JP2006118965A - Photodetection circuit, electro-optical device, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photodetection circuit capable of detecting accurately environmental light in a simple manufacturing process, and also provide an electro-optical device using it, and electronic equipment. <P>SOLUTION: A photodiode 310A outputs a current I1 corresponding to the environmental light and background light. A shielding film 350 is provided on the surface where the environmental light of a photodiode 310B enters. The photodiode 310B outputs a current I2 corresponding to the background light. A differential current Δi flows in a capacitor 320. Consequently, the potential of a node Q becomes correspondingly the quantity of the environmental light. A switching element 330 for switching on/off in the period of a reset signal RESET is provided in parallel with the capacitor 320. A NAND circuit 340 operates inversion of a logical product between the potential of the node Q and a reference signal REF, and outputs the operation result through inverters 350, 360, 370 as a pulse signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photodetection circuit capable of accurately detecting ambient light capable of detecting illuminance, an electro-optical device using the photodetection circuit, and an electronic apparatus.

  In a transmissive or anti-transmissive liquid crystal device, a backlight is provided on the back of the liquid crystal panel. Light from the backlight is modulated by the liquid crystal panel. A plurality of pixels are formed in a matrix on the liquid crystal panel, and an image is displayed by adjusting the transmittance for each pixel. In such a liquid crystal device, the power consumption of the backlight is large. Therefore, a photodetection circuit may be provided to reduce power consumption of the liquid crystal device, and the intensity of the backlight may be adjusted in accordance with the magnitude of the ambient light (for example, Patent Document 1 and Patent Document 2). Furthermore, it is known that a light detection circuit is formed on a glass substrate of a liquid crystal device for the purpose of reducing parts (Patent Document 3).

JP-A-5-265401 (Claims 1 and 2) JP-A-6-11713 (Claim 1 and FIG. 1) Japanese Unexamined Patent Publication No. 2000-131137

By the way, when a light detection circuit is provided on a glass substrate, light from the ambient light to be detected and the backlight enters the light detection circuit. For this reason, it is necessary to isolate | separate both. In order to easily isolate the optical sensor from the backlight components, an appropriate light-shielding film may be disposed under the semiconductor film.
However, a precise manufacturing process is required for forming a semiconductor film, such as forming a base with very little unevenness. For this reason, when the light shielding film is disposed under the semiconductor film, there is a concern that the manufacturing process becomes complicated and the yield decreases.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a photodetector circuit capable of accurately detecting ambient light with a simple manufacturing process, an electro-optical device using the same, and an electronic apparatus. It is to provide.

  In order to solve the above-described problems, a light detection circuit according to the present invention is one in which target light and disturbance light are incident as incident light, and outputs a first current corresponding to the amount of incident light. A sensor, a light-shielding film is provided on a surface on which the target light is incident, and a sub-sensor that outputs a second current according to the amount of the disturbance light. The main sensor and the sub-sensor are connected via a connection point. The differential current between the first current and the second current is taken out as an output signal from the connection point.

  According to the present invention, since the light incident on the sub sensor is only the background light, the magnitude of the differential current is in accordance with the amount of the target light. Further, since the light shielding film may be formed on the surface on which the target light is incident, the photodetection circuit can be configured easily. Note that the target light means light to be detected, and corresponds to, for example, the environmental light in the embodiment. On the other hand, disturbance light means light that is not a detection target, and corresponds to, for example, background light in the embodiment.

  Further, another photodetection circuit according to the present invention is one in which target light and disturbance light are incident as incident light, and a plurality of unit circuits in which a main sensor and a sub sensor are connected in series via a connection point. And a light-shielding film provided on the surface of the sub sensor on which the target light is incident, the main sensor outputs a first current corresponding to the amount of the incident light, and the front sub-sensor outputs the disturbance A second current corresponding to the amount of light is output, the connection points provided in each of the plurality of unit circuits are connected to each other, and the total current of the first current and the total current of the second current are The differential current is taken out as an output signal. According to the present invention, since the plurality of main sensors and the plurality of sub sensors are used, the target light can be detected more accurately. In addition, since the magnitude of the differential current can be increased, the noise margin can be improved.

As a more preferred aspect, the plurality of unit circuits are arranged along at least one of a row direction and a column direction, and the main sensor and the sub sensor are alternately arranged in the row direction or the column direction. It is desirable. In this case, the main sensor and the sub sensor can be arranged in a distributed manner, so that the ambient light irradiation conditions can be made uniform, and the influence of the temperature distribution and the manufacturing variations are less likely to occur. It becomes possible. Thereby, the detection precision of object light can be improved significantly. A plurality of single circuits may be arranged in a matrix, and in this case, the main sensor and the sub sensor may be arranged in a staggered manner.
Further, as a specific mode of the main sensor and the sub sensor, it is preferable that the photoelectric conversion characteristics of the main sensor and the photoelectric conversion characteristics of the sub sensor are equal, and each of the main sensor and the sub sensor includes a photo It is composed of a diode, and the photodiode is reverse-biased.

  In the above-described photodetector circuit, a capacitive element having one end connected to the connection point and the other end connected to a power supply, and a switching element provided in parallel with the capacitive element and turned on and off at a predetermined cycle are provided. Preferably, the voltage signal at the connection point is taken out as an output signal. According to the present invention, since both ends of the capacitive element are short-circuited at a predetermined cycle by the switching element, the voltage signal at the connection point is a signal indicating illuminance. In general, since the output currents of the main sensor and the sub sensor are very small, it is necessary to use a resistor having a large resistance value in order to generate a voltage signal using the resistor, which increases the circuit area. On the other hand, when a capacitive element is used, an element with a small low capacitance value sufficient for charging a minute current is sufficient. Therefore, the circuit scale can be greatly reduced. In addition, since the high-resistance resistor acts as an antenna, noise may be mixed in. However, since the photodetection circuit of the present invention uses a capacitive element, the illuminance can be accurately detected with a large noise margin.

In addition, it is preferable that the above-described light detection circuit includes a voltage frequency conversion circuit that converts the voltage signal into a frequency signal, and takes out the frequency signal as the output signal instead of the voltage signal. In this case, since the frequency signal is output from the photodetection circuit, the noise margin is improved and the signal is easily handled.
More specifically, the voltage frequency conversion circuit includes a logic circuit that calculates a logical product of the voltage signal and a reference signal having a cycle shorter than the ON / OFF cycle of the switching element and outputs a binarized signal. And the binarized signal is output as the frequency signal. According to this configuration, since the binarized signal that is a frequency signal can be output by the logic circuit, the configuration can be simplified.
In addition, the photodetection circuit includes a counting unit that counts the binarized signal and outputs a count data signal indicating a count result per unit time, and outputs the count data signal as the output signal. preferable. In this case, it can be output as a digital signal.

  Next, an electro-optical device according to the present invention is provided with the above-described light detection circuit, a plurality of data lines, and a plurality of scanning lines, each corresponding to the intersection of the data lines and the scanning data. An electro-optical panel having a plurality of pixel circuits including a liquid crystal element whose transmittance is changed by a general action, a light source that irradiates light from one surface of the electro-optical panel to the other surface, And a dimming circuit that adjusts the amount of light based on the output signal of the photodetection circuit. According to the present invention, since the light amount of the light source can be adjusted according to the ambient illuminance detected by the light detection circuit, for example, the light emission luminance of the light source is increased in a bright place, while the light emission luminance of the light source is increased in a dark place. Can be lowered. As a result, an easy-to-view screen can be displayed and power consumption can be reduced.

  Next, another electro-optical device according to the present invention is provided with a plurality of data lines, a plurality of scanning lines, each corresponding to the intersection of the data lines and the scanning data, and optically operated by an electric action. A pixel circuit including an electro-optical element whose characteristics change, a control circuit that generates a plurality of control signals, a drive signal based on the plurality of control signals, and the drive signals that are the plurality of data lines and the plurality of data A driving circuit that outputs to at least one of the scanning lines, a main sensor that outputs a first current corresponding to the amount of incident light including target light and disturbance light, and a light-shielding film on a surface on which the target light is incident And outputs a second current corresponding to the amount of the disturbance light, and is connected in series with the main sensor via a connection point, and has a sub sensor, one end connected to the connection point, and the other end connected to a power source. A capacitive element and the capacitive element; Comprising a photodetector circuit and a switching element for turning on and off based on the first signal provided to the column, characterized in that the first signal was also used as one of the plurality of control signals.

According to the present invention, since a special configuration for generating the first signal (for example, the reset signal RESET of the embodiment) is not necessary, the configuration can be simplified and the cost of the electro-optical device can be reduced. Can be reduced. Furthermore, when the electro-optical panel is provided with data lines, scanning lines, pixel circuits, driving circuits, and light detection circuits, it is possible to reduce the number of input terminals of the electro-optical panel and cope with a narrow pitch. Become. The photodetector circuit further includes a logic circuit that calculates a logical product with a second signal (for example, the reference signal REF of the embodiment) having a shorter cycle than the first signal and outputs a binarized signal, The first signal and the second signal may be combined with any of the plurality of control signals. In this case, since a special configuration for generating the first signal and the second signal is not necessary, the configuration can be simplified, and the cost of the electro-optical device can be reduced.
Next, an electronic apparatus according to the present invention preferably includes the above-described electro-optical device. Examples of the electronic device include a personal computer, a cellular phone, and an information portable terminal.

<1. First Embodiment>
The electro-optical device according to the first embodiment of the present invention uses liquid crystal as an electro-optical material. The electro-optical device 1 includes a liquid crystal panel AA (an example of an electro-optical panel) as a main part. The liquid crystal panel AA is bonded to an element substrate on which a thin film transistor (hereinafter referred to as “TFT”) is formed as a switching element and a counter substrate with the electrode formation surfaces facing each other and maintaining a certain gap. However, liquid crystal is sandwiched between the gaps.

  FIG. 1 is a block diagram showing the overall configuration of the electro-optical device 1 according to the first embodiment. The electro-optical device 1 includes a liquid crystal panel AA, a light control circuit 500, a backlight 600, a signal generation circuit 700, a control circuit 800, and an image processing circuit 900. The liquid crystal panel AA is a transmissive type, but may be a transflective type. The signal generation circuit 700 generates a reset signal RESET and a reference signal REF. These signals are used in the optical sensor circuit 300. The liquid crystal panel AA includes an image display area A, a scanning line driving circuit 100, a data line driving circuit 200, an optical sensor circuit 300, and a counting circuit 400 on the element substrate. The control circuit 800 generates an X transfer start pulse DX and an X clock signal XCK and supplies them to the data line driving circuit 200, and also generates a Y transfer start pulse DY and a Y clock signal YCK and supplies them to the scanning line driving circuit 100. To do. In the image display area A, a plurality of pixel circuits P1 are formed in a matrix, and the transmittance can be controlled for each pixel circuit P1. Light from the backlight 600 is emitted through the pixel circuit P1. Thereby, gradation display by light modulation becomes possible. The dimming circuit 500 adjusts so that the backlight 600 emits light with the luminance according to the illuminance data 400a. The illuminance data 400a is data indicating the illuminance of the environment.

  By the way, the visibility of the display image depends on the brightness of the environment. For example, under natural daylight, it is necessary to set the light emission luminance of the backlight 600 high and display a bright screen. On the other hand, in a dark environment at night, a clear image can be displayed even if the light emission activation of the backlight 600 is not as high as during the day. Therefore, it is desirable to adjust the light emission luminance of the backlight 600 according to the illuminance of the ambient light. The optical sensor circuit 300 and the counting circuit 400 provided in the liquid crystal panel AA are used for measuring the illuminance of ambient light.

  FIG. 2 shows a circuit diagram of the optical sensor circuit 300. As shown in this figure, the photodiodes 310A and 310B are connected in series between the high potential side power source VH and the low potential side power source VL. The photodiodes 310A and 310B are composed of, for example, PIN diodes and are reverse-biased. The photodiodes 310A and 310B can be created if there is a process for forming a semiconductor region, a process for forming an N-type region, and a process for forming a P-type region, so that the pixel circuit P1 / scanning line driving circuit / data line driving circuit is configured. It is formed on the element substrate by the same process as the TFT to be performed. The photoelectric conversion characteristics of the photodiode 310A and the photoelectric conversion characteristics of the photodiode 310B are substantially equal if they are formed close to each other on the element substrate and have the same element size. The photoelectric conversion characteristics define the relationship between the amount of input light and the magnitude of the output current.

  Ambient light and background light enter the photodiode 310A as incident light. The photodiode 310A outputs a first current i1 corresponding to the amount of incident light. Here, ambient light corresponds to target light that is a measurement target, and background light corresponds to disturbance light that is not a measurement target. The photodiode 310A functions as a main sensor that outputs a first current i1 corresponding to the amount of incident light including ambient light and disturbance light.

