JP4797521B2 - Electro-optical device, illuminance detection method of electro-optical device, and electronic apparatus - Google Patents

Description

  The present invention relates to an illuminance detection method, a luminance control method, an electro-optical device, and an electronic apparatus suitable for a display device that controls display luminance.

  The liquid crystal panel is configured by sealing liquid crystal between two substrates such as a glass substrate and a quartz substrate. Each substrate is provided with an electrode, and an image signal is supplied to the electrode. The optical characteristics of the liquid crystal between the electrodes of each substrate change according to the image signal. That is, by applying a voltage based on the image signal to the liquid crystal between the electrodes of each substrate, the alignment of the liquid crystal molecules is changed. Thereby, the light transmittance in each pixel changes according to the image signal, and the image display according to the image signal is performed.

  In order to display with high brightness in such a liquid crystal panel, a backlight is generally provided on the back of the liquid crystal panel. As such a backlight, an apparatus for improving the uniformity of illumination using a light guide plate has been developed. By illuminating the display area of the liquid crystal panel with the backlight, the display on the display area can be observed with sufficient luminance.

  By the way, the visibility of the display on the liquid crystal panel changes according to the ambient brightness. For example, the brighter the ambient light, the easier it is to see the display when the illumination in the display area is brighter. Conversely, when the ambient light is sufficiently dark, it is not necessary to make the display area brighter than necessary.

Patent Document 1 discloses a technique for detecting ambient light and controlling the brightness of a backlight based on feedback information in order to provide an easy-to-see display regardless of ambient brightness.
JP 2003-78838 A

  By the way, in the apparatus of patent document 1, a discrete component is employ | adopted as an optical sensor which detects ambient light (external light). For this reason, it is necessary to mount an optical sensor on a flexible printed circuit board, resulting in an increase in man-hours and costs.

  Therefore, it is conceivable to form an optical sensor on a substrate constituting a display panel such as a liquid crystal panel. However, since the display panel employs a light-transmitting substrate, the light emitted from the backlight or the self-light emitting element also enters the photosensor for detecting ambient light. For this reason, there has been a problem that the detection accuracy of the ambient light is lowered, and there is a problem in luminance control. Note that a light-shielding film may be formed between the backlight or the self-luminous element and the optical sensor. However, even in this case, a sufficient effect can be obtained because the light propagates through the light-transmitting substrate. Absent.

  This is a problem common to all display devices that detect external light and perform luminance control.

  The present invention provides an illuminance detection method, a brightness control method, an electro-optical device, and an electronic apparatus that can enable accurate detection of external light by temporarily stopping light emission of a light emitting unit when external light is detected. The purpose is to provide.

  An illuminance detection method according to the present invention includes a light emission stop procedure for stopping emission of the display light from a display unit that emits display light, and an illuminance detection procedure for detecting the illuminance of external light around the display unit. It is characterized by that.

  According to such a configuration, the emission stop procedure stops emission of display light from the display unit. Next, in the illuminance detection procedure, the illuminance of external light around the display unit is detected. At the time of detecting the illuminance of the external light, the emission of the display light is stopped, and the display light is prevented from adversely affecting the detection of the illuminance of the external light. Thereby, the illuminance of external light can be accurately detected.

  Further, the display light is obtained by light from an illumination device that illuminates the display unit.

  According to such a configuration, emission of display light can be stopped by turning off the illumination device.

  Further, the display light is obtained by light from a light emitting element constituting the display portion.

  According to such a configuration, emission of display light can be stopped by stopping light emission of the light emitting element.

  The light emission stop procedure and the illuminance detection procedure are performed during a blanking period of an image signal supplied to the display unit.

  According to such a configuration, it is possible to stop emission of display light and detect external light without affecting the image display of the display unit.

  The display unit is configured by a liquid crystal panel in which liquid crystal is sealed between the first and second substrates, and the light emission stop procedure includes a procedure of turning off the backlight that illuminates the display unit, In the illuminance detection procedure, the illuminance of the outside light is detected based on an output of an optical sensor configured by a thin film diode formed on the first substrate.

  According to such a configuration, display light emission can be stopped and external light can be detected without being affected by the backlight of the liquid crystal panel.

  Further, the luminance control method according to the present invention includes a light emission stop procedure for stopping emission of the display light from the display unit that emits display light, and an illuminance detection procedure for detecting illuminance of external light around the display unit, And a light emission control procedure for controlling the luminance of the display light based on the detected illuminance of the external light.

  According to such a configuration, when the external light is detected, the display light is turned off, and the external light can be detected without being affected by the display light. The illuminance of the external light detected in the illuminance detection procedure is accurate. It is. In the light emission control procedure, the luminance of the display light is controlled based on the detected illuminance of outside light. In this way, display brightness can be controlled in accordance with external light. Thereby, the visibility of a display can be improved. Further, the display luminance can be prevented from becoming unnecessarily high, and the power consumption can be reduced.

  Further, the display light is obtained by light from an illumination device that illuminates the display unit.

  According to such a configuration, it is possible to stop the emission of the display light by turning off the lighting device, and to control the luminance of the lighting device according to the external light.

  Further, the display light is obtained by light from a light emitting element constituting the display portion.

  According to such a configuration, the emission of the display light can be stopped by stopping the light emission of the light emitting element, and the luminance of the light emitting element can be controlled according to the external light.

  The light emission stop procedure and the illuminance detection procedure are performed during a blanking period of an image signal supplied to the display unit.

  According to such a configuration, it is possible to stop emission of display light and detect external light without affecting the image display of the display unit, and it is possible to observe the image display with appropriate brightness. .

  Further, the display unit is configured by a liquid crystal panel in which liquid crystal is sealed between the first and second substrates, and the light emission stop procedure includes a procedure of turning off the backlight that illuminates the display unit, The illuminance detection procedure detects the illuminance of the external light based on an output of an optical sensor configured by a thin film diode formed on the first substrate, and the light emission control procedure detects the detected external light. The brightness of the backlight is controlled based on the illuminance of light.

  According to such a configuration, display light emission can be stopped and external light can be detected without being affected by the backlight of the liquid crystal panel, and the luminance of the backlight is appropriately controlled according to the external light. be able to.

  The electro-optical device according to the present invention includes a display unit that emits display light, a light sensor that detects the illuminance of ambient light around the display unit, and the display when the illuminance of the ambient light is detected by the light sensor. And a light emission stopping means for stopping the emission of the display light of the part.

  According to such a configuration, the optical sensor detects the illuminance of external light during the period in which the emission of the display light is stopped by the light emission stopping unit. That is, during a period when only external light is incident on the optical sensor, the optical sensor detects the illuminance of external light. Therefore, a detection result based on the illuminance of external light that is not affected by the display light is obtained from the optical sensor.

  The electro-optical device according to the present invention includes a display unit that emits display light, an optical sensor that detects the illuminance of external light around the display unit, and the detection of the illuminance of the external light by the optical sensor. A light emission stopping unit that stops emission of display light from the display unit, and a light emission control unit that controls the luminance of the display light based on the detected illuminance of the external light.

  According to such a configuration, the light emission control unit controls the luminance of the display light based on the illuminance of external light. Since the emission of the display light is stopped during the detection period of the illuminance of the external light, the detected illuminance of the external light is accurate without being affected by the display light. Thereby, it is possible to obtain an appropriate display luminance corresponding to the external light, and it is possible to reduce power consumption while being excellent in visibility.

  In the electro-optical device according to the aspect of the invention, the display unit includes a liquid crystal panel in which liquid crystal is sealed between the first and second substrates, and the display light illuminates the display unit. The light sensor is obtained by a light, and the optical sensor is formed of a thin film diode formed on the first substrate.

  According to such a configuration, the optical sensor detects external light from the liquid crystal panel with the backlight turned off. Since the backlight is turned off when the external light is detected, the detected external light is accurate. The brightness of the backlight is controlled according to the detected accurate illuminance of outside light. Thereby, it is possible to observe a display with appropriate brightness according to the external light.

  Further, an electronic apparatus according to the present invention is characterized by using the electro-optical device.

  According to such a configuration, it is possible to accurately detect external light and control display luminance, thereby improving display visibility and reducing power consumption.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of a display device in which an electro-optical device according to a first embodiment of the invention is incorporated. 2 is a cross-sectional view showing a cross-sectional structure when a liquid crystal panel is employed as the electro-optical device 12 of FIG.

<First Embodiment>
In FIG. 1, the display device 11 includes an electro-optical device 12. When a liquid crystal panel is used as the electro-optical device 12, the electro-optical device 12 includes a display panel 21 and an illumination device 22. Note that a self-luminous display panel may be employed as the electro-optical device, and in this case, an illumination device is not necessary. FIG. 2 shows a configuration example when a liquid crystal panel is employed as the display panel 21. Note that FIG. 2 shows an example of a small number of pixels in order to simplify the description, but the number of pixels is not particularly limited.

  The display panel 21 is configured by enclosing a liquid crystal 25 between an element substrate 23 and a counter substrate 24 that transmit light. The element substrate 23 and the counter substrate 24 arranged so as to face each other are bonded together by a sealing material 26.

  The display panel 21 has a display screen 13, and an effective display area 14 surrounded by a broken line in FIG. 1 is provided at the center of the display screen 13. The effective display area 14 includes, for example, a plurality of scanning lines (not shown) extending in the vertical direction and a plurality of data lines (not shown) extending in the horizontal direction. A pixel is formed corresponding to the intersection of the plurality of data lines.

  A reflective layer 27 and an overcoat layer 28 are laminated on the element substrate 23, and a pixel electrode (ITO) 29 constituting a pixel is disposed on the overcoat layer 28. A counter electrode (common electrode (ITO)) 30 is provided on the counter substrate 24 side. On the pixel electrode 29 of the element substrate 23, an alignment film (not shown) that has been subjected to a rubbing process is provided in contact with the liquid crystal 25. On the other hand, the counter substrate 24 is also provided with an alignment film (not shown) that is in contact with the liquid crystal 25 and is subjected to rubbing treatment. Each alignment film is made of a transparent organic film such as a polyimide film. A light shielding film 31 is formed on the counter substrate 24 along the data lines and the scanning lines.

  A polarizing plate 32 is provided on the observation surface side of the counter substrate 24, and a polarizing plate 33 is provided on the surface opposite to the element formation surface of the element substrate 23. The polarizing plates 32 and 33 are set to the polarization axis corresponding to the rubbing direction of the alignment film formed on the element substrate 23 and the counter substrate 24.

  In the display panel 21, an image signal is supplied to the data line, and a scanning signal is supplied to the scanning line. In this way, each pixel is driven based on the image signal, the light transmittance is changed, and image display is performed.

  The lighting device 22 emits light from below the element substrate 23 of the display panel 21. In the display panel 21, image display is performed by controlling the transmittance of the emitted light of the illumination device 22 in accordance with the image signal in the effective display area 14.

  The illuminating device 22 is provided with a light emitting diode (hereinafter referred to as an LED) 35 composed of a plurality of point light sources constituting a light source. A light guide plate 36 is provided on the side of the LED 35 and below the effective display area 14 of the display panel 21. The LED 35 is disposed on the side surface of the light guide plate 36 and can emit light into the light guide plate 36.

  The light guide plate 36 has a substantially plate shape, and is disposed so that one side surface (incident surface) thereof faces the output surface of the LED 35. The light guide plate 36 is formed of, for example, a transparent acrylic resin, and the three side surfaces other than the one side facing the LED 35 are made of a material having high reflection characteristics or scattering characteristics, for example, a reflection layer such as a white printing layer. Is formed. From one side surface of the light guide plate 36 facing the LED 35, light from the LED 35 enters and is guided into the light guide plate 36.

  In addition to the acrylic resin, the light guide plate 36 is made of a polycarbonate resin having transparency or translucency, various resins such as amorphous polyolefin resin, inorganic materials such as glass, or various composites thereof. Can be used.

  The light guide plate 36 reflects and scatters incident light by the bottom and side reflection layers, and emits light from the top surface. An optical sheet 37 including a diffusion sheet and a prism sheet is disposed on the upper surface of the light guide plate 36. The optical sheet 37 diffuses the light from the light guide plate 36 and emits the light upward. An effective display area 14 of the display panel 21 is disposed on the optical sheet 37. Thereby, the light from the optical sheet 37 enters the effective display area 14 of the display panel 21.

  A non-display area 15 is provided around the effective display area 14. In this non-display area 15, a light receiving element arrangement area 16 of an illuminance detection circuit 19 described later is provided. The light receiving element arrangement region 16 has a region that transmits light from the upper surface (observation surface) side of the counter substrate 24 into the substrate.

  In the present embodiment, the outside light sensor 4 is provided in the light receiving element arrangement region 16. The sensor 4 for external light is formed on the element substrate 23 by a process of a so-called polysilicon type thin film transistor, a low temperature polysilicon type thin film transistor which is preferably manufactured at a temperature of about 600 ° C. or less. External light from the observation surface side of the counter substrate 24 is incident on the external light sensor 4.

  The external light sensor 4 outputs an output corresponding to the incident light. That is, the external light sensor 4 receives external light and outputs an output based on the illuminance of the external light. The output of the external light sensor 4 is given to the illuminance detection circuit 19.

  FIG. 3 shows an example of the external light sensor 4. FIG. 4 is a graph showing the relationship between incident light intensity and output. The light receiving element of the external light sensor 4 can be represented by an equivalent circuit of a parallel circuit of a diode D1 such as a PIN diode and a capacitor C1.

  A voltage from the power supply 41 is applied to the capacitor C1 via the switch. The terminal voltage of the capacitor C1 decreases due to the photogenerated charge generated in the diode D1 by the incidence of light. A voltage drop amount Vdrop indicated by an arrow in FIG. 4 is obtained as a sensor output via the amplifier 43 at the output terminal 44.

  Vdrop corresponding to the sensor output is expressed by the following equation (1).

Vdorp = V0 exp (-t / RC) (1)
Further, when detecting a voltage drop of the capacitor C1 by a change in the pulse time width, an output element having a threshold voltage is connected to the switch 42, and when the voltage of the capacitor C1 reaches the threshold, the output element What is necessary is just to output a signal. In this case, the output element can output a pulse signal having a time width inversely proportional to the intensity of light incident on the diode D1.

  In addition, although it demonstrated as what uses the voltage according to incident light as sensor output, you may use the electric current output according to incident light, or the output from which the time width of a pulse changes according to incident light is used. May be.

  The illuminance detection circuit 19 drives and controls the external light sensor 4 by generating a power supply voltage, a drive signal, a reset signal, and the like for driving the external light sensor 4. The illuminance detection circuit 19 performs conversion in which the output linearly changes according to the light intensity with respect to the output of the above formula (1), and then outputs it as an illuminance detection signal. That is, the illuminance detection circuit 19 outputs an illuminance detection signal in which the relationship between the light intensity and the output changes linearly as shown in FIG.

  The illuminance detection signal from the illuminance detection circuit 19 is given to the light emission control unit 18. The light emission control unit 18 controls the light emission unit of the display panel 21 based on the illuminance detection signal. That is, in the case of the liquid crystal panel of FIG. 2, the light emission control unit 18 controls the light emission of the illumination device 22. The light emission control unit 18 determines the brightness of the illumination device 22 based on the illuminance detection signal, generates a light emission control signal for lighting the illumination device 22 with the determined brightness, and outputs the light emission control signal to the illumination device 22. It has become.

  For example, if the illuminance detection signal indicates that the external light is relatively bright, the light emission control unit 18 can also increase the brightness of the illumination device 22 according to the brightness of the external light. . The light emission control unit 18 may turn off the illumination device 22 and use the display panel 21 as a reflection type when it is indicated that the external light is brighter than a predetermined threshold. The illumination device 22 emits light with brightness based on the light emission control signal.

  In the present embodiment, the illuminance detection circuit 19 and the light emission control unit 18 are controlled by the display driver 17. The display driver 17 drives each pixel in the effective display area 14 and controls image display. For example, the display driver 17 generates a horizontal synchronization signal and a vertical synchronization signal, and controls scanning and supply of the image signal to the pixels. The display driver 17 also generates various timing signals including a vertical blanking pulse indicating a vertical blanking period.

  In the present embodiment, the light emission control unit 18 and the illuminance detection circuit 19 are given a timing signal from the display driver 17 so as to turn off the illumination device 22 during an external light detection period in which the illuminance of external light is detected. It has become. Furthermore, the light emission control unit 18 determines the brightness of the illumination device 22 based on the illuminance detection signal during the extinguishing period of the illumination device 22.

  For example, the light emission control unit 18 is given a vertical blanking pulse and turns off the lighting device 22 during the vertical blanking period, and the illuminance detection circuit 19 performs the vertical blanking period, that is, the lighting device 22 is turned off. The illuminance of external light is detected.

  In addition, when employ | adopting the backlight which uses LED (light emitting diode) as a light emission source as the illuminating device 22, the light emission control part 18 controls the drive voltage (backlight voltage) of LED, and is a backlight. Dimming is possible.

  Next, the operation of the embodiment configured as described above will be described with reference to FIGS. FIG. 6 is a timing chart showing an external light detection period, and FIG. 7 is a flowchart showing an illuminance detection method and a luminance control method.

  The display device 11 controls the brightness of the illumination device 22 so that the illumination device 22 in the electro-optical device 12 emits light with an appropriate brightness according to ambient light (external light). That is, the light emission control unit 18 controls the illumination device 22 to emit light with a predetermined luminance based on the illuminance detection signal from the illuminance detection circuit 19. In the present embodiment, the illumination device 22 is turned off during the outside light detection period so that the illuminance of the outside light can be accurately detected.

  That is, the light emission control unit 18 and the illuminance detection circuit 19 determine whether or not it is a period for measuring external light in step S1 of FIG. The blanking period occurs at a 1/60 second period, and it is not necessary to detect outside light during the entire blanking period. The display driver 17 outputs a timing signal indicating an external light measurement period to the light emission control unit 18 and the illuminance detection circuit 19 so as to detect the illuminance of external light at an appropriate timing.

  In the external light measurement period, the light emission control unit 18 and the illuminance detection circuit 19 detect that the vertical blanking period is reached by the vertical blanking pulse from the display driver 17 (step S2), and this blanking period is determined. The ambient light detection period. The light emission control unit 18 controls the lighting device 22 to turn off the light (step S3). The illuminance detection circuit 19 drives the external light sensor 4 and acquires a sensor output (step S4). For example, the illuminance detection circuit 19 receives the sensor output after 2 milliseconds have elapsed from the start of the blanking period. The sensor output may be either an analog value or a digital value.

  During the period for detecting the illuminance of external light by the illuminance detection circuit 19, the illumination device 22 is turned off. Therefore, only ambient light (external light) of the display panel 21 is incident on the external light sensor 4, and the illuminance detection circuit 19 can accurately detect the illuminance of external light.

  Note that it is only necessary that the light emission of the lighting device is stopped in the external light detection period, and the external light detection period does not necessarily coincide with the blanking period. For example, only a part of the blanking period may be set as the outside light detection period.

  The illuminance detection circuit 19 outputs an illuminance detection signal based on the sensor output to the light emission control unit 18. The light emission control part 18 determines the brightness of the illuminating device 22 based on the detection result of the illumination intensity of external light (step S5). When the blanking period ends, the light emission control unit 18 proceeds from step S6 to step S7, and outputs a light emission control signal for instructing the determined brightness. The illuminating device 22 lights with the brightness based on the light emission control signal (step S8).

  For example, when it is detected that the external light is bright during the illuminance detection period, the light emission control unit 18 increases the brightness of the illumination device 22 according to the brightness of the external light. The control in this case of FIG. 6 is shown.

  The backlight voltage in FIG. 6 is a voltage generated according to the light emission control signal and applied to the backlight which is the lighting device 22. In the external light detection period, the backlight voltage decreases and the backlight is turned off. When the external light detection period that is the blanking period ends, a backlight voltage higher than that before the external light detection period is generated according to the light emission control signal. Thereby, the backlight emits light that is brighter than before the external light detection period.

  In addition, the light emission control part 18 can perform various brightness control according to the brightness of external light. For example, when the outside light is extremely bright, the illumination device 22 (backlight) may be turned off and the liquid crystal display may be operated in the reflection mode. Further, as described above, when the external light is moderately bright, the backlight is also brightened to improve the visibility of the liquid crystal display. On the other hand, when the outside light is relatively dark, the backlight is also darkened to enable a display that is easy on the eyes and easy to see. In this case, power consumption can also be reduced.

  As described above, in the present embodiment, during the period for detecting the illuminance of the external light, the light emission of the backlight and the self-light-emitting element is stopped, and the brightness of the external light is accurately detected by the external light sensor. Is possible. In addition, since the period during which light emission is stopped is set as the blanking period, it is possible to detect the illuminance and control the display brightness without affecting the display.

  Further, the brightness of the backlight light is controlled according to the brightness of the external light detected with high accuracy, and a display device with excellent visibility can be obtained. In addition, it is possible to prevent the backlight from becoming brighter than necessary, and power consumption can be reduced.

  In the above-described embodiment, the example of controlling the brightness of the backlight according to the external light has been described. However, when a self-luminous display panel is used, the light emission is performed according to the detected external light. The display brightness of the body may be controlled.

  Furthermore, not only the brightness control but also the γ value of the projected image and the picture itself may be controlled according to the external light. Further, it can be applied not only to video but also to control of audio and the like. For example, when it is detected that the external light has become darker than a predetermined brightness, it is possible to change the ringing tone of the mobile phone to the ringing tone for night.

<Second Embodiment>
FIG. 8 is a timing chart for explaining the illuminance detection method and the luminance control method employed in the second embodiment of the present invention. The present embodiment has the same hardware configuration as that of the first embodiment, and the light emission control method is different.

  In the present embodiment, the light emission control unit 18 gradually changes the brightness of the illumination device 22 based on the illuminance detection result of the external light. In addition, the light emission control unit 18 controls the brightness of the illumination device 22 after a predetermined period has elapsed from the external light detection period, not the display period immediately after the external light detection period.

  In the example of FIG. 8, the backlight voltage for controlling the brightness of the illumination device 22 (backlight) is changed after about 1.5 vertical periods have elapsed from the external light detection period. Moreover, the change in the backlight voltage is gradual, and the desired brightness is reached after about 0.5 vertical period after the change in brightness is started.

  Other configurations and operations are the same as those in the first embodiment.

  As described above, in the present embodiment, the brightness is gradually changed over a predetermined period from the detection of external light, and it is possible to prevent a sense of incongruity from occurring due to a sudden change in display luminance.

<Third Embodiment>
FIG. 9 is a timing chart for explaining the illuminance detection method and the luminance control method employed in the third embodiment of the present invention. The present embodiment has the same hardware configuration as that of the first embodiment, and the light emission control method is different.

  In the present embodiment, the light emission control unit 18 and the illuminance detection circuit 19 set a period longer than the blanking period as the external light detection period. FIG. 9 shows an example in which one vertical period is set as the external light detection period.

  In this embodiment, since the external light detection period is longer than the blanking period, the accuracy of detecting the illuminance of external light can be further improved. As shown in FIG. 9, if the external light detection period is about one field period, the illumination device 22 is only turned off for 1/60 seconds, and there is no visual problem.

  In FIG. 9, the external light detection period is set to one field period, but a period shorter than one field period may be set, or a longer period may be set if there is no visual discomfort. In addition, the start and end timings of the external light detection period can be set as appropriate. Various timings can be considered, such as once every few seconds to once every few minutes as needed.

  Other configurations, operations, and effects are the same as those in the first embodiment.

<Fourth embodiment>
10 to 13 relate to a fourth embodiment of the present invention, and FIG. 10 is a sectional view showing a sectional structure when a liquid crystal panel is adopted as an electro-optical device according to the fourth embodiment of the present invention. is there. FIG. 11 is a circuit diagram showing an illuminance detection and luminance control circuit employed in the electro-optical device according to the fourth embodiment. FIG. 12 is a timing chart showing a reference light detection period and an external light detection period. FIG. 13 is a flowchart showing an illuminance detection method and luminance control method according to the fourth embodiment. In FIG. 10 and FIG. 11, the same components as those in FIG. 2 and FIG.

  The external light sensor 4 shown in FIG. 10 is formed on a liquid crystal panel manufactured by low-temperature polysilicon technology. For this reason, the light detection current of the external light sensor 4 is relatively small, and it is difficult to obtain sufficient accuracy. In addition, sensors manufactured by low-temperature polysilicon technology have large individual differences, and it is conceivable that external light detection accuracy is low.

  Therefore, in the present embodiment, the external light can be detected with high accuracy by calibrating the detection result of the external light using the output of the sensor for detecting the reference light.

  As the reference light, various kinds of light can be adopted, but when applied to a liquid crystal panel using a backlight, the backlight light can be used as the reference light. For a display panel using a self light emitting element, light from the self light emitting element can be used as reference light.

  The display panel 51 of FIG. 10 is different from the display panel 21 in the first embodiment in that the backlight reference sensor 2 and the light shielding film 3 are added. That is, the display panel 51 is provided with the backlight reference sensor 2 and the outside light sensor 4 in the light receiving element arrangement region 16. The backlight reference sensor 2 and the external light sensor 4 are formed on the element substrate 23 by low-temperature polysilicon technology. A light shielding film 3 is formed above the backlight reference sensor 2, and the light shielding film 3 prevents external light from the observation surface side of the counter substrate 24 from entering the backlight reference sensor 2. The backlight reference sensor 2 receives light from the illumination device 22 that passes through the element substrate 23. Further, external light from the observation surface side of the counter substrate 24 enters the external light sensor 4.

  In the present embodiment, the illuminance detection and luminance control circuit 8 shown in FIG. 11 is employed instead of the illuminance detection circuit 19 and the light emission control unit 19 of FIG.

  In FIG. 11, the backlight 1 corresponds to the illumination device 22 of FIG. The backlight 1 can irradiate the display panel with backlight light.

  The backlight reference sensor 2 and the external light sensor 4 each output an output corresponding to incident light. The backlight reference sensor 2 is configured such that the outside light is blocked by the light shielding film 3 and the backlight light from the backlight 1 is incident. The backlight reference sensor 2 outputs an output based on the illuminance of the backlight light.

  In addition, external light is incident on the external light sensor 4. Also in the present embodiment, when the external light is detected, the backlight 1 is turned off, and the external light sensor 4 outputs an output based on the illuminance of the external light.

  The backlight 1 includes, for example, an LED, and can control the illuminance with relatively high accuracy. The backlight reference sensor 2 and the outside light sensor 4 are formed by a semiconductor process at positions close to each other, and have substantially the same characteristics.

  In the present embodiment, these characteristics are used to detect external light with high accuracy. As described later, the known illuminance of the backlight light whose illuminance is controlled with high accuracy is detected by the backlight reference sensor 2, and the output of the external light sensor is calibrated based on the detection result. The detection accuracy is improved.

  Each sensor output from the backlight reference sensor 2 and the outside light sensor 4 is given to a comparator 5 as a calibration means. The comparator 5 compares the sensor outputs from the backlight reference sensor 2 and the external light sensor 4 and outputs the comparison result to the backlight controller 6 as the light emission control means. For example, the comparator 5 may output a ratio between the output of the backlight reference sensor 2 that has detected predetermined reference light and the output of the external light sensor 4 as a comparison result. Now, it is assumed that the sensor characteristics of the backlight reference sensor 2 and the external light sensor 4 have linear characteristics that pass 0 as shown in FIG. Then, a reference light having a known predetermined brightness is generated in the backlight 1, and this reference light is detected by the backlight reference sensor 2. On the other hand, the external light sensor 4 detects external light. In this case, it is determined how many times the brightness of the outside light is higher than the brightness of the reference light according to how many times the sensor output of the sensor 4 for external light is the sensor output of the sensor 2 for backlight reference. Can do. As described above, if the brightness of the reference light is controlled with high accuracy and the characteristics of the backlight reference sensor 2 and the external light sensor 4 are linearly the same characteristic passing through 0, the brightness of the external light is increased. It can be detected with accuracy. Even when the sensor characteristics do not pass through 0, it is obvious that external light can be detected in the same manner as long as it is linear.

  The comparator 5 may output the ratio of the sensor outputs of the backlight reference sensor 2 and the external light sensor 4 as a comparison result as it is, and the absolute brightness of the external light can be determined based on the comparison between the sensor outputs. A signal indicating the brightness of the obtained external light may be obtained as a comparison result.

  The comparison result of the comparator 5 is given to the backlight controller 6. The backlight controller 6 generates a backlight control signal for controlling the brightness of the backlight 1 based on the comparison result of the comparator 5 and outputs the backlight control signal to the backlight 1.

  For example, when the comparison result indicates that the external light is relatively bright, the backlight controller 6 can also increase the brightness of the backlight 1 according to the brightness of the external light. Further, the backlight controller 6 may turn off the backlight 1 and use the display panel 51 as a reflection type when it is indicated that the external light is brighter than a predetermined threshold. The backlight 1 emits light with brightness based on the backlight control signal.

  In the present embodiment, the illuminance detection circuit 7 and the backlight controller 6 are controlled by the display driver 17, and the backlight 1 is turned off during the external light detection period in which the illuminance of external light is detected. Yes.

  Next, the operation of the embodiment configured as described above will be described with reference to FIGS.

  Also in this embodiment, external light detection and display luminance control may be performed only for a predetermined period. In the present embodiment, after external light is detected, reference light (backlight) is detected in order to calibrate the detection result of external light.

  In the present embodiment, an external light detection period is set at the blanking period. That is, when the backlight controller 6 of the illuminance detection and luminance control circuit 8 in FIG. 11 detects that the external light detection period has been reached by the blanking pulse (steps S1 and S2), the backlight 1 is detected by the backlight control signal. Is turned off (step S3).

  On the other hand, external light incident from the observation surface side of the counter substrate 24 passes through the counter substrate 24 and enters the sensor 4 for external light. The external light sensor 4 detects the brightness of the external light (step S4). The output of the external light sensor 4 is given to the comparator 5. In the external light detection period, the backlight 1 is turned off, and the external light sensor 4 can reliably detect the illuminance of the external light.

  When the blanking period ends, the backlight controller 6 shifts the processing from step S6 to step S11, and controls the backlight 1 to emit reference light having a predetermined luminance. The backlight light enters the backlight reference sensor 2. As shown in FIG. 12, the reference light detection period is set to a display period immediately after the outside light detection period. The backlight reference sensor 2 detects the brightness of the backlight light. The sensor output of the backlight reference sensor 2 is given to the comparator 5.

  The comparator 5 obtains the ratio between the sensor outputs from the backlight reference sensor 2 and the external light sensor 4 (step S12), and outputs the comparison result to the backlight controller 6.

  For example, it is assumed that the illuminance by the backlight 1 is 10,000 lux as the reference light, and the output of the backlight reference sensor 2 by this backlight light is 5V. On the other hand, it is assumed that the output of the external light sensor 4 that has detected the external light is 6V. In this case, the comparator 5 outputs 6/5 = 1.2. That is, in this case, the brightness of the external light is 12,000 lux which is 1.2 times the reference light.

  The backlight controller 6 determines the brightness of the backlight 1 based on the comparison result from the comparator 5. When the reference light detection period ends, the backlight controller 6 outputs a backlight control signal for turning on the backlight 1 with the determined brightness (step S13). When the reference light detection period ends in this way, the backlight 1 is lit with brightness based on the high-precision external light illuminance obtained during the external light detection period (step S14).

  As described above, also in this embodiment, after the backlight is turned off, the brightness of the external light is detected by the external light sensor. After detecting the outside light, the reference light whose brightness is controlled with high accuracy is detected by a backlight reference sensor having substantially the same characteristics as the outside light sensor. Since the backlight is turned off during the external light detection period, it is possible to reliably obtain sensor output based on external light. Further, the sensor output of the external light sensor is calibrated by comparing the sensor output of the backlight reference sensor and the sensor output of the external light sensor. Thereby, it is possible to detect the brightness of external light with high accuracy.

  Further, the brightness of the backlight light is controlled according to the brightness of the external light detected with high accuracy, and a display device with excellent visibility can be obtained. In addition, it is possible to prevent the backlight from becoming brighter than necessary, and power consumption can be reduced.

  In the above embodiment, the backlight reference sensor and the ambient light sensor detect the illuminance by the same method, but different detection methods may be adopted. Further, in the above embodiment, the example in which the external light is detected first and the reference light is detected later has been described. The external light may be detected later. Further, the backlight brightness control after calibration may be performed during the blanking period. In this case, it is possible to prevent the brightness from changing during the display period.

  In the present embodiment, the backlight reference sensor and the external light sensor are provided separately, but the reference light detection period and the external light detection period are set to different times. By sharing these sensors and using one sensor in a time-sharing manner, the reference light and the outside light may be detected. If one sensor is shared, a sensor that prevents the entry of outside light by the light shielding film 3 cannot be made, but the brightness detected in the reference light detection period is sufficiently higher than the brightness detected in the outside light detection period It is only necessary to calibrate based on the reference light.

  Polycrystalline thin-film sensors such as PIN diodes manufactured by low-temperature polysilicon technology have larger individual variations in light sensitivity than individual variations in bulk silicon, so that they can be used as sensors for detecting ambient light (external light). Conventionally, it was necessary to calibrate the sensitivity. On the other hand, in the present embodiment, the sensor output for detecting the external light is automatically calibrated by using the output of the sensor for detecting the reference light. External light detection is possible.

  In the above-described embodiment, the example of controlling the brightness of the backlight according to the external light has been described. However, when a self-luminous display panel is used, the light emission is performed according to the detected external light. The display brightness of the body may be controlled. In this case, display light itself by self-light emission may be used as the reference light.

  Furthermore, not only the brightness control but also the γ value of the projected image and the picture itself may be controlled according to the external light. Further, it can be applied not only to video but also to control of audio and the like. For example, when it is detected that the external light has become darker than a predetermined brightness, it is possible to change the ringing tone of the mobile phone to the ringing tone for night.

<Fifth embodiment>
FIG. 14 relates to a fifth embodiment of the present invention, and is a cross-sectional view showing a cross-sectional structure when an EL (electroluminescence) panel is adopted as an electro-optical device according to the fifth embodiment.

  A low-temperature polysilicon layer 73 is formed on the substrate 71. The substrate 71 and the substrate 72 are opposed to each other with the organic EL layer 74 interposed therebetween. The organic EL layer 74 constitutes R, G, and B pixels. A light shielding film 75 is formed on the substrate 72.

  In the present embodiment, the reference light reference sensor 76 is formed on the substrate 73 so as to face one of the R, G, and B pixels of the organic EL layer 74 or one by one. A light shielding film 77 is formed on the substrate 72 facing the reference light reference sensor 76. As a result, the reference light reference sensor 76 is prevented from entering external light and can detect the light emission intensity of each pixel of the organic EL layer 74.

  An external light sensor 78 is formed at the end of the substrate 71. The external light sensor 78 can detect external light.

  In the present embodiment, when the ambient light illuminance is detected by the ambient light sensor 78, the organic EL layer 74 that is a light emitting element is turned off.

  The electro-optical device configured as described above also includes an illuminance detection circuit, a light emission control unit, and a display driver similar to those in FIG. The reference light reference sensor 76 detects the emission intensity of the organic EL layer 74 as the intensity of the reference light. Next, in the external light detection period, the light emission of the organic EL layer 74 is stopped, and the external light sensor 78 detects the illuminance of the external light. Then, the sensor output of the external light sensor 78 is calibrated using the sensor output of the reference light reference sensor 76. In this way, it is possible to accurately detect outside light and control display luminance.

  Further, an electronic apparatus using the above electro-optical device is also included in the present invention. FIG. 15 is a perspective view showing an example of an electronic device, and shows the appearance of a mobile phone. As shown in FIG. 15, the above-described electro-optical device, for example, a liquid crystal display device is used for the display unit 201 of the mobile phone 200 as an electronic device.

  In addition, as an electronic device, for example, a projection display device including a light source, a light valve that modulates light emitted from the light source, and an optical system for projecting light modulated by the light valve It is. In addition, other electronic devices include televisions, viewfinder type / monitor direct view type video tape recorders, car navigation devices, pagers, electronic notebooks, calculators, word processors, workstations, videophones, POS terminals, digital Examples include a still camera and a device equipped with a touch panel. Needless to say, the electro-optical device according to the present invention is applicable to these various electronic devices.

  The electro-optical device of the present invention is not limited to a passive matrix type liquid crystal display panel but an active matrix type liquid crystal panel (for example, a liquid crystal display panel including a TFT (thin film transistor) or a TFD (thin film diode) as a switching element). It is possible to apply to the same. In addition to liquid crystal display panels, electroluminescence devices, organic electroluminescence devices, plasma display devices, electrophoretic display devices, devices using electron emission (such as Field Emission Display and Surface-Conduction Electron-Emitter Display), DLP ( The present invention can be similarly applied to various electro-optical devices such as Digital Light Processing (aka DMD: Digital Micromirror Device).

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the outline | summary of the display apparatus incorporating the electro-optical apparatus which concerns on the 1st Embodiment of this invention. FIG. 2 is a cross-sectional view illustrating a cross-sectional structure when a liquid crystal panel is employed as the electro-optical device 12 in FIG. 1. The equivalent circuit diagram which shows an example of the sensor 4 for external light. The graph which shows the relationship between incident light intensity and an output. The graph for demonstrating the sensor output from which the relationship between light intensity and an output changes linearly. The timing chart which shows an external light detection period. The flowchart which shows the detection method of an illumination intensity, and the control method of a brightness | luminance. The timing chart for demonstrating the illumination intensity detection method and luminance control method which are employ | adopted as the 2nd Embodiment of this invention. The timing chart for demonstrating the illumination intensity detection method and luminance control method which are employ | adopted as the 3rd Embodiment of this invention. Sectional drawing which shows the cross-sectional structure at the time of employ | adopting a liquid crystal panel as an electro-optical apparatus which concerns on the 4th Embodiment of this invention. FIG. 10 is a circuit diagram showing an illuminance detection and luminance control circuit employed in an electro-optical device according to a fourth embodiment. 4 is a timing chart showing a reference light detection period and an external light detection period. The flowchart which shows the detection method of the illumination intensity which concerns on 4th Embodiment, and the control method of a brightness | luminance. Sectional drawing which shows sectional structure at the time of employ | adopting EL (electroluminescence) panel as an electro-optical apparatus which concerns on the 5th Embodiment of this invention. The perspective view which shows the example of an electronic device.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 11 ... Display apparatus, 12 ... Display panel, 14 ... Effective display area, 17 ... Display driver, 18 ... Light emission control part, 19 ... Illuminance detection circuit.

Claims (6)

A display unit for emitting display light;
A control unit for controlling emission of display light from the display unit;
A light receiving portion for receiving incident light;
In an electro-optical device including an illuminance detection unit that detects illuminance of light received by the light receiving unit,
The control unit stops emission of display light from the display unit in a blanking period of an image signal supplied to the display unit,
The light receiving unit receives external light around the display unit during the blanking period,
The control unit emits reference light from the display unit,
The light receiving unit receives the reference light,
The illuminance detection unit detects the illuminance of the external light based on a comparison between the external light received during the blanking period and the received reference light .
The electro-optical device , wherein the control unit causes display light having brightness based on the detected illuminance of the external light to be emitted from the display unit . An illumination device for illuminating the display unit;
The electro-optical device according to claim 1 , wherein the display light is obtained by illumination light from the illumination device. The display unit includes a light emitting element,
The electro-optical device according to claim 1 , wherein the display light is obtained by light from the light emitting element. The display unit includes a liquid crystal panel in which liquid crystal is sandwiched between first and second substrates,
The lighting device is composed of a backlight,
The light receiving unit is composed of an optical sensor configured by a thin film diode formed on the first substrate,
The electro-optical device according to claim 2 , wherein the illuminance detection unit detects the illuminance of the external light based on an output of the optical sensor. A display unit for emitting display light;
A control unit for controlling emission of display light from the display unit;
A light receiving portion for receiving incident light;
In an illuminance detection method for an electro-optical device comprising an illuminance detection unit that detects the illuminance of light received by the light receiving unit,
In the blanking period of the image signal supplied to the display unit, the emission of display light from the display unit is stopped,
During the blanking period, external light around the display unit is received,
Reference light is emitted from the display unit,
Receiving the reference light;
Based on a comparison between the external light received during the blanking period and the received reference light, the illuminance of the external light is detected ,
An illuminance detection method for an electro-optical device, wherein display light having brightness based on the detected illuminance of the external light is emitted from the display unit . An electronic device characterized by using the electro-optical device according to any one of claims 1 to 4.

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