JP2003288060A - Liquid crystal gradation control circuit, and image display controller using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance register setting efficiency of a digital video signal of an image display device and to minimize circuit scale of the image display device in a gamma converter. <P>SOLUTION: In the gamma conversion performing digital gradation control, the number of set registers are reduced from all the number forming a gamma characteristic curve to the number of fixed points, register efficiency of software is enhanced and the circuit scale is minimized by approximating the gamma characteristic curve between the fixed points and interpolation points to be generated by using a linear interpolation circuit of the fixed points. In addition, gamma correction closer to a natural image is realized by having the setting registers by every color as RGB. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal gradation control circuit for gamma converting a video signal of a display device.

[0002]

2. Description of the Related Art In recent years, a small-sized liquid crystal display module having high definition and high image quality, which is used for portable information terminals such as mobile phones and PDAs, has emerged. Factors responsible for high image quality include the number of gradations and gamma correction that makes the image appear more natural. In order to obtain a high-definition image, it is essential to increase the number of gradations and have a more natural gamma correction function. However, if the number of gradations is increased and the true gamma correction is implemented, the circuit scale becomes large, which causes a problem for the trend toward miniaturization of the liquid crystal module.

Methods for controlling the gradation of liquid crystal are roughly classified into analog control and digital control. The analog grayscale control is to vary the Vref resistance value that generates the grayscale voltage level of the source driver so that the Vref is matched with the grayscale level of the digital video signal input to the source driver.
A voltage value is selected to drive the source line.

The digital gradation control is mainly composed of a register such as a flip-flop, and can change the gradation by gamma table conversion for outputting a registered value corresponding to an input value to realize an arbitrary gamma characteristic. It is possible.

Here, the gamma correction will be described. The gamma (γ) value is a tan θ when the reproduction characteristic is represented with the logarithmic value of the luminance of the subject as the horizontal axis and the logarithmic value of the luminance of the reproduced image as the vertical axis, where the inclination angle of the reproduction characteristic curve is θ.
Point to. When the brightness of the subject is reproduced faithfully, that is, when the vertical axis (output) increases by 1 with respect to the horizontal axis (input) 1 increasing area, a straight line with an inclination angle of 45 degrees is displayed on the graph, and tan45 When ° = 1, the gamma value becomes 1. When the gamma value is 1 or more, the tilt angle is 45 degrees or more, that is, a "hard" reproduction image tone having a stronger contrast feeling than the subject contrast is obtained, and conversely, when the gamma value is 1 or less, a flat "fewer contrast feeling" is obtained. It means that the image has a "soft" reproduction. That is, the gamma value indicates the degree of hardness of the image tone of the image reproduction system. The image pickup device, the film, the cathode ray tube, the liquid crystal, and the like each have a unique gamma value, and it is desirable that the gamma value becomes 1 throughout the entire system from shooting to image reproduction by appropriately adjusting these.

In the field of display, the gamma correction is to correct the change when a digital signal becomes an analog signal and is displayed on a display.
If you make a two-dimensional graph with input strength on the horizontal axis and brightness on the vertical axis, brightness should be a straight line that rises in direct proportion to the input strength, but the signal is actually input to the display. When displayed, the brightness is not directly proportional to the input and becomes a curve on the graph. The gamma value expresses this degree of bending, and the larger the number, the greater the degree of bending of the curve.
If the gamma value is 1.0, which is a direct proportional relationship between the input and the brightness, which is a straight line on the graph, the gamma value is generally adjusted to about 2.2. In printing and DTP, the gamma value is often adjusted to 1.8 before use, but generally the display gamma value is assumed to be 2.2. For example, the gamma value of a CRT display is 2.
2, which is 2.2 to 2.5 in general PC compatible machines and workstations. However, there is a special case where the display gamma value is set to about 1.8 by performing gamma correction on software.

[0007]

The analog gradation control and the digital gradation control of the liquid crystal will be described below with reference to the drawings.

FIG. 16 shows the generation of the Vref divided voltage of the source driver in the source driver for outputting the analog gradation. The Vref resistor is composed of a series resistor group from the power supply to the GND, the source voltage amplitude is applied to the source line, and the operational amplifier outputs a current for driving the actual source line load. The upper and lower variable resistors are used to change the contrast and brightness of the displayed image. A steady current flows through this Vref resistor, which also causes an increase in power consumption. In addition, it is necessary to invert the grayscale voltage by the inversion drive for each line or frame, which is peculiar to the liquid crystal, and one Vref resistor can generate two types of grayscale voltages of positive / negative polarity or two Vref resistors. There is also a method of generating positive and negative inversion gradations by using. Due to such a configuration, there is also a problem that the Vref current and the output current amount of the operational amplifier are different depending on the expression gradation of the video digital signal, which causes a power difference.

