JP2008233379A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct-vision type liquid crystal display device, wherein intensities of external light of a display unit are precisely detected in each of predetermined regions and excellent display is performed based upon detection results irrelevantly to the irradiation state of the external light. <P>SOLUTION: Optical sensors 20 are provided in each of predetermined regions (for example, for each of pixel formation portions) of the display unit of the matrix type liquid crystal display device, and an image correcting unit 50 corrects (for example, gamma correction) a data signal DAT supplied to a display control unit 200 from outside based upon detected values of external light intensities in each of the predetermined regions obtained by those optical sensors 20 so that a contrast decrease of display depending upon the external light is compensated. A data signal line driving circuit (not shown) drives the display unit 100 based upon the image signal having been corrected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device configured to suppress deterioration in display quality due to external light.

  At present, liquid crystal display devices using thin film transistors (TFTs) are widely used as display devices for television receivers, computers, mobile phones and the like. This liquid crystal display device is often used not only indoors but also outdoors, and the influence of external light on display quality may be a problem. That is, when used in an environment where there is a large amount of external light such as outdoors, there is a problem that the contrast in the display of the liquid crystal display device is lowered and the display quality is impaired.

  On the other hand, in a display device such as a liquid crystal display device, an external light amount (intensity of external light) is detected by an optical sensor, and the brightness of the display unit is adjusted according to the detection result, thereby adjusting the contrast of the display unit to external light. However, there is known a technique of maintaining a constant value regardless of the above (for example, Patent Documents 1 to 5).

FIG. 9 is a block diagram showing a schematic configuration of such a conventional liquid crystal display device (hereinafter referred to as “conventional example”). In this conventional example, the optical sensor 20 is provided in the vicinity of the display unit in the liquid crystal display device. Based on the detection result of the external light intensity by the optical sensor 20, the data signal DAT representing the image to be displayed is the correction unit 90. It is corrected by.
JP 2004-272156 A JP 2001-134235 A JP 2006-285063 A JP 2005-122187 A JP 2006-30318 A Japanese Patent Laid-Open No. 7-182959 JP-A-7-162790

  However, the amount of external light may vary depending on the area of the display unit, such as when external light is applied to a part of the display unit such as a liquid crystal panel. In such a case, the above conventional technique cannot always provide a good display. For example, as shown in FIG. 10A, in the display unit 100 of the conventional example, the contrast of the display image is greatly reduced because the intensity of the external light is high in a part of the area A1, and the external area A2 is outside. Since the intensity of light is relatively weak, the degree of decrease in the contrast of the display image is small, and in the other area A3, the contrast of the display image may not be decreased because little external light is received. In this case, as shown in FIG. 9, the optical sensor 20 is in a position that hardly receives external light, and the correction (image correction) of the data signal DAT based on the detection of the external light intensity is not substantially performed. Accordingly, as shown in FIG. 10B, a decrease in contrast due to external light in the regions A1 and A2 in the display unit 100 is not eliminated.

  On the other hand, Patent Document 6 discloses a measuring unit (specifically, a plurality of optical sensors arranged on the outer peripheral portion of the light-emitting panel) for measuring the luminance of each of a plurality of different areas on the display screen, and a measuring unit. There is disclosed an image display apparatus that includes a correction unit that corrects an input signal corresponding to a region having a high luminance measured by the method to display at a higher luminance and prevents a decrease in contrast due to external light. Further, in Patent Document 7, a plurality of optical sensors are arranged in a screen, the distribution state of external light is measured based on the projected image characteristic detection signal, and the luminance is determined based on the distribution state of the external light. A projection display device that adjusts the distribution of the image is disclosed.

  However, in the image display device described in Patent Document 6, since the optical sensor is disposed on the outer peripheral portion of the light-emitting panel, the amount of external light in each area of the display unit may not be measured sufficiently accurately and may be obtained. There is a limit to the accuracy of the light intensity distribution. Further, the display device described in Patent Document 7 is a projection type, and a plurality of optical sensors are arranged on the screen, and this configuration is directly applied to a direct-view type display device such as a normal liquid crystal display device. Can not do it.

  Accordingly, the present invention provides a direct-view type liquid crystal display device that can accurately detect the external light intensity in a display unit for each predetermined region and can perform good display regardless of the external light irradiation state based on the detection result. With the goal.

The first invention corresponds to a plurality of data signal lines, a plurality of scanning signal lines intersecting with the plurality of data signal lines, and intersections of the plurality of data signal lines and the plurality of scanning signal lines, respectively. A liquid crystal display device having a display unit including a plurality of pixel forming units arranged in a matrix, and displaying an image on the display unit based on an input signal given from the outside,
A data signal line driving circuit for generating a plurality of data signals representing an image to be displayed on the display unit based on the input signal and applying the data signals to the plurality of data signal lines;
A scanning signal line driving circuit for selectively driving the plurality of scanning signal lines;
An external light detection unit that includes a plurality of optical sensors disposed in the display unit, and detects the intensity of external light in the display unit for each predetermined region;
An image correction unit that corrects an image to be displayed on the display unit according to a distribution in the display unit of the intensity of the external light based on a detection result by the external light detection unit.