  On the other hand, in the photodiode 310B, a light shielding film 350 is provided on the surface on which the ambient light is incident. The light shielding film 350 has a function of shielding light. Accordingly, ambient light is not incident on the photodiode 310B, and only background light is incident. The photodiode 310B outputs a second current i2 corresponding to the amount of background light. That is, the photodiode 310B functions as a sub sensor that outputs the second current i2 according to the amount of disturbance light. Further, as the light shielding film 350, a film provided on the substrate of the liquid crystal panel A can be used. This is because the light shielding film 350 only needs to block the ambient light irradiated from above the liquid crystal panel A. Therefore, a wiring metal layer, a reflection metal layer (in the case of a reflective liquid crystal display device), or the like can be used for the light shielding film 350. Alternatively, a black matrix film provided on the color filter side may be used.

The photodiodes 310A and 310B are connected via a node Q, and a capacitor 320 is provided between the node Q and the ground GND (low potential side power supply). From node Q, differential current Δi (= I1−I2) between first current I1 and second current I2 is output to capacitor 320. Here, the first current I1 includes the ambient light component Ia and the background light component Ib, and the second current I2 includes only the background light component Ib. Therefore, the differential current Δi is given by the following equation (1).
Δi = I1−I2 = (Ia + Ib) −Ib = Ia (1)

  However, in order for Formula (1) to hold, it is necessary that the same amount of background light is incident on the photodiodes 310A and 310B, and that the photoelectric conversion characteristics of the photodiodes 310A and 310B are equal. Since the photodiodes 310A and 310B are manufactured by the same manufacturing process, the difference in their photoelectric conversion characteristics is acceptable. Further, since the photodiodes 310A and 310B are arranged close to each other, a difference in the amount of background light can be ignored. In other words, the photodiodes 310A and 310B are arranged close to each other to the extent that the light amount difference is acceptable. The magnitude of the difference current Δi depends on the amount of ambient light. As described above, in the present embodiment, the photodiode 310A that outputs the current I1 corresponding to the amounts of ambient light (target light) and background light (disturbance light), the light shielding film 350 that blocks ambient light, and the background light ( Since the photodiode 310B that outputs the current I2 corresponding to the amount of disturbance light) and the differential current Δi are output, the amount of ambient light (illuminance) can be accurately detected. In addition, the light-shielding film 350 only needs to be provided above the semiconductor film because it only needs to block ambient light irradiated from above the liquid crystal panel A. For this reason, a manufacturing process is simplified and a yield can be improved.

  Further, one end of the switching element 330 is connected to the node Q, and the other end is connected to the ground GND. Charge is accumulated in the capacitor 320 due to the differential current Δi and the potential of the node Q rises. However, when the switching element 330 is turned on, the accumulated charge is discharged and the potential of the node Q becomes the ground level. Here, the relationship between the potentials VH, VL, and GND is VH> GND> VL. Next, the switching element 330 is configured by a TFT, and is turned on when a reset signal REST supplied to the gate thereof is active (high level), and is turned off when the reset signal REST is inactive (low level). The node Q is connected to one input terminal of the NAND circuit 340, and the other input terminal is supplied with the reference signal REF The cycle of the reference signal REF is shorter than the cycle of the reset signal RESET. Is output as a pulse signal 300a through three inverters 350, 360, and 370.

  FIG. 3 shows a timing chart of the optical sensor circuit 300. In this example, the value of the differential current Δi output by the node Q at low illuminance is i1, and the value of the differential current Δi output by the node Q at high illuminance is i2. When the reset signal RESET becomes active during the period from time t1 to time t2, the switching element 330 is turned on, and both ends of the capacitor 320 are short-circuited. As a result, the potential of the node Q becomes the ground level. When time t2 is reached, switching element 330 is turned off and charging of capacitor 320 is started. For this reason, the potential of the node Q rises from time t2. In this case, since the capacitor 320 is charged with a constant current, the waveform of the potential change at the node Q is a straight line. The slope of the potential waveform increases as the current value increases. In this example, since i1> i2, the rise time Ta is shorter than the rise time Tb.

