JP3303412B2 - Gamma correction circuit, display device adjusting method, and display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly to a gamma correction circuit and a method for adjusting the same.

[0002]

2. Description of the Related Art FIG. 8 shows a conventional embodiment.

An input video signal 100 is an analog signal, is selected by a switching circuit 11, and is converted into a digital signal by an AD converter 1. Reference numeral 2 denotes a look-up table (hereinafter abbreviated as LUT), which is disclosed in Japanese Unexamined Patent Publication No. Hei 4-96579 or SID91 DIgest p.
high-Quality-Image EDTV Li
As described in “Quid-Crystal-Projector”, a conversion data table for input and output is written, and the difference between the gamma characteristic applied to the input video signal 100 in advance and the input / output characteristic of the display device 4 is determined. Used for correction and the like. Generally, LUT
2 is composed of storage elements such as EPROM and RAM,
The address bus is used as input and the data bus is used as output.
The output of the LUT 2 is returned to an analog signal by the DA converter 3 and is input to the display device 4 so that a video signal can be displayed. When adjusting gamma, the analog signal generator 10 generates a gray scale signal,
The gray scale is displayed on the display device 4 by switching with the switching circuit 11, and the contents of the LUT 2 are changed by the setting circuit 9 while observing the screen of the display device 4.

[0004]

However, in the circuit shown in the conventional example, the signal level of each step of the gray scale generated by the signal generator and the input digital value of the LUT equal to the level correspond to data. In many cases, it is difficult to adjust the level of any step of the gray scale displayed on the screen, because the temperature may shift due to changes in the ambient temperature or changes over time even if the measurement is taken. It took a lot of time with mistakes. In general, in order to simplify the adjustment, the LUT shown in FIG.
In the setting example 60, a plurality of adjustment points are determined like black circles, and the adjustment points are often set by broken line approximation. However, the break point, that is, the input level of the LUT corresponding to the adjustment point and the gray scale 61 Since the level of the step does not always match, for example, when trying to adjust the LUT while measuring the screen brightness of the display device, the level to be set at the adjustment point must be obtained by interpolation calculation of the measured value, which is complicated. In addition to the above, repetition was required to cause an error, which required a lot of time.

Further, when the gray scale is displayed on the entire screen of the display device, there is a problem that the shading of the display device affects the luminance distribution of the gray scale, so that accurate setting cannot be performed. In this case, if the gray scale is displayed small near the center of the screen, the influence of shading is reduced, but there is a problem that the scale of the signal generator increases. To avoid the influence of shading, a method of displaying a raster signal and measuring the luminance of one point on the screen while changing the signal level is also possible, but much more time is required.

Further, since the gray scale and the input video signal cannot be displayed at the same time, it is necessary to frequently operate the switching circuit 11 to adjust the result of the gray scale adjustment while confirming the result with the input video signal. Was.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a gamma correction using a look-up table.
Switching means connected to the input of the table;
Signal generating means connected to the stage, and switching means for the signal generating means
The output from the signal generation means connected to the stage and the input video signal
Signal switching means so that
Timing generation means for outputting a signal to be controlled, and signal generation
A synchronizing means for synchronizing the means and the timing generating means with the input video signal.

In addition, the present invention is characterized in that a signal input to the look-up table is adjusted while performing switching display in synchronization with an input video signal.

[0009]

【Example】

(Embodiment 1) FIG. 1 shows a first embodiment according to the present invention. In this figure, the same reference numerals as those in FIG. 8 showing the conventional example indicate the same functions.

The input video signal 100 is an analog signal,
The signal is converted into a digital signal by the D converter 1, selected by the switching circuit 5, and input to the LUT 2. Here, the output of the AD converter 1, the input of the switching circuit 5, and the input of the LUT 2 have the same number of bits, and are composed of, for example, 8 bits.
The contents of the LUT 2 can be changed by the setting circuit 9. The output of the LUT 2 is returned to an analog signal by the DA converter 3 and is input to the display device 4 for display. On the other hand, in the sync separation circuit 6, the input video signal 100
01 is separated and input to the timing circuit 7. Here, it is clear that the synchronization signal may be directly input to the timing circuit 7 without passing through the synchronization separation circuit 6 for a signal such as a computer signal in which the synchronization signal is separated in advance. From the timing circuit 7, a timing signal 102 is connected to the counter 8, and a switching signal 103 is connected to the switching circuit 5. The output of the counter 8 is a 4-bit gray scale signal 104,
The upper four bits (D7 to D4) 21 of the switching circuit 5 are connected. Also, the lower 4 bits (D
3 to D0) 22 are connected to the ground.