The digital gradation control will be described with reference to FIG. Input and output called gamma table is 1 in advance
Gamma correction is performed using a gamma table output value corresponding to an input digital video signal value by a register group that performs value conversion corresponding to the pair 1. As shown in FIG. 17, how much power nonlinearity the output characteristic has with respect to the linearity of the input value is set using this gamma table. Although the gamma characteristic curve can be set arbitrarily, the scale of the table circuit mainly composed of registers becomes large according to the number of bits of the input digital video signal, and by handling the color video signal, R / G / B Since it is necessary to change the correction degree for each color separately, it is necessary to have a circuit size three times as large as that for a single color. Further, when sequentially changing the gamma correction in the display specifications while the system is operating, it is necessary to re-set all the input values, which also burdens the software processing of the microcomputer.

[0010]

[Means for Solving the Problems] In order to solve this problem,
The present invention disclosed in the present application is as follows.

As a first invention, a gamma input setting section,
The gamma output setting unit, the inclination setting unit, the position detection circuit for the converted data, the signal switch circuit, and the linear interpolation circuit for outputting the gamma conversion data, the gamma input setting unit holds a plurality of set values. Then, the gamma output setting unit holds a plurality of setting values so as to form a gamma characteristic approximate straight line with respect to each setting value of the gamma input setting unit,
The inclination setting unit holds a plurality of linear change rates calculated from the respective set values of the gamma output setting unit corresponding to the respective set values of the gamma input setting unit, and the position detection circuit is configured to hold the gamma input setting unit. Detecting the converted data position on the gamma characteristic approximating straight line using a plurality of setting values of the unit, and generating a switch signal, the signal switch circuit using the switch signal, the gamma input setting unit, the gamma output The setting values required for linear interpolation are selected one by one from the setting values of the setting unit and the inclination setting unit, and the linear interpolation circuit uses the set values selected by the signal switch circuit to interpolate values. A liquid crystal gradation control circuit characterized by outputting gamma-converted data is calculated.

As a second invention, a gamma input setting section,
A gamma output setting section, a position detection circuit for the converted data,
The gamma input setting unit holds a plurality of set values, and the gamma output setting unit sets each set value of the gamma input setting unit. On the other hand, the position detection circuit holds a plurality of setting values so as to form a gamma characteristic approximation line on a one-to-one basis, and the position detection circuit uses the plurality of setting values of the gamma input setting unit to convert the converted data position on the gamma characteristic approximation line. Is detected to generate a switch signal, and the inclination calculation switch circuit uses the switch signal to determine a set value required for linear interpolation from the set values of the gamma input setting section and the gamma output setting section. The linear interpolation circuit calculates the linear change rate using the selected setting values and the gamma input setting section and the gamma input setting section selected by the inclination calculation switch circuit. Serial By calculating the interpolated value by using the set values and the calculated linear rate of change of the gamma output setting unit, and a liquid crystal gray scale control circuits and outputs a gamma conversion data.

As a third invention, a gamma input setting unit,
It is composed of a gamma input superimposing circuit, a gamma output setting unit, a position detection circuit for the converted data, a slope calculation switch circuit, and a linear interpolation circuit for outputting the gamma conversion data. The gamma input setting unit inputs the initial value and the input value. The gamma input convolution circuit generates a plurality of setting values from the initial value and the input interval value, and the gamma output setting unit generates a plurality of setting values for each setting value of the gamma input setting unit. A plurality of set values are held so as to form a gamma characteristic approximate straight line on a one-to-one basis, and the position detection circuit uses the initial value and the plurality of set values generated by the gamma input superimposing circuit to make a gamma characteristic approximate straight line. A switch signal is generated by detecting the converted data position above, and the inclination calculation switch circuit uses the switch signal to output a plurality of the initial values and the gamma input superposition circuit. One of the set values required for linear interpolation is selected from among the fixed values and the set values of the gamma output setting unit, and the linear change rate is calculated using the selected set values, and the linear interpolation circuit Provides a liquid crystal gradation control circuit characterized by outputting gamma conversion data by calculating an interpolated value using the values selected and calculated by the inclination calculation switch circuit.

