JP2008286854A - Light source device and liquid crystal display device - Google Patents

Abstract

A light receiving element of a sensor unit is prevented from being saturated before light amount detection, and detection accuracy at the time of light amount detection can be improved.
An illumination light sensor 13 serving as a light receiving element is connected to a sensor circuit (I / V conversion unit 14) at the time of light amount detection (detection lighting period) and at the time of non-detection (normal lighting period). The connection path of the illumination light sensor 13 is switched so that a potential difference in the opposite direction to the potential difference between both ends of the illumination light sensor 13 generated at the time of detection is generated. As a result, for example, even when all the partial lighting parts 4 near the detection region are turned on in the normal lighting state and then in the detection lighting state, the illumination light sensor 13 is saturated before the light amount is detected. Is prevented. Even if only the partial lighting unit 4 to be detected is turned on immediately after the normal lighting state, the detection operation can be performed with high accuracy and high response speed.
[Selection] Figure 6

Description

  The present invention relates to a light source device having a plurality of partial lighting units that can be controlled independently from each other, and a liquid crystal display device using such a light source device.

  In recent years, there has been a trend toward thinner displays as represented by liquid crystal TVs (televisions) and plasma displays (PDPs), and in particular, many mobile displays are liquid crystal systems with faithful colors. Reproducibility is desired. The backlight of the liquid crystal display panel is the CCFL (Cold Cathode Fluorescent Lamp) type using a fluorescent tube, but mercury-less has been required environmentally, and a light emitting diode (LED: LED: Light Emitting Diode) etc. are considered promising.

As a backlight device using such an LED, for example, those shown in Patent Documents 1 and 2 have been proposed. Here, the LED backlight device disclosed in Patent Document 1 is configured to change the luminance level of the entire backlight device according to the brightness of the surrounding environment by detecting external light. On the other hand, in Patent Document 2, the light source unit is divided into a plurality of partial lighting units (individual light emitting units) in order to improve the moving image response of the liquid crystal display panel, and the plurality of partial lighting units are sequentially turned on. An LED backlight device is disclosed.
JP 2006-145886 A JP 2006-243283 A

  By the way, in such an LED backlight device, the luminance variation of the illumination light can be suppressed by detecting the illumination light and feedback-controlling the light emission amount of the LED based on the detected value. In addition, in the case of an additive color mixing type backlight device that uses a plurality of types of LEDs such as a red LED, a green LED, and a blue LED and mixes a plurality of color lights to obtain specific color light, in addition to the luminance of illumination light, The variation of the chromaticity of the illumination light can be suppressed by a similar feedback system.

  Here, in a backlight device that performs a lighting operation using a plurality of partial lighting units, the following method can be considered as a method for performing feedback control of the light emission amount. Here, a case where a backlight device is applied to a transmissive liquid crystal display device and a partial lighting operation can be performed according to a video signal is considered. In the case of such a backlight device, ideally, it is preferable to individually detect the amount of light of each of the plurality of partial lighting units and feedback control the light emission amount of each partial lighting unit. However, since it is difficult to provide light receiving elements in all the partial lighting sections, a plurality of detection areas are set so that a predetermined number (for example, four) of partial lighting sections are included, and the light receiving elements are provided for each detection area. It is conceivable to detect the amount of light of a part of the partial lighting section for each detection region and to feedback control the light emission amount. In this case, in order to detect the accurate light quantity of each partial lighting part, only the partial lighting part to be detected is turned on so that light from other partial lighting parts does not enter, and the other parts are turned off. It is preferable.

  Such light amount detection for feedback control can be performed even in a state where normal video display is performed by the following method. For example, a short lighting period (detection lighting period) for performing light amount detection for a certain detection region is provided in the first period in the display period of one frame, and this period is only for the partial lighting part to be detected. Lights up. The period other than the detection lighting period in the display period of one frame is a period for performing normal video display based on the video signal (normal lighting period). In the normal lighting period, an arbitrary partial lighting portion is turned on according to a video to be displayed. For example, when white display is performed as a video display, a plurality of partial lighting portions are all turned on. By repeating the detection lighting state and the normal lighting state, the partial lighting parts in each detection area are sequentially lit during the detection lighting period with the normal lighting period in between, so that the light amount is detected for all the detection areas. It can be performed. That is, it is possible to detect the amount of light for all the detection areas while performing normal video display. Even when such lighting is performed, if the detection lighting period is set to a very short period, there is no influence on the video viewing.

  FIG. 17 shows a configuration example of a sensor unit for performing such light quantity detection. This sensor unit includes a photodiode 213 as a light receiving element that generates a current corresponding to the amount of light, and a sensor circuit 214 that generates a sensor output signal corresponding to the current generated in the photodiode 213. The sensor circuit 214 is a negative feedback circuit and includes an output terminal 80, a feedback capacitor 81, a feedback resistor 82, and an operational amplifier 83. The feedback capacitor 81 and the feedback resistor 82 are connected in parallel to the inverting input terminal and the output terminal of the operational amplifier 83. The anode A of the photodiode 213 is connected to one end of the feedback capacitor 81 and the feedback resistor 82 and the inverting input terminal (−) of the operational amplifier 83. The cathode K of the photodiode 213 is connected to the non-inverting input terminal (+) of the operational amplifier 83. An offset voltage V1 is applied to the non-inverting input terminal of the operational amplifier 83.

  The photodiode 213 is a PN junction semiconductor device, and an anode electrode is provided on the P layer side and a cathode electrode is provided on the N layer side. When the photodiode 213 is irradiated with light, an electron-hole pair is generated at the PN junction due to the light energy, and a reverse current corresponding to the amount of light is generated from the cathode to the anode when an external circuit (sensor circuit 214) is connected. It flows toward. The sensor circuit 214 has a function as an I / V conversion circuit, and outputs an output voltage Vout corresponding to the amount of light as a sensor output signal. FIG. 18 shows a characteristic example of the output voltage Vout by the sensor circuit 214. In the sensor circuit 214, if the resistance value of the feedback resistor 82 is Rf and the value of the current generated by the photodiode 213 and flowing through the feedback resistor 82 is Is, “− (Is × Rf) with reference to the offset voltage V1. ) "Is obtained.

