen (15). Also,
The number of transparent parts in this pattern is an integral multiple of 1
The number of pixels in a horizontal line is made equal to, for example, 910 pixels.

Also, these patterns are similar to Beam I! This is a pattern for detecting the start point of effective horizontal scanning of r and specifying the start point of modulation of beam 11 by signals R, , B.

Furthermore, these patterns are for phase locking of the PLL, which will be described later.

In addition, these patterns detect the end point of effective horizontal scanning of beam βr and detect beams l,
This is used to specify the end point of modulation.

Therefore, since these patterns are horizontally scanned by the beam βr, a laser beam Rr whose intensity changes in accordance with the horizontal scanning is obtained from the grating plate (33>).

This beam Ilr is then supplied to the photosensor (38) through the condensing lens (34), and the sensor (38) outputs a pulse signal Sp1 that rises or falls according to the change in the intensity of the laser beam βr, that is, the laser beam An alternating signal Sp of frequency and phase corresponding to the change in intensity of 1r is extracted.

In this case, the frequency and phase (rising and falling points) of the signal Sp are such that the laser beam 1r is
3) corresponds to the horizontal scanning position when horizontally scanning. Further, the horizontal scanning position when the laser beam Ilr horizontally scans the grating plate (33) corresponds to the horizontal scanning position when the laser beam L 2 horizontally scans the screen (15). Therefore, the frequency and phase (rising and falling points) of the signal Sp are:
This corresponds to the horizontal scanning position when the laser beam 11 horizontally scans the screen (15).

Now, as shown in Fig. 3, ROM (40a) (40b) (40c) is
The embodiment shown in FIG. 2 for reading out the correction data will be described.

In FIG. 2, the output terminal (
22a) (22b) (22c) Video signal R from
, G, and B are A/D conversion circuits (80a) (80
b) Line memory (90a) via (80c)
) (90b) (90c) are supplied to the write human power ports. The write clock signal CL from the output terminal (25) of the RGB demodulation circuit (20) is supplied to the write clock input terminals of the line memories (90a) (90b) (90c). Then, video signals R and G are generated according to the supplied clock signal CL.

B is line memory (90a) (90b) (90c)
will be written to.

On the other hand, the signal Sp from the photosensor (38) is sent to the first phase comparator circuit (42) via the waveform shaping circuit (41).
Supplied as comparative manpower. This comparison circuit (42), together with circuits (43) to (45), includes a P
This composes the LL circuit (46) and the comparator circuit (46).
The comparison output of 2) is passed through a low-pass filter (43) to V
CO (44) as its control signal, and this V
C0 (44) The oscillation signal RCL is a frequency dividing circuit (45)
The frequency is divided into a frequency equal to that of the signal Sp, and the frequency-divided output is supplied to the comparator circuit (42) as a second comparator.

Therefore, the oscillation frequency and phase of the VCO (44) change following the frequency and phase of the signal Sp.

This oscillation signal RCL is transmitted to the line memory (90a
) (90b) (90c) and the H counter (35) as its read clock. Also, at this time, the signal Sp from the shaping circuit (41) is supplied to the pattern detection circuit (49), and the signal Rut indicating each horizontal scanning start position of the beam L is taken out. 90a) (90b) (90c)
and is supplied to the H counter (35) as a read start signal.

Then, depending on the horizontal position of the laser beam on the screen (15), each video signal R, G, B is transferred to each line memory (
90a> (90b) (90c) are sequentially read out from the D/A conversion circuit (81a) (81b) (81
c) supplied to.

Then, the D/A conversion circuit (81a) (81,b) (
81c), each video signal R, G, B is converted into a corresponding voltage signal, and each multiplier circuit (60a
> (60b) is supplied to (60c).

