Image display system and image display device

The present invention provides a technique for supplying appropriate image quality to a user. Upon executing an application, a PC1 outputs an automatic adjustment start signal s1 which is information relating to image quality required for the application, and on the basis of the automatic adjustment start signal s1, a display device 4 adjusts the image quality. Thus, it is possible to display an image with image quality suitable for each of the applications without causing any time-consuming manual operations by the user. Consequently, it is possible to provide appropriate image quality to the user.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image display system for displaying an image on the basis of an image signal sent from a computer, and an image display device.

2. Description of the Background Art

FIG. 8is a block diagram showing a configuration of a conventional image display system. As shown inFIG. 8, the conventional image display system is provided with a computer system100and a display device110connected to the computer system100. The display device110has a preamplifier120, an analog/digital converter (hereinafter, referred to as “A/D converter”)130, a microcomputer140, a PLL (Phase Locked Loop) unit150, a graphic controller160and a liquid crystal display panel170.

The computer system100outputs an analog image signal composed of color signals of red (R), green (G) and blue (B) to the preamplifier120, and outputs a horizontal synchronous signal H and a vertical synchronous signal V to the microcomputer140. The preamplifier120adjusts the signal level of the received analog image signal on the basis of control of the microcomputer140, and outputs the analog image signal having the adjusted signal level to the A/D converter130. Hereinafter, the analog image signal to be inputted to the preamplifier120is referred to as “input analog image signal” and the analog image signal to be outputted from the preamplifier120is referred to as “output analog image signal”.

The A/D converter130converts the received output analog image signal to a digital image signal on the basis of a sampling clock outputted from the PLL unit150, and outputs the resulting signal to the graphic controller160. Further, the microcomputer140detects and separates the horizontal synchronous signal H and vertical synchronous signal V outputted from the computer system100, identifies the operation mode on the basis of the frequencies of the separated horizontal synchronous signal H and vertical synchronous signal V, and recognizes the resolution which corresponds to the operation mode. Moreover, the separated horizontal synchronous signal H and vertical synchronous signal V are outputted to the PLL unit150and the graphic controller160.

The PLL unit150variably changes the sampling clock in accordance with the resolution recognized by the microcomputer140, and outputs the resulting sampling clock to the A/D converter130. The graphic controller160adjusts the frequency of the digital image signal outputted from the A/D converter130in accordance with the resolution recognized by the microcomputer140, and displays an image on the liquid crystal display panel170.

Then, an adjusting process of the signal level of an input analog image signal that is carried out in the preamplifier120will be described in detail. In the above-described conventional image display system, in order to appropriately carry out the gradation-display of an image, it is necessary to carry out a gradation adjustment of making the signal level of the output analog image signal coincident with the analog input range of the A/D converter130. This gradation adjustment is carried out in the preamplifier120. Here, the “analog input range” means a range of the analog signal level for which the A/D converter130can output a digital signal in accordance with the signal level of the analog signal when the A/D converter130converts an analog signal to a digital signal. Therefore, analog signals exceeding this range are outputted from the A/D converter130as digital data having a constant value regardless of the signal level.

More specifically, on the basis of the control of the microcomputer140, the preamplifier120amplifies the amplitude of the input analog image signal. By varying the value of the minimum level (hereinafter, referred to as “bias value”) of the input analog image signal with respect to a reference voltage, e.g., 0V, the signal level of the output analog image signal is made coincident with the analog input range of the A/D converter130. In other words, on the basis of the control of the microcomputer140, the preamplifier120adjusts the amplification rate (hereinafter, referred to as “gain value”) and the bias value of the input analog image signal. The microcomputer140stores a program (hereinafter, referred to as “program for adjustment”) used for adjusting the gain value and bias value of the input analog image signal. This program is executed by the microcomputer140so that the gain value and bias value of the input analog video signal are set.

Next, a setting method of the gain value and bias value of the input analog image signal in a conventional image display system will be described in more detail.FIG. 9is a flow chart showing the setting method of the gain value and bias value of the input analog image signal in the conventional image display system. As shown inFIG. 9, at step ST100, the gain value and the bias value are initialized.

Next, at step ST110, a base address register is set, which is used for reading data of the digital image signal (hereinafter, referred to as “stable area data”) corresponding to a stable area of the black area in the input analog image signal which is inputted so as to adjust the bias value. Then, at step ST120, a judgment is made as to whether or not the value of the stable area data read out through the base address register thus set is greater than the minimum value “00” of the digital output range of the A/D converter130. Here, the “stable area” means an area which is not subjected to influences from a ringing phenomenon which tends to generate in edge portions of the input analog image signal, and is specified by a program for adjustment installed in the microcomputer140. Moreover, the stable area data, which is read out through the base address register, is data set on a pixel basis.

As a result of the judgment at step ST120, when the value of the stable area data, which is read out through the base address, is greater than the minimum value of the digital output range of the A/D converter130, the bias value is reduced at step ST130, and at step ST120, the judgment is again made as to whether or not the value of the stable area data read through the base address is greater than the minimum value of the digital output range of the A/D converter130. As a result of the judgment at step ST120, when the value of the stable area data, which is read out through the base address, is equal to the minimum value “00” of the digital output range of the A/D converter130, the adjusting process of the bias value is completed at step ST140.

Upon completion of the adjustment of the bias value, at step ST150, a base address register is set, which is used for reading the stable area data of the white area in the input analog image signal which is inputted so as to adjust the gain value. Then, at step ST160, a judgment is made as to whether or not the value of the stable area data read out through the base address register thus set is smaller than the maximum value “FF” of the digital output range of the A/D converter130.