  Here, as described above, in the method of detecting the light amount by alternately repeating the detection lighting state and the normal lighting state, in the detection lighting state, only the partial lighting part to be detected is lit, and the partial lighting part In order to detect only the light from the light, it is necessary to increase the light receiving area of the photodiode 213 to increase the sensitivity. On the other hand, for example, in the normal lighting state, when all the partial lighting parts in the vicinity of the detection region are turned on and then in the detection lighting state, before the light amount is detected, the photodiode 213 is compared with the light amount detection time. A large amount of light is incident. For this reason, due to the characteristics of the PN junction type semiconductor device, the photodiode 213 is saturated before the light amount is detected, and immediately after that, only the partial lighting part to be detected is turned on to perform the detection operation. However, since it takes a while for the photodiode 213 to return from the saturated state, sufficient sensitivity cannot be obtained during the detection lighting period, resulting in a defective detection operation and a decrease in detection accuracy. In particular, this tendency is remarkable when the sensitivity is increased by increasing the light receiving area in order to detect only light from a specific partial lighting section as described above.

  In order to solve this problem, for example, with the circuit configuration as shown in FIG. 19, it is conceivable to switch the gain of the sensor circuit 214 between normal lighting and light amount detection. In the circuit of FIG. 19, the feedback resistor 82 is configured with a first feedback resistor 82A (resistance value Rf1) and a second feedback resistor 82B (resistance value Rf2) having different resistance values from the circuit configuration of FIG. The gain switching is performed by switching the path in the sensor circuit 214 with the switching unit SW10. However, even if it is intended to cope with such gain switching, the problem of the detection operation failure cannot be solved because the photodiode 213 itself is saturated before the light amount detection.

  The present invention has been made in view of such problems, and its purpose is to prevent the light receiving element of the sensor unit from being saturated before performing light amount detection, and to improve detection accuracy during light amount detection. An object of the present invention is to provide a light source device and a liquid crystal display device which can be used.

  The light source device of the present invention is provided for each of a light source unit having a plurality of partial lighting units capable of controlling light emission independently of each other and a plurality of detection regions set to include two or more partial lighting units. A sensor unit that detects the amount of light when a part of the partial lighting unit in the detection area is lit, a normal lighting period in which a plurality of partial lighting units are lit according to an input signal, and a target of the light amount detection by the sensor unit The light source unit is driven so that the detection lighting period for lighting only the partial lighting part becomes mixed along the time axis, and the partial lighting part in each detection region is set in the detection lighting period across the normal lighting period. Light source driving means for sequentially lighting and light source control means for adjusting the light emission amount of the partial lighting portion based on the detection result of the sensor portion. In particular, the sensor unit generates a light-receiving element that generates a current corresponding to the amount of light from the partial lighting unit that is a target of light amount detection in the detection region, and a sensor output signal that corresponds to the current generated by the light-receiving element. The sensor circuit and the light receiving element are connected to the sensor circuit during the detection lighting period, and in the normal lighting period, a potential difference in the opposite direction to the potential difference between both ends of the light receiving element that occurs when detecting the amount of light is generated. And a path switching unit that switches a connection path of the light receiving elements.

  The liquid crystal display device of the present invention is a liquid crystal display device including a light source device that emits light and a liquid crystal display panel that modulates light emitted from the light source device based on a video signal. There are some which are constituted by the light source device.

  In the light source device or the liquid crystal display device of the present invention, a normal lighting period in which at least one partial lighting unit is turned on according to an input signal, and a detection lighting period in which only the partial lighting unit that is a target of light amount detection by the sensor unit is turned on. Are driven along the time axis, and the partial lighting portions in each detection region are sequentially lit during the detection lighting period with the normal lighting period interposed therebetween. In the sensor unit, the light path is connected to the sensor circuit when the light amount is detected (detection lighting period), and both ends of the light receiving element are generated when the light amount is detected when not detected (normal lighting period). The connection path of the light receiving elements is switched so that a potential difference in the opposite direction to the potential difference is generated. As a result, for example, even if the partial lighting part near the detection region is lit in the normal lighting state and then enters the detection lighting state, the light receiving element may be saturated before the light amount is detected. Is prevented. Even if the detection operation is performed by turning on only the partial lighting unit to be detected immediately after the normal lighting state, the detection operation with high accuracy and high response speed is possible.

  According to the light source device or the liquid crystal display device of the present invention, the light receiving element is connected to the sensor circuit at the time of light amount detection (detection lighting period), and light reception that occurs at the time of light amount detection at the time of non-detection (normal lighting period). Since the connection path of the light receiving element is switched so that a potential difference in the opposite direction to the potential difference between the two ends of the element is generated, the light receiving element of the sensor unit is prevented from being saturated before the light amount is detected. In addition, the detection accuracy at the time of detecting the light amount can be improved. Further, the present invention can be easily implemented without the need for providing a complicated control circuit for countermeasures against saturation of the light receiving element or preparing a complicated control algorithm in a portion other than the sensor unit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]

  FIG. 1 shows the overall configuration of a liquid crystal display device according to a first embodiment of the present invention. The liquid crystal display device 3 is a so-called transmissive liquid crystal display device that emits transmitted light as display light Dout. The backlight device 1 as a light source device according to the first embodiment of the present invention, and a transmissive liquid crystal display device. The liquid crystal display panel 2 is included.

  The liquid crystal display panel 2 includes a transmissive liquid crystal layer 20 and a pair of substrates sandwiching the liquid crystal layer 20, that is, a TFT (Thin Film Transistor) substrate 211 which is a substrate on the backlight device 1 side, and a substrate opposed thereto. And the polarizing plate 210 and 220 laminated on the opposite side of the liquid crystal layer 20 in the TFT substrate 211 and the counter electrode substrate 221. The TFT substrate 211 includes pixels in a matrix form, and each pixel is formed with a pixel electrode 212 including a driving element such as a TFT.

  The backlight device 1 is of an additive color mixing method that mixes a plurality of color lights (in this case, red light, green light, and blue light) to obtain illumination light Lout that is specific color light (in this case, white light). And a light source unit (a light source unit 10 to be described later) including a plurality of red LEDs 1R, a green LED 1G, and a blue LED 1B.

  2A, 2 </ b> B, and 3 illustrate an example of an arrangement configuration of each color LED in the backlight device 1. As shown in FIG. 2A, in this backlight device 1, unit cells 41 and 42 of the light emitting unit are formed by two sets of red LED 1R, green LED 1G and blue LED 1B, respectively, and these two unit cells 41, The partial lighting part 4 which is a unit unit of the light emission part is formed by 42. In addition, each color LED is connected in series in each unit cell and between the unit cells 41 and 42. Specifically, as shown in FIG. 2B, the anode and cathode of each color LED are connected.

  As shown in FIG. 3, for example, each partial lighting unit 4 configured in this way is arranged in a matrix in the light source unit 10 and can be controlled independently of each other as described later. The light emission amount) is controlled by PWM (Pulse Width Modulation) using a pulse signal. Further, on the light source unit 10, one illumination light sensor 13 is arranged for four partial lighting units 4 (for example, partial lighting units 4A to 4D). The illumination light sensor 13 receives light from the partial lighting unit 4 (illumination light Lout described later), and receives light from a region (detection region 40) corresponding to the arrangement region of the four partial lighting units 4. It can receive light.