As a fourth invention, a gamma input setting section,
A gamma input superposition circuit, a gamma value setting section, a position detection circuit for the converted data, a gamma output calculation switch circuit,
The gamma input setting unit holds one initial value and one input interval value, and the gamma input superposition circuit includes a plurality of linear interpolation circuits that output gamma-converted data. A set value is generated, and the position detection circuit detects a converted data position on a gamma characteristic approximation line by using the initial value and a plurality of set values generated by the gamma input convolution circuit, and generates a switch signal. Then, the gamma output operation switch circuit calculates each set value after gamma correction for each set value generated by the gamma input convolution circuit based on the gamma value held in the gamma value setting unit, and outputs the switch signal. Using the initial value and the plurality of setting values generated by the gamma input superimposing circuit and the setting values after the gamma correction, the setting values required for linear interpolation are respectively shifted by one. By selecting and calculating a linear change rate using the selected setting value, the linear interpolation circuit, by calculating the interpolated value using the value selected and calculated by the gamma output calculation switch circuit, A liquid crystal gradation control circuit characterized by outputting gamma-converted data.

As a fifth invention, in a gamma converter comprising a gamma input setting section and a gamma output setting section, each of the gamma input setting section and the gamma output setting section comprises a plurality of registers, and the gamma output setting section. There is provided a liquid crystal gradation control circuit equipped with a gamma converter, which is characterized in that the register circuit scale is reduced by reducing the setting range of a plurality of setting values forming the.

As a sixth invention, in a gamma converter comprising a gamma input setting section and a gamma output setting section, each of the gamma input setting section and the gamma output setting section comprises a plurality of registers, and the gamma output setting section. The gamma converter is characterized in that the register circuit scale is reduced by reducing the setting range of the plurality of setting values forming the gamma output setting unit at the same time as reducing the setting range of the plurality of setting values forming the gamma output setting unit. A liquid crystal gradation control circuit is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In all the drawings for explaining the embodiments, the same reference numerals are assigned to those having the same function, and the repeated description thereof will be omitted.

(Embodiment 1) FIG. 1 illustrates gamma setting using linear approximation in a liquid crystal gradation control circuit according to a first embodiment of the present invention. The invention is based on digital gradation control. If the table values are set for all the input values, not only time is required for the gamma setting, but also the required circuit area becomes large. Therefore, in the present invention,
It is proposed that the minimum required points be set directly and that other points be approximated using linear interpolation. The inventions after the first embodiment will be explained by unifying the gamma setting using linear interpolation by setting five points.

Gamma input setting registers IN0, IN1,
For IN2, IN3, and IN4, gamma output setting registers OUT0, OUT1, and OUT in consideration of gamma characteristics
2, OUT3, OUT4 are set. The inclination setting registers INC0, INC1, INC2, INC3 are represented by (Equation 1) INCn = (OUTn + 1-OUTn) / STEPn (Equation 2) STEPn = INn + 1-INn. In the first embodiment, the value of INCn is also calculated and set by the software of the microcomputer.
Even if a linear approximation is used for a continuous gamma characteristic curve, there is practically no problem.

FIG. 2 is a block diagram illustrating the configuration of the liquid crystal gradation control circuit according to the first embodiment of the present invention. Using the converted data 11 that is an input value, the position detection circuit 15 that detects the position on the gamma characteristic curve that is linearly approximated, and the switch signal 17 that is output from the position detection circuit 15,
A signal switch circuit 16 for selecting the register value of the gamma input setting unit 12 and the value of the gamma output setting unit 13 necessary for linear interpolation, and the register of the gamma input / output set value and inclination setting unit 14 selected by the signal switch circuit 16. A linear interpolation circuit 18 that linearly interpolates the value and outputs gamma-converted data 19 that is an interpolated value.

First, the operation of the position detection circuit 15 will be described with reference to FIG. Using the gamma input setting register INn, it is detected at which position on the gamma characteristic curve that the converted data 11 is linearly approximated, and the switch signal 17 is detected.
Is a circuit that generates a selection signal for the signal switch circuit 16. An exclusive OR element 1B and an inverter 1C are configured with a comparator 1A corresponding to the number of each input register and a logic unit for logically operating the output thereof.

