JP2004240273A - Liquid crystal display device and service providing system - Google Patents

Abstract

[PROBLEMS] To display desired gradation luminance by ensuring that a liquid crystal reaches a transmittance (target gradation luminance) determined by an input image signal after one vertical display period has elapsed in any use environment. Provided is a liquid crystal display device capable of performing the following.
A temperature sensor for detecting a temperature in the device, and a sensor for causing a liquid crystal display panel to respond to a transmittance determined by an input image signal after one vertical display period has elapsed at the detected temperature in the device. A communication control unit 10 for requesting the emphasis conversion parameter to the server 300 via the communication network 200 and obtaining the emphasis conversion parameter from the server 300; and a rewritable OS table for storing the obtained emphasis conversion parameter The image processing apparatus includes a memory 11 and an emphasis conversion unit 3 that performs an emphasis conversion process for compensating an optical response characteristic of the liquid crystal display panel 5 on an input image signal using the stored emphasis conversion parameters.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device that displays an image using a liquid crystal display panel, and more particularly to a liquid crystal display device and a service providing system capable of improving the optical response characteristics of the liquid crystal display panel.
[0002]
[Prior art]
In recent years, lighter and thinner display devices have been required to reduce the weight and thickness of personal computers and television receivers. In response to such demands, liquid crystal displays (LCDs) have been used instead of cathode ray tubes (CRTs). ) Has been developed.
[0003]
An LCD applies a desired electric field to a liquid crystal layer having an anisotropic dielectric constant injected between two substrates, and controls the intensity of the electric field to control the amount of light transmitted through the substrates to achieve a desired level. This is a display device for obtaining an image signal. Such LCDs are typical of portable simple flat panel displays. Among them, TFT LCDs using thin film transistors (TFTs) as switching elements are mainly used.
[0004]
Recently, LCDs are widely used not only as display devices for computers but also as display devices for television receivers, so that the need to implement moving images has increased. However, the conventional LCD has a shortcoming that it is difficult to realize a moving image due to a low response speed.
[0005]
In order to improve such a problem of the response speed of the liquid crystal, a predetermined gradation voltage for the input image signal of the current frame is determined according to a combination of the input image signal of the previous frame and the input image signal of the current frame. A liquid crystal driving method for supplying a high (overshoot) driving voltage or a lower (undershoot) driving voltage to a liquid crystal display panel is known (Japanese Patent Laid-Open No. 4-365094). Hereinafter, in this specification, this driving method is defined as overshoot (OS) driving.
[0006]
Also, it is known that the response speed of liquid crystal has a very large temperature dependence, so that even if the temperature of the liquid crystal display panel changes, the response speed of gradation change is always maintained without deteriorating the display quality. A liquid crystal panel driving device for controlling the liquid crystal panel in an optimal state is described in, for example, Japanese Patent Application Laid-Open No. 4-318516.
[0007]
A method of performing overshoot driving to compensate for the optical response characteristics of the liquid crystal display panel in accordance with the use environment temperature will be described with reference to FIGS. Here, FIG. 5 is a functional block diagram showing a configuration of a main part of a conventional liquid crystal display device, FIG. 6 is an explanatory diagram showing an example of contents of an OS table memory, and FIG. 7 shows a relationship between a device internal temperature and an emphasis conversion parameter. FIG. 8 is an explanatory diagram showing the relationship between the voltage applied to the liquid crystal and the response of the liquid crystal.
[0008]
In FIG. 5, reference numerals 1a to 1c denote OS table memories (ROM) storing applied voltage data (emphasis conversion parameters) corresponding to gradation transitions before and after one frame period of the input image signal for each temperature in the apparatus. Is the frame memory (FM), 3 is the input image data (Current Data) of the Mth frame to be displayed, and the input image data (Previous Data) of the (M-1) th frame stored in the frame memory 2 is compared. Then, an enhancement conversion parameter corresponding to the comparison result (gradation transition) is read out from any of the OS table memories (ROM) 1a to 1c, and the enhancement required for image display of the Mth frame is performed based on the enhancement conversion parameter. This is an enhancement conversion unit that determines a conversion signal.
[0009]
Reference numeral 4 denotes a liquid crystal controller that outputs a liquid crystal driving signal to the gate driver 6 and the source driver 7 of the liquid crystal display panel 5 based on the emphasized conversion signal from the emphasis conversion unit 3. The temperature sensor 9 selects one of the OS table memories (ROM) 1a to 1c according to the internal temperature detected by the temperature sensor 8, and converts the control signal for switching the enhancement conversion parameter into an enhancement conversion unit. 3 is a control CPU that outputs the data to the control CPU 3.
[0010]
Here, the emphasis conversion parameters LEVEL1, LEVEL2, and LEVEL3 stored in the OS table memories (ROM) 1a to 1c are respectively stored in the environment of the reference temperatures T1, T2, and T3 (T1 <T2 <T3). It is obtained in advance from the actual measurement value of the optical response characteristic of the liquid crystal display panel 5, and the respective degree of enhancement conversion has a relationship of LEVEL1>LEVEL2> LEVEL3.
[0011]
For example, when the number of display signal levels, that is, the number of display data is 256 gradations of 8 bits, even if the OS table memory (ROM) has enhancement conversion parameters (measured values) for all 256 gradations. For example, as shown in FIG. 6, for example, as shown in FIG. 6, only the emphasis conversion parameters (measured values) for nine representative tones for every 32 gradations are stored, and the emphasis conversion signals for the other gradations are stored in the measured values. , The storage capacity of the OS table memory (ROM) can be reduced.
[0012]
Next, the operation of the conventional liquid crystal display device will be described. If the internal temperature T detected by the temperature sensor 8 is equal to or lower than the threshold temperature Th1 (= (T1 + T2) / 2), the control CPU 9 instructs the emphasis conversion unit 3 to select and refer to the OS table memory (ROM) 1a. (See FIG. 7). As a result, the emphasis conversion unit 3 performs an emphasis conversion process on the input image signal using the emphasis conversion parameter LEVEL 1 stored in the OS table memory (ROM) 1a.
[0013]
If the temperature T in the apparatus detected by the temperature sensor 8 is higher than the threshold temperature Th1 and equal to or lower than the threshold temperature Th2 (= (T2 + T3) / 2), the control CPU 9 sends an OS table memory ( (ROM) 1b is instructed to be referred to (see FIG. 7). As a result, the emphasis conversion unit 3 performs an emphasis conversion process on the input image signal using the emphasis conversion parameter LEVEL 2 stored in the OS table memory (ROM) 1b.
[0014]
Further, if the internal temperature T detected by the temperature sensor 8 is higher than the threshold temperature Th2, the control CPU 9 instructs the emphasis conversion unit 3 to select and refer to the OS table memory (ROM) 1c (FIG. 7). As a result, the emphasis conversion unit 3 performs an emphasis conversion process on the input image signal using the emphasis conversion parameter LEVEL 3 stored in the OS table memory (ROM) 1c.
[0015]
In general, in a liquid crystal display panel, the time required to change from one halftone to another halftone is long, and the ability to follow an input signal at a low temperature becomes extremely poor, and the response time increases. There is a problem that it is not possible to display within a frame period (for example, 16.7 msec in the case of a progressive scan of 60 Hz), and not only an afterimage is generated but also a halftone cannot be displayed correctly. By using the overshoot drive circuit, it is possible to display the target halftone in a short time (within one frame period) as shown by the solid line in FIG.
[0016]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 4-365094 [Patent Document 2]
JP-A-4-318516
[Problems to be solved by the invention]
In the above-described conventional liquid crystal display device, it is determined which of the OS table memories (ROM) 1a to 1c is to be referred to for each temperature range divided by the threshold temperatures Th1 and Th2, and the enhancement conversion parameters LEVEL 1 to LEVEL are determined. 3, the input image signal is subjected to the enhancement conversion. The enhancement conversion parameters LEVEL1 to LEVEL3 are determined by the liquid crystal display panel 5 at the reference temperatures T1 to T3 after the lapse of one frame period. This is an actually measured value of applied voltage data that can respond to the transmittance determined by the signal.
