JPH0318823A - Video signal correcting device - Google Patents

Abstract

PURPOSE:To execute an effective linearity correction by calculating a reverse conversion curve of a characteristic curve and storing it in advance in plural look-up table memories, providing a table selection memory and executing arbitrarily a selection of a table number against a variation of a video signal level - screen luminance characteristic. CONSTITUTION:Temperature data obtained by bringing a result of measurement of a temperature of a liquid crystal panel 17 by a temperature detector 12b to digital conversion refers to a table selection memory 12d in which data for relating input data and the table number is stored. Subsequently, when the table number of its output is inputted to the upper address line of a look-up memory 12e, a table against a variation of a temperature level is selected. Also, video signal data for driving a dot matrix type display inputted to the lower address line is converted by correction data generated by calculating a reverse conversion curve of a characteristic curve of a video signal level - screen luminance characteristic of every temperature level of the panel. In such a way, an effective linearity correction can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal correction device for correcting a video signal of a dot matrix display to improve display characteristics.

2. Description of the Related Art Conventional video signal correction devices have been studied for display devices using liquid crystal displays, etc., and attention has been focused mainly on linearity M-positive for improving liquid crystal display characteristics.

An example of the above-mentioned conventional video signal correction device will be described below with reference to the drawings.

FIG. 7 shows the configuration of a liquid crystal display device using a conventional video signal correction device.

In FIG. 7, 72 is a video signal correction device, ? 2a is A
/D converter? 2b is lookup table memory, 7
3c is a D/A converter. An A/D converter output from a video signal processing circuit 71 that creates three primary color video signals (for example, R, G, and B) from a video signal. The video signal data 73a that has undergone digital conversion in step 2a is corrected by referring to the lookup table memory 72b. The video signal data 73b that has undergone this correction is D/A
Analog conversion is performed by converter 72c. Furthermore, in the voltage adder 74, a threshold voltage indicating the rising position of the video signal level-screen brightness characteristic and an offset voltage Va
After O is added, it is input to the signal line driver 75, and the liquid crystal panel 77 is driven for each line selected by the scanning line driver 76.

The operation of the conventional video signal correction device configured as described above will be described below.

Assume that as a result of measuring the video signal level (V) and single screen luminance (1) characteristics of a liquid crystal panel for one color, the characteristic curve is as shown in (1) in FIG. 8(a). ■ Check the video signal input level to the LCD panel. When set in the range from to ■, the video signal undergoes the characteristic conversion shown within the dotted line. Lookup table memory to compensate for this characteristic transformation? 2b stores one table of data created by calculating the inverse transformation curve of the characteristic curve (FIG. 8(b)), and performs correction transformation on the video signal data for driving the liquid crystal panel. As a result, when the video signal that has undergone correction conversion is input to the liquid crystal panel, the video signal level-screen brightness characteristics will be as shown in (1) in Figure 8 (C), and linearity correction will be performed. .

(For example, Japanese Unexamined Patent Publication No. 62-209418) Problems to be Solved by the Invention However, with the above configuration, the video signal level-screen brightness characteristic changes due to changes in the temperature of the liquid crystal panel or changes in the video signal input level. It is difficult to perform an effective nearness correction in such a case.

The liquid crystal panel temperature is the video signal level in Figure 8(a).
When the screen brightness characteristic (1) is lower than when measured, the rising position of the video signal level-screen brightness characteristic changes as shown in (2) in FIG. 8(a). At this time, when correction is performed using the correction table shown in Figure 8 (C), the video signal level-screen brightness characteristic when the video signal that has undergone correction conversion is input to the liquid crystal panel is as shown in Figure 8 (C).
), and effective linearity correction is not performed.

Therefore, there has been a problem in that effective linearity correction cannot be performed when there is a change in the video signal level-screen brightness characteristic using only the correction data stored in the look-up table memory for l tables.