Also, ROM (40a) (40b) (40c)
The brightness correction data stored in the H counter (35
) is performed according to the horizontal scanning position of the laser beam on the screen (15), and the ROM (40a) (4
0b) (40c) Since the read address is specified, the data is read out in correspondence with the position of the laser beam on the screen.

and ROM (40a) (40b) (40C)
The brightness correction data read from the D/A conversion circuit (5
0a> (50b) (50c) and after being converted into a voltage signal, the multiplier circuit (60a) (60b)
(60c) respectively. In these multiplication circuits (60a) (60b) (60c), the video signals R, G, and B are subjected to brightness correction. The brightness-corrected video signals R, G, and B are sent to the drive circuit (70a).
(70b) Via (70c), the optical modulator (2a)
(2b) Supplied to (2C).

In addition, ROM <40a) (40b) (40c)
The brightness correction data stored in the screen (15) is obtained by raster scanning with the same brightness specification after the assembly of the laser display device, measuring the brightness of each point on the screen (15), and adjusting the brightness so that it is a constant value and the optimum value. This is determined so that white balance can be obtained.

According to the embodiment shown in FIG. 2, hue unevenness occurs due to chromatic aberration of the optical components of the Raded display device, efficiency differences due to deflection angles, or differences in scanning line speed on the screen. Brightness unevenness, etc. can be completely corrected.

In the above example, horizontal scanning of the laser beam is performed using a rotating polygon mirror (9), but horizontal scanning may be performed using an acousto-optic deflector.

In addition, in the example in FIG. 2, the D/A conversion circuit (81a) (
81b) (81c) is a multiplication circuit (60a) (60b
) (60c) may be connected to the subsequent stage.

〔Effect of the invention〕

Thus, according to the invention, the ROM (40a) (40
b) A brightness correction coefficient is stored in advance in (40c), and the brightness correction coefficient is stored in ROM (40c) in synchronization with the raster scanning of the laser beam.
The brightness correction coefficient stored in 0a), (40b), and (40c) is read out, and the brightness correction coefficient is multiplied by the brightness modulation signal of the laser beam to perform brightness correction. It is possible to eliminate uneven brightness and hue shift over the entire surface.

Furthermore, when a so-called multi-screen is configured using a plurality of radar display devices, there is no difference in brightness at the boundary between the screens, and it is possible to realize a multi-screen where the entire screen has a -like brightness.

Furthermore, since there is no need to use expensive optical components to eliminate chromatic aberration, it is possible to realize a radar display device that can be mass-produced at low cost.

Furthermore, since the brightness correction value can be set after the assembly of the laser display device is completed, errors accumulated during assembly of the optical components can be adjusted.

Furthermore, when wide-angle projection is performed on a flat screen, there is no need to use optical components for correcting the scanning speed of the laser beam, making it possible to reduce the number of components.

[Brief explanation of drawings]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 is a block diagram of another embodiment of the invention, and Fig. 3 is a block diagram for detecting the position of the actual laser beam spot on the screen (15). FIG. 4 is a perspective view of the entire laser display device. (la) (lb) (lc) is a laser light source, (2a)
(2b) (2c) is a light modulator, (15) is a screen, (20) is an RGB demodulation circuit, (30) is a V counter, (35) is an H counter, (38) is a photosensor, (
40a) (40b) (40c) are ROMs. (46) is a PLL circuit, (49) is a pattern detection circuit,
(60a) (60b) (60c) are multiplication circuits,
β1 is the display laser beam, ! r is a reference laser beam.

Claims (1)

[Claims] A laser display device that displays an image on a screen by raster scanning a laser beam whose brightness is modulated based on a video signal, comprising: a memory that stores brightness correction data; and the laser beam on the screen. means for reading the brightness correction data stored in the memory in accordance with the scanning position of the image signal; and means for correcting the brightness information of the video signal based on the read brightness correction data; The laser display device is configured such that the laser beam is brightness-modulated based on the video signal with the brightness information corrected, thereby correcting brightness unevenness and hue unevenness on the screen.