JPH08317322A - Multi-screen display system - Google Patents

Abstract

PURPOSE: To eliminate nonuniform luminance between respective display devices at the time of performing multi-picture display using a display device, in which display luminance is changed with an APL, by finding the APL to be displayed on the respective display devices and controlling a video signal level with the maximum APL of those APL as a reference. CONSTITUTION: A video signal is subjected to multi-screen signal processing, and that video signal is displayed on a display part 4 of a PDP, etc., while controlling the signal level at a signal level control part 3. A luminance signal is found by a matrix 5, the APL for each frame or the like is found, and the APL averaged for a fixed period is provided by a control part 7 or the like. The maximum APL is found from that APL and the APL of the other display device provided through a bus S2 by a signal level coefficient processing part 11 or the like. The display rate of the maximum APL is calculated from the characteristics of a display rate to APL found in advance, the rate of an output signal level to provide the same display corresponding to the input signal level of each APL is found, the signal level control part 3 is controlled with this rate as a signal level coefficient, and the display luminance level is displayed equally as the display part of the maximum APL.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-screen display system which is capable of displaying a large-screen image using a plurality of display devices and which has improved uneven brightness.

[0002]

2. Description of the Related Art Generally, in a display device using a CRT, a PDP (plasma display panel), etc., in order to suppress the maximum power consumption, the display brightness is changed according to the APL (average video level) of the input video signal, and the APL is increased. In this case, it is provided with a function such as APC (Automatic Power Control) that reduces the display brightness for the same input signal level. Therefore, when a plurality of such display devices are collected for multi-screen display, even if the input signal levels are the same, the display brightness will be different if the APLs are different, which causes the problem that the display brightness becomes uneven on the entire display screen. is there.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and even when multi-screen display is performed using a display device having an APC or the like, uneven brightness occurs between the display devices. It is to construct a multi-screen display system without any problems.

[0004]

APL calculation means for calculating APL (average video level) of a video signal displayed on each display device, comparison means for each APL, and video signal level input to the display device. A control means is provided, and by controlling the video signal level input to each display device by each APL, the uneven brightness between the display devices whose display brightness changes depending on the input APL is corrected.

The APL calculation period is a plurality of frame periods or a plurality of field periods, and the APL is updated in a period shorter than the plurality of frame periods or the plurality of field periods.

The APL calculation period is matched with the response time of the display luminance change by the APL of the display device.

The number of registers equal to the number of APL updates within the APL calculation period is provided, each register is circularly accessed for each APL update, and the value of the accessed register is subtracted from the APL to obtain the updated value of the APL. By writing to the register and adding to the desired APL,
Calculate APL.

The APL is calculated by accumulating and averaging video signals corresponding to one pixel among a plurality of display pixels on the display screen.

The APL is calculated by accumulating and averaging only the upper bits of the corresponding digital video signal.

The APL is calculated using the video signal of one frame or one field selected from a plurality of frames or fields.

The video signal level input to the display device is calculated from an approximate expression of APL vs. display brightness obtained in advance with reference to the video signal corresponding to the maximum APL by comparing each APL.

The APL input to the display device is interpolated with reference to a table of APL vs. display luminance obtained in advance with reference to the video signal corresponding to the maximum APL by comparing each APL.

[0013]

APL calculation means for calculating the APL (average video level) of the video signal displayed on each display device, and each AP
By providing L comparing means and video signal level control means for inputting to the display device, and controlling the video signal level input to each display device by each APL, it is possible to correct the luminance unevenness between the display devices. Even when performing multi-screen display on a display device whose display brightness changes depending on the input APL, it is possible to eliminate the brightness unevenness between the display devices.

The calculation period of the APL is a plurality of frame periods or a plurality of field periods, and by updating the APL in a period shorter than the plurality of frame periods or the plurality of field periods, it is possible to cope with a display device having a response time in APC or the like. become.

By adjusting the calculation period of the APL to the response time of the display luminance change by the APL of the display device, it becomes possible to correct the luminance unevenness that matches the characteristics of the display device.

The number of registers equal to the number of APL updates within the APL calculation period is provided, each register is circularly accessed for each APL update, and the value of the accessed register is subtracted from the APL to obtain the updated value of the APL. Is written in the register and added to the desired APL to calculate the APL, so that the accurate APL calculation of the response can be easily performed.

The APL is calculated by accumulating and averaging video signals corresponding to one pixel among a plurality of display pixels on the display screen, and utilizing the correlation of the video signals in the display screen. The scale of the APL calculation means can be reduced without lowering the accuracy.

The APL can be calculated by accumulating and averaging only the upper bits of the corresponding digital video signal, thereby avoiding the influence of noise on the video signal.
The scale of the APL calculation means can be reduced.

The APL is calculated using a video signal of one frame or one field selected from a plurality of frames or fields, so that the APL can be calculated without lowering the accuracy by utilizing the correlation in the time axis direction of the video signal. The operating speed of the calculation means can be reduced.

The video signal level to be input to the display device is calculated by an approximate expression of APL vs. display brightness obtained in advance with reference to the video signal corresponding to the maximum APL by comparing each APL. A fast processing means is obtained.

The APL input to the display device is simply calculated by comparing each APL with the video signal corresponding to the maximum APL as a reference and interpolating by referring to a table of APL vs. display luminance obtained in advance. Thus, it is possible to obtain a processing means capable of handling any display characteristic.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-screen display system according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of a brightness nonuniformity correction unit of one display device of one embodiment of a multi-screen display system according to the present invention. Analog video signal S
1 is digitized by an analog / digital converter 1 and a multi-screen signal processing unit 2 enlarges a required video signal portion and the like, and a signal level control unit 3 controls a signal level in accordance with APL so that a PDP or the like can be obtained. It is displayed on the display unit 4. On the other hand, the video signal composed of the three primary colors of R, G, B of the display video signal of the display device is used as the luminance signal in the matrix 5, and the APL for each frame or each field is calculated by the APL calculator 6. In accordance with the procedure of the APL processing unit 10, the control unit 7 cyclically accesses, for each frame or each field, the registers provided in the storage unit 9 by the number obtained by dividing the APL calculation period by the frame period or the field period. The value of the accessed register is read, the value is subtracted from the APL register of the desired period provided at another address of the storage unit 9, and the value obtained by the APL calculator 6 for each frame or each field is taken in. Write to the accessed register. AP for each same frame or each field
L is added to the APL register provided in the storage unit 9 for the required period. In this way, the APL register of the storage unit 9 is updated for each frame or field averaged during the period required by the video signal displayed on the display device.
Get.

The control unit 7 further calculates the APL of the video signal to be displayed on the display device and other display devices constituting the multi-screen display system in the same manner as described above in accordance with the processing procedure of the signal level coefficient processing unit 11. APL that takes in the maximum APL via the APL data bus S2
Ask for. The maximum display rate of the APL is calculated from the previously obtained characteristics of the APL versus the display rate, and the ratio of the output signal level having the same display rate with respect to the input signal level in the APL of the display device is calculated. Is used as a signal level coefficient and the signal level control unit 3 is controlled so that the display brightness level is the same as that of the display unit having the maximum APL. Here, the display rate means the display brightness of the white peak in an arbitrary APL with respect to the display brightness of the white peak where APL is close to zero.

FIG. 2 is an example of a line graph showing the approximate characteristics of the display rate for each APL in one embodiment of the multi-screen display device according to the present invention. Since the power consumption is small where the APL is small, APC is not applied and the display rate becomes approximately 1 indicated by the straight line C1. APC is applied at a certain Ac value Ac or higher,
When the power consumption is suppressed to a substantially constant value, the display rate decreases and the curve becomes C2. The display rate corresponding to the value Am of the maximum APL is Pm.
And When the APL of the display device is smaller than Ac, the control unit 7 of FIG. 1 outputs the value of Pm to the signal level control unit 3 including a multiplier or the like, and the input signal receives the coefficient Pm.
By multiplying by m and displaying the output signal on the display unit 4, the display ratio becomes the same as that of the display device that displays the maximum APL. When the APL of the display device is larger than Ac, the approximate expression of the curve C2 is obtained, and the signal level such that the display rate for the input signal, which is the total of the display rate reduction and the signal level reduction due to APC, is equal to Pm. The coefficient is obtained, and the signal level control unit 3 is controlled in the same manner as described above to match the display brightness with the maximum APL display unit.

As another method of obtaining the signal level coefficient, the table of the APL vs. signal level coefficient is stored in the storage unit 9 of FIG. 1 for each maximum APL previously obtained from the experimental value, and the maximum APL and the corresponding display are stored. It can also be obtained from the APL of the apparatus by interpolation calculation using the table.

Next, for example, how to apply APC in a PDP is determined by the heat radiation characteristics of the PDP, and therefore generally has a considerably long response time compared to the frame period. The AP
By combining the calculation period of L with this response time, it is possible to prevent the occurrence of uneven brightness due to time lag.

A for each frame or field in FIG.
The PL calculator 6 is composed of an adder and a register, takes the cumulative sum of the luminance signals corresponding to each display pixel, and can use the value as the denormalized APL.

A for each frame or field in FIG.
The PL calculator 6 may be composed of an adder and a register, and may take a cumulative sum from the luminance signals corresponding to one display pixel among a plurality of display pixels, and use the value as a denormalized APL.

A for each frame or field in FIG.
The PL calculator 6 is composed of an adder and a register, and can also obtain the APL by taking the cumulative sum of only the upper bits of the digital video signal.

A for each frame or field in FIG.
The PL calculator 6 can also calculate the APL for a period in which the control unit 7 takes a cumulative sum once for several frames or fields and fetches the data in accordance with it.

[0031]

As described above, in a multi-screen display system that performs enlarged display using a plurality of display devices, the APL displayed on each display device is calculated, and the input signal in each display device is adjusted. , A with the maximum display rate for the input signal
By making the display rate of the display device that displays PL the same,
A multi-screen display system having no brightness unevenness can be configured even if a display device having a characteristic in which the display rate varies depending on the APC or the like is used.

[Brief description of drawings]

FIG. 1 is a first embodiment of a multi-screen display device according to the present invention.
It is a block diagram of a brightness unevenness correction unit of one display device.

FIG. 2 is an example of a line graph showing the approximate characteristics of the display rate for each APL in one embodiment of the multi-screen display device according to the present invention.

[Explanation of symbols]

 1 analog / digital converter 2 multi-screen signal processing unit 3 signal level control unit 4 display unit 5 matrix 6 APL calculator for each frame or field 7 control unit 9 storage unit 10 APL processing unit 11 coefficient processing unit S1 analog video signal S2 APL data bus

Claims (9)

[Claims] 1. A multi-screen display system for dividing one image into a plurality of display devices for display, and APL calculation means for calculating an APL (average image level) of a video signal displayed on each display device, and each of the APL calculation means. A comparison means between APLs and a control means for controlling a video signal level input to the display device are provided,
A multi-screen display system characterized by correcting unevenness in brightness between display devices whose display brightness changes depending on the input APL by controlling a video signal level input to each display device by the APL. 2. The multi-screen display according to claim 1, wherein the APL calculation period is a plurality of frame periods or a plurality of field periods, and the APL value is updated in a period shorter than the plurality of frame periods or the plurality of field periods. system. 3. The APL calculation period is the APL of the display device.
3. The multi-screen display system according to claim 2, wherein the multi-screen display system is adapted to match the response time of the change in display brightness. 4. A number of registers equal to the number of APL updates within the APL calculation period are provided, each register is circularly accessed for each APL update, and the value of the accessed register is subtracted from the APL to obtain the value of the APL. 4. The multi-screen display system according to claim 2, wherein the APL is calculated by writing the updated value in the register and adding it to the desired APL. 5. The APL is calculated by accumulating and averaging video signals corresponding to one pixel among a plurality of display pixels on a display screen. The multi-screen display system according to claim 3 or 4. 6. The APL is calculated by accumulating and averaging only the upper bits of the corresponding digital video signal, claim 1, claim 2, claim 3, claim 4, or claim 4. The multi-screen display system according to claim 5. 7. The APL is calculated using only a video signal of one frame or one field selected from a plurality of frames or fields.
Claim 2, Claim 3, Claim 4, Claim 5 or Claim 6
The described multi-screen display system. 8. The video signal level input to the display device is
Comparing each APL, the video signal corresponding to the maximum APL is used as a reference, and the APL is calculated from an approximate expression of the display luminance, which is obtained in advance. The multi-screen display system according to claim 4, claim 5, claim 6, or claim 7. 9. The APL input to the display device is each APL.
3. A comparison is made with reference to a table of APL vs. display luminance data which has been obtained in advance, with reference to a video signal corresponding to the maximum APL, and interpolation calculation is performed. The multi-screen display system according to claim 4, claim 5, claim 6, or claim 7.