  The illumination light sensor 13 constitutes a part of a sensor unit 7 (see FIGS. 4 to 7) described later. A plurality of detection areas 40 are provided, and each sensor area 7 including the illumination light sensor 13 is provided for each detection area 40. The number of partial lighting units 4 arranged in one detection region 40 is not limited to four, and may be set to a smaller number (for example, two) or a larger number (for example, six). . Details of the illumination light sensor 13 will be described later.

  It should be noted that the light amount detection in the present embodiment can be performed even in a state where normal video display is being performed. More specific control timing will be described later. For example, a short lighting period (detection lighting period) for detecting the amount of light for a certain detection area 40 is provided in the head period of the display period of one frame. During this period, control is performed so that only the partial lighting unit 4 to be detected is lit. In addition, a period other than the detection lighting period in the display period of one frame is a period for performing normal video display based on the video signal (normal lighting period). By repeating such a detection lighting state and a normal lighting state and sequentially lighting the partial lighting portions 4 in each detection region 40 during the detection lighting period with the normal lighting period interposed therebetween, all the detection regions 40 are detected. The amount of light can be detected. That is, it is possible to detect the light quantity for all the detection areas 40 while performing normal video display.

  Next, with reference to FIG. 4, the structure of the drive and control part of the liquid crystal display panel 2 and the light source unit 10 described above will be described in detail. FIG. 4 shows a block configuration of the liquid crystal display device 3. In FIG. 4 (and FIG. 5 described later), the illumination light sensor 13 is shown as being disposed in the vicinity of the light source unit 10 for convenience.

  As shown in FIG. 4, the driving circuit for driving the liquid crystal display panel 2 to display an image displays an X driver (data) that supplies a driving voltage based on the video signal to each pixel electrode 212 in the liquid crystal display panel 2. Driver) 51, a Y driver (gate driver) 52 that drives each pixel electrode 212 in the liquid display panel 2 along a scanning line (not shown), and timing control for controlling the X driver 51 and the Y driver 52. Unit (timing generator) 61, an RGB process processing unit 60 (signal generator) for processing an external video signal to generate an RGB signal, and a frame memory for storing the RGB signal from the RGB process processing unit 60 And a video memory 62.

  On the other hand, the part which performs the drive and control for the light source part 10 of the backlight apparatus 1 to perform lighting operation is the backlight drive part 11, the backlight control part 12, the illumination light sensor 13, and path | route switch part SW. The I / V conversion unit 14 and the A / D conversion unit 15 are included.

  The illumination light sensor 13 receives the illumination light Lout from the light source unit 10 (specifically, the partial lighting unit 4 in each detection region 40 as described above) and obtains a light reception signal. (In this case, red light sensor 13R that extracts red light from the mixed color light (in this case, white light) obtained by mixing red light, green light, and blue light and selectively receives the light, and green light It is composed of a green light sensor 13G that extracts and selectively receives light, and a blue light sensor 13B that extracts blue light and selectively receives it.

  The I / V conversion unit 14 performs I / V (current / voltage) conversion on the light reception signal for each color obtained by the illumination light sensor 13, and outputs light reception data that is an analog voltage signal for each color. Is.

  The path switching unit SW is configured to detect a plurality of partial lighting units 4 according to a video signal when detecting the amount of light (detection lighting period during which only the partial lighting unit 4 to be detected by the sensor unit 7 is turned on). The path between the I / V conversion unit 14 and the illumination light sensor 13 is switched according to the normal lighting period for lighting. 4 and 5, the I / V conversion unit 14 and the path switching unit SW are actually provided for each of the color light sensors 13R, 13G, and 13B. For each color light, the illumination light sensor 13, the I / V conversion unit 14, and the path switching unit SW constitute a single sensor unit 7 as a whole. A specific example of path switching by the path switching unit SW and a specific configuration of the sensor unit 7 will be described later with reference to FIG.

  The A / D conversion unit 15 samples the light reception data for each color output from the I / V conversion unit 14 at a predetermined timing according to the sampling gate signal SG supplied from the timing control unit 61, and also performs A / D (analog) / Digital) conversion is performed, and the received light data D1, which is a digital voltage signal, is output to the backlight control unit 12 for each color.

  The backlight control unit 12 generates and outputs control signals D3 and D4, which will be described later, based on the light reception data D1 for each color supplied from the A / D conversion unit 15 and the control signal D0 supplied from the timing control unit 61. In addition, the driving operation of the backlight driving unit 11 is controlled. The detailed configuration of the backlight control unit 12 will be described later (FIG. 5).

  Next, with reference to FIG. 5, the detailed configuration of the backlight drive unit 11 and the backlight control unit 12 described above will be described. FIG. 5 is a block diagram illustrating the detailed configuration of the backlight driving unit 11 and the backlight control unit 12 and the configuration of the light source unit 10, the illumination light sensor 13, the I / V conversion unit 14, and the A / D conversion unit 15. Is. The light reception data D1 includes red light reception data D1R, green light reception data D1G, and blue light reception data D1B, and the control signal D3 includes a red control signal D3R, a green control signal D3G, and a blue control. It is assumed that it is composed of the signal D3B. For convenience, the red LED 1R, the green LED 1G, and the blue LED 1B are all shown as being connected in series in the light source unit 10 here.

  The backlight drive unit 11 is supplied with power from the power supply unit 110 according to the power supply unit 110 and the control signal D3 (red control signal D3R, green control signal D3G, and blue control signal D3B) supplied from the backlight control unit 12. The constant current drivers 111R, 111G, and 111B that supply currents IR, IG, and IB to the anode sides of the red LED 1R, the green LED 1G, and the blue LED 1B in the light source unit 10 by the supply, and the red LED 1R, the green LED 1G, and the blue LED 1B, respectively. The switching elements 112R, 112G, and 112B connected between the cathode and the ground, the control signal D4 supplied from the backlight control unit 12, and the control signal D0 supplied from the timing control unit 61, respectively. , 112G, 112B Control signal D5 generates and outputs a (pulse signal) for, switching elements 112R, has 112G, and a PWM driver 113 for each PWM control 112B to.

  The backlight control unit 12 includes a light amount balance control unit 121 and a light amount control unit 122. The light quantity balance control unit 121 controls the constant current drivers 111R, 111G, and 111B based on the light reception data D1 (red light reception data D1R, green light reception data D1G, and blue light reception data D1B) supplied from the A / D conversion unit 15. By generating and outputting D3 (red control signal D3R, green control signal D3G, and blue control signal D3B), the color balance (white balance of white light) of the illumination light Lout from the light source unit 10 is constant. It is controlled so that the light emission amount of the illumination light Lout changes while being maintained. The light quantity control unit 122 controls the PWM driver 113 based on the green light reception data D1G of the light reception data D1 supplied from the A / D conversion unit 15 and the control signal D0 supplied from the timing control unit. By generating and outputting D4, the light emission amount of the illumination light Lout from the light source unit 10 is adjusted and controlled so as to change.

  Here, the backlight driving unit 11 mainly corresponds to a specific example of “light source driving unit” in the present invention, and the backlight control unit 12 mainly corresponds to a specific example of “light source control unit” in the present invention. The sensor unit 7 corresponds to a specific example of the “sensor unit” in the present invention, the illumination light sensor 13 corresponds to a specific example of the “light receiving element” in the present invention, and the I / V conversion unit 14 corresponds to the present invention. The path switching unit SW corresponds to a specific example of “path switching unit” in the present invention.

  FIG. 6 shows a configuration example of the sensor unit 7. The sensor unit 7 is the most characteristic part in the backlight device 1 of the present embodiment. As described above, the sensor unit 7 is provided for each detection region 40. In addition, the sensor unit 7 is provided for each color, but since the substantial configuration is the same for each detection region 40 and each color, a description will be given here.

  The sensor unit 7 includes an illumination light sensor 13, an I / V conversion unit 14, and a path switching unit SW. The configuration of the illumination light sensor 13 and the I / V conversion unit 14 itself is substantially the same as the configuration of the conventional sensor unit (FIG. 17). That is, the illumination light sensor 13 is composed of, for example, a photodiode having a PN junction structure. The I / V conversion unit 14 constitutes a negative feedback type sensor circuit that generates a sensor output signal (output voltage Vout) corresponding to the current generated by the illumination light sensor 13, and includes an output terminal 80 and a feedback capacitor 81. And a feedback resistor 82 and an operational amplifier 83. The feedback capacitor 81 and the feedback resistor 82 are connected in parallel to the inverting input terminal (−) and the output terminal of the operational amplifier 83. The cathode K of the illumination light sensor 13 is connected to the non-inverting input terminal (+) of the operational amplifier 83. An offset voltage V1 is applied to the non-inverting input terminal of the operational amplifier 83. The connection destination of the anode A of the illumination light sensor 13 is switched by the path switching unit SW between detection of the light amount (detection lighting period) and non-detection (normal lighting period).

  The path switching unit SW includes a changeover switch having changeover terminals 71A and 71B and a common terminal 71C. The switching timing of the path switching unit SW is controlled based on, for example, a control signal D0 supplied from the timing control unit 61 (FIGS. 4 and 5). The common terminal 71 </ b> C of the path switching unit SW is connected to the anode A of the illumination light sensor 13. One switching terminal 71A of the path switching unit SW is grounded. The other switching terminal 71B of the path switching unit SW is connected to the I / V conversion unit 14. More specifically, the other switching terminal 71B is connected to one end of the feedback capacitor 81 and the feedback resistor 82 and the inverting input terminal (−) of the operational amplifier 83.

  The path switching unit SW switches the connection destination of the anode A of the illumination light sensor 13 to the sensor circuit (I / V conversion unit 14) side when detecting the light amount, and switches to the ground side when not detecting. Here, with reference to FIGS. 7A and 7B, the potential difference generated in the photodiode as the illumination light sensor 13 will be described. When light is irradiated to the photodiode, electron-hole pairs are generated at the PN junction due to the light energy, and a reverse current corresponding to the amount of light is generated in the cathode while the external circuit (I / V converter 14) is connected. Flow from K to anode A. When considering a state in which both ends are opened as shown in FIG. 7A, a potential difference Vo such that the voltage of the anode A is relatively higher than the cathode K of the photodiode in accordance with the irradiated light. appear. On the other hand, when the anode A is grounded as shown in FIG. 7B, the voltage of the cathode K is relative to the anode A relative to the irradiated light, contrary to FIG. 7A. A potential difference Vo ′ that increases is generated.

  That is, in the circuit of FIG. 6, the path switching unit SW generates a potential difference Vo ′ in the opposite direction to the potential difference Vo at both ends of the illumination light sensor 13 that is generated at the time of detecting the light amount when not detected (normal lighting period). The connection path of the illumination light sensor 13 is switched so as to be in a state. In order to promptly return the photodiode as the illumination light sensor 13 from the saturated state, it is necessary to make the illumination light sensor 13 in a low capacity state so that electric charges can be quickly removed from the illumination light sensor 13. In the circuit of FIG. 6, the path switching unit SW reduces the capacitance by causing the illumination light sensor 13 to generate a potential difference Vo ′ in the direction opposite to that during detection in the period before the light amount detection, and the anode side is grounded. As a result, the electric charge is quickly released to the ground side. Thereby, for example, immediately after all the partial lighting parts 4 in the vicinity of the detection region 40 are lit in the normal lighting state, the state shifts to the detection lighting state, and only the specific partial lighting part 4 is lit to detect the light amount. Even if it is a case, the situation where the illumination light sensor 13 is saturated before the light quantity detection is prevented. In addition, in the state switched to the ground side, the current from the illumination light sensor 13 does not flow to the I / V conversion unit 14, and the output voltage Vout from the I / V conversion unit 14 at that time becomes the offset voltage V1. . In addition, when detecting the light amount when the connection path is switched to the I / V conversion unit 14, the circuit of FIG. 6 operates in the same manner as a normal sensor circuit (FIG. 17). That is, when the light amount is detected, if the resistance value of the feedback resistor 82 is Rf in the I / V conversion unit 14 and the value of the current generated in the illumination light sensor 13 and flowing through the feedback resistor 82 is Is, FIG. As shown, an output voltage Vout that is “− (Is × Rf)” with respect to the offset voltage V1 is obtained.

  Next, operations of the backlight device 1 and the liquid crystal display device 3 of the present embodiment having the above-described configuration will be described in detail.

  First, basic operations of the backlight device 1 and the liquid crystal display device 3 will be described. FIGS. 8A to 8C and FIGS. 9A to 9C are timing waveform diagrams showing the lighting operation in the light source unit 10 of the backlight device 1, and FIG. 8A and FIG. 9A shows the current IR flowing through the red LED 1R, FIGS. 8B and 9B show the current IG flowing through the green LED 1G, and FIGS. 8C and 9C show the current flowing through the blue LED 1B. IB is shown respectively. 10A to 10D are timing waveform diagrams showing an outline of the entire operation of the liquid crystal display device 3. FIG. 10A is a diagram in the liquid crystal display panel 2 from the X driver 51. FIG. 10B shows the voltage applied to the pixel electrode 212 (pixel application voltage, drive voltage), FIG. 10B shows the response of the liquid crystal molecules (actual potential state at the pixel electrode 212), and FIG. 10C shows the Y driver 52. The voltage applied to the gate of the TFT element in the liquid crystal display panel 2 (pixel gate pulse) is shown respectively. FIG. 10D shows the lighting state of the backlight device 1.

  In the backlight device 1, when the switching elements 112 R, 112 G, and 112 B are turned on in the backlight driving unit 11, currents IR, IG, and IB from the constant current drivers 111 R, 111 G, and 111 B are respectively red in the light source unit 10. The light flows to the LED 1R, the green LED 1G, and the blue LED 1B, thereby emitting red light, green light, and blue light, respectively, and emitting illumination light Lout that is mixed color light.

  At this time, the control signal D0 is supplied from the timing control unit 61 to the backlight driving unit 11, and the control signal D5 based on the control signal D0 is transmitted from the PWM driver 113 in the backlight driving unit 11 to the switching elements 112R, 112G, and 112B. Therefore, the switching elements 112R, 112G, and 112B are turned on at a timing according to the control signal D0, and the lighting periods of the red LED 1R, the green LED 1G, and the blue LED 1B are also synchronized with this. . In other words, the red LED 1R, the green LED 1G, and the blue LED 1B are PWM-driven by time-division driving using the control signal D5 that is a pulse signal.

  At this time, the illumination light sensor 13 receives the irradiation light Lout from the light source unit 10. Specifically, in the red light sensor 13R, the green light sensor 13G, and the blue light sensor 13B in the illumination light sensor 13, each color light of the irradiation light Lout from the light source unit 10 is extracted by a photodiode for each color. As a result, a current corresponding to the amount of light of each color is generated, and the received light data of the current value is supplied to the I / V conversion unit 14. Further, the received light data of the current value for each color is converted into the received light data of the analog voltage value by the I / V conversion unit 14 respectively. The light reception data of the analog voltage value for each color is sampled at a predetermined timing according to the sampling gate signal SG supplied from the timing control unit 61 in the A / D conversion unit 15, and the light reception of the digital voltage value is performed. Data D1R, D1G, and D1B are converted.

  Here, in the backlight control unit 12, based on the light reception data D1R, D1G, D1B for each color supplied from the A / D conversion unit 15, a control signal is sent from the light amount balance control unit 121 to the constant current drivers 111R, 111G, 111B. D3R, D3G, and D3B are respectively supplied, and thereby the magnitudes of the currents IR, IG, and IB ΔIR, ΔIG, and ΔIB, that is, the LED 1R so that the luminance and chromaticity (color balance) of the irradiation light Lout are kept constant. , 1G, and 1B are adjusted (see FIGS. 8A to 8C). The light quantity control unit 122 generates a control signal D4 based on the light reception data D1G among the light reception data D1R, D1G, and D1B for each color supplied from the A / D conversion unit 15 and supplies the control signal D4 to the PWM driver 113. Thus, the ON period of the switching elements 112R, 112G, and 112B, that is, the lighting period ΔT of each color LED 1R, 1G, and 1B is adjusted (see FIGS. 8A to 8C). In this way, based on the illumination light Lout from the light source unit 10, the magnitudes ΔIR, ΔIG, ΔIB of the currents IR, IG, IB (light emission luminance of the LEDs 1R, 1G, 1B) and the lighting period are controlled. The light emission amount of the light Lout is adjusted and controlled for each partial lighting unit 4.

  Here, the light quantity control unit 122 inputs only D1G of the control signals D1R, D1G, and D1B, because this is because the human visual sensitivity is the highest for green light, and other controls. The signals D1R and D1B may be input. 8A to 8C, there is only one pulse signal (lighting period: ΔT) per frame period. Actually, FIGS. 9A to 9C are used. ), A plurality of pulse signals (lighting period: ΔT0, for example, a pulse signal between timings t11 and t12, a pulse signal between timings t13 and t14,... Per one frame period (unit display driving period),. ) Is supposed to exist.

  On the other hand, in the entire liquid crystal display device 3 of the present embodiment, the light source of the backlight device 1 is driven by the drive voltage (pixel applied voltage) to the pixel electrode 212 output from the X driver 51 and the Y driver 52 based on the video signal. The illumination light Lout from the unit 10 is modulated by the liquid crystal layer 20 and output from the liquid crystal display panel 2 as display light Dout. In this way, the backlight device 1 functions as a backlight (liquid crystal illumination device) of the liquid crystal display device 3, thereby displaying an image with the display light Dout.

  Specifically, for example, as shown in FIG. 10C, a pixel gate pulse is applied from the Y driver 52 to the gates of TFT elements for one horizontal line in the liquid crystal display panel 2, and at the same time, FIG. As shown in (), the pixel application voltage based on the video signal is applied from the X driver 51 to the pixel electrode 212 for one horizontal line. At this time, as shown in FIG. 10B, the response of the actual potential of the pixel electrode 212 (response of the liquid crystal) is delayed with respect to the pixel applied voltage (the pixel applied voltage rises at timing t21). The actual potential rises at the timing t12). In the backlight device 1, the backlight device 1 is turned on during the period from the timing t22 to t23 when the actual potential is equal to the pixel applied voltage. Video display based on the video signal is performed. 10A to 10D, the period from timing t21 to t23 corresponds to one horizontal period (one frame period), and liquid crystal burn-in prevention or the like is performed in one horizontal period from timing t23 to t25 thereafter. Therefore, the operation is the same as that in one horizontal period from the timing t21 to t23 except that the pixel application voltage is inverted with respect to the common (common) potential Vcom.

  In the liquid crystal display device 3, the control signal D 0 is sent from the timing control unit 61 to the PWM driver 113 in the backlight drive unit 11 using a signal (a signal based on the video signal) supplied from the RGB process processing unit 60. For example, as shown in FIG. 11, in the light source unit 10, a video display area (area where the display video Pa is displayed) having a predetermined luminance or higher in the video display area in the liquid crystal display panel 2 is provided. It is possible to perform an operation in which only the partial lighting part 4 in the region corresponding to is turned on to form the partial lighting region Pb.

  Next, the lighting operation of the backlight device 1 will be described in more detail with reference to FIGS. FIG. 12A shows the timing waveform of the sampling gate signal SG. FIGS. 12B to 12D show the current IR that flows through the red LED 1R, the current IG that flows through the green LED 1G, and the current IB that flows through the blue LED 1B, respectively, as in FIGS. 9A to 9C. However, FIGS. 12B to 12D show timing waveforms for an arbitrary partial lighting unit 4 which is a light quantity detection target. The partial lighting portions 4 other than the detection target are turned off during the detection lighting period Δt1 (current values ΔIR0, ΔIG0, and ΔIB0 are zero).

  As shown in FIG. 12, in the backlight device 1, for example, there is a certain one period in a display period of one frame (periods t 31 to t 32 and timings t 33 to t 34 shown in FIG. 12). A short lighting period (detection lighting period Δt1) for detecting the light amount is provided for the detection area 40, and only the partial lighting unit 4 to be detected is lit during this period. During the display period of one frame other than the detection lighting period Δt1 (the period up to timing t31 shown in FIG. 12, the period from timing t32 to t33, and the period after timing t34), normal video display is performed based on the video signal. This is the period to perform (normal lighting period Δt4). In the normal lighting period Δt4, an arbitrary partial lighting unit 4 is turned on according to a video to be displayed. For example, when white display is performed as a video display, the plurality of partial lighting units 4 are all turned on. In this manner, in the backlight device 1, the light source unit 10 is driven in a time-sharing manner by the pulse signal so that the normal lighting period Δt4 and the detection lighting period Δt1 are mixed along the time axis.

  In the circuit of the sensor unit 7 shown in FIG. 6, in the above-described lighting period for detection Δt1, the connection destination of the anode A of the illumination light sensor 13 is the sensor circuit (I / V conversion unit 14) by the path switching unit SW. Switched to the side. In the normal lighting period Δt4 as described above, switching to the ground side is performed.

  As described above, according to the backlight device 1 of the present embodiment, the illumination light sensor 13 that is a light receiving element is used as a sensor circuit (I / V conversion unit 14) during light amount detection (detection lighting period). In addition to the connection, the connection path of the illumination light sensor 13 is switched so that a potential difference in the opposite direction to the potential difference between the both ends of the illumination light sensor 13 that occurs at the time of light amount detection occurs during non-detection (normal lighting period). Thus, for example, the illumination light sensor 13 is saturated before the light amount is detected even if the partial lighting unit 4 near the detection region is turned on in the normal lighting state and then is in the lighting state for detection. It is prevented from entering a state. Even if only the partial lighting unit 4 to be detected is turned on immediately after the normal lighting state, the detection operation can be performed with high accuracy and high response speed. Further, it is not necessary to provide a complicated control circuit for countermeasures against saturation of the illumination light sensor 13 in a portion other than the sensor unit 7 or to prepare a complicated control algorithm.

Further, since such a backlight device 1 is used as a backlight (liquid crystal illumination device) of the liquid crystal display device 3, fluctuations in luminance and chromaticity can be suppressed and the image quality of the display image can be improved. Is possible.
[Second Embodiment]

  Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the component substantially the same as the said 1st Embodiment, and description is abbreviate | omitted suitably.

FIG. 13 shows a configuration example of the sensor unit 7A in the second embodiment of the present invention.
In the present embodiment, the sensor unit 7A shown in FIG. 13 is provided instead of the sensor unit 7 (FIG. 6) in the first embodiment, and other configurations are the same as those in the first embodiment. It is.

The sensor unit 7A in the present embodiment is obtained by reversing the connection relationship of the illumination light sensor 13 with respect to the circuit configuration of the sensor unit 7 of FIG. That is, in the sensor unit 7 of FIG. 6, when detecting the light amount, the cathode K side of the illumination light sensor 13 is connected to the non-inverting input terminal (+) of the operational amplifier 83, and the anode A side is connected to the inverting input terminal (−). However, in the sensor unit 7A according to the present embodiment, the cathode K side is connected to the inverting input terminal (−) of the operational amplifier 83 and the anode A side is connected to the non-inverting input terminal (+) when detecting the light amount. It is what I did. Further, in the sensor unit 7 of FIG. 6, only one path switching unit SW is provided and only the connection path of the anode A of the illumination light sensor 13 is switched. However, in the sensor unit 7A in the present embodiment, there are two Route switching units SW1 and SW2 are provided, and the connection routes at both ends of the illumination light sensor 13 are switched.
In the present embodiment, the first route switching unit SW1 and the second route switching unit SW2 correspond to a specific example of “route switching unit” in the present invention.

  The first path switching unit SW1 is configured by a switching switch having switching terminals 71A and 71B and a common terminal 71C, similarly to the path switching unit SW of FIG. The common terminal 71 </ b> C of the first path switching unit SW <b> 1 is connected to the anode A of the illumination light sensor 13. One switching terminal 71A of the first path switching unit SW1 is grounded. The other switching terminal 71B of the first path switching unit SW1 is connected to the I / V conversion unit 14. More specifically, the other switching terminal 71B is connected to the non-inverting input terminal (+) of the operational amplifier 83.

  Similarly, the second path switching unit SW2 includes a changeover switch having changeover terminals 72A and 72B and a common terminal 72C. The common terminal 72C of the second path switching unit SW2 is connected to the cathode K of the illumination light sensor 13. One switching terminal 72A of the second path switching unit SW2 is an open end. The other switching terminal 72B of the second path switching unit SW2 is connected to the I / V conversion unit 14. More specifically, the other switching terminal 72B is connected to one end of the feedback capacitor 81 and the feedback resistor 82 and the inverting input terminal (−) of the operational amplifier 83.

The first path switching unit SW1 switches the connection destination of the anode A of the illumination light sensor 13 to the sensor circuit (I / V conversion unit 14) side when detecting the light amount, and switches to the ground side when not detecting. . Further, the second path switching unit SW2 switches the connection destination of the cathode K of the illumination light sensor 13 to the sensor circuit (I / V conversion unit 14) side when detecting the light amount, and disconnects from the sensor circuit when not detecting, and opens the open end. Switch to the side. Note that the timing of switching by the path switching units SW1 and SW2 is the same as that of the path switching unit SW in FIG. This prevents a situation in which the illumination light sensor 13 is saturated before the light amount is detected based on the same principle as that of the sensor unit 7 of FIG. Further, at the time of light amount detection in which the connection path is switched to the I / V conversion unit 14 side, an output whose polarity is reversed from the output characteristic (FIG. 18) by the sensor unit 7 of FIG. 6 is obtained. FIG. 14 shows a characteristic example of the output voltage Vout output from the output terminal 80 of the I / V conversion unit 14 in the circuit of FIG. In the circuit of FIG. 13, if the resistance value of the feedback resistor 82 is Rf and the value of the current generated in the illumination light sensor 13 (photodiode) and flowing through the feedback resistor 82 is Is, the offset voltage V1 is used as a reference. An output voltage Vout of “Is × Rf” is obtained. In the state where the anode A is switched to the ground side, the current from the illumination light sensor 13 does not flow to the I / V conversion unit 14, and the output voltage Vout from the I / V conversion unit 14 at that time is the offset voltage. V1.
[Third Embodiment]

  Next, a third embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the component substantially the same as the said 1st Embodiment, and description is abbreviate | omitted suitably.

FIG. 15 shows a configuration example of the sensor unit 7B according to the third embodiment of the present invention.
The present embodiment includes a sensor unit 7B of FIG. 15 instead of the sensor unit 7 (FIG. 6) in the first embodiment, and other configurations are the same as those of the first embodiment. It is.

The sensor unit 7B in the present embodiment is different in the configuration of the I / V conversion unit 14 from the circuit configuration of the sensor unit 7 in FIG. In the sensor unit 7 of FIG. 6, the I / V conversion unit 14 is configured by a circuit using the operational amplifier 83, but in this embodiment, the I / V conversion unit 14 is configured by a load resistor 84. An output terminal 80 is connected to one end of the load resistor 84. Further, in the sensor unit 7 of FIG. 6, only one path switching unit SW is provided and only the connection path of the anode A of the illumination light sensor 13 is switched. Route switching units SW1 and SW2 are provided, and the connection routes at both ends of the illumination light sensor 13 are switched.
In the present embodiment, the first route switching unit SW1 and the second route switching unit SW2 correspond to a specific example of “route switching unit” in the present invention.

  The first path switching unit SW1 is configured by a switching switch having switching terminals 71A and 71B and a common terminal 71C, similarly to the path switching unit SW of FIG. The common terminal 71 </ b> C of the first path switching unit SW <b> 1 is connected to the anode A of the illumination light sensor 13. One switching terminal 71A of the first path switching unit SW1 is grounded. The other switching terminal 71B of the first path switching unit SW1 is connected to the I / V conversion unit 14. More specifically, the other switching terminal 71 </ b> B is connected to one end of the load resistor 84.

  Similarly, the second path switching unit SW2 includes a changeover switch having changeover terminals 72A and 72B and a common terminal 72C. The common terminal 72C of the second path switching unit SW2 is connected to the cathode K of the illumination light sensor 13. One switching terminal 72A of the second path switching unit SW2 is an open end. The other switching terminal 72B of the second path switching unit SW2 is connected to the I / V conversion unit 14. More specifically, the other switching terminal 72 </ b> B is connected to the other end of the load resistor 84.

  The first path switching unit SW1 switches the connection destination of the anode A of the illumination light sensor 13 to the sensor circuit (I / V conversion unit 14) side when detecting the light amount, and switches to the ground side when not detecting. . Further, the second path switching unit SW2 switches the connection destination of the cathode K of the illumination light sensor 13 to the sensor circuit (I / V conversion unit 14) side when detecting the light amount, and disconnects from the sensor circuit when not detecting, and opens the open end. Switch to the side. Note that the timing of switching by the path switching units SW1 and SW2 is the same as that of the path switching unit SW in FIG. This prevents a situation in which the illumination light sensor 13 is saturated before the light amount is detected based on the same principle as that of the sensor unit 7 of FIG. Further, at the time of detecting the light amount when the connection path is switched to the I / V conversion unit 14 side, the output voltage Vout having the characteristics as shown in FIG. In the circuit of FIG. 15, if the resistance value of the load resistor 84 is RL and the value of the current generated by the illumination light sensor 13 (photodiode) and flowing through the load resistor 84 is Io, “Io × RL”. An output voltage Vout is obtained. In the state where the anode A is switched to the ground side, the current from the illumination light sensor 13 does not flow to the I / V conversion unit 14, and the output voltage Vout from the I / V conversion unit 14 at that time becomes zero. .

In addition, this invention is not limited to said each embodiment, A various deformation | transformation implementation is possible.
For example, in each of the above embodiments, a description is given of a case where control is performed so that the light emission amount of each partial lighting unit 40 in the detection region 40 is kept constant based on the sampled light reception signal in the detection lighting period Δt1. However, on the basis of the sampled light reception signal in the detection lighting period Δt1, control is performed so that the light emission amount of only the partial lighting part that is lit in the detection lighting period Δt1 is kept constant. As described above, the partial lighting section that is lit during the detection lighting period Δt1 may circulate in the detection region 40, for example. Even in such a configuration, the light emission amount of the partial lighting part that is lit during the detection lighting period Δt1 based on the light reception signal during the detection lighting period Δt1 whose value is kept almost constant regardless of the sampling timing. Since each is controlled, it is possible to improve the accuracy of keeping the light emission amount constant. In addition, since the partial lighting parts that are the control targets of the light emission amount circulate in the detection region 40 or the like in this way, all the partial lighting parts 4 are controlled based on their own illumination light. Fine light emission amount control for the partial lighting unit 4 is possible, and the accuracy of keeping the light emission amount constant as the entire light source unit 10 can be further improved.

  In each of the above embodiments, the case where the detection lighting period Δt1 is provided only once in one frame period has been described. However, a plurality of detection lighting periods Δt1 are provided in one frame period. Conversely, one detection lighting period Δt1 may be provided in a plurality of frame periods. Further, the position of the detection lighting period Δt1 within one frame period is not limited to the head within one frame period.

  In each of the above embodiments, the light source unit 10 has been described as being configured of the red LED 1R, the green LED 1G, and the blue LED 1B. In addition to (or instead of) these, LEDs that emit other colored light You may make it comprise including. When configured with four or more color lights, it is possible to expand the color reproduction range and express more diverse colors.

  In each of the above embodiments, the light source unit 10 includes a plurality of red LEDs 1R, a green LED 1G, and a blue LED 1B, and a plurality of color lights (red light, green light, and blue light) are mixed to generate a specific color light (white). Although the additive color mixing type backlight device 1 that obtains the illumination light Lout that is light) has been described, a light source unit may be configured by one type of LED, and a backlight device that emits monochromatic illumination light may be used. Even in such a configuration, it is possible to reduce the variation in the luminance of the illumination light with a simple configuration.

  In each of the above embodiments, the case where the liquid crystal display device 3 is a transmissive liquid crystal display device including the backlight device 1 has been described. However, the front light device is configured by the light source device of the present invention, and the reflection type liquid crystal display device is formed. A liquid crystal display device may be used.

  Furthermore, the light source device of the present invention can be applied not only to a lighting device for a liquid crystal display device but also to other light source devices such as lighting equipment.

