JP3502627B2 - Liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device for displaying an image using a liquid crystal display panel, and more particularly to an acceleration driving method capable of improving the response speed of the liquid crystal display panel.

[0002]

2. Description of the Related Art In recent image display devices, a liquid crystal display device (LCD) has been widely used instead of a cathode ray tube (CRT) for both PC and TV.
An LCD applies an electric field to a liquid crystal layer having an anisotropic dielectric constant that is injected between two substrates, and controls the intensity of the electric field to control the amount of light transmitted through the substrates. A display device for obtaining an image signal.

At present, various studies have been conducted to make the performance of LCDs as close as possible to a cathode ray tube, and one of them is to improve the response speed of liquid crystals. Various attempts have been made to speed up the response speed of the liquid crystal, such as optimizing the liquid crystal material and reducing the thickness (cell gap) of the liquid crystal cell, but on the other hand, the driving method is independent of the performance of the liquid crystal itself. Studies have been conducted to improve the response speed by devising the.

In order to improve the problem of the response speed of the liquid crystal, the input image of the current vertical period determined in advance according to the combination of the input image signal of the previous vertical period and the input image signal of the current vertical period. A liquid crystal driving method is known in which a driving voltage higher (overshot) or lower (undershot) driving voltage than a grayscale voltage for a signal is supplied to a liquid crystal display panel. Hereinafter, in this specification, this driving method is defined as acceleration driving.

For example, in Japanese Patent Laid-Open No. 4-365094, an image memory for storing one frame of display digital image data, two inputs of the digital image data and image data read from the image memory with a delay of one frame are input. R storing a table storing image data corresponding to
When the image data changes, the optimum image data stored in advance according to the direction and degree of the change is read out and the liquid crystal panel is driven, so that the light transmittance rises or rises. It has been proposed to make the fall steep in a necessary and sufficient range to improve the response speed of the liquid crystal.

Generally, in a liquid crystal display panel, it takes a long time to change from one halftone to another halftone, the halftone cannot be displayed within one field (about 16.6 msec), and an afterimage is generated. There is a problem that not only the generated halftone but also the halftone cannot be correctly displayed, but by using the above-described acceleration drive, the target halftone can be displayed in a short time.

[0007]

By the way, it is known that the response speed of liquid crystal has a very large temperature dependency,
Even if the temperature of the liquid crystal panel changes, there is a liquid crystal panel driving device which controls the response speed of gradation change to an optimum state without spoiling the display quality, for example.
It is described in Japanese Patent No. 318516.

This is a RAM for storing one frame of display digital image data, a temperature sensor for detecting the temperature of the liquid crystal panel, the digital image data and the RAM.
From the image data read out one frame later, and when the image data of this time changes compared with the image data of one frame before, the image data of this time is changed in the changing direction to the temperature detected by the temperature sensor. A data conversion circuit for carrying out emphasis conversion in accordance therewith is provided, and the liquid crystal panel is driven for display based on the image data output from the data conversion circuit.

That is, the temperature of the liquid crystal panel detected by the temperature sensor is, for example, three levels of values Th, Tm, Tl (Th>
Tm> Tl), and correspondingly, the mode signal output from the A / D converter to the data conversion circuit is set to Mh, Mm, and Ml, and the ROM of the data conversion circuit stores the current image data and one frame. By storing and setting the table of the image data having the delayed image data as the designated address for the number of mode signals “3” in advance, the table corresponding to the input mode signal is selected, and the table in this table is selected. The image data written in the address position where the image data of 1) and the image data delayed by one frame are designated addresses are read and output to the drive circuit of the liquid crystal panel.

However, the above-mentioned JP-A-4-3185.
In the one disclosed in Japanese Patent No. 16, the mode signals Mh, Mm, and Ml corresponding to the three levels of the detected temperatures Th, Tm, and Tl (Th>Tm> Tl) are generated, and the mode signals Mh and Mm are generated. , Ml, the emphasis conversion parameters are switched, so that, for example, when the detected temperature of the liquid crystal panel is unstable, and when the process goes back and forth between the stages Th, Tm, and Tl, the mode signals Mh and Mm are switched. , Ml also change frequently, and the emphasis conversion parameter read from the ROM changes even for the same gradation change. As a result, there is a problem in that an image displayed on the liquid crystal panel causes a flicker or other symptom to deteriorate the image quality.

The present invention has been made in view of the above problems, and even when the detected temperature in the apparatus is unstable,
Provided is a liquid crystal display device capable of stably variably controlling enhancement conversion parameters and improving the quality of a display image.

