JPH11316577A - Display device adjustment method - Google Patents

Abstract

(57) [Problem] To perform various adjustments of a display device, cancel a variation in luminance caused by the light source when irradiating light from a light source built in the product to the liquid crystal panel, and remove the light from the light source. Even when the intensity is abnormal, a high-quality display device is realized by accurately setting the gamma correction characteristics. In a luminance measurement of a display device, a sensor (4) is used.
And a transmitted light measurement is performed using the reference sensor 5A, and a correction value is calculated based on the fluctuation data of the reference data based on the measurement data obtained by the sensor 4 and the reference data obtained by the reference sensor 5A. Correction and later conversion to gradation values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly to a display device which does not emit light.
That is, the present invention relates to an adjustment method in a display device having a light source and an optical modulation element.

[0002]

2. Description of the Related Art As a display device using a display light source such as a backlight and an optical modulation element, for example, a liquid crystal display device, an electroluminescence (EL), and a digital micromirror device (DMD) are known. In such a display device, for example, a liquid crystal display device, various adjustments described below are performed as one process in a manufacturing stage in a factory production line. Here, as an example, in an active matrix type liquid crystal display device using a TFT (thin film transistor) as a pixel switch, the above-described various adjustment methods when displaying in a normally white mode, and a general relationship between light intensity and applied voltage. explain.

Generally, in a TFT liquid crystal display device,
One of the two substrates in which liquid crystal is sealed is a TFT active matrix substrate, the other substrate is a counter substrate, and a common electrode is formed. Further, on the TFT active matrix substrate, a pixel electrode connected to each TFT serving as a pixel switch is formed. Then, a signal voltage is applied to the pixel electrode, a constant common voltage is applied to the common electrode of the counter substrate, and a liquid crystal of each pixel is supplied with a common voltage to the common electrode and a signal voltage to the pixel electrode. A difference voltage is applied.

In the normally white display method, as shown in FIG. 17, the smaller the difference voltage between the signal voltage and the common voltage, the brighter the image display, and the larger the difference voltage, the darker the image display. Here, in the graph of FIG. 17, the vertical axis represents the transmittance T (brightness), and the horizontal axis represents the voltage V (positive voltage (+), negative voltage (-)). , The relationship between the difference voltage from the opposing substrate voltage and the transmittance. That is, in the liquid crystal display device, when the difference voltage from the counter substrate voltage is small, the transmittance increases and the image display becomes bright, and when the difference voltage from the counter substrate voltage is large, the transmittance decreases and the image display becomes dark. It becomes.

FIG. 18 shows a change in signal voltage when the voltage applied to the liquid crystal is inverted for driving.
That is, in FIG. 18, the common voltage 1
Image signal 2 on the positive polarity side when driving with respect to the positive polarity
5 shows changes in the voltages of the image signals 3 on the negative polarity side when the negative polarity driving is performed.

In such a liquid crystal display device, as a first adjustment item, there is adjustment of a common voltage to a common electrode (referred to as common adjustment). This adjusts the common voltage 1 applied to the common electrode on the opposing substrate shown in FIG. 18, and an image without flicker is obtained on the screen by this adjustment.

As a second adjustment item, there is contrast adjustment or dynamic range adjustment. This is shown in FIG.
8, the maximum value 2 of the voltage of the image signal 2 on the positive polarity side
The contrast ratio is adjusted by simultaneously adjusting the amplitude VA between A and the minimum value 2B of the voltage and the amplitude VB between the minimum value 3A and the maximum value 3B of the voltage of the image signal 3 on the negative polarity side. is there.

As a third adjustment item, there is a DC offset adjustment. This is an adjustment for setting to which area a voltage is applied and handed to a user in an applied voltage-light intensity characteristic described later. The DC level is adjusted while the voltage amplitude of the image signal is kept constant. Is what you do.

This is because the voltage VC between the maximum value 2 A of the voltage of the positive polarity image signal 2 shown in FIG.
And the absolute value of the voltage VD between the common voltage 1 and the minimum value 3A of the negative image signal 3 is adjusted to the same offset voltage. In other words, by adjusting the offset voltage while viewing the image displayed on the liquid crystal panel or the color image projected on the projector screen in the case of a projector, each color in the case of positive drive and negative drive can be adjusted. Levels are determined simultaneously. This DC offset adjustment is generally performed while white display is performed on the liquid crystal panel, and is also referred to as white balance adjustment.

As a fourth adjustment item, there is a setting of a gamma correction characteristic. The liquid crystal display device has a gamma correction circuit in the data processing circuit, and as shown in FIG.
First, an applied voltage (V) -transmittance (T) characteristic unique to a liquid crystal panel is measured. Then, the applied voltage −
FIG. 19B shows correction data necessary for correcting the transmittance characteristic to a linear characteristic as shown in FIG.
Are determined. Further, FIG.
The applied voltage obtained by the luminance measurement shown in FIG.
The gamma correction is completed by combining the transmittance characteristic with the gamma correction characteristic of FIG. 19B to obtain a linear input / output characteristic as shown in FIG. 19C.

[0011]

Here, in performing the various adjustments of the display device as described above, it is necessary to irradiate light from a light source incorporated in an actual product, for example, a backlight toward a liquid crystal panel. .

At this time, as shown in FIGS. 2A and 2B, the brightness of this type of light source is not always constant. Here, in the graphs shown in FIGS. 2A and 2B, both the vertical axis represents luminance (lux) and the horizontal axis represents time, but the unit of the horizontal axis in FIG. Is msec
In contrast, the unit of the horizontal axis in FIG. 2B is sec.

The graphs of FIGS. 2A and 2B are obtained by measuring the luminance of different light sources.
As shown in (A) and (B), even with the same rating, there are manufacturing variations. Therefore, if the light source is different, the luminance-time characteristic waveform is also different. For example, a metal halide lamp usually used as a backlight is used. In the discharge tube described above, a luminance variation of about 10% occurs depending on the discharge state and the like. In particular, this variation in luminance is shown in FIG.
As can be seen in (B), it may occur in a short time and / or a long time.

If the light intensity from the light source decreases or increases during the adjustment, the measurement required for the third and fourth adjustment items among the above-described adjustment items is hindered. In other words, if the DC offset adjustment and the setting of the gamma correction characteristic are performed when the light intensity from the light source is abnormal, it is impossible to perform appropriate white display and gamma correction when the light intensity from the light source is normal.

Therefore, an object of the present invention is to correct data obtained in measurement for performing various adjustments of a display device, irrespective of the variation in luminance due to a light source, thereby achieving high correction. An object of the present invention is to realize a quality display device.

Another object of the present invention is to further improve the reliability of optical modulation by further performing DC offset adjustment.

[0017]

According to a first aspect of the present invention, a method for adjusting a display device includes a light source and an optical modulation element for modulating light from the light source based on an applied voltage. A first step of changing and setting the applied voltage in accordance with the gradation value, and measuring the light intensity modulated by the optical modulation element corresponding to at least one pixel; and For each measurement, an applied voltage corresponding to a gradation value that is always constant is set, and the reference light intensity modulated by the optical modulation element corresponding to a pixel at a reference position different from the at least one pixel is set. A second step of measuring each, and a third step of correcting the light intensity of each gradation measured in the first step based on the reference light intensity measured in the second step, It is characterized by having.

Therefore, according to the display device adjusting method of the present invention, the reference light intensity at the reference position obtained in the second step is set by changing the applied voltage in the first step. By measuring each time the light intensity is measured, the variation in the light intensity for reference can be referred to, and thus, the variation in the light intensity due to the light source can be qualitatively measured. Correcting the light intensity obtained in the first step based on the light intensity measured corresponding to each gradation value to create ideal measurement data in consideration of the light intensity variation of the light source. Can be. The two types of light intensity measurement do not need to be completely at the same timing, and the two types of light intensity measurement may be switched and executed in a relatively short time. In short, when the light intensity is measured by changing and setting the applied voltage, any timing may be used as long as the light intensity of the light source itself used for the light intensity measurement can be measured for reference.