The present invention measures the video signal level-screen brightness characteristic for each change when there is a change in the video signal level-screen brightness characteristic due to changes in the temperature of the liquid crystal panel, changes in the video signal input level, etc., and reverses the characteristic curve. Conversion curves are calculated and stored in multiple look-up table memories, and a table selection memory is provided to arbitrarily select table numbers corresponding to changes in video signal level-screen brightness characteristics, allowing for effective nearness correction. The purpose is to carry out.

Means for Solving the Problems In order to solve the above problems, the video signal correction device of the present invention provides an A/D converter that outputs video signal data obtained by digitally converting a video signal that drives a dot matrix display.
A D converter and correction data for correcting display unevenness are stored in a plurality of tables, and a table is selected by table selection data input to the upper address line.
A look-up table memory outputs converted data obtained by performing correction conversion on the video signal data output from the A/D converter inputted to the lower address line, and a D/D converter converts the converted data into analog and outputs it to a dot matrix display.
A converter, a table selection memory that stores data relating input data and table numbers, and outputs table selection data for switching display unevenness correction to the input data to a lookup table memory, and a dot matrix. It is equipped with a temperature detector that measures the temperature of the type display panel, an A/D converter that outputs temperature data obtained by digitally converting the output signal of the temperature detector as input data to the table selection memory, and a lookup table. The multiple pieces of correction data stored in the memory are created by measuring the video signal level-screen brightness characteristics for each temperature level of the dot matrix display panel for each of the three primary color signals, and calculating the inverse conversion curve of the characteristic curve. This is the data.

Effect of the present invention With the above-described configuration, the temperature data obtained by digitally converting the temperature of the liquid crystal panel with the temperature detector and the A/D converter stores data that associates the input data with the table number. By referring to the table selection memory and inputting the output table number to the upper address line of the lookup table memory, a table for changes in temperature level is selected, and
The video signal data input to the lower address line that drives the dot matrix display is corrected using correction data created by calculating the inverse conversion curve of the video signal level-screen brightness characteristic curve for each individual temperature level of the panel. It will be converted.

Embodiment Hereinafter, a video signal correction device according to an embodiment of the present invention will be described with reference to the drawings.

SUMMARY OF THE INVENTION An object of the present invention is to perform effective linearity correction that compensates for changes in video signal level-screen brightness characteristics due to temperature changes in a liquid crystal panel.

FIG. 1 shows the configuration of a liquid crystal display device using a video signal correction device according to a first embodiment of the present invention. In FIG. 1, 12 is a video signal correction device;
12a is an A/D converter, 12b is a temperature detector, 12c is an A/D converter, 12d is a table selection memory, 12e is a look-up table memory, and 12f is a D/A converter. From the video signal to the three primary color video signals (for example, R, G,
B) is output from the video signal processing circuit 11 that creates A
The video signal data 13a that has been digitally converted by the /D converter 12a is input to the lower address of the lookup table memory 12e, and is corrected by referring to the table. Video signal data 13 that has undergone this correction
b undergoes analog conversion by the D/A converter 12f. Furthermore, the voltage adder 14 adds an offset voltage ■Ao that matches the threshold voltage indicating the rising position of the video signal level-screen brightness characteristic, and then inputs it to the signal line driver 15 and selects it by the scanning line driver 16. The liquid crystal panel 17 is driven for each line. At this time, the temperature of the liquid crystal panel is measured by the temperature detector 12b, and the result is sent to the A/D.
The temperature data obtained by digital conversion with the converter 12c is
By referring to the table selection memory 12d that stores data that associates input data and table numbers, the output table number is determined from the lookup table memory 1.
It is input to the upper address of 2e.

The operation of the video signal correction device configured as described above will be described below.

If the video signal level-screen brightness characteristics measured for two types of temperature levels are the characteristics shown in (1) and (2) in Figure 2 (aJ), the inverse of each characteristic curve is A conversion curve is calculated, and correction data shown in FIG. 2(b) for characteristic (1) and in FIG. 2(C) for characteristic (2) is created.

Although one color has been described above, the same applies to the other two colors.

In addition, the change Δ■7 in the threshold voltage, which is the rising position of the video signal level-screen brightness characteristic, with respect to the temperature T (K) of the liquid crystal panel is constant because there is a relationship of Δv, =EXP(-a/T). The temperature is set each time a threshold voltage change occurs, and the table number for that temperature level is stored in the table selection memory.In order to create correction data to be stored in the lookup table memory, the video signal level at that temperature level is set. - Measure screen brightness characteristics.

As described above, according to this embodiment, an A/D converter outputs video signal data obtained by digitally converting a video signal that drives a dot matrix display, and a plurality of correction data for correcting display unevenness are provided. The table is stored in a table, the table is selected according to the table selection data input to the upper address line, and the converted data is output by correcting and converting the video signal data of the A/D converter output input to the lower address line. A lookup table memory for converting data into analog data, a D/A converter for converting converted data into analog and outputting it to a dot matrix type display, and data for associating input data with table numbers are stored. A table selection memory that outputs table selection data for switching corrections to a lookup table memory, a temperature detector that measures the temperature of the dot matrix display panel, and a table that stores temperature data obtained by digitally converting the output signal of the temperature detector. It is equipped with an A/D converter that outputs as input data of the selection memory, and a plurality of pieces of correction data stored in the lookup table memory are divided into three primary color signals for each individual temperature level of the dot matrix display panel. This data is created by measuring the video signal level vs. screen brightness characteristics of A table corresponding to the change can be arbitrarily selected, and effective linearity correction can be performed by correction conversion with reference to the table.

A video signal correction device according to a second embodiment of the present invention will be described below with reference to the drawings.

The present invention further adds an offset voltage to the offset voltage Ao that is added to the video signal input to the liquid crystal panel so as to match the threshold voltage that indicates the rising position of the video signal level-screen brightness characteristic, so that the video signal level is low. The purpose of this invention is to perform effective nearness correction that compensates for changes in the video signal level-screen brightness characteristics when increasing the screen brightness level.

FIG. 3 shows the configuration of a liquid crystal display device using a video signal correction device according to a second embodiment of the present invention. In FIG. 3, 32 is a video signal correction device;
32a is an A/D converter, 32b is a voltage variable circuit, 32c
is an A/D converter, 32d is a table selection memory, 32e
is a look-up table memory, 32f is a D/A converter, and 32g is a voltage adder.

Video signal data 33a is output from a video signal processing circuit 31 that creates three primary color video signals (for example, R, CB) from a video signal, and is digitally converted by an A/D converter 32a.
is input to the lower address of the lookup table memory 32e, and is corrected by referring to the table. The video signal data 33b that has undergone this correction is D/
After being analog-converted by the A converter 32f, the offset voltage (2) is made to match the threshold voltage indicating the rising position of the video signal level-screen brightness characteristic by the voltage adder 34. , an offset voltage is further added by the voltage adder 32g to increase the screen brightness level when the video signal level is low. This offset voltage is generated by the voltage variable circuit 32b. Thereafter, the video signal is input to the signal line driver 35, and the liquid crystal panel 37 is driven for each line selected by the scanning line driver 36.

Also, at this time, the voltage data obtained by digitally converting the offset voltage generated by the voltage variable circuit 32b by the A/D converter 32c is used in the table selection memory 32d that stores data that associates the input data with the table number. By referencing, the output table number is input to the upper address of the lookup table memory 32e.

The operation of the video signal correction device configured as described above will be described below.

When the measured video signal level-screen brightness characteristic is as shown in FIG. 4(a), the offset voltage is VaO
In this case, calculate the inverse conversion curve of the characteristic curve of the part surrounded by the dotted line to create the correction data shown in Figure 4 Φ), and add the voltage Δ■ generated in the voltage variable circuit to the offset voltage. ,. In the case of adding , the inverse transformation curve of the characteristic curve of the part surrounded by the - dotted chain line is calculated to create the correction data shown in FIG. 4(C).

Although one color has been described above, the same applies to the other two colors.

In addition, the offset voltage ΔVA generated in the voltage variable circuit
Store the table number for 0 in the table selection memory.

As described above, according to this embodiment, the first embodiment includes a voltage variable circuit that generates an offset voltage according to a set level, and an analog adder that adds the offset voltage to the output signal of the D/A converter. and an A/D converter to which a voltage variable circuit is connected in place of the temperature detector and outputs voltage data obtained by digitally converting the offset voltage output as input data of the table selection memory. The several pieces of correction data stored in the uptable memo IJ'' measure the video signal level screen brightness characteristics for each of the three primary color signals, and create an inverse conversion curve of the characteristic curve to be referred to when changing the offset voltage. Because the data is calculated and created, a table for changes in the video signal level-screen brightness characteristics when the offset voltage is changed to raise the screen brightness level when the video signal level is low is created. Any number can be selected, and effective linearity correction can be performed by referring to the table and performing correction conversion.

A video signal correction device according to a third embodiment of the present invention will be described below with reference to the drawings.

An object of the present invention is to perform effective nearness correction that compensates for changes in video signal level-screen brightness characteristics due to changes in temperature of a liquid crystal panel, with only approximately doubling the capacity of a lookup table memory. .

FIG. 5 shows the configuration of a liquid crystal display device using a video signal correction device according to a third embodiment of the present invention. In FIG. 5, 52 is a video signal correction device;
52a is an A/D converter, 52b is a temperature detector, 52c is an A/D converter, 52d is a subtraction amount generation memory, 52e is a look-up table memory, 52f is a subtracter, 52g is a limiter circuit, and 52h is a D/D converter. It is an A converter. It is output from a video signal processing circuit 51 that separates a video signal into three primary color video signals (for example, R, G, and B), and is sent to an A/D converter 52a.
The video signal data 53a (for example, 8-bit data per color) that has undergone digital conversion is input to the lower address of the look-up table memory 52e, and is corrected by referring to the table. In the look-up table memory, the bit width of output data is larger than the bit width of input data (eg, 9 bits of output data). The corrected video signal data 53b is
After the value corresponding to the temperature change of the liquid crystal panel is subtracted by the subtracter 52f, the maximum value and minimum value are limited by the limiter circuit 52g in order to match the bit width of the input data of the lookup table memory, and the D/A Analog conversion is performed by converter 52h. Furthermore, the voltage adder 54 generates an offset voltage (2), which is made to match the threshold voltage indicating the rising position of the video signal level-screen brightness characteristic. is added,
The liquid crystal panel 57 is driven for each line inputted to the signal line driver 55 and selected by the scanning line driver 56. At this time, the temperature data obtained by digitally converting the result of measuring the temperature of the liquid crystal panel by the temperature detector 52b by the A/D converter 52c stores data that relates the input data and the amount subtracted by the subtracter. By referring to the subtraction amount generation memory 52d, the output subtraction amount is subtracted from the output data of the lookup table memory 52e.

The operation of the video signal correction device configured as described above will be described below.

If the video signal level screen brightness characteristic measured for a certain temperature level is the characteristic shown in (1) in Figure 6(a), an inverse transformation curve of the characteristic curve is calculated and
) or (d) (for example, 8 bits of input data, 9 bits of output data) is created. When the video signal input level to the liquid crystal panel is set in the range from VaO to ■, the video signal undergoes characteristic conversion shown within the dotted line, so in order to correct this, the subtracter 52f converts the output data of the lookup table memory 52e. The amount of subtraction (1) that is the difference between the output zero level shown in FIGS. 6(b) and (C) from
After subtracting, data values of 0 or less are limited to 0, and data values of 255 or more are limited to 255, so that they are within the range of 0 to 255. As a result, the correction characteristics seen from the look-up table memory, subtracter, and limiter circuit as a whole become the characteristics shown in FIG. 6(C).

In addition, when the temperature level of the liquid crystal panel changes and the video signal level screen brightness characteristic becomes the characteristic shown in (2) in Fig. 6 (a), the correction data shown in Fig. 6 (d) is applied. The subtraction amount (2) corresponding to this temperature level from the output data is stored in the lookup table memory 52e (Fig. 6).
A subtraction amount (1) that is the difference between the output zero levels shown in d) and (e) is subtracted. As a result, the correction characteristics seen from the look-up table memory, subtracter, and limiter circuit as a whole become the characteristics shown in FIG. 6(e).

Although one color has been described above, the same applies to the other two colors.

Also, since the change in threshold voltage Δ■, which is the rising position of the video signal level-screen brightness characteristic, is related to the temperature T (K) of the liquid crystal panel, there is a relationship of Δ■, -EXP(-a/T). , the temperature is set every time a certain threshold voltage change is shown, and the subtraction amount (corresponding to ■＾0+Δ■i) for that temperature level is stored in the subtraction amount generation memory.

As described above, according to this embodiment, an A/D converter outputs video signal data obtained by digitally converting a video signal that drives a dot matrix display, and correction data for correcting display unevenness is stored in a table. A look-up table memory outputs converted data obtained by correcting and converting the video signal data output from the A/D converter input to the address line to a data line having a bit number greater than the number of bits of the address line. , a subtracter that outputs the result of subtraction from the converted data value, a limiter circuit that outputs the result of limiting the output data value of the subtracter, and a dot matrix type display that converts the output of the limiter circuit into analog. A D/A converter that outputs the temperature of the dot matrix type display panel, a temperature detector that measures the temperature of the dot matrix display panel, an A/D converter that outputs temperature data obtained by digitally converting the output signal of the temperature sensor, and a temperature level It is equipped with a subtraction amount generation memory that stores data relating to the amount of subtraction from the conversion data and outputs the amount of subtraction in the subtracter according to the input of temperature data, and the correction data stored in the lookup table memory The data was created by measuring the video signal level-screen brightness characteristics of the dot matrix display panel for each of the three primary color signals and calculating the inverse conversion curve of the characteristic curve. When there is a change in the screen brightness characteristics, the amount of subtraction corresponding to the change can be arbitrarily selected and subtracted from the correction conversion output in the lookup table memory, which increases the capacity of the lookup table memory by about twice. , effective linearity correction can be performed.

Effects of the Invention As described above, the present invention includes an A/D converter that outputs video signal data obtained by digitally converting the video/signal that drives a dot matrix display, and a plurality of correction data for correcting display unevenness. Store it in the table of
The table is selected according to the table selection data input to the upper address line, and the A/
A lookup table memory that outputs converted data obtained by performing correction conversion on the video signal data output from the D converter, a D/A converter that converts the converted data into analog and outputs it to a dot matrix display, and input data and a table. A table selection memory that stores data relating numbers and outputs table selection data for switching display unevenness correction to input data to a lookup table memory, and a temperature that measures the temperature of a dot matrix display panel. It is equipped with a detector and an A/D converter that outputs temperature data obtained by digitally converting the output signal of the temperature detector as input data of the table selection memory, and further includes a plurality of corrections stored in the lookup table memory. The data is created by measuring the video signal level-screen brightness characteristics for each temperature level of the dot matrix display panel for each of the three primary color signals, and calculating the inverse conversion curve of the characteristic curve. When there is a change in the video signal level-screen brightness characteristic due to a temperature change, a table number corresponding to the change can be arbitrarily selected, and effective linearity correction can be performed by correction conversion with reference to the table.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a liquid crystal display device using a video signal correction device according to the first embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the correction conversion shown in FIG. 1, and FIG. A configuration diagram of a liquid crystal display device using the video signal correction device in the second embodiment, FIG. 4 is an explanatory diagram of the operation of the correction conversion in FIG. 3, and FIG. A configuration diagram of a liquid crystal display device using a signal correction device.
This figure is a block diagram of a liquid crystal display device using a conventional video signal correction device, and FIG. 8 is an explanatory diagram of the operation of the correction conversion shown in FIG. 7. 12...Video signal correction device, 12a...
・A/D converter, 12b...Temperature detector, 12
c...A/D converter, 12d...Table selection memory, 12e...Lookup table memory, 12f...D/A converter, 32b
...... Voltage variable circuit, 32g... Voltage adder, 52d... Subtraction amount generation memory, 52f.
...Subtractor, 52g...Limiter circuit.