[0012]

The first invention of the present application is a liquid
A liquid crystal display device that displays an image using a crystal display panel.
Therefore, the temperature detecting means for detecting the temperature inside the apparatus, and the temperature
Hysteresis processing is applied to the temperature detected by the detection means.
Control means for generating a control signal, and
Control signal generated by the control means and the input image data
Depending on the combination of gradation transitions before and after one vertical period
Current vertical period using the emphasis conversion parameter determined by
By performing emphasis conversion on the input image data of
Enhancement conversion for compensating optical response characteristics of the liquid crystal display panel
And a writing gradation determining means for obtaining data
And A second invention of the present application is the write gradation determining means.
Is the gradation before and after one vertical period of the input image data
Depending on the combination of transitions, the input image data
Enhanced conversion data that compensates the optical response characteristics of the liquid crystal display panel.
For each of a plurality of predetermined temperature ranges for conversion into data
Tables with different emphasis conversion parameters stored in
A memory and a control signal generated by the control means.
Select one of the table memories
And a switching unit that switches the output by the switching unit.
Read by referencing the table memory
Using the enhanced conversion parameters
The enhanced conversion data for the
It is characterized in that it is supplied to a liquid crystal display panel. Of the present application
In a third aspect of the present invention, the writing gradation determination unit is configured to output the input image.
Combination of gradation transition before and after one vertical period of data
According to the input image data of the liquid crystal display panel
To convert to enhanced conversion data that compensates for optical response characteristics
, Different emphasis conversion for each of a plurality of predetermined temperature ranges
A table that stores parameters for each of the multiple reference table areas.
And a control signal generated by the control means
One of the plurality of reference table areas based on
And a switching unit for selectively switching the
The reference table area of the switched table memory
The emphasis conversion parameter read by referring to
Using the enhanced conversion data for the input image data
Obtained and supplied to the liquid crystal display panel as write gradation data
It is characterized by doing. A fourth invention of the present application is the above-mentioned
Bull memory has a transition of the representative gradation in the display data gradation
Emphasis conversion parameters for patterns are stored
It is characterized by A fifth invention of the present application is the control hand.
The steps are the temperature detected by the temperature detecting means and a predetermined threshold temperature.
The temperature is higher or lower than the predetermined threshold temperature.
When the detected temperature is continuously acquired more than a predetermined number of times,
Switching selection of emphasis conversion parameters corresponding to the detected temperature
It is characterized in that it outputs a control signal for Application
According to a sixth aspect of the present invention, the control means provides the temperature detection means.
With respect to the temperature detected by
It is characterized by correcting the error of. Seventh invention of the present application
Is the control means, according to the elapsed time after the power is turned on,
The error temperature to be corrected is variably controlled.
It

In the liquid crystal display device of the present invention, even if the detected temperature in the device is unstable, the emphasis conversion parameter can be variably controlled stably by adding hysteresis to the detected temperature in the device. It is possible to improve the quality of the displayed image.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The first embodiment of the present invention will be described below.
A detailed description will be given with reference to FIGS. 1 to 4. Here, FIG. 1 is a block diagram showing a schematic configuration of a main part of the liquid crystal display device of the present embodiment, FIG. 2 is a schematic explanatory diagram showing a table content of a ROM in the liquid crystal display device of the present embodiment, and FIG. FIG. 4 is an explanatory view showing the relationship between the detected temperature and the level at which the emphasis conversion parameter is switched in the liquid crystal display device of FIG. 4, and FIG. 4 is a flowchart showing the hysteresis processing in the liquid crystal display device of the present embodiment.

In FIG. 1, reference numeral 1 denotes an RO which stores an enhancement conversion parameter corresponding to a gradation change of input image data.
M, 2 are a frame memory (FM), 3 is a comparison between the image data of the current field and the image data of the previous field read from FM2, and the emphasis conversion parameter corresponding to the comparison result (gradation transition) is read from the ROM1. An arithmetic unit 4 that reads out and determines / outputs emphasis data (corrected image data) is a liquid crystal that outputs a liquid crystal drive signal to the gate driver 6 and the source driver 7 of the liquid crystal panel 5 based on the emphasis data from the arithmetic unit 3. The controller.

Further, 8 is a thermistor for detecting the temperature inside the apparatus, and 9 is a voltage value (detection temperature) from the thermistor 8.
This is a microcomputer that performs a hysteresis process on the, and outputs a parameter control signal for performing switching control of the emphasis conversion parameter read from the ROM 1.

In the above configuration, the ROM 1 is composed of ROMs 1a to 1c in which three enhancement conversion parameters LEVEL 0 to LEVEL 2 corresponding to the internal temperature of the apparatus are stored. Each of the ROMs 1a to 1c is shown in FIG. As shown, a table storing the enhancement conversion parameters corresponding to the gradation transition of the input image data is stored (the number of display signal levels, that is, the number of display data is 25 bits of 8 bits).
6 gradations).

The arithmetic unit 3 adaptively switches and selects the ROMs 1a to 1c in accordance with the parameter control signal from the microcomputer 9, and performs the emphasis conversion according to the gradation transition before and after one field from the selected ROMs 1a to 1c. Read parameters,
Based on this, the corrected image data to be output to the liquid crystal controller 4 is determined.

For example, the parameter control signal from the microcomputer 9 indicates "LEVEL 0", the previous field data from the FM2 is "0", and the current field data of the input image data is "128". In this case, the arithmetic unit 3 can select the ROM 1a and obtain the enhanced conversion parameter 9 "output data of" 194 "".

The computing unit 3 creates an input / output table of 0 to 255 based on the emphasis conversion parameter from the ROM 1, determines corrected image data in which the emphasis conversion parameter data is added, and outputs it to the liquid crystal controller 4. To do.
For example, when there is no value (not assigned) in the table stored in the ROM 1 as in the case where the previous field data is “0” and the current field data is “100”, the linear complement is performed by the calculator 3. As a result, data of about "175" is output.

In the liquid crystal display device of the present embodiment, as shown in FIG. 3, LEVEL 0 of three stages according to the temperature inside the device is used.
Up to LEVEL 2 enhancement conversion parameters are prepared and stored in the tables of the ROMs 1a to 1c, respectively. The threshold temperatures for switching the emphasis conversion parameter are Thresh 0 and Thresh 1, but if the temperature inside the apparatus detected by the thermistor 8 is unstable near the threshold temperature, the emphasis conversion parameter (LE
There is a problem that VEL 0 to LEVEL 2) are frequently switched.

Therefore, in the present embodiment, hysteresis is added to the thermistor detection temperature in the microcomputer 9,
It is configured to generate a parameter control signal. The hysteresis process performed by the microcomputer 9 will be described below with the flowchart of FIG. In the present embodiment, it is assumed that the microcomputer 9 regularly acquires the in-apparatus temperature data (for example, about every 120 ms).

First, the temperature data from the thermistor 8 is acquired (step 1) and compared with the temperature data acquired previously (step 2). When the temperature data acquired this time is higher, that is, when the temperature inside the apparatus rises, the temperature data acquired this time is compared with the current upper limit temperature threshold value of LEVEL, Thresh (LEVEL) + α (step 3). Here, α is an arbitrary number set in advance.

If the temperature data acquired this time is larger, the current LEVEL is increased by 1 (step 4) and the process returns to step 1. If the temperature data acquired this time is smaller, the current LEVEL is maintained as it is (step 5), and the process returns to step 1.

On the other hand, if it is determined in step 2 that the temperature data acquired this time is lower, that is, if the temperature inside the apparatus has dropped, the temperature data acquired this time and the lower limit temperature threshold value of the current LEVEL, Thresh.
(LEVEL-1) + α is compared (step 6), and if the temperature data acquired this time is smaller, the current LEVEL
Is decremented by 1 (step 7) and the process returns to step 1. Also,
If the temperature data acquired this time is larger, the current L
The EVEL is maintained as it is (step 8), and the process returns to step 1.

For example, if the current emphasis conversion parameter is LE
If the newly read temperature is higher than the previously read temperature when it corresponds to VEL 1, Thresh 1
Compared with + α, if it is higher than this, LEVEL 2
Move to. If the newly read temperature is lower than the previously read temperature, it is compared with Thresh 0-α, and if it is lower than this, LEVEL 0 is entered.

As described above, in the present embodiment, since the detected temperature has a hysteresis by setting the temperature threshold to ± α according to the rise and fall of the temperature, the detected temperature rises and falls near the temperature threshold. Even if it is repeated, the enhancement conversion parameters (LEVEL 0 to L
It is possible to realize stable switching control of the enhancement conversion parameters (LEVEL 0 to LEVEL 2) without causing the EVEL 2) to change drastically, and it is possible to improve the image quality of the display image.

Next, a second embodiment of the present invention will be described in detail with reference to FIG. 5. The same parts as those of the first embodiment described above are designated by the same reference numerals and the description thereof will be omitted. Here, FIG. 5 is a flowchart showing the hysteresis process in the liquid crystal display device of the present embodiment.

The configuration of the liquid crystal display device of this embodiment is shown in FIG.
In addition, it is the same as that of the first embodiment described above. The difference lies in the hysteresis processing in the microcomputer 9, and this point will be described below with reference to the flowchart of FIG.

First, the temperature data from the thermistor 8 is acquired (step 1), the current LEVEL of the emphasis conversion parameter corresponding to the acquired temperature data is determined (step 2), and the determined current LEVEL and The enhancement conversion parameter currently selected is compared with the confirmed LEVEL (step 3). If both are the same, the counter values of both the up counter and the down counter are cleared (step 4) and the process returns to step 1.

If LEVEL is currently higher than the fixed LEVEL, the counter value of the up counter is incremented by 1 and the counter value of the down counter is cleared (step 5), and the counter value of the up counter reaches 5. It is determined whether or not (step 6), and when the counter value of the up counter has not reached 5, the process returns to step 1. When the counter value of the up counter reaches 5,
The confirmed LEVEL is increased by 1, and the process returns to step 1 (step 7).

On the other hand, in step 4, the current LEVE
If it is determined that L has fallen below the fixed LEVEL,
The counter value of the down counter is incremented by 1, and the counter value of the up counter is cleared (step 8),
It is determined whether or not the counter value of the down counter has reached 5 (step 9), and when the counter value of the down counter has not reached 5, the process returns to step 1. When the count value of the down counter reaches 5, the definite LEVEL is decremented by 1 and the process returns to step 1 (step 7).

As described above, in this embodiment, the temperature threshold value is fixed, the fluctuation of LEVEL is monitored, and when it is determined that LEVEL has completely changed, a new LE is newly added.
By shifting to VEL, since the detected temperature has a hysteresis, even when the detected temperature repeatedly rises and falls near the temperature threshold value, the enhancement conversion parameters (LEVEL 0 to LEVEL 2 are accompanied by this). ) Does not fluctuate drastically, and a stable emphasis conversion parameter (LEV
It becomes possible to realize the switching control of EL 0 to LEVEL 2), and it is possible to improve the image quality of the display image.

In the above-described embodiment of the present invention, the thermistor 8 is used as the means for detecting the temperature inside the apparatus, but the present invention is not limited to this, and is usually provided in a power supply for driving the liquid crystal panel 5. A method of sharing a detection signal output from the temperature detector, a method of detecting a driving voltage of a light source provided in the vicinity of the liquid crystal panel 5, and using this as an indirect temperature detection signal are conceivable.

It is desirable that the temperature detecting means directly measure the temperature of the liquid crystal panel 5 surface, but since this is difficult in practice, the temperature is measured on the driving substrate and an error from the temperature of the liquid crystal panel 5 surface is measured. Need to be corrected. That is, temperature correlation data between the surface of the liquid crystal panel 5 and the thermistor portion on the drive substrate is acquired in advance, and the measured temperature on the drive substrate is corrected based on this temperature correlation data.

Here, since there is a difference in the temperature rising curve between the driving substrate and the surface of the liquid crystal panel 5 after the power is turned on until the temperature inside the device is saturated, there is a difference in the temperature rise with the lapse of time after the power is turned on. Data indicating the difference between the curves is stored in the microcomputer 9, the timer built in the microcomputer 9 is used to count the elapsed time after the power is turned on, and the error to be corrected in accordance with the elapsed time. The temperature is variably controlled.

Further, in the above-described embodiment of the present invention, three ROMs 1a to 1c corresponding to LEVEL 0 to LEVEL 2 are provided as means for switching the emphasis conversion parameter according to the temperature inside the apparatus, and these are switched and selected. As described above, for example, as shown in FIG. 6, addresses corresponding to LEVEL 0 to LEVEL 2 are allocated in a single ROM 1 and the microcomputer 9
The address to be referred to may be variably controlled based on the parameter control signal from.

The emphasis conversion parameter read from the ROM 1 may not be changed, and the arithmetic unit 3 may perform an operation for changing the emphasis conversion parameter. in this case,
For example, a configuration is provided in which the coefficient k (0 <k <1) is added to the emphasis conversion parameter read from the ROM 1, and the value of the coefficient k can be variably controlled based on the parameter control signal.

Further, in the above embodiment of the present invention,
Enhanced conversion parameter (LE
VEL) is set to three levels, but needless to say, it is not limited to this. Furthermore, it is obvious that the hysteresis processing of the first embodiment and the hysteresis processing of the second embodiment may be combined to more reliably determine / control the LEVEL switching.

Further, in the above-described embodiment of the present invention, the image data of one field before and the image data of the current field are compared, and the enhancement conversion parameter obtained from the comparison result is used to improve the response speed of the liquid crystal panel. However, it goes without saying that the enhancement conversion parameter may be obtained by using the image data of two fields before and three fields before, for example.

[0041]

Since the liquid crystal display device of the present invention is configured as described above, even if the detected temperature in the device is unstable, the emphasis conversion parameter is stably variably controlled and displayed. It is possible to improve the image quality of the image.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a main part in a first embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a schematic explanatory view showing an example of table contents of a ROM in the first embodiment of the liquid crystal display device of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a detected temperature and an emphasis conversion parameter level in the first embodiment of the liquid crystal display device of the present invention.

FIG. 4 is a flowchart showing a hysteresis process in the first embodiment of the liquid crystal display device of the present invention.

FIG. 5 is a flowchart showing a hysteresis process in the second embodiment of the liquid crystal display device of the present invention.

FIG. 6 shows an RO in the embodiment of the liquid crystal display device of the present invention.
It is a schematic explanatory drawing which shows the other example of the table content of M.

[Explanation of symbols]

1 ROM 2 frame memory 3 calculator 4 LCD controller 5 LCD panel 6 gate driver 7 Source driver 8 thermistor 9 Microcomputer

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI G09G 3/20 641 G09G 3/20 641P 642 642C 642P 3/36 3/36 H04N 5/66 102 H04N 5/66 102Z (56) Reference: JP-A-3-98085 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G09G 3/00-3/38 G02F 1/133 H04N 5/66-5/74

Claims (7)

(57) [Claims] 1. Displaying an image using a liquid crystal display panel
A liquid crystal display device , comprising temperature detecting means for detecting the temperature inside the device, and hysteresis for the temperature detected by the temperature detecting means.
Control means for generating a control signal by performing processing
And the control signal generated by the control means and the input image data.
The combination of gradation transition before and after one vertical period
Using the enhancement conversion parameter determined according to
To perform emphasis conversion on input image data in the immediate period
The strength of compensating the optical response characteristics of the liquid crystal display panel.
And a writing gradation determining means for obtaining the tone conversion data
Liquid crystal display device characterized by. 2. The liquid crystal display device according to claim 1.
The write gradation determining means is one vertical of the input image data.
Depending on the combination of gradation transitions before and after the period,
The input image data is used to determine the optical response characteristics of the liquid crystal display panel.
Pre-defined for conversion into enhanced conversion data for compensation
Different emphasis conversion parameters are recorded for each temperature range.
Based on the plurality of stored table memories and the control signal generated by the control means,
Selectively switching one of multiple table memories
And a table memory switched by the switching unit.
Using the enhanced transformation parameters read by
To obtain the enhanced conversion data for the input image data.
Therefore, write grayscale data is supplied to the liquid crystal display panel.
A liquid crystal display device characterized by the following. 3. The liquid crystal display device according to claim 1.
The write gradation determining means is one vertical of the input image data.
Depending on the combination of gradation transitions before and after the period,
The input image data is used to determine the optical response characteristics of the liquid crystal display panel.
Pre-defined for conversion into enhanced conversion data for compensation
Different emphasis conversion parameters for different temperature ranges
Based on a table memory stored for each number of reference table areas and a control signal generated by the control means.
Selectively switch one of multiple reference table areas
A switching unit for switching the table memory, which is switched by the switching unit.
Enhancement read by referring to the illumination table area
Using the conversion parameters, for the input image data
The enhanced conversion data is obtained, and the liquid crystal is used as the writing gradation data.
A liquid crystal display device characterized by being supplied to a display panel. 4. The liquid crystal display according to claim 2 or 3.
In the device, the table memory is a representative floor in display data gradation.
Emphasis conversion parameters for key transition patterns are stored
A liquid crystal display device characterized by being provided. 5. The method according to any one of claims 1 to 4.
In the liquid crystal display device, the control means controls the temperature detected by the temperature detection means and the location.
Compared with a fixed threshold temperature, and rises above the specified threshold temperature
Or, the detected temperature that has dropped is continuously acquired more than the specified number of times.
In case of the above, the enhanced conversion parameter corresponding to the detected temperature
It is characterized by outputting a control signal for switching and selecting
Liquid crystal display device. 6. The method according to any one of claims 1 to 5.
In the liquid crystal display device, the control means controls the temperature detected by the temperature detection means.
Then, the error with the temperature of the liquid crystal display panel surface is corrected.
A liquid crystal display device characterized by the above. 7. The liquid crystal display device according to claim 6,
In addition, the control means, according to the elapsed time after the power is turned on,
Liquid characterized by variably controlling the error temperature to be corrected
Crystal display device.