JP2929105B2 - Liquid crystal drive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid crystal driving device for driving a dot matrix liquid crystal display panel.

2. Description of the Related Art Conventionally, a dot matrix liquid crystal display panel is generally used for a display unit of a portable small television receiver, a small electronic calculator, or the like. Since the vertical frequency of an NTSC television receiver is 60 Hz, the image of each field must be displayed every 17 [ms] (= 1/60 [s]), and the response speed of the liquid crystal display panel Is inevitably 17
It is desired to be sufficiently faster than [ms]. However, the current response speed of liquid crystal display panels is 50-100 [ms]
In addition, there is a disadvantage that an afterimage is seen when displaying a moving image due to the cumulative response.

Therefore, the following method has been proposed as a liquid crystal driving device that improves the response speed and eliminates afterimages. That is, when focusing on one pixel in the liquid crystal display panel, 1F (frame: “frame” in the specification of the present application indicates a period in which all picture elements forming one screen of the display panel are scanned in one way, For example, in a case where all the picture elements constituting one screen are scanned and displayed one by one for each field of a TV signal, one field of the TV signal is regarded as equal to one frame in the present application, and the TV signal is regarded as being equal to one frame. Is not necessarily coincident with one frame.), And the image data is refreshed once. The liquid crystal display panel has a cumulative responsiveness is well known, when representing the cumulative response as a model _{equation, y n = (1-K} ) x n + Ky n-1 ... (1) ( provided that, K : Constant x _n : Input image data y _n : Output image data (displayed data) When this equation (1) is Z-converted, Y (z) = (1−K) X (z) + KZ ⁻¹ Y (z) Y (z) = (1−K) X (z) / (1−KZ ⁻¹ ) (2) (where, Z ⁻¹ : delay operator for one frame) Liquid crystal display panel transfer function H
(Z) can be considered as H (z) = (1−K) / (1−KZ ⁻¹ ) (3) Here, if signal pre-processing is performed using a transfer function that is the reverse of the transfer function of the liquid crystal display panel, the response speed of display can be improved. That is, when the X (z) = (1- KZ -1) W (z) / (1-KZ -1) ... (4) The equation (4) to Z inverse _{transform, x n = (w n -Kw} n _-1 ) / (1-K) (5) This signal processing needs to be performed only for the moving image area. Further, the amplitude of the signal _xn thus obtained becomes large and it is impossible to display the signal on the liquid crystal display panel as it is. Therefore, it is necessary to make the amplitudes of _xn and wn _equal by a limiter.

The signal _xn as described above is effective in improving the responsiveness of a fast-moving image, but on the other hand, a small change is emphasized in an image having little motion and close to a still image. Therefore, there is a problem that noise increases. Therefore, the processing of the signal _xn as described above needs to be performed on pixels and regions where the change of the image is more than a certain level.

FIG. 3 shows a circuit configuration for realizing the above equation (5).
× M are quantized in pixel units, and 1 as a digital signal w _n
It is input to the + input side of the frame delay circuit 12 and the subtractor 13. One-frame delay circuit 12, the signal w _n input is delayed one frame, and outputs to the multiplier 14 as the signal w _n-1. The multiplier 14 multiplies the signal w _n−1 by K to obtain Kw _n−1 ,
It is input to the minus input side of the subtractor 13. In the subtractor 13, A /
A subtraction w _n −Kw _n−1 is performed based on the signal w _n from the D converter 11 and the signal K w _{n −1} from the subtractor 13, and the difference is output to the multiplier 15. The multiplier 15
The input signal is multiplied by 1 / (1−K) and output to the limiter 16. Limiter 16, when a signal sent from the multiplier 15 had exceeded the amplitude of the output signal w _n of the A / D converter 11, intended to limit this by calculation, the signal x _n and the output thereof Is sent to the segment driver 17. The segment driver 17 _responds to the signal _xn by using a liquid crystal display panel (LCD) 1
Drive 8 segment electrodes. This liquid crystal display panel 18
Are driven by a common driver 19.
The liquid crystal display panel 18, the common driver 19, and the A / D
The converter 11 operates in synchronization with the timing signal sent from the timing signal generation circuit 20.

Thus, the digital signal w output from the A / D converter 11
_n and the signal w _n−1 output from the one-frame delay circuit 12 are
Output to the motion detection circuit 21. This motion detection circuit 21
From the difference between the two signals w _n and w _n-1 having a time difference of one frame, it is determined whether or not the change (movement) of the image of the pixel is large. Container 15
To output a constant K.