1 is a perspective view illustrating an overall configuration of a liquid crystal display device according to a first embodiment of the present invention. It is a plane schematic diagram showing the structural example of the unit unit (partial lighting part) of the light source part in the backlight apparatus shown in FIG. FIG. 3 is a schematic plan view illustrating an arrangement configuration example of a partial lighting unit and an illumination light sensor in a light source unit in FIG. 2. It is a block diagram showing the whole structure of the liquid crystal display device shown in FIG. FIG. 5 is a block diagram illustrating in detail a configuration of a drive and control part of the light source unit illustrated in FIG. 4. It is a circuit diagram which shows one structural example of the sensor part in the 1st Embodiment of this invention. It is explanatory drawing about the electrical potential difference of the both ends of a photodiode. It is a timing waveform diagram for demonstrating the drive pulse signal of a light source part. FIG. 9 is a timing waveform diagram illustrating a detailed configuration of a drive pulse signal illustrated in FIG. 8. FIG. 3 is a timing waveform diagram for explaining an example of a method for driving the liquid crystal display panel and the backlight device shown in FIG. 1. It is a perspective view for demonstrating an example of arrangement | positioning relationship between a video display area | region and a partial lighting area | region. It is a timing waveform diagram for demonstrating an example of lighting operation of a light source part, and light reception operation | movement of an illumination light sensor. It is a circuit diagram which shows one structural example of the sensor part in the 2nd Embodiment of this invention. It is a characteristic view which shows an example of the output characteristic of the sensor part in the 2nd Embodiment of this invention. It is a circuit diagram which shows one structural example of the sensor part in the 3rd Embodiment of this invention. It is a characteristic view which shows an example of the output characteristic of the sensor part in the 3rd Embodiment of this invention. It is a circuit diagram which shows one structural example of the conventional sensor part. It is a characteristic view which shows an example of the output characteristic of the sensor part shown in FIG. It is a circuit diagram which shows one structural example of the sensor part which has a gain switching function.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Backlight apparatus, 1R ... Red LED, 1G ... Green LED, 1B ... Blue LED, 2 ... Liquid crystal display panel, 3 ... Liquid crystal display device, 4, 4A, 4B, 4C, 4D ... Unit unit (partial lighting part) 7, 7A, 7B ... sensor unit, 10 ... light source unit, 11 ... backlight drive unit, 12 ... backlight control unit, 13 ... illumination light sensor, 13R ... red light sensor, 13G ... green light sensor, 13B ... blue Optical sensor, 14 ... I / V converter, 15 ... A / D converter, 20 ... liquid crystal layer, 40 ... detection region, 41,42 ... unit cell, 51 ... X driver, 52 ... Y driver, 60 ... RGB process Processing unit 61 ... Timing control unit 62 ... Video memory 81 ... Feedback capacitance 82 ... Feedback resistor 83 ... Op amp 84 ... Load resistor 110 ... Power supply unit 111R, 111G, 111B ... Constant current , 112R, 112G, 112B ... switching element, 113 ... PWM driver, 121 ... light quantity control unit, 122 ... light quantity balance control unit, 210, 220 ... polarizing plate, 211 ... TFT substrate, 212 ... pixel electrode, 221 ... counter electrode Substrate, CFR, CFG, CFB ... color filter, D0, D3, D4, D5 ... control data, D1 ... received light data, Dout ... display light, IR, IG, IB ... current, Lout ... illumination light, Pa ... display image, Pb: Partial lighting region, SG: Sampling gate signal, SW, SW1, SW2, ... Path switching unit, ΔT, ΔT0: Pulse width, Δt1: Detection lighting period, Δt4: Normal lighting period, ΔIR, ΔIR0, ΔIG, ΔIG0 , ΔIB, ΔIB0... Current value (pulse height).

Claims (5)

A light source unit having a plurality of partial lighting units capable of controlling light emission independently of each other;
A sensor unit that is provided for each of a plurality of detection regions set to include two or more partial lighting units, and detects a light amount when a partial partial lighting unit in the detection region is lit;
A normal lighting period in which the plurality of partial lighting parts are turned on in accordance with an input signal and a detection lighting period in which only the partial lighting part that is the target of light amount detection by the sensor part is mixed along the time axis. A light source driving means for driving the light source unit and sequentially lighting the partial lighting unit in each detection region during the detection lighting period across the normal lighting period;
Light source control means for adjusting the light emission amount of the partial lighting unit based on the detection result of the sensor unit,
The sensor unit is
A light receiving element that generates a current corresponding to the amount of light from the partial lighting unit that is a target of light amount detection in the detection region;
A sensor circuit for generating a sensor output signal corresponding to the current generated in the light receiving element;
The light receiving element is connected to the sensor circuit during the detection lighting period, and a potential difference in a direction opposite to the potential difference between both ends of the light receiving element that occurs during light amount detection occurs during the normal lighting period. And a path switching unit that switches a connection path of the light receiving element. The light receiving element is a photodiode;
The light source device according to claim 1, wherein the path switching unit switches the path so that a potential difference in which a cathode voltage is higher than a voltage of an anode of the photodiode is generated. The light source device according to claim 2, wherein the path switching unit switches the path so that an anode of the photodiode is grounded during the normal lighting period. A light source device applied to a liquid crystal display panel that modulates incident light based on a video signal,
It is configured as a liquid crystal illumination device that emits light from each of the partial lighting sections to the liquid crystal display panel as the incident light,
The light source device according to claim 1, wherein the light source driving unit lights the plurality of partial lighting units according to the video signal in the normal lighting period. A liquid crystal display device comprising: a light source device that emits light; and a liquid crystal display panel that modulates light emitted from the light source device based on a video signal,
The light source device is
A light source unit having a plurality of partial lighting units capable of controlling light emission independently of each other;
A sensor unit that is provided for each of a plurality of detection regions set to include two or more partial lighting units, and detects a light amount when a partial partial lighting unit in the detection region is lit;
A normal lighting period in which the plurality of partial lighting parts are turned on according to an input video signal and a detection lighting period in which only the partial lighting part that is a target of light amount detection by the sensor part is turned on along the time axis. Driving the light source units so as to be mixed, light source driving means for sequentially lighting the partial lighting units in each detection region in the detection lighting period across the normal lighting period;
Light source control means for adjusting the light emission amount of the partial lighting unit based on the detection result of the sensor unit,
The sensor unit is
A light receiving element that generates a current corresponding to the amount of light from the partial lighting unit that is a target of light amount detection in the detection region;
A sensor circuit for generating a sensor output signal corresponding to the current generated in the light receiving element;
The light receiving element is connected to the sensor circuit during the detection lighting period, and a potential difference in a direction opposite to the potential difference between both ends of the light receiving element that occurs during light amount detection occurs during the normal lighting period. And a path switching unit that switches a connection path of the light receiving element.

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