According to a second invention, in the first invention,
The image correction unit corrects the plurality of data signals based on the detection result of the external light detection unit, thereby compensating for a decrease in contrast of an image displayed on the display unit due to external light for each predetermined region. Thus, the image to be displayed on the display unit is corrected.

According to a third invention, in the second invention,
The image correction unit
A plurality of gamma correction tables prepared in advance as a table for correcting the value indicated by the input signal so that the relationship between the input signal and the luminance of the pixel formed by the pixel forming unit is changed;
By selecting one gamma correction table from the plurality of gamma correction tables based on the detection result by the external light detection unit, and correcting the value indicated by the input signal based on the selected gamma correction table, And a correction processing unit that corrects the plurality of data signals so that a decrease due to external light is compensated for each predetermined region.

According to a fourth invention, in the first invention,
The plurality of photosensors are arranged in a matrix in the display unit,
The outside light detector is
Photodetection scanning signal lines disposed along each row of the matrix of photosensors;
A photodetection data signal line disposed along each column of the matrix of photosensors;
A photodetection scanning signal line driving circuit for selectively driving the photodetection scanning signal line so that a selection period of the photodetection scanning signal line does not overlap any of the selection periods of the plurality of scanning signal lines;
When any one of the light detection scanning signal lines is selected, an external light intensity detected value by an optical sensor arranged along the selected light detection scanning signal line is used as the light detection data signal. A level detection unit that acquires via a line,
The light detection scanning signal line is arranged in parallel with the plurality of scanning signal lines,
The data signal line for photodetection is shared with the data signal line.

A fifth invention is the fourth invention,
The light detection scanning signal line corresponds to each of the plurality of scanning signal lines,
The scanning signal line driving circuit for light detection has a detection value of an external light intensity detected by a photosensor in a row corresponding to the scanning signal line to be selected before each scanning signal line is selected within each frame period. Select each light detection scanning signal line to be acquired by the level detection unit,
The image correction unit corrects the plurality of data signals to be applied to the plurality of data signal lines based on the detected value of the external light intensity when the scanning signal line to be selected is selected. Thus, the image to be displayed on the display unit is corrected.

According to a sixth invention, in the fourth invention,
The plurality of photosensors, photodetection scanning signal lines, and photodetection data signal lines are integrally formed on a substrate on which circuits constituting the plurality of pixel forming portions are formed. And

  According to the first aspect, the intensity of the external light in the display unit is detected for each predetermined area, and the image to be displayed on the display unit is based on the detection result according to the distribution of the external light intensity in the display unit. It is corrected. Thereby, even if the external light intensity varies depending on the position on the display unit, an image in which the original display quality is substantially maintained is visually recognized on the entire screen. In other words, in a direct-view type liquid crystal display device, good display can be performed regardless of the external light irradiation state on the display unit.

  According to the second aspect of the invention, the plurality of data signals are corrected so that a decrease in contrast of the image displayed on the display unit due to external light is compensated for each predetermined region. Even if the light intensity is different, an image in which the original contrast is substantially maintained is visually recognized on the entire screen.

  According to the third aspect of the invention, the display image is corrected by correcting the value indicated by the input signal based on the gamma correction table selected from the plurality of gamma correction tables prepared in advance based on the detection result by the external light detection unit. The decrease in contrast due to external light is compensated for each predetermined region. As a result, even if the external light intensity varies depending on the position on the display unit, an image in which the original contrast is substantially maintained is visually recognized on the entire screen.

  According to the fourth aspect of the invention, the detected value of the external light intensity by a large number of optical sensors arranged in a matrix in the display unit is detected by the level detection unit via the data signal line based on the scanning by the scanning signal for light detection. Therefore, the distribution of the external light intensity in the display unit can be accurately detected (with high spatial resolution) while suppressing the complexity of the configuration of the display unit.

  According to the fifth aspect of the present invention, before each scanning signal line is selected within each frame period, the detected value of the external light intensity by the photosensor in the row corresponding to the scanning signal line to be selected is acquired. The data signal to be applied to each data signal line when the scanning signal line to be selected is selected is corrected based on the detected value of the external light intensity. As a result, the detection of the external light intensity and the image correction based on the detection can be sequentially performed for each display line, so that an increase in circuit amount due to the detection and correction of the external light intensity in units of pixels can be suppressed.

  According to the sixth aspect of the invention, each photosensor, each photodetection scanning signal line, and each photodetection data signal line is integrally formed on a substrate on which a circuit constituting each pixel forming portion is formed. Since it is formed, it is possible to suppress an increase in manufacturing cost due to the realization of the function of detecting the external light intensity in the display unit for each predetermined region.

<1. Summary of the present invention>
Before describing the embodiments of the present invention, first, the outline of the present invention will be described in comparison with a conventional example.

  FIG. 1 is a schematic block diagram for explaining the basic configuration and features of a liquid crystal display device according to the present invention. In the present invention, the display unit 100 of the liquid crystal display device is provided with the optical sensor 20 for each predetermined region, and the intensity of the external light applied to the display unit 100 can be detected for each predetermined region. . Here, the optical sensor 20 is provided in each of n × m regions obtained by dividing the vertical direction (vertical direction) of the display unit 100 into n pieces and dividing the horizontal direction (horizontal direction) into m pieces. It has been. That is, n × m photosensors 20 are arranged in a matrix in the display unit 100.

  The display unit 100 corresponds to a liquid crystal panel, and includes a plurality of data signal lines (also referred to as “source lines”) and a plurality of scanning signal lines (also referred to as “gate lines”) intersecting with the plurality of data signal lines. And a plurality of pixel forming portions arranged in a matrix corresponding to the intersections of the plurality of data signal lines and the plurality of scanning signal lines. A configuration may be considered in which one photosensor 20 is provided for each pixel formation portion, and the photosensor 20 is provided for each region corresponding to one pixel in the display unit 100. In this configuration, the number of data signal lines is equal to m, and the number of scanning signal lines is equal to n. In FIG. 1, a data signal line driving circuit (also called “data driver” or “source driver”) (not shown) for driving the plurality of data signal lines and the plurality of scanning signal lines are driven. A scanning signal line driving circuit (also referred to as “gate driver”) (not shown) is formed integrally with the display unit 100 as a liquid crystal panel. However, in the present invention, the liquid crystal panel as the display unit 100 may be separated from the data signal line driving circuit and the scanning signal line driving circuit.

  The liquid crystal display device illustrated in FIG. 1 includes a display control unit 200 and an image correction unit 50 in addition to the display unit 100 described above. In this configuration, a data signal DAT representing an image to be displayed is externally supplied to the display control unit 200 as an input signal, and is obtained by the optical sensor 20 in each region (m × n regions) of the display unit 100. A detection value indicating the external light intensity is input to the image correction unit 50. The image correction unit 50 corrects the data signal DAT from the outside or an image signal corresponding to the data signal DAT based on the detected value of the external light intensity. In this correction, the data signal DAT and the like are corrected for each region so as to compensate for a decrease in display contrast (contrast of an image displayed on the display unit 100) due to external light irradiation on the display unit 100. That is, when one optical sensor 20 is provided for each pixel formation portion in the display unit 100, the data signal DAT is corrected based on the detected value of the external light intensity in units of pixels. However, the data signal DAT may be corrected for each predetermined number of adjacent regions based on the average value of detection values obtained by the optical sensors in the predetermined number of adjacent regions.

  According to the above configuration, the plurality of data signals applied to the plurality of data signal lines in the display unit 100 from the data signal line driving circuit (not shown) are corrected, thereby displaying the data. The reduction in display contrast is compensated according to the external light intensity in each area of the unit 100.

  By the way, since the gamma characteristic indicating the relationship between the gradation value indicated by the data signal DAT given from the outside and the luminance displayed on the display unit 100 differs depending on the display device, the input is performed so that the image is reproduced as a display image satisfactorily. A correction called gamma correction is applied to the data signal DAT as a signal. As described above, the correction by the image correction unit 50 corrects the contrast in accordance with the external light intensity in the display unit 100 in order to prevent a decrease in the image displayed on the display unit 100 due to the external light. (Contrast correction 52) By changing the content of this gamma correction based on the detected value of the external light intensity (gamma correction 54), it is possible to prevent a decrease in display contrast due to external light (in the embodiments described later, external contrast is reduced). The content of the gamma correction is changed based on the detected value of the external light intensity so that the decrease in display contrast due to light is compensated).

  Now, as shown in FIG. 2A, the intensity of external light is high in some areas A1 of the display unit 100, the intensity of external light is relatively low in the surrounding area A2, and the other areas A3. Now consider the case where there is little external light. In this case, if the image correction based on the detection of outside light is not performed, the contrast of the display image on the display unit 100 is greatly reduced in the region A1, the degree of reduction is small in the region A2, and is not reduced in the region A3.

  As described above, in the liquid crystal display device (FIG. 1) according to the present invention, the external light intensity is detected for each region of the display unit 100, and the data signal DAT is corrected based on the detection result, thereby displaying the display. The reduction in display contrast is compensated according to the external light intensity in each area of the unit 100. Therefore, in the above-described case shown in FIG. 2A, according to the configuration of the present invention, the data signal is corrected so as to greatly increase the contrast for the image to be displayed in the area A1 where the external light intensity is high. (Strong image correction) For the image to be displayed in the area A2 where the external light intensity is low, the data signal is corrected so as to slightly increase the contrast (weak image correction), and the area A3 that hardly receives external light is to be displayed Does not correct the corresponding data signal (no image correction). As a result, even if the external light intensity varies depending on the position on the display unit 100, the observer can visually recognize an image in which the original contrast is substantially maintained as shown in FIG.

<2. First Embodiment>
<2.1 Overall configuration>
FIG. 3 is a block diagram showing the overall configuration of the liquid crystal display device according to the first embodiment of the present invention. The liquid crystal display device includes a display unit 100 that provides a display screen, a display control circuit 200, a data signal line driving circuit 300, a scanning signal line driving circuit 400, and a light detection scanning signal line driving circuit 420. ing. The display unit 100 includes a plurality of data signal lines SL (1) to SL (m), a plurality of scanning signal lines GL (1) to GL (n), and the plurality of data signal lines SL (1). Includes a plurality (m × n) of pixel forming portions provided corresponding to the intersections of .about.SL (m) and the plurality of scanning signal lines GL (1) to GL (n). Each pixel forming portion is a switching element having a gate electrode connected to the scanning signal line GL (i) passing through the corresponding intersection and a source electrode connected to the data signal line SL (j) passing through the intersection. A thin film transistor (TFT), a pixel electrode connected to the drain electrode of the TFT, a common electrode provided in common to the plurality of pixel formation portions, and a common electrode provided in the plurality of pixel formation portions. The liquid crystal layer is sandwiched between the pixel electrode and the common electrode. In each pixel formation portion, a pixel capacitance is formed by a pixel electrode and a common electrode facing the pixel electrode with a liquid crystal layer interposed therebetween. When an active signal is applied to the scanning signal line GL (i) that passes through the corresponding intersection, each pixel forming unit turns on the TFT inside thereof, and the data signal line SL (j that passes through the corresponding intersection. ) The internal pixel capacitor is charged by the above signal.

  In the display unit 100 according to the present embodiment, the scanning signal lines HL (i) for light detection are arranged in parallel to the scanning signal lines SL (i) (i = 1, 2,..., N), A plurality (m × n) corresponding to the intersections of the plurality of data signal lines SL (1) to SL (m) and the plurality of light detection scanning signal lines HL (1) to HL (n), respectively. Optical sensors are provided (details will be described later).

  The display control circuit 200 receives a data signal DAT and a timing control signal TS given from the outside, receives a digital image signal DV, a data start pulse signal SSP for controlling the timing for displaying an image on the display unit 100, a data clock. A signal SCK, a latch strobe signal LS, a gate start pulse signal GSP, a gate clock signal GCK, and a light detection start pulse signal HSP for controlling the timing of reading the detected value of the external light intensity from the light sensor in the display unit 100. Output. The data clock signal SCK is a clock signal including a pulse corresponding to each pixel of the image represented by the digital image signal DV, and the data start pulse signal SSP is a signal including one pulse at the beginning of each horizontal scanning period. The latch strobe signal LS is a signal including one pulse for each horizontal scanning period. The gate clock signal GCK is a clock signal having a period of one horizontal scanning period, and the gate start pulse GSP is a signal including one pulse at the beginning of each vertical scanning period (each frame period). The detection start pulse signal HSP is a signal having a pulse that appears approximately one horizontal period earlier than the pulse of the gate start pulse signal GSP. The timing signal TS given from the outside includes a horizontal synchronizing signal HSY and a vertical synchronizing signal VSY corresponding to the digital image signal DV, and the data start pulse signal SSP and the gate clock signal GCK are based on the horizontal synchronizing signal HSY. The gate start pulse signal GSP and the light detection start pulse signal HSP are generated based on the vertical synchronization signal VSY.

  The data signal line driving circuit 300 receives the digital image signal DV, the data start pulse signal SSP, the data clock signal SCK, and the latch strobe signal LS output from the display control circuit 200, and receives the pixel formation unit in the display unit 100. Data signals S (1) to S (m) are applied to the data signal lines SL (1) to SL (m), respectively, in order to charge the pixel capacitors. At this time, the digital image signal DV indicating the voltage to be applied to each of the data signal lines SL (1) to SL (m) is sequentially supplied to the data signal line driving circuit 300 at the timing when the pulse of the data clock signal SCK is generated. Is input. The data signal line driver circuit 300 has a built-in shift register, and the data start pulse signal SSP is sequentially transferred to the shift register based on the data clock signal GCK. According to this transfer, m sampling pulses are sequentially output in the cycle of the data clock signal SCK. Based on these m sampling signals, the digital image signal DV indicating the voltage to be applied to each of the data signal lines SL (1) to SL (m) is sequentially held in the data signal line driving circuit 300. At the timing when the pulse of the latch strobe signal LS is generated, the held digital image signal DV is converted into an analog voltage, and all the data signal lines SL (1) are converted into data signals S (1) to S (m). To SL (m) simultaneously. That is, in this embodiment, a line sequential driving method is adopted.

  Based on the gate start pulse signal GSP and the gate clock signal GCK output from the display control circuit 200, the scanning signal line driving circuit 400 generates active scanning signals (pixels) on the scanning signal lines GL (1) to GL (n). A voltage for turning on the TFT in the formation portion is sequentially applied.

  As described above, in the display unit 100, the data signals S (1) to S (m) are applied to the data signal lines SL (1) to SL (m), respectively, and the scanning signal lines GL (1) to GL are applied. Scan signals G (1) to G (n) are respectively applied to (n). A predetermined potential Vcom is applied to the common electrode by a common electrode driving circuit (not shown). As a result, a voltage corresponding to a pixel value based on the digital image signal DV is given to each pixel electrode with reference to the potential Vcom of the common electrode, and the voltage is held in the pixel capacitance. Thereby, a voltage corresponding to the potential difference between each pixel electrode and the common electrode is applied to the liquid crystal layer of the display unit 100, and the display unit 100 controls the light transmittance of the liquid crystal layer by this applied voltage, An image represented by the digital image signal DV is displayed.

  On the other hand, the light detection scanning signal line drive circuit 420 is based on the light detection start pulse signal HSP and the gate clock signal GCK output from the display control circuit 200, and the light detection scanning signal lines HL (1) to HL. Active scan signals are sequentially applied to (n). Since the light detection start pulse signal HSP is a signal having a phase advanced by about one horizontal period from the gate start pulse signal GSP, an active scanning signal G (i) is applied to each scanning signal line GL (i). The active scanning signal H (i) is applied to the light detection scanning signal line HL (i) at a timing that is approximately one horizontal period earlier than the applied timing. However, each scanning signal G (i) (i = 1 to n) output from the scanning signal line driving circuit 400 is active during any horizontal scanning period (except for the blanking period) and is not active during the blanking period. On the other hand, each scanning signal H (i) (i = 1 to n) output from the scanning signal line driving circuit 420 for light detection becomes active in any (horizontal) blanking period, and the horizontal scanning period (returning). Inactive (except for line period).

  Therefore, in the kth horizontal scanning period (hereinafter, also referred to as “kth display period”), the active scanning signal G (k) is applied to the kth scanning signal line GL (k), and the kth display period. In the blanking period immediately after that, the active scanning signal H (k + 1) is applied to the k + 1th light detection scanning signal line HL (k + 1) (k = 1, 2,..., N−1). By sequentially selecting the light detection scanning signal line HL (k + 1) by the application of the scanning signal H (k + 1), a detection value indicating the external light intensity detected by each optical sensor in the display unit 100 is acquired. By correcting the digital image signal DV based on the detected value, the data signals S (1) to S (m) used for charging the pixel capacitance in the (k + 1) th horizontal scanning period (k + 1 display period). It is corrected (details will be described later).

<2.2 External light detection and image correction>
Next, external light detection and image correction in the present embodiment will be described with reference to FIGS. FIG. 4 is a block diagram illustrating a configuration for detecting external light and correcting an image in the present embodiment. As described above, the display unit 100 according to the present embodiment is provided with the optical sensor 20 corresponding to each intersection of the scanning signal line for light detection HL (i) and the data signal line SL (j). (I = 1, 2,..., N; j = 1, 2,..., M). Each optical sensor 20 includes a photoelectric conversion element such as a photodiode or a phototransistor, a capacitor, and a TFT as a switching element, and the capacitor (hereinafter referred to as “hereinafter referred to as“ capacitor ”) immediately before the start of each horizontal scanning period by a power supply line (not shown). Detection capacitor) is discharged to a predetermined potential, and at the end of each horizontal scanning period due to the photocurrent generated by the photoelectric conversion element, the charging voltage and the accumulated charge amount of the detection capacitor are set according to the external light intensity. It has become. The photodetection scanning signal line HL (k) corresponding to the kth display line (which is a display area corresponding to the kth scanning signal line GL (k), hereinafter also referred to as “kth display line”) is In the blanking period immediately after the k-1st horizontal scanning period (k-1 display period), the selected state is established (k = 2, 3,..., n). At this time, in each photosensor 20 in the region of the kth display line, the TFT as the switching element is turned on, and one end of the detection capacitor inside thereof is connected to the data signal line SL (j) passing through the corresponding intersection. It is electrically connected through the TFT (assuming that the other end of the detection capacitor is given a fixed potential such as a ground potential).

  Accordingly, as shown in FIG. 5, in the k−1 display period, the pixel capacity of each pixel formation unit corresponding to the k−1 display line is charged by the corresponding data signal S (j) (pixel writing). In addition, the detection capacitors of the optical sensor 20 in all display line regions including the kth display line are charged according to the external light intensity (external light sensing). Then, one end of the detection capacitor of the optical sensor 20 in the region of the kth display line is electrically connected to the data signal lines SL (1) to SL (m) in the blanking period immediately after the k−1th display period. Therefore, the accumulated charge amount of the detection capacitor in the region of the kth display line can be detected via the data signal lines SL (1) to SL (m). Various well-known configurations can be adopted as the specific configuration of the photosensors arranged in a matrix and the reading unit of the detection values (a level detection unit 304 described later in the present embodiment) (for example, JP-A-2001-292276, JP-A-2007-11233, JP-A-2005-122187 (reference 4), etc.).

  As shown in FIG. 4, the data signal line drive circuit 300 in this embodiment includes a level detection unit 304 and a correction unit 350 in addition to the signal line drive unit 302 having the same function as the conventional data signal line drive circuit. I have. The data signal lines SL (1) to SL (m) are connected not only to the signal line driver 302 but also to the level detector 304. In these data signal lines SL (j), as described above, the voltage indicating the external light intensity in the region of the kth display line and the accumulated charge are held in the blanking period immediately after the k−1th display period. One ends of m detection capacitors (within the optical sensor 20) are electrically connected to each other. The level detection unit 304 detects the accumulated charge amount of these detection capacitors via these data signal lines SL (1) to SL (m), and based on the detection result, the level detection unit 304 detects the external charge in the region of the kth display line. M detection values Lex are generated as light intensity detection values. These m detection values Lex are given to the correction unit 350. As can be seen from the above description, in this embodiment, the photodetection scanning signal line drive circuit 420, the photodetection scan signal lines HL (1) to HL (n), the n × m photosensors 20, and the data The signal lines SL (1) to SL (m) and the level detection unit 304 constitute an external light detection unit that detects external light intensity in the display unit 100 for each pixel formation unit.

  As illustrated in FIG. 6, the correction unit 350 includes a gamma correction processing unit 352 and a correction storage unit 354 that stores R correction tables Tm1 to TmR. Here, the external light intensity that can be indicated by the detection value Lex from the level detection unit 304 is divided into R levels, and these R levels correspond to the R correction tables Tm1 to TmR, respectively. Each correction table Tmk (k = 1 to R) is a table for gamma correction, and an image can be displayed with an original contrast by suppressing a decrease in display contrast even when a corresponding level of external light intensity is irradiated. A value for correcting the image signal so as to be visually recognized is set. The gamma correction processing unit 352 selects one correction table Tms (1 ≦ s ≦ R) from the R correction tables Tm1 to TmR according to the detection value Lex (of the external light intensity) from the level detection unit 304, With reference to the selected correction table Tms, the signal before correction is subjected to gamma correction, and the corrected signal is output. As shown in FIG. 5, in the present embodiment, the correction unit 350 includes each of the m detection values Lex indicating the external light intensity in the region of the kth display line in the blanking period immediately after the k−1th display period. Is applied to the corresponding data signal (k = 2, 3,..., M).

  In the k-th display period, the signal line driver 302 applies the data signals S (1) to S (m) as the corrected signals to the data signal lines SL (1) to SL (m), respectively. In the k-th display period, the scanning signal G (k) applied to the k-th scanning signal line GL (k) becomes active, and the data signal S (1) to S (m) causes the k-th display line. The pixel capacities of the m pixel forming portions are charged (driving of the display portion for pixel writing of the kth display line).

  In this way, the pixel capacity of the pixel forming portion corresponding to each display line is charged by a data signal that is gamma-corrected according to the external light intensity at each position (each of the m positions) in the display line region. Is done. As a result, even if the external light intensity in the display unit 100 varies from region to region, image correction is performed to compensate for the decrease in contrast in accordance with the external light intensity in each region, and the image is displayed with almost the original contrast over the entire screen. Visible. Further, according to the configuration of the above-described embodiment (see FIG. 4), circuits (TFTs, pixel electrodes, etc.), scanning signal lines GL (1) to GL (n), data signals, and the like that constitute the pixel forming portion in the display portion 100 Each optical sensor 20 and light detection scanning signal lines HL (1) to HL (n) can be integrally formed on the substrate on which the lines SL (1) to SL (m) are to be formed (others). The same applies to the embodiments and modified examples). Therefore, compared with the case where the optical sensors as a plurality of individual components are used, an increase in manufacturing cost associated with the realization of the function of detecting the external light intensity in each area in the display unit 100 can be suppressed.

  When a transmissive liquid crystal panel is used for the display unit 100 and light is emitted from the backlight, the light from the backlight may affect the detected value Lex of the external light intensity. However, since the intensity of the backlight light is substantially constant in the display screen, even in this case, image correction that compensates for a decrease in contrast according to the external light intensity for each region is performed based on the detection value Lex. It can be carried out.

<3. Second Embodiment>
Next, a liquid crystal display device according to a second embodiment of the present invention will be described. Since this liquid crystal display device is substantially the same as that of the first embodiment except for the configuration of the data signal line driving circuit 300, the same reference numerals are assigned to the same or corresponding parts, and detailed description will be given. Omitted.

  FIG. 7 is a block diagram showing a configuration for external light detection and image correction in the present embodiment. As shown in FIG. 7, the data signal line drive circuit 300 in this embodiment includes a level detection unit 306 and a correction unit 360 in addition to the signal line drive unit 302 as in the first embodiment. . However, the configurations and operations of the level detection unit 306 and the correction unit 360 in the present embodiment are different from those in the first embodiment. In the present embodiment, the light detection start pulse signal HSP generated by the display control circuit 200 and input to the light detection scanning signal line drive circuit 420 is also different from the first embodiment in the light detection scanning. The timing of the scanning signals H (1) to H (n) applied to the signal lines HL (1) to HL (n) is different from that of the first embodiment. Hereinafter, with reference to FIG. 7 and FIG. 8, external light detection and image correction in the present embodiment will be described focusing on these differences.

  In this embodiment, the light detection start pulse signal HSP is a signal having a pulse that appears approximately two horizontal periods earlier than the pulse of the gate start pulse signal GSP. Based on the detection start pulse signal HSP and the gate clock signal GCK, the i + 2th light detection scanning signal line HL (i + 2) is active in the blanking period immediately after the i-th display period (i-th horizontal scanning period). A scanning signal H (i + 2) is applied (i = 1, 2,..., N−2).

  As shown in FIG. 8, in the k−1 display period, the pixel capacity of each pixel forming unit corresponding to the k−1 display line is charged by the data signal S (j) and includes the k + 1 display line. The detection capacitors of the optical sensor 20 in all display line regions are charged according to the external light intensity (external light sensing). In this embodiment, unlike the first embodiment, active scanning signals H (1) to H (n) are applied to the light detection scanning signal lines HL (1) to HL (n) as described above. Thus, one end of the detection capacitor of the photosensor 20 in the region of the (k + 1) th display line is electrically connected to the data signal lines SL (1) to SL (m) in the blanking period immediately after the (k-1) th display period. Connected. The level detection unit 306 detects the accumulated charge amount of the detection capacitor in the region of the (k + 1) th display line via these data signal lines SL (1) to SL (m) during this blanking period, and the detection result Based on the above, m detection values are generated and temporarily held as detection values of the external light intensity in the area of the (k + 1) th display line (k = 2, 3,..., N−1). The m detection values for the k + 1 display line are sequentially converted into a digital signal based on the data clock signal SCK in the kth display period, and are provided to the correction unit 360 as the digital detection signal Lex (k + 1 display line). Signal input correction).

  Since the signal line driving unit 302 employs the line sequential driving method, the data signals S (1) to S (m) corresponding to the pixel values of the kth display line are the data signal lines in the kth display period. The display unit 100 is driven by being applied to SL (1) to SL (m), and a digital image signal DV corresponding to the pixel value of the (k + 1) th display line is serially input. The correction unit 360 receives the digital image signal DV as a pre-correction signal and corrects it based on the digital detection signals Lex sequentially input from the level detection unit 306. That is, the correction unit 360 has the same configuration as that of the first embodiment (FIG. 6), and one correction table Tms (1) is selected from the R correction tables Tm1 to TmR according to the digital detection signal Lex. ≦ s ≦ R), gamma correction is performed on the digital image signal DV with reference to the selected correction table Tms, and the corrected signal is output as a modified digital image signal DVm. Thus, the data signals S (1) to S (m) are corrected based on the digital detection signal Lex.

  The signal line driving unit 302 sequentially receives and holds the corrected digital image signal DVm in the k-th display period, converts it into an analog signal in the k + 1-th display period, and converts it into data signals S (1) to S (m). The data signal lines SL (1) to SL (m) are respectively applied. In the (k + 1) th display period, the scanning signal G (k + 1) applied to the (k + 1) th scanning signal line GL (k + 1) becomes active, and the data signal S (1) to S (m) causes m in the (k + 1) th display line. The pixel capacities of the pixel forming portions are charged (driving of the display portion for writing pixel values of the (k + 1) th display line).

  In this way, the pixel capacity of the pixel forming portion corresponding to each display line is charged by a data signal that is gamma-corrected according to the external light intensity at each position (each of the m positions) in the display line region. Is done. As a result, even if the external light intensity in the display unit 100 varies from region to region, image correction is performed to compensate for the decrease in contrast in accordance with the external light intensity in each region, and the image is displayed with almost the original contrast over the entire screen. Visible.

  In the configuration shown in FIG. 7, the correction unit 360 is built in the data signal line drive circuit 300, but the correction unit 360 may be provided outside the data signal line drive circuit 300. For example, the correction unit 360 may be provided in the display control circuit 200. In this case, the digital detection signal Lex is given from the data signal line driving circuit 300 to the display control circuit 200, and the display control circuit 200 generates the corrected digital image signal DVm based on the digital detection signal Lex, and the data signal line driving circuit 300 will be given.

<4. Modification>
In the first and second embodiments, the line-sequential driving method is adopted, but the present invention can also be applied when the point-sequential driving method is adopted. For example, when the present invention is applied to a dot sequential drive type liquid crystal display device with a configuration as shown in FIG. 7, the latch strobe signal LS is not necessary, but the modified digital image signal output from the correction unit 360 is used. A DA converter that converts DVm into an analog signal is required.

  In the first and second embodiments, each optical sensor 20 includes a detection capacitor for accumulating a charge amount corresponding to the external light intensity, and the external light intensity in each display period (horizontal scanning period). However, the detection capacitor may be provided for each data signal line in the level detection unit 306. In this case, one of the photodetection scanning signal lines HL (i) is selected within the (horizontal) blanking period, and photoelectric conversion of each photosensor 20 corresponding to the photodetection scanning signal line HL (i) is performed. The detection capacitor in the level detection unit 306 is charged through each data signal line SL (j) by the photocurrent generated by the element. That is, in this case, external light sensing is performed not in the display period but in the return period. According to such a configuration, the time available for external light sensing is shortened, but the configuration of each optical sensor 20 can be simplified.

1 is a schematic block diagram for explaining a basic configuration and characteristics of a liquid crystal display device according to the present invention. It is a figure which shows the example of a display for demonstrating the effect of this invention. 1 is a block diagram illustrating a configuration of a liquid crystal display device according to a first embodiment of the present invention. It is a block diagram which shows the structure for the external light detection and image correction in the said 1st Embodiment. It is a signal waveform diagram for explaining operation of the liquid crystal display device concerning the above-mentioned 1st embodiment, and a figure showing a processing flow. It is a block diagram which shows the structure of the correction | amendment part in the said 1st Embodiment. It is a block diagram which shows the structure for the external light detection and image correction in the 2nd Embodiment of this invention. It is a signal waveform diagram for explaining operation of the liquid crystal display device concerning the above-mentioned 2nd embodiment, and a figure showing a processing flow. It is a schematic block diagram for demonstrating the conventional liquid crystal display device (conventional example). It is a figure which shows the example of a display for demonstrating the problem in the conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Optical sensor 50 ... Image correction part 100 ... Display part 200 ... Display control circuit (display control part)
300 ... Data signal line drive circuit 302 ... Signal line drive unit 304, 306 ... Level detection unit 350, 360 ... Correction unit (image correction unit)
352... Gamma correction processing unit 354. Correction storage unit 400... Scanning signal line drive circuit 420... Light detection scanning signal line drive circuit Tm1 to TmR.
GL (i) ... scanning signal line (i = 1 to n)
HL (i): scanning signal line for light detection (i = 1 to n)
SL (j) ... Data line (j = 1 to m)
TL (j): Data line for light detection (j = 1 to m)
DV: Digital image signal (before correction)
DVm: Modified digital image signal G (i): Scanning signal line (i = 1 to n)
H (i) ... (for light detection) scanning signal (i = 1 to n)
Lex ... detection value (detection signal)
SCK ... Data clock signal SSP ... Data start pulse signal GCK ... Gate clock signal GSP ... Gate start pulse signal HSP ... Photodetection start pulse signal HSY ... Horizontal synchronization signal VSY ... Vertical synchronization signal

Claims (6)

The plurality of data signal lines, the plurality of scanning signal lines intersecting with the plurality of data signal lines, and the intersections of the plurality of data signal lines and the plurality of scanning signal lines are arranged in a matrix. A liquid crystal display device having a display unit including a plurality of pixel forming units and displaying an image on the display unit based on an input signal given from outside,
A data signal line driving circuit for generating a plurality of data signals representing an image to be displayed on the display unit based on the input signal and applying the data signals to the plurality of data signal lines;
A scanning signal line driving circuit for selectively driving the plurality of scanning signal lines;
An external light detection unit that includes a plurality of optical sensors disposed in the display unit, and detects the intensity of external light in the display unit for each predetermined region;
A liquid crystal display device comprising: an image correction unit that corrects an image to be displayed on the display unit according to a distribution of the intensity of the external light in the display unit based on a detection result by the external light detection unit.   The image correction unit corrects the plurality of data signals based on the detection result of the external light detection unit, thereby compensating for a decrease in contrast of an image displayed on the display unit due to external light for each predetermined region. The liquid crystal display device according to claim 1, wherein an image to be displayed on the display unit is corrected. The image correction unit
A plurality of gamma correction tables prepared in advance as a table for correcting the value indicated by the input signal so that the relationship between the input signal and the luminance of the pixel formed by the pixel forming unit is changed;
By selecting one gamma correction table from the plurality of gamma correction tables based on the detection result by the external light detection unit, and correcting the value indicated by the input signal based on the selected gamma correction table, The liquid crystal display device according to claim 2, further comprising: a correction processing unit that corrects the plurality of data signals so that a decrease due to external light is compensated for each predetermined region. The plurality of photosensors are arranged in a matrix in the display unit,
The outside light detector is
Photodetection scanning signal lines disposed along each row of the matrix of photosensors;
A photodetection data signal line disposed along each column of the matrix of photosensors;
A photodetection scanning signal line driving circuit for selectively driving the photodetection scanning signal line so that a selection period of the photodetection scanning signal line does not overlap any of the selection periods of the plurality of scanning signal lines;
When any one of the light detection scanning signal lines is selected, an external light intensity detected value by an optical sensor arranged along the selected light detection scanning signal line is used as the light detection data signal. A level detection unit that acquires via a line,
The light detection scanning signal line is arranged in parallel with the plurality of scanning signal lines,
The liquid crystal display device according to claim 1, wherein the data signal line for photodetection is shared with the plurality of data signal lines. The light detection scanning signal line corresponds to each of the plurality of scanning signal lines,
The scanning signal line driving circuit for light detection has a detection value of an external light intensity detected by a photosensor in a row corresponding to the scanning signal line to be selected before each scanning signal line is selected within each frame period. Select each light detection scanning signal line to be acquired by the level detection unit,
The image correction unit corrects the plurality of data signals to be applied to the plurality of data signal lines based on the detected value of the external light intensity when the scanning signal line to be selected is selected. The liquid crystal display device according to claim 4, wherein an image to be displayed on the display unit is corrected by the operation.   The plurality of photosensors, the photodetection scanning signal lines, and the photodetection data signal lines are integrally formed on a substrate on which circuits constituting the plurality of pixel forming portions are formed. The liquid crystal display device according to claim 4, wherein: