JP2012128339A - Liquid crystal display device, liquid crystal display system and display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device reducing a luminance difference between an upper section and a lower section of a display for displaying an image, and further to provide a liquid crystal display system and a display method.SOLUTION: A projector 1 comprises: LEDs 14R, 14G and 14B being turned off during a first field period and being turned on during a second field period following the first field period; liquid crystal panels 13R, 13G and 13B having a plurality of pixels, scanning each of the plurality of pixels during the first field period and the second field period and transmitting light beams emitted from the LEDs 14R, 14G and 14B with transmittances controlled for each of the plurality of pixels; and a controller 4 for controlling time responses required for raising the amount of light emitted when the LEDs 14R, 14G and 14B start being turned on during the second field period based on a time response of a transmittance of a pixel scanned during the last period of the first field period divided into a plurality of periods.

Description

  The present invention relates to a liquid crystal display device, a liquid crystal display system, and a display method.

  A display device for the purpose of obtaining good image quality is disclosed in Patent Document 1. The display device disclosed in Patent Document 1 includes glasses with a liquid crystal shutter that a user wears to view an image shot using binocular parallax, and synchronizes this shutter operation with switching of the display frame. .

JP 2010-93740 A

  However, when the image is updated by sequentially scanning from the upper part to the lower part of the screen displaying the image, the display device disclosed in Patent Document 1 uses the time response (optical response) of the transmittance of the liquid crystal to the upper part of the screen. Since there is a difference in transmittance between the upper part and the lower part, there is a problem that a luminance difference occurs between the upper part and the lower part of the screen.

  In addition, the time response of the transmittance of the liquid crystal until the image before update is completely updated changes according to the luminance difference of the screen. For example, if a pixel that displayed a low-brightness color before the update displays a high-brightness color after the update, the brightness is completely lower than if a high-brightness color was displayed before the update. The time response of the transmittance of the liquid crystal until it is updated is different. As described above, in the display device disclosed in Patent Document 1, there is a problem in that crosstalk occurs in which the image before the update remains in the image after the update according to the luminance difference generated between the upper part and the lower part of the screen. was there.

  In particular, when displaying a three-dimensional image captured using binocular parallax, the display device disclosed in Patent Document 1 has a problem that crosstalk occurs depending on the amount of light from the light source. there were.

  The present invention has been made in view of the above-described points, and an object of the present invention is to provide a liquid crystal display device and a display method that reduce a luminance difference between an upper part and a lower part of a screen that displays an image.

The present invention has been made to solve the above-described problem, and includes a light source unit that is turned off in a first field period and turned on in a second field period, and a plurality of pixels, and the first field period. A liquid crystal panel that scans each of the plurality of pixels in the second field period and transmits light from the light source unit with a transmittance controlled for each pixel; and a last of the first field period divided into a plurality Based on the time response of the transmittance of at least one pixel included in the pixel group scanned in the period, the time response of the rise of the light emission amount when the light source unit starts lighting in the second field period is controlled. And a control unit.
Thereby, the liquid crystal display device adjusts the light amount of the light source unit according to the time response of the transmittance of the liquid crystal, thereby reducing the luminance difference between the upper and lower parts of the screen on which the image is displayed and reducing the crosstalk. be able to.

Further, according to the present invention, the liquid crystal panel scans the plurality of pixels based on the same image in the first field period and the second field period, and emits light from the light source unit with transmittance controlled for each pixel. A liquid crystal display device is characterized by transmitting light.
Thereby, since the liquid crystal display device scans based on the same image in the first field period and the second field period, the image does not change in the second field in which the light source unit is lit, thereby reducing crosstalk. be able to.

According to the present invention, when the control unit starts lighting in the second field period based on a time response of the transmittance of the last one pixel scanned in the first field period. The liquid crystal display device is characterized in that it controls the time response of the rise of the light emission amount.
As a result, the liquid crystal display device can prevent the occurrence of crosstalk.

According to the present invention, the control unit sets the plurality of pixels based on an image different from the second field period in a third field period in which the light source unit is turned off after the second field period. In the case of scanning, the light source unit is controlled to be turned off at the start of scanning in the third field period.
Thereby, since the light source unit is turned off during the period in which the image in the second field period is switched to the image in the third field period, crosstalk can be reduced.

According to the present invention, the controller scans the transmittance in the field period immediately before the first field period of the pixel scanned in the last period among the first field period divided into a plurality of the first field period. The liquid crystal display device is characterized in that, based on a difference from the transmittance in the second field period, the time response of the rise of the light emission amount when the light source unit starts lighting in the second field period. .
Thus, when the field period is divided into a plurality of times, the time response of the rise of the light emission amount is controlled only when the lighting is started in the first field period, so that a bright screen can be obtained.

Further, the present invention is characterized in that the control unit controls the time response of the rise of the light emission amount when the light source unit starts lighting in the second field period according to the temperature of the liquid crystal panel. The liquid crystal display device.
As a result, the response time of the transmittance of the liquid crystal panel changes depending on the temperature. By controlling the time response of the rise of the light emission amount according to the temperature of the liquid crystal panel, the upper part of the screen on which the image is projected (displayed) It is possible to reduce the luminance difference from the lower portion and reduce crosstalk.

The present invention is also the liquid crystal display device, wherein the light source unit is a solid light source.
Examples of the solid light source include a light emitting diode and a semiconductor laser. Thereby, compared with light sources, such as a high pressure mercury lamp and a metal halide lamp, control of the time response of the emitted light quantity of a light source part can be implemented easily.

Further, the present invention provides a liquid crystal display device that alternately displays an image for the left eye and an image for the right eye, and the image for the left eye and the image for the right eye displayed by the liquid crystal display device, A liquid crystal display system comprising: glasses that alternately transmit according to a timing signal notified from the liquid crystal display device.
Thereby, the liquid crystal display system can reduce the luminance difference and the crosstalk between the upper part and the lower part of the screen in the 3D image.

The present invention is also a display method in a liquid crystal display device, wherein the light source unit is turned off in the first field period and turned on in the subsequent second field period, and the liquid crystal panel has a plurality of pixels, Scanning the plurality of pixels in each of the first field period and the second field period and transmitting light from the light source unit at a transmittance controlled for each pixel; and a control unit configured to perform the first field period Based on the time response of the transmittance of the pixels scanned in the last period among the plurality of divisions, the time response of the rise of the light emission amount when the light source unit starts lighting in the second field period is controlled. A display method comprising: steps.
Accordingly, the display method in the liquid crystal display device adjusts the light amount of the light source unit according to the time response of the transmittance of the liquid crystal, thereby reducing the luminance difference between the upper and lower portions of the screen on which the image is projected (displayed). Crosstalk can be reduced.

  According to the present invention, the liquid crystal display device adjusts the amount of light of the light source unit according to the time response of the transmittance of the liquid crystal, thereby reducing the luminance difference between the upper and lower portions of the screen on which the image is projected (displayed). Crosstalk can be reduced.

It is a block diagram showing the example of a structure of the liquid crystal display device in 1st Embodiment of this invention. It is a block diagram showing the structural example of the optical system which comprises the liquid crystal display device in 1st Embodiment of this invention. It is a time chart showing operation | movement of the liquid crystal display device in 1st Embodiment of this invention. It is a table | surface which shows the light emission amount according to the average value of the transmittance | permeability of the liquid crystal in 1st Embodiment of this invention. It is a figure for comparing the light quantity which permeate | transmits glasses with the case where it is assumed that the light emission amount is constant and the light emission amount is changed in the first embodiment of the present invention. It is a time chart showing the operation | movement according to the temperature of the liquid crystal display device in 1st Embodiment of this invention. It is a block diagram showing the structural example of the liquid crystal display device in 2nd Embodiment of this invention.

[First embodiment]
A first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of a liquid crystal display device. The liquid crystal display system includes a projector 1 and 3D glasses 80. The projector 1 projects an image on a screen based on the image data and the timing signal. The user can see the image projected on the screen. Here, a user who is not wearing the 3D glasses 80 can see a two-dimensional image on the screen. In addition, when a 3D image captured using binocular parallax is projected on the screen, the user wearing the 3D glasses 80 can view the 3D image on the screen.

  The 3D glasses 80 include a 3D glasses circuit 81, right eye glasses 82, and left eye glasses 83. The 3D glasses circuit 81 receives a timing signal notified by infrared rays from the projector 1. When one image frame is composed of a plurality of field images, this timing signal is a vertical synchronization signal (VSYNC) for scanning the field image to be displayed.

  The 3D glasses 80 alternately shield the light incident on the left and right glasses via the screen from the projector 1 according to the timing signal notified from the projector 1. Specifically, the right eyeglasses 82 blocks light incident on the user's right eye according to the timing signal. Further, the left eye glasses 83 shields light incident on the user's left eye according to the timing signal.

  The projector 1 includes a main board 2, a control unit (microcomputer) 4, a liquid crystal panel (red light transmission liquid crystal light valve) 13R, a liquid crystal panel (green light transmission liquid crystal light valve) 13G, and a liquid crystal panel. (Blue light transmission type liquid crystal light valve) 13B, a temperature sensor (thermistor) 62, a light amount detection unit 64, a light source driving circuit 70, and an optical system. Details of the optical system will be described later with reference to FIG.

  The temperature sensor 62 measures the temperatures of the liquid crystal panels 13R, 13G, and 13B and outputs the temperature information to the main board 2.

  Image data, timing signals, and temperature information are input to the main board 2. The main board 2 communicates timing signals to the 3D glasses 80 by infrared rays. The main board 2 scans the screen by scanning the liquid crystal panels 13R, 13G, and 13B based on the image data, the timing signal, and the temperature information (screen scanning). Here, the main board 2 updates the image according to the image data by sequentially scanning through the liquid crystal panels 13R, 13G, and 13B from the upper part to the lower part of the screen in synchronization with the timing signal. Project an image onto the screen. Details of the screen scanning will be described later with reference to FIGS. 3 and 6.

  The main board 2 includes a storage unit 3. The storage unit 3 is a look-up table (hereinafter referred to as “LUT”) that represents the relationship between the average value of the transmittance of the liquid crystal included in the liquid crystal panels 13R, 13G, and 13B and the inclination of the light emission amount in the time direction. "). Details of the LUT will be described later with reference to FIG. In addition, the memory | storage part 3 may memorize | store the calculation formula showing the relationship between the average value of the transmittance | permeability of a liquid crystal, and the inclination of the light emission amount in a time direction.

  FIG. 2 is a block diagram illustrating a configuration example of an optical system constituting the projector 1. The optical system includes a red light (for R light) LED 14R, a green light (for G light) LED 14G, a blue light (for B light) LED 14B, a collimator lens 12, and a liquid crystal panel (space light for R light). A modulation device 13R, a liquid crystal panel (G light spatial light modulation device) 13G, a liquid crystal panel (B light spatial light modulation device) 13B, a cross dichroic prism 11, and a projection lens 17 are provided.

  The red light LED 14R is a solid light source and emits red light. The red light emitted from the red light LED 14R is collimated by the collimator lens 12 and enters the liquid crystal panel 13R. The liquid crystal panel 13R is a transmissive liquid crystal light valve that scans a plurality of pixels and modulates red light with a transmittance controlled for each pixel in accordance with an image signal. The red light modulated by the liquid crystal panel 13R enters the cross dichroic prism 11.

  The green light LED 14G is a solid light source and emits green light. The green light emitted from the green light LED 14G is collimated by the collimator lens 12 and enters the liquid crystal panel 13G. The liquid crystal panel 13G is a transmissive liquid crystal light valve that scans a plurality of pixels and modulates green light with a transmittance controlled for each pixel in accordance with an image signal. The green light modulated by the liquid crystal panel 13G enters the cross dichroic prism 11 from a direction different from the red light.

  The blue light LED 14B is a solid light source and emits blue light. The blue light emitted from the blue light LED 14B is collimated by the collimator lens 12 and enters the liquid crystal panel 13B. The liquid crystal panel 13B is a transmissive liquid crystal light valve that scans a plurality of pixels and modulates blue light with a transmittance controlled for each pixel in accordance with an image signal. The blue light modulated by the liquid crystal panel 13B enters the cross dichroic prism 11 from a different direction from the red light and the green light. Hereinafter, the red light LED 14R, the green light LED 14G, and the blue light LED 14B are collectively referred to as a “solid light source 14”.

  Note that the optical system may include a uniformizing optical system, for example, a rod integrator and a fly-eye lens, for uniformizing the intensity distribution of the luminous flux after the LED for each color light.

  The cross dichroic prism 11 is an optical system that combines red light, green light, and blue light. The cross dichroic prism 11 includes a first dichroic film 15 and a second dichroic film 16. The first dichroic film 15 and the second dichroic film 16 are disposed so as to be substantially orthogonal to each other.

  The first dichroic film 15 reflects red light and transmits green light and blue light. On the other hand, the second dichroic film 16 reflects blue light and transmits red light and green light. Thereby, the red light, the green light, and the blue light are combined and enter the projection lens 17. The projection lens 17 projects the light combined by the cross dichroic prism 11 onto the screen 18. Thereby, an image corresponding to the image signal is projected on the screen 18.

  Returning to FIG. 1, the description of the configuration example of the liquid crystal display device is continued. The light source driving circuit (DC-DC circuit) 70 includes FETs (Field Effect Transistors) 71 and 72. Whether or not the FET 72 is valid is controlled by the control unit 4.

  When the FET 72 is invalid, the light source driving circuit 70 turns off the solid light source 14. On the other hand, when the FET 72 is valid, the light source driving circuit 70 turns on the solid-state light source 14. Further, the width (Duty) of the waveform of the voltage applied to the FET 71 when the FET 72 is valid is PWM (Pulse Width Modulation) controlled by the control unit 4. Moreover, the light emission amount of the solid light source 14 is adjusted by this PWM control.

  The light quantity detection unit 64 includes an I / V conversion circuit 63, a photodiode (PD), and a differential amplifier circuit 5. The I / V conversion circuit 63 generates a current corresponding to the amount of received light when the photodiode receives the light emitted from the solid-state light source 14. The I / V conversion circuit 63 measures a current generated inside, converts the measured current (I) into a voltage (V), and outputs the voltage (V) to the differential amplifier circuit 5. The differential amplifier circuit 5 amplifies the voltage input from the I / V conversion circuit 63 and outputs the amplified voltage to the control unit 4 as a voltage corresponding to the light emission amount of the solid light source 14.

  Returning to FIG. 1, the description of the configuration example of the liquid crystal display device is continued. The control unit 4 turns off the solid-state light source 14 of the light source driving circuit 70 by not applying a voltage to the FET 72 according to the timing signal notified from the main board 2 through communication. Here, since the voltage according to the light emission amount of the solid light source 14 is input from the differential amplifier circuit 5 to the control unit 4, the control unit 4 can identify whether or not the solid light source 14 is turned off. it can.

  When a voltage is applied to the FET 72, the control unit 4 adjusts the light emission amount of the solid-state light source 14 by performing PWM control on the width of the waveform of the voltage applied to the FET 71. Since the voltage difference corresponding to the light emission amount of the solid light source 14 is input from the differential amplifier circuit 5 to the control unit 4, the control unit 4 determines the difference between the light emission amount of the solid light source 14 and the target light emission amount. Can be detected. Here, the control unit 4 adjusts the light emission amount of the solid-state light source 14 according to the transmittance of the liquid crystal through which the light forming the image projected on the lower portion of the screen 18 (see FIG. 2) is transmitted.

  FIG. 3 is a time chart showing the operation of the liquid crystal display device. The horizontal axis in FIG. 3 represents time. Each field (n, n + 1,..., N is a positive integer) that divides the horizontal axis represents a scanning period (hereinafter referred to as “field period”) for displaying one field image that switches in synchronization with the timing signal. Represents each.

  The control unit 4 (see FIG. 1) is configured to generate a solid-state light source based on the time response of the transmittance of at least one pixel included in the pixel group scanned in the last period among the n-th field period divided into a plurality. 14 controls the time response of the rise of the light emission amount when lighting starts in the (n + 1) th field period. In addition, the control unit 4 determines that the solid-state light source 14 is based on the time response of the transmittance of at least one pixel included in the pixel group scanned in the last period among the (n + 2) th field period. The time response of the rise of the light emission amount when starting lighting in the (n + 3) th field period is controlled. These controls will be described later with reference to FIG.

  “Screen scanning” in FIG. 3 indicates that scanning is sequentially performed from the scanning line at the top of the screen to the scanning line at the bottom of the screen within one field period. In FIG. 3, as an example, the right-eye image R is scanned in the n-th field period, and the right-eye image R is scanned in the (n + 1) -th field period (multiple scanning). Also, the right-eye image R projected on the screen in the (n + 2) -th field period is updated to the left-eye image L by screen scanning, and the left-eye image in the (n + 3) -th field period. L is scanned (multiple scans). Thus, by scanning the screen from the nth field to the (n + 3) field, two images for the right eye and for the left eye are scanned, and the display of one frame image is completed. In the (n + 4) th field period, the same screen scanning as that in the nth field period is performed.

  A “polarity inversion signal (Field Reverse Pulse: FRP)” in FIG. 3 is a signal representing the polarity of a voltage applied to a plurality of pixels included in the liquid crystal panels 30 to 32. In the n-th field period, a positive voltage is applied to the liquid crystal, and in the (n + 1) -th field period, a negative voltage is applied to the liquid crystal. Further, a positive voltage is applied to the liquid crystal in the (n + 2) th field period, and a negative voltage is applied to the liquid crystal in the (n + 3) field period. In the (n + 4) field period, the voltage is applied in the same manner as in the nth field period. Thereby, the positive voltage applied to the liquid crystal and the negative voltage applied to the liquid crystal can be made substantially the same, and the polarity can be balanced. Therefore, it is possible to suppress the occurrence of display defects such as flicker and display image burn-in.

  “Right-eye glasses” in FIG. 3 represents ON or OFF of the right-eye glasses 82 of the 3D glasses 80. Here, “ON” means a state (open) in which light incident on the glasses is not blocked by the liquid crystal. Further, “off” is a state in which light incident on the glasses is blocked by the liquid crystal. “Left eye glasses” in FIG. 4 represents ON or OFF of the left eye glasses 83 of the 3D glasses 80.

  Further, in “right eyeglasses” and “left eyeglasses” in FIG. 3, a broken line represents a timing signal notified from the projector 1 by infrared rays. A solid line represents ON or OFF of the liquid crystal according to a timing signal notified by infrared rays. As shown in FIG. 3, on and off vary transiently with respect to the timing signal.

  In “right eyeglasses” in FIG. 3, it is turned off in the nth field period and turned on in the (n + 1) th field period. Further, it is turned off in the (n + 2) th field period and turned off in the (n + 3) th field period. In the (n + 4) th field period, the field is turned off as in the nth field period.

  Further, “left eyeglasses” in FIG. 3 is turned off in the nth field period and turned off in the (n + 1) th field period. Further, it is turned off in the (n + 2) th field period and turned on in the (n + 3) th field period. In the (n + 4) th field period, the field is turned off as in the nth field period.

  “Transmittance of liquid crystal corresponding to the upper part of the screen” in FIG. 3 represents the time response (optical response) of the transmittance of the liquid crystal through which the image projected on the upper area of the screen is transmitted. Similarly, “the transmittance of the liquid crystal corresponding to the lower part of the screen” in FIG. 3 represents the time response (optical response) of the transmittance of the liquid crystal through which the image projected on the lower area of the screen is transmitted.

  The liquid crystal panels 13R, 13G, and 13B scan a plurality of pixels based on the same image in the nth field period and the (n + 1) th field period, and transmit light from the solid-state light source 14 with transmittance controlled for each pixel. . Since the liquid crystal panels 13R, 13G, and 13B scan based on the same image in the nth field period and the (n + 1) field period, the image does not change in the (n + 1) field in which the solid light source 14 is lit. Thereby, the liquid crystal display device can reduce crosstalk. The same applies to the (n + 2) th field period and the (n + 3) field period.

  In FIG. 3, the image projected on the screen 18 (see FIG. 2) when the right-eye glasses 82 are on is, for example, white (transmittance 100%), while the left-eye glasses 83. As an example, an image projected on the screen 18 when is turned on is assumed to be gray (transmittance 50%). Here, “the transmittance of the liquid crystal corresponding to the upper part of the screen” is assumed to be 100% transmittance in the (n + 1) th field period and 50% transmittance in the (n + 3) th field period. On the other hand, “the transmittance of the liquid crystal corresponding to the lower part of the screen” is assumed to have a transmittance of 50% in the nth field period and 100% in the (n + 2) th field period.

  In general, the right-eye image and the left-eye image belonging to the same frame are almost the same image only by shifting the object (element / object) by the amount of parallax. Here, in order to simplify the description, the right-eye image and the left-eye image are uniform images that differ only in luminance.

  Here, for comparison, the time response of the transmittance of the liquid crystal when the transmittance is 30% in the n-th field period of “the transmittance of the liquid crystal corresponding to the lower part of the screen” in FIG. 3 is represented by a broken line. . In the n-th to (n + 1) th field period, the time response (dashed line) of the transmittance of the liquid crystal from the transmittance of 30% to the transmittance of 100% and the transmission of the liquid crystal from the transmittance of 50% to the transmittance of 100% It shows that the slope of the rise is different from the time response of the rate (solid line).

  “Light emission amount” in FIG. 3 represents the light emission amount of the solid-state light source 14 (see FIGS. 1 and 2). The amount of light emitted from the solid-state light source 14 has its rising slope α adjusted according to the transmittance of the liquid crystal corresponding to the lower part of the screen.

  Here, the control unit 4 (see FIG. 1), after the scan for updating the field image before the update to the field image after the update is completed, is updated after being updated a plurality of times including the scan. The light emission amount of the solid light source 14 is adjusted until scanning for further updating the field image is started. For example, the control unit 4 is configured to perform a solid state in the (n + 1) th field period included in the period from the end of the screen scan R in the nth field period to the start of the screen scan L in the (n + 2) th field period. The light emission amount of the light source 14 is adjusted. The same applies to the (n + 3) th field period.

  Further, the control unit 4 turns off the solid-state light source 14 so that the fall of the light emission amount becomes steep. That is, when scanning a plurality of pixels based on an image different from the (n + 1) field period in the (n + 2) field period, which is a field period in which the solid-state light source 14 is turned off after the (n + 1) field period, the control unit 4 controls that the solid-state light source 14 is turned off at the start of scanning in the (n + 2) -th field period. Specifically, the control unit 4 determines the light emission amount of the solid-state light source 14 from the start of the screen scan for updating the field image before update to the field image after update until the end of the scan. Set below a predetermined threshold. For example, the control unit 4 sets the light emission amount of the solid light source 14 to 0 in the (n + 2) -th field period including the period from when the screen scanning L is started to when it is ended. Thereby, since the control part 4 can divide | segment clearly the field period which makes the solid light source 14 light-emit, and the field period which makes the solid light source 14 light-extinguish, it can avoid generating crosstalk.

FIG. 4 is a table showing the light emission amount according to the average value of the transmittance of the liquid crystal. In FIG. 4, the average value of the transmittance of the liquid crystal corresponding to the lower part of the screen on which the field image before the update is displayed (hereinafter referred to as “the transmittance before the image update”) and the field image after the update are displayed. A table (LUT) shows the relationship between the average value of the transmittance of the liquid crystal corresponding to the lower part of the screen (hereinafter referred to as “transmittance after image update”) and the light emission amount. The LUT is stored in advance in the storage unit 3 and is referred to by the control unit 4. Based on this LUT, the control unit 4 adjusts the amount of light emitted from the solid light source 14 at the rising edge. The light emission amount is expressed as light emission amount L = (1−e ^−αt ), where t is time. This equation is an example.

  Here, the rising slope α of the light emission amount is synchronized with the rising slope (time response) of the transmittance of the liquid crystal corresponding to the lower part of the screen, and the average value of the transmittance before the image update and the It is determined according to the average value of the transmittance. For example, when the average value of the transmittance before the image update is 50% and the average value of the transmittance after the image update is 100%, the rising slope α of the light emission amount is set to 1.0. Further, for example, when the average value of the transmittance before the image update is 30% and the average value of the transmittance after the image update is 100%, the rising slope α of the light emission amount is determined to be 1.2. .

  As described above, the control unit 4 determines the transmittance and the (n + 1) th field in the field period immediately before the nth field period of the pixel scanned in the last period among the nth field period. Based on the difference from the transmittance in the period, the time response of the rise of the light emission amount when the solid-state light source 14 starts lighting in the (n + 1) th field period is controlled. When the field period is divided into a plurality of times, the time response of the rise of the light emission amount is controlled only when the lighting is started in the first field period, so that the liquid crystal display device displays a bright screen. Obtainable.

  FIG. 5 is a diagram for comparing the amount of light transmitted through the glasses when the light emission amount is constant and when the light emission amount is changed. The luminance of the image projected on the screen 18 (see FIG. 2) is multiplied by the light emission amount of the solid light source 14 (see FIG. 2) and the liquid crystal transmittance of the liquid crystal panels 30 to 32 (see FIG. 2). Value.

  FIG. 5A shows that in the (n + 1) th field period (see FIG. 4), the light emission amount of the solid state light source 14 is constant (starts sharply at the start of the field period and sharply at the end of the field period). It is a figure in the case of falling). In this case, due to the time response of the transmittance of the liquid crystal, a difference occurs between the transmittance of the liquid crystal corresponding to the upper part of the screen and the transmittance of the liquid crystal corresponding to the lower part of the screen. (Lower drawing) According to this luminance difference, crosstalk occurs in which the image before update remains in the image after update as an afterimage.

  On the other hand, FIG. 5B is a diagram when the light emission amount is changed in accordance with the rising inclination α. In this case, the rising slope α of the light emission amount is synchronized with the rising slope (time response) of the transmittance of the liquid crystal corresponding to the lower part of the screen (upper figure), and thus the transmittance of the liquid crystal corresponding to the upper part of the screen. Even if there is a difference between the transmittance of the liquid crystal corresponding to the lower part of the screen, the difference in luminance between the upper part and the lower part of the screen is reduced (lower figure). Thereby, according to this luminance difference, the crosstalk that remains in the image after the update as an afterimage is prevented from occurring.

  As described above, the projector 1 includes the light source unit that is turned off in the first field period and turned on in the subsequent second field period, and the plurality of pixels, and each of the first field period and the second field period includes the light source unit. The liquid crystal panels 13R, 13G, and 13B that scan a plurality of pixels and transmit the light from the light source unit with the transmittance controlled for each pixel, and the last field among the first field period divided into a plurality are scanned. A control unit 4 for controlling a time response of the rise of the light emission amount when the light source unit starts lighting in the second field period based on a time response of the transmittance of at least one pixel included in the pixel group. .

  As a result, the liquid crystal display device (projector) adjusts the light amount of the light source unit according to the time response of the transmittance of the liquid crystal, thereby reducing the difference in brightness between the upper and lower portions of the screen on which the image is projected (displayed). Crosstalk can be reduced.

  In a more preferred embodiment, the control unit 4 starts lighting the solid-state light source 14 in the (n + 1) th field period based on the time response of the transmittance of the last one pixel scanned in the nth field period. Controls the time response of the rise of the emitted light amount. The same applies to the (n + 2) th field period and the (n + 3) field period. Since the time response of the rise of the light emission amount when the solid-state light source 14 starts lighting is controlled, the liquid crystal display device can thereby prevent crosstalk from occurring.

  FIG. 6 is a time chart showing the operation according to the temperature of the liquid crystal display device. FIG. 6 shows screen scanning, polarity inversion signal, right eyeglasses, left eyeglasses, liquid crystal transmittance corresponding to the upper part of the screen, liquid crystal transmittance corresponding to the lower part of the screen, and light emission amount. Is expressed for each liquid crystal temperature. The control unit 4 adjusts the light emission amount of the solid light source 14 according to the temperature of the liquid crystal of the liquid crystal panels 13R, 13G, and 13B.

  Here, the broken lines in “the transmittance of the liquid crystal corresponding to the upper portion of the screen” and “the transmittance of the liquid crystal corresponding to the lower portion of the screen” represent the time response (optical response) of the transmittance of the liquid crystal at room temperature. . The solid line represents the time response (optical response) of the transmittance of the liquid crystal, which is at a high temperature with respect to normal temperature. A broken line in “light emission amount” represents the light emission amount when the liquid crystal is at room temperature. The solid line represents the amount of light emitted when the liquid crystal is at a higher temperature than normal temperature.

  As described above, when the liquid crystal is at a high temperature with respect to the normal temperature, the time response of the transmittance of the liquid crystal becomes faster. Therefore, the LUT (see FIG. 4) stored in advance in the storage unit 3 is determined for each temperature. May be. In this case, the control unit 4 uses the temperature information notified from the temperature sensor 6 via the main board 2 and the LUT for each temperature, and the rise time of the light emission amount when the solid-state light source 14 starts lighting. Control the response. By controlling the time response of the rise of the amount of light emission according to the temperature of the liquid crystal panel, the liquid crystal display device can reduce the difference in brightness between the upper and lower parts of the screen on which the image is displayed and reduce crosstalk. it can.

[Second Embodiment]
A second embodiment of the present invention will be described in detail with reference to the drawings. The differential amplifier circuit 5 (see FIG. 1) may be configured as follows. Only the differences from the first embodiment will be described below.

  FIG. 7 is a block diagram illustrating a configuration example of the liquid crystal display device. Unlike the configuration example shown in FIG. 1, the configuration example shown in FIG. 7 does not require the I / V conversion circuit 63 and the photodiode (PD). Instead, in the configuration example shown in FIG. 7, the differential amplifier circuit 5 measures the voltage difference between both ends of the electrical resistor that constitutes a part of the light source driving circuit 70, and determines the light emission amount of the solid light source 14. The measured voltage difference is output to the control unit 4 as the corresponding voltage. As a result, the circuit scale of the liquid crystal display device can be reduced, and the cost can be reduced.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  For example, the projector 1 may display an image as a liquid crystal display without using the screen 18.

  Note that the program for realizing the liquid crystal display device and the liquid crystal display system described above may be recorded on a computer-readable recording medium, and the program may be read into the computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible disk, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” is a volatile memory (RAM) inside a computer system that becomes a server or a client when a program is transmitted through a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included. The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

DESCRIPTION OF SYMBOLS 1 ... Projector (liquid crystal display device), 2 ... Main board, 3 ... Memory | storage part, 4 ... Control part, 5 ... Differential amplifier circuit, 11 ... Cross dichroic prism, 12 ... Collimator lens, 13R, 13G, 13B ... Liquid crystal panel 14R, 14G, 14B ... LED (solid light source), 15 ... first dichroic film, 16 ... second dichroic film, 17 ... projection lens, 18 ... screen, 62 ... temperature sensor, 63 ... I / V conversion circuit, 64 ... Light quantity detection unit, 70 ... Light source drive circuit, 71 ... FET, 72 ... FET, 80 ... 3D glasses, 81 ... 3D glasses circuit, 82 ... Right eye glasses, 83 ... Left eye glasses

Claims (9)

A light source unit that is turned off in the first field period and turned on in the subsequent second field period;
A liquid crystal panel having a plurality of pixels, scanning the plurality of pixels in the first field period and the second field period, and transmitting light from the light source unit at a transmittance controlled for each pixel;
Based on the time response of the transmittance of at least one pixel included in the pixel group scanned in the last period among the first field period divided into a plurality, the light source unit is turned on in the second field period. A control unit for controlling the time response of the rise of the light emission amount when starting,
A liquid crystal display device comprising:   The liquid crystal panel scans the plurality of pixels based on the same image in the first field period and the second field period, and transmits light from the light source unit with transmittance controlled for each pixel. The liquid crystal display device according to claim 1.   The control unit is configured to increase a light emission amount when the light source unit starts lighting in the second field period based on a time response of the transmittance of the last one pixel scanned in the first field period. The liquid crystal display device according to claim 1, wherein a time response is controlled.   The control unit scans the plurality of pixels based on an image different from the second field period in a third field period in which the light source unit is turned off after the second field period. 4. The liquid crystal display device according to claim 1, wherein the unit is controlled to be turned off at the start of scanning in the third field period. 5.   The control unit is configured to transmit the transmittance in the field period immediately before the first field period and the transmission in the second field period of the pixel scanned in the last period among the first field period divided into a plurality. 5. The time response of the rise of the light emission amount when the light source unit starts lighting in the second field period based on a difference from the rate. 5. The liquid crystal display device according to item.   The said control part controls the time response of the rise of the light emission amount when the said light source part starts lighting in the said 2nd field period according to the temperature of the said liquid crystal panel. 6. The liquid crystal display device according to any one of items 5.   The liquid crystal display device according to claim 1, wherein the light source unit is a solid light source. The liquid crystal display device according to any one of claims 1 to 7, wherein an image for the left eye and an image for the right eye are displayed alternately.
Glasses for alternately transmitting the image for the left eye and the image for the right eye displayed by the liquid crystal display device according to a timing signal notified from the liquid crystal display device;
A liquid crystal display system comprising: A display method in a liquid crystal display device,
A step in which the light source unit is turned off in the first field period and turned on in the subsequent second field period;
A liquid crystal panel having a plurality of pixels, scanning the plurality of pixels in each of the first field period and the second field period, and transmitting light from the light source unit at a transmittance controlled for each pixel; ,
When the light source unit starts lighting in the second field period based on the time response of the transmittance of the pixels scanned in the last period among the first field period divided into a plurality of the first field period A step of controlling the time response of the rise of the light emission amount;
A display method characterized by comprising:

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