According to a second aspect of the present invention, in the method for adjusting a display device according to the first aspect, in the second step, the measurement is performed by setting the applied voltage corresponding to the maximum gradation value. And

Therefore, according to the display device adjusting method of the present invention, by setting the applied voltage corresponding to the maximum gradation value at the time of each measurement at the reference position, the relative position of the light source is set. Variation in light intensity can be measured.

According to a third aspect of the present invention, in addition to the feature of the second aspect, the display device includes a plurality of types of optical modulation elements, and the measurement is performed by the optical modulation device. It is performed for each element.

Therefore, according to the method of adjusting a display device according to the third aspect, color display can be performed by using a plurality of types of optical modulation elements. The light intensity obtained in the first step can be corrected in consideration of the variation of the light intensity of the light source.

According to a fourth aspect of the present invention, there is provided a method for adjusting a display device having a light source and an optical modulation element for modulating light from the light source based on an applied voltage. To change and set the applied voltage,
A first step of measuring the light intensity modulated by the optical modulation element corresponding to at least one pixel;
A second step of measuring the light intensity from the light source for each reference in each measurement in the step, and the first step based on the reference light intensity measured in the second step.
And a third step of correcting the light intensity for each gradation measured in the step.

Therefore, according to the display device adjusting method of the fourth aspect, in the second step, the intensity of light before reaching the optical modulation element is measured for reference.
It is possible to qualitatively measure the variation in light intensity due to the light source at each measurement, and to compare and refer to the light intensity measured for the reference and the light intensity measured for each of the gradation values, The light intensity obtained in the first step can be corrected in consideration of the light intensity variation of the light source. The second step can be performed by using a reference light measuring means disposed inside the display device.

According to a sixth aspect of the present invention, there is provided the display device adjusting method according to any one of the first to fifth aspects, wherein in the third step, the reference light intensity measured in the first measurement and the first light intensity are measured. It is characterized in that each correction value is calculated by comparing the light intensity for each reference obtained in each subsequent measurement with each other.

Therefore, according to the display device adjusting method of the present invention, the reference light intensity obtained in each of the above measurements is based on the reference light intensity obtained in the first measurement. Therefore, since the correction value can be calculated for each measurement, the variation of the light intensity of the light source can be reflected on the correction value.

According to a seventh aspect of the present invention, in addition to the features of any one of the first to fifth aspects, in the third step, the reference light intensity measured for each measurement is measured in the third step. The correction value is calculated by comparing the average value with the reference light intensity obtained in each measurement.

Therefore, according to the display device adjusting method of the present invention, the reference light intensity obtained in each of the above measurements is based on the average value of the reference light intensity measured in each of the above measurements. Since the correction value can be calculated for each measurement from the light intensity of the light source, the variation of the light intensity of the light source can be reflected on the correction value.

According to the eighth aspect of the present invention, in addition to the features of the seventh aspect, in the third step, in the third step, an initial value of the standardized light intensity for the reference and the value obtained in each measurement are obtained. Each correction value is calculated by comparing the obtained reference light intensity with the corresponding reference light intensity.

Therefore, according to the display device adjusting method of the present invention, the reference light intensity obtained in each of the above measurements is based on the reference light intensity initial value set as the standard. Thus, the correction value for each measurement can be calculated, so that the correction value can reflect variations in the light intensity of the light source.

According to a ninth aspect of the present invention, in the method for adjusting a display device according to any one of the first to eighth aspects, the third step converts the corrected light intensity into a gradation value. It is characterized by including a step.

Therefore, according to the display device adjusting method of the ninth aspect, the corrected light intensity is converted into a gradation value, so that the gradation value considering the light intensity variation of the light source is considered. Can be obtained.

According to a tenth aspect of the present invention, there is provided a display device adjusting method comprising the steps of: adjusting a gamma based on each of the correction values obtained in the third step in addition to the features described in the first to ninth aspects. The method further includes a step of determining a correction characteristic.

Therefore, according to the display device adjusting method of the present invention, since the correction value can be calculated before the gamma correction, the gamma correction is performed based on the correction value. In the step of determining, the data to which the variation in light intensity of the light source is fed back can be used as basic data for gamma correction,
Higher accuracy gamma correction characteristics can be obtained.

According to an eleventh aspect of the present invention, in addition to the feature of the tenth aspect, the input digital data is
A step in which the gamma correction characteristic is corrected by a gamma correction circuit in which the gamma correction characteristic is set, and the applied voltage at the optical modulation element is converted into digital image data suitable for the optical modulation characteristic; and the digital image data is transmitted to a DA converter. Converting the analog image data with an amplifier, amplifying the analog image data with an amplifier, modulating the optical modulation element based on the amplified analog image data, and displaying an image. When the gradation value of the input digital image data to the gamma correction circuit is the maximum and the gradation value of the output digital image data from the gamma correction circuit is smaller than the maximum value, the amplification factor of the amplifier is adjusted. Changing the display image to increase the dynamic range of the display image.

Therefore, according to the display device adjusting method of the present invention, since the bias can be adjusted after the DA conversion, the gain of the image signal can be increased, and the contrast ratio of the display device can be reduced. Can be improved.

According to a twelfth aspect of the present invention, in addition to the feature of the eleventh aspect, the amplifier comprises an operational amplifier.
The amplifier changes a bias potential supplied to the operational amplifier.

According to the display device adjusting method of the twelfth aspect, the bias can be easily adjusted after DA conversion by the amplifier, so that the contrast ratio of the display device can be easily improved. .

According to a thirteenth aspect of the present invention, in addition to the feature of the tenth aspect, in addition to the feature of the tenth aspect, the digital data is
A step of correcting by the gamma correction circuit in which the gamma correction characteristic is set to obtain digital image data suitable for the applied voltage-optical modulation characteristic in the optical modulation element; Converting the image data into analog image data with a DA converter based on a reference voltage, amplifying the analog image data with an amplifier, and modulating the optical modulation element based on the analog image data Driving and displaying an image, wherein the gradation value of the input digital image data to the gamma correction circuit is the maximum, and the gradation value of the output digital image data from the gamma correction circuit is larger than the maximum value. An adjusting step of changing the reference voltage of the DA converter when the value is smaller to expand the dynamic range of the displayed image. .

Therefore, according to the display device adjusting method of the present invention, since the reference voltage of the DA converter can be adjusted, the gain of the DA converter can be adjusted, and the contrast ratio of the display device can be adjusted. Can be improved.

According to a fourteenth aspect of the present invention, in addition to the feature of the tenth aspect, the input digital data is
A step of correcting by the gamma correction circuit in which the gamma correction characteristic is set to obtain digital image data suitable for the applied voltage-optical modulation characteristic in the optical modulation element; Converting the image data into analog image data by a DA converter based on a reference voltage, and setting a voltage corresponding to a minimum gradation value of the analog image data to a predetermined clamp voltage by a clamp circuit And a step of modulating the optical modulation element based on the analog image data to display an image, and changing a clamp voltage in the clamp circuit,
Adjusting the DC offset amount of the analog image data with respect to the reference voltage to adjust the white balance.

Therefore, according to the display device adjusting method of the present invention, since the DC offset amount can be adjusted by the clamp circuit, the white balance of the display device can be adjusted.

According to a fifteenth aspect of the present invention, in the method for adjusting a display device according to any one of the first to fourteenth aspects, the display device is a projection display device, and the measurement in the first step is performed in the first step. , For the pixels on the screen,
The measurement in the second step is performed on a pixel at the reference position on the screen.

Therefore, according to the display device of the fifteenth aspect, since the adjustment of the projection type display device can be performed, the image quality of the projection type display device can be improved.

[0045]

Embodiments of the present invention will be described below with reference to the drawings. First, an outline of a display device in which the adjustment of the present invention is performed will be described.

