JP2002372943A - Driving circuit for image display device, image display device, and driving method of the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high quality image display device in which the difference in display images censed by switching of an image signal correcting means where the correction of the saturation characteristic of a phosphor selected for input signals is considered, can be eliminated and to provide a driving circuit of the image display device and its method. SOLUTION: An image signal converting means 1 conducts operations based on a correction table where the correction of the saturation characteristic of a phosphor for the case that an average image level detected by an average image level detecting means is high, is consider, and an image signal converting mean 2 conducts operations based on a correction table where the correction of the saturation characteristic of the phosphor for the case of a low detected average image level is considered. The image display device is provided with a computing means which conducts weighted computations for the converted image signals that are simultaneously converted from input image signals by the means 1 and 2 and outputted based on the average image levels to obtain converted input image signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device by irradiating a phosphor with an electron beam, a driving circuit of the image display device, and a method thereof. The present invention relates to an apparatus capable of displaying an image satisfactorily even if there is an image.

[0002]

2. Description of the Related Art Conventionally, a multi-electron beam source in which a plurality of surface conduction elements are arranged in a matrix with a plurality of row wirings and column wirings, and a display panel having a phosphor screen which emits light by receiving electron beam irradiation from each electron beam source. As one of the image display devices for displaying an image by (SED panel), there is a configuration disclosed in Japanese Patent Application Laid-Open No. 2000-075833 by the present applicant.

According to this configuration, when performing PWM driving, an SED panel cannot be obtained simply by performing an inverse γ correction for returning a transmitted image signal to the original image by performing γ correction on an original image signal for a CRT. ABL that lowers the type of phosphor, characteristics of input signal, and average image level of the entire screen
The saturation characteristic of the phosphor is affected by control or the like, and the relationship between the luminance signal and the light emission amount is broken.

For this reason, several image signal correcting means are prepared in consideration of the correction of the saturation characteristics of the phosphors, and the image signal correction means in consideration of the correction of the saturation characteristics of the phosphors according to the environment and the average luminance of the entire screen. The input image signal is converted into an image signal that makes the phosphor emission luminance characteristic linear with respect to the electron beam intensity by a method such as switching, thereby enabling an image display having good tone reproduction and color reproduction characteristics.

[0005]

However, in the case of the above-described prior art, the following problems have occurred.

In the conventional image display device configuration, when switching the image signal correction means in consideration of the correction of the saturation characteristics of the phosphor in conjunction with the change in the average image level of the entire screen, a certain threshold value is used. , There was a difference in image quality before and after switching.

[0007] For example, every time so-called ABL control for lowering the average luminance of the entire screen is performed, the viewer is made to recognize a change more than necessary.

Further, in order to reduce the difference due to the switching, many image signal correcting means are required, and the cost cannot be reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to correct an image signal in consideration of a correction of a saturation characteristic of a selected phosphor for an input signal. An object of the present invention is to provide a high-quality image display device, a driving circuit for the image display device, and a method thereof capable of eliminating a difference in a display image due to switching of the means.

[0010]

In order to achieve the above object, according to the present invention, an input image signal is simultaneously converted by a plurality of image signal conversion means to output a converted input image signal. A drive circuit of an image display device that generates a voltage to be applied to an electron-emitting device that emits electrons that cause a phosphor to emit light in response to a signal, the image display device having an average image level detection unit that detects an average image level during a predetermined period. A first image signal conversion unit based on a correction table in consideration of correction of a saturation characteristic of the phosphor when the average image level detected by the average image level detection unit is high, and detection by the average image level detection unit. A second image signal conversion unit based on a correction table that takes into account correction of the saturation characteristics of the phosphor when the average image level obtained is low, The converted image signals output is converted at the same time by the second image signal converting means, characterized in that it comprises a calculating means for weighting operation to obtain a transformed input image signal based on the average picture level.

The calculating means calculates a weight σ value based on the average image level in a range of 0 ≦ σ ≦ 1, and is simultaneously converted by the first and second image signal converting means and output. Σ, (1)
−σ) to perform weighting calculation.

The weight σ value is preferably a value whose denominator is represented by a power of two.

Preferably, the plurality of image signal conversion means are provided for each image quality mode selected by the image quality selection means for selecting the image quality of a display image of the image display device.

The first and second image signal conversion means include:
An input image signal obtained by gamma-correcting the original signal for a cathode ray tube (CRT) is restored to the original signal, and the restored original signal is corrected for electron beam intensity versus non-linearity of phosphor emission luminance in an image display device. It is also preferable to perform conversion and output a converted image signal in which the electron beam intensity versus the phosphor emission luminance characteristic is a straight line.

Preferably, the input image signal is a color signal, and the plurality of image signal conversion means and the calculation means are provided for each color signal, and the input image signal is converted to output a converted image signal. It is.

The input image signal is converted by the rewritable image signal conversion means to output a converted input image signal,
A drive circuit of an image display device for generating a voltage to be applied to an electron-emitting device that emits electrons for causing a phosphor to emit light in accordance with the converted input image signal, wherein the average image detects an average image level during a predetermined period. Level detection means, a first correction table considering correction of the saturation characteristics of the phosphor when the average image level detected by the average image level detection means is high, and an average detected by the average image level detection means. The second correction table taking into account the correction of the saturation characteristics of the phosphor when the image level is low, and the first and second correction tables are weighted based on the average image level. And control means for rewriting the image signal conversion means based on the image signal conversion means.

The control means calculates a weight σ value based on the average image level in a range of 0 ≦ σ ≦ 1, and calculates σ, (1) for the first and second correction tables, respectively.
−σ) to perform weighting calculation.

Preferably, the weight σ value is a value whose denominator is represented by a power of two.

It is also preferable that the control means rewrites the image signal conversion means during a vertical blanking period of the image display device.

Preferably, the first and second correction tables are provided for each image quality mode selected by image quality selection means for selecting the image quality of a display image on an image display device.

The image signal converting means restores an input image signal obtained by gamma-correcting the original signal for a cathode ray tube (CRT) to the original signal, and controls the electron beam intensity of the restored original signal in an image display device. It is also preferable to perform conversion for correcting the non-linearity of the phosphor emission luminance, and output a converted image signal in which the electron beam intensity versus the phosphor emission luminance characteristic is a straight line.

Preferably, the input image signal is a color signal, and the control means rewrites the image signal conversion means by performing a weighting operation for each color signal.

Preferably, the input image signal is a color signal, and the image signal converting means is provided for each color signal, and converts the input image signal to output a converted image signal.

It is also preferable that the average image level detecting means detects the average image level based on the input image signal or the converted input image signal.

It is preferable that the predetermined period during which the average image level detecting means detects the average image level is an integral multiple of one vertical scanning period.

The first and second image signal conversion means include:
It is also preferable that the correction is performed based on a correction table that takes into account the correction of the saturation characteristic of the phosphor in the high gradation part and the correction of the collapse caused by the driving waveform characteristic in the low gradation part.

Preferably, the electron-emitting device is a cold cathode device.

Preferably, the electron-emitting device is a surface conduction electron-emitting device.

In the image display device, an image display section in which a plurality of two-dimensionally arranged electron-emitting devices are connected in a matrix by a plurality of row wirings and a plurality of column wirings,
A phosphor that is disposed to face the image display unit and emits light by receiving electrons emitted from the electron-emitting device; and applying a selection voltage to one of the plurality of row wirings, and selecting the selected row. Selecting means for performing scanning drive by sequentially switching wiring, the driving circuit described above, and modulating means for applying a modulation signal corresponding to a converted input image signal output from the driving circuit to each of the plurality of column wirings Wherein a plurality of electron-emitting devices connected to the selected row wiring are driven by a potential difference between the selection voltage and the modulation signal to display an image.

An input image signal is simultaneously converted by a plurality of image signal conversion steps to output a converted input image signal, and in accordance with the converted input image signal, the converted input image signal is applied to an electron-emitting device which emits electrons for emitting a phosphor. A method of driving an image display device that generates a voltage, comprising: detecting an average image level during a predetermined period; and correcting the saturation characteristic of the phosphor when the detected average image level is high. A first image signal conversion step based on:
A second image signal conversion step based on a correction table considering correction of the saturation characteristic of the phosphor when the detected average image level is low;
And obtaining a converted input image signal by performing a weighting operation based on the average image level on the converted image signals that have been simultaneously converted and output in the image signal converting step.

In the rewritable image signal converting step, the input image signal is converted to output a converted input image signal, and the converted input image signal is applied to an electron-emitting device for emitting electrons for emitting a phosphor in accordance with the converted input image signal. A method for driving an image display device for generating a voltage, the method comprising: detecting an average image level during a predetermined period; and correcting a saturation characteristic of a phosphor when the detected average image level is high. A correction table, a second correction table considering correction of the saturation characteristic of the phosphor when the average image level detected by the average image level detection unit is low, and the first and second correction tables based on the average image level. Weighting the correction table of No. 2 and rewriting the image signal conversion step based on the calculation result.

[0032]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

(Embodiment 1) In Embodiment 1, a multi-electron beam source in which a plurality of surface conduction elements are arranged in a matrix with a plurality of row wirings and column wirings, and emits light upon receiving electron beam irradiation from each electron beam source. An example will be described in which a TV signal is displayed on a display panel (hereinafter, referred to as an SED panel) having a fluorescent screen.

FIG. 6 is a block diagram of a driving circuit of the SED panel.

P2000 is an SED panel. In this embodiment, 240 × 720 surface conduction type devices P2
001 are matrix-wired by 240 vertical rows and 720 horizontal columns, and each surface conduction element P200
The emission electron beam from 1 is accelerated by a high voltage applied from the high voltage power supply unit P30 and is irradiated on a phosphor (not shown) to emit light. The phosphor (not shown) can have various color arrangements depending on the application. For example, an RGB vertical stripe color arrangement is used.

In this embodiment, the horizontal 2
An application example of displaying an NTSC-equivalent television image on an SED panel having 40 (RGB trio) × vertical 240 lines of pixels will be described. However, not only NTSC but also a high-definition image such as HDTV or a computer output image. Image signals having different resolutions and frame rates can be easily handled with almost the same configuration.

FIG. 7 shows an NTSC-Video receiver that receives an NTSC composite video input and outputs RGB components.
4 shows an RGB decoder section P1.

In this unit, a synchronizing signal (SYNC) superimposed on the input video signal is separated and output. Similarly, a color burst signal superimposed on the input video signal is separated, and a CLK signal (CLK1) synchronized with the color burst signal is generated and output.

FIG. 8 shows an NTSC-RGB decoder section P
1 shows a timing generator P2 for generating the following timing signals required to convert the analog RGB signal decoded in 1 into a digital gradation signal for luminance-modulating the SED panel.

The signal output from the timing generator P2 includes a clamp pulse for DC-reproducing an RGB analog signal from the NTSC-RGB decoder P1 in the analog processor P3 and an RGB signal from the NTSC-RGB decoder P1. A blanking pulse (BLK) for adding a blank period to the analog signal in the analog processing unit P3.
Pulse), a detection pulse for detecting the level of the RGB analog signal by the video detection unit P4, and an analog RG
A sample pulse (not shown) for converting the B signal into a digital signal in the A / D section P6;
A RAM controller control signal necessary for controlling the RAMP8, a free-running CLK signal (CLK2) generated by a PLL circuit in the timing generator P2 so as to synchronize with CLK1 when CLK1 is input, and a RAM controller control signal required in the timing generator P2. And a synchronization signal (SY generated based on CLK2)
NC2).

This timing generator P2 is a self-running CL
By providing the K2 generation means, the reference signals CLK2 and SYNC2 can be generated even when there is no input video signal, so that an image can be displayed by reading the image signal from the RAM P8.

FIG. 9 shows an NTSC-RGB decoder section P
1 shows an analog processing unit P3 provided for each of the output primary color signals from No. 1;

The analog processing section P3 receives a clamp pulse from the timing generation section P2 and performs DC reproduction.

Further, a blanking period is added in response to a BLK pulse from the timing generator P2.

Also, it receives the gain adjustment signal of the D / A section P14, which is one of the control outputs of the system control section mainly composed of the MPU P11, and receives the amplitude of the primary color signal inputted from the NTSC-RGB decoder section P1. Perform control.

Also, when receiving an offset adjustment signal of the D / A section P14, which is one of the control outputs of the system control section mainly composed of the MPU P11, the NTSC-RGB
The black level of the primary color signal input from the decoder unit P1 is controlled.

The video detecting section P4 is a video detecting section for detecting an input video signal level or a video signal level after being controlled by the analog processing section P3, and outputs a detection pulse from the timing generating section P2. Receiving, MP
The detection result is read by the A / D unit P15, which is one of the control inputs of the system control unit mainly composed of the UP11. Here, the video detector P4, A / D
The unit P15 constitutes an average image level detecting means.

The detection pulse from the timing generator P2 is composed of, for example, a gate pulse, a reset pulse, and a sample and hold (S / H) pulse. The video detector is composed of, for example, an integrating circuit and an S / H circuit. .

For example, during the valid period of the input video signal by the gate pulse, the video signal is integrated by the above-mentioned integration circuit, and the output of the integration circuit is sampled by the S / H circuit by the S / H pulse generated in the vertical flyback period. A during the vertical flyback period
After the detection result is read by the / D section P15, the integration circuit and the S / H circuit are initialized by the reset pulse.

With such an operation, the average video level for each field can be detected.

The LPFP 5 is a pre-filter means placed before the A / D section P6.

The A / D section P6 is an A / D converter which receives the sample CLK from the timing generation section P2 and quantizes the analog primary color signal passed through the LPFP 5 with a required number of gradations.

The image signal conversion means P7 is a conversion means provided for converting the input video signal into the light emission characteristics of the SED panel.

When a luminance gradation is expressed by pulse width modulation as in this embodiment, a linear characteristic in which the amount of light emission is almost proportional to the magnitude of luminance data is often exhibited.

On the other hand, the video signal is a TV signal using a CRT.
Since it is intended for a receiver, it is subjected to gamma processing in order to correct the non-linear emission characteristics of a CRT.

Therefore, when a TV image is displayed on a panel having linear light emission characteristics as in this embodiment, it is necessary to cancel the effect of the gamma processing by an image signal correcting means such as the image signal converting means P7.

The operation described later is performed by the output of the I / O control unit P13, which is one of the control inputs and outputs of the system control unit mainly composed of the MPU P11. RAM
P8 is an image memory provided for each R / G / B processing circuit, and has addresses corresponding to the total number of display pixels of the panel (in this case, horizontal 240 × vertical 240 lines × 3).

The luminance data to be emitted by each pixel of the panel is stored in this memory, and the luminance data is read out in a dot-sequential manner to display the image stored in the memory on the panel.

The output of the luminance data from the RAM P8 is
This is performed under the address control from the RAM controller P12.

Writing data to the RAM P8 is performed by M
This is performed under the management of the system control unit mainly composed of the PU P11. In the case of a simple test pattern or the like, the MPU P11 calculates and generates and writes luminance data stored in each address of the RAM P8. In the case of a pattern such as a natural still image, for example, an image file stored in an external computer or the like is read via the serial communication I / F P16, which is one of the input / output units of the system control unit mainly composed of the MPU P11. Is written to RAM P8 which is an image memory.

A data selector P9 determines whether the output image signal is data from the RAM P8 or data from the A / D unit P6 (input video signal system).
It is determined by the output of the I / O control unit P13, which is one of the control inputs and outputs of the system control unit mainly composed of the UP 11.

In addition to the two-system input select, the selector P9 has a mode for generating a fixed value, and has an I / O control unit P
13, this mode can be selected and output. In this mode, an adjustment signal such as an all-white pattern can be displayed at a high speed without an external input.

P10 is a horizontal one-line memory means provided for each primary color signal.
, The luminance data input in parallel to the three RGB systems are rearranged in an order according to the panel color arrangement, converted into one system serial signal, and output to the X driver unit via the latch means P22.

The system control section is mainly composed of MPU P
11. Serial communication I / F P16, I / O control unit P1
3, D / A section P14, A / D section P15, data memory P
17, composed of a user SW means P18.

The system control section includes a user switch
The request is realized by receiving a user request from the means P18 or the serial communication I / FP 16 and outputting a corresponding control signal from the I / O control unit P13 or the D / A unit P14.

Further, upon receiving the system monitoring signal from the A / D unit P15, the corresponding control signal is transmitted to the I / O control unit P13 or D / D.
Optimal automatic control is performed by output from the / A section P14. In the present embodiment, as a user request, display control such as generation of a test pattern, variable gradation, brightness, and color control can be realized.

As described above, automatic control of ABL or the like can also be performed by monitoring the average video level from the video detection unit P4 by the A / D unit P15.

Further, by providing the data memory P17, the user adjustment amount can be stored.

P19 is a Y driver control timing generator, P20 is an X driver control timing generator,
Both receive the CLK1, CLK2 and SYNC2 signals and generate Y driver control and X driver control signals.

P21 is a control unit for controlling the timing of the line memory P10.
An R, G, B WRT control signal for receiving the SYNC2 signal and writing the luminance data to the line memory and an R, G, B RD control signal for reading the luminance data from the line memory in an order according to the panel color arrangement are generated. .