The comparator 1A receives the inputs A and B from
If A> B, the output H level is output, and if A ≦ B, the L level is output. Two points having different comparator outputs are detected by the exclusive OR element 1B (ExOR), and the result is output as the switch signal 17. Further, only when the maximum value is matched, only SW4 outputs "1" through the inverter 1C.

For example, the gamma input setting register value (IN
0, IN1, IN2, IN3, IN4) = (00h, 0
Fh, 1Fh, 2Fh, 3Fh), and the converted data Rd
Is 28h, the comparator output becomes L, L, L, H, H in order from the top as shown in FIG. 3, and each switch output is (SW0, SW1, SW2, SW3, SW4) = (0,
0, 1, 0, 0). Thus, only SW2 is turned on. That is, it is detected that Rd exists between IN2 = 1Fh and IN3 = 2Fh. The switches that are turned on for the value of Rd of the converted data 11 are shown in (Table 1).

[0024]

[Table 1]

As described above, the position detecting circuit 15 serves as a decoder for selecting the output position corresponding to the input signal.

Next, the signal switch circuit 16 and the linear interpolation circuit 18 will be described. Since these two circuits are very close in function, they are described in FIG. 4 at the same time. The signal switch circuit 16 outputs the switch signal 17, which is the position information on the gamma approximated straight line of the converted data 11 generated by the position detection circuit 15 described above, to the gamma input setting register I.
Nn, gamma output setting register OUTn, and inclination setting register INCn are used as selection conditions.

The signal switch circuit 16 selects an IN multiplexer 1D for selecting the gamma input setting register INn, an OUT multiplexer 1E for selecting the gamma output setting register OUTn, and an I for selecting the slope setting register INCn.
It is composed of the NC multiplexer 1F. Of the detected position information, SW4 = 1 is the gamma output setting register OU
Since it is used only when outputting T4, the values necessary for linear interpolation are gamma input setting registers IN0 to IN3,
The gamma output setting registers OUT0 to OUT4 and the inclination setting registers INC0 to INC3. INa is S
The output of the IN multiplexer 1D that selects IN0 to IN3 by W0 to SW3, and INCa is SW0 to SW
IN to select INC0 to INC3 and 00h by 4
The output of C multiplexer 1F and OUTa are SW
OU that selects OUT0 to OUT4 by 0 to SW4
It represents the output of the T multiplexer 1E. Switch signal SW
, And IN, INC, and OUT numbers correspond to each other, and the same number is selected in each multiplexer.

Next, the configuration of the linear interpolation circuit 18 will be shown. I
Output INa of N multiplexer 1D and converted data 11
Differencer 1G for calculating the difference of (Rd), its difference value and I
It is configured by a multiplier 1H that multiplies the output INCa of the NC multiplexer 1F and an adder 1I that calculates the sum of the multiplication value and the OUT multiplexer 1E. That is, the arithmetic expression used for the linear interpolation is represented by (Equation 3).

(Equation 3) Yd = INCa × (Rd−INa) + OUTa The circuit configuration shown in FIG. 4 embodies this equation. The circuit configuration is not limited to this as long as it is a circuit configuration expressing the above formula. For example, the multiplier 1H may be configured to add the value of the difference value (Rd-INa) by the value of the slope INCa.

The operation of the two circuits shown in FIG. 4 is briefly shown in Table 2.

[0031]

[Table 2]

The gamma value is set to 2.2. Rd = 28
In the case of h, the gamma conversion data 19 calculated by INC2 × (28h−IN2) + OUT2 is output. Rd = I
In the case of N4, INCa = 00h, OUTa = OUT
4 is selected and the value of Yd = OUT4 is set. The operation shown in (Table 2) is summarized as a gamma characteristic as shown in FIG. 5, and the points except the fixed points (P0 to P4) are linearly stored. Note that the fixed points output the values OUT0 to OUT4 as they are.

FIG. 6 shows a register configuration in the case where each RGB has a gamma characteristic. Gamma input setting register 1J for each RGB, gamma output setting register 1K for each RGB, RG
In the B-specific inclination setting register 1L, the RGB switch circuit 1M selectively outputs. If you want to load the settings for each color of RGB, switch Ron, Gon, and Bon respectively.

Although the accuracy cannot be expected if there are few polygonal line approximation points, the contrast of the display image can be changed by changing the maximum value / minimum value amplitude of the approximation line and setting each in the gamma output register. . Brightness can be adjusted by setting a uniform offset value in all gamma output registers. Needless to say, it can be used as a gamma correction circuit for a display device such as a PDP or an organic EL because it is a digital gradation control regardless of the liquid crystal.

In this way, by linearly approximating the gamma characteristic with a small number of set points and digitally controlling the gamma characteristic, the number of registers to be set can be reduced and the software processing load on the microcomputer side can be reduced. For example, when it is necessary to sequentially change the gamma setting according to the input digital video signal, the gamma characteristic can be approximately realized with a small number of points, so the number of settings from the microcomputer can be reduced and communication with the microcomputer can be reduced. The number of times will be reduced, and the burden of software processing will be lightened. Further, by reducing the number of registers, the circuit scale and cost can be reduced.

(Second Embodiment) FIG. 7 shows the configuration of a liquid crystal gradation control circuit according to a second embodiment of the present invention. The difference from the first embodiment is that the tilt setting is calculated by hardware each time without holding the tilt setting register. That is, the inclination calculation function is added to the signal switch circuit 16 to change the inclination calculation switch circuit 2
6 Similar to the first embodiment, each output is INa,
OUTa and INCa.

FIG. 8 shows the inclination calculation switch circuit 26.
Described in. Similar to the case of the first embodiment, but
Since there is no tilt setting register, the tilt calculation circuit 24 does INC
The configuration is such that a is calculated. To calculate the slope, assuming that the slope is A, generally two points (X0, Y0) and (X1,
Since Y1) is calculated as (Equation 4) A = (Y1−Y0) / (X1−X0), in the slope calculation circuit 24, the gamma input / output setting register value selected by the switch signal 17 and one of them INCa is calculated from the upper setting register value. Therefore, the IN multiplexer 2D and OUT
This can be realized by configuring the multiplexer 2E in two stages and shifting the selected gamma input setting value as shown in FIG. By doing so, the same signal as in the first embodiment can be delivered to the linear interpolation circuit 18.

FIG. 9 shows the internal structure of the inclination calculation circuit 24. The selected INn and the upper INn + 1 are used as the gamma input setting values, and the selected OUTn and the upper OUT are used as the gamma output setting values.
n + 1 is used. Output difference value (OUTn + 1-OUT
The slope setting value INCa is calculated by dividing n) by the input difference value (INn + 1−INn).

(Embodiment 3) FIG. 10 shows a third embodiment of the present invention.
3 shows a configuration of a liquid crystal gradation control circuit of the embodiment. The difference from the second embodiment is that the gamma input setting unit 3
2, the input initial value IN0 is used as the gamma input setting register and the input setting interval value STEP0 is used as the step setting register instead of all the input setting values. That is, in the first and second embodiments, each gamma input setting register can individually set an arbitrary value by changing the setting, whereas in the third embodiment, the interval between the gamma input setting register values is fixed and fixed. By doing so, the number of register settings is reduced. This embodiment is effective for a display device that does not change the gamma value so much. The gamma input superimposing circuit 34 is a circuit for adding the input setting interval value STEP0 by a fixed number of points to the gamma input initial value IN0, and the internal configuration is shown in FIG. The adder is (fixed number-
Only 1) is required.

(Fourth Embodiment) FIG. 12 shows the configuration of a liquid crystal gradation control circuit according to the fourth embodiment. Third
The difference from the above embodiment is that a gamma value setting unit 43 and a gamma output operation switch circuit 46 are provided instead of the gamma output setting unit 13. FIG. 13 shows the circuit operation.

The IN multiplexers 4D and 4E are used as selectors selected by the switch signal 17. In order to perform the inclination calculation, the gamma input set value INn and the set value INn + 1 above the gamma input set value INn + 1 are selected. Therefore, the gamma input setting value is
It is shifted by the multiplexer 4E. The values calculated by the gamma value setting unit GAMMA0 and the gamma calculation units 4B and 4C are set as gamma output setting values OUTn and OUTn + 1. The inclination setting circuit INCa is output from the inclination calculation circuit 24 using the gamma input setting values INn and INn + 1 and the gamma output setting values OUTn and OUTn + 1.

The gamma input setting unit 42 may be either the gamma input setting unit 13 of the first embodiment or the gamma input setting unit 32 of the third embodiment.