[0018]
Therefore, when the temperature T in the apparatus is largely different from the reference temperatures T1 to T3, for example, when the temperature T in the apparatus is near the threshold temperatures Th1 and Th2, the emphasis conversion is performed with reference to any of the OS table memories (ROM) 1a to 1c. Even if this happens, the liquid crystal display panel 5 cannot accurately respond to the transmittance determined by the input image signal after the lapse of one frame period, and reaches the target gradation luminance as shown by the broken line in FIG. In other words, there is a problem that the image is not displayed correctly or the response is higher than the target gradation luminance, and a correct image cannot be displayed.
[0019]
Also, it is assumed that the liquid crystal display panel 5 has reached the transmittance (target gradation luminance) determined by the image signal of the current frame despite the occurrence of an error in the actual arrival gradation luminance. If the image signal of the next frame is subjected to the emphasis conversion processing, the liquid crystal display panel 5 does not reach the transmittance defined by the image signal of the next frame or responds excessively, so that not only the correct image display cannot be performed. However, there is a problem that the error gradually increases and the pixel gradually becomes black or white.
[0020]
Incidentally, it is possible to suppress the occurrence of the liquid crystal response error by increasing the number of samples of the reference temperature Tn for actually measuring the emphasis conversion parameters and increasing the number of emphasis conversion parameters corresponding to the device internal temperature. However, in this case, as many OS table memories (ROMs) as the number of emphasis conversion parameters are required, so that an increase in cost due to an increase in resources is inevitable, and the feasibility is limited.
[0021]
The present invention has been made in view of the above problems, and ensures that the liquid crystal reaches a transmittance (target gradation luminance) determined by an input image signal after one vertical display period has elapsed in any use environment. Accordingly, a liquid crystal display device capable of displaying a desired gradation luminance is provided.
[0022]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a temperature detecting means for detecting a temperature in the device, wherein the liquid crystal display panel responds to a transmittance determined by an input image signal after one vertical display period has elapsed at the detected temperature in the device. Enhancement conversion parameter requesting means for requesting an enhancement conversion parameter for an external device, enhancement enhancement parameter acquisition means for acquiring the enhancement conversion parameter from an external device, and a rewritable memory for storing the acquired enhancement conversion parameter. And an emphasis conversion means for performing an emphasis conversion process for compensating the optical response characteristics of the liquid crystal display panel on the input image signal using the stored emphasis conversion parameters.
[0023]
The second invention of the present application is characterized in that the emphasis conversion parameter requesting means requests the external device for the emphasis conversion parameter by adding device identification information for identifying the device.
[0024]
A third invention of the present application is characterized in that the external device is a server device connected via a communication network.
[0025]
According to a fourth aspect of the present invention, the memory means is a table memory for storing an enhancement conversion parameter specified from an image signal in a current vertical display period and an image signal one vertical display period ago.
[0026]
The fifth invention of the present application is connected to a communication network, and holds an enhancement conversion parameter for causing the liquid crystal display panel to respond to a transmittance determined by an input image signal after a lapse of one vertical display period, corresponding to a plurality of temperatures. A server device, and a service providing system including a liquid crystal display device having a function of connecting to the communication network, wherein the liquid crystal display device detects a temperature in the device, Enhancement conversion parameter requesting means for requesting the server device for an enhancement conversion parameter for causing the liquid crystal display panel to respond to the transmittance determined by the input image signal after the elapse of one vertical display period at the detected device temperature. An enhancement conversion parameter acquisition unit that acquires the enhancement conversion parameter from the server device; Rewritable memory means for storing parameters, and emphasis conversion means for performing an emphasis conversion process for compensating an optical response characteristic of a liquid crystal display panel on an input image signal using the stored emphasis conversion parameters. It is characterized by.