As a result of the judgment at step ST160, when the value of the stable area data, which is read out through the base address, is smaller than the maximum value of the digital output range of the A/D converter130, the gain value is increased at step ST170, and at step ST160, the judgment is again made as to whether or not the value of the stable area data, which is read through the base address, is smaller than the maximum value of the digital output range of the A/D converter130. As a result of the judgment at step ST160, when the value of the stable area data, which is read out through the base address, is equal to the maximum value of the digital output range of the A/D converter130, the adjusting process of the gain value is completed at step ST180.

As described above, in the conventional image display system, a stable area, which is not subjected to influences from a ringing phenomenon in the input analog image signal, is used so as to set the gain value and bias value of the input analog image signal. Then, a gradation adjusting process, which makes the signal level of the output analog image signal coincident with the analog input range of the A/D converter130, is carried out. Thus, it becomes possible to carry out an appropriate gradation displaying process.

With respect to the conventional image display system as described above, Japanese Patent Application Laid-Open No. 2001-13931 discloses substantially the same arrangement.

However, in the above-described conventional image display system, since the stable area varies depending on the computer system100to be connected to the display device110, the stable area specified by the program installed in the microcomputer140sometimes corresponds to an area which is subjected to influences from a ringing phenomenon. In such a case, the stable area data, which is read out through the base address register, is also subjected to influences from a ringing phenomenon. In addition, the stable area data, which is read out through the base address register, is set on a pixel basis, so that processes at steps ST120to ST140or steps ST160to ST180are executed on a pixel basis. In other words, the gradation adjusting process is carried out by using stable area data corresponding to only one pixel. Therefore, depending on the computer system100to be connected to the display device110, the gain value and bias value of the input analog image signal are set by using only the stable area data which has been subjected to influences from a ringing phenomenon, resulting in a failure to carry out an appropriate gradation displaying process in some cases. This makes it impossible to provide appropriate image quality to the user.

Moreover, in order to provide appropriate image quality to the user, with respect to adjustments of image quality, not only a gradation adjustment of making the signal level of the output analog image signal coincident with the analog input range of the A/D converter130, but also adjustments on luminance and γ-characteristic need to be carried out.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a technique for supplying appropriate image quality to a user.

According to a first aspect of the present invention, an image display system includes a computer which executes application software and which outputs an image signal corresponding to the application software, and an image display device which displays an image on the basis of the image signal. Upon executing the application software, the computer outputs information relating to image quality required for the application software to the image display device. The image display device adjusts image quality on the basis of the information.

According to a second aspect of the present invention, an image display device is connected to a computer which executes application software and which outputs an image signal corresponding to the application software, and can display an image on the basis of the image signal. When the computer executes the application software, the image display device receives information relating to image quality required for the application software that is outputted from the computer, and adjusts image quality on the basis of the information.

When the image display device receives the information relating to image quality required for an application that is outputted from the computer upon executing the application, the display device adjusts image quality on the basis of the information. Thus, it is possible to display an image with image quality which is suitable for the corresponding application without causing any time-consuming, complex tasks to be carried out by the user. Consequently, it becomes possible to supply appropriate image quality to the user.

According to a third aspect of the present invention, an image display system includes a computer which outputs an analog image signal, and an image display device which displays an image on the basis of the analog image signal. The image display device has an analog/digital converter which converts the analog image signal to a digital image signal, a display unit which displays an image on the basis of the digital image signal, and a controller which carries out a gradation adjustment of making a signal level of the analog image signal and an analog input range in the analog/digital converter coincident with each other. The computer outputs the analog image signal which allows the display unit to display a predetermined pattern for use in the gradation adjustment in preset timing over a plurality of pixels, and also outputs information for instructing the start of the gradation adjustment to the controller. Upon receipt of the information, the controller makes a comparison between all the data of the digital image signal corresponding to the predetermined pattern and a value corresponding to a digital output range in the analog/digital converter, and carries out the gradation adjustment on the basis of the results of the comparison.

According to a fourth aspect of the present invention, an image display device is connected to a computer which outputs an analog image signal, and can display an image on the basis of the analog image signal. The image display device includes an analog/digital converter which converts the analog image signal to a digital image signal, a display unit which displays an image on the basis of the digital image signal, and a controller which carries out a gradation adjustment of making a signal level of the analog image signal and an analog input range in the analog/digital converter coincident with each other. The controller receives the analog image signal which allows the display unit to display a predetermined pattern for use in the gradation adjustment over a plurality of pixels in addition to information for instructing the start of the gradation adjustment that is outputted from the computer in preset timing, and makes a comparison between all the data of the digital image signal corresponding to the predetermined pattern and a value corresponding to a digital output range in the analog/digital converter, and carries out the gradation adjustment on the basis of the results of the comparison.