(Fifth Embodiment) FIG. 14 shows a fifth embodiment of the present invention.
6 shows a gamma converter used in the liquid crystal gradation control circuit of the embodiment. For ease of explanation, description will be given using five fixed points. Originally, since each fixed point gamma output setting value OUTn has a setting range of n bits, it is possible to realize a gamma characteristic having a downward slope to the extreme. In the analog gradation control, there is inversion driving (line inversion, frame inversion, etc.) peculiar to liquid crystal, and a positive / negative polarity gamma characteristic curve is required. Therefore, a right downward gamma characteristic curve is also required. in the case of,
Since the gamma correction is applied to the digital video signal itself, not to the analog gradation control, it is sufficient if the gamma characteristic with a rightward rise can be realized. For example, each gamma output setting value O
Set the range of UTn centered around a certain reference point
Even if it is / 2, there is practically no problem. Furthermore, even if the setting range is set to 1/4 of the conventional range, the gamma value that can be realized is limited, but in practice, a gamma characteristic that can be sufficiently endured can be realized. That is, the bit range is reduced by limiting the output range of the gamma output setting value OUTn and optimizing the output range to a practical range. When the output range is set to 1/2 or 1/4, the bit scale of the setting register becomes n-1 or n-2, and the register circuit scale can be reduced accordingly.

(Embodiment 6) FIG. 15 shows a sixth embodiment of the present invention.
6 shows a gamma converter used in the liquid crystal gradation control circuit of the embodiment. In the fifth embodiment, the bit scale is reduced by limiting the output range of the gamma output setting value OUTn. However, in the sixth embodiment, the definition range of the gamma input setting value INn is not the entire n bits. We propose to reduce the register circuit on the gamma input side by limiting the range.

If the definition range of the gamma input set value INn and the gamma output set value OUTn are set to 1/4 of the whole,
The gamma characteristic within the area surrounded by the straight line as shown in FIG. 15 can be expressed. Practically, if the gamma setting can be expressed within the enclosed range, the bit scale on the input side and the output side can be reduced, and the overall register circuit scale can be reduced.

[0046]

As described above, the liquid crystal gradation control circuit of the present invention and the image display control apparatus using the same use the linear approximation interpolation in the gamma conversion of the digital video signal of the image display device. It is possible to improve the software setting efficiency and reduce the circuit scale.

[Brief description of drawings]

FIG. 1 is a diagram of gamma setting using linear approximation used in a liquid crystal gradation control circuit according to a first embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a liquid crystal gradation control circuit according to a first embodiment of the present invention.

FIG. 3 is a configuration diagram of a position detection circuit of the liquid crystal gradation control circuit according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a signal switch circuit and a linear interpolation circuit of the liquid crystal gradation control circuit according to the first embodiment of the present invention.

FIG. 5 is a linear approximation gamma output diagram by the liquid crystal gradation control circuit according to the first embodiment of the present invention.

FIG. 6 is a block diagram of a gamma setting register for each RGB used in the liquid crystal gradation control circuit according to the first embodiment of the present invention.

FIG. 7 is an overall configuration diagram of a liquid crystal gradation control circuit according to a second embodiment of the present invention.

FIG. 8 is a configuration diagram of a tilt calculation switch circuit of a liquid crystal gradation control circuit according to a second embodiment of the present invention.

FIG. 9 is a configuration diagram of a tilt calculation circuit of a liquid crystal gradation control circuit according to a second embodiment of the present invention.

FIG. 10 is an overall configuration diagram of a liquid crystal gradation control circuit according to a third embodiment of the present invention.

FIG. 11 is a configuration diagram of a gamma input superposition circuit of a liquid crystal gradation control circuit according to a third embodiment of the present invention.

FIG. 12 is an overall configuration diagram of a liquid crystal gradation control circuit according to a fourth embodiment of the present invention.

FIG. 13 is a configuration diagram of a gamma output operation switch circuit of a liquid crystal gradation control circuit according to a fourth embodiment of the present invention.

FIG. 14 is a gamma setting range diagram in the gamma converter of the liquid crystal gradation control circuit according to the fifth embodiment of the present invention.

FIG. 15 is a diagram of a gamma setting range and a gamma characteristic representable range in a gamma converter of a liquid crystal gradation control circuit according to a sixth embodiment of the present invention.

FIG. 16 is a diagram showing a conventional example of analog gradation control for the present invention.

FIG. 17 is a diagram showing a conventional example of digital gradation control for the present invention.

