JP2001331144A - Video signal processing device, display device, projector, display method, and information storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high quality picture display by optimal driving irrespectively of temperatures and external conditions. SOLUTION: A video signal processing device expressing gradations according to an ON-time in the time-base direction in one frame period of a display device has a means for varying the number of gradations in the time-base direction and varying the number of gradations in the direction of the space for spatially expressing the gradations.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing device, a display device, a projector, a display method, and an information storage medium. , A display device, a projector, a display method, and an information storage medium.

[0002]

2. Description of the Related Art In a display device capable of binary display, a display that expresses multiple gray scales by performing time-division driving with subframes and spatial and temporal pseudo gray scale processing (dither, error diffusion, etc.). Examples of the device include a digital micromirror device (DMD), a ferroelectric liquid crystal display, and a plasma display panel (PDP).

In a single-panel system, a multi-grayscale display is realized by switching between RGB light sources or by combining a color wheel and spatial and temporal pseudo-grayscale processing, as in the field sequential system. There is.

JP-A-8-214243 and JP-A-8-214244 disclose an error diffusion filter for performing spatial pseudo multi-grayscale processing for a DMD (digital micromirror device).

Japanese Patent No. 2817597 (Fujitsu General Co., Ltd.) discloses a method of switching between direct input of a personal computer video signal and input via error diffusion for display.

[0006]

However, in the above prior art, 1) In the case of a display device using a liquid crystal device, the response speed of the liquid crystal varies depending on the temperature. In the case of expressing a gradation by a pseudo multi-gradation processing, there is a problem that a response speed cannot be kept at a low temperature. 2) Further, in a digital driving method such as DMD in which digital data is directly input to a display device, a high bandwidth is required for transferring data, and noise and power consumption become problems. There has been a demand to switch the driving method according to the mode to be used.

[0007]

A video signal processing apparatus according to the present invention is a video signal processing apparatus which expresses a gray scale by an ON time in a time axis direction in one frame period of a display device. It is characterized by having means for varying the number of gradations and means for varying the number of gradations in the spatial direction for spatially expressing gradations.

In the above-mentioned video signal processing apparatus, it is preferable that the variable control is performed so that the number of gradations in the time axis direction is equal to the sum of the number of gradations in the space direction.

According to the present invention, 1) high-quality display can be performed by optimal driving regardless of temperature and external conditions. 2) Since the driving method can be changed according to the application such as a low power consumption mode, power consumption and noise can be reduced.

A display device and a projector according to the present invention use the video signal processing device according to the present invention.

A display method according to the present invention is characterized in that a temperature near a display device is measured, and the number of gradations in the time axis direction and the number of gradations in the space direction are varied based on the measurement result. It is.

Further, the display method of the present invention is characterized in that the number of gradations in the time axis direction and the number of gradations in the space direction are varied according to a plurality of display modes of the display device.

An information recording medium according to the present invention stores a program describing the display method according to the present invention.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a functional block diagram of a first embodiment of the present invention.

In FIG. 1, 1 is a gamma conversion circuit, 2 is a first adder, 3 is a time / space gradation number switching section, 4 is an error diffusion section, and 5 is a vertical delay circuit (vertical delay section). , 6 are horizontal delay circuits (horizontal delay units), 7 is a second adder, 8 is a frame memory, 9 is a write control circuit (write control unit), 1
0 is a read control circuit (read control unit), 11 is a drive circuit, 1
Reference numeral 2 denotes a display device, here a liquid crystal device (LC
D).

The input video signal is subjected to various signal processing such as contrast, brightness, color conversion and enlargement / reduction by a DSP (Digital Signal Processor), and then input to the gamma conversion circuit 1. In the gamma conversion circuit 1,
De-gamma processing is performed on the gamma characteristic applied to the input signal in advance, and gamma processing is performed according to the characteristics of the display device.

FIG. 2A is a characteristic diagram showing an example of degamma processing, in which an input signal is converted into an inverse gamma characteristic in order to cancel the transmission gamma characteristic. Therefore, particularly, the signal component on the black side is compressed, so that the number of gradations is deteriorated, which causes image deterioration such as a false contour.

FIG. 2B shows an example of degamma according to the gamma characteristic of the liquid crystal device. As in the case of the transmission degamma, the compression of the signal component causes deterioration in the number of gradations.

The gamma conversion circuit 1 is set to have a degamma characteristic obtained by combining the transmission degamma and the degamma of the display device. Here, when the DMD is used, only the transmission degamma needs to be performed because the gamma characteristic of the DMD is linear.

Therefore, the gamma conversion circuit 1 constituted by a look-up table (LUT) such as a RAM reduces the number of gradations by increasing the number of output bits with respect to the number of input bits. It is devised so that it does not occur. For example, an address of 8 bits and data of 10 bits R
An input signal is input to an address and data is output using AM.

The 10-bit data output from the gamma conversion circuit 1 is added by the first adder 2 to the error data for the pixel being processed obtained from the error diffusion unit 4.

The error diffusion unit 4 compares the error with a threshold value for error calculation to determine an error to be diffused to neighboring pixels.

Next, the time / space grayscale number switching unit 3 serving as an error bit switching unit diffuses, as an error, grayscales equal to or greater than the number of grayscales to be displayed on the display device.

Data of the number of bits corresponding to the number of gradations of the display device is written into the frame memory 8.

The data is read from the frame memory 8 in accordance with the sub-frame of the display device, and the driving circuit 11
Liquid crystal display (LCD) 1 serving as a display device
2 is displayed.

Here, the read drive circuit 11 can change the number and ratio of subframes in one frame as shown below.

FIG. 3 shows the data sent to the display device and the ON state.
It is a timing chart which shows the relationship of time.

FIG. 3 (a) shows a case where display time of 8 bits (256 gradations) is represented by gradation by varying the ON time corresponding to each bit data. One frame period is assigned an ON time according to the weight of each bit from the MSB to the LSB. In the case of 8-bit data, the data is divided into eight sub-frames, and ７, ４, ８, 1/16, 1/32.
ON periods of 1/64, 1/128, and 1/256 are given. Here, assuming that one frame period is 16.6 ms (millisecond), the OSB given to the 0th bit which is the LSB is
The N time is only 65 μs (microsecond). In the case of the color sequential system, one frame period is set to RGB
, And is further reduced to 1/3 of 21.7 μs.

Here, when a liquid crystal display using FLC (ferroelectric liquid crystal) is used, the response speed at 50 ° C. is 10 μs, but the response speed at 20 ° C. is 60 μs.
s, and there is a problem that the ON time corresponding to the LSB cannot be satisfied.

FIG. 3B shows a case where the display data is 6 bits. In this case, the ON time given to the LSB is 259 μs in the case of the three-plate system and 86.4 μs in the case of the color sequential system. , 20 ° C. response time.

Therefore, by changing the number of gradations in the time axis direction, it is possible to perform control according to characteristics such as the response speed of the liquid crystal. Further, since the amount of data in the time axis direction can be reduced, there is an effect of reducing high-frequency noise and power consumption. Further, since the bus occupancy is reduced, the bus can be used effectively.

In the present invention, the number of gray scales adjusted in the time axis direction by the time / space gray scale number switching unit 3 is diffused in the spatial direction, so that the number of gray scales does not deteriorate.

FIG. 4 is a diagram showing an error diffusion process according to the present invention.

The pixel A is connected to the gamma conversion circuit 1 by 10
Output as bit data. Next, the adder 2 adds an error for the A pixel. Here, since the error increases the number of gradations in the LSB direction, the data output of the adder is 16 bits.

Next, in the time / space gradation number switching section 3, the gradation number in the time axis direction is written to the frame memory 8 as 8 bits, and the remaining 8 bits are inputted to the error diffusion section. Then, the 8-bit error generated in the pixel A is 1 /
Each four is diffused to each of B, C, D, and E pixels. Here, the diffusion of the error is performed by the vertical delay circuit 5 and the horizontal delay circuit 6.

FIG. 5 is an overall system block diagram of a projector according to a second embodiment of the present invention.

In FIG. 5, 51 is a light source, 52 is a first focusing lens, 53 is a color wheel, 54 is a second focusing lens, 55 is a DMD device, 56 is a zoom lens,
57 is a screen, 58 is a mode setting unit, 59 is a temperature sensor, 60 is a CPU, 61 is a signal processing unit (DS
P).

The light emitted from the light source 51 is focused by the first focusing lens 52 and is
3 is incident. The color wheel 53 is rotated by a motor and sequentially passes RGB light. The transmitted light is the second
The DMD chip 55 is irradiated by the converging lens 54. The DMD chip 55 controls the micromirror of each pixel according to the image driven by the signal processing unit 61,
The light emitted from the second focusing lens 54 is reflected according to the image data. The reflected image is projected on a screen 57 via a zoom lens 56.

Here, the signal processing section (DSP) 61 is composed of a processing circuit including the time / space gradation number switching section 3 described above, and outputs the output of the mode setting section 58 or the temperature sensor 59 arranged around the DMD chip. As shown in FIG. 1, the time / spatial gradation number switching unit 3 changes the ratio between the number of temporal gradations and the number of spatial gradations, as shown in FIG.

The 8-bit input pixel data is converted to 10 bits by the gamma conversion circuit 1 and then added to the output data of the error diffusion unit 4 in the adder 2 to form 16-bit data, which is converted into a 16-bit data. It is input to the tone switching unit 3. The time / space gradation number switching unit 3 divides the 16-bit data into gradations in the time direction and the space direction, and
Display with.

Here, depending on the ambient temperature of the display device,
A case in which three types of display device driving sequences are switched will be described with reference to the flowchart in FIG.

In a liquid crystal device, as the temperature of the device increases, the response speed of display deteriorates. Therefore, as the temperature rises, by reducing the number of gradations in the time axis direction, it is possible to obtain a sufficient response time by reducing the number of subframes in one frame period.

For example, the display in the time axis direction of 10 ° C. or less is 4 bits, 6 bits from 10 ° C. to 30 ° C., and 7 bits from 30 ° C.
0 ° C. is 8 bits, and 70 ° C. or higher is non-display. When the temperature exceeds 70 ° C., the display device deteriorates. Therefore, the light source is turned off to prevent the temperature from rising.

First, the temperature around the display device is obtained from the temperature sensor 59 by the CPU 60 (S601).

It is determined whether the ambient temperature is in the range of 30 to 70 ° C. (S602). If the ambient temperature T is in the range of 30 to 70 ° C., the number of gradations in the time axis direction is set to 8 bits, The spatial grayscale number switching section 3 outputs the upper 8 bits to the frame memory 8 (S603). Then, the lower 8 bits are output to the error diffusion unit 4 (S604), and diffused as error data to peripheral pixels, thereby storing the gradation of the input data. Read control unit 10 and drive circuit 1
In FIG. 3, as shown in FIG. 3A, data is read from the frame memory 8 in order from the MSB (7 bits), and one frame period is divided into sub-frames according to the bit weights and displayed.

If the ambient temperature is not in the range of 30 to 70 ° C., it is determined whether or not the ambient temperature T is in the range of 10 to 30 ° C. (S605).
Similarly, the number of gradations in the time axis direction is set to 6 bits, and the time / space gradation number switching unit 3 outputs the upper 6 bits to the frame memory 8 (S606). Then, the lower 10 bits are output to the error diffusion unit 4 (S607), and are diffused as error data to peripheral pixels, thereby storing the gradation of the input data. Read control unit 10 and drive circuit 11
In FIG. 3B, as shown in FIG. 3B, data is read from the frame memory 8 in order from the MSB (5 bits), and one frame period is divided into subframes according to the bit weights for display. In this case, the period corresponding to LSB (0 bit) is longer than that in the case of 30 to 70 ° C., so that it is possible to sufficiently display even if the response speed of the liquid crystal device is slow.

If the ambient temperature T is not in the range of 10 ° C. to 30 ° C., it is determined whether the ambient temperature T is 10 ° C. or less (S608), and the same processing as described above is performed. The number of tones is 4 bits, and the number of tones in the spatial axis direction is 12 bits (S609, S610).

When the ambient temperature T is higher than 70 ° C., the display data is fixed and the light source is turned off to prevent the temperature from rising (S611).