The controller receives information for instructing the start of the gradation adjustment that is outputted from the computer in preset timing, and carries out a gradation adjustment of making a signal level of the analog image signal and an analog input range in the analog/digital converter coincident with each other. Therefore, it is possible to carry out an appropriate gradation displaying process without requiring any specific attention of the user, in other words, without requiring any time-consuming, complex manual operations by the user. Consequently, it is possible to supply appropriate image quality to the user without requiring any time-consuming, complex manual operations by the user.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 1is a block diagram showing a configuration of an image display system according to a first embodiment of the present invention, and this also serves as a block diagram showing a configuration of an image display system according to a second embodiment, which will be described later. As shown inFIG. 1, the image display system according to the first embodiment is provided with: a personal computer (hereinafter, referred to as “PC”)1which executes a plurality of pieces of application software (hereinafter, simply referred to as “application”) and outputs analog image signals d1R, d1G and d1B that correspond to the respective applications; and an image display device4(hereinafter, simply referred to as “display device4”) which displays an image on the basis of the analog image signals d1R, d1G and d1B. Here, the analog image signals d1R, d1G and d1B outputted by the PC1, are color signals corresponding to red (R), green (G) and blue (B) in this order, and these analog image signals d1R, d1G and d1B are collectively referred to as “analog image signal d1” in some cases. Moreover, the PC1outputs an automatic adjustment start signal s1which is information relating to image quality individually required in each of the applications to be executed, to the display device4by using DDC (Display Data Channel) commands, for example.

The display device4has: an analog/digital converter2(hereinafter, referred to as “ADC2”) which respectively converts the analog image signals d1R, d1G and d1B to digital image signals d2R, d2G and d2B at a resolution of, for example, 8 bits; a CPU (Central Processing Unit)3which controls other blocks in the display device4, communicates with the PC1, and outputs an automatic adjustment completion signal s2indicating that the adjustment of the image quality has been completed; an image processing block6which carries out predetermined data conversions on the respective digital image signals d2R, d2G and d2B and outputs the resulting signals as digital image signals d3R, d3G and d3B; a TFT (Thin Film Transistor) panel5which is a display unit for displaying an image on the basis of the digital image signals d3R, d3G and d3B; and an LUT storing block7which stores a plurality of look-up tables used for γ-characteristic conversion. Here, the digital image signals d2R and d3R are red color signals, the digital signals d2G and d3G are green color signals, and digital image signals d2B and d3B are blue color signals. Hereinafter, in some cases, the digital image signals d2R, d2G and d2B are collectively referred to as “digital image signal d2”, and the digital image signals d3R, d3G and d3B are collectively referred to as “digital image signal d3”. Moreover, the CPU3outputs a gradation adjusting signal s7to the ADC2. However, this gradation adjusting signal s7is not used in the image display system according to the first embodiment, but used in the image display system according to the second embodiment, which will be described later. Therefore, none of description therefor will be given.

FIG. 2is a flow chart showing an adjusting method of image quality in the image display system according to the first embodiment. As shown inFIG. 2, at step ST1, when the user sends an instruction for executing a desired application to the PC1, the PC1starts up the corresponding application, and inputs an analog image signal d1corresponding to the application to the ADC2of the display device4. Then, at step ST2, the PC1inputs the automatic adjustment start signal s1to the display device4, and more specifically to the CPU3. Here, the automatic adjustment start signal s1contains adjustment items of image quality required in the application to be executed by the PC1and adjustment values in the respective adjustment items, and the adjustment items include, for example, luminance, γ-characteristic, contrast and the like.

Further, at step ST3, the display device4adjusts the image quality on the basis of the automatic adjustment start signal s1. More specifically, upon receipt of the automatic adjustment start signal s1, the CPU3controls the other blocks within the display device4so that the image quality is adjusted in accordance with the adjustment items and adjustment values contained in the automatic adjustment start signal s1. Upon completion of the adjustment of the image quality in the display device4, at step ST4, the automatic adjustment completion signal s2is inputted from the display device4, and more specifically from the CPU3to the PC1so that the PC1recognizes that the image quality adjustment has been completed within the display device4. Here, a driver, which forms basic software relating to communications between the PC1and the CPU3in the display device4, is preliminarily installed in the PC1. Moreover, items relating to adjustment functions are different depending on display devices4to be used, for example, in some cases, some display devices4have adjustment functions for γ-characteristic, while the other display devices4have no adjustment functions for γ-characteristic; therefore, the above-described driver is prepared for each of the display devices4, with the items of the adjustment functions that the display device4has and the controlling parameters required for the adjustments being stored in the driver.

Next, referring to examples about adjustment items of image quality contained in the automatic adjustment start signal s1, an adjusting method of image quality will be more specifically described. As one example of applications in which the gradation control is significant, an application using “Clear Type”, which is a smoothing technique of vector font which is one type of the data system of character font, has been proposed. The “Clear Type” is a technique in which respective cells of red (R), green (G) and blue (B) that constitute one pixel of a color liquid crystal display are independently controlled so as to smooth edges of vector font. When the PC1executes the application using the “Clear Type”, coloring in rainbow colors occurs in character edge portions unless the γ-characteristic of the display device4is set to a γ value=2.2 for each of the respective color signals of RGB, resulting in a failure to sufficiently obtain the effects of “Clear Type”. For this reason, the specification of γ value=2.2 is required for the display device4.

In the image display system according to the first embodiment, the γ-characteristic can be adjusted by using, for example, a look-up table, and when the PC1executes an application using the “Clear Type”, the γ-characteristic is adjusted so as to be set to the γ value=2.2. More specifically, when the PC1starts up an application using “Clear Type” (step ST1), the automatic adjustment start signal s1containing information that “the γ-characteristic is adjusted so as to be set to the γ value=2.2” is inputted from the PC1to the CPU3of the display device4(step ST2). Then, the CPU3outputs a LUT switching signal s4to the LUT storing block7so that an instruction is given to the LUT storing block7so as to set the look-up table corresponding to the γ value=2.2 in the image processing block6. Upon receipt of the LUT switching signal s4, the LUT storing block7, which stores look-up tables corresponding to respective γ values, sets the look-up table corresponding to the γ value=2.2 in the image processing block6. Then, the image processing block6carries out a data conversion process on the digital image signal d2in accordance with the look-up table which has been set, adjusts the γ-characteristic to the γ value=2.2, and outputs the digital image signal d3to the TFT panel5(step ST3). The TFT panel5displays an image on the basis of the digital image signal d3. Upon completion of the adjustment of the γ characteristic, the CPU3inputs an automatic adjustment completion signal s2to the PC1(step ST4). Here, no adjusting functions of the γ characteristic are prepared depending on the display device4to be used. However, since the presence or absence of the adjusting functions of the γ-characteristic has been written in the driver that has been preliminarily installed, the automatic adjustment start signal s1is not inputted to the display device4when such a display device4is used. It is noted that the same is true for the other adjustment items for image quality such as luminance and white balance, and in the case when the display device4has no adjusting functions of the respective adjustment items, the automatic adjustment start signal s1is not inputted to the display device4.

Next, the following description will be given of adjustments of image quality in the case where the application to be executed by the PC1is word processor software. In recent years, most of word processors form documents with black characters on the white background. In this case, when the luminance setting of the display device4is too high, eyestrain tends to occur, resulting in degradation in the work efficiency. In the image display system according to the first embodiment, when the PC1executes a piece of word processing software, an adjustment can be carried out so as to set the luminance of the display device4to a lower level. More specifically, when the PC1starts up a piece of word processing software (step ST1), the automatic adjustment start signal s1containing information that “the luminance is set to a low level” is inputted from the PC1to the CPU3of the display device4(step ST2). Then, the CPU3outputs a luminance controlling signal s3to the TFT panel5so that an instruction is given to the TFT panel5so as to lower the luminance setting value. Upon receipt of the luminance controlling signal s3, the TFT panel5, which has, for example, a fluorescent tube, controls an inverter circuit for driving the fluorescent tube so as to lower the luminance (step ST3). Upon completion of the adjustment of the luminance, the CPU3inputs an automatic adjustment completion signal s2to the PC1(step ST4). Moreover, in the case where the word processor software uses “Clear Type”, the automatic adjustment start signal s1also contains the information that “the γ-characteristic is adjusted so as to be set to the γvalue=2.2”, and the γ-characteristic is also adjusted as described above.

Moreover, in the last few years, PCs have been rapidly applied to multimedia, and video streaming, DVDs (Digital Versatile Disks) and the like have come to be widely used; thus, there have been more opportunities to reproduce moving pictures by using a PC. Normally, when moving pictures are viewed, brighter display is preferably used in a manner opposite to the application of the word processor software. In the image display system according to the first embodiment, when the PC1executes an application used for reproducing moving pictures, an adjustment can be made so as to increase the luminance setting of the display device4. More specifically, when the PC1starts up an application used for reproducing moving pictures (step ST1), the automatic adjustment start signal s1containing information that “the luminance is adjusted so as to be set to a higher level” is inputted from the PC1to the CPU3of the display device4(step ST2). Then, the CPU3outputs a luminance controlling signal s3to the TFT panel5so that an instruction is given to the TFT panel5so as to set the luminance setting value higher. Upon receipt of the luminance controlling signal s3, the TFT panel5controls an inverter circuit for driving the fluorescent tube so as to increase the luminance (step ST3). Upon completion of the adjustment of the luminance, the CPU3inputs an automatic adjustment completion signal s2to the PC1(step ST4).

Moreover, in the image display system according to the first embodiment, when the PC1executes an application in which a white-balance adjustment is required, the white-balance adjustment can be carried out in the display device4. More specifically, when the PC1starts up an application in which a white-balance adjustment is required (step ST1), the automatic adjustment start signal s1containing information that “the white-balance is adjusted” is inputted from the PC1to the CPU3of the display device4(step ST2). Then, the CPU3outputs a white-balance controlling signal s5to the image processing block6so that an instruction is given to the image processing block6so as to adjust the white balance. Upon receipt of the white-balance controlling signal s5, the image processing block6carries out a data conversion process on the digital image signal d2in accordance with the contents the signal so that the white-balance is adjusted and the resulting digital image signal d3is outputted to the TFT panel5(step ST3). The TFT panel5displays an image on the basis of the digital image signal d3. Upon completion of the adjustment of the white-balance, the CPU3inputs an automatic adjustment completion signal s2to the PC1(step ST4).

As described above, in the image display system according to the first embodiment, when the display device4receives the automatic adjustment start signal s1which is outputted by the PC1upon executing an application and which includes information relating to image quality required for the application, the display device4adjusts the image quality on the basis of the automatic adjustment start signal s1. Therefore, it becomes possible to display an image with image quality which is suitable for the corresponding application without causing any time-consuming, complex tasks to be carried out by the user. As a result it becomes possible to supply appropriate image quality to the user.

It is noted that, in the first embodiment, an analog interface is adopted as the image signal input interface of the display device4. However, the present invention is also applicable to a case where a display device4using a digital interface or a digital/analog compatible interface is adopted. Also in the display device4using the digital interface, a digital signal receiver is adopted in place of the ADC2. Moreover, in the display device4using the digital/analog compatible interface, both of the ADC2and the digital signal receiver are adopted, and a circuit which switches the ADC2and the digital signal receiver depending on the kinds of the inputted image signal is also provided.

Moreover, in the first embodiment, the automatic adjustment start signal s1is sent to the display device4through DDC commands. However, the automatic adjustment start signal s1may be sent to the display device4by using another interface standard, such as RS-232C.

In addition, in the first embodiment, the TFT panel5is used as a display unit for displaying images. However, another display unit, such as a plasma display panel, may be used.

Second Embodiment

Next, referring again toFIG. 1, an image display system according to the second embodiment will be described. In the image display system according to the second embodiment, the analog input range of the ADC2is further adjusted by using a gradation adjusting signal s7which is not used in the image display system according to the above-described first embodiment. As described above, in order to gradation-display an image appropriately, a gradation-adjusting process for matching the signal level of the analog image signal d1with the analog input range of the ADC2is required. In the second embodiment, this gradation adjustment is carried out by changing the analog input range of the ADC2. Here, the other configurations are the same as those of the image display system according to the above-described first embodiment, Therefore, none of description therefor will be given.

FIGS. 3A,3B and3C show the relationship between the signal level of the analog image signal d1and the analog input range of the ADC2.FIG. 3Ashows a case where the signal level of the analog image signal d1is coincident with the analog input range of the ADC2.FIG. 3Bshows a case where the signal level of the analog image signal d1is not coincident with the analog input range of the ADC2.FIG. 3Cshows a case where the signal level of the analog image signal d1and the analog input range of the ADC2, which have been set to a relationship shown inFIG. 3B, are made coincident with each other by adjusting the analog input range of the ADC2. Here, the respective values shown inFIGS. 3A,3B and3C are indicated relative to 0V, for convenience of description.

As shown inFIG. 3A, in the case where the minimum value α of the signal level of the analog image signal d1is coincident with the minimum value γ of the analog input range of the ADC2and where the maximum value β of the signal level of the analog image signal d1is coincident with the maximum value δ of the analog input range of the ADC2, the analog image signal d1can be converted to a digital image signal d2appropriately at a resolution of 8 bits in the ADC2. Therefore, it is possible to gradation-display an image appropriately. However, depending on the PC1to be connected to the display device4as well as depending on time-based changes in the same PC1, the amplitude of the analog image signal d1tends to become greater. Consequently, as shown inFIG. 3B, there sometimes is a case where the minimum value α of the signal level of the analog image signal d1becomes smaller than the minimum value γ of the analog input range of the ADC2and the maximum value β of the signal level of the analog image signal d1becomes greater than the maximum value δ of the analog input range of the ADC2. In such a case, all the analog image signal d1smaller than the minimum value γ of the analog input range of the ADC2is converted to data “0” (represented by decimal value) by the ADC2. In other words, the data of the digital image signal d2corresponding to such an analog image signal d1is represented by “0” in the decimal system. Moreover, all the analog image signal d1greater than the maximum value δ of the analog input range of the ADC2is converted to data “255” (represented by decimal value) by the ADC2. In other words, the data of the digital image signal d2corresponding to such an analog image signal d1is represented by “255” in the decimal system. Consequently, it becomes impossible to gradation-display an image appropriately.

In the second embodiment as shown inFIG. 3C, even when the signal level of the analog image signal d1is varied, the signal level of the analog image signal d1and the analog input range of the ADC2are made coincident with each other by adjusting the analog input range of the ADC2.

Next, the detailed description will be given of the gradation adjustment carried out by the image display system according to the second embodiment.FIG. 4is a flow chart showing the gradation adjusting method in the image display system according to the second embodiment. In the image display system according to the second embodiment, for example, upon activating the OS (Operating Systems) of the PC1, a gradation adjustment is carried out. As shown inFIG. 4, at step ST10, the PC1turns the gradation adjusting function on upon activating the OS. When the gradation adjusting function is operated, the PC1displays predetermined patterns for gradation adjustment (hereinafter, referred to as “pattern for gradation adjustment”), for example, a black pattern and a white pattern that respectively cover a plurality of pixels, on the TFT panel5at step ST11, and also outputs an automatic adjustment start signal s1to the CPU3of the display device4. Here, in the second embodiment, the black pattern and the white pattern are respectively displayed in a manner so as to cover a plurality of pixels. These pixels constitute, for example, one line of horizontal lines in the display screen of the TFT panel5. In other words, the black pattern and the white pattern are simultaneously displayed on respective horizontal lines in the display screen. Moreover, the automatic adjustment start signal s1according to the second embodiment is a signal which further contains information for giving an instruction so as to start the gradation adjustment to the CPU3, and also contains information relating to image quality individually required for the respective applications as described in the first embodiment when the PC1carries out the application, so that the image display system according to the second embodiment carries out an adjustment on the image quality which is suitable for each of the applications.

The operation at step ST11will be further described. When the gradation adjusting function is turned on, the PC1outputs an analog image signal d1which, allows the TFT panel5to display patterns for gradation adjustment over a plurality of pixels, to the ADC2of the display device4, and also outputs the automatic adjustment start signal s1to the CPU3of the display device4. Then, the ADC2converts the inputted analog image signal d1for displaying the pattern for gradation adjustment to a digital image signal d2, and outputs the resulting signal. Further, the image processing block6carries out a predetermined data conversion on the digital image signal d2, and outputs the resulting signal to the TFT panel5as a digital image signal d3. On the basis of the digital image signal d3thus received, the TFT panel5displays the patterns for gradation adjustment. In other words, each of the black pattern and the white pattern is simultaneously displayed as a single line. Therefore, the analog image signal d1is allowed to have a minimum amplitude value and a maximum amplitude value within one frame period. In other words, the signal level of the analog image signal d1is allowed to have the minimum value and the maximum value within one frame period. Here, on the assumption that the image processing block6is included in the TFT panel5, the TFT panel5displays the black pattern and the white pattern on the basis of the digital image signal d2.