[Explanation of symbols]

1A comparator 1B Exclusive OR element 1C inverter 1D IN multiplexer 1E OUT multiplexer 1F INC multiplexer 1G differencer 1H multiplier 1I adder Gamma input setting register for each 1J RGB Gamma output setting register for each 1K RGB 1L RGB tilt setting register 1M RGB switch circuit 2D IN multiplexer 2E OUT multiplexer 4B gamma calculator 4C gamma calculator 4D IN multiplexer 4E IN multiplexer 11 Converted data 12 Gamma input setting section 13 Gamma output setting section 14 Tilt setting section 15 Position detection circuit 16 signal switch circuit 17 Switch signal 18 Linear interpolation circuit 19 Gamma conversion data 24 Slope calculation circuit 26 Tilt calculation switch circuit 32 Gamma input setting section 34 Gamma input superposition circuit 42 Gamma input setting section 43 Gamma value setting section 46 Gamma output calculation switch circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 9/69 H04N 9/69 5C080 F term (reference) 2H093 NA32 NA33 NA51 NC25 ND06 ND49 5C006 AF46 BB11 BC16 FA43 5C021 PA17 PA53 PA58 PA62 PA66 PA67 PA80 PA87 PA89 RB03 XA34 5C058 AA06 BA13 BB14 5C066 AA03 CA01 EC05 GA01 KA12 KD06 KE02 KE03 KE08 KE09 KM13 KP02 5C080 AA10 BB05 DD01 DD22 EE29 JJ02 JJ03 JJ05 JJ05

Claims (26)