[0027]
According to the liquid crystal display device of the present invention, an optimal enhancement conversion parameter corresponding to the temperature in the device is obtained from an external device, and the obtained enhancement conversion parameter is used to input a signal of the liquid crystal display panel to the input image signal. The enhancement conversion process for compensating the optical response characteristics can be performed, so that the liquid crystal display panel can reliably transmit the input image signal after one vertical display period (target gradation luminance) in any use environment. , And a high-quality image display can be realized.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 4. The same reference numerals are given to the same portions as those in the above-described conventional example, and the description thereof will be omitted. Here, FIG. 1 is a functional block diagram showing a schematic configuration in a service providing system of the present embodiment, FIG. 2 is a schematic explanatory diagram showing an example of information storage in a server device of the present embodiment, and FIG. 3 is a liquid crystal display of the present embodiment. FIG. 4 is a flowchart showing the operation of the control CPU in the device, and FIG. 4 is a flowchart showing the operation in the server device of the present embodiment.
[0029]
As shown in FIG. 1, the service providing system according to the present embodiment includes a liquid crystal display device 100 having a function of connecting to a communication network 200, and a service operating company (for example, a manufacturer of the liquid crystal display device 100) that exists on the communication network 200. , Etc.) operated by the server 300. Here, a description will be given of a communication network 200 that uses, for example, the Internet that is widely open to the general public. However, it is needless to say that the communication network 200 is not limited to this.
[0030]
In the server 300, after one vertical display period has elapsed, an emphasis conversion parameter for causing the liquid crystal display panel 5 of each liquid crystal display device 100 to respond to the transmittance determined by the input image signal is accumulated corresponding to a plurality of temperature conditions. ing. The optical response characteristics of the liquid crystal display panel 5 differ depending on the alignment mode of the liquid crystal, the electrode structure for applying an electric field to the liquid crystal material, and the like. Therefore, as shown in FIG. 2, here, a plurality of enhancement conversion parameters corresponding to each temperature condition are stored in a hierarchical structure for each product type of the liquid crystal display device 100.
[0031]
The enhancement conversion parameters stored in the server 300 are obtained from the actually measured values of the optical response characteristics of the liquid crystal display panel 5 used in each of the products (liquid crystal display devices) A to Z, and are about one vertical display period. Is data determined according to the combination of gradation transitions in the image signal of FIG. For example, when the number of display signal levels, that is, the number of display data items is 256 gradations of 8 bits, enhancement conversion parameters (actual measurement values) for all 256 × 256 gradation transitions may be held, or, for example, 9 × 9. Only the emphasis conversion parameters (actually measured values) for the transition pattern for the representative gray scale may be held.
[0032]
Further, the liquid crystal display device 100 includes an OS table memory (EEPROM) 11 that rewritably stores an emphasis conversion parameter referred to by the emphasis conversion unit 3, and device identification information that stores device identification information for identifying the device. The storage unit 20, a communication control unit (modem) 30 for communicating with the server 300 on the communication network 200, and an emphasis conversion parameter corresponding to the device temperature detected by the temperature sensor 8 are acquired from the server 300. The control CPU 40 controls the communication control unit 30 as described above, and updates and stores the acquired enhancement conversion parameter in the OS table memory (EEPROM) 11.
[0033]
Here, the rewritable non-volatile OS table memory (EEPROM) 11 is, like the one shown in FIG. 6, an emphasis conversion designated from the image signal of the current vertical display period and the image signal of one previous vertical display period. It is a two-dimensional table memory for storing parameters. The temperature sensor 8 is desirably provided so as to be able to detect the temperature of the liquid crystal display panel 5 itself as much as possible, and may be configured such that not only one but also a plurality of them are provided at different panel plane positions. .
[0034]
Further, as the device identification information stored in the device identification information storage unit 20, an ID assigned to each product is used here, but it is possible to specify the liquid crystal display panel 5 used in the device. Anything is fine. Further, in the control CPU 40, the URL address of the server 300 that provides the service of providing the emphasized conversion parameter is held in advance, and it is possible to access the server 300 on the Internet based on the URL address. Has become.
[0035]
Next, the operation of the present embodiment configured as described above will be described. First, as shown in the flowchart of FIG. 3, the liquid crystal display device 100 acquires the current internal device temperature data T from the temperature sensor 8 (step 1), and compares it with the previously acquired internal device temperature data (step 1). Step 2) If there is no change from the previously obtained data, the process returns to step 1. If there is a change from the previously obtained data, the connection to the communication network 200 is executed (step 3), and after adding the current in-apparatus temperature data T to the apparatus identification information, the corresponding enhancement conversion parameter is transmitted. Request to server 300 (step 4).
[0036]
When the emphasis conversion parameter corresponding to the current temperature of the device is received (downloaded) from the server 300 via the communication network 200 (step 5), the parameter is rewritten and stored in the OS table memory (EEPROM) 11 (step 6). ), Disconnect the connection to the communication network 200 (step 7), and return to step 1. Steps 3 and 7 are unnecessary in an environment where the connection to the communication network 200 is always possible.
[0037]
The emphasis conversion unit 3 performs an emphasis conversion process on the input image signal using the emphasis conversion parameters stored in the OS table memory (EEPROM) 11 so that the liquid crystal display panel 5 can display the input image signal after one frame period. And outputs an enhanced conversion signal (applied voltage data) capable of responding to the transmittance determined by
[0038]
On the other hand, as shown in the flowchart of FIG. 4, the server 300 on the communication network 200 determines whether or not there is a transmission request for the enhancement conversion parameter from the liquid crystal display device 100 (step 11), and receives the transmission request for the enhancement conversion parameter. Then, the emphasis conversion parameter corresponding to the requesting device identification information and the in-device temperature data T is transmitted to the requesting liquid crystal display device 100 (step 12), and the process returns to step 11.
[0039]
As described above, the liquid crystal display device 100 of the present embodiment can always externally acquire the optimum enhancement conversion parameter corresponding to the temperature inside the device regardless of the viewing environment such as the place of use or the time zone. Using the optimal enhancement conversion parameter obtained from the outside, it is possible to reliably cause the liquid crystal display panel 5 to respond to the transmittance (target gradation luminance) determined by the input image signal after the elapse of one vertical display period. In other words, it is possible to prevent the occurrence of a liquid crystal response error due to a mismatch between the reference temperature and the internal temperature in an environment where the enhancement conversion parameter is actually measured, and to realize high-quality image display.
[0040]
Further, with the service providing system of the present embodiment, it is possible to always supply an optimum emphasis conversion parameter regardless of the use environment of the liquid crystal display device 100 and realize a high quality image display. Further, in the liquid crystal display device 100, it is not necessary to have in advance enhancement conversion parameters corresponding to a plurality of device temperatures, and it is possible to prevent an increase in resources.
[0041]
In the above-described embodiment, the emphasis conversion process is always performed with reference to the OS table memory (EEPROM) 11 after power-on, but the rewritable nonvolatile OS table memory (EEPROM) 11 is used. In addition, a read-only OS table memory (e.g., a read-only OS table memory that stores an emphasis conversion parameter corresponding to a predetermined reference temperature, which is referred to when connection to the communication network 200 is not possible or when power is turned on, etc. ROM) may be provided.
[0042]
In the above embodiment, the OS table memory (EEPROM) 11 for storing the enhancement conversion parameter (applied voltage data) addressed from the image signal of the current frame and the image signal of the previous frame in a two-dimensional matrix is provided. A description has been given of a case where the enhancement conversion processing is performed on the image signal of the current frame by using the enhancement conversion parameter. However, the enhancement conversion parameter (applied voltage data) which is uniquely determined from the gradation level of the image signal of the current frame is described. ) May be used as a one-dimensional table memory.
[0043]
Further, a two-dimensional function f (pre, cur) corresponding to the temperature in the apparatus, which uses, for example, the grayscale before the transition and the grayscale after the transition as variables, as an enhancement conversion parameter, is obtained from the outside as appropriate. A configuration may be used in which an input image signal is subjected to an emphasis conversion process for compensating for the optical response characteristics of the liquid crystal display panel.
[0044]
Further, in the above embodiment, by adding hysteresis to the temperature inside the device detected by the temperature sensor 8 and controlling the request / acquisition of the emphasis conversion parameter, the detected temperature inside the device is unstable. However, it is possible to stably update the emphasis conversion parameters without frequently changing the emphasis conversion parameters, thereby improving the image quality of the display image.
[0045]
【The invention's effect】
Since the liquid crystal display device of the present invention is configured as described above, an optimal enhancement conversion parameter corresponding to the temperature inside the device is obtained from an external device, and the input image signal is obtained by using the obtained enhancement conversion parameter. However, since the enhancement conversion processing for compensating the optical response characteristics of the liquid crystal display panel can be performed, the liquid crystal display panel can reliably transmit the input image signal after one vertical display period has passed in any use environment. It is possible to make the response reach the ratio (target gradation luminance), and high-quality image display can be realized.
[Brief description of the drawings]
FIG. 1 is a functional block diagram illustrating a schematic configuration of a service providing apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic explanatory diagram showing an example of holding information of a server device according to an embodiment of the present invention.
FIG. 3 is a flowchart illustrating an operation of a control CPU of the liquid crystal display device according to one embodiment of the present invention.
FIG. 4 is a flowchart showing an operation of the server device according to the embodiment of the present invention.
FIG. 5 is a functional block diagram showing a main part configuration in a conventional liquid crystal display device.
FIG. 6 is an explanatory diagram showing an example of the contents of an OS table memory (ROM) in a conventional liquid crystal display device.
FIG. 7 is an explanatory diagram showing the relationship between the internal temperature and the enhancement conversion parameter in a conventional liquid crystal display device.
FIG. 8 is an explanatory diagram showing the relationship between the voltage applied to the liquid crystal and the response of the liquid crystal.
[Explanation of symbols]
2 Frame memory 3 Emphasis converter 4 Liquid crystal controller 5 Liquid crystal display panel 6 Gate driver 7 Source driver 8 Temperature sensor 11 Table memory (EEPROM)
20 device identification information storage unit 30 communication control unit 40 control CPU
100 liquid crystal display device 200 communication network 300 server

Claims (5)

Temperature detection means for detecting the temperature in the device,
Enhancement conversion parameter requesting means for requesting an external device for an enhancement conversion parameter for causing the liquid crystal display panel to respond to the transmittance determined by the input image signal after the elapse of one vertical display period at the detected device temperature. ,
Enhancement conversion parameter acquisition means for acquiring the enhancement conversion parameter from an external device,
Rewritable memory means for storing the acquired enhancement conversion parameter,
A liquid crystal display device comprising: an emphasis conversion unit that performs an emphasis conversion process for compensating an optical response characteristic of a liquid crystal display panel on an input image signal using the stored emphasis conversion parameters. The liquid crystal display device according to claim 1,
The liquid crystal display device, wherein the emphasis conversion parameter requesting unit adds device identification information for identifying the device and requests the emphasis conversion parameter from an external device. The liquid crystal display device according to claim 1, wherein
The liquid crystal display device, wherein the external device is a server device connected via a communication network. The liquid crystal display device according to any one of claims 1 to 3,
2. The liquid crystal display device according to claim 1, wherein said memory means is a table memory for storing an emphasis conversion parameter designated from an image signal of a current vertical display period and an image signal of one vertical display period before. A server device connected to the communication network and holding an enhancement conversion parameter for causing the liquid crystal display panel to respond to the transmittance determined by the input image signal after a lapse of one vertical display period for each of a plurality of temperatures;
A service providing system including a liquid crystal display device having a function of connecting to the communication network,
The liquid crystal display device, a temperature detecting means for detecting the temperature in the device,
Enhancement conversion parameter requesting means for requesting, from the server device, an enhancement conversion parameter for causing the liquid crystal display panel to respond to a transmittance determined by an input image signal after the elapse of one vertical display period at the detected device internal temperature. When,
Enhancement conversion parameter acquisition means for acquiring the enhancement conversion parameter from the server device;
Rewritable memory means for storing the acquired enhancement conversion parameter,
A service providing system comprising: an emphasis conversion unit that performs an emphasis conversion process for compensating an optical response characteristic of a liquid crystal display panel on an input image signal using the stored emphasis conversion parameter.

Images