Upon receipt of the automatic adjustment start signal s1, the CPU3starts an adjusting process with respect to the analog input range of the ADC2. More specifically, the maximum value and the minimum value in the analog input range of the AD2are set to various values by altering the reference voltage which specifies the analog input range and is given to the ADC2. At step ST12, the CPU3outputs a gradation adjusting signal s7to the ADC2so that the maximum value in the analog input range of the ADC2is set to the greatest value while the minimum value therein is set to the smallest value. Then, at step ST13, the CPU3monitors the data of the digital image signal d2outputted from the ADC2on a pixel basis during one frame period, and the data corresponding to one frame of the digital image signal d2thus monitored is compared with the maximum value in the digital output range of the ADC2. Here, since the patterns for gradation adjustment are displayed on the display screen of the TFT panel5, comparing the data corresponding to one frame of the monitored digital image signal d2with the maximum value in the digital output range of the ADC2is consequently equivalent to comparing all the data of the digital image signal d2corresponding to the patterns for gradation adjustment with the maximum value in the digital output range of the ADC2. It is noted that, in the second embodiment, since the resolution of the ADC2is set to 8 bits, the maximum value in the digital output range is set to “255” in the decimal system.

Then, as a result of the comparison at step ST13, of the data corresponding to one frame of the monitored digital image signal d2, when the number of data having the value of “255” is not more than a predetermined threshold value A, the CPU3sends the gradation adjusting signal s7to the ADC2at step ST14so as to lower the maximum value in the analog input range of the ADC2by one rank. Then, the above-described step ST13is executed, and of the data corresponding to one frame of the monitored digital image signal d2, when the number of data having the value of “255” is greater than the predetermined threshold value A, the CPU3fixes the maximum value in the analog input range of the ADC2at that time at step ST15; thus, the adjustment of the maximum value in the analog input range in the ADC2is completed.

Next, at step ST16, the CPU3monitors the data of the digital image signal d2outputted from the ADC2on a pixel basis during one frame period, and the data corresponding to one frame of the digital image signal d2thus monitored is compared with the minimum value in the digital output range of the ADC2. Here, comparing the data corresponding to one frame of the monitored digital image signal d2with the minimum value in the digital output range of the ADC2is consequently equivalent to comparing all the data of the digital image signal d2corresponding to the patterns for gradation adjustment with the minimum value in the digital output range of the ADC2. It is noted that, in the second embodiment, since the resolution of the ADC2is set to 8 bits, the maximum value in the digital output range is set to “0” in the decimal system.

Then, as a result of the comparison at step ST16, of the data corresponding to one frame of the monitored digital image signal d2, when the number of data having the value of “0” is not more than a predetermined threshold value B, the CPU3sends the gradation adjusting signal s7to the ADC2at step ST17so as to raise the minimum value in the analog input range of the ADC2by one rank. Then, the above-described step ST16is executed, and of the data corresponding to one frame of the monitored digital image signal d2, when the number of data having the value of “0” is greater than the predetermined threshold value B, the CPU3fixes the minimum value in the analog input range of the ADC2at that time at step S19; thus, the gradation adjustment in the display device4is completed. Further, the CPU3outputs an automatic adjustment completion signal s2to the PC1. In this case, the gradation adjustment is one type of the image quality adjusting processes, and the automatic adjustment completion signal s2, which is information indicating the completion of the image quality adjustment, contains information indicating the completion of the gradation adjustment. Upon receipt of the automatic adjustment completion signal s2, the PC1recognizes that the gradation adjustment has been completed in the display device4, and finishes the display of the patterns for gradation adjustment. More specifically, the PC1stops the output of the analog image signal d1which displays the patterns for gradation adjustment.

Next, the brief description will be given of a setting method of the above-described threshold values A, B. The resolution of the TFT panel5according to the second embodiment is determined on the basis of, for example, XGA (Extended Graphics Array), and capable of displaying 1024×768 dots. In such a TFT panel5, the number of display pixels in the 1H period is 1024 pixels. In the second embodiment, each of the black pattern and the white pattern is displayed on one line of horizontal lines. Therefore, the number of data of the digital image signal d2corresponding to the black pattern is set to 1024, and the number of data of the digital image signal d2corresponding to the white pattern is also set to 1024. Here, taking into consideration that, supposing that the number of display pixels which are under influences of a ringing phenomenon is “a” as shown inFIG. 5, the number of display pixels that are under the ringing phenomenon tends to vary due to the PC1connected thereto, and that noise tends to generate in the analog image signal d1in addition to the ringing phenomenon, the threshold values A and B are set to, for example, “1024−2a”. In this manner, the threshold values A and B are appropriately set so that, even when the analog image signal d1is under the influence of the ringing phenomenon or even when the analog image signal d1is under influence from noise other than the ringing phenomenon, the analog input range of the ADC2can be adjusted without having influences from these. Consequently, the gradation adjustment can be carried out appropriately. Here, with respect to the above-described number of display pixels “a”, it can be set by, for example, experiments.

The gradation adjustment is carried out as described above so that the signal level of the analog image signal d1is made coincident with the analog input range of the ADC2. Thus, it is possible to carry out an appropriate gradation display on an image. Consequently, it becomes possible to supply appropriate image quality to the user.

Moreover, in the second embodiment, the gradation adjustment is carried out by using the results of comparison between the data of the digital image signal d2corresponding to the pattern for gradation adjustment containing the black pattern and the minimum value of the digital output range of the ADC2. Therefore, the minimum value of the signal level of the analog image signal d1is positively made coincident with the minimum value of the analog input range of the ADC2. Furthermore, the gradation adjustment is carried out by using the results of comparison between the data of the digital image signal corresponding to the pattern for gradation adjustment containing the white pattern and the maximum value of the digital output range of the analog/digital converter. Therefore, the maximum value of the signal level of the analog image signal d1is positively made coincident with the maximum value of the analog input range of the ADC2. As a result, it becomes possible to make the signal level of the analog image signal d1and the analog input range in the ADC2almost coincident with each other, and consequently to carry out an appropriate gradation display on an image.

Moreover, in accordance with the image display system according to the second embodiment, the CPU3receives the automatic adjustment start signal s1which is outputted from the PC1in predetermined timing, more specifically, upon activation of the OS, and carries out the gradation adjustment. Therefore, it is possible to carry out an appropriate gradation display without requiring any specific attention of the user, that is, without requiring any time-consuming, complex manual operations by the user, and consequently to supply appropriate image quality to the user without requiring any time-consuming manual operations by the user.

Moreover, in accordance with the image display system according to the second embodiment, comparison is made between all the data of the digital image signal d2corresponding to the patterns for gradation adjustment displayed over a plurality of pixels and the value corresponding to the digital output range in the ADC2, and on the basis of the results of the comparison, a gradation adjusting process is carried out. In other words, the data of the digital image signal d2corresponding to a plurality of pixels is used to carry out the gradation adjusting process. Consequently, for example, the operations from step ST13to step ST17are carried out. In contrast, in the above-described conventional technique, the gradation adjustment is carried out by using only the data of a digital image signal corresponding to one pixel, with the result that it is not possible to carry out the operations from step ST13to step ST17. For this reason, in the case where a ringing phenomenon occurs over several pixels as shown inFIG. 5, it is not possible to carry out a gradation adjustment without receiving the resulting adverse effects. In the image display system according to the second embodiment, for example, by executing the operations from the above-described step ST13to step ST17, it is possible to carry out a gradation adjustment without receiving the resulting adverse effects even when noise such as a ringing phenomenon occurs over several pixels.

Moreover, in accordance with the second embodiment, after the gradation adjustment is completed by the CPU3, the display of the pattern for gradation adjustment is completed. Therefore, patterns that are not required for the user become less conspicuous in comparison with cases where the pattern for gradation adjustment is always displayed.

Furthermore, during the gradation adjusting process, since the pattern for gradation adjustment is partially displayed on the display screen of the TFT panel5, more specifically, since only one line of each of the black pattern and the white pattern is displayed on the display screen, patterns that are not required for the user become less conspicuous in comparison with cases where the pattern for gradation adjustment is displayed over the entire surface of the display screen.

Third Embodiment

FIG. 6is a block diagram showing a configuration of an image display system according to a third embodiment. In the image display system according to the above-described second embodiment, the gradation adjustment is carried out by changing the analog input range of the ADC2. However, in the image display system according to the third embodiment, the gradation adjustment is carried out by changing the signal level of the analog image signal d1. With respect to the configuration thereof, a preamplifier10is further provided to the image display system according to the first embodiment, and in place of the gradation adjusting signal s7outputted to the ADC2, the CPU3outputs a gradation adjusting signal s17to the preamplifier10so that a gradation adjusting process is carried out by changing the signal level of the analog image signal d1.

As shown inFIG. 6, the analog image signal d1, which is outputted from the PC1, is inputted to the preamplifier10, and the preamplifier10is controlled by the CPU3to change the signal level of the analog image signal d1. More specifically, as shown inFIG. 3B, when the signal level of the analog image signal d1is changed, the gain value and bias value of the analog image signal d1are adjusted so that the signal level of the analog image signal d11is made coincident with the analog input range of the ADC2. Then, the analog image signal d1with its signal level being changed is outputted to the ADC2as analog image signals d11R, d11G and d11B. Here, the analog image signals d11R, d11G and d11B are color signals of red, green and blue, in this order, and hereinafter, the analog image signals d11R, d11G and d11B are collectively referred to as “analog image signals d11”. The ADC2converts the analog image signal d11to a digital image signal d2. Since the other configurations are the same as those of the image display system according to the first embodiment, none of description therefor will be given.

Next, the detailed description will be given of gradation adjustments carried out by the image display system according to the third embodiment.FIG. 7is a flow chart showing the gradation adjusting method in the image display system according to the third embodiment. In the image display system according to the third embodiment, for example, upon activating the OS of the PC1, a gradation adjustment is carried out. As shown inFIG. 7, at step ST50, the PC1turns the gradation adjusting function on upon activating the OS. When the gradation adjusting function is operated, the PC1displays predetermined patterns for gradation adjustment, for example, a black pattern and a white pattern that respectively cover a plurality of pixels, on the TFT panel5at step ST51, and also outputs an automatic adjustment start signal s1to the CPU3of the display device4. Here, in the third embodiment, the black pattern and the white pattern are respectively displayed in a manner so as to cover a plurality of pixels. However, these pixels constitute, for example, one line of horizontal lines in the display screen of the TFT panel5. In other words, each of the black pattern and the white pattern is simultaneously displayed as a single horizontal line on the display screen.

The operation at step ST51will be described in more detail. When the gradation adjusting function is turned on, the PC1outputs an analog image signal d1, which is used for displaying the patterns for gradation adjustment over a plurality of pixels on the TFT panel5, to the preamplifier10of the display device4, and also outputs the automatic adjustment start signal s1to the CPU3of the display device4. Then, the preamplifier10changes the signal level of the inputted analog image signal d1uniformly regardless of the kinds of color signals, and outputs the resulting analog image signal d11to the ADC2. Here, in the preamplifier10, since the signal level of the analog image signal d1is uniformly changed regardless of the kinds of color signals, the analog image signal d11is also allowed to display the patterns for gradation adjustment.

The ADC2converts the analog image signal d11, for displaying the inputted patterns for gradation adjustment, to a digital image signal d2, and outputs the resulting signal. Further, the image processing block6carries out a predetermined data conversion on the digital image signal d2, and outputs the resulting signal to the TFT panel5as a digital image signal d3. On the basis of the digital image signal d3thus received, the TFT panel5displays the patterns for gradation adjustment. In other words, the black pattern and the white pattern are simultaneously displayed line by line. Therefore, the analog image signal d1and d11are allowed to have a minimum amplitude value and a maximum amplitude value within one frame period. In other words, the signal levels of the analog image signal d1and d11are allowed to have the minimum value and the maximum value within one frame period. Here, on the assumption that the image processing block6is included in the TFT panel5, the TFT panel5displays the black pattern and the white pattern on the basis of the digital image signal d2.

Upon receipt of the automatic adjustment start signal s1, the CPU3starts adjusting processes with respect to the gain value and bias value of the analog image signal d1. More specifically, at step ST52, the CPU3outputs a gradation adjusting signal s17to the preamplifier10so that the gain value of the analog image signal d1is set to a minimum value, while the bias value thereof is set to a maximum value. Then, at step ST53, the CPU3monitors the data of the digital image signal d2outputted from the ADC2on a pixel basis during one frame period, and the data corresponding to one frame of the digital image signal d2thus monitored is compared with the maximum value in the digital output range of the ADC2. Here, since the patterns for gradation adjustment are displayed on the display screen of the TFT panel5, comparing the data corresponding to one frame of the monitored digital image signal d2with the maximum value in the digital output range of the ADC2is consequently equivalent to comparing all the data of the digital image signal d2corresponding to the patterns for gradation adjustment with the maximum value in the digital output range of the ADC2. It is noted that, since the resolution of the ADC2is set to 8 bits, the maximum value in the digital output range is set to “255” in the decimal system.

Then, as a result of the comparison at step ST53, of the data corresponding to one frame of the monitored digital image signal d2, when the number of data having the value of “255” is not more than a predetermined threshold value A, the CPU3sends the gradation adjusting signal s17to the preamplifier10at step ST54so as to raise the gain value of the analog image signal d1by one rank. Then, the above-described step ST53is executed, and of the data corresponding to one frame of the monitored digital image signal d2, when the number of data having the value of “255” is greater than the predetermined threshold value A, the CPU3fixes the gain value of the analog image signal d1at that time at step ST55; thus, the adjustment of the gain value is completed.

Next, at step ST56, the CPU3monitors the data of the digital image signal d2outputted from the ADC2on a pixel basis during one frame period, and the data corresponding to one frame of the digital image signal d2thus monitored is compared with the minimum value in the digital output range of the ADC2. Here, comparing the data corresponding to one frame of the monitored digital image signal d2with the minimum value in the digital output range of the ADC2is consequently equivalent to comparing all the data of the digital image signal d2corresponding to the patterns for gradation adjustment with the minimum value in the digital output range of the ADC2. It is noted that, since the resolution of the ADC2is set to 8 bits, the maximum value in the digital output range is set to “0” in the decimal system.

Then, as a result of the comparison at step ST56, of the data corresponding to one frame of the monitored digital image signal d2, when the number of data having the value of “0” is not more than a predetermined threshold value B, the CPU3sends the gradation adjusting signal s17to the preamplifier10at step ST57so as to lower the bias value of the analog image signal d1by one rank. Then, the above-described step ST56is executed, and of the data corresponding to one frame of the monitored digital image signal d2, when the number of data having the value of “0” is greater than the predetermined threshold value B, the CPU3fixes the bias value of the analog image signal d1at that time at step S59, and outputs the automatic adjustment completion signal s2to the PC1. Upon receipt of the automatic adjustment completion signal s2, the PC1recognizes that the gradation adjustment has been completed in the display device4, and finishes the display of the patterns for gradation adjustment. More specifically, the PC1stops the output of the analog image signal d1that displays the gradation adjusting-use patterns. Here, with respect to the setting method of the threshold values A and B, the same processes as those of the above-described second embodiment are carried out. Therefore, none of description therefor will be given.

By carrying out the gradation adjustment as described above, it becomes possible to make the signal level of the analog image signal d11coincident with the analog input range of the ADC2. Therefore, it is possible to carry out appropriate gradation display of an image by using a configuration and method different from those of the above-described second embodiment. Consequently, it is possible to supply appropriate image quality to the user.

It is noted that, different from the image quality adjustment carried out by the image display system according to the first embodiment, since it is not necessary for the image display systems according to the second and third embodiments to carry out the image adjusting process each time the PC1executes an application, the gradation adjustment is carried out, for example, upon activation of the OS. However, the gradation adjustment may be carried out in another timing. Moreover, it is preferable to carry out the gradation adjustments a plurality of times every time a different type of the PC1is connected. However, in the case of a system without requiring high precision, only one time of the gradation adjustment may be carried out for each PC1.