[Claims] 1. A gamma input setting section, a gamma output setting section, an inclination setting section, a position detection circuit for the converted data, a signal switch circuit, and a linear interpolation circuit for outputting the gamma converted data. The gamma input setting unit holds a plurality of setting values, and the gamma output setting unit holds a plurality of setting values so as to form a gamma characteristic approximation straight line for each setting value of the gamma input setting unit. The inclination setting unit holds a plurality of linear change rates calculated from the respective set values of the gamma output setting unit corresponding to the respective set values of the gamma input setting unit, and the position detection circuit is configured to hold the gamma input setting unit. Detecting a converted data position on the gamma characteristic approximating straight line using a plurality of setting values of the unit, and generating a switch signal, the signal switch circuit using the switch signal, the gamma input setting unit, the One of the set values required for the linear interpolation is selected from the set values of the gamma output setting unit and the slope setting unit, and the linear interpolation circuit uses the set values selected by the signal switch circuit. A liquid crystal gradation control circuit characterized by outputting gamma conversion data by calculating an insertion value. 2. The means for holding a plurality of set values of the gamma input setting unit, the gamma output setting unit, and the inclination setting unit is configured by a register group having variable set values. 1. The liquid crystal gradation control circuit described in 1. 3. An image display control device equipped with the liquid crystal gradation control circuit according to claim 2. 4. The liquid crystal floor according to claim 1, wherein the gamma input setting unit, the gamma output setting unit, and the inclination setting unit are composed of a register group whose set values are individually variable for each of RGB colors. Key control circuit. 5. An image display control device equipped with the liquid crystal gradation control circuit according to claim 4. 6. A gamma input setting unit, a gamma output setting unit, a position detection circuit for data to be converted, a slope calculation switch circuit, and a linear interpolation circuit for outputting gamma conversion data. Holds a plurality of set values, and the gamma output setting section holds a plurality of set values so as to form a gamma characteristic approximate straight line in a one-to-one correspondence with each set value of the gamma input setting section. A circuit detects a converted data position on a gamma characteristic approximation line using a plurality of setting values of the gamma input setting unit to generate a switch signal, and the inclination calculation switch circuit uses the switch signal to generate the switch signal. From the setting values of the gamma input setting section and the gamma output setting section, one setting value required for linear interpolation is selected, and the linear change rate is calculated using the selected setting value. The linear interpolation circuit calculates an interpolation value by using each set value of the gamma input setting unit and the gamma output setting unit selected by the slope calculation switch circuit and the calculated linear change rate, A liquid crystal gradation control circuit characterized by outputting gamma-converted data. 7. The liquid crystal floor according to claim 6, wherein the means for holding a plurality of set values of the gamma input setting unit and the gamma output setting unit is composed of a register group having variable set values. Key control circuit. 8. An image display control device equipped with the liquid crystal gradation control circuit according to claim 7. 9. The liquid crystal gradation control circuit according to claim 6, wherein the gamma input setting unit and the gamma output setting unit are composed of a register group whose set values are individually variable for each of RGB colors. 10. An image display control device equipped with the liquid crystal gradation control circuit according to claim 9. 11. A gamma input setting unit, a gamma input superimposing circuit, a gamma output setting unit, a position detection circuit for the converted data, a slope calculation switch circuit, and a linear interpolation circuit for outputting the gamma conversion data. The gamma input setting unit holds an initial value and an input interval value one by one, the gamma input superposition circuit generates a plurality of setting values from the initial value and the input interval value, and the gamma output setting unit A plurality of setting values are held so as to form a gamma characteristic approximate straight line for each setting value of the gamma input setting unit, and the position detection circuit is generated by the initial value and the gamma input superposition circuit. The converted data position on the gamma characteristic approximation line is detected using a plurality of set values to generate a switch signal, and the inclination calculation switch circuit uses the switch signal to set the initial value and A set value required for linear interpolation is selected from the plurality of set values generated by the comma input superposition circuit and each set value of the gamma output setting section, and the selected set value is used. A liquid crystal floor characterized in that it calculates a linear change rate, and the linear interpolation circuit outputs an gamma conversion data by calculating an interpolated value using the value selected and calculated by the inclination calculation switch circuit. Key control circuit. 12. A means for holding an initial value and an input interval value of the gamma input setting section and a plurality of setting values of the gamma output setting section is configured by a register group having variable setting values. The liquid crystal gradation control circuit according to claim 11. 13. An image display control device equipped with the liquid crystal gradation control circuit according to claim 12. 14. An initial value and an input interval value of the gamma input setting unit and a plurality of setting values of the gamma output setting unit are RG.
12. The liquid crystal gradation control circuit according to claim 11, wherein each B color is composed of a variable register group individually. 15. An image display control device equipped with the liquid crystal gradation control circuit according to claim 14. 16. A gamma input setting unit, a gamma input superposition circuit, a gamma value setting unit, a position detection circuit for the converted data, a gamma output operation switch circuit, and a linear interpolation circuit for outputting the gamma conversion data. The gamma input setting unit holds an initial value and an input interval value one by one, the gamma input superposition circuit generates a plurality of set values from the initial value and the input interval value, and the position detection circuit is , A switch signal is generated by detecting a converted data position on a gamma characteristic approximation line using the initial value and a plurality of setting values generated by the gamma input convolution circuit, Based on the gamma value held in the value setting unit, each set value after gamma correction is calculated for each set value generated by the gamma input convolution circuit, and the initial value is calculated using the switch signal. A set value required for linear interpolation from the plurality of set values generated by the gamma input superposition circuit and the set values after the gamma correction, and the selected set values. Is calculated, and the linear interpolation circuit outputs gamma conversion data by calculating an interpolated value using the value selected and calculated by the gamma output calculation switch circuit. The liquid crystal gradation control circuit. 17. A means for holding an initial value and an input interval value of the gamma input setting unit and each setting value of the gamma value setting unit is constituted by a register group having a variable setting value. Item 16. A liquid crystal gradation control circuit according to item 16. 18. An image display control device equipped with the liquid crystal gradation control circuit according to claim 17. 19. The initial value and input interval value of the gamma input setting unit and each setting value of the gamma value setting unit are configured by a register group that is individually variable for each of RGB colors. LCD gradation control circuit. 20. An image display control device equipped with the liquid crystal gradation control circuit according to claim 19. 21. A gamma converter comprising a gamma input setting unit and a gamma output setting unit, wherein the gamma input setting unit and the gamma output setting unit are each composed of a plurality of registers, and a plurality of units forming the gamma output setting unit are provided. A liquid crystal gradation control circuit equipped with a gamma converter characterized by reducing the register circuit scale by reducing the setting range of the setting value of. 22. The liquid crystal gradation control circuit according to claim 1, wherein the gamma converter according to claim 21 is mounted. 23. An image display control device equipped with the liquid crystal gradation control circuit according to claim 22. 24. In a gamma converter including a gamma input setting unit and a gamma output setting unit, the gamma input setting unit and the gamma output setting unit are each composed of a plurality of registers, and a plurality of units forming the gamma output setting unit are provided. Liquid crystal gradation equipped with a gamma converter characterized by reducing the register circuit scale by reducing the setting range of a plurality of setting values forming the gamma output setting unit at the same time as reducing the setting range of the setting value of Control circuit. 25. A liquid crystal gradation control circuit according to claim 1, wherein the gamma converter according to claim 24 is mounted. 26. An image display control device equipped with the liquid crystal gradation control circuit according to claim 25.