For example an A / D converter 11 a digital signal w _n and the signal w _n-1 in which this delayed one frame in one frame delay circuit 12 outputs of the data the luminance component of a video signal having a weight of m bits Therefore, it is determined whether or not the change in the image is large based on whether or not these differences are equal to or more than a predetermined bit. The range that the constant K output from the motion detection circuit 21 can take according to this determination result is “0 ≦ K <1”. When it is determined that the change is small, the value of the constant K becomes “0”, and as a result, the output of the multiplier 14 becomes “0” and the multiplier 15 becomes a through bus, and performs signal processing for enhancing the image change. It is a circuit that does not perform. When it is determined that the change is large, the constant K is set to a value set in advance in the range of “0 <K <1”.

Hereinafter, an operation when it is determined that a change in image data is large will be described.

The response speed in one pixel of the liquid crystal display panel 18 is, for example,
If it is 50 [ms], the constant K in the above equation (5) is “K
= 1/2 ". Therefore, in the multiplier 14, the signal w _n−1 delayed by the one-frame delay circuit 12 becomes w _n−1 / 2, and the subtractor 13
In, the operation of w _n −w _n−1 / 2 is performed. The multiplier 15 multiplies 2 is input from the subtractor 13 the signal, and outputs the signal to the limiter 16 becomes "2w _n -w _n-1". Segment In the limiter 16, against the signal sent from the multiplier 15, for example, _{x n = (2w n -w n} -1) / 3 + 1/3 of the performed operations, the signal x _n obtained by the calculation The data is output to the driver 17 and displayed on the liquid crystal display panel 18.

[Problems to be Solved by the Invention] If the liquid crystal driving device has the above-described circuit configuration, when a change in an image is large, the liquid crystal display panel is driven by data that has been subjected to signal processing for enhancing the image change in advance. As a result, it is possible to remove the influence component that causes an afterimage, and it is possible to improve the response speed of the liquid crystal display panel.

However, the above-described liquid crystal driving device constitutes a circuit using two multipliers, and the two multipliers occupy a considerable size even on the driving device. If it is desired to make the value of the constant K variable, a logic element must be provided for each value of the constant K, and using two multipliers poses a problem in terms of miniaturization. I have.

The present invention has been made in view of the above circumstances, and has as its object to provide a liquid crystal driving device capable of simplifying a circuit configuration and reducing a circuit scale.

[Means for Solving the Problems] According to the present invention, in a liquid crystal driving device, after subtracting data of an (n-1) th frame from data of an nth frame, a K /
The liquid crystal display panel is driven by adding the data multiplied by (1-K) and the data of the n-th frame, and driving the liquid crystal display panel with the added data.

In addition, the present invention uses the n-th frame data from the n-th frame data.
After subtracting the data of one frame, the data multiplied by K / (1−K) and the data of the n-th frame are added, and in the liquid crystal driving device that drives the liquid crystal display panel with the added data, Is compared with the set reference value, if it is smaller than the set reference value, it is determined that the image is a still image area, and if it is larger than the set reference value, it is determined that the image is a moving image area.
It is characterized in that a constant K is generated for each of the B color signals.

[Operation] After subtracting the data of the (n-1) th frame from the data of the nth frame as described above, the data multiplied by K / (1−K) and the data of the nth frame are added. , The number of multipliers can be reduced to one, and the circuit configuration can be simplified.

Further, the still image area and the moving image area are detected by the motion detecting means, and a constant K is generated for each of the R, G, and B color signals based on the detection result. However, it is possible to appropriately improve the response speed.

First Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

The liquid crystal driving device shown in FIG.
Wherein the inverse transformation of the liquid crystal response shown in equation, that is, which is constituted based on _{x n = (w n -Kw n} -1) / formula (1-K). The expression _{(5), x n = (w n -Kw} n-1) / can be _{(1-K) + w n} ... (6) and be expressed. According to the present invention, a circuit is configured by using the equation (6).
This will be described with reference to the drawings. The same parts as those in FIG. 3 are denoted by the same reference numerals, and detailed description is omitted.

Analog video input signal as shown in FIG. 1 is converted into a digital signal w _n by the A / D converter 11, one-frame delay circuit 12, is input to the + input and the adder 31 of the subtractor 13 You. The signal w _n-1 delayed by one frame, for example, 1/60 [s] or 1/31 [s] by the one-frame delay circuit 12 is input to the minus input side of the subtractor 13. Subtractor
13, A / D converter signal w _n from 11 and one-frame delay circuit 1
The subtraction of “w _n −Kw _n−1 ” is performed with the signal Kw _n−1 from 2 and the difference is output to the multiplier 14 and the motion detection circuit 32. The motion detection circuit 32 generates an image when the subtraction result sent from the subtractor 13, that is, the subtraction result of the two signals w _n and w _n−1 having a time difference of one frame is _{equal to} or larger than a predetermined value. Is determined as a moving image area, and the value of the constant K is set to “0” in the still image area, and the value of the constant K is set in advance in the range of “0 <K <1” in the moving image area. Outputs the set value. The value of “K / (1−K)” based on the constant K output from the motion detection circuit 32 is
Is given as a multiplier value.

The multiplier 14 converts the signal input from the subtractor 13 into “K / (1
−K) ”, and outputs the result to the adder 31. This adder 31
Adding the signals from the digital signal w _n a multiplier 14 from the A / D converter 11, and outputs the addition result to the limiter 16.
The limiter 16 outputs a signal transmitted from the adder 31 to A /
_If the amplitude of the output signal wn of the D converter 11 exceeds the limit, the output is sent to the segment driver 17 as a signal _xn . Then, the liquid crystal display panel 18 is driven by the segment driver 17 and the common driver 19.

With the circuit configuration shown in FIG. 1, the response speed of the liquid crystal can be compensated for by one multiplier in the same manner as in the circuit of FIG. For this reason, the circuit scale can be significantly simplified, the cost can be reduced, and it is very advantageous in reducing the size.

Second Embodiment Next, a second embodiment of the present invention will be described.

In the second embodiment, an optimum constant K is obtained when the liquid crystal display panel 18 performs color display in the first embodiment shown in FIG. When the liquid crystal display panel 18 is a color display, the cell gap is adjusted by changing the thickness of the R, G, and B color filters provided corresponding to each pixel, and the R, G, and B wavelengths are changed for each pixel. The intensity of the wavelength light transmitted through each filter is equalized. Therefore, the responsiveness of the liquid crystal depends on the cell gap, and the responsiveness of each of the R, G, and B pixels does not always match. Therefore, it is not appropriate to process the R, G, B color signals with the same constant. Therefore, in the second embodiment, when the liquid crystal display panel 18 performs color display, the second
As shown in the figure, a constant generation circuit 38 is provided on the output side of the motion detection circuit 32 in the first embodiment of FIG. 1 so as to generate a different constant K for each of the R, G, and B color signals.

In FIG. 2, the motion detection circuit 32 determines whether the region is a moving image region or a still image region based on whether the value of the subtraction result sent from the subtractor 13 is equal to or greater than a predetermined value. Is output to the constant generation circuit 33. The constant generation circuit 33 generates a constant K based on a determination signal indicating whether a moving image area or a still image area is sent from the motion detection circuit 32. In the still image area, the constant K is set to “0”. In the moving image area, the value of the constant K is set to an optimum value according to the R, G, B color signals within the range of “0 <K <1”. This constant generation circuit
The optimum value of the constant K output from the pixel 33 is a value obtained from a transfer function in the cell gap of R, G, B of the liquid crystal display panel 18 and is set for each of the R, G, B color signals. Then, based on the constant K output from the constant generation circuit 33, “K /
(1−K) ”is given to the multiplier 14 as a multiplied value.

When performing the pre-processing to enhance the temporal change of the image data as described above, by changing the degree of enhancement for each of the R, G, B color signals according to each transfer function, the color display image In addition, appropriate response speed improvement is made.

[Effects of the Invention] As described above in detail, according to the present invention, after subtracting the data of the (n-1) th frame from the data of the nth frame,
By adding the data multiplied by K / (1−K) and the data of the n-th frame and driving the liquid crystal display panel based on the added data, the number of multipliers can be reduced to one. Thereby, the circuit configuration can be simplified and the circuit scale can be reduced.

Further, according to the present invention, when performing a pre-processing for detecting a moving image area by the motion detecting means and enhancing a temporal change of image data, the degree of enhancement for each of R, G, B color signals is assigned to each transfer function. Since it is changed in response to the above, it is possible to appropriately improve the response speed even for a color display image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of a first embodiment of the present invention, FIG. 2 is a block diagram showing a circuit configuration of a second embodiment of the present invention, and FIG. Is a block diagram showing a circuit configuration of a liquid crystal driving device for the present invention. 11 A / D converter, 12 1-frame delay circuit, 13
Subtractor, 14 Multiplier, 16 Limiter, 17 Segment driver, 18 Liquid crystal display panel, 19 Common driver, 31 Adder, 32 Motion detector, 33 Constant Generator circuit.

Claims (2)

(57) [Claims] 1. A subtraction means for subtracting data of an (n-1) th frame from data of an nth frame, a multiplication means for multiplying data outputted from the subtraction means by K / (1-K), and a multiplication means A liquid crystal display device comprising: an adder for adding data output from the controller to the data of the n-th frame; and a driver for driving the liquid crystal display panel with the data output from the adder. 2. The liquid crystal driving device according to claim 1, wherein the output data of said subtracting means is compared with a set reference value. A motion detecting means for judging a moving image area; and constant generating means for generating a constant K for each of R, G, B color signals for the data of the n-th frame based on a detection signal of the motion detecting means. A liquid crystal drive device characterized by the above-mentioned.