Claims (1)

[Claims] (1) A that outputs video signal data obtained by digitally converting a video signal that drives a dot matrix display.
/D converter and correction data for correcting display unevenness are stored in a plurality of tables, and a table is selected according to the table selection data input to the upper address line, and the table is selected by the table selection data input to the lower address line. A look-up table memory that outputs converted data obtained by performing correction conversion on the video signal data output from the A/D converter, a D/A converter that converts the converted data into analog and outputs it to a dot matrix display, and an input. A table selection memory that stores data relating data and table numbers and outputs table selection data for switching display unevenness correction to the input data to the lookup table memory, and a temperature of a dot matrix display panel. and an A/D converter that outputs temperature data obtained by digitally converting the output signal of the temperature detector as input data to the table selection memory. . (2) The multiple pieces of correction data stored in the look-up table memory are obtained by measuring the video signal level-screen brightness characteristics for each temperature level of the dot matrix display panel for each of the three primary color signals, and inversely converting the characteristic curve. The video signal correction device according to claim 1, wherein the data is created by calculating a curve. (3) A that outputs video signal data obtained by digitally converting the video signal that drives the dot matrix display.
/D converter and correction data for correcting display unevenness are stored in a plurality of tables, and a table is selected according to the table selection data input to the upper address line, and the table is selected by the table selection data input to the lower address line. A look-up table memory that outputs converted data obtained by performing correction conversion on the video signal data output from the A/D converter, a D/A converter that converts the converted data into analog and outputs it to a dot matrix display, and an input. A table selection memory that stores data relating data and table numbers and outputs table selection data to the lookup table memory for switching display unevenness correction for input data, and an offset voltage according to a set level. an analog adder that adds the offset voltage to the output signal of the D/A converter; and an analog adder that adds the offset voltage to the output signal of the D/A converter, and digitally converts the offset voltage output from the voltage variable circuit to input the table selection memory. A video signal correction device comprising: an A/D converter that outputs data. (4) The multiple pieces of correction data stored in the lookup table memory measure the video signal level-screen brightness characteristics of the three primary color signals, and create an inverse conversion curve of the characteristic curve to be referenced when changing the offset voltage. 4. The video signal correction device according to claim 3, wherein the data is calculated and created. (5) A that outputs video signal data obtained by digitally converting the video signal that drives the dot matrix display.
A/D converter and correction data for correcting display unevenness are stored in a table, and conversion data obtained by correcting and converting the video signal data of the output of the A/D converter inputted to the address line is sent to the address. a look-up table memory for outputting to a data line having a number of bits greater than the number of bits for the line; a subtracter for outputting a result of subtraction from the converted data value; and a limit on the output data value of the subtracter. a limiter circuit that outputs the result of the measurement, a D/A converter that converts the output of the limiter circuit into analog and outputs it to a dot matrix display, a temperature detector that measures the temperature of the dot matrix display panel, and a temperature detector that measures the temperature of the dot matrix display panel; An A/D converter outputs temperature data obtained by digitally converting the output signal of the detector, and data relating the temperature level and the amount of subtraction from the conversion data is stored, and the input of the temperature data causes the subtracter to output the temperature data. A video signal correction device comprising: a subtraction amount generation memory that outputs a subtraction amount. (6) The correction data stored in the lookup table memory is data created by measuring the video signal level-screen brightness characteristics of the dot matrix display panel for each of the three primary color signals and calculating the inverse conversion curve of the characteristic curve. The video signal correction device according to claim 5, characterized in that: