JP2009294506A - Display device and method for adjusting display quality of display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress influences on visual luminance over the entire panel when abnormality occurs in individual illuminators constituting an auxiliary light source. <P>SOLUTION: The visual luminance of the entire display panel is controlled to be uniform in the following way. In a plurality of cold cathode tubes 410 in a backlight section 400, whether or not abnormality occurs in any of the tubes to fail to normally emit light is monitored; if abnormality occurs, a power supply voltage supplied to a horizontal scanning section is adjusted, or a video signal sent from the horizontal scanning section to pixel cells is adjusted, or the intensity of illumination light illuminating the display panel by the backlight section 400 is adjusted, so as to compensate a decrease in the luminance in a display abnormality area T_NG of a display panel, which may be induced by the occurrence of abnormality of the cold cathode tube 410. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display panel including a pixel circuit (also referred to as a pixel) including an electro-optical element (also referred to as a display element or a light emitting element), a display device including a light source device that illuminates the display panel, and The present invention relates to a method for adjusting display quality of a display device. More specifically, the present invention relates to a display device having a function of correcting display unevenness caused by a light source device and a method for adjusting the display quality.

  As a display element of a pixel, there is a display device using an electro-optical element whose luminance changes depending on an applied voltage or a flowing current. For example, a liquid crystal display element is a typical example of an electro-optical element whose luminance changes depending on an applied voltage, and an organic electroluminescence (Organic Electro Luminescence, Organic EL, Organic) (Light Emitting Diode, OLED; hereinafter referred to as “organic EL”) A typical example is an element. The organic EL display device using the latter organic EL element is a so-called self-luminous display device using an electro-optic element which is a self-luminous element as a pixel display element.

  In a self-luminous display device, as a screen adjustment, contrast adjustment and brightness adjustment are performed by adjusting an image signal written in a pixel cell. On the other hand, in the case of a display device that is not self-luminous, in many cases (but not essential), an illumination unit serving as an auxiliary light source is used to illuminate the illumination light emitted from the illumination unit with the display surface side or the display surface. Irradiation is from the back side on the opposite side. For example, a liquid crystal display device using a liquid crystal element as an electro-optical element of a pixel cell is a typical example.

  In a display device that uses an auxiliary light source, the light emitted from the light source device has non-uniformity, and this non-uniformity of light has a considerable influence on the display quality of the liquid crystal display device. . This tendency becomes more conspicuous as the liquid crystal display device becomes larger, and there is a mechanism for making the light uniform by using a diffusion sheet or the like. However, the current situation is that the light unevenness is not sufficient. Thus, a mechanism for preventing display unevenness due to nonuniformity of light emitted from the auxiliary light source has been proposed (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 08-313879

  For example, in the mechanism described in Patent Document 1, a display screen of a liquid crystal display panel displayed via a liquid crystal display panel, a backlight device, a signal processing device, and a backlight device is divided into predetermined areas and a predetermined display screen is displayed. Detection means such as an RGB sensor for detecting the hue and brightness of the area, a memory for storing detection data of the detection means, and a predetermined area of the display screen based on the detection data of the detection means stored in the memory A liquid crystal display device is configured with correction means for correcting hue and luminance. Then, the hue and luminance in the area are detected by the detecting means, and the correction means detects the hue and luminance in the liquid crystal display panel so that the hue and luminance in each area are the same based on the hue and luminance detection data stored in the memory. By changing the drive data (applied voltage) of each area and automatically adjusting the display screen of the liquid crystal display panel to be uniform, uneven brightness due to non-uniformity of light emitted from the backlight unit Prevents uneven hue.

  Here, in a display device of a type using an auxiliary light source, if there is an abnormality in the illuminating body that constitutes the light source, significant unevenness of illumination light occurs, and significant display unevenness occurs. For this measure, it is conceivable to use the mechanism described in Patent Document 1.

  However, the mechanism described in Patent Document 1 is a countermeasure method in the case where the illumination light is still non-uniform on the assumption that all the illuminating bodies constituting the backlight unit are normal, and is stored in the memory. The acquisition of the detection data and the change of the drive data by the detection means are not triggered by the backlight abnormality detection. In other words, the mechanism described in Patent Document 1 is merely drive data control focusing on the fact that there is non-uniformity of light even if the backlight unit is normal, and there is an abnormality in the individual illuminating bodies constituting the backlight unit. There is no control taking into account when this occurs.

  Further, the mechanism described in Patent Document 1 has a drawback that a detection unit that acquires detection data stored in a memory referred to when changing drive data in a correction mode is required separately from the apparatus main body. . Therefore, for example, it is difficult to apply to a portable device (PDA (Personal Digital Assistant), portable terminal, notebook personal computer, etc.).

  The present invention suppresses the influence on the visually perceived display performance (particularly viewing luminance: luminance in the case of black and white, hue in the case of color) when an abnormality occurs in the individual illuminating bodies constituting the auxiliary light source. The purpose is to provide a mechanism that can do this.

  In one form of the display device and the display quality adjustment method according to the present invention, first, the display device includes a display panel that includes a plurality of pixel cells and displays an image based on an input image signal, and a plurality of illumination bodies. A lighting unit that illuminates the display panel, a horizontal scanning unit that sends a video signal to each pixel cell of the display panel, a vertical scanning unit that vertically scans each pixel cell of the display panel, and a power supply voltage to the horizontal scanning unit. And a power supply unit to supply. When the pixel cell includes an electro-optical element that is not self-luminous, it is preferable to further include an illumination unit that illuminates the display panel. These may be considered to be the same as those provided in a general panel type display device using an auxiliary light source.

  Further, as a characteristic matter in one embodiment of the display device and the display quality adjustment method according to the present invention, when an abnormality occurs in any lighting body of the lighting unit and normal light emission cannot be obtained, the power source unit To control the power supply voltage supplied to the horizontal scanning unit, adjust the video signal sent from the horizontal scanning unit to the pixel cell, or adjust the intensity of the illumination light that the illumination unit illuminates the display panel Thus, a display brightness control unit is provided for controlling the viewing brightness of the entire display panel to be uniform. The control by the display brightness control unit is such that the viewing brightness of the display abnormal area corresponding to the illuminating body in which an abnormality has occurred in the display panel and the display normal area other than the display abnormal area are the viewing brightness before the occurrence of the abnormality. It means to keep it the same.

  In other words, if any abnormality occurs in any of the plurality of illuminating bodies in the illuminating unit and normal light emission cannot be obtained, and if an abnormality occurs, the abnormality occurs in the illuminating body. Contrast control and illumination light control are performed so as to correct a decrease in luminance of a corresponding portion (display abnormal region) in the obtained display panel.

  According to one aspect of the present invention, when abnormality occurs in any of the plurality of illuminating bodies constituting the illuminating unit and normal light emission cannot be obtained, contrast control is performed so as to compensate for a decrease in luminance in the display abnormal region. Since the illumination light control is performed, the display screen of the display panel can be made uniform even when an abnormality occurs.

  In addition, it is only necessary to start control by monitoring which of the plurality of illuminating bodies constituting the illuminating unit has an abnormality. Reference is made when changing drive data as in the mechanism described in Patent Document 1. It is not essential to have a detection means for acquiring detected detection data under the correction mode and a memory for storing detected detection data, so that it is easy even for portable devices such as PDAs, portable terminals, and notebook computers. Applicable to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, a liquid crystal element that is not a self-luminous type will be described as an example of a pixel display element, and a transmissive display device that uses an auxiliary light source as a backlight will be described in detail. However, this is merely an example, and a reflective display device that irradiates illumination light emitted from an auxiliary light source from the front side, or a liquid crystal element that is not a self-luminous type as a pixel display element, and an auxiliary light source is not used. A reflective display device using ambient light may also be used. Furthermore, a display device called a transflective type in which functions of a transmissive type and a reflective type are incorporated in one display panel may be used. The target display element is not limited to a liquid crystal element. The embodiments described later can be similarly applied to all display elements that emit light by voltage driving and display elements that emit light by current driving. In the case of a display device that does not use an illuminating unit as an auxiliary light source, it goes without saying that an embodiment that controls a part related to the illuminating unit is not applicable.

<Overall configuration of liquid crystal display device>
FIG. 1 is a diagram showing an outline of the overall configuration of an embodiment of a liquid crystal display device using a liquid crystal element as an electro-optical element, for example. Such a display device is used for a display unit of a portable music player or other electronic device using a recording medium such as a semiconductor memory, a mini disk (MD), or a cassette tape.

  As shown in FIG. 1, in the liquid crystal display device 1, a pixel array unit 3 is integrally formed on a substrate 2, and a gate driver unit 5 (also referred to as a vertical driving unit) which is a first control unit in the vicinity thereof. And a source driver unit 6 (also referred to as a horizontal driving unit) as a second control unit. The gate driver unit 5 and the source driver unit 6 are supplied with video signals and various pulse signals from a drive control circuit arranged outside the panel.

  Although the figure shows a form in which the pixel array part 3 alone is used as the display panel part, the product form is not limited to this. That is, as a product form, a display panel unit in which a control unit such as a pixel array unit 3 and a gate driver unit 5 and a source driver unit 6 are mounted on the same glass substrate is separated from a drive signal generation unit and a video signal processing unit. (Referred to as an arrangement configuration on the panel), the display panel unit is mounted with the pixel array unit 3, and a control unit, a drive signal generation unit, a video signal processing unit, etc. on a separate substrate (for example, a flexible substrate) A configuration in which the peripheral circuit is mounted (referred to as a configuration outside the peripheral circuit panel) is conceivable.

  In addition, in the case of the on-panel arrangement configuration in which the pixel array unit 3 and the control unit are mounted on the same glass substrate to constitute the display panel unit, the control unit (necessary at the time of generating the TFT of the pixel array unit 3) And a glass substrate on which the pixel array unit 3 is mounted by a COG (Chip On Glass) mounting technique. A mechanism (referred to as a COG mounting configuration) for directly mounting a semiconductor chip for a control unit (and a drive signal generation unit and a video signal processing unit as necessary) may be considered.

  In the configuration outside the peripheral circuit panel and the COG mounting configuration (also collectively referred to as a control unit retrofit configuration), there is a point in time when the pixel array unit 3 and the control unit are separate. Since the image display cannot be performed unless the pixel array unit 3 and the control unit are connected, a defect of each pixel in the pixel array unit 3 (TFT short-circuit or open) or a scan line defect (disconnection or adjacent scan line). Contact) cannot be performed.

  For this reason, in the case of adopting a control unit retrofitting configuration, for the purpose of inspecting each pixel and scanning line of the pixel array unit 3 in the peripheral part of the pixel array unit 3 without connecting the control unit to the pixel array unit 3 A simple lighting test may be performed by providing a test switch circuit that can supply a test signal to each scanning line from the outside of the pixel array unit 3. In addition, in the retrofitting configuration of the control unit, there is a point in time when the pixel array unit 3 and the control unit are separate from each other. Since there is a greater possibility of static electricity being applied and circuit elements being destroyed than in the case of a TFT integrated configuration, an electrostatic protection circuit may be provided for each scanning line for the purpose of protecting the circuit elements from static electricity damage. .

  The pixel array unit 3 has a panel structure including a pair of substrates 2 and a liquid crystal element 32 held between the substrates. For example, pixel cells 30 including pixel transistors and the like are two-dimensionally arranged in a matrix on a transparent insulating substrate, for example, a first glass substrate (drive side substrate), and a vertical scanning line is provided for each row with respect to this pixel array. In addition to being wired, horizontal scanning lines are wired for each column. The first glass substrate is disposed to face the second glass substrate (opposite side substrate) with a predetermined gap, and is bonded together with a sealant (not shown). Then, the liquid crystal material is sealed in a region inside the position of the sealant. In the case of a color liquid crystal display panel, a color filter is arranged on the display surface side with the filter color position and the pixel position aligned.

  For example, a vertical scanning line 12 (gate line) that transmits a row selection pulse supplied from the gate driver unit 5 and a source output voltage Vsource supplied from the source driver unit 6 are transmitted to the pixel array unit 3 to transmit a liquid crystal element. A horizontal scanning line 14 (also referred to as a signal line or a data line) is formed. A pixel cell 30 is disposed at the intersection of the two. The pixel cell 30 includes a liquid crystal element 32, a thin film transistor 34 (TFT) that drives a pixel electrode of the liquid crystal element 32, and a storage capacitor 36 (pixel capacitor) that holds a pixel signal. In the figure, one vertical scanning line 12, one horizontal scanning line 14, and one pixel cell 30 are shown, but the pixel cells 30 are arranged in a two-dimensional matrix, and the vertical scanning line 12 with respect to these pixel cells 30. And a horizontal scanning line 14 are wired.

  The gate driver unit 5 sequentially selects each pixel cell 30 via the vertical scanning line 12. The source driver unit 6 writes an image signal to the selected pixel cell 30 via the horizontal scanning line 14. For example, the gate driver unit 5 includes a gamma correction circuit that performs gamma correction on the output image signal Vsout from the timing controller unit 300 based on the reference gamma voltage Vγ from the gradation reference voltage generation unit 200 and a video signal after gamma correction. A sampling circuit that samples and holds the output image signal Vsout as an output image signal Vsout, an output buffer that supplies the output image signal Vsout to the pixel cell 30 via the horizontal scanning line 14, and the like. The output buffer is configured by a combination of logic gates (including latches), and selects each pixel cell 30 of the pixel array unit 3 in units of rows.

  Although FIG. 1 shows a configuration in which the gate driver unit 5 is arranged only on one side of the pixel array unit 3, a configuration in which the gate driver unit 5 is arranged on both the left and right sides with the pixel array unit 3 in between is adopted. Is also possible. The source driver unit 6 includes a shift register, a sampling switch (horizontal switch), and the like, and writes a video signal in units of pixels to each pixel cell 30 in a row selected by the gate driver unit 5. 1 shows a configuration in which the source driver unit 6 is disposed only on one side of the pixel array unit 3, but a configuration in which the source driver unit 6 is disposed on both upper and lower sides with the pixel array unit 3 interposed therebetween is employed. Is also possible.

  Here, the dot sequential drive for writing the video signal in the pixel unit to each pixel cell 30 in the selected row is taken as an example, but the line sequential drive for writing the video signal in the row unit to each pixel cell 30 in the selected row. It is also possible to adopt.

  Further, the liquid crystal display device 1 has a source voltage supply power supply unit that mainly generates a power supply voltage for the source driver unit 6 (hereinafter referred to as a source power supply voltage Vsd) around the pixel array unit 3 (outside of the panel in the figure). 100, a gradation reference voltage generation unit 200 that generates a gradation reference voltage (hereinafter referred to as a reference gamma voltage Vγ) indicating a γ (gamma, gradation) curve for the source driver unit 6, a gate driver unit 5 and a source The driver unit 6 includes a timing controller unit 300 that transmits an output image signal Vsout and a timing signal. Furthermore, the liquid crystal display device 1 includes a backlight unit 400 that is an example of an illumination unit (light source or lighting unit) that illuminates the display panel, a source voltage supply power unit 100, a gradation reference voltage generation unit 200, and a timing controller unit 300. And a control / overall unit 500 that is an example of a display luminance control unit that controls the operation of the entire apparatus, such as the backlight unit 400. Although not shown, for example, a gate power supply unit that mainly generates a power supply voltage Vgd for the gate driver unit 5 is also provided.

  The source voltage supply power supply unit 100 includes a power supply generation unit 102 that generates a source power supply voltage Vsd. For example, the power supply generation unit 102 is a step-up type switching power supply, and includes a switching drive unit 110 including a switching transistor (hereinafter referred to as SWTR122) configured by an FET (Field-Effect Transistor), and a SWTR122. A coil 124 to be driven, a rectifying diode 126, and a rectifying capacitor 128 are included.

  A coil 124 is provided between the drain of the SWTR 122 and the input power supply Vi (<source power supply voltage Vsd). An anode of the diode 126 is connected to a connection point (referred to as a node ND_1) between the drain of the SWTR 122 and one terminal of the coil 124, and a capacitor 128 is provided between the cathode of the diode 126 and the ground wiring GND. One connection point between the cathode of the diode 126 and the capacitor 128 is referred to as a node ND_2. As an example, the switching drive unit 110 including the SWTR 122 is an IC for switching power supply (accommodated in a semiconductor integrated circuit).

  The source voltage supply power supply unit 100 supplies the source power supply voltage Vsd having a predetermined value to the source driver unit 6 side in normal times. Further, the source power supply voltage Vsd is raised so as to be in an appropriate state based on an instruction from the control / supervision unit 500 via the control signal CN_1.

  The gradation reference voltage generation unit 200 receives the source power supply voltage Vsd from the source voltage supply power supply unit 100 and receives, for example, an analog method using a resistance dividing circuit or a digital method using table data (lookup table) (for example, 8 ˜12 bits), a reference gamma voltage Vγ defining the γ curve is supplied to the source driver unit 6. For example, a reference gamma voltage Vγ that provides a standard γ curve with respect to a value when the source power supply voltage Vsd is normal is supplied to the source driver unit 6. Further, the reference gamma voltage Vγ is set to an appropriate state based on an instruction from the control / supervision unit 500 via the control signal CN_2.

  The timing controller unit 300 includes a level conversion unit 310 that converts an input image signal Vsin into an output image signal Vsout, and a timing generator unit 320 that generates a timing signal. The level conversion unit 310 converts the input image signal Vsin into the output image signal Vsout by, for example, an analog method using a resistance dividing circuit or a digital method (for example, 8 to 12 bits) using table data (lookup table). Normally, the input image signal Vsin is supplied to the source driver unit 6 as the output image signal Vsout. Further, the input / output relationship of the image signal is corrected based on an instruction from the control / supervision unit 500 via the control signal CN_3.

  The backlight unit 400 includes a backlight driving unit 420 having a dimming function and an abnormality detection function for a plurality of illumination bodies. The backlight driving unit 420 controls the light emission luminance of the plurality of illuminators and sets the backlight luminance to a predetermined backlight value at the normal time. Further, the backlight luminance is increased by a predetermined amount based on an instruction from the control / supervision unit 500 via the control signal CN_4. Further, when the backlight unit 400 detects an abnormality of the illuminating body, the backlight unit 400 notifies the control / supervision unit 500 of an abnormality detection signal DET_NG.

  The control / supervision unit 500 controls the source voltage supply power source unit 100 to be supplied to the source driver unit 6 when an abnormality occurs in any one of the backlight units 400 and normal light emission cannot be obtained. Adjusting the source power supply voltage Vsd, adjusting the source output voltage Vsource sent from the source driver unit 6 to the pixel cell 30, or adjusting the intensity of the illumination light that the backlight unit 400 illuminates the display panel. Then, the viewing brightness of the entire display panel is controlled to be uniform.

  At this time, the control / supervision unit 500 first monitors the abnormality detection signal DET_NG for each illuminating body notified from the backlight unit 400, and if an abnormality (deterioration or failure) of the cold cathode tube 410 is detected, an alarm is generated. To notify the user and encourage exchange.

  In addition, when the abnormality detection signal DET_NG is active (that is, when there is an abnormality in the illuminating body), the control / supervision unit 500 reduces the viewing luminance that may occur in a corresponding area (referred to as a display abnormality area T_NG) in the display panel. The source voltage supply power supply unit 100, the gradation reference voltage generation unit 200, and the level conversion unit 310 of the timing controller unit 300 are controlled so as to be corrected. That is, the control / supervisory unit 500 monitors the abnormality detection signal DET_NG and controls each unit so that the decrease in luminance of the display abnormal region T_NG in the liquid crystal panel is corrected, whereby the luminance and hue of the display screen of the display panel can be controlled. Keep it uniform. The degree of correction may be determined appropriately in advance by estimating the luminance reduction portion distribution when the illuminator is not emitting light.

  Preferably (although not essential), the liquid crystal display device 1 corresponds to a display panel when light emission of a certain illuminator is stopped (substantially equivalent to when an abnormality occurs), as indicated by a dotted line in the figure. A configuration having a luminance decrease distribution storage unit 512 that stores a distribution state of a viewing luminance decrease that may occur in a region (display abnormal region T_NG) in a semiconductor memory or the like for each illuminating body is adopted. In this case, when the control / supervision unit 500 and the luminance decrease distribution storage unit 512 cause abnormality in any of the illuminating bodies of the backlight unit 400 and normal light emission cannot be obtained, the source voltage supply power source unit 100 is Control the source power supply voltage Vsd supplied to the source driver unit 6 and adjust the source output voltage Vsource sent from the source driver unit 6 to the pixel cell 30, or the backlight unit 400 illuminates the display panel. By adjusting the intensity of the illumination light to be displayed, a display luminance control unit 9 is configured to control the viewing luminance of the entire display panel to be uniform.

  When the abnormality detection signal DET_NG is active (that is, when there is an abnormality in the illuminating body), the control / supervision unit 500 refers to the distribution state of the viewing luminance reduction for each illuminating body stored in the luminance declining distribution storage unit 512. Thus, the source voltage supply power supply unit 100, the gradation reference voltage generation unit 200, and the level conversion unit 310 of the timing controller unit 300 are controlled so as to correct the viewing luminance decrease that may occur in the display abnormality region T_NG. That is, the control / supervisory unit 500 monitors the abnormality detection signal DET_NG and controls each unit so that the decrease in luminance of the display abnormal region T_NG in the liquid crystal panel is corrected, whereby the luminance and hue of the display screen of the display panel can be controlled. Keep it uniform. The configuration provided with the luminance decrease distribution storage unit 512 can realize correction in accordance with the device.

  For this reason, when the abnormality detection signal DET_NG is received from the backlight driving unit 420, the control / supervision unit 500 completely stops the illumination by the illuminating body corresponding to the abnormality detection signal DET_NG in order to properly correct the viewing luminance. Let For example, it is not allowed to leave a halfway operation state such as an abnormal operation caused by a discharge that repeatedly turns on and off, or lighting in a state where appropriate luminance cannot be obtained.

  The control / supervisory unit 500 preferably corresponds to the luminance unevenness distribution of the display panel when each illuminator of the control / supervisory unit 500 becomes abnormal and stops emitting light, that is, the correspondence of the luminance decrease distribution based on the luminance decrease due to the illuminant that does not emit light Is specified in advance and stored in the luminance decrease distribution storage unit 512. The source power supply voltage Vsd by the source voltage supply power supply unit 100 is increased so that the luminance of the display abnormality region T_NG increases based on the correspondence relationship of the luminance decrease distribution based on the luminance decrease by the illuminating body that does not emit light. , Adjustment of the curve of the reference gamma voltage Vγ by the gradation reference voltage generation unit 200, increase of the output image signal Vsout by the level conversion unit 310, and adjustment of the backlight luminance by the backlight unit 400 are referred to as “appropriate state”. Control to be. Such control is referred to as luminance maintenance control for an illuminant abnormality. Hereinafter, an example of the control method will be described. Incidentally, the increase of the source power supply voltage Vsd, the adjustment of the curve of the reference gamma voltage Vγ, and the increase of the output image signal Vsout act on the source output voltage Vsource (pixel signal level) itself for driving the pixel cell 30, and so-called contrast adjustment. The backlight luminance is adjusted to increase or decrease the entire display luminance level regardless of the source output voltage Vsource, and corresponds to so-called brightness adjustment.

  Here, the “appropriate state” is correction of a decrease in viewing luminance (and luminance unevenness and hue unevenness caused by this) that may occur in the display abnormal region T_NG illuminated by the abnormal illumination body of the backlight unit 400 in the liquid crystal panel unit. It means a state that can be done. In order to form a state in which a decrease in viewing luminance can be corrected, not only the correction of the source power supply voltage Vsd by the source voltage supply power supply unit 100 but also the reference gamma voltage Vγ by the gradation reference voltage generation unit 200 is necessary. This is combined with the correction of the output image signal Vsout by the curve and level conversion unit 310 and the correction of the backlight luminance by the backlight unit 400. The basic idea is that the viewing brightness of the display abnormal area T_NG is maintained the same as the viewing brightness before the occurrence of the abnormality.

  For example, the normal brightness level is set for the display normal area T_OK, and the viewing brightness of the display abnormal area T_NG is the same level as the viewing brightness before the occurrence of abnormality for only the display abnormal area T_NG in vertical scanning. Any one of the source power supply voltage Vsd, the curve of the reference gamma voltage Vγ, the correspondence between the input image signal Vsin and the output image signal Vsout (the input / output relationship of the image signal) A first luminance maintenance control method for correcting any combination is adopted. In this first luminance maintenance control method, the adjustment of the backlight luminance is not applied in order to increase the backlight luminance of only the display abnormal region T_NG that occurs when illuminated by an abnormal illumination body. This is because it is necessary to increase the light emission luminance of the illuminating body, but this is actually impossible.

  Alternatively, the source power supply voltage Vsd, the reference gamma voltage Vγ curve, and the input of the image signal are applied to the entire panel in a direction in which the viewing brightness increases so that the display abnormal area T_NG is substantially the same as the original display brightness. A display that will perform the first correction of any combination other than at least one of the output relation and the backlight luminance, and will be higher than the original viewing luminance due to the first correction. Before the occurrence of an abnormality in the illumination body of the display abnormal area T_NG, the viewing brightness of the display normal area T_OK is such that the portion adjusted in the increasing direction is offset with respect to the portion excluding the abnormal area T_NG (referred to as the normal display area T_OK) The first correction among the source power supply voltage Vsd, the reference gamma voltage Vγ curve, the input / output relationship of the image signal, and the backlight luminance in a direction in which the viewing luminance decreases to the same level as the viewing luminance of The second luminance maintenance control method for performing the second correction of any one or an arbitrary combination excluding those to which has been applied.

  In both the first and second luminance maintenance control methods, increasing the source power supply voltage Vsd causes an increase in heat generation of the source driver unit 6. For this reason, in both the first and second luminance maintenance control methods, it is preferable to perform corrections other than the correction for increasing the source power supply voltage Vsd. Further, when the second luminance maintenance control method is adopted, the curve of the reference gamma voltage Vγ excluding the source power supply voltage Vsd, the input / output relationship of the image signal, the backlight luminance with respect to the entire panel surface in the direction in which the viewing luminance increases. The source driver corrects any one or any combination of backlight luminances, and further corrects the normal display region T_OK in a direction in which the viewing luminance decreases by decreasing the source power supply voltage Vsd. It is also possible to obtain an additional effect of suppressing an increase in heat generation at the portion 6.

  By adopting such a mechanism, the display screen of the display panel is made to correspond to the position of the illuminating body, and the luminance and hue are corrected for each display abnormal region T_NG that occurs when the illuminating body does not emit light. By automatically adjusting the partial area (illuminating body area) corresponding to the illuminating body to have the same brightness and hue, even if an abnormality occurs in any of the illuminating bodies, the display screen can maintain a uniform quality. Like that.

<Configuration example of the power generation unit>
FIG. 2 is a diagram illustrating details of the power generation unit 102 (particularly, the switching drive unit 110). First, a series circuit of voltage detection bleeder resistors 132 and 134 is connected in parallel with the capacitor 128. A bleeder resistor 132 is disposed on the node ND_2 side, and a bleeder resistor 134 is disposed on the ground wiring GND side. Based on the ratio of the resistance value R_132 of the bleeder resistor 132 and the resistance value R_134 of the bleeder resistor 134, a detection voltage Vsens (= Vsd · R_134 / (R_132 + R_134) is obtained at the connection point of the bleeder resistors 132 and 134 (referred to as node ND_5).

  The switching drive unit 110 includes a variable reference power source 112 that generates a reference voltage Vstd, a voltage amplification unit 114 that amplifies a difference between the reference voltage Vstd and the detection voltage Vsens, and an amplification result (feedback signal Vr) by the voltage amplification unit 114. And a PWM driver 116 (PWM: Pulse Width Modulation) for switching and driving the SWTR 122. The reference power supply 112 is supplied with a control signal CN_1 from the control / supervisory unit 500, and the source power supply voltage Vsd is adjusted by adjusting the reference voltage Vstd based on the control signal CN_1. The PWM driver 116 is supplied with a reference signal (for example, a triangular wave) having a predetermined frequency for switching driving (switching frequency Fsw), and changes the duty ratio D of the pulse wave in accordance with the feedback signal Vr, thereby modulating and driving the SWTR 122. To do. Here, the duty ratio D is represented by D = τ / T, where pulse width τ (active H width) and switching period Tsw (= 1 / Fsw).

  The power supply generation unit 102 is configured to perform a negative feedback operation as a whole, and the detection voltage Vsens is set so as to maintain the source power supply voltage Vsd at a desired value (in this example, Vstd · (1 + R_132 / R_134)). When the voltage is lower than the reference voltage Vstd, the ON period of the SWTR 122 is lengthened and the source power supply voltage Vsd is increased. Conversely, when the detection voltage Vsens is higher than the reference voltage Vstd, the ON period of the SWTR 122 is shortened and the source power supply voltage Vsd is set. Operates to lower.

  Energy is stored in the coil 124 by flowing a current from the input power source Vi to the ground wiring GND via the coil 124 and the SWTR 122 during the ON period of the SWTR 122, and a load (source driver) is stored by the energy stored in the coil 124 during the OFF period of the SWTR 122. The source driver supply power supply current Is is supplied to the most part 6). The current flowing through the SWTR 122 during the on period and the current flowing through the source driver supply power current Is flowing through the source driver unit 6 during the off period may be considered to be substantially the same (except for loss and other than the source driver unit 6).

<Configuration example of backlight unit>
FIG. 3 is a diagram for explaining the details of the backlight unit 400. The backlight unit 400 is disposed close to a liquid crystal display panel having the pixel array unit 3 as a main part, and irradiates the liquid crystal display panel with light. As shown in FIG. 3A, the backlight unit 400 is provided with, for example, a diffusion plate 402 for correcting light unevenness and a reflection plate 404 for improving light utilization efficiency.

  In order to improve the color purity of the liquid crystal display panel, the backlight unit 400 has four-wavelength fluorescence including a three-wavelength phosphor whose spectral characteristics are adapted to the spectral characteristics of the color filter and a fourth wavelength component (for example, a crimson component). A cold-cathode tube (CCFL: Cold-Cathode Fluorescent Lamp) using a body is mainly used for an illuminating body (luminous body). An illuminating device that uses a cold-cathode tube as an illuminating body is made of a glass material that requires a high voltage for lighting, and whose life is shortened when lighting and extinguishing of a fluorescent tube are repeated repeatedly. However, there is a problem that the degree of freedom of shape is limited as a shape light source.

  The illuminating body of the liquid crystal display is not limited to a cold cathode tube, and for example, a hot cathode tube or a light emitting diode (LED) may be used. Moreover, you may use planar light emitting elements, such as a flat fluorescent lamp (FFL: Flat Fluorescent Lamp) and an electroluminescence (EL: Electro Luminescence) element.

  When an LED illumination device using a light emitting diode is used for a backlight or the like, a method of emitting white illumination light by arranging white LEDs, or R (red), G (green), B (blue) 3 Any system in which primary color LEDs are arranged and these three primary color lights are mixed to form white light can be adopted. When adopting a system that mixes the light of the three primary colors to produce white light, if any one of the colors becomes abnormal and does not emit light, the three primary colors will become halfway and the white balance will be lost. The remaining light is also turned off.

  As a method of obtaining a white LED, for example, a method of obtaining a white color by combining a yellow phosphor with a blue LED chip, a method of obtaining a white color by combining an RGB phosphor with a short wavelength LED chip, and a three-color LED chip of RGB Any method such as a method of obtaining white as mixed light and a method of obtaining white as mixed light of two-color LED chips which are complementary colors can be adopted. A lighting device that uses an LED as an illuminator can be driven at a lower voltage, consumes less power, has a longer life, and uses a mixed color of three colors than a lighting device using a fluorescent tube such as a cold cathode tube. Have advantages such as increased color reproducibility and freedom in white balance adjustment.

  Here, the structure of the backlight is a structure called an area light system or a direct system (DLT: Direct-Lit) in which a planar light source is formed by arranging illuminating bodies behind the liquid crystal display panel (directly below). Configuration) or a structure called an edge light system or light guide plate system (ELC: Edge-Lit Configuration) in which an illuminating body is arranged on the side of a light guide plate placed behind a liquid crystal panel to form a planar light source. Is present. For example, when an area light type planar light source using a cold cathode tube is used, a configuration is adopted in which a plurality of cold cathode tubes are connected in parallel so that the luminance of each cold cathode tube is the same and the luminance is kept uniform. It is common. When an area light type planar light source using LEDs is used, a configuration is adopted in which a series unit in which a plurality of LED elements are connected in series is connected in parallel so that the luminance of each series unit is the same and the luminance is kept uniform. It is common.

  In the present embodiment, any of them can be adopted. However, in terms of luminance, the area light method with relatively high light utilization efficiency is preferable because a backlight with high luminance can be realized. On the other hand, on the side of thickness, in the case of the area light method, the thickness is increased, and when a reduction in thickness is required, it is preferable to adopt the edge light method. By the way, in terms of luminance unevenness and chromaticity unevenness (collectively referred to as display unevenness) due to deterioration or failure of the illuminator, the area light method is more easily recognized than the edge light method. .

  In any method, the light for illuminating the panel has non-uniformity, which is particularly remarkable when a flat light emitting element is not used. The non-uniformity of the light of the backlight unit 400 affects the display quality of the liquid crystal display device. Specifically, the non-uniformity of the light appears as uneven brightness and hue, and becomes more noticeable as the panel size increases. In the present embodiment, the diffusion plate 402 is used as a countermeasure to make the light uniform. Although not shown, in addition to the diffusion plate 402, for example, between the diffusion plate 402 and the liquid crystal panel, a diffuser plate, a prism sheet, etc. Provide an optical sheet.

  FIG. 3 shows a configuration example in the case where a direct system using a plurality of cold-cathode tubes as an illuminating body is adopted as luminance priority. For lighting a backlight using a cold-cathode tube, for example, a high frequency of about several tens to several hundreds KHz and a high voltage of about 500 to 1.5 KVp-p are necessary. Uses a configuration that uses a highly efficient inverter circuit. Specifically, as illustrated, the backlight unit 400 of the present embodiment includes a backlight driving unit 420 including a plurality of cold cathode tubes 410 and inverter units 424 as main components. As shown in FIG. 3A, each cold cathode tube 410 has its longitudinal direction in the horizontal scanning direction in order to effectively realize the luminance maintenance control for the illuminator abnormality (in this example, the abnormality of the cold cathode tube 410). It is arranged in parallel with each other and has a structure in which a plurality of them are arranged in the vertical direction.

  As shown in FIG. 3 (2), a sinusoidal voltage is applied to the cold cathode tube 410 from the backlight driving unit 420. As a result, a sine wave current flows through the cold cathode tube 410. At this time, if all the cold-cathode tubes 410 are driven with a sine wave of the same polarity, interference with the drive circuit of the liquid crystal display panel occurs, and interference fringe noise is generated on the liquid crystal display panel. In order to avoid this problem, the backlight unit 400 of the present embodiment divides the cold-cathode tubes 410 into a plurality of groups and has high-phase sine waves of different phases (typically divided into two groups and opposite in polarity). Drive with voltage. Therefore, as the inverter unit 424 of the backlight driving unit 420, for example, an odd-numbered cold-cathode tube 410_o is driven with a positive and high-voltage output while an inverter circuit is provided for each cold-cathode tube 410. The cathode tube 410_e is driven with a negative high voltage output.

  Further, the backlight unit 400 of the present embodiment also has a light control function for adjusting the backlight luminance. The dimming function is a function for supplying a voltage to the cold cathode tube 410, which is an example of an illuminating body, to emit light and to change the luminance of the emitted light. In realizing the dimming function, a voltage dimming method, duty Various mechanisms such as a dimming method (also called a burst dimming method or a chopper control method), a current dimming method, or a method in which these are arbitrarily combined can be employed.

  For example, the backlight driving unit 420 includes a dimming unit 422 that adjusts the DC input voltage VBL, and a high-frequency voltage of several tens to several hundreds KHz in the cold cathode tube 410 based on the adjustment voltage Vadj adjusted by the dimming unit 422. Inverter section 424 and control transistor 426 are provided.

  The dimmer 422 adjusts the DC input voltage VBL by, for example, turning on / off a transistor (not shown) and controlling the pulse width, and supplies the adjusted voltage Vadj to the inverter 424.

  The inverter unit 424 may use a known high-frequency oscillation circuit using an oscillation transformer. For example, a cold cathode tube 410 is arranged on the secondary winding side of the oscillation transformer, and a resonance circuit is formed by a primary winding of the oscillation transformer, a parallel capacitor, and a pair of oscillation transistors connected in series to drive them, A feedback winding is formed for the secondary winding of the oscillation transformer. Then, a positive feedback is applied to the base of the oscillation transistor by a feedback winding to alternately turn on / off the pair of oscillation transistors to oscillate a high frequency, and a high frequency voltage obtained thereby is supplied to the cold cathode tube 410.

  Here, when the voltage dimming method is adopted, the dimming unit 422 is supplied to the inverter unit 424 by controlling the base voltage of the transistor (voltage control transistor 426a) that forms a voltage source according to the lamp voltage variable signal. Dimming is achieved by adjusting the adjustment voltage Vadj. The adjustment voltage Vadj is decreased to lower the lamp luminance, and conversely, the adjustment voltage Vadj is increased to increase the lamp luminance. It should be noted that if the adjustment voltage Vadj is excessively decreased, the cold cathode tube 410 cannot be turned on, and if the adjustment voltage Vadj is excessively increased, the life is shortened. For this reason, the adjustment voltage Vadj for obtaining the normal brightness is set to 100%, and the lamp brightness is adjusted to be lowered in a range where the lamp can be lit.

  Further, when adopting the duty dimming method, the dimming unit 422 performs on / off control of the transistor for PWM control (switching transistor 426b) according to the duty signal while monitoring and maintaining the adjustment voltage Vadj. Thus, a supply period and a non-supply period are formed in the adjustment voltage Vadj supplied to the inverter unit 424, and the lamp luminance is controlled by controlling the ratio between the period during which the cold cathode tube 410 is lit and the period during which it is turned off. The lamp brightness is lowered by extending the non-supply period (that is, the light extinction period), and conversely, the lamp brightness is increased by increasing the supply period (that is, the lighting period). Note that if the extinction period is excessively long, continuous lamp lighting cannot be maintained. For this reason, the normal luminance is obtained when the duty (= lighting period / (lighting period + light-out period) is 100%, and the duty is adjusted in the direction of decreasing the lamp luminance within a range in which the lamp can be lit.

  When the current dimming method is adopted, the dimming unit 422 supplies the inverter 424 from the power source by controlling the base voltage of the transistor (current control transistor 426c) that forms the current source in accordance with the lamp current variable signal. In other words, the lamp current Ilamp flowing through the cold cathode tube 410 is adjusted. The lamp current Ilamp is decreased to lower the lamp brightness, and conversely, the lamp current Ilamp is increased to increase the lamp brightness. It should be noted that if the lamp current Ilamp is excessively lowered, the cold cathode tube 410 cannot be turned on, and if the lamp current Ilamp is excessively increased, the lifetime is reduced. For this reason, the lamp current Ilamp capable of obtaining the normal brightness is set to 100%, and the lamp brightness is adjusted in a direction in which the lamp brightness can be reduced within a range in which the lamp can be maintained.

<Abnormality detection of lighting object>
Further, the backlight unit 400 of the present embodiment adopts a configuration in which each cold cathode tube 410 is individually driven, and monitors the increase or decrease of the lamp current flowing through each cold cathode tube 410 to individually detect abnormalities in the illuminating body. An illuminator abnormality detection unit 440 for detection is provided.

  Whether the illuminating body is a phosphor such as a cold cathode tube 410 or an LED, it may not be lit normally due to the occurrence of an abnormality due to aged deterioration, in addition to the initial failure. The illuminator abnormality detection unit 440 detects an abnormality of the illuminator. Although the method for detecting an abnormality differs depending on what the illuminating body is, it can be broadly classified into a current detection method, a voltage detection method, and other methods. Any of them can be adopted. In the current detection method, the current flowing through the illuminating body is monitored directly or indirectly using a current detection resistor or the like, and compared with a reference current to determine whether or not there is an abnormality. In the voltage detection method, the voltage applied to the illuminator is directly or indirectly monitored, and compared with a reference voltage to determine whether or not there is an abnormality. As another method, for example, when the illuminating body is a phosphor, a detection coil (copper foil pattern or the like) for detecting the presence or absence of corona discharge may be arranged in the vicinity of the phosphor or the transformer. It is determined whether the phosphor is abnormal based on the presence or absence of discharge. As other methods, various methods other than the method of detecting the presence or absence of corona discharge are known, but the description thereof is omitted here.

  FIG. 3B shows a configuration example in which the illuminator abnormality detection unit 440 employs a current detection method when the illuminator is a cold cathode tube 410. The illuminator abnormality detection unit 440 includes a current detection resistor 442 and an abnormality determination unit 444 arranged on the current feedback side terminal of the cold cathode tube 410. The abnormality determination unit 444 monitors a voltage that can be generated at both ends of the current detection resistor 442, and determines that there is an abnormality in the cold cathode tube 410 when the voltage is not within a normal range. For example, the abnormality determination unit 444 detects a spike voltage generated at both ends of the current detection resistor 442 when an abnormal current due to a high-voltage discharge flows through the cold cathode tube 410 and compares it with a reference voltage to determine whether or not there is an abnormality. When it is abnormal, the abnormality detection signal DET_NG is notified to the control / supervisory unit 500. Alternatively, the abnormality determination unit 444 notifies the abnormality detection signal DET_NG to the control / supervision unit 500 when the cold cathode tube 410 is not lit and no voltage is generated across the current detection resistor 442.

<Illuminance distribution and viewing luminance distribution>
FIG. 4 shows the uneven illuminance distribution of a planar light source that irradiates a display panel when light emission of a certain illuminator is stopped, and uneven viewing luminance distribution that can occur in a display abnormal region T_NG in the display panel due to the uneven illuminance distribution. It is a figure explaining the relationship of the situation. FIG. 5 is a diagram for explaining a distribution state of viewing luminance reduction for each illuminating body stored in the luminance reduction distribution storage unit 512.

  As shown on the left side in FIG. 4, a plurality of cold-cathode tubes 410 are arranged at predetermined intervals in the vertical scanning direction, and a diffusion plate 402 is disposed on the display panel side to form a planar light source. Has been. The diffusing plate 402 forms a planar light source that irradiates the display panel with a composite component of illumination light emitted from each cold cathode tube 410, and makes the illuminance distribution of the planar light source uniform.

  As shown in FIG. 4A, when all the cold-cathode tubes 410 emit light normally and at substantially the same illuminance level due to the presence of the diffusion plate 402, the illuminance distribution on the display panel side is As shown in the center, the level is substantially uniform at level L_1. Microscopically, it cannot be denied that there is some uneven illuminance, but this component is ignored here. As a result, when the same pixel signal is supplied to each pixel cell 30 of the pixel array unit 3, as shown on the right side in the figure, basically, there is no display unevenness (brightness unevenness), and the level is almost level. It is uniform at Y_1.

  On the other hand, as shown in FIG. 4B, for example, the fourth cold cathode tube 410 (abnormal cold cathode tube 410_NG) from the top is abnormal and does not emit light, and the remaining cold cathode tubes 410 are normal and identical. When light is emitted at the illuminance level, the illumination light of the planar light source has an illuminance level at the portion corresponding to the abnormal cold cathode tube 410_NG, even if the diffusion plate 402 is present, as shown in the center of the figure. The level L_1 is not reached and the illuminance unevenness occurs slightly. As a result, when the same pixel signal is supplied to each pixel cell 30 of the pixel array unit 3, as shown on the right side of the drawing, the viewing luminance is level Y_1 in the portion corresponding to the abnormal cold cathode tube 410_NG. The brightness will be slightly reduced and uneven brightness will occur.

  The degree of decrease in the level of illumination light and viewing luminance at the abnormal cold cathode tube 410_NG is related to the emission luminance and radiation angle of each cold cathode tube 410 and the diffusion efficiency of the diffusion plate 402. Can be specified at the design stage. The control / supervisory unit 500 reduces the viewing luminance level in the portion of the abnormal cold cathode tube 410_NG based on the degree of the viewing luminance level reduction specified at the time of design. Correction is performed by increasing Vsd, correcting the curve of the reference gamma voltage Vγ by the gradation reference voltage generating unit 200, increasing the output image signal Vsout by the level converting unit 310, and adjusting the backlight luminance by the backlight unit 400.

  In addition, it cannot be denied that the degree of decrease in the level of illumination light and viewing luminance in the portion of the abnormal cold cathode tube 410_NG depends on each device and the characteristics over time. In order to deal with this, a luminance reduction distribution storage unit 512 is provided, and as shown in FIG. 5, the cold cathode tubes 410 (shown only for 410_1 to 410_6 in the figure) one by one in a non-light-emitting state one by one. The distribution state of the viewing luminance decrease due to the decrease in the illumination light level at the time of occurrence is measured for each cold cathode tube 410, and the measurement result for each cold cathode tube 410 is stored in the luminance decrease distribution storage unit 512 to reduce the luminance. A mechanism for referring to the stored information at the time of correction may be adopted. In FIG. 5, an illuminance distribution K is a measurement result of the luminance distribution when the cold cathode tube 410_k is in a non-light emitting state.

  In acquiring the luminance distribution to be stored in the luminance decrease distribution storage unit 512, a known sensor is used when the same pixel signal is supplied to each pixel cell 30 and light emission of a certain cold cathode tube 410 is stopped. Then, the distribution of viewing luminance over the entire panel may be measured. As an example, a measurement technique similar to the mechanism described in Patent Document 1 may be applied.

<Luminance maintenance control method for illuminant abnormality: Basic principle>
FIG. 6 is a diagram for explaining the basic principle of the luminance maintenance control method for an illuminant abnormality.

  The first luminance maintenance control method shown in FIG. 6 (1) is applied only to the display abnormal region T_NG corresponding to the abnormal cold cathode tube 410_NG as in the corrected luminance distribution COMP_1 shown in the center of FIG. 6 (1). On the other hand, any one or any combination of the source power supply voltage Vsd, the reference gamma voltage Vγ curve, the input / output relationship of the image signal, and the backlight luminance is corrected in the direction in which the viewing luminance increases.

  In this way, the corrected viewing luminance distribution Y_2 shown on the right side of FIG. 6 (1) is a combination of the illuminance distribution L_1 and the corrected luminance distribution COMP_1 in the state corresponding to the abnormal cold cathode tube 410_NG where the illuminance decreases. The luminance drop at the portion corresponding to the abnormal cold cathode tube 410_NG is corrected. Although the figure shows the case where the correction amount is insufficient, if the correction is complete, it becomes the same as the normal viewing luminance distribution Y_1 shown in FIG.

  On the other hand, the second luminance maintenance control method shown in FIG. 6 (2) first corresponds to the abnormal cold cathode tube 410_NG as in the first corrected luminance distribution COMP_1 shown second from the left in FIG. 6 (2). The display power source voltage Vsd, the reference gamma voltage Vγ curve, and the input of the image signal are applied to the entire panel in the direction in which the viewing luminance increases so that the display abnormal region T_NG to be displayed is substantially the same as the original viewing luminance. Any one or at least one of the output relation and the backlight luminance is corrected. Further, as shown in the second corrected luminance distribution COMP_2 shown second from the right in FIG. 6 (2), the display abnormal region T_NG that would be higher than the original viewing luminance due to the first correction is excluded. For the normal display area T_OK, the source power supply voltage Vsd, the reference gamma voltage Vγ curve, and the rest of the input / output relationship of the image signal in the direction of decreasing the viewing brightness (not used for the corrected brightness distribution COMP_1 1), any one of the backlight luminances or any combination thereof is corrected.

  By doing so, the corrected viewing luminance distribution Y_2 shown on the right side of FIG. 6B is the illuminance distribution L_1 in the state corresponding to the abnormal cold cathode tube 410_NG and the first corrected luminance distribution COMP_1. And the second corrected luminance distribution COMP_2 is combined, and the luminance drop at the portion corresponding to the abnormal cold cathode tube 410_NG is corrected. Although the figure shows the case where the correction amount is insufficient, if the correction is complete, it becomes the same as the normal viewing luminance distribution Y_1 shown in FIG.

  Since the first luminance maintenance control method corrects the source output voltage Vsource that drives the pixel cell 30 only for the display abnormality region T_NG, there is an advantage that the control is easier than the second luminance maintenance control method. On the other hand, the second luminance maintenance control method corrects the source output voltage Vsource not only for the display abnormal region T_NG but also for the normal display region T_OK, so that the control is more complicated than the first luminance maintenance control method. Since control of backlight luminance can also be applied, there is an advantage that the degree of freedom of control is increased.

<Luminance Maintenance Control Method for Illuminant Abnormality: First Embodiment>
FIG. 7 is a diagram for explaining a first embodiment of a luminance maintenance control method for an illuminant abnormality. The luminance maintenance control method according to the first embodiment is characterized in that a viewing luminance maintenance measure is taken when an abnormality occurs in the cold cathode tube 410 by changing the source power supply voltage Vsd by the source voltage supply power supply unit 100. Have. In order to facilitate understanding, including other embodiments to be described later, it will be described as a monochrome (monochrome) liquid crystal display panel unless otherwise specified.

  For example, when the first luminance maintenance control method is adopted, the control / supervisory unit 500 controls the source voltage supply power supply unit 100 when receiving an abnormality detection signal DET_NG from a lighting object abnormality detection unit 440 for a certain cold cathode tube 410. Thus, in the portion corresponding to the display abnormal region T_NG in the vertical scanning, the corrected luminance distribution COMP_1 is obtained by raising the source power supply voltage Vsd by a predetermined amount from the normal level.

  Alternatively, in the case of adopting the second luminance maintenance control method, when the overall viewing luminance level is increased, the control / supervision unit 500 sends the abnormality detection signal DET_NG to the illuminant abnormality detection unit 440 for a certain cold cathode tube 410. From the above, by controlling the source voltage supply power supply unit 100, the first corrected luminance distribution COMP_1 is obtained by raising the source power supply voltage Vsd by a predetermined amount from the normal level for the entire vertical scanning. Further, when the viewing brightness level of the normal display area T_OK is lowered, the second corrected brightness distribution is obtained by reducing the source power supply voltage Vsd by a predetermined amount from the normal level in the portion corresponding to the normal display area T_OK of the vertical scanning. Make COMP_2 available.

  The source power supply voltage Vsd is supplied not only to the source driver unit 6 but also to the gradation reference voltage generation unit 200. When the source power supply voltage Vsd is changed, the reference gamma voltage Vγ generated by the gradation reference voltage generation unit 200 is changed. A curve (for example, an output level change with respect to an input gradation level 0 to 255) changes. As a result, the source output voltage Vsource for driving the pixel cell 30 changes, and the viewing luminance level is adjusted.

  Specifically, as shown in FIG. 7A (1-1), when the source power supply voltage Vsd before the change is Vsd_0 and the source power supply voltage Vsd after the change to the rising side is Vsd_1, the input gradation levels 0 to 255 are obtained. In contrast, the γ curve (gradation curve) set in the range of 0 to Vsd_0 is set in the range of 0 to Vsd_1 after adjustment. As a result, after the adjustment, as shown in FIG. 7 (1-2), the source output voltage Vsource with respect to the same output image signal Vsout (that is, the same input image signal Vsin) increases and the luminance level rises. Further, as shown in FIG. 7 (2-1), when the source power supply voltage Vsd after the change to the lower side is Vsd_2, the γ curve is set in the range of 0 to Vsd_2 after the adjustment. As a result, after the adjustment, as shown in FIG. 7 (2-2), the source output voltage Vsource with respect to the same output image signal Vsout (that is, the same input image signal Vsin) is reduced, and the luminance level is lowered.

  As described above, according to the luminance maintenance control method of the first embodiment, the presence or absence of an abnormality in the cold cathode tube 410 is monitored by the illuminator abnormality detection unit 440, which is fed back to supply the source voltage. Since the viewing luminance is controlled by adjusting the source power supply voltage Vsd by the power supply unit 100, the viewing luminance almost the same as that of the other normal display areas T_OK in the portion of the abnormal cold cathode tube 410_NG with respect to the same input image signal Vsin. By adjusting the level, the display screen of the liquid crystal display panel can be made uniform.

  In the above description, the monochrome liquid crystal display panel has been described. However, in the case of a color liquid crystal display panel, for example, color separation of R (red), G (green), and B (blue) is performed. A filter (a collection thereof is referred to as a color filter) is arranged on the display surface side by aligning the position of each color of the color separation filter with the position of the pixel cell 30. Here, focusing on the relationship between the source output voltage Vsource in the liquid crystal display panel and the transmittance of the illumination light emitted from the backlight unit 400, the amount of light transmitted from the liquid crystal display panel is the source output applied to the pixel cell 30. Controlled by voltage Vsource. In the case of a color liquid crystal display panel, there is a shift in the transmittance curve of each color of R, G, B. If the driving considering the deviation of the transmittance curve is not performed, the white balance is lost and the hue unevenness is visually recognized. Therefore, when the source power supply voltage Vsd is adjusted in the case of color display support, the control of the source power supply voltage Vsd in consideration of the deviation of the transmittance curve of each color of R, G, and B (the control of the source output voltage Vsource as the adjustment result). It is good to keep in mind that white balance is not lost by controlling viewing brightness for each color. The point of preventing the white balance from being lost is the same in other embodiments described later.

