JP2001016602A - Projection type liquid crystal display and automatic hue adjustment system - Google Patents

Abstract

(57) [Summary] [Problem] To improve the hue variation of a liquid crystal projector by adjusting the characteristics of a gamma curve to improve the color reproducibility of a projected image by adjusting the level of a plurality of points of the gamma curve. It is possible to improve black floating and halftone hues. In addition, the adjustment is performed automatically to reduce the adjustment time. SOLUTION: An image quality improvement processing unit 6 for correcting three image signals with individually adjusted gamma curves, a microcomputer 17 for adjusting the gamma curves, and an EEPROM 1
8. It has a main body key 20. For automatic adjustment,
It has a personal computer 32 that executes automatic adjustment in a predetermined procedure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display device and an automatic hue adjustment system, and more particularly to improvement of image quality of a projected image and reduction of adjustment time.

[0002]

2. Description of the Related Art A liquid crystal projector displays an image by synthesizing light transmitted through three liquid crystal panels, but the liquid crystal panels used are mass-produced, and the characteristics vary from panel to panel. FIG. 5 shows VT characteristics of the liquid crystal panels having different characteristics as described above (light transmittance characteristics with respect to applied voltage).
Are exemplified, and the manner of dispersion varies and there is no regularity.

[0003] In addition to the above-mentioned variations in the liquid crystal panel, various variations of the liquid crystal projector, such as variations in the chromaticity of the constituent mirrors, variations in the transmittance of the dichroic mirror, and variations in the colors of the lamps of the light source, are provided. There are color variation factors. Since these factors combine to cause a greater variation, the liquid crystal projector had to adjust the hue for each set.

Therefore, as shown in FIG. 6, for example, when the chromaticity at the center of the screen when a 50% white signal is displayed indicates an initial chromaticity value deviating from the adjustment range, red (R),
There is a method in which the chromaticity falls within the adjustment range by moving the gamma curves for correcting the green (G) and blue (B) signals in parallel up and down as shown in FIG. An example of the adjustment procedure when the initial chromaticity is at the position shown in FIG. 6 will be described below (see FIGS. 6 and 7).

(1) Display a 50% white signal,
The x and y values of the chromaticity at the center of the screen are measured by the hue information measuring means. This measured value is used as the initial chromaticity. (2) The gamma curve of B is shifted upward (downward) and y
Decrease (increase) the value, and put only the y value within the adjustment range. (3) Shift the gamma curve of R downward (upward) to obtain x
The value is decreased (increased) and only the x value is within the adjustment range.

(4) If both the x value and the y value are within the adjustment range, the adjustment is terminated. (5) If only the x value is not within the adjustment range (3)
repeat. (6) If only the x value is not within the adjustment range (2)
repeat. (7) If both the x value and the y value are within the adjustment range, the adjustment ends. (8) If both the x value and the y value are not within the adjustment range, repeat steps (2) to (7).

[0007]

In the above-mentioned conventional adjusting method, the chromaticity of the 50% white signal is adjusted by shifting the gamma curve for correcting the R, G, B signals up and down as it is. The hue was adjusted.

In this method, however, the chromaticity of 50% white is adjusted, but only the entire gamma curve is shifted.
If the slope of the T characteristic varies, this leads to a decrease in contrast, floating of black, and the like, and has not been able to improve the variation in hue in the halftone.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress variations in the hue of a liquid crystal projector without causing a decrease in image quality, a decrease in contrast, or a floating black. The present invention also aims at shortening the adjustment time.

[0010]

The light emitted from the light source means is incident on a plurality of liquid crystal light valve means, and the projected image emitted from the image forming surface of the liquid crystal light valve means is reflected by an optical system such as a mirror or a lens. In a projection type liquid crystal display device that performs composite projection on a screen via a screen, 0% of a signal input to a plurality of the liquid crystal light valve means at a predetermined characteristic curve.
And hue adjusting means for individually correcting levels other than 100%, and image quality improving means for correcting the hue of the projected image using the hue adjusting means.

The image quality improving means adjusts the hues of a plurality of points using a gamma characteristic of a light valve having a fixed output value at a certain point of the input signal.

The image quality improving means prepares several types of light valve gamma curves in which the output value of a certain point of the input signal is fixed, and selects an optimum gamma curve from the gamma curves, thereby greatly shortening the adjustment time. Realize shortening.

In the automatic hue adjustment system, a projection type liquid crystal display device according to claim 1, hue information measuring means for measuring hue information of a projected image, and inputting the hue information,
Control processing means for controlling the hue adjustment means so as to perform hue adjustment automatically.

[0014]

FIG. 1 is a block diagram showing a circuit configuration of a projection type liquid crystal display device 25 (hereinafter, referred to as a liquid crystal display device) according to an embodiment of the present invention. First, this configuration will be described. .

The liquid crystal display device 25 includes a signal input unit 1 connected to a video signal source (not shown) such as a personal computer or a VCR.
Then, video signals output from these signal sources are input. The signal input unit 1 divides the video signal into R, G, and B signals s1, s2, and s3 and outputs the signals to the A / D converters 2, 3, and 4.

The digital signal processing unit 5 receives the color signals converted into digital signals by the A / D converters 2, 3, and 4, and performs pixel conversion to the number of pixels of the liquid crystal panel, menu display, enlargement / reduction, and the like. Performs various digital signal processing and processes digital R signal s4, G signal s5, B signal s
6 is output to the image quality improvement processing section 6 through the selectors 26, 27 and 28, respectively.

The selectors 26, 27, 28
S4, s5, s6 from the digital signal processing unit 5 only when the hue adjustment is performed using the internal signal generator.
R, G, B from the signal generator 22
To the image quality improvement processing section 6.

However, when a signal generator is connected to the signal input unit 1 from the outside and the adjustment signal is input from the outside to adjust the hue of the liquid crystal display device, the selectors 26, 27,
28 sends the signal output from the digital signal processing unit 5 to the image quality improvement processing unit 6 as it is.

In the image quality improvement processing section 6, the input R signal s
4. Each signal of the G signal s5 and the B signal s6 is created by shifting the gamma curve selected from FIG. 3 by the shift value v (−h ≦ v ≦ h) of FIG. Each of them is individually corrected by a gamma curve.

The corrected digital R color signal s7 is supplied to the D / A converter 7, the G color signal s8 is supplied to the D / A converter 8, and the B color signal s9 is supplied to the D / A converter 9. Respectively.

The driving circuits 10 to 12 include an image quality improvement processing unit 6
Are corrected by a gamma curve, and the D / A converters 7 to 9
The R, G, and B color signals converted to analog signals are input, and the R, G, and B signals converted to levels that match the specifications of the liquid crystal panel are respectively input to the R, G, and B liquid crystal panels. Output to 13-15.

Each of these liquid crystal panels 13, 14, 15
Functions as a light valve that receives light emitted from a light source (not shown) and outputs a projection image, which is light transmitted through the liquid crystal panel itself, to an optical system 16 including a mirror, a lens, and the like. These projection images are combined by the optical system 16 and projected on a screen (not shown).

The microcomputer 17 executes a task of determining a gamma curve to be used for correction in the image quality improvement processing section 6 according to a predetermined procedure described later. The EEPROM 18 has n types of gamma curves Γm (1 ≦ 1) numbered from 1 to n.
gamma table storage area 1 for storing data of m ≦ n)
8a, a number storage area 18b for storing the number of the selected gamma curve, and a shift value storage area 18c for storing a shift value v for adding to the selected gamma curve and shifting the gamma curve. I have.

The liquid crystal display device 25 includes a remote control light receiving section 19 for receiving an operation signal s10 output from a remote control 31 used when manually performing hue adjustment described later,
Main unit key 20 also used when manually performing hue adjustment
Are connected to the input port 17b of the microcomputer 17. Main unit key 20, microcomputer 17, and E
EPROM 18 functions as hue adjusting means.

Further, the liquid crystal display device 25 is provided with a personal computer 32, a measuring device 33 and an RS23 as communication means with the outside.
Communication port 21 for connecting a communication cable such as 2C
Is provided. The measuring device 33 receives projection light output from a projection lens (not shown) of the optical system 16, measures x and y values of the projection light on an xy chromaticity diagram, and converts the measured data. It is sent to the microcomputer 17 via the communication port 21.

The microcomputer 17 exchanges data with the EEPROM 18 through the input / output port 17a.
The communication port 21 is connected to the input / output port 17c, and further outputs a gamma curve data signal s11 for performing signal correction described later to the image quality improvement processing unit 6 from the output port 17d.

The signal generator 22 receives a command signal s16 output from the microcomputer 17 during hue adjustment described later,
The white signal for adjustment is sent to the selectors 26, 27, 28.

FIG. 2 is a block diagram showing the internal structure of the image quality improvement processing unit 6, and each of the R, G, and B gamma correction units 6a, 6b.
b and 6c take in the gamma curves ΓR, ΓG, and 作成 B created by the microcomputer 17 by the hue adjustment described later, and input s4, s5, and s6 to the respective gamma curves ΓR,
で G and ΓB, and the corrected color signals s7, s8,
It functions as an image quality improving unit that outputs s9. The output signals s7 to s9 are supplied to D / A converters 7 to 9.

As described later, the number storage area 18b and the shift value storage area 18c of the EEPROM 18
The numbers of three gamma curves and three shift values are stored in order to prepare individual gamma curves for each of the gamma correction units 6a, 6b and 6c. .

The n types of gamma curves Γm (1 ≦ 1) stored in the gamma table storage area 18a of the EEPROM 18
m ≦ n), as shown in FIG. 3, the output levels corresponding to, for example, an input level of 50% coincide with each other, and the level of each output level is reversed at the boundary of this input level. It is set to converge to a value.

The characteristics of the gamma curve are as follows.
Gamma curve with the lowest output level in the area of less than 1%
From the gamma curve Γn with the highest output level in the same area
Up to this point, the n pieces of gamma curves Δm change stepwise. Further, even in a region where the input level is 50% or more, the characteristics similarly change stepwise.

The shift value storage area 18c stores data from + h to -h
The shift values selected by the method described later from the s shift values v set at equal intervals are stored. FIG. 4 shows a change in the gamma curve Δm shifted by the stored shift value.

When shifting the gamma curve, 0%
And the output values of 100% are fixed.

Therefore, the shift of the gamma curve in the case where the output level with respect to the input level is adjusted in increments of 5% is performed when the input level of the video signal is in the range of 5% to 95%, and 0 to 5% and 95%. The range from to 100% is, for example, connected by a straight line.

Next, the procedure for manually adjusting the hue will be described with reference to the xy chromaticity diagram shown in FIG.
This adjustment is performed by transmitting a communication command for directly changing the gamma curve from the personal computer 32 via the communication port 21 to the microcomputer 1.
7 or the menu required for adjusting the gamma curve is called on the projected image by the remote controller 31 or the main body key 20, and the menu is executed by, for example, selecting a numerical value from the menu.

The hue adjustment is performed according to the following procedure. In this initial state, the gamma correction units 6a, 6b, 6c (FIG. 2) of the image quality improvement processing unit 6 use the projector with a shift value of zero in advance. A gamma curve Δm corresponding to the average characteristics of the liquid crystal panel is taken. The following adjustment procedure is an example of a procedure for adjusting the hue using the signal generator 22 inside the liquid crystal display device 25. When connecting a signal generator externally to adjust hue, the signal generator 22 is not used. The following adjustment procedure is an example when the initial chromaticity is at the position shown in FIG.

(1) A 50% white signal is output from the signal generator 22, and the x and y values of the chromaticity of the projection light projected from the projection lens of the optical system 16 are checked by the measuring device 33. (2) In order to adjust the gamma curve used in the gamma correction unit 6c (FIG. 2) for B, the shift value vb stored in the shift value storage area 18c is sequentially increased (down), and the gamma is adjusted as shown in FIG. The level of the curve #m is sequentially shifted up (shifted down) to lower (increase) the chromaticity y value, and only the y value is within the adjustment range (see FIG. 6), and the shift value vb at this time is stored in the shift value. It is stored in the area 18c. (3) In order to adjust the gamma curve used by the gamma correction unit 6a for R, the shift value vr stored in the shift value storage area 18c is sequentially reduced (up), and the level of the gamma curve Γm is increased as shown in FIG. Are sequentially shifted down (shifted up) to lower (increase) the chromaticity x value, and put only the x value within the adjustment range (see FIG. 6), and store the shift value vr at this time in the shift value storage area 18c. Let it.

(4) If both the x value and the y value are within the adjustment range, go to (9). (5) If only the x value is not within the adjustment range (3)
repeat. (6) If only the y value is not within the adjustment range (2)
repeat. (7) If both x value and y value are within the adjustment range (9)
Proceed to. (8) If both the x value and the y value are not within the adjustment range, repeat steps (2) to (7). The above procedures (1) to (8) are the same as the conventional method, except that the output values of 0 and 100% are not shifted in the shift of the gamma curve.

(9) An a% white signal is output from the signal generator 22, and the x and y values of the chromaticity of the projection light projected from the projection lens of the optical system 16 are checked by the measuring device 33.
(A is 10 if adjusting the darker part than 50% white
Use a value of ~ 40, and use a value of 60 ~ 90 to adjust areas brighter than 50% white)

(10) The y value is larger (smaller) than the value in the adjustment range.
If the value of a selected in (9) is in the range of 10 to 40, the gamma curves of B {m + 1 to {n ({m-1 to {
1) are sequentially selected, and the y value is decreased (increased), and the number of the gamma curve at which the color difference from the adjustment value is minimized is stored in the number memory 18b (see FIG. 6). (11) When the y value is larger (smaller) than the value in the adjustment range,
If the value of a selected in (9) is in the range of 60 to 90, the gamma curve of B Γm-1 to Γ1 (Γm + 1 to Γn)
The gamma curve number at which the color difference from the adjustment value is minimized is stored in the number memory 18b (see FIG. 6).

(12) The x value is larger (smaller) than the value in the adjustment range.
If the value of a selected in (9) is in the range of 10 to 40, the gamma curve of R {m-1 to {1 ({m + 1 to {1})}
The numbers are sequentially selected up to n), and the x value is reduced (increased), and the number of the gamma curve that minimizes the color difference from the adjustment value is stored in the number memory 18b (see FIG. 6). (13) When the x value is larger (smaller) than the value in the adjustment range,
If the value of a selected in (9) is in the range of 60 to 90, the gamma curve of R Γm + 1 to Γn (Γm-1 to Γ1)
The gamma curve number at which the color difference from the adjustment value is minimized is stored in the number memory 18b (see FIG. 6).

Thus, the manual hue adjustment is completed. During a normal operation for processing a video signal, the microcomputer 1 shown in FIG.
7 reads the gamma curve number mb stored in the number storage area 18b, and the corresponding gamma curve #mb
Is called from the gamma table storage area 18a, and the gamma curve ΓB created by adding the shift value vb stored in the shift value storage area 18c to this is sent to the gamma correction unit 6c in FIG. Then, the input digital B signal s6 is corrected by the gamma curve ΓB, and the corrected G color signal s9 is output.

Similarly, the microcomputer 17 reads the gamma curve number mr stored in the number storage area 18b, calls the corresponding gamma curve Γmr from the gamma table 18a, and stores it in the shift value storage area 18c.
The gamma curve ΓR created by adding the shift value vr stored in the register G is sent to the R gamma correction unit 6a in FIG. Then, the input digital R signal s
4 is corrected by the gamma curve ΓR, and the corrected R color signal s7 is output.

As for the G signal, the digital G signal s5 input to 6b in FIG. 2 is corrected by the gamma curve Γm of the gamma table 18a, and the corrected G color signal s8 is output.

In the adjustment procedure shown in this embodiment, if all the gamma curves of R, G, and B are adjusted in the xy chromaticity coordinate system of FIG. 6, the values fall within the adjustment range. Takes a very long time, so the G gamma curve of G is fixed and the adjustment is performed by focusing only on the gamma curves of B and R. However, the gamma curve of B is fixed and the gamma curve of R and G is adjusted. The adjustment may be performed alone.

Next, automatic hue adjustment will be described. The automatic hue adjustment includes two methods: a method of executing the automatic adjustment program incorporated in the personal computer 32 and a method of incorporating the automatic adjustment program in the ROM 34 inside the liquid crystal display device 25 and executing the program.

In the automatic adjustment method using a personal computer, first, the personal computer 32 inputs the measurement data output from the measuring device 33 through the communication port 21 of the liquid crystal display device 25, and displays the projection light on the xy chromaticity diagram. Monitor the x, y values. The automatic adjustment program incorporated in the personal computer 32 is incorporated so as to execute the above manual adjustment steps (1) to (13) as they are, and the personal computer 32 controls the microcomputer 17 in accordance with the program. The automatic hue adjustment is performed by sending a signal through the communication port 21.

Similarly, in the automatic adjustment method without using a personal computer, the microcomputer 17 inputs the measurement data output from the measuring device 33 through the communication port 21 of the liquid crystal display device 25, and displays the data on the xy chromaticity diagram of the projection light. Monitor the x and y values of. RO
The automatic adjustment program incorporated in M34 is incorporated so as to execute the above manual adjustment steps (1) to (13) as they are, and the microcomputer 17 executes automatic hue adjustment according to this program.

In the automatic adjustment method using a personal computer,
The personal computer 32 corresponds to control processing means for controlling the hue adjusting means so as to automatically perform hue adjustment, and the measuring device 33 corresponds to hue information measuring means for measuring hue information of a projected image.

[0050]

According to the first aspect of the present invention, the gamma curve is shifted while the levels of the R, G, and B signals are fixed at 0% and 100%. Can always be kept constant.

According to the second aspect of the present invention, there is an effect that it is possible to adjust the hue variation of a plurality of levels.
As compared with the conventional method of adjusting the hue of only the level, a projection-type liquid crystal display device having less variation in the hue of the set solid in mass production can be supplied stably.

According to the third aspect of the present invention, the adjustment can be performed promptly by selecting one of a plurality of gamma curves having different characteristics stored in the table.

According to the fourth aspect of the present invention, the time for the hue adjustment can be greatly reduced by automating the hue adjustment.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a projection type liquid crystal display device showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration circuit of an image quality improvement processing unit 6.

FIG. 3 shows a gamma table storage area 18a of a ROM 18.
FIG. 7 is a characteristic diagram showing characteristics of a plurality of gamma curves stored in FIG.

FIG. 4 is a characteristic diagram showing a characteristic change of a gamma curve shifted by a value of a shift value storage area 18c of a ROM 18.

FIG. 5 is a characteristic diagram showing variations in VT characteristics of a liquid crystal panel.

FIG. 6 is a diagram showing an image of hue adjustment on xy chromaticity coordinates.

FIG. 7 is a diagram illustrating an image of a shift of a gamma curve.

[Explanation of symbols]

Reference Signs List 1 signal input unit, 2 A / D converter, 3 A / D converter, 4 A / D converter, 5 digital signal processing unit, 6 image quality improvement processing unit, 6a R gamma correction unit, 6b G gamma correction Unit, 6c B gamma correction unit, 7 D / A converter, 8 D / A converter, 9
D / A converter, 10 drive circuits, 11 drive circuits, 12 drive circuits, 13 R liquid crystal panel, 1
4G liquid crystal panel, 15B liquid crystal panel, 16
Optical system, 17 microcomputers, 18 EEPROM,
18a gamma table storage area, 18b number storage area, 18c shift value storage area, 19 remote control light receiving section, 20 main body key, 21 communication port, 22
Signal generator, 26 selector, 27 selector, 28 selector, 31 remote controller, 32
PC, 33 measuring instrument, 34 ROM.

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Claims (4)

[Claims] 1. A light emitted from a light source means is incident on a plurality of liquid crystal light valve means, and a projection image emitted from an image forming surface of the liquid crystal light valve means is synthesized and projected on a screen via an optical system. In a projection type liquid crystal display device, hue adjusting means for individually correcting levels other than 0% and 100% of signals input to the plurality of liquid crystal light valve means with a predetermined characteristic curve, and utilizing the hue adjusting means. A projection type liquid crystal display device comprising: an image quality improving unit that corrects a color of a projected image. 2. A projection type liquid crystal display according to claim 1, wherein said image quality improving means adjusts the hues of a plurality of points using a gamma characteristic of a light valve having a fixed output value at a certain point of the input signal. Display device. 3. The image quality improving means prepares several kinds of light valve gamma curves having fixed output values at a certain point of an input signal, and selects an optimum gamma curve from among them. The projection type liquid crystal display device as described in the above. 4. A projection type liquid crystal display device according to claim 1, a hue information measuring means for measuring hue information of said projection image, and said hue adjustment for inputting said hue information and automatically performing hue adjustment. Control processing means for controlling the means.