  The NAND circuit 340 functions as a logic circuit that calculates the logical product of the potential of the node Q and the reference signal REF. For this reason, when the value of the differential current Δi is i1, the pulse signal 300a is output in the period from the time ta to the time t3, and when the value of the differential current Δi is i2, the time from the time tb to the time t3 is output. The pulse signal 300a is output during the period. Here, when the number of pulse signals 300a generated in the period from time t2 to time t3 is compared, the number is 8 when the current value is i1, and is 3 when the current value is i2. As described above, the current value i1 is the value of the differential current Δi obtained when the ambient illuminance is high and the current value i2 is low. Therefore, the frequency of the pulse signal 300a is an indicator of the illuminance of the environment, and the higher the illuminance, the higher the frequency. In other words, the optical sensor circuit 300 outputs the pulse signal 300a indicating the illuminance of the environment as a frequency signal. Although simply expressed in FIG. 3, the pulse signal 300 a is actually output when the potential of the node Q reaches the operating point of the NAND circuit 340.

  The value of the current output from the photoelectric conversion elements such as the photodiodes 310A and 320B is extremely small. A resistor may be used to convert a current into a voltage, but a resistor having a large resistance value needs to be formed in order to extract a voltage signal from a minute current. Such an area occupied by the resistor is large, which causes a problem in layout. Furthermore, there is a possibility that noise acts due to the resistor acting as an antenna, and it is not easy to accurately detect the illuminance. According to the present embodiment, since the differential current Δi is integrated and converted into a voltage signal using the capacitor 320, the illuminance can be accurately detected with a small occupied area. Further, since the reference signal REF is supplied from the outside and the illuminance is detected in the form of frequency, the noise margin is improved and the handling of the signal becomes easy. The pulse signal 300a obtained in this way is supplied to the counting circuit 400 shown in FIG.

  FIG. 4 shows a configuration example of the counting circuit 400. The counting circuit 400 includes, for example, a counter circuit 410 whose count value is reset by a reset signal RESET, and a latch circuit 420 that latches count data indicating the count result of the counter circuit 410 with the reset signal RESET. The output data of the latch circuit 420 is output to the dimming circuit 500 as illuminance data 400a.

Next, the image display area A will be described. In the image display region A, as shown in FIG. 5, m (m is a natural number of 2 or more) scanning lines 2 are formed in parallel along the X direction, while n (n is (Natural number of 2 or more) number of data lines 3 are arranged in parallel along the Y direction. In the vicinity of the intersection of the scanning line 2 and the data line 3, the gate of the TFT 50 is connected to the scanning line 2, while the source of the TFT 50 is connected to the data line 3 and the drain of the TFT 50 is connected to the pixel electrode 6. Connected. Each pixel includes a pixel electrode 6, a counter electrode (described later) formed on the counter substrate, and a liquid crystal sandwiched between the two electrodes. As a result, the pixels are arranged in a matrix corresponding to each intersection of the scanning line 2 and the data line 3.
Further, scanning signals Y1, Y2,..., Ym are applied in a pulse-sequential manner to each scanning line 2 to which the gate of the TFT 50 is connected. Therefore, when a scanning signal is supplied to a certain scanning line 2, the TFT 50 connected to the scanning line is turned on, so that the data signals X1, X2,..., Xn supplied from the data line 3 at a predetermined timing are After being written in order to the corresponding pixels, they are held for a predetermined period.

Since the orientation and order of liquid crystal molecules change according to the voltage level applied to each pixel, gradation display by light modulation becomes possible. For example, the amount of light passing through the liquid crystal is limited as the applied voltage increases in the normally white mode, whereas the amount of light that passes through the liquid crystal is reduced as the applied voltage increases in the normally black mode. As a whole, light having contrast according to the image signal is emitted for each pixel. For this reason, a predetermined display becomes possible.
In order to prevent the held image signal from leaking, a storage capacitor 51 is added in parallel with a liquid crystal capacitor formed between the pixel electrode 6 and the counter electrode. For example, the voltage of the pixel electrode 6 is held by the storage capacitor 51 for a time that is three orders of magnitude longer than the time when the source voltage is applied, so that the holding characteristics are improved, so that a high contrast ratio is realized.

  FIG. 6 shows a timing chart of the scanning line driving circuit 100 and the data line driving circuit 200. The scanning line driving circuit 100 sequentially shifts the Y transfer start pulse DY of one frame (1F) cycle in accordance with the Y clock signal YCK to generate the scanning signals Y1, Y2,. The scanning signals Y1 to Ym are sequentially activated in each horizontal scanning period (1H). The data line driving circuit 200 transfers the X transfer start pulse DX of the horizontal scanning period in accordance with the X clock signal XCK, and internally generates sampling signals S1, S2,. Then, the data line driving circuit 200 samples the image signal VID using the sampling signals S1, S2,... Sn to generate data signals X1, X2,.

  As described above, in the present embodiment, since the light emission luminance of the backlight 600 is adjusted using the light detection circuit 300, the brightness of the screen can be controlled in accordance with the environmental illuminance, and the consumption of the electro-optical device 1 can be controlled. Electric power can be reduced. In addition, since the optical sensor circuit 300 and the counting circuit 400 are formed on the liquid crystal panel AA using elements such as TFTs, the electro-optical device 1 can be greatly reduced in size. Furthermore, the photodetection circuit 300 can accurately detect the illuminance because the differential current Δi is charged by the capacitor 320 and the signal corresponding to the illuminance of the environment is extracted. In addition, since the final output signal of the optical sensor circuit 300 is given as the pulse signal 300a, the illuminance data 400a can be easily obtained by measuring the number of pulses per unit time.

<2. Second Embodiment>
Next, an electro-optical device 1 according to a second embodiment of the invention will be described. The electro-optical device 1 according to the second embodiment is the same as that of the first embodiment except that the Y transfer start pulse DY is used instead of the reset signal RESET and the Y clock signal YCK is used instead of the reference signal REF. The configuration is the same as that of the optical device 1.
FIG. 7 shows a configuration of the electro-optical device 1 according to the second embodiment. As shown in this figure, in the electro-optical device 1 of this embodiment, the signal generation circuit 700 is omitted. This is because the reset signal RESET is also used as the Y transfer start pulse DY, and the reference signal REF is also used as the Y clock signal YCK. Note that the X transfer start pulse DX may be used instead of the reset signal RESET, and the X clock signal XCK may be used instead of the reference signal REF. That is, various signals for driving the pixel circuit P1 may be used as the reset signal RESET and the reference signal REF.

  However, since the frequency of the Y clock signal YCK is lower than that of the X clock signal XCK, the Y transfer start pulse DY and the Y clock signal YCK are used in place of the reset signal RESET and the reference signal REF from the viewpoint of reducing power consumption. preferable. In addition, since the change in environmental illuminance is sufficiently longer than one frame period, which is the period of the Y transfer start pulse DY, even if the Y transfer start pulse DY and the Y clock signal YCK are used, the change in environmental illuminance follows. Thus, the light emission luminance of the backlight 600 can be adjusted.

As described above, in the present embodiment, since various signals for driving the pixel circuit P1 are also used as the reset signal RESET and the reference signal REF, it is necessary to generate a special signal in order to operate the optical sensor circuit 300. Disappear. As a result, the signal generation circuit 600 can be omitted to simplify the configuration. Further, since it is not necessary to provide an input terminal for supplying the reset signal RESET and the reference signal REF to the liquid crystal panel AA, it is possible to cope with a narrow pitch of the input terminals.
In each embodiment described above, the optical sensor circuit 300 outputs the pulse signal 300a. However, the potential of the node Q may be output as a voltage signal. The effective value of this voltage signal is a value corresponding to the illuminance. Therefore, the light control circuit 500 may control the light emission luminance of the backlight 600 based on the voltage signal. In addition, in each of the above-described embodiments, the photodetection circuit that detects the illuminance of the environment may be considered to include not only the photosensor circuit 300 but also the counting circuit 400.

<3. Modified Example of Optical Sensor Circuit>
Next, a modified example of the optical sensor circuit 300 will be described. The optical sensor circuits 301 and 302 described below can be replaced with the optical sensor circuit 300 of the first embodiment and the second embodiment described above.
(1) First Modification FIG. 8 is a circuit diagram of an optical sensor circuit 301 according to a first modification. The optical sensor circuit 301 shown in the figure is configured similarly to the optical sensor circuit 300 shown in FIG. 2 except that a plurality of photodiodes 310A and 310B are used. The sensor unit 31 of the optical sensor circuit 301 includes a plurality of unit circuits U. Each of the plurality of unit circuits U includes a photodiode 310A and a photodiode 310B. The node Q, which is a connection point between the photodiode 310A and the photodiode 310B, is connected to each other, and a differential current Δi is extracted therefrom.

In this case, the difference current Δi is given as a difference between the sum of the first currents I1 output from each of the plurality of photodiodes 310A and the sum of the second currents I2 output from each of the plurality of photodiodes 310B. By using a plurality of unit circuits U in this way, it is possible to generate a differential current Δi with higher accuracy and improve the detection accuracy of ambient light.

(2) Second Modification FIG. 9 is a circuit diagram of an optical sensor circuit 302 according to the second modification. The optical sensor circuit 302 shown in the figure has the same configuration as the optical sensor circuit 301 shown in FIG. 8 except that the sensor unit 32 is used instead of the sensor unit 31.
In the sensor unit 31 of FIG. 8, the photodiode 310A and the photodiode 310B are arranged in the column direction. As described above, when the photodiode 310A (main sensor) for detecting incident light and the photodiode 310B (sub sensor) for detecting background light are arranged so as to be adjacent to each other independently, the background incident on the photodiode 310A. There is a possibility that the irradiation state of the light and the background light incident on the photodiode 310B is different. In addition, there may be a difference in photoelectric conversion characteristics due to manufacturing variations. Furthermore, there may be a difference between the background light component Ib of the photodiode 310A and the background light component Ib of the photodiode 310B due to a difference in temperature distribution.

Therefore, in the second modification, the unit circuits U are arranged in a matrix, and the photodiodes 310A and the photodiodes 310B are alternately arranged in the column direction. As a result, the photodiodes 310A and the photodiodes 310B are dispersed and arranged in a minute region, and the background light irradiation state and temperature distribution can be made uniform. As a result, ambient light can be detected more accurately.
In addition, as shown in FIG. 10, you may use the sensor part 33 which has arrange | positioned the photodiode 310A and the photodiode 310B in zigzag form.

<4. Electronic equipment>
Next, an electronic apparatus to which the electro-optical device 1 according to the above-described embodiments and modifications is applied will be described. FIG. 11 shows the configuration of a mobile personal computer to which the electro-optical device 1 is applied. The personal computer 2000 includes the electro-optical device 1 as a display unit and a main body 2010. The main body 2010 is provided with a power switch 2001 and a keyboard 2002.
FIG. 12 shows a configuration of a mobile phone to which the electro-optical device 1 is applied. A cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and the electro-optical device 1 as a display unit. By operating the scroll button 3002, the screen displayed on the electro-optical device 1 is scrolled.
FIG. 13 shows a configuration of a portable information terminal (PDA: Personal Digital Assistants) to which the electro-optical device 1 is applied. The information portable terminal 4000 includes a plurality of operation buttons 4001, a power switch 4002, and the electro-optical device 1 as a display unit. When the power switch 4002 is operated, various types of information such as an address book and a schedule book are displayed on the electro-optical device 1.
The electronic apparatus to which the electro-optical device 1 is applied includes, in addition to those shown in FIGS. 11 to 13, a digital still camera, a liquid crystal television, a viewfinder type, a monitor direct-view type video tape recorder, a car navigation device, a pager, Examples include electronic notebooks, calculators, word processors, workstations, videophones, POS terminals, and devices equipped with touch panels. The electro-optical device 1 described above can be applied as a display unit of these various electronic devices.

1 is a block diagram illustrating an overall configuration of an electro-optical device 1 according to a first embodiment of the present invention. It is a block diagram which shows the structural example of the optical sensor circuit 300 of the apparatus. It is a timing chart which shows operation | movement of the circuit. It is a block diagram which shows the structural example of the counting circuit 400 of the same apparatus. It is a circuit diagram which shows the structural example of the image display area A of the same apparatus. 3 is a timing chart showing operations of a scanning line driving circuit 100 and a data line driving circuit 200 of the same device. FIG. 6 is a block diagram illustrating an overall configuration of an electro-optical device 1 according to a second embodiment of the invention. It is a circuit diagram which shows the structure of the optical sensor circuit 301 which concerns on a 1st modification. It is a circuit diagram which shows the structure of the optical sensor circuit 301 which concerns on a 2nd modification. It is a circuit diagram which shows the other example of the sensor part used for the circuit. 2 is a perspective view illustrating a configuration of a personal computer as an example of an electronic apparatus to which the electro-optical device 1 is applied. FIG. 2 is a perspective view illustrating a configuration of a mobile phone as an example of an electronic apparatus to which the electro-optical device 1 is applied. FIG. 3 is a perspective view showing a configuration of a portable information terminal as an example of an electronic apparatus to which the electro-optical device 1 is applied. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electro-optical device, 2 ... Scan line, 3 ... Data line, 100 ... Scan line drive circuit, 200 ... Data line drive circuit, 300 ... Optical sensor circuit, 310A ... Photodiode (main sensor), 310B ... Photodiode ( Sub sensor), I1 ... first current, I2 ... second current, Δi ... differential current, U ... unit circuit, 320 ... capacitor, 330 ... switching element, 340 ... NAND circuit, P1 ... pixel circuit, 400 ... counter circuit.

Claims (12)

A light detection circuit in which target light and disturbance light are incident as incident light,
A main sensor that outputs a first current according to the amount of the incident light;
A light-shielding film is provided on a surface on which the target light is incident, and a sub-sensor that outputs a second current corresponding to the amount of the disturbance light,
The main sensor and the sub sensor are connected in series via a connection point, and a differential current between the first current and the second current is extracted from the connection point as an output signal.
An optical detection circuit characterized by that. A light detection circuit in which target light and disturbance light are incident as incident light,
A plurality of unit circuits in which a main sensor and a sub sensor are connected in series via a connection point;
A light shielding film provided on a surface on which the target light of the sub sensor is incident,
The main sensor outputs a first current corresponding to the amount of incident light,
The front sub sensor outputs a second current corresponding to the amount of the disturbance light,
The connection points provided in each of the plurality of unit circuits are connected to each other, and a differential current between the total current of the first current and the total current of the second current is extracted as an output signal.
An optical detection circuit characterized by that. The plurality of unit circuits are arranged along at least one of a row direction and a column direction,
The main sensor and the sub sensor are alternately arranged in the row direction or the column direction.
The photodetection circuit according to claim 2.   4. The photodetection circuit according to claim 1, wherein a photoelectric conversion characteristic of the main sensor is equal to a photoelectric conversion characteristic of the sub sensor. 5.   5. The photodetection circuit according to claim 1, wherein each of the main sensor and the sub sensor includes a photodiode, and the photodiode is reverse-biased. 6. A capacitive element having one end connected to the connection point and the other end connected to a power source;
A switching element provided in parallel with the capacitive element and turned on and off at a predetermined period;
Taking out the voltage signal at the connection point as an output signal,
The photodetection circuit according to claim 1, wherein A voltage frequency conversion circuit for converting the voltage signal into a frequency signal;
Taking out the frequency signal as the output signal instead of the voltage signal;
The photodetection circuit according to claim 6. The voltage frequency conversion circuit includes a logic circuit that calculates a logical product of the voltage signal and a reference signal having a cycle shorter than the ON / OFF cycle of the switching element and outputs a binary signal.
Outputting the binarized signal as the frequency signal;
The photodetection circuit according to claim 7. Counting means for counting the binarized signal and outputting a counting data signal indicating a counting result per unit time;
The photodetection circuit according to claim 8, wherein the count data signal is extracted as the output signal. 10. The photodetection circuit according to claim 1, a plurality of data lines, and a plurality of scanning lines, each provided corresponding to an intersection of the data lines and the scanning data, An electro-optical panel having a plurality of pixel circuits including a liquid crystal element whose transmittance is changed by a typical action;
A light source that emits light from one surface of the electro-optical panel to the other surface;
A light control circuit for adjusting the light quantity of the light source based on the output signal of the light detection circuit;
An electro-optical device comprising: Multiple data lines,
A plurality of scan lines;
A pixel circuit including an electro-optical element, each of which is provided corresponding to an intersection of the data line and the scanning data, and whose optical characteristics are changed by an electrical action;
A control circuit for generating a plurality of control signals;
A drive circuit that generates a drive signal based on the plurality of control signals and outputs the drive signal to at least one of the plurality of data lines and the plurality of scanning lines;
A main sensor that outputs a first current corresponding to the amount of incident light composed of target light and disturbance light, and a second current corresponding to the amount of disturbance light provided on a surface on which the target light enters is provided with a light-shielding film. A sub sensor connected in series with the main sensor via a connection point, a capacitive element having one end connected to the connection point and the other end connected to a power source, and a first parallel provided with the capacitive element. Comprising a photodetector circuit comprising a switching element that is turned on and off based on a signal,
An electro-optical device, wherein the first signal is also used as one of the plurality of control signals.   An electronic apparatus comprising the electro-optical device according to claim 11.

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