As shown in the flowchart, the ratio of the number of gradations in the time axis direction to the number of gradations in the space axis direction is changed in accordance with the peripheral temperature of the display device, whereby the display device according to the peripheral temperature is changed. It is possible to obtain a display period by sub-frame division that is optimal for the response speed. Further, since the deterioration of the number of gradations in the time axis direction can be compensated for by the number of gradations in the spatial direction, it is possible to display the input data without deteriorating the gradation.

According to the present invention, the ratio between the number of temporal gradations and the number of spatial gradations can be changed depending on the temperature around the display device. Thereby, high definition display becomes possible.

Next, an example in which the driving method is switched by setting a mode such as a low power consumption mode or a low noise mode will be described.

When the frequency in the time axis direction for driving the display device is increased, power consumption is increased and radiation noise is increased, which may affect peripheral devices and the human body.

In particular, in a digital drive type device such as a DMD for directly inputting digital data to a display device, a high bandwidth is required for transferring data, and noise and power consumption are problematic. Therefore, there is a demand to switch the driving method according to the mode to be used.

In this embodiment, an example in which a driving method is switched by setting a mode such as a low power consumption mode or a low noise mode will be described with reference to the flowchart of FIG.

First, the drive mode is set by the mode setting section 58 (S701).

The set mode information is acquired by the CPU 60, and if the mode is the normal mode (S702), the number of gradations in the time axis direction is set to 8 bits, and the time / space gradation number switching unit 3
, The upper 8 bits are output to the frame memory 8 (S703). Then, the lower 8 bits are output to the error diffusion unit 4 (S704), and diffused as error data to peripheral pixels, thereby preserving the gradation of the input data. As shown in FIG. 3A, the read control unit 10 and the drive circuit 11 read data from the frame memory 8 in order from the MSB (7 bits) and divide one frame period into sub-frames according to the bit weights for display. I do.

If the set drive mode is the low power consumption mode 1 (S705), similarly, the number of gradations in the time axis direction is set to 6 bits, and the time / space gradation number switching unit 3
The upper 6 bits are output to the frame memory 8 (S70).
6). Then, the lower 10 bits are output to the error diffusion unit 4 (S707), and are diffused as error data to peripheral pixels, thereby storing the gradation of the input data. As shown in FIG. 3B, the read control unit 10 and the drive circuit 11 read data from the frame memory 8 in order from the MSB (5 bits) and divide one frame period into sub-frames according to the bit weights for display. I do.

The driving frequency of the display device corresponding to the sub-frame obtained by dividing one frame is slower than that in the normal mode, so that there is an effect that power consumption and noise are reduced.

Also in the low power consumption mode 2 (S70
8) The same processing is performed to set the number of gradations in the time axis direction to 2 bits and the number of gradations in the space axis direction to 14 bits.

In this case, since the driving frequency of the display device corresponding to the sub-frame obtained by dividing one frame is further slowed down as compared with the normal mode, it is possible to further reduce the influence of power consumption and noise.

As shown in the flowchart, the ratio between the number of gradations in the time axis direction and the number of gradations in the space axis direction is changed according to the setting of the display mode. It is possible to switch, and achieve low power consumption and low noise, and to compensate for the deterioration of the number of gradations in the time axis direction with the number of gradations in the spatial direction. It is possible to display without displaying.

In this embodiment, an example in which three steps are switched has been described. However, the steps may be set finely so that smooth control can be performed.

The mode setting may not only be performed manually, but may be automatically switched according to environmental changes, input image types (moving images / still images / CG), and image change information.

According to the present invention, the ratio between the number of temporal gradations and the number of spatial gradations can be changed according to the mode set by the mode setting section. It is possible to change the driving method according to the application such as switching of the power supply, so that it is possible to reduce power consumption, noise, and the like.

In the above embodiment, the temperature in the vicinity of the display device according to the present invention is measured, and based on the measurement result, the number of gradations in the time axis direction and the number of gradations in the space direction are varied. The present invention describes a method and a display method in which the number of gradations in the time axis direction and the number of gradations in the spatial direction are varied according to a plurality of display modes of the display device. The present invention describes such a display method. CDROM with recorded program,
Information recording media such as semiconductor memories such as DVDs and flash memories are also included. Then, the program recorded on a CD ROM or the like is read into a computer, and the processing according to the display method according to the present invention is executed.