First Embodiment (Overall Description of Display Device) FIG. 3 is a block diagram schematically showing an entire display device for driving a liquid crystal display panel. The liquid crystal display device of the present embodiment shown in FIG. 3 is applied to a projector using three liquid crystal display panels as R, G, and B light valves, respectively.
In the present embodiment, three liquid crystal display panels are referred to as TF
Although an active matrix substrate using T as a switching element is used, another liquid crystal display substrate can be used.

In FIG. 3, the liquid crystal display device of the projector is roughly divided into signals used for data processing of red (hereinafter, referred to as R), green (hereinafter, referred to as G), and blue (hereinafter, referred to as B). Processing board 10 and liquid crystal display dedicated boards 30R, 30G, 30B provided for each color R, G, B
And three liquid crystal display panels 50R, 50G, and 50B respectively functioning as three light valves.

The signal processing board 10 includes various circuits (not shown) for a projector which is an electronic apparatus of the present embodiment.
In addition, an overall control board on which elements and circuits realizing the following functions are mounted may be used.

First, NT is used as an input terminal for image data.
The first to input analog TV signals such as SC and PAL
And a second input terminal 14 for inputting a digital image signal such as a computer output or a CDROM output.
And Here, the analog television signal input to the first input terminal 12 has been subjected to gamma correction in consideration of the characteristics of the CRT, but the digital television signal input to the second input terminal 14 Is not gamma corrected. It is also possible to provide another terminal for inputting a digital image signal subjected to gamma correction for CRT, such as a CCD camera output.

The AD converter 1 is connected to the first input terminal 12.
6 are connected to perform analog-to-digital conversion of the television signal. Further, the AD converter 16 has a digital decoder 18.
Is connected. The digital decoder 18 decodes a luminance signal Y and color difference signals U and V in a television signal into R, G, and B signals of three colors.

At a stage subsequent to the digital decoder 18, a frame memory 20 is provided. The data input through the first input terminal 12 is input into the frame memory 20 via the AD converter 16 and the digital decoder
It is written for the frame. Digital R, G, and B data input through the second input terminal 14 is directly written into the frame memory 20. The liquid crystal display panel 50
When the interlaced scanning is performed in R, 50G, and 50B, R, G, and B data for one frame are read out of the frame memory 20 in two fields in the order of odd-numbered lines and even-numbered lines. It is.

Here, although not particularly shown, a liquid crystal driving IC mounted on the liquid crystal display dedicated board 30R and a liquid crystal driving IC used for displaying other colors G and B shown in FIG. The configuration of the IC is the same.

A gamma correction circuit 32 is provided on the liquid crystal display dedicated board 30R. Further, a phase expansion circuit 34 is provided at a stage subsequent to the gamma correction circuit 32. The phase expansion circuit 34 performs data phase expansion in order to reduce the driving frequency of the liquid crystal display panel 50R.

A polarity inverting circuit 36 is provided at a stage subsequent to the phase expanding circuit 34. The polarity inversion circuit 36 is provided for inverting the polarity of the electric field applied to the liquid crystal of each pixel of the liquid crystal display panel 50R at a predetermined cycle to drive the polarity inversion. In the present embodiment, since the switching element of the liquid crystal display panel is constituted by a TFT, the TFT
The polarity of the data potential supplied to the pixel is inverted at a predetermined timing with respect to the potential of the common electrode formed on the substrate facing the substrate, and the pixel is driven. For this purpose, the polarity inversion circuit 36 generates and outputs data having a positive potential and data having a negative potential with respect to the potential of the common electrode.

A DA converter 38 is provided downstream of the polarity inversion circuit 36, and performs digital-to-analog conversion on the polarity-inverted data of the N lines that have undergone phase development. This analog signal is the output of the liquid crystal display drive IC.

Although not shown, the liquid crystal display driving IC is provided with a timing generation circuit, and a timing signal required by the phase expansion circuit 34, the polarity inversion circuit 36, and the DA converter 38 is an image synchronization signal. Is generated based on

The liquid crystal display dedicated board 30R is further provided with an amplifier 40 and a buffer 42. The data on which the bias voltage corresponding to the positive and negative polarity inversion drive is superimposed by the amplifier, for example, the operational amplifier 40, is supplied to the liquid crystal display panel 50R via the buffer 42, and the liquid crystal display panel 50R is controlled based on the data. 1 dot or 1
The polarity inversion driving is performed every predetermined period such as every line.

The main purpose of the gamma correction circuit 32 is to perform gamma correction suitable for the applied voltage-transmittance characteristics of each liquid crystal display panel. Since the applied voltage-transmittance characteristics are different for each liquid crystal display panel, they need to be adjusted as described later. Since the gamma correction circuit 32 is mounted on a board dedicated to liquid crystal display and integrated with the display panel, the adjustment process is simplified and the calculation is simplified, so that highly accurate correction can be performed. .

(Luminance Measurement Method) FIGS. 1A to 1C
FIG. 2 shows a schematic diagram of a luminance measuring device of the display device according to the first embodiment. In the first embodiment, the luminance measurement of a liquid crystal display device, for example, a projector is performed for each of R, G, and B panels, and the measurement is performed with the gradation value as shown in FIG. The measurement is performed by projecting an image for each of R, G, and B colors from the projector 8 to the projector screen 6 via the lens 7 using the measuring device 9, the sensor 4, and the reference sensor 5 </ b> A.

At this time, the projector screen 6 is provided with light transmitting means 13A and 13B so that the light from the projector 8 is directly incident on the sensors 4 and 5A. In order to measure the brightness of light on the projector screen 6, the sensors 4 and 5A are installed so as to be in contact with the light transmitting means 13A and 13B on the projector screen 6.

Here, the light transmitting means 13A and 13B are
The light from the projector 8 is prevented from being blocked by the projector screen 6, and may be configured by, for example, a means of partially providing a hole or making the light transparent.

FIG. 1B shows that the light transmitting means is provided with openings 13A,
13B shows an example of a screen 6 having 13B. These openings 13A and 13B are preferably provided line-symmetrically at positions separated by a distance L1 from the vertical center line L of the screen 6. This is because the optical system of the projector is designed so that the illuminance is equal at each line-symmetric position with respect to the vertical center line L of the screen 6.

Further, as shown in FIG. 1B, areas 13C and 13D indicated by hatching in the figure are black-displayed around the openings 13A and 13B at the time of measurement, and these areas are used as masks. Is preferred. That is, FIG.
As shown in (C), each of the sensors 4 and 5A receives light in the range of the angle ψ, but the masks 13C and 13D can prevent light other than the measurement light from being incident on each of the sensors 4 and 5A.

As the reference sensor 5A,
The reference data is measured by using a device having the same specifications as that of the sensor 4 and always displaying a predetermined gradation, for example, white, on the pixel projected on the position corresponding to the reference sensor 5A on the projector screen 6. I do.

The measurement of the luminance by the sensor 4 is performed by changing the gradation of the display area corresponding to the opening 13A and measuring the luminance at each gradation by the sensor 4. That is, by doing so, the voltage applied to the liquid crystal corresponding to each gradation can be
The correlation with the transmittance of the liquid crystal to which the voltage is applied is measured.

The sensor 4 and the reference sensor 5A are:
The measurement data Mes measured by the sensor 4 and the reference data Ref measured by the reference sensor 5A are connected to the gradation value measuring device 9 via the cable 11A and input to the gradation value measuring device 9, respectively. Correction of the measurement data Mes based on the reference data Ref to be performed, and a luminance value-gradation value conversion is performed on the corrected luminance value Lux calculated by the correction, and a corrected gradation value Data is calculated.

In order to measure the luminance with the sensors 4 and 5A, the image projected on the projector screen 6 is changed in gradation value only for each measurement in the area of the opening 13A, and is always white in the area of the opening 13B. Is displayed and the mask area 13C,
13D always displays black. Therefore, at the time of luminance measurement, image data capable of displaying such a projected image is supplied. It should be noted that a modification of the method of displaying the projected image at the time of measuring the luminance will be described later with reference to FIGS.

Further, when measuring the brightness with the sensors 4 and 5A, sampling can be performed simultaneously by synchronizing the two sensors 4 and 5A. May be performed once or more than once.

In the luminance measurement, the light incident on the sensor 4 and the reference sensor 5A is photoelectrically converted and output as an electric signal to the first data bus formed by the cable 11A to measure the gradation value. Table 9
The correction luminance Lux is calculated by a method described later based on the measurement data Mes and the reference data Ref obtained in each measurement by data processing on the gradation value measuring device 9 side. You. Thereafter, the corrected gradation values Data calculated by normalizing the corrected luminance Lux are output to the second data bus formed by the cable 11B, and are fed back to the projector 8.

The corrected gradation value Data is input to the data correction circuit 23 in the data processing circuit mounted on the projector 8.
The gamma correction characteristic is determined based on the data. Further, the gamma correction circuit 32 shown in FIG.
Based on gamma correction characteristics stored in M, RAM, etc.
Gamma correction is performed on input digital data.

(Method of Extracting Corrected Tone Value from Measurement Data) As described in the brightness measurement method, the brightness measured by the sensor 4 and the reference sensor 5A shown in FIG. After that, it is converted into normalized data.

FIG. 4A shows a gradation value calculated from the luminance of the light source built in the projector 8 shown in FIG. 1 and a corrected luminance Lux calculated from the measurement data of the projector 8 for every 32 gradations. A table in which an example of the corrected gradation value is normalized in a range of 0 to 255 is shown. In FIG. 4A, a raster signal Xm, which is a liquid crystal panel drive signal as an input signal, is supplied with R, G,
The corrected gradation values Ym (R), in which the corrected luminance values obtained by correcting the transmittance measured in the respective panels of B, are normalized,
Ym (G) and Ym (B). here,
The raster signal Xm includes drive signals Xm (R), Xm (G), and Xm corresponding to R, G, and B panels.
(B), each of which is individual, R, G, B
The measurement is performed for each raster signal for each panel, but due to data processing, items in the table of FIG. 4A are omitted, and are represented by “raster signal Xm”.

That is, each numerical value in the table of FIG. 4A is represented by a gradation value after correcting each measurement data of the luminance of light transmitted through each of the R, G, and B panels, and normalizing the data. Things. In this normalization, the maximum value of the corrected gradation value is 255 and the minimum value is 0. For example, in each measurement data, the maximum value of the corrected luminance value of R is Rmax, the minimum value is Rmin, and the minimum value is Rmin. The corrected luminance value is Rx, the maximum corrected luminance value of G is Gmax, the minimum value is Gmin, each corrected luminance value is Gx, the maximum corrected luminance value of B is Bmax, and the minimum value is Bmi.
n, assuming that each corrected luminance value is Bx, the corrected gradation values Ym (R), Ym (G), and Ym (B) of R, G, and B are calculated by the following equations 1 to 3, respectively. It is.

Formula 1; Ym (R) = 255 × (Rx-Rmi
n) / (Rmax-Rmin) Formula 2: Ym (G) = 255 × (Gx-Gmin) / (Gmax
−Gmin) Equation 3; Ym (B) = 255 × (Bx−Bmin) / (Bmax)
-Bmin) Then, since each gradation value in the table of FIG. 4A is represented by 9 gradations, the interval between the gradations is 256 / (9-1) from 0 to 255. The display is performed every 32 gradations. FIG. 4A shows corrected gradation values Ym (R), Ym (G), and Ym for each color calculated from the measured data and the corrected luminance value using the formulas 1 to 3.
Although m (B) is shown, a graph of this is shown in FIG. 4 (B). In FIG. 4B, the vertical axis represents the corrected gradation value Y of the light transmitted through each of the R, G, and B panels.
m (R), Ym (G), and Ym (B), where the horizontal axis is the grayscale value Xm of the raster signal, and three types of correction grayscale values for each of the R, G, and B panels. A graph is shown.

As described above, in color display on a liquid crystal display device such as a projector, three panels of R, G, and B are used. The correction gradation values Ym (R), Ym (G), and Ym (B) are calculated from the correction described later.

Although the present invention can adjust the display device by the method described above, conventionally, the display device is corrected by using the reference data to calculate the corrected luminance value and then normalized. Has not been adjusted by the method described above, the tone value is calculated only by a simple luminance-to-tone value conversion of the measured data, and used as data to be subjected to gamma correction. Has been adjusted visually by projecting an image on a projector screen based on each of the above tone values of the transmitted light.

That is, as described above, the relationship between the time and the luminance in the light source is not constant, but varies, so that the gradation value Xm of the raster signal in FIG.
Is 96, the measured data of the panel transmitted light is, for example, 100, and when the gradation value Xm of the raster signal is 128, the measured data of the panel transmitted light is, for example, 95. . In such a case, the luminance does not increase in proportion to the gradation value, and the proportional relationship is broken. Therefore, even if the measurement data itself is normalized, the applied voltage-light intensity characteristics become inaccurate. Was. Therefore, when measuring the point where the luminance is saturated, if 98% is calculated with respect to 100%, if the deviation is 5% due to the variation of the light source, the reliability of the calculated gradation value is reduced. In addition, visual adjustment was required.

For example, FIG. 5 is a graph showing the luminance variation of the light source and the time-gradation characteristics of the projector. In FIG. 5, the horizontal axis indicates the number of times of measuring the luminance of the projector, and the vertical axis indicates the gradation. As shown in FIG. 5, the luminance of the light source is not constant at each luminance measurement, but varies at each measurement. For example, as is clear from FIG. 5, as the luminance of the light source increases, the gradation of the display panel of the projector also increases, and as the luminance of the light source decreases, the gradation of the projector also decreases.

Therefore, in the present embodiment, when the luminance of the display device is measured, not only the measurement by the sensor 4 but also the luminance as the reference data is measured simultaneously by the measurement by the reference sensor 5A as shown in FIG. ,
This is to correct the measured data.

That is, when the applied voltage-light intensity characteristic is measured for each gradation, conventionally, data obtained by normalizing the measured data itself without taking into account the luminance variation of the light source generated for each measurement is obtained by a projector or the like. Is stored as an applied voltage-light intensity characteristic in a storage unit in the display device, and gamma correction has been performed based on this.
It was impossible to have proper gamma correction data. However, by performing the measurement by adjusting the display device using the adjustment method of the present embodiment, the measurement data Mes
Is corrected based on the correction value calculated by the reference data Ref, and then normalized, and the corrected gradation value Data obtained after the normalization is used as gamma correction target data, so that proper gamma correction data is obtained. It is possible to make it.

As a method for correcting the measurement data, there are three methods described below.

(1) Each reference data Ref is compared with the reference data Ref0 in the first measurement or the average value RefA of each reference data Ref, and a correction value for each measurement is calculated. Mes is decreased by the correction value.

Here, the reference data at the time of the first luminance measurement is Ref0, the measured data is Mes0, the corrected measurement data is a corrected luminance value Lux0, and thereafter 1, 2,.
, N. Then, each corrected luminance value Lux is converted into each measurement data Mes, each reference data Ref, and the reference data Re obtained by the first measurement serving as a reference.
It is calculated by the following equations 4 to 7 based on f0.

Equation 4; Lux0 = Mes0 Equation 5; Lux1 = Mes1 / [1+ (Ref1-Ref)
0) / Ref0] Expression 6; Lux2 = Mes2 / [1+ (Ref2-Ref)
0) / Ref0] Equation 7; Luxn = Mesn / [1+ (Refn−Ref)
0) / Ref0] According to this adjustment method, for example, as shown in the table of FIG. 6, the measured data Mes when the gradation of the raster signal is measured at n, n + 1, n + 2 is 80. , 89,9
3. Each reference data Ref is 100, 105,
97, the reference data R at the time of the first measurement
ef0 becomes 100. Therefore, when the reference data Ref0 at the time of the n-th gradation is used as the reference value, (Ref1-Ref0) is +5 at the time of the n + 1-th gradation, and (Ref2-Ref0) is -3 at the time of the n + 2-th gradation. The corrected luminance value Lux as the data to be normalized is calculated by Expressions 4 to 7 based on
0, Lux1 is calculated as 84.76, and Lux2 is calculated as 95.88.

Note that this correction method can be applied to the case where the brightness of the lamp fluctuates even for a relatively long time and data is collected over a long time, as shown in FIG. 2 (B).

Each corrected luminance value Lu is calculated using the average value RefA of each reference data Ref in each measurement.
When calculating x, first, the average value RefA of the reference data Ref is calculated by Expression 8.

Equation 8: RefA = (Ref0 + Ref1 +
Ref2 +... + Refn) / n Then, instead of the reference data Ref0 obtained in the first measurement, which is a reference in Expressions 4 to 7, the average value RefA of the reference data of the entire measurement is used.
Is used to calculate each corrected luminance value Lux based on Expressions 9 to 12 below.

Equation 9; Lux0 = Mes0 Equation 10; Lux1 = Mes1 / [1+ (Ref1-Re
fA) / RefA] Formula 11; Lux2 = Mes2 / [1+ (Ref2-Re
fA) / RefA] Equation 12; Luxn = Mesn / [1+ (Refn-Re
fA) / RefA] As shown in FIG. 2A, this correction method can be applied to a case where the brightness of the lamp varies even within a relatively short time and data is collected over a short time. The data sampling in this case is performed 10 times during 100 mS, for example, since 1 mS is required for the data sampling itself.

(2) Compare with the fixed reference data RefX.

When the reference data Ref has an initial value as a standard, the corrected luminance value Lux is set to a fixed value RefX by using the following Expressions 13 to 16 in the same manner as (1). Is calculated.

Equation 13; Lux0 = Mes0 / [1+ (R
ef0-RefX) / RefX] Expression 14; Lux1 = Mes1 / [1+ (Ref1-Re)
fX) / RefX] Formula 15; Lux2 = Mes2 / [1+ (Ref2-Re
fX) / RefX] Equation 16; Luxn = Mesn / [1+ (Refn-Re
fX) / RefX] This method can also be applied to the case where the brightness of the lamp varies over a relatively long period of time and data is collected over a long period of time, as shown in FIG.

In the present embodiment, the corrected luminance value is calculated and normalized by the above-described methods (1) and (2) or a combination thereof, and is stored as gamma correction target data. By calculating each correction gradation value Data which is the applied voltage-transmittance characteristic, a measurement error caused by a change in light intensity from the light source can be canceled by the data correction.

(Circuit Configuration of Data Correction Circuit) As described above, the correction of the measurement data with reference to the reference data is performed by connecting the gamma correction circuit 32 in the projector 8 in FIG. , And a data correction circuit (not shown).

FIG. 7 shows a schematic configuration of the data correction circuit and the gamma correction circuit, and data processing accompanying the above-described calculation of the corrected gradation value will be described.

The data correction circuit 23 has, for example, a subtraction circuit 22 and an operation circuit 21. The data correction circuit 23 performs any one of the above-described equations 4 to 7, 8 to 12, and 13 to 16 by: The subtraction circuit 22 and the arithmetic circuit 21 calculate the corrected luminance value Lux for each measurement. The output of the data correction circuit 23 is connected to a normalization circuit 24 that calculates a corrected gradation value Data based on the corrected luminance value Lux.

The subtraction circuit 22 outputs the measurement signal mes and the reference data Ref having the measurement data Mes input from the sensor and the reference sensor for each measurement to the gradation value measuring device 9 shown in FIG. Is a circuit to which a reference signal ref having data as the data is supplied, and which calculates a correction value by supplying these signals.

At this time, the corrected luminance value Lux is obtained by using any one of the above-described methods (1) and (2), and the reference data Ref0 or the reference data Ref0 obtained by the first measurement is obtained from the reference data Ref. Average value RefA of each reference data Ref, or
The set fixed reference data RefX is subtracted as described above.

The subtraction circuit 22 can be constituted by, for example, an operational amplifier. At this time, the (Ref1-R
ef0), (Ref1-RefA) or (Ref0-
Data such as (RefX) can be obtained by inputting an analog output from the sensor 5A to an operational amplifier and performing an analog-to-digital conversion of the differential voltage amplified by the operational amplifier.

The arithmetic circuit 21 calculates each corrected luminance value Lux based on the measured data Mes and the reference data Ref by any one of the above-described methods based on the corrected values output from the subtraction circuit 22. Is what you do.

Each corrected luminance value Lux calculated by the arithmetic circuit 21 is output to the normalization circuit 24 as a corrected gradation signal lux having the same as data, and is output from the normalization circuit 24 as described above. The correction gradation value Data is calculated by performing normalization by a suitable method.

Then, the corrected gradation values Data are stored in the first memory 17 in the gamma correction circuit 32 by writing the corrected gradation values Data. The first memory 17 can preferably be constituted by a data rewritable nonvolatile memory.

Here, an example has been shown in which the calculations of Equations 4 to 16 are performed using a subtraction circuit and a calculation circuit.
The circuit is not particularly limited to this, and any circuit may be used as long as the circuit can realize the arithmetic function.
In FIG. 7, the subtraction circuit 22 and the arithmetic circuit 2
1 is described in another block, but it is of course possible to use a single circuit having two functions. That is, using a logic circuit, a microcomputer, or the like having an arithmetic function, the above equations 4 to 7, 8 to 12, 13 to
By selecting and programming any one of the sixteen, it becomes possible to have the above-mentioned arithmetic function.

The gamma correction circuit 32 includes at least a first memory 17 for storing each corrected gradation value Data, a second memory 19 for storing an ideal γ gradation value, and each of the corrected gradation values Data. And a CPU 15 for receiving an ideal γ gradation value and calculating a gamma correction curve, and an ASIC 14 having a gamma table.

That is, the applied voltage-transmittance characteristic stored in the first memory 17 is represented by a graph shown in FIG.
The transmittance characteristics are shown in the graph of FIG.
The applied voltage-transmittance characteristic stored in the IC 14 is shown in FIG.
Each corresponds to the graph shown in (B).

As described above, since the data for correcting the applied voltage-light intensity characteristic due to the variation of the light source is written in the gamma correction circuit in the data processing circuit of the present embodiment, the data can be accurately corrected for the gamma correction. Since such correction can be performed, the reliability of the display device can be improved.

(Specific Example of Display Device) A specific example of a display device to which the above-described method for adjusting a display device of the present invention is applied will be described below. For example, the electronic device includes a display information output source 1000, a display information processing circuit 1002, and a display drive circuit 1 shown in FIG.
004, a display panel 1006 such as a liquid crystal panel, a clock generation circuit 1008, and a power supply circuit 1010. The display information output source 1000 includes a ROM, a RAM,
And the like, and a tuning circuit that tunes and outputs a television signal, and outputs display information such as an image signal based on a clock from a clock generation circuit 1008 corresponding to the timing circuit block 20 described above. .

The display information processing circuit 1002 corresponds to the data processing circuit block 30 in each of the above embodiments, and processes and outputs display information based on the clock from the clock generation circuit 1008. This display information processing circuit 1002
Can include a gamma correction circuit, a clamp circuit, and the like, in addition to the above-described amplification / polarity inversion circuit, phase expansion circuit, rotation circuit, and the like.

The drive circuit 1004 includes only the above-described scan side drive circuit 102, X driver 104 and precharge drive circuit 160, or only the X driver 104, and drives the liquid crystal panel 1006 for display. Power supply circuit 10
10 supplies power to each of the circuits described above.

As the electronic apparatus having such a configuration, a projector shown in FIG. 9, a personal computer (PC) compatible with multimedia shown in FIG. 10, and an engineering workstation (EWS) can be exemplified.

The projector shown in FIG. 9 is a projection type projector using a transmission type liquid crystal panel as a light valve, and uses, for example, a three-plate prism type optical system. Referring to FIG. 9, in a projector 1100, projection light emitted from a lamp unit 1102 of a white light source is divided into a plurality of mirrors 1106 and two dichroic mirrors 1108 by a plurality of mirrors 1108 inside a light guide 1104.
Three active matrix liquid crystal panels 1110 that are divided into three primary colors of G and B and display images of each color
The lights modulated by R, 1110G and 1110B are incident on dichroic prism 1112 from three directions.

In the dichroic prism 1112, the red R and blue B lights are bent by 90 °, and the green G
The image of each color is synthesized because the light goes straight, and a color image is projected on a screen or the like through the projection lens 1114. Here, a projection type projector has been described as an example in the figure, but the present invention is not limited to this, and the display device of the present invention can be applied to a reflection type projector and a transmission type liquid crystal display device.

The personal computer 12 shown in FIG.
00 is a main body 1204 having a keyboard 1202
And a liquid crystal display screen 1206.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, the present invention can be applied to other display devices that do not use a liquid crystal panel when fluctuation in light emission intensity becomes a problem during adjustment of the gradation of the display device.
Also, when the liquid crystal panel is used as a light valve,
The present invention is applicable to display devices other than projectors.

In the above embodiment, the TFT
Has been described as an example of a pixel switching element, but the switching element may be a two-terminal element such as an MIM. In this case, since a two-terminal element and a liquid crystal cell are connected in series between the scanning signal line and the data signal line to form a pixel, a difference voltage between the two signal lines is supplied to the pixel.

In the above embodiments, the TFT is used as the switching element, and the substrate on which the elements of the liquid crystal panel are formed is a glass or quartz substrate. However, a semiconductor substrate may be used instead.

<Embodiment 2> In the luminance adjustment method according to Embodiment 2, the measurement data is adjusted by directly measuring the leakage light of a light source in a display device such as a projector.

That is, the brightness of the light before passing through the display panel is measured by the leak light of the light source built in the projector, and the brightness of the light passing through the display panel is measured with the light projected on the projector screen. The brightness is adjusted by measuring.

FIG. 11 is a schematic diagram of a luminance measuring device of the display device according to the second embodiment. As in the first embodiment, in the luminance measurement of the display device of the second embodiment, for example, a projector, measurement is performed for each of R, G, and B.
Tone value measuring device 9, sensor 4, reference sensor 5B
Is performed by projecting an image from the projector 8 to the projector screen 6 via the lens 7.

At this time, the projector screen 6
As in the first embodiment, the light transmitting means 13
A is provided so that light from the projector 8 is directly incident on the sensor 4.

On the other hand, in order to measure the luminance of light before passing through the display panel, the reference sensor 5B is installed so that light leaked from the light source in the projector 8 is incident on the reference sensor 5B. ing. Although this installation position is not particularly shown, it is installed so that the reference sensor 5B is located closer to the light source than the display panel. For example, since the adjustment according to the present invention is performed as one of the manufacturing steps before shipment from the factory, the reference sensor 5B is set at a position closer to the light source than the display panel before the projector is assembled. However, the measurement can be performed after the projector is manufactured in a state where the reference sensor 5 </ b> B is previously installed at the position as described above. FIG. 11 illustrates the latter as an example.

As the reference sensor 5B, an apparatus having the same specifications as the sensor 4 is used, and a single clock signal is supplied to the reference sensor 5B and the sensor 4B.
At the same time.

The sensor 4 and the reference sensor 5B are connected to a tone value measuring device 9 via a cable 11A, and are used to measure data measured by the sensor 4 and reference data measured by the reference sensor 5B. Is input to the gradation value measuring device 9 for each measurement, and the correction of the measurement data and the luminance-gradation value conversion performed in the first embodiment are performed.

As in the first embodiment, the luminance of the light source is measured by changing the gradation of the light source in the projector 8 and measuring the luminance at each gradation by the sensor 4. This is performed by measuring the luminance as each reference by the reference sensor 5B.

In the luminance measurement, the light incident on the sensor 4 and the reference sensor 5B are output as electric signals to the first data bus formed by the cable 11A and input to the gradation value measuring device 9. As a result, the measurement data Mes obtained for each measurement is
The reference data Ref is supplied to the tone value measuring device 9.

Then, the reference data Ref
In the same manner as in the first embodiment, the respective measurement data Mes are corrected to calculate the corrected luminance values Lux, and by normalizing the corrected luminance values Lux, the corrected gradation values Data are calculated. The corrected gradation value Data is output to a second data bus formed by the cable 11B, and is fed back to the projector 8.

Then, the data correction circuit 23 mounted on the gradation value measuring device 9 generates the reference data Re.
f based on the correction value calculated from f.
es is corrected to calculate a corrected luminance value Lux, respectively, and then normalized to calculate a corrected gradation value Data. Further, each of the corrected gradation values Data is calculated by the gamma correction shown in FIG. By being input to the circuit 32, gamma correction is performed on the applied voltage-light intensity characteristics based on the corrected gradation value Data.

The method of extracting each corrected luminance value from each measurement data uses the same device as that of the first embodiment as the tone value measuring device in FIG. It is performed in.

Here, since the configuration of the data processing circuit is the same as that of the first embodiment, the data processing circuit shown in FIG. 5 can be used. At the time of luminance measurement, not only the measurement by the sensor 4 but also the measurement by the reference sensor 5B are performed at the same time, and the same correction as in the first embodiment is performed on each measurement data using the reference data. Therefore, the calculation for correcting the reference data and the measurement data to calculate the corrected luminance value can be performed in real time.

Therefore, according to the adjustment method of the second embodiment, the correction value is calculated for the measurement data Mes by referring to the reference data Ref, and based on the data corrected using the correction value. By performing the normalization, it is possible to have appropriate gamma correction data. The method for correcting the measurement data is also described in the first embodiment.
Applying the method of (1) or (2) described in
7, the corrected luminance value Lux can be obtained from the measurement data Mes by executing the calculations of the expressions 8 to 12 and the expressions 13 to 16.

That is, by applying this adjusting method, the adjusting method of the display device according to the second embodiment is also
Since the light intensity of the light source built in the display device fluctuates every few seconds, in the present embodiment, the measurement data is corrected based on the reference data and the measurement data measured by the reference sensor. By normalizing the subsequent data, a corrected gradation value as data to be stored in the storage unit in the display device is calculated. Needless to say, the same circuit as that of the first embodiment can be applied to the configuration of the data correction circuit in the display device. Further, the display device according to the second embodiment can be applied to the projection display device, the electronic device, and the like described in the first embodiment, as in the first embodiment.

Although the method of adjusting the display device has been described above, in consideration of the transmittance variation caused by the material of the panel, the first embodiment uses a device transmitted through the liquid crystal panel as a reference, and thus has a higher accuracy. Can be adjusted.

<Third Embodiment> In the display device, for example, as shown in a graph showing the applied voltage-gray scale characteristic after gamma correction in FIG. Then, when the black display becomes 30, the voltage amplitude between the white potential and the black potential is reduced. Therefore, in order to realize a display device with higher accuracy, it is necessary to finally adjust the voltage amplitude, and it is necessary to adjust the contrast or the dynamic range. For example, in the example of FIG. 12, the contrast ratio can be improved by making the characteristic of P like Q in order to increase the voltage amplitude.

In this contrast adjustment, by adjusting the gain of the image signal and adjusting the reference voltage in the DA converter by the following three methods, the dynamic range of black and white can be expanded to increase the contrast ratio. There are two methods as shown in (3) and (4).

(3) Adjust the bias after digital-analog conversion.

(4) Adjust the reference voltage of the DA converter.

Further, as a method of DC offset adjustment (white balance adjustment), there is a method shown in (5).

(5) For example, the black level of the clamp circuit is adjusted.

The methods (3) and (4) described above adjust the voltage amplitudes VA and VB in FIG. 18. The method (5) adjusts the voltage amplitudes VC and VD by DC level adjustment. Things. Hereinafter, the methods (3) to (5) will be individually described.

FIG. 13 is a block diagram of an adjusting device for adjusting the bias after the digital-analog conversion.

The adjusting device shown in FIG. 13 includes an operation unit 300 for inputting data for adjusting gamma correction data, and a storage unit for storing applied voltage-transmittance characteristics of each panel, for example, data rewritable. Nonvolatile third memory 302
And a CPU 304 for calculating various adjustment data based on information from the operation input unit 300 and the third memory 302. The operation input unit 30
The 0, E ² PROM 302 and CPU 304 allow such adjustments only at the time of shipment from the factory, and are therefore incorporated in adjustment equipment installed in the factory.

In the adjustment process before shipment of this device from the factory, the applied voltage-light intensity characteristics of each of the display panels 50R, 50G and 50B are measured and stored in the third memory 302, respectively. Then, a predetermined pattern is displayed on the display panel 5.
The image is displayed on 0R, 50G, 50B, and inspected by visually observing it on the panel or on a projector screen on which R, G, B are combined, for example. Furthermore,
Bias generation circuit 306 that changes the bias voltage superimposed by amplifier 40 based on a command from CPU 304
Having. The operation input unit 300 shown in FIG. 13 has a dynamic range adjustment operation unit, and the bias generation circuit 3 is sent from the CPU 300 based on the operation input or automatically.
At 06, a bias voltage change command is issued.

Here, the configuration of the amplifier 40 is shown in FIG.

FIG. 14 shows a circuit configuration of the amplifier 40 in the case of four-phase expansion where N = 4. Operational amplifiers 40A to 40D are connected to the four DA converters 38A to 38D. And four operational amplifiers 40A to 40D
The output of the bias generation circuit 306 is commonly connected to the bias input line of (1).

As described above, with the adjusting device shown in FIG. 13, after the digital-to-analog conversion, the bias can be adjusted by the operation input, the gain of the image signal can be adjusted, and the voltage amplitude can be widened. It becomes possible.

FIG. 15 shows an adjusting device for adjusting the reference voltage of the digital-to-analog converter to expand a narrow dynamic range.

In the adjusting device of FIG. 15, a reference voltage generating circuit 308 for changing the reference voltage of the DA converter 38 is provided instead of the bias generating circuit 306 of FIG. As a result, a reference voltage change command is issued to the reference voltage generation circuit 308 by the CPU 300 based on the operation input of the operation input unit 300 or automatically. Note that, also in FIG. 15, the configuration shown in FIG. 14 can be applied to the configuration of the amplifier circuit 40.

As described above, the adjustment device of FIG.
The reference voltage of the A converter can be adjusted by an operation input, and the voltage amplitude can be widened.

FIG. 16 shows an adjusting device for adjusting, for example, the black level in the clamp circuit.

The adjusting device in FIG. 16 is a clamp circuit 60 and a voltage setting circuit 61, and is a circuit provided after the DA converter in FIG.

The clamp circuit 60 outputs the image signal Vin
It has a signal line 62 to which 1 is input, and a charging capacitor 64 and a charge driving transistor 66 connected in the middle of the signal line. The clamp voltage V _CLAMP is applied to the emitter of the charging transistor 66,
Its collector is connected to the signal line 62. The clamp control signal CONT is input to the base of the charging transistor.

The image signal Vin1 is a signal that changes between a white level and a black level.
V and the black level are 2V. The control signal input to the base of the charge driving transistor 66 in the clamp circuit 60 is a vertical retrace period or a horizontal retrace period before the image signal Vin1 is input. It becomes logic "H" during input. At this time, the charging driving transistor 66 is turned on, and the clamp voltage V is applied to the charging capacitor 64.
_CLAMP is charged. Thereafter, the control signal C
ONT becomes logic "L", and the charging transistor 66 is turned off. Thereafter, when the image signal Vin1 is input, it is clamped to the black level clamp voltage V _CLAMP .

The image signal Vin2 output from the clamp circuit 60 has a clamp voltage V _CLAMP of, for example, 1.2.
V, the black level is lower than the image signal Vin1, but the amplitude between the black level and the white level is the same, for example, 3V.

As described above, the adjusting device shown in FIG. 16 can set the clamp voltage of the clamp circuit to the black level, and can change the white level accordingly, so that this adjustment can be made for each of R, G, and B. By executing the process on the panel, white balance adjustment is performed.

Although the contrast adjustment and the white balance adjustment have been described above, these methods are performed after the adjustment according to the first or second embodiment. According to this adjustment method, the image quality of the display device is further reduced. Can be improved.

<Embodiment 4> FIG. 20 is a block diagram showing a configuration of a main part for obtaining the display pattern shown in FIG. 1B. Among the circuits shown in FIG.
To 38D, amplifiers 40A to 40D and bias generation circuit 306 are the same as those in FIG. 20, the adjustment voltage generation circuit 310, the reference potential 312,
A switch 314 and a switching signal generation circuit 316 are provided.

The operation of the circuit of FIG. 20 is described in FIG.
This will be described with reference to FIG. DAC38A-3 of FIG.
From 8D, pixel data corresponding to the display pattern shown in FIG. 21A is output. The difference between the display pattern of FIG. 21A and the display pattern at the time of measurement shown in FIG. 1B is that the area corresponding to the opening 13A has the same black display as the surrounding mask area 13C. .

Here, the reference potential 312 is set to the switch 314
2 is supplied to the bias generation circuit 306 through
The display pattern shown in FIG. 1A is projected on the projector screen 6. However, in this state, it is not possible to display a different gradation value in the area of the opening 13A for each measurement.

Therefore, only when the display is performed in the area corresponding to the opening 13A, the switch 314 is switched.
The potential from the adjustment voltage generation circuit 310 is supplied to the bias generation circuit 306 via the switch 314. From the adjustment voltage generation circuit 310, different potentials are generated in the region of the opening 13A corresponding to different gradation values for each measurement. As described above, only when the pixel data corresponding to the area of the opening 13A is amplified by the amplifiers 40A to 40D, D
The black display data output from the ACs 38A to 38D are amplified by the amplifiers 40A to 40D so as to have different gradation values for each measurement.
Amplified at 40D. In this way, the pixel data supplied to the liquid crystal panel at the time of measurement can be changed in the gradation value only in the area of the opening 13A while fixing the pixel data in the fixed pattern shown in FIG.

Since the switch 314 is switched only when the display is performed in the area corresponding to the opening 13A, the switching signal generation circuit 316 generates a switching signal as shown in FIG.

[0160]

[Brief description of the drawings]

FIG. 1A is a schematic diagram of a luminance measuring device for measuring an applied voltage-light intensity characteristic according to a first embodiment in which the present invention is applied to a projector, and FIG. FIG. 1A is a front view of the screen shown in FIG. 1A, and FIG. 1C is a cross-sectional view of the screen.

FIGS. 2A and 2B are graphs showing a relationship between time and luminance of two types of light sources applied to a projector, respectively.

FIG. 3 is a block diagram of the entire display device in which the present invention is applied to a projector.

FIGS. 4A and 4B respectively show light intensity measurement data obtained by measuring the luminance of a light source built in the projector for each of 32 gradations based on reference data by the adjustment method according to the present invention. It is a data characteristic diagram and a graph which are an example in which the corrected luminance values obtained by the correction were respectively normalized and represented.

FIG. 5 is a graph showing a relationship between a luminance variation of a light source and an applied voltage-light intensity characteristic of a projector.

FIG. 6 shows measurement data Mes and reference data Re.
FIG. 14 is a characteristic diagram illustrating a numerical example of a corrected luminance value Lux corrected based on f.

FIG. 7 is a block diagram schematically illustrating circuit functions of a data correction circuit and a gamma correction circuit.

FIG. 8 is a schematic diagram of an electronic device to which the present invention is applied.

FIG. 9 is a schematic diagram of a projector to which the present invention is applied.

FIG. 10 is a schematic diagram of a personal computer (PC) to which the present invention is applied.

FIG. 11 is a schematic diagram of a luminance measuring device for measuring an applied voltage-light intensity characteristic according to a second embodiment in which the invention is applied to a projector.

FIG. 12 is an example of a graph showing applied voltage-light intensity characteristics after gamma correction.

FIG. 13 is a block diagram illustrating an adjustment device that performs bias adjustment after digital-analog conversion.

FIG. 14 is a block diagram showing a circuit configuration of an amplifier in the case of four-phase expansion.

FIG. 15 is a block diagram showing an adjusting device for adjusting a reference voltage of the DA converter to expand a narrow dynamic range.

FIG. 16 is a block diagram showing an adjusting device for adjusting, for example, a black level of the clamp.

FIG. 17 is a graph showing a relationship between a voltage V (a positive voltage (+) and a negative voltage (-)), a difference voltage between a counter substrate voltage, and transmittance.

FIG. 18 is a graph showing a change in signal voltage when the voltage applied to the liquid crystal is inverted for driving.

19A is a graph showing measured applied voltage-transmittance characteristics specific to a liquid crystal panel, and FIG. 19B is a graph showing correction data required to correct the applied voltage-transmittance characteristics specific to a panel. FIG. 19C is a graph showing the applied voltage-transmittance characteristics after gamma correction.

FIG. 20 shows a circuit capable of displaying pixel data of a constant gradation at each measurement, and displaying only a region of an opening 13A in the display pattern shown in FIG. FIG.

21A is a diagram showing a display pattern based on pixel data of a constant gradation supplied at each measurement, and FIG. 21B is a diagram obtained by switching a switch in FIG. 20; It is a figure showing the same display pattern as 1 (B).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Common voltage 2 Positive side image signal 3 Negative side image signal 4 Sensor 5A, 5B Reference sensor 6 Projector screen 7 Lens 8 Projector 9 Tone value measuring instrument 10 Signal processing board 11A, 11B Cable 12, 14 Input terminal 13A, 13B Light transmitting means (opening) 14 ASIC 16 AD converter 17 First memory 18 Digital decoder 19 Second memory 20 Frame memory 21 Operation circuit 22 Subtraction circuit 23 Data correction circuit 24 Normalization circuit 30R, 30G, 30B Liquid crystal Display-only board 32 Gamma correction circuit 34 Phase expansion circuit 36 Polarity inversion circuit 38, 38A to 38D DA converter 40, 40A to 40D amplifier 42 Buffer 50R, 50G, 50B Liquid crystal display panel 60 Clamp circuit 61 Voltage setting circuit 6 Signal lines 64 charging capacitor 66 charging the driving transistor 300 operation input unit 15,304 CPU 302 third memory 306 bias generating circuit 308 reference voltage generation circuit 310 adjusts the voltage generating circuit 312 a reference potential 314 switch 316 switch signal generating circuit

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 5/66 H04N 5/66 A 5/74 5/74 D

Claims (15)

[Claims] 1. A method for adjusting a display device having a light source and an optical modulation element for modulating light from the light source based on the applied voltage, wherein the applied voltage is changed and set in correspondence with different gradation values. A first step of measuring the light intensity modulated by the optical modulation element corresponding to at least one pixel, and an application corresponding to a gradation value that is always constant at each measurement in the first step. A second step of setting to a voltage and measuring a reference light intensity modulated by the optical modulation element corresponding to a pixel at a reference position different from the at least one pixel, and measuring in the second step A third step of correcting the light intensity for each gradation measured in the first step based on the obtained reference light intensity. 2. The method for adjusting a display device according to claim 1, wherein in the second step, measurement is performed by setting the applied voltage corresponding to a maximum gradation value. 3. The display device according to claim 2, wherein the display device includes a plurality of types of optical modulation elements, and the measurement is performed for each of the optical modulation elements. Adjustment method. 4. A method for adjusting a display device having a light source and an optical modulation element for modulating light from the light source based on the applied voltage, wherein the applied voltage is changed and set in correspondence with different gradation values. A first step of measuring the light intensity modulated by the optical modulation element corresponding to at least one pixel, and for each measurement in the first step, the light intensity from the light source is used as a reference. A second step of measuring; and a third step of correcting the light intensity of each gradation measured in the first step based on the reference light intensity measured in the second step. A method for adjusting a display device, the method comprising: 5. The method for adjusting a display device according to claim 4, wherein in the second step, light from the light source is measured using a reference light measuring unit disposed inside the display device. . 6. The method according to claim 1, wherein, in the third step, the reference light intensity measured in the first measurement and the reference light obtained in each measurement after the first measurement. A method for adjusting a display device, comprising calculating respective correction values by comparing respective intensities. 7. The method according to claim 1, wherein, in the third step, an average value of the reference light intensity measured for each measurement and each reference light intensity obtained in each measurement. A method for adjusting a display device, comprising calculating respective correction values by comparing respective intensities. 8. The method according to claim 1, wherein, in the third step, an initial value of a standardized light intensity and a reference light intensity obtained in each measurement are defined. A method for adjusting a display device, wherein each correction value is calculated by comparing the respective values. 9. The method according to claim 1, wherein the third step includes a step of converting the corrected light intensity into a gradation value. 10. The method according to claim 9, further comprising a step of determining a gamma correction characteristic based on each correction value obtained in the third step. . 11. The digital image data according to claim 10, wherein the input digital data is corrected by a gamma correction circuit in which the gamma correction characteristic is set, and the applied voltage-optical modulation characteristic of the optical modulation element is adjusted. Converting the digital image data into analog image data with a DA converter; amplifying the analog image data with an amplifier; and performing the optical operation based on the amplified analog image data. A step of modulating and driving the modulation element to display an image, wherein the gradation value of the input digital image data to the gamma correction circuit is maximum, and the gradation value of the output digital image data from the gamma correction circuit is Adjusting the amplification factor of the amplifier when the value is smaller than the maximum value to extend the dynamic range of the displayed image. Adjustment method for a display device according to claim. 12. The amplifier according to claim 11, wherein the amplifier is configured by an operational amplifier,
In the adjusting step, the amplifier changes a bias potential supplied to the operational amplifier. 13. The digital image data according to claim 10, wherein the digital data is corrected by a gamma correction circuit in which the gamma correction characteristic is set, and the applied voltage-optical modulation characteristic in the optical modulation element is applied. A step of converting the digital image data corrected by the gamma correction circuit into analog image data by a DA converter based on a reference voltage; and a step of amplifying the analog image data by an amplifier. And a step of modulating and driving the optical modulation element based on the analog image data to display an image; and wherein the tone value of digital image data input to the gamma correction circuit is maximum, and the gamma correction circuit When the gradation value of the output digital image data from the device is smaller than the maximum value, the reference voltage of the DA converter is changed to Adjustment method of a display device, comprising: the adjusting step to expand the dynamic range, the. 14. The digital image data according to claim 10, wherein the input digital data is corrected by a gamma correction circuit in which the gamma correction characteristic is set, and the applied voltage-optical modulation characteristic of the optical modulation element is adjusted. And converting the digital image data corrected by the gamma correction circuit into analog image data with a DA converter based on a reference voltage. Setting a corresponding voltage to a predetermined clamp voltage in a clamp circuit, modulating the optical modulation element based on the analog image data to display an image, and setting a clamp voltage in the clamp circuit. Adjusting the DC offset amount of the analog image data with respect to the reference voltage to adjust the white balance. A method for adjusting a display device, comprising: 15. The display device according to claim 1, wherein the display device is a projection display device, wherein the measurement in the first step is performed on a pixel on a screen, and the second step is performed. Wherein the measurement is performed on a pixel at the reference position on the screen.