<Luminance Maintenance Control Method for Illuminant Abnormality: Second Embodiment>
FIG. 8 is a diagram for explaining a second embodiment of the luminance maintenance control method for abnormal illumination. The brightness maintenance control method of the second embodiment is to take measures to maintain viewing brightness when an abnormality occurs in the cold cathode tube 410 by adjusting the curve of the reference gamma voltage Vγ by the gradation reference voltage generation unit 200. Has characteristics.

  For example, when the first luminance maintenance control method is adopted, the control / supervisory unit 500 controls the gradation reference voltage generation unit 200 when receiving the abnormality detection signal DET_NG from the illuminant abnormality detection unit 440 for a certain cold cathode tube 410. Thus, in the portion corresponding to the display abnormality region T_NG in the vertical scanning, the correction luminance distribution COMP_1 is obtained by increasing the rate of change of the curve of the reference gamma voltage Vγ above the normal level.

  Further, in the case of adopting the second luminance maintenance control method, when increasing the overall viewing luminance level, the control / supervision unit 500 sends the abnormality detection signal DET_NG to the illuminant abnormality detection unit 440 for a certain cold cathode tube 410. The first reference luminance distribution COMP_1 is obtained by controlling the gradation reference voltage generation unit 200 so that the change rate of the curve of the reference gamma voltage Vγ is larger than the normal level for the entire vertical scanning. To. Further, in the case of adopting the second luminance maintenance control method, when the viewing luminance level of the normal display region T_OK is reduced, the rate of change of the curve of the reference gamma voltage Vγ in the portion corresponding to the normal display region T_OK of vertical scanning Is made smaller than the normal level to obtain the second corrected luminance distribution COMP_2. As a result, the pixel cell 30 is changed by changing the curve of the reference gamma voltage Vγ generated by the gradation reference voltage generation unit 200 (for example, a curve indicating an output level change with respect to the input gradation levels 0 to 255). The source output voltage Vsource for driving is changed, and the viewing luminance level is adjusted.

  Specifically, as shown in FIG. 8 (1-1), if the reference gamma voltage Vγ before change is Vγ_0, and the reference gamma voltage Vγ having a larger change rate is Vγ_1, The curve of Vγ_0 (gradation curve) in the range of 0 to Vsd_0 is set, but after the adjustment, the curve of Vγ_1 is set in the range of 0 to Vsd_0. As a result, after the adjustment, as shown in FIG. 8 (1-2), the source output voltage Vsource with respect to the same output image signal Vsout (that is, the same input image signal Vsin) increases and the luminance level rises. Further, as shown in FIG. 8 (2-1), when the reference gamma voltage Vγ with a small change rate is Vγ_2, the curve of Vγ_2 is in the range of 0 to Vsd_0 after adjustment with respect to the input gradation level 0 to 255. Will come to set. As a result, after the adjustment, as shown in FIG. 8 (2-2), the source output voltage Vsource with respect to the same output image signal Vsout (that is, the same input image signal Vsin) is reduced, and the luminance level is lowered.

  However, in the case of the curve of the reference gamma voltage Vγ_1 with the increased rate of change, the curve of Vγ_1 is set in a range larger than 0 to Vsd_0. In practice, however, the gamma correction unit of the source driver unit 6 uses the source The gamma correction cannot be performed beyond the power supply voltage Vsd_0, and the influence mainly appears on the high luminance side where the input gradation level is large. Specifically, as shown in FIG. 8 (3), it is impossible to represent a gradation change in a high luminance part (for example, gradation level 230 or later) having a large input gradation level. Therefore, for example, as shown in FIG. 8 (4), the gradation reference voltage generation unit 200 has an input gradation level between a little before the output gradation becomes 255 (for example, the input gradation level 210) to 255. It is preferable that an output level change is obtained in accordance with the change (gradation levels 210 to 255).

  As described above, according to the luminance maintenance control method of the second embodiment, the presence or absence of abnormality in the cold cathode tube 410 is monitored by the illuminator abnormality detection unit 440, which is fed back to the gradation reference voltage. Since the viewing luminance is controlled by adjusting the curve of the reference gamma voltage Vγ_1 by the generation unit 200, the abnormal cold cathode tube 410_NG can be applied to the same input image signal Vsin as in the first embodiment. The display screen of the liquid crystal display panel can be made uniform by adjusting the viewing brightness level to substantially the same as the normal display area T_OK.

<Luminance Maintenance Control Method for Illuminant Abnormality: Third Embodiment>
FIG. 9 is a diagram for explaining a third embodiment of the luminance maintenance control method for abnormal illumination. In the luminance maintenance control method of the third embodiment, the level conversion unit 310 of the timing controller unit 300 adjusts the input / output relationship of image signals, thereby taking measures to maintain viewing luminance when an abnormality occurs in the cold cathode tube 410. Characterized by points.

  For example, when the first luminance maintenance control method is adopted, the control / supervisory unit 500 receives the abnormality detection signal DET_NG for a certain cold cathode tube 410 from the illuminant abnormality detection unit 440, thereby controlling the level conversion unit 310. In the portion corresponding to the display abnormal region T_NG in the vertical scanning, the corrected luminance distribution COMP_1 is obtained by making the output image signal Vsout larger than the input image signal Vsin.

  Further, in the case of adopting the second luminance maintenance control method, when increasing the overall viewing luminance level, the control / supervision unit 500 sends the abnormality detection signal DET_NG to the illuminant abnormality detection unit 440 for a certain cold cathode tube 410. The first correction luminance distribution COMP_1 is obtained by controlling the level conversion unit 310 so that the output image signal Vsout is larger than the input image signal Vsin for the entire vertical scanning. Further, when the viewing luminance level of the normal display area T_OK is lowered, the output image signal Vsout is made smaller than the input image signal Vsin in the portion corresponding to the normal display area T_OK of the vertical scanning. A corrected luminance distribution COMP_2 is obtained. By changing the input / output relationship of the image signal so that the output image signal Vsout generated by the level conversion unit 310 is larger or smaller than the input image signal Vsin, the reference gamma by the gradation reference voltage generation unit 200 is changed. The same effect as the adjustment of the curve of the voltage Vγ_1 is obtained. As a result, the source output voltage Vsource for driving the pixel cell 30 is changed, and the viewing luminance level is adjusted.

  Specifically, as shown in FIG. 9 (1-1), the characteristic line indicating the input / output relationship before the change is IO_0, and the changed characteristic line IO_1 is the output image signal Vsout rather than the input image signal Vsin. By making the value larger, the input gradation level that abuts against the γ curve generated by the gradation reference voltage generation unit 200 is increased in advance. As a result, even if the source power supply voltage Vsd and the γ curve are not adjusted, the source output voltage corresponding to the same input image signal Vsin is adjusted as shown in FIG. Vsource increases and the brightness level increases. Also, as shown in FIG. 9 (2-1), the changed characteristic line IO_2 causes the gradation reference voltage generation unit 200 to make the output image signal Vsout smaller than the input image signal Vsin. The input gradation level that abuts the γ curve to be generated is previously reduced. As a result, even if the source power supply voltage Vsd and the γ curve are not adjusted, the source output voltage corresponding to the same input image signal Vsin is adjusted as shown in FIG. Vsource decreases and the luminance level decreases.

  However, in the case of the characteristic line IO_1 in which the output image signal Vsout is larger than the input image signal Vsin, the characteristic line IO_1 is set in a range larger than 0 to Vsd_0. The gamma correction unit of the driver unit 6 cannot perform gamma correction exceeding the source power supply voltage Vsd_0, and its influence mainly appears on the high luminance side where the input gradation level is large. Specifically, as shown in FIG. 9 (3), it is impossible to represent a gradation change in a high luminance part (for example, gradation level 230 or later) having a large input gradation level. Therefore, for example, as shown in FIG. 9 (4), the gradation reference voltage generation unit 200 has an input gradation level between a little before the output gradation becomes 255 (for example, the input gradation level 210) to 255. It is preferable that an output level change is obtained in accordance with the change (gradation levels 210 to 255).

  As described above, according to the luminance maintenance control method of the third embodiment, the presence / absence of abnormality in the cold cathode tube 410 is monitored by the illuminator abnormality detection unit 440, which is fed back to the level conversion unit 310. Since the viewing luminance is controlled by adjusting the input / output characteristics of the image signal according to the same manner as in the first embodiment, other display normals are performed even in the abnormal cold cathode tube 410_NG portion for the same input image signal Vsin. The display screen of the liquid crystal display panel can be made uniform by adjusting the viewing luminance level to be substantially the same as that of the region T_OK.

<Luminance Maintenance Control Method for Illuminant Abnormality: Fourth Embodiment>
FIG. 10 is a diagram for explaining a fourth embodiment of the luminance maintenance control method for abnormal illumination. The brightness maintenance control method according to the fourth embodiment is characterized in that the viewing brightness maintenance measure when an abnormality occurs in the cold cathode tube 410 is performed by adjusting the backlight brightness by the dimming unit 422 of the backlight unit 400. Have Note that the adjustment of the backlight luminance cannot be applied to the abnormal cold cathode tube 410_NG as a matter of course, so that only the second luminance maintenance control method can be used in practice.

  For example, in the case of adopting the second luminance maintenance control method, when increasing the overall viewing luminance level, the control / supervision unit 500 sends the abnormality detection signal DET_NG to the illuminant abnormality detection unit 440 for a certain cold cathode tube 410. From the above, by controlling the light control unit 422, the backlight luminance is increased from the normal level for the entire vertical scanning so that the first corrected luminance distribution COMP_1 is obtained. Further, when the viewing luminance level of the normal display area T_OK is reduced, the second corrected luminance distribution COMP_2 is obtained by reducing the backlight luminance below the normal level in the portion corresponding to the normal display area T_OK of the vertical scanning. To be able to. Since the so-called brightness is adjusted by changing the backlight luminance to be larger or smaller than the normal level, the source output voltage Vsource for driving the pixel cell 30 is the same as a result. Also, the viewing luminance level is adjusted.

  Specifically, as shown in FIG. 10A, the backlight unit 400 (specifically, a normal cold cathode tube 410 in detail) with respect to the gradation characteristic line G_0 of the viewing luminance in the state of the backlight luminance before the change. ) Is controlled so as to increase the light emission luminance (backlight luminance). As a result, even if the source power supply voltage Vsd and the γ curve are not adjusted, the gradation characteristic line G_1 after the adjustment of the backlight luminance is the same as the input image signal Vsin (input floor) as shown in FIG. The viewing luminance level with respect to the tone level) increases. Further, as shown in FIG. 10B, when the light emission luminance (backlight luminance) output from the backlight unit 400 (specifically, the normal cold cathode tube 410) is controlled to be low, the source power supply voltage Vsd and γ Even without adjusting the curve, the viewing luminance level for the same input image signal Vsin (input gradation level) of the gradation characteristic line G_2 after adjusting the backlight luminance decreases.

  As described above, according to the luminance maintenance control method of the fourth embodiment, the presence or absence of abnormality in the cold cathode tube 410 is monitored by the illuminator abnormality detection unit 440, which is fed back to the backlight unit 400. Since the viewing luminance is controlled by adjusting the backlight luminance by the dimming unit 422, other abnormal cold cathode tube 410_NG is also used for the same input image signal Vsin as in the first embodiment. The display screen of the liquid crystal display panel can be made uniform by adjusting the viewing luminance level to substantially the same as the normal display area T_OK.

It is a figure which shows the outline of the whole structure of one Embodiment of a liquid crystal display device. It is a figure explaining the detail of a power generation part. It is a figure explaining the detail of a backlight part. It is a figure explaining the illuminance distribution nonuniformity of the planar light source at the time of light emission stop of an illuminating body, and the situation of viewing-and-listening luminance distribution nonuniformity in the display panel resulting from this nonuniformity of illuminance. It is a figure explaining the distribution condition of the viewing-and-listening brightness fall for every lighting body memorize | stored in a brightness fall distribution memory | storage part. It is a figure explaining the basic principle of the brightness | luminance maintenance control method with respect to illumination body abnormality. It is a figure explaining 1st Embodiment of the brightness | luminance maintenance control method with respect to illumination body abnormality. It is a figure explaining 2nd Embodiment of the brightness | luminance maintenance control method with respect to illumination body abnormality. It is a figure explaining 3rd Embodiment of the brightness | luminance maintenance control method with respect to illumination body abnormality. It is a figure explaining 4th Embodiment of the brightness | luminance maintenance control method with respect to illumination body abnormality.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 2 ... Board | substrate, 3 ... Pixel array part, 6 ... Source driver part, 5 ... Gate driver part, 9 ... Display brightness control part, 12 ... Vertical scanning line, 14 ... Horizontal scanning line, 30 ... Pixel Cell ... 32 ... Liquid crystal element 100 ... Source voltage supply power supply unit 102 ... Power supply generation unit 110 ... Switching drive unit 200 ... Tone reference voltage generation unit 300 ... Timing controller unit 310 ... Level conversion unit 320 ... Timing generator section, 400 ... Backlight section, 410 ... Cold cathode tube, 420 ... Backlight drive section, 422 ... Dimming section, 500 ... Control / supervision section, 512 ... Brightness reduction distribution storage section

Claims (9)

A display panel comprising a plurality of pixel cells and displaying an image based on an input image signal;
An illumination unit comprising a plurality of illumination bodies and illuminating the display panel;
A horizontal scanning unit for sending a video signal to each pixel cell of the display panel;
A vertical scanning unit that vertically scans each pixel cell of the display panel;
A power supply unit for supplying a power supply voltage to the horizontal scanning unit;
When an abnormality occurs in any one of the illumination units of the illumination unit and normal light emission cannot be obtained, the power supply unit is controlled to adjust the power supply voltage supplied to the horizontal scanning unit. The video signal sent to the pixel cell is adjusted, or the illumination unit adjusts the intensity of illumination light that illuminates the display panel, thereby controlling the viewing luminance of the entire display panel to be uniform. A display brightness control unit;
A display device comprising: The display luminance control unit stops light emission of the illuminating body in which the abnormality occurs when an abnormality occurs in any illuminating body of the illuminating unit and normal light emission cannot be obtained. The display device according to claim 1. The illuminating unit includes an illuminating body that individually emits a plurality of color components, and is a system that mixes light emitted from the illuminating bodies for each color to form white light,
The display brightness control unit, when an abnormality occurs in any of the illumination units of the illumination unit and normal light emission cannot be obtained, stops the light emission of the illumination unit in which the abnormality occurs and also emits white light. The display device according to claim 2, wherein light emission of another color component illuminating body paired with the illuminating body in which the abnormality has occurred for generation is also stopped. A luminance decrease distribution storage unit that stores distribution status of a viewing luminance decrease that may occur in a display abnormal region in the display panel when light emission of a certain illuminating body is stopped, for each illuminating body,
The display brightness control unit is configured to reduce the viewing brightness for each lighting body stored in the brightness reduction distribution storage unit when an abnormality occurs in any lighting body of the lighting unit and normal light emission cannot be obtained. The display device according to claim 1, wherein the control is performed with reference to a distribution state so that viewing brightness of the entire display panel is uniform. A gradation reference voltage generation unit that generates a reference gradation voltage defining a gradation curve and supplies the reference gradation voltage to the horizontal scanning unit;
A level conversion unit that converts an input image signal into an output image signal and supplies the output image signal to the horizontal scanning unit;
Further comprising
The gradation reference voltage generator adjusts the reference gradation voltage, or the level converter adjusts the correspondence relationship between the input image signal and the output image signal, so that the horizontal scanning unit The display device according to claim 1, wherein a video signal transmitted to the pixel cell is adjusted. The display brightness control unit is configured to increase the power supply voltage in a direction in which the viewing brightness of the display abnormality area corresponding to the illuminating body in which an abnormality has occurred in the display panel is increased to the same level as the viewing brightness before the occurrence of the abnormality. The control is performed so as to adjust at least one of the video signals, and a normal viewing brightness level is set for a normal display area other than the abnormal display area on the display panel. The display device according to 1. The display brightness control unit increases the viewing brightness of the display abnormality area corresponding to the illuminating body in which an abnormality has occurred in the display panel to a level that is the same as the viewing brightness before the occurrence of the abnormality. Is controlled so as to perform a first correction for adjusting at least one of the power supply voltage, the video signal, and the intensity of the illumination light, and the display panel other than the display abnormal region is displayed normally. With respect to the area, except for the power supply voltage, the video signal, and the intensity of illumination light to which the first correction has been applied in a direction that decreases to the same level as the viewing luminance before the occurrence of abnormality. The display device according to claim 1, wherein control is performed so as to perform a second correction for adjusting at least one of the two. The display luminance control unit performs control so as to perform the first correction by adjusting at least one of the intensity of the video signal and the illumination light, and adjusts the power supply voltage to adjust the first voltage. The display device according to claim 7, wherein the display device is controlled to perform correction of 2. A display panel that includes a plurality of pixel cells and displays an image based on an input image signal, an illumination unit that illuminates the display panel, a horizontal scanning unit that transmits a video signal to each pixel cell of the display panel, and the display In a method for adjusting the display quality of a display device comprising: a vertical scanning unit that vertically scans each pixel cell of a panel; and a power supply unit that supplies a power supply voltage to the horizontal scanning unit.
The power supply current consumed by the horizontal scanning unit is monitored, and when the monitored power supply current exceeds a predetermined determination level, the power supply unit is controlled to reduce the power supply voltage supplied to the horizontal scanning unit, and A display device that controls the video signal transmitted from the horizontal scanning unit to the pixel cell to be large, or controls the illumination unit to increase illumination light that illuminates the display panel. To adjust the display quality of the.

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