[0067]

As described above, according to the present invention, 1) high-quality display can be achieved by optimal driving regardless of temperature and external conditions. 2) Since the driving method can be changed according to the application such as a low power consumption mode, power consumption and noise can be reduced. This has the effect.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a first embodiment according to the present invention.

FIG. 2 is an explanatory diagram of gamma conversion characteristics.

FIG. 3 is an explanatory diagram of gradation processing in a time axis direction according to an ON time.

FIG. 4 is an error diffusion processing diagram.

FIG. 5 is an overall system block diagram according to a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating a case where three types of display device driving sequences are switched according to the ambient temperature of the display device.

FIG. 7 is a flowchart illustrating a case where a driving method is switched according to a mode setting such as a low power consumption mode or a low noise mode.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 gamma converter 2 first adder 3 time / space gradation number switching unit 4 error diffusion unit 5 vertical delay unit 6 horizontal delay unit 7 second adder 8 frame memory 9 write control unit 10 read control unit 11 Drive circuit 12 LCD 51 Light source 52 First focusing lens 53 Color filter wheel 54 Second focusing lens 55 DMD 56 Zoom lens 57 Projection screen 58 Mode setting section 59 Temperature sensor 60 CPU 61 DSP (digital signal processor)

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) G02F 1/13 505 G02F 1/13 505 5C080 1/133 575 1/133 575 G03B 21/00 G03B 21/00 D G09G 3 / 34 G09G 3/34 D 3/36 3/36 H04N 5/66 H04N 5/66 A 5/74 5/74 DF term (reference) 2H041 AA16 AB14 AC06 AZ01 AZ08 2H088 EA18 HA28 JA17 MA13 2H093 NA55 NC28 NC50 NC57 NC63 NC65 ND06 NE06 NF17 NG02 5C006 AA12 AA13 AA17 AA22 AF44 AF46 AF62 BA12 BB11 BC16 BF02 BF15 EC11 FA19 FA31 FA47 FA56 5C058 AA06 BA01 BA13 BA26 BA33 BA35 BB13 EA11 EA27 EA51 5C080 EA01 DD30 EA01 DD19 EB01 JJ05 JJ07

Claims (13)

[Claims] 1. A video signal processing apparatus for expressing a gray scale by an ON time in a time axis direction in one frame period of a display device, wherein a means for varying the number of gray scales in a time axis direction; Means for varying the number of gradations in the spatial direction to be expressed. 2. The video signal according to claim 1, wherein the video signal is variably controlled so that the sum of the number of gradations in the time axis direction and the number of gradations in the spatial direction becomes equal. Processing equipment. 3. The video signal processing apparatus according to claim 1, wherein the means for spatially expressing the gradation is a pseudo multi-gradation processing means based on an error diffusion method. 4. The video signal processing apparatus according to claim 1, wherein said means for spatially expressing gradation is a pseudo multi-gradation processing means using a dither method. 5. A display device comprising: the video signal processing device according to claim 1; and a display device that performs display based on a signal output by the video signal processing device. 6. A temperature measuring means for measuring a temperature in the vicinity of the display device, and according to an output of the temperature measuring means,
6. The display device according to claim 5, wherein the number of gradations in the time axis direction and the number of gradations in the space direction are variable. 7. A display mode setting means for setting a display mode of the display device, wherein a number of gradations in a time axis direction and a number of gradations in a spatial direction are varied according to an output of the display mode setting means. The display device according to claim 5, wherein: 8. The display device according to claim 5, wherein the display device is a digital micromirror device. 9. The display device according to claim 5, wherein the display device is a ferroelectric liquid crystal device. 10. A display device according to claim 5, wherein the display device is provided with RGB.
A lighting device for illuminating each of the primary color lights, and a projection device for projecting transmitted light or reflected light from the display device onto a screen. 11. A display method comprising: measuring a temperature in the vicinity of a display device; and varying the number of gradations in a time axis direction and the number of gradations in a spatial direction based on the measurement result. 12. A display method, wherein the number of gradations in the time axis direction and the number of gradations in the spatial direction are varied according to a plurality of display modes of the display device. 13. An information recording medium on which a program describing the display method according to claim 11 or 12 is recorded.