FIG. 10 is a timing chart for explaining the operation of the SED panel drive circuit.

T104 is a waveform of a color sample data string written using one of the RGB colors as an example, and is composed of 240 data strings in one horizontal period. This data string is written into the line memory P10 by the control signal in one horizontal period.

In the next horizontal period, the line memory P1 for each color
0 is enabled at three times the frequency of writing to enable 720 luminance data strings T10 per horizontal period.
Get 5.

Reference numeral P1001 denotes an X / Y driver timing generator, which receives control signals from the Y driver control timing generator P19 and the X driver control timing generator P20. The X and Y driver timing generator P
The signal output from the shift register 1001 is a shift clock and the data read into the shift registers P1101 and 1107 are P
An LD pulse for fetching to a memory unit (not shown) in the WM generator unit P1102 and the D / A unit P1103 and for triggering a horizontal cycle to the PWM generator unit P1102 and the D / A unit P1103; And a horizontal period shift clock for moving the Y shift register for controlling the Y driver and a vertical period trigger signal for giving a row scanning start trigger.

The shift register P1101 stores the 720 luminance data strings from the latch means P22 in each horizontal cycle into the X and Y driver timing generator P1001.
The data is read by the shift clock T107 synchronized with the luminance data from the CPU, and the data of one horizontal row of 720 pieces are transferred at a time to the PWM generator P1102 by the LD pulse T108.

The shift register P1107 reads the column wiring drive current data string of 720 column wirings every horizontal cycle from the data selector means P1201 by the shift clock in the same manner as the luminance data, and the D / A section P1103 by the LD pulse T108. , The data for 720 horizontal rows is transferred at a time.

If table ROM P1202 is SE
A memory means for storing data of a current amplitude value to be passed through each of the 720 × 240 surface conduction type elements of the D panel P2000, and an X, Y driver timing generation section P1
The read address control is performed by the If table ROM control signal from 001, and 720 current amplitude value data for one row scanned as shown in T106 every horizontal cycle is output. By setting the current value for driving the column wiring (that is, the surface conduction type element) to an optimum value for each element using the If table ROM P1202, the uniformity of luminance can be extremely improved.

Further, the If table ROM P1202
It is possible to use 720 × 240 current amplitude value data as one bank and provide a plurality of types of banks.

For example, when the light emission luminance of the panel is switched in a plurality of stages, the current amplitude data to be passed to each element is stored in the bank corresponding to each stage, and the MPU P11
A configuration may be adopted in which an If data bank corresponding to a desired brightness is selected by a bank switching signal output from an I / O control unit P13 which is one of the control inputs and outputs of a system control unit mainly configured by. it can.

A data selector means P1201 is provided for the case where the If table ROM P1202 is not used for the purpose of cost reduction or the like.
If setting data output from the I / O control unit P13, which is one of the control inputs and outputs of the system control unit mainly composed of the control unit 11, is output to the shift register P1107 by a switching signal from the I / O control unit P13. be able to. This makes it possible to control the display luminance of the panel by changing the output If data.

A PWM generator section P1102 provided for each column wiring receives the luminance data from the shift register P1101, and generates a pulse signal T110 having a pulse width proportional to the data size for each horizontal cycle.

D / A section P110 provided for each column wiring
Reference numeral 3 denotes a current-output digital-to-analog converter which receives data of a current amplitude value from the shift register P1107 and generates a driving current T109 having a current amplitude proportional to the data size for each horizontal cycle.

P1104 is a switch means composed of a transistor or the like, and applies a current output from the D / A unit P1103 to the column wiring during a period in which the output from the PWM generator unit P1102 is valid, and a PWM generator unit P11
The column wiring is grounded during the period in which the output from 02 is invalid.

An example of a column wiring driving waveform is shown at T111.

Diode means P1 provided for each column wiring
105 is a Vmax regulator P1106 on the common side.
Connected to. The Vmax regulator P1106 is a constant voltage source capable of sinking current, and is a diode means P11
05 × 720 × 2 of SED panel P2000
A protection circuit for preventing an overvoltage from being applied to each of the forty surface conduction elements is formed.

The protection voltage (the potential defined by Vmax and −Vss applied when scanning the row wiring is selected) is MP
This is provided by a D / A unit P14, which is one of the control inputs and outputs of the system control unit mainly composed of UP11.

Therefore, it is also possible to change the Vmax potential (or -Vss potential) for the purpose of luminance control in addition to the element overvoltage prevention.

That is, if If data for increasing the output current of the D / A section P14 is given and the protection diode means P1105 is always set to conduct, the selection potential of the surface conduction element P2001 becomes (Vmax + Vs
s), the luminance control can be realized by changing the Vmax potential (or -Vss potential).

The Y shift register section P1002 stores X, Y
A pre-driver unit P10 which receives a horizontal cycle shift clock from the driver timing generation unit P1001 and a vertical cycle trigger signal for giving a row scanning start trigger, and is provided with a selection signal for scanning a row wiring for each row wiring.
03 sequentially.

The output section for driving each row wiring is composed of, for example, transistor means P1006, FET means P1004, and diode means P1007.

The pre-driver section P1003 drives this output section with good response.

The FET means P1004 is a switch means which conducts when a row is selected, and the constant voltage regulator P10 when selected.
The -Vss potential from 05 is applied to the row wiring.

The transistor means P1006 is a switch means which conducts when a row is not selected, and applies the Vso potential from the constant voltage regulator P1005 to the row wiring when the row is not selected.

An example of a row wiring drive waveform is shown at T112.

The diode means P1007 is provided for preventing an abnormal potential from being generated in the row wiring and protecting the output section for driving each row wiring. The constant voltage regulator units P1005 and 1008 for generating −Vss and Vuso potentials are MPU P1
1 is controlled by a D / A unit P14, which is one of the control inputs / outputs of the system control unit composed mainly of the control unit 1.

Similarly, the high-voltage power supply unit P30
It is controlled by a D / A unit P14, which is one of the control inputs and outputs of the system control unit mainly composed of P11.

Further, an example in which an HDTV signal and a computer signal can be received in addition to the NTSC signal will be described.

The input signal switching section as shown in FIG. 13 is provided at the preceding stage of FIG.

P40, P41 and P42 are NTSC signals,
An interface unit corresponding to an HDTV signal and a computer signal. The interface unit converts the resolution of an input signal so as to match the number of pixels of the SED panel P2000, and outputs the converted signal in the form of an RGB component signal and a SYNC signal.

P44 is a signal switching section such as a remote controller accessed by the user, and sends a selection signal for selecting which input signal to display to the signal discriminating section P45.

A signal discriminating section P45 receives a selection signal from the signal switching section P44 and supplies a switching signal to the signal selector section P43.

The signal discriminating section P45 is composed of P40 to P42.
When only one type of signal is inputted, for example, a switching signal is provided to the signal selector P43 so that the signal is automatically displayed.

P43 is a signal selector, which selects and outputs one of three types of input signals according to the switching signal from the signal discriminator P45.

Further, the signal discriminating section P45 sends information on which signal is currently selected to the MPU P1 in FIG.
1 is given to the system control section mainly configured. The system control unit can determine the type of the image signal to be received at present based on this information.

For example, when displaying a TV signal such as an NTSC signal or an HDTV signal, it is desirable to have a high luminance for viewing away from the display screen, and when displaying a PC signal, it is desirable to reduce the luminance for viewing near the display screen. I do.

At this time, the system control unit performs brightness control using the brightness control method (controls If data, Vmax, -Vss, etc.) described above according to the type of input to be received. .

Further, in the display device having the configuration shown in FIG.
An example will be described in which the average luminance level of an input image signal is detected to suppress power consumption of the entire apparatus, and so-called ABL control for suppressing the light emission luminance of the entire panel when the average luminance level is high.

By the operation described above, the average image level of each color is detected in analog amount by the video detection unit P4 provided for each of RGB, and the A / D converter of the system control unit of the A / D unit P15 detects the average image level. Read as a digital value into the system control unit.

MPU P11 in the system control section
Is to monitor the average image level in each field period, and when the average image level exceeds a certain threshold, for example, the brightness control method (If data or Vma
x, -Vss, etc.).

The greater the average image level, the more the luminance suppression control is performed so that the average light emission luminance over the entire panel does not exceed a certain threshold.

Here, the image signal conversion means P7 shown in FIG.
Will be described with reference to FIG.

In FIG. 1, reference numeral 1 denotes a correction table which takes into account correction of a small saturation characteristic of a phosphor corresponding to a case where the average image level of the entire screen is high and the suppression of luminance is strong (when the amount of electron beam is small). The first (first) image signal conversion means 2 takes into account the correction of the large saturation characteristic of the phosphor corresponding to the case where the average image level of the entire screen is low and the suppression of luminance does not work (when the amount of electron beam is large). (Second) image signal conversion means based on the corrected table. Reference numeral 3 denotes subtraction means, 4 and 5 denote multiplication means, and 6 denotes addition means, which constitute an operation means, and output an input image signal as a converted input image signal.

Each of the image signal conversion means 1 and 2 is, for example, a ROM
Calculation of a table realized and stored in a non-volatile memory such as that described above is performed as follows.

The linear original signal is α1 (the number of gradations is kbit
Α1 is an integer from 0 to (2 k −1)),
The conversion characteristic of the gamma correction performed on the TV signal transmission side is f1
(X), and the inverse function of f1 (x) is g1 (x).

At this time, with respect to the input image signal β1 that has been gamma-corrected on the TV signal transmitting side, the restored original signal α1 obtained by canceling the gamma correction is α1 = g1 (β1) (conversion equation 1) ).

On the other hand, if the pulse width data is α2, the nonlinear characteristic curve of the luminance-pulse width data of the SED panel is f2 (x), and the inverse function of f2 (x) is g2 (x), the SED panel has The converted input image signal α2, which is pulse width data for canceling the non-linear characteristic curve of luminance-pulse width data, is represented by α2 = g2 (β2) (2) where luminance is β2.

Here, the restored original signal α obtained by the conversion equation 1
By substituting 1 into β2 of the conversion equation 2 as a linear luminance, a converted input image signal α2 can be obtained.
A conversion input image signal α2 is obtained for 1 and a table that approximates to an integer value and outputs it may be created based on the conversion formula (the address signal of the table ROM (image signal conversion means P7) corresponds to β1, Α2 is stored as data corresponding to the address).

More specifically, the following may be performed.

FIG. 11 shows an example of a gamma correction conversion curve performed on the TV signal transmission side to correct the gamma characteristic of the CRT.

According to the literature (edited by Japan Broadcasting Corporation, Hi-Vision Technology, p. 47), an approximate curve of γ = 0.45 is often used. Accordingly, an approximate curve of γ = 2.2 may be used as a function for inverse γ correction (corresponding to the above g (x1)).

FIG. 12 shows the SE used in this embodiment.
4 shows normalized luminance-gradation data (substantially proportional to the drive voltage pulse width) of the D panel.

By calculating the inverse function of the approximation function of the convex curve, the nonlinearity of the SED panel can be corrected as in the case of the inverse gamma correction.

As can be seen from FIG. 12, the nonlinearity of the SED panel differs depending on the RGB phosphor. By calculating the inverse function of the approximation function of the convex curve for each color, it is possible to correct the nonlinear difference for each color.

In this example, the emission characteristic of R is γ =
The emission characteristic of 0.72, G can be approximated by γ = 0.9, and the emission characteristic of B can be approximated by γ = 1. Since this value may change depending on the driving condition of the panel, the above is merely an example, and it is necessary to calculate the value according to the driving condition of the panel.

The method of creating table data by power function approximation has been described above. However, the present invention is not limited to this, and similar effects can be obtained by another function approximation or by obtaining from actual measurement curves of panel characteristics. For example, the same effect can be obtained by obtaining from a characteristic curve that considers the collapse of a low gradation portion due to the rising characteristic of the drive waveform as shown in FIG.

The above-described conversion is simultaneously performed on the input image signals by the image signal conversion means 1 and 2, while the output from the video detector P4, which is the average image level of the entire screen, is received. A weight σ value to be assigned to the image signal conversion means 2 is calculated inside the MPU P 11 according to the output value from the / D unit P 15, and is used as a multiplier of the multiplier 5.

The σ value is calculated, for example, as a value from 0 to 1 from the ABL command value.
Subtractor 3 inside P11 or outside MPU P11
Is prepared and the value is calculated by receiving the σ value. If the σ value is approximated by a value whose denominator is 2 n, for example, the hardware configuration of the multiplier becomes easy.

1-σ is a multiplier of the multiplier 4 as a weight assigned to the image signal conversion means 1. The multipliers of the multipliers 4 and 5 are updated during the vertical flyback period after the luminance detection for one vertical period is completed.

The input image signals converted by the image signal conversion means 1 and 2 are weighted by the multipliers 4 and 5, respectively, and added by the adder 6 to obtain a converted input image signal.

In one vertical period in which the average image level of the entire screen is detected by the video detection unit P4 and the A / D unit P15, correction is made by the σ value calculated based on the input image signal one vertical period before. It is carried out.

Alternatively, a memory for one vertical period is prepared before or after the image signal conversion means 1 and 2, and the multiplier 4
The same effect can be obtained by a configuration in which the timing of inputting the converted image signal to the block No. 5 is delayed by one vertical period to perform correction in accordance with the σ value.

Alternatively, the image signal input to the video detector P4 is used as a converted input image signal output from the adder 6, and the input image signal after one vertical period is calculated based on the σ value calculated based on this signal. The same effect can be obtained even when the correction is performed.

The same effect can be obtained even if the detection period of the average image level of the entire screen is an integral multiple of one vertical period.

As described above, according to the present embodiment,
The correction table taking into account the saturation phenomenon of the phosphor is strictly expressed, and the switching of the correction table taking into account the saturation phenomenon of the phosphor is continuously performed in conjunction with the change in the average luminance of the entire screen, so that a good Image display having a tone reproduction characteristic can be performed.

(Embodiment 2) As Embodiment 2, the configuration around the MPU P11 as the control means is configured as shown in FIG. 2, and a correction method in the procedure shown in FIG. 4 will be described.
The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 2, reference numeral 21 denotes a (first) correction table which takes into account correction of a small saturation characteristic of a phosphor corresponding to a case where the average image level of the entire screen is high and luminance is strongly suppressed. Is a (second) correction table which takes into account correction of a large saturation characteristic of the phosphor corresponding to a case where the average image level is low and the suppression of luminance does not work, and 23 is an image signal prepared in the image signal conversion means P7. A conversion unit that outputs an input image signal as a converted input image signal;

The correction tables 21 and 22 are arranged exclusively for a certain address in the data memory P17, for example, and store the same tables as the image signal conversion means 1 and 2 in the first embodiment. Is RA
The memory is a rewritable memory such as M, and a control line for rewriting is connected from the MPU P11.

In FIG. 4, step 1 is, for example, ABL
Step 2 is a process for determining whether the average image level should be restricted, such as a command. Step 2 is a process for executing the restriction. Step 3 is a process for calculating a correction table corresponding to the restriction. Step 5 is a process of determining whether or not the period has come, and step 5 is a process of updating the table calculated in step 3 to the image signal conversion unit 23.

In Step 3, as in the first embodiment, the MPU is based on the output value from the A / D unit P15 that has received the output of the video detection unit P4, which is the average image level of the entire screen.
In P11, σ and 1−σ are calculated, and M is calculated based on the σ value.
Each correction table is weighted in the PU P11.

The sum of the two weighted correction tables is transferred to the image signal conversion means P7 as a correction table taking into account the correction of the phosphor saturation characteristics corresponding to the average image level of the entire screen. The image signal is output as a converted input image signal by the image signal converting means P7.

That is, for example, if the input image signal is x,
Assuming that the function representing the correction table 1 of 21 is F (x) and the function representing the correction table 2 of 22 is G (x), a function Y representing the correction table to be transferred to the image signal conversion means P7
(X) is represented by Y (x) = σF (x) + (1−σ) G (x).

The updating of the image signal conversion means P7 is performed during the vertical flyback period after the luminance detection for one vertical period is completed.

As in the first embodiment, the video detector P
4. In one vertical period in which the average image level of the entire screen is detected by the A / D unit P15, correction is performed by the σ value calculated based on the input image signal one vertical period before.

Alternatively, a memory for one vertical period is prepared before the image signal converting means P7, and the image signal converting means P7
A similar effect can be obtained by a configuration in which the timing of inputting an image signal to the image is delayed by one vertical period to perform correction in accordance with the σ value.

Alternatively, the image signal input to the video detector P4 is used as a converted input image signal output from the image signal converting means P7, and the input image after one vertical period is calculated based on the σ value calculated based on this signal. A similar effect can be obtained even when the signal is corrected.

The above multiplication, addition, and subtraction are performed by the MPU.
Do not perform within P11, multiplier outside MPU P11,
A similar effect can be obtained by using a configuration in which an adder and a subtractor are provided.

(Embodiment 3) As Embodiment 3, a description will be given of a correction method based on the configuration shown in FIG. 3 in which the image quality mode is switched by the image quality selection means according to the type of input image.
The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

For example, the display mode is switched between a display mode A for a TV signal such as an NTSC signal and an HDTV signal, for which high luminance is desirable for viewing away from the display screen, and a display mode B for a PC signal whose luminance is desired to be reduced for viewing near the display screen. And use it.

In this case, it is necessary to prepare two types of image signal conversion means for each mode, since the manner of the brightness control differs depending on the mode.

That is, the image signal conversion means 1A and 1B taking into account the correction of the small saturation characteristic of the phosphor corresponding to the case where the average image level of the entire screen is high and the suppression of the luminance is strongly applied.
In addition, image signal conversion means 2A and 2B are prepared in consideration of correction of a large saturation characteristic of the phosphor corresponding to a case where the average image level of the entire screen is low and luminance suppression does not work.

According to the selected mode, any one of the image signal conversion means corrects a small saturation characteristic of the phosphor corresponding to a case where the average image level of the entire screen in the environment is high and the suppression of the luminance is strongly applied. The mode switching signal is selected as the image signal converting means 1 taking into account the image signal converting means 2 taking into account the correction of the large saturation characteristic of the phosphor corresponding to the case where the average image level of the entire screen is low and the suppression of luminance does not work. .

Based on these image signal conversion means 1 and 2, the input image signal is output as a converted input image signal by the method shown in the first embodiment.

Regarding the mode switching factor of the image quality, the same effect can be obtained regardless of the type of the input image as well as the use of the input image. For example, mode switching depending on whether the input image is viewed in a bright environment or a dark environment, or It is also possible to respond to mode switching or the like depending on the color to be emphasized.

(Embodiment 4) Embodiment 4 includes:
The third embodiment is applied to the second embodiment, and two types of correction tables are prepared for each mode, and two types of correction tables corresponding to each mode are selected by a mode switching signal.

In this case, a procedure as shown in FIG. 5 is inserted between step 2 and step 3 in FIG. 4 and output as a converted input image signal by the method described in the second embodiment.

[0156]

As described above, according to the present invention,
The correction table taking into account the saturation phenomenon of the phosphor is strictly expressed, and the switching of the correction table taking into account the saturation phenomenon of the phosphor is continuously performed in conjunction with the change in the average luminance of the entire screen, so that a good Image display having a tone reproduction characteristic can be performed.

Further, even when the image quality is switched according to the use or type of the input image, the switching of the correction table taking into account the saturation phenomenon of the phosphor is continuously performed in conjunction with the change in the average luminance of the entire screen. This makes it possible to display an image having good tone reproduction and color reproduction characteristics.

[Brief description of the drawings]

FIG. 1 shows a block diagram of an image conversion unit described in Embodiment 1.

FIG. 2 illustrates an image conversion unit and an image conversion unit according to a second embodiment.
FIG. 3 shows a block diagram of a PU.

FIG. 3 shows a block diagram of an image conversion unit described in a third embodiment.

FIG. 4 shows a rewriting sequence of the image conversion means described in the second embodiment.

FIG. 5 shows a rewriting sequence of the image conversion means described in the fourth embodiment.

FIG. 6 shows a block diagram of a drive circuit of the SED panel.

FIG. 7 shows a block diagram of an NTSC-RGB decoder unit.

FIG. 8 shows a block diagram of a timing generator.

FIG. 9 shows a block diagram of a signal processing unit of the SED panel.

FIG. 10 is a timing chart of each drive signal of the SED panel.

FIG. 11 shows an example of gamma correction.

FIG. 12 shows an example of light emission characteristics of an SED panel.

FIG. 13 shows a block diagram of an input switching unit of the SED panel.

FIG. 14 shows an example of a light emission characteristic of an SED panel in consideration of a collapse of a low gradation portion caused by a rising characteristic of a driving waveform.

[Explanation of symbols]

(1) Image signal conversion means based on a correction table which takes into account correction of a small saturation characteristic of a phosphor corresponding to a case where the average image level of the entire screen is high and the suppression of luminance is strongly performed. (2) The average image level of the entire screen is low and the luminance is low. Image signal conversion means 3 based on a correction table in consideration of correction of a large saturation characteristic of a phosphor corresponding to when suppression does not work 3 Subtraction means 4, 5 Multiplication means 6 Addition means 21 Correction table 1 22 Correction table 2 23 Image signal conversion Means P7 Image signal conversion means P11 MPU

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C058 AA03 BA08 BA13 BB04 BB12 BB25 5C080 AA08 BB05 CC03 DD01 EE28 GG09 JJ02 JJ04 JJ05 JJ07

Claims (22)

[Claims] 1. An electron emission device for simultaneously converting an input image signal by a plurality of image signal conversion means, outputting a converted input image signal, and emitting electrons for causing a phosphor to emit light in accordance with the converted input image signal. A drive circuit of an image display device for generating a voltage to be applied, comprising: an average image level detection unit that detects an average image level during a predetermined period; and a case where the average image level detected by the average image level detection unit is high. A first image signal converter based on a correction table that takes into account the correction of the saturation characteristics of the phosphor; and a correction of the saturation characteristics of the phosphor when the average image level detected by the average image level detector is low. A second image signal converter based on the corrected table, and an input image signal which are simultaneously converted by the first and second image signal converters and output respectively. A driving means for obtaining a converted input image signal by performing a weighting operation on the output converted image signal based on the average image level. 2. The calculation means calculates a weight σ value based on the average image level in a range of 0 ≦ σ ≦ 1, and is simultaneously converted by the first and second image signal conversion means, respectively. The output converted image signals have σ and (1
2. The driving circuit for an image display device according to claim 1, wherein a weighting operation is performed by multiplying by-[sigma]). 3. The driving circuit according to claim 2, wherein the weight σ value is a value whose denominator is represented by a power of two. 4. The image signal conversion means according to claim 1, wherein said plurality of image signal conversion means are provided for each image quality mode selected by an image quality selection means for selecting image quality of a display image of an image display device. , 2 or 3, the driving circuit of the image display device. 5. The image signal conversion device according to claim 1, wherein:
An input image signal obtained by gamma-correcting the original signal for a cathode ray tube (CRT) is restored to the original signal, and the restored original signal is corrected for electron beam intensity versus non-linearity of phosphor emission luminance in an image display device. The driving circuit according to any one of claims 1 to 4, wherein the conversion circuit performs conversion and outputs a converted image signal in which the electron beam intensity versus the phosphor emission luminance characteristic is a straight line. 6. The input image signal is a color signal, and the plurality of image signal conversion means and the calculation means are provided for each color signal, and convert the input image signal to output a converted image signal. The driving circuit for an image display device according to claim 1, wherein: 7. An input image signal is converted by a rewritable image signal conversion means to output a converted input image signal.
A drive circuit of an image display device for generating a voltage to be applied to an electron-emitting device that emits electrons that cause a phosphor to emit light in accordance with the converted input image signal, the average circuit detecting an average image level during a predetermined period Level detection means, a first correction table considering correction of the saturation characteristic of the phosphor when the average image level detected by the average image level detection means is high, and an average detected by the average image level detection means A second correction table that takes into account the correction of the saturation characteristic of the phosphor when the image level is low; and a weighting operation for the first and second correction tables based on the average image level. Control means for rewriting the image signal conversion means on the basis of the image signal conversion means. 8. The control means calculates a weight σ value based on the average image level in a range of 0 ≦ σ ≦ 1, and calculates σ, ( 1
The driving circuit of the image display device according to claim 7, wherein the weighting operation is performed by multiplying by −σ). 9. The driving circuit according to claim 8, wherein the weight σ value is a value whose denominator is represented by a power of two. 10. The driving circuit for an image display device according to claim 7, wherein said control means performs rewriting of said image signal conversion means during a vertical flyback period of the image display device. 11. The apparatus according to claim 11, wherein said first and second correction tables are provided for each image quality mode selected by an image quality selection means for selecting the image quality of a display image on an image display device. Item 11. The driving circuit for an image display device according to any one of items 7 to 10. 12. The image signal converting means restores an input image signal obtained by gamma-correcting an original signal for a cathode ray tube (CRT) to the original signal, and an electron beam in the image display device of the restored original signal. 12. A conversion method for correcting nonlinearity of intensity versus phosphor emission luminance, and outputting a converted image signal in which the electron beam intensity vs. phosphor emission luminance characteristic is a straight line. 2. The driving circuit for an image display device according to claim 1. 13. The input image signal is a color signal,
13. The driving circuit according to claim 7, wherein the control unit rewrites the image signal converting unit by performing a weighting operation for each color signal. 14. The input image signal is a color signal,
14. The image display device according to claim 7, wherein the image signal conversion unit is provided for each color signal, and converts the input image signal to output a converted image signal. Drive circuit. 15. The apparatus according to claim 1, wherein said average image level detecting means detects said average image level based on said input image signal or said converted input image signal. Drive circuit of the image display device. 16. The apparatus according to claim 1, wherein the predetermined period in which the average image level detecting means detects an average image level is an integral multiple of one vertical scanning period. Drive circuit of the image display device. 17. The first and second image signal converters take into account correction of a saturation characteristic of the phosphor in a high gradation area and a collapse of a driving waveform in a low gradation area. 17. The driving circuit according to claim 1, wherein the correction is performed based on a correction table. 18. The driving circuit according to claim 1, wherein said electron-emitting device is a cold-cathode device. 19. The driving circuit according to claim 1, wherein the electron-emitting device is a surface conduction electron-emitting device. 20. An image display section in which a plurality of two-dimensionally arranged electron-emitting devices are connected in a matrix by a plurality of row wirings and a plurality of column wirings, and arranged opposite to the image display section. And a phosphor that emits light by receiving electrons emitted from the electron-emitting device, and a scanning drive by applying a selection voltage to one of the plurality of row wirings and sequentially switching the selected row wiring. 20. A drive circuit according to claim 1, further comprising: a selector configured to apply a modulation signal corresponding to a converted input image signal output from the drive circuit to each of the plurality of column wirings. An image display device comprising: driving a plurality of electron-emitting devices connected to the selected row wiring by a potential difference between the selection voltage and the modulation signal, and displaying an image. 21. An electron emission device for simultaneously converting an input image signal by a plurality of image signal conversion steps, outputting a converted input image signal, and emitting electrons for causing a phosphor to emit light in accordance with the converted input image signal. A method for driving an image display device that generates an applied voltage, comprising: detecting an average image level during a predetermined period; and correcting the saturation characteristics of the phosphor when the detected average image level is high. A first image signal conversion step based on a table, a second image signal conversion step based on a correction table considering correction of a saturation characteristic of a phosphor when the detected average image level is low, and an input image signal. Weights the converted image signals that have been simultaneously converted by the first and second image signal conversion steps and output respectively, based on the average image level. Obtaining a converted input image signal by performing an operation. A method for driving an image display device, comprising: 22. An electron emission device for converting an input image signal in a rewritable image signal conversion step to output a converted input image signal, and emitting electrons for causing a phosphor to emit light according to the converted input image signal. A method for driving an image display device that generates a voltage to be applied, comprising: detecting an average image level during a predetermined period; and correcting a saturation characteristic of the phosphor when the detected average image level is high. 1 correction table, a second correction table considering correction of the saturation characteristic of the phosphor when the average image level detected by the average image level detection means is low, and the first correction table based on the average image level. And weighting the second correction table, and rewriting the image signal conversion step based on the calculation result. The driving method of the image display apparatus.