FIGS. 2 and 3 are timing charts showing the operation timing of FIG. FIG. 2 shows a vertical cycle, and a vertical synchronizing signal 101a constituting the synchronizing signal 101.
It operates with the cycle of. As shown, the timing signal 102 and the switching signal 103 become high level in a part of the vertical cycle. FIG. 3 shows the horizontal period, in which the period in which the timing signal 102 and the switching signal 103 in FIG. 2 are at the high level is enlarged and shown. ing. The timing signal 102 becomes high level in a part of the horizontal cycle as shown in FIG. The switching signal 103 goes high in synchronization with the timing signal 102, and switches the switching circuit 5 to the counter 8 during this period, and switches to the output side of the AD converter 1 during the other periods. The gray scale signal 104 shown in FIG. 3 indicates the output of the counter 8, and as shown in FIG.
Four bits D6, D5, and D4 are output, and the timing signal 102 counts up during a high level period.
It is reset by the horizontal synchronization signal 101b.

With the configuration described above, when the timing signal 102 is at a high level, the switching circuit 5
In hexadecimal notation, 0, 10H, 20H, 30H, 40
H, 50H, 60H, 70H, 80H, 90H, A0
Gray scale signals of 16 steps of H, B0H, C0H, D0H, E0H, and F0H are input.

FIG. 4 shows a screen of the display device 4. As shown in the figure, the grayscale signal 50 corrected by the LUT 2 is displayed only during the period when the timing signal 102 is at the high level, and the input video signal 100 is
The video signal 51 corrected in step is displayed.

After the adjustment is completed, the switching circuit 5
By fixing to the output side of the converter 1, the video signal 51 is also displayed in the portion where the gray scale signal 50 has appeared.

(Embodiment 2) FIG. 5 shows a second embodiment according to the present invention. Note that the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The output of the timing circuit 7 is connected to the counter 8 as a timing signal 105, and is connected to the lower four bits (D3 to D0) 22 of one input of the switching circuit 5 as a timing signal 106. Other configurations are the same as those in FIG.

FIG. 6 is a timing chart showing the operation of this embodiment in a horizontal cycle. The operation in the vertical cycle is the same as that in FIG. 2 describing the first embodiment. FIG. 6 shows FIG.
The period during which the timing signal 102 and the switching signal 103 of FIG.
It operates with a period of 01b. Timing signal 105
Becomes high level in a part of the horizontal period as shown in FIG. The switching signal 103 becomes a high level in synchronization with the timing signal 105. During the high level, the switching circuit 5 is switched to the counter 8 side.
In other periods, the operation of switching to the output side of the AD converter 1 is performed. The counter 8 counts up as described in the first embodiment, but the switching signal 103 is maintained at the high level for a period equivalent to one count even after the counter 8 has reached the full count. The timing signal 10
No. 6 is at a high level for a period equivalent to this one count.

With such a configuration, the timing signal 1
During the high level period of 05, the switching circuit 5
In decimal notation, 0, 10H, 20H, 30H, 40H, 5
0H, 60H, 70H, 80H, 90H, A0H, B0
H, C0H, D0H, E0H, and F0H are input, and while the timing signal 106 is at a high level, FFH is input, and a total of 17 steps of grayscale signals are input.

FIG. 7 shows a screen of the display device 4. As shown in the figure, only during the period when the timing signals 105 and 106 are at the high level, the gray scale signal 5 corrected by the LUT 2 is used.
2 is displayed, and the input video signal 100 is
The signal 51 corrected at T2 is displayed.

In the first and second embodiments, the AD
The case where the converter 1, the switching circuit 5, and the LUT 2 are composed of 8 bits and the output of the counter 8 is 4 bits has been described. Further, only the case where the input video signal has one system has been described, but it is apparent that the configuration with three systems can support a color signal.

[0021]

As described above, according to the present invention,
The signal level of the gray scale Ru is displayed can in grasped as a digital value, just observing the gray scale is displayed, it allows the input values should be adjusted LUT, it is possible to short the adjustment. In particular, when setting the LUT by the polygonal line approximation, since the adjustment point and the level of each step of the gray scale can be matched, the adjustment can be performed while measuring the luminance of the display device. There is an excellent point that only one adjustment is required. In addition, even if interpolation calculation takes time to approximate between the adjustment points with a higher-order curve, it is possible to adjust only the level of each step of the gray scale first, and then perform the interpolation calculation after adjustment. There is an advantage that the adjustment time can be shortened.

Further, by setting the timing circuit and the counter, it becomes possible to display, for example, a gray scale in an arbitrary size at an arbitrary place on the screen of the display device .
For example, by performing a relatively small display at the center of the screen, even if shading has occurred on the display device, it is possible to make adjustments while avoiding the effect. In this case, it can be realized with a much smaller circuit configuration than when a signal generating means is provided at the input of the AD converter.

Furthermore, at the same time as the gray scale, because can display by correcting the input video signal by the LUT output, the adjustment result by the gray scale, the effect at the same time can be grasped on the input video signal, as in the prior art switching circuit This eliminates the need for complicated operations such as frequent switching and comparison.

[Brief description of the drawings]

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

FIG. 2 is a timing chart illustrating the operation of the present invention.

FIG. 3 is a timing chart illustrating the operation of the present invention.

FIG. 4 is a diagram illustrating a screen display according to the present invention.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is a timing chart illustrating the operation of the present invention.

FIG. 7 is a diagram illustrating a screen display according to the present invention.

FIG. 8 is a block diagram showing a conventional example.

FIG. 9 is a diagram showing data and a gray scale of a conventional lookup table.

[Explanation of symbols]

 Reference Signs List 1 AD converter 2 Look-up table 3 DA converter 4 Display device 5 Switching circuit 6 Synchronization separation circuit 7 Timing circuit 8 Counter 9 Setting circuit 11 Switching circuit 21 Upper bit 22 Lower bit 50 Gray scale 51 Video signal 52 Gray scale 60 Look-up table Data 61 gray scale 100 input video signal 101 synchronization signal 101a vertical synchronization signal 101b horizontal synchronization signal 102 timing signal 103 switching signal 104 gray scale signal 105 timing signal 106 timing signal

Claims (12)

(57) [Claims] 1. A signal switching means for selectively switching the output and the output from the signal generating means and an input video signal, the lookup table output of the switching means are entered, the signal generating means and the switching means the signal is connected to the bets
The output from the generating means and the input video signal are simultaneously displayed on the screen.
A signal for controlling said signal switching means as displayed in
A timing generating means for outputting a gamma correction circuit, characterized in that the said timing generating means and said signal generating means and a synchronization means for synchronizing with the input signal. 2. The gamma correction circuit according to claim 1, wherein the number of output bits of said signal generating means is set smaller than the number of input bits of said look-up table. The number of input bits wherein the switching means, the number of output bits of said switching means, becomes the set number of input bits are equal to the lookup table, the switching
Input from the signal generating means of the means from the upper bit
3. The gamma correction circuit according to claim 2 , wherein the outputs of said signal generating means are connected in sequence, and the remaining bits of the input from said signal generating means of said switching means are connected to the same specific potential. 4. The apparatus according to claim 1, further comprising means for changing the specific potential in accordance with a display position of a display device.
3. The gamma correction circuit according to 3 . 5. A control method of a display device for displaying performs gamma correction on an input video signal, in synchronism with the input video signal and an input from the input video signal and the signal generating means switching
Input to switching look-up table by means of a signal from said signal generating means and said input video signal on a screen
A method of adjusting a display device, wherein the contents of the look-up table are changed while displaying simultaneously . 6. The adjustment method for a display device according to claim 5, wherein the number of output bits of said signal generating means is set smaller than the number of input bits of said look-up table. The number of input bits wherein said switching means, the number of output bits of said switching means, is set equal to be the number of input bits of the look-up table, the switching
The input from the signal generating means of the means is in order from the upper bit.
Said output signal generating means is connected, the remaining bits of the input from the signal generating means of said switching means is characterized by comprising connected to the same specific potential to claim 6
The adjustment method of the display device according to the above. 8. A display method according to claim 7 display apparatus, wherein by comprising varied depending on the display position of the display specific potential device. 9. A display device for displaying an input video signal after subjecting the video signal to gamma correction and selectively switching between an output from a signal generating means and the input video signal, and said switching means. and a look-up table which outputs are are entered, the signal generating means and the switching means
It said input movies and output from the signal generating means is connected to the bets
Switch the signal so that the image signal and the image signal are simultaneously displayed on the screen
A display device, comprising: a timing generating means for outputting a signal for controlling the signal generating means; and a synchronizing means for synchronizing the signal generating means and the timing generating means with the input signal. 10. The number of output bits of said signal generating means is:
10. The display device according to claim 9, wherein the number of input bits is set to be smaller than the number of input bits of the lookup table. 11. The switching means, wherein the number of input bits of the switching means, the number of output bits of the switching means , and the number of input bits of the look-up table are set to be equal.
Input from the signal generating means in order from the upper bit
The output of the signal generating means is connected and is provided before the switching means.
11. The display device according to claim 10, wherein the remaining bits of the input from said signal generating means are connected to the same specific potential. 12. The display device according to claim 11, further comprising means for changing the specific potential according to a display position of the display device.