JP2010153484A - Light receiving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an influence of light of an infrared region on a light receiving element. <P>SOLUTION: A light receiving circuit has: a first color filter where a first color component of a visible light region and light of the infrared region penetrate; a second color filter which a second color component of the visible light region and light of the infrared region penetrate; a first light receiving element which is formed on a semiconductor substrate and whose light receiving face is covered by the laminated first and second color filters; a second light receiving element which is formed on the semiconductor substrate and whose light receiving face is covered by the first color filter; a current mirror circuit to which a first current flowing to the first light receiving element is inputted in accordance with a received light intensity of input light from an observation space and which outputs a second current corresponding to the first current; and a first current-voltage conversion circuit converting a differential current between a third current flowing to the second light receiving element and the second current in accordance with a received light intensity of input light, into a voltage, and outputting the resulting voltage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light receiving circuit.

  As an example of a light detection device using a light receiving element such as a photodiode, light in the visible light region (hereinafter referred to as ambient light Lop) input from the surrounding observation space as shown in FIG. 6 is received. An illuminance sensor that measures ambient brightness is generally known. In the illuminance sensor shown in FIG. 6, the photocurrent Ig flowing through the light receiving element 12 according to the received light intensity of the ambient light Lop is, for example, a digital signal by the IV (current / voltage) conversion circuit 15 and the signal conversion circuit 2. It is converted into an illuminance signal LX.

  As another example of a photodetection device, a reflective or transmissive proximity sensor that detects the presence or absence of an object by receiving mainly light in the infrared region that is reflected by the object or transmitted without being blocked by the object (Object detection device) is generally known. For example, in the reflective proximity sensor shown in FIG. 7, the photocurrent Iir3 flowing through the light receiving element 13 in accordance with the light receiving intensity of the light reflected by the object 9 (hereinafter referred to as reflected light LRf) is converted into an IV conversion circuit. 16 and the signal conversion circuit 6, for example, are converted into a reception pattern signal Rx, which is a binary signal, and then input to the determination unit 7 and compared with the transmission pattern signal Tx.

  As a color filter that can be used by the light receiving element to selectively receive light in a desired wavelength region in the above-described photodetector, an OCF formed directly on the light receiving surface of the light receiving element on the semiconductor substrate is used. (On-chip Color Filter) is generally known. As an example, in the illuminance sensor shown in FIG. 6, a green region (a wavelength region of about 500 nm or more and less than about 600 nm) is mainly formed on the light receiving surface of a silicon photodiode that is sensitive to light in a wavelength region of about 400 nm to 1100 nm. OCF (hereinafter referred to as a green transmission filter g) that transmits light in the infrared region (wavelength region of about 750 nm or more) is formed, and the relative spectral sensitivity characteristics of the light receiving element 12 having the green transmission filter g are shown in FIG. It becomes like the solid line of 8.

  Patent Document 1 discloses an infrared light transmission filter configured by stacking OCFs that transmit light of different color components. As an example, in the proximity sensor shown in FIG. 7, the green transmission filter g, the red region (wavelength region of about 600 nm or more and less than about 750 nm), and the infrared region are formed on the light receiving surface of the silicon photodiode. The relative spectral sensitivity characteristics of the light receiving element 13 having the green transmission filter g and the red transmission filter r are laminated as shown by the solid line in FIG. Become. The relative spectral sensitivity characteristic of the light receiving element having only the red transmission filter r is as shown by a solid line in FIG. 9. In FIG. 10, the solid line in FIG. 8 is indicated by a short broken line, and the solid line in FIG. It is shown in

In this manner, by forming the OCF on the light receiving surface of the light receiving element, it is possible to selectively receive light in a desired wavelength region in a light detection device such as an illuminance sensor or a proximity sensor.
JP 2006-210701 A

  The photodetection device as described above may be mounted on a portable terminal such as a notebook personal computer or a cellular phone. For example, by mounting the illuminance sensor shown in FIG. 6 on a notebook personal computer, the brightness (luminance) of the liquid crystal display can be adjusted according to the ambient brightness (illuminance). Further, for example, by mounting the proximity sensor shown in FIG. 7 on a mobile phone, it is possible to prevent malfunction caused by touching the face of the touch panel during a call.

  However, when the illuminance sensor and the proximity sensor are mounted on the same portable terminal, reflected light LRf mainly for the infrared region is input to the light receiving element 12 having the green transmission filter g for the illuminance sensor. As shown in FIG. 8, since the light receiving element 12 has high sensitivity to light in the infrared region, the measurement value of the illuminance sensor fluctuates. In particular, in the case of a small portable terminal such as a mobile phone, the influence cannot be avoided by arranging the illuminance sensor and the proximity sensor apart from each other.

  Therefore, the illuminance sensor and the proximity sensor cannot be mounted on a small portable terminal at the same time.

  The main present invention that solves the above-described problems includes a first color filter that transmits the first color component in the visible light region and the light in the infrared region, the second color component in the visible light region, and the infrared region. A second color filter that transmits light, a first light receiving element that is formed on the semiconductor substrate and has a light receiving surface covered by the stacked first and second color filters, and formed on the semiconductor substrate A second light-receiving element whose light-receiving surface is covered by the first color filter, and a first current flowing through the first light-receiving element in accordance with the received light intensity of the input light from the observation space, A current mirror circuit that outputs a second current according to the first current, and a difference between the third current flowing through the second light receiving element according to the received light intensity of the input light and the second current A first power that converts current to voltage and outputs it - a voltage conversion circuit, a receiving circuit, characterized in that it comprises a.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  ADVANTAGE OF THE INVENTION According to this invention, the influence by the light of the infrared region with respect to a light receiving element can be suppressed.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

<First Embodiment>
=== Overall Configuration and Operation of Photodetection Device ===
Hereinafter, with reference to FIG. 1, a schematic configuration of the entire photodetecting device including the light receiving circuit according to the first embodiment of the present invention will be described.

  The light detection apparatus shown in FIG. 1 is configured to include a light receiving circuit 1a and a signal conversion circuit 2, and is an illuminance sensor that receives ambient light Lop and measures ambient brightness. In the present embodiment, the light receiving circuit 1a includes, for example, light receiving elements 11 and 12, a current mirror circuit 14, and an IV conversion circuit 15. In the present embodiment, the ambient light Lop includes visible light region light (hereinafter referred to as a visible light component) that is a desired light component in the illuminance sensor and infrared region light that is a noise component for the illuminance sensor. (Hereinafter, referred to as an infrared noise component).

  The first light receiving element 11 formed on the semiconductor substrate has a light receiving surface covered with the stacked green transmission filter g (first color filter) and red transmission filter r (second color filter), Ambient light Lop is input from the observation space, and photocurrent Iir1 (first current) is output. The second light receiving element 12 formed on the same semiconductor substrate as the light receiving element 11 has a light receiving surface covered with a green transmission filter g, receives ambient light Lop from the observation space, and receives a photocurrent Ig (first 3).

  The photocurrent Iir1 is input from the light receiving element 11 to the current mirror circuit 14, and the outputs of the light receiving element 12 and the current mirror circuit 14 are connected at the node A. The visible light current signal Iop is input from the node A to the first IV conversion circuit 15, and the output signal of the IV conversion circuit 15 is input to the signal conversion circuit 2 as the visible light voltage signal Vop. And the output signal of the signal conversion circuit 2 is output from the said photon detection apparatus as the illumination intensity signal LX.

Next, the operation of the entire photodetecting device in this embodiment will be described.
The light receiving circuit 1a suppresses an infrared noise component in the ambient light Lop, and outputs a visible light voltage signal Vop whose voltage value changes according to the received light intensity of the visible light component. A detailed description of the operation of the light receiving circuit 1a will be described later.

The signal conversion circuit 2 converts the visible light voltage signal Vop into, for example, an illuminance signal LX that is a digital signal. As an example, the signal conversion circuit 2 smoothes the visible light voltage signal Vop as appropriate, converts it to 16-bit serial data using an AD (analog / digital) conversion circuit, etc., and outputs the I ² C as the illuminance signal LX. Output to (Inter-Integrated Circuit) bus.

=== Configuration and Operation of Light-Receiving Circuit ===
In the light receiving circuit 1a of the photodetector shown in FIG. 1, photodiodes are used as the light receiving elements 11 and 12, for example. Hereinafter, as a first embodiment of the present invention, the configuration of the light receiving circuit 1a when the light receiving elements 11 and 12 are photodiodes PD1 and PD2 will be described with reference to FIG.

  The anodes of the photodiodes PD1 and PD2 are both connected to the ground potential.

  In the present embodiment, the current mirror circuit 14 includes transistors 141 and 142 which are PNP bipolar transistors, for example. The collectors of the first transistor 141 and the second transistor 142 are connected to the cathodes of the photodiodes PD1 and PD2, respectively. Note that the connection point between the transistor 142 and the photodiode PD2 corresponds to the node A in FIG. The emitters of the transistors 141 and 142 are both connected to the power supply potential VCC, and the bases are both connected to the collector of the transistor 141.

  In the present embodiment, the IV conversion circuit 15 includes, for example, current sources 151 and 152, transistors 153 and 154 that are NPN bipolar transistors, and a resistor 155. The current source 151 connected to the power supply potential VCC supplies a source current (discharge current) IS1, and the current source 152 connected to the ground potential supplies a sink current (sink current) IS2. In the transistor 153, the current IS1 is supplied to the collector, the emitter is connected to the ground potential, and the base is connected to the node A, thereby forming a grounded emitter circuit. Further, the transistor 154 is supplied with the current IS2 at the emitter, the collector is connected to the power supply potential VCC, and the base is connected to the connection point between the current source 151 and the transistor 153, thereby forming an emitter follower circuit. The output node (node B) of the emitter follower circuit and the input node (node A) of the grounded emitter circuit are connected via a resistor 155.

  Next, the operation of the light receiving circuit 1a in the present embodiment will be described with reference to FIG. In FIG. 2, the current value of each current is a positive value when flowing in the direction of the arrow.

  When the ambient light Lop is input from the observation space, the photodiode PD1 having the green transmission filter g and the red transmission filter r has a light reception intensity mainly in the infrared region as shown by a solid line in FIG. Accordingly, the photocurrent Iir1 flows. Further, since the transistor 142 constitutes a current mirror circuit with the transistor 141, the collector current of the transistor 142 becomes a current Iir2 (second current) corresponding to the photocurrent Iir1 that is the collector current of the transistor 621.

On the other hand, when the ambient light Lop is input from the observation space, the photodiode PD2 having the green transmission filter g mainly receives light in the green region and the infrared region in the visible light region as shown by a solid line in FIG. A photocurrent Ig flows in accordance with the light receiving intensity of the region. Further, since the cathode of the photodiode PD2 and the collector of the transistor 142 are connected at the node A which is an input node of the IV conversion circuit 15, the visible light current signal Iop input to the IV conversion circuit 15 is
Iop = Ig-Iir2
It can be expressed as. Therefore, when the ambient light Lop is not input from the observation space and the potential of the node A when the photocurrents Iir1 and Ig do not flow is the reference level V0, the visible light voltage signal Vop is
Vop = V0 + Iop × R
The voltage value changes in proportion to the difference between the photocurrent Ig and the current Iir2.

  In this way, the photocurrents Iir1 and Ig flow through the photodiodes PD1 and PD2 according to the received light intensity of the ambient light Lop, respectively, the current mirror circuit 14 outputs the current Iir2 according to the photocurrent Iir1, and The IV conversion circuit 15 converts the visible light current signal Iop, which is the difference between the photocurrent Ig and the current Iir2, into a voltage, and outputs a visible light voltage signal Vop. In addition, an infrared noise component mainly appears in the photocurrent Iir1 and the current Iir2, and a visible light component and an infrared noise component mainly due to light in the green region appear in the photocurrent Ig. Therefore, the visible light current signal Iop mainly shows a visible light component due to light in the green region, and the light receiving circuit 1a suppresses the infrared noise component as a whole, and the received light intensity of the desired visible light component in the illuminance sensor is increased. A visible light voltage signal Vop whose voltage value changes accordingly is output.

  The above operation of the light receiving circuit 1a can also be expressed by the relative spectral sensitivity characteristics of the photodiodes PD1 and PD2 and the light receiving circuit 1a as shown in FIG. 3, for example. In FIG. 3, the relative spectral sensitivity characteristic of the photodiode PD1 similar to the solid line in FIG. 10 is indicated by a long broken line, and the relative spectral sensitivity characteristic of the photodiode PD2 similar to the solid line in FIG. The relative spectral sensitivity characteristic of 1a is shown by a solid line.

  In order to equalize the magnitudes of the infrared noise components appearing in the photocurrent Ig and the current Iir2 and more reliably remove the infrared noise components, the size ratio of the transistors 141 and 142 of the current mirror circuit 14 is determined by the photodiode PD1. It is desirable to make it equal to the light receiving area ratio of PD2. Further, since the visible light component mainly appears in the photocurrent Ig and hardly appears in the photocurrent Iir1 and the current Iir2, the visible light component input to the photodiode PD2 mainly appears in the visible light voltage signal Vop. Therefore, in order to improve the light receiving sensitivity of the light receiving circuit 1a for visible light components without increasing the total light receiving area of the photodiodes PD1 and PD2, or to reduce the total light receiving area without reducing the light receiving sensitivity. It is desirable to make the light receiving area of the photodiode PD2 larger than the light receiving area of the photodiode PD1.

<Second Embodiment>
Hereinafter, with reference to FIG. 5, a schematic configuration of the entire photodetecting device including the light receiving circuit according to the second embodiment of the present invention will be described.

  5 includes a light receiving circuit 1b, signal conversion circuits 2 and 6, a pattern generation unit 3, a light emission control circuit 4, a light emitting element 5, and a determination unit 7. An illuminance sensor that receives the light Lop and measures ambient brightness and a reflective proximity sensor that receives the reflected light LRf and detects the presence or absence of the object 9 are simultaneously mounted. In the present embodiment, the ambient light Lop includes only the desired visible light component in the illuminance sensor, and the reflected light LRf in which the transmission light signal LTx is reflected by the object 9 includes the desired light component in the proximity sensor. Only the light in the infrared region (hereinafter referred to as the infrared signal component) is included. Hereinafter, the entire input light from the observation space including the ambient light Lop and the reflected light LRf is represented by the received light signal LRx. It shall be called. In this case, of the received light signal LRx, the ambient light Lop is a noise component for the proximity sensor, and the reflected light LRf is a noise component for the illuminance sensor, that is, the above-described infrared noise component.

  The portion corresponding to the illuminance sensor of the light detection device shown in FIG. 5 (hereinafter referred to as the illuminance sensor unit) includes the light receiving elements 11 and 12 and the current mirror circuit 14 among the signal conversion circuit 2 and the light receiving circuit 1b. And the IV conversion circuit 15, and has the same configuration as the photodetection device (illuminance sensor) of the first embodiment shown in FIG. Detailed description will be omitted.

  A portion corresponding to a proximity sensor (hereinafter referred to as a proximity sensor unit) of the light detection device shown in FIG. 5 includes a pattern generation unit 3, a light emission control circuit 4, a light emitting element 5, a signal conversion circuit 6, and a determination unit. 7 and the IV conversion circuit 16 having the same configuration as the IV conversion circuit 15 in the light reception circuit 1b, for example, and the general proximity sensor shown in FIG. It is the same composition as.

  A transmission pattern signal Tx is input from the pattern generator 3 to the light emission control circuit 4. The transmission current signal ITx output from the light emission control circuit 4 is input to the light emitting element 5, and the light transmission element 5 outputs the transmission optical signal LTx to the observation space.

  The third light receiving element 13 formed on the same semiconductor substrate as the light receiving elements 11 and 12 has a light receiving surface covered with the stacked green transmission filter g and red transmission filter r, and receives the received optical signal LRx from the observation space. Is input and the photocurrent Iir3 (fourth current) is output. Further, the photocurrent Iir3 is input from the light receiving element 13 to the second IV conversion circuit 16, and the output signal of the IV conversion circuit 16 is input to the signal conversion circuit 6 as the infrared light voltage signal Vir.

  The determination unit 7 receives the transmission pattern signal Tx from the pattern generation unit 3 and the reception pattern signal Rx from the signal conversion circuit 6. The output signal of the determination unit 7 is output from the proximity sensor unit as the object detection signal DT. It is output.

Next, the operation of the entire photodetecting device in this embodiment will be described.
The illuminance sensor unit suppresses the infrared noise component included in the reflected light LRf in the received light signal LRx, and the visible light included in the ambient light Lop, as in the light detection device (illuminance sensor) of the first embodiment. The visible light voltage signal Vop whose voltage value changes according to the received light intensity of the component is converted into an illuminance signal LX which is a digital signal, for example, and output.

  The pattern generator 3 generates a transmission pattern signal Tx, which is a binary signal, for example, and supplies it to the light emission control circuit 4. Further, the light emission control circuit 4 supplies the transmission current signal ITx to the light emitting element 5 according to the level of the transmission pattern signal Tx, and changes the light emission intensity of the transmission light signal LTx output from the light emitting element 5 to the observation space. . As an example, when the light emitting element 5 is a light emitting diode, the light emission control circuit 4 increases the light emission intensity of the transmission optical signal LTx by increasing the transmission current signal ITx while the transmission pattern signal Tx is at a high level, While the transmission pattern signal Tx is at a low level, the light emission intensity of the transmission optical signal LTx is lowered by reducing the transmission current signal ITx.

  In this way, the light emission control circuit 4 changes the light emission intensity of the transmission light signal LTx output from the light emitting element 5 to the observation space according to the level of the transmission pattern signal Tx output from the pattern generator 3.

  When the received light signal LRx is input from the observation space, the light receiving element 13 having the green transmission filter g and the red transmission filter r receives mainly infrared light included in the reflected light LRf as shown by the solid line in FIG. The photocurrent Iir3 flows according to the received light intensity of the signal component. The IV conversion circuit 16 converts the photocurrent Iir3 into a voltage and outputs an infrared light voltage signal Vir.

  The signal conversion circuit 6 converts the infrared light voltage signal Vir into a reception pattern signal Rx which is a binary signal, for example. As an example, the signal conversion circuit 6 uses a comparator (comparator) or the like to receive a high-level reception pattern while the received light intensity of the infrared signal component is high and the infrared light voltage signal Vir is higher than a predetermined voltage. The signal Rx is output, and while the received light intensity of the infrared signal component is low and the infrared light voltage signal Vir is lower than a predetermined voltage, the low-level reception pattern signal Rx is output.

  The determination unit 7 compares the transmission pattern signal Tx and the reception pattern signal Rx, and outputs an object detection signal DT according to the comparison result. As an example, the determination unit 7 determines whether or not the levels of the transmission pattern signal Tx and the reception pattern signal Rx match using an XOR circuit (exclusive OR circuit) or the like, and the number of times of matching is determined. When the number of times is equal to or greater than the predetermined number, a high-level object detection signal DT indicating that the object has been detected in the observation space is output. When the number of coincidence is less than the predetermined number, the low-level object is detected. A detection signal DT is output.

  In this way, the determination unit 7 detects an object in the observation space according to the comparison result between the transmission pattern signal Tx output from the pattern generation unit 3 and the reception pattern signal Rx output from the signal conversion circuit 6. An object detection signal DT indicating whether or not it has been output is output.

  As is apparent from the above, the illuminance sensor unit suppresses the infrared noise component included in the reflected light LRf in the received light signal LRx, and the illuminance signal according to the received light intensity of the visible light component included in the ambient light Lop. LX is output. Further, the proximity sensor unit outputs the object detection signal DT based on the reception pattern signal Rx generated mainly according to the received light intensity of the infrared signal component included in the reflected light LRf in the reception light signal LRx, The visible light component included in the ambient light Lop, which is a noise component for the sensor unit, is suppressed by the green transmission filter g and the red transmission filter r of the light receiving element 13. Therefore, the illuminance sensor and the proximity sensor can be simultaneously mounted on a small portable terminal that cannot be arranged separately.

  As described above, in the light receiving circuit shown in FIG. 2, the photodiode PD1 having the first and second color filters and the photodiode PD2 having the first color filter are in accordance with the light receiving intensity of the ambient light Lop. The photocurrents Iir1 and Ig respectively flow, the current mirror circuit 14 outputs a current Iir2 according to the photocurrent Iir1, and the IV conversion circuit 15 converts the difference current between the photocurrent Ig and the current Iir2 into a voltage. By outputting, an infrared noise component can be suppressed in the ambient light Lop.

  Further, by making the size ratio of the transistors 141 and 142 constituting the current mirror circuit 14 equal to the light receiving area ratio of the photodiodes PD1 and PD2, the magnitudes of the infrared noise components appearing in the photocurrent Ig and the current Iir2 are made equal. In addition, the infrared noise component can be more reliably removed.

  Also, by making the light receiving area of the photodiode PD2 larger than the light receiving area of the photodiode PD1, the trade between the total light receiving area of the photodiodes PD1 and PD2 and the light receiving sensitivity of the light receiving circuit for a desired visible light component in the illuminance sensor. The off problem can be solved efficiently.

  Further, as shown in FIG. 5, the photocurrent Iir3 flows through the light receiving element 13 having the first and second color filters mainly according to the received light intensity of the infrared signal component included in the reflected light LRf, and IV The conversion circuit 16 converts the photocurrent Iir3 into a voltage and outputs the voltage, whereby the illuminance sensor and the proximity sensor can be simultaneously mounted on a small portable terminal such as a cellular phone.

  Further, by setting the first and second color filters as the green transmission filter g and the red transmission filter r, respectively, the relative spectral sensitivity characteristics of the light receiving circuit 1a or the light receiving circuit, for example, as shown by the solid line in FIG. The relative spectral sensitivity characteristic of the portion included in the illuminance sensor portion of 1b can be a characteristic suitable for an illuminance sensor having a peak sensitivity wavelength near the center of the visible light region.

  In addition, the said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and equivalents thereof are also included in the present invention.

  In the above embodiment, the configuration and operation of the light receiving circuit in the case where each light receiving element is a photodiode have been described as an example, but the present invention is not limited to this. The light receiving elements 11 to 13 may be other optical sensors that can change the current value of the output signal according to the received light intensity of the input light from the observation space and can form an OCF on the light receiving surface.

  In the above embodiment, the configuration example of the current mirror circuit 14 is shown in FIG. 2, but the present invention is not limited to this. For example, the transistors 141 and 142 of the current mirror circuit 14 may be MOS (Metal-Oxide Semiconductor) transistors.

In the above embodiment, the IV conversion circuit 15 has a configuration in which the output impedance is low by using an emitter follower circuit as an output stage, but the present invention is not limited to this. For example, as shown in FIG. 4, by using an operational amplifier 156 in which the non-inverting input is connected to the reference level V 0, the inverting input is connected to the node A, and the output is connected through the resistor 155. Even when the output impedance of the IV conversion circuit 15 is lowered and the input impedance of the signal conversion circuit 2 is low, the visible light voltage signal Vop can be input. In this case, the visible light voltage signal Vop is
Vop = V0 + Iop × R
It can be expressed as. Also, the IV conversion circuit 16 can have the same configuration.

  In the second embodiment, as an application example of the light receiving circuit of the present invention, the light detection device in which the illuminance sensor and the reflective proximity sensor are simultaneously mounted is shown in FIG. 5, but the present invention is not limited to this. The light receiving circuit 1b can be applied to, for example, a photodetecting device in which an illuminance sensor and a transmissive proximity sensor are simultaneously mounted. In the case of a transmissive proximity sensor, for example, the determination unit 7 indicates that an object has been detected in the observation space when the number of times that the levels of the transmission pattern signal Tx and the reception pattern signal Rx match is less than a predetermined number. The high level object detection signal DT shown is output.

  In the second embodiment, the transmission pattern signal Tx and the reception pattern signal Rx are both binary signals, but the present invention is not limited to this. The determination unit 7 only needs to receive a comparable transmission pattern signal Tx and reception pattern signal Rx. For example, both may be a 3-bit digital signal. In this case, as an example, the signal conversion circuit 6 converts the infrared light voltage signal Vir to a value from 0 to 7 (from binary 000 to 111) using an AD conversion circuit or the like, and the determination unit 7 Then, it is determined whether or not the values of the transmission pattern signal Tx and the reception pattern signal Rx are substantially coincident with each other, and the object detection signal DT is output according to the number of coincidence.

  In the said 2nd Embodiment, although the operation | movement of the light emission control circuit 4 in case the light emitting element 5 is a light emitting diode was demonstrated as an example, it is not limited to this. The light emission control circuit 4 and the light emitting element 5 need to change the light emission intensity of the transmission optical signal LTx in accordance with the modulation speed of the transmission pattern signal Tx. Can be changed.

  In the second embodiment, it is assumed that the ambient light Lop includes only a desired visible light component in the illuminance sensor unit. In the photodetector shown in FIG. 5, the light receiving element 13 in the light receiving circuit 1b. Only the IV conversion circuit 16 and the IV conversion circuit 16 are included in the proximity sensor unit, but the invention is not limited to this. Actually, as in the first embodiment, the ambient light Lop includes the light in the infrared region together with the visible light component, and the light in the infrared region is transmitted through the green transmission filter g and the light receiving element 13. Since it is not suppressed by the red transmission filter r, a desired infrared signal component in the proximity sensor unit may be buried as a DC noise component. Therefore, the proximity sensor unit may be configured to suppress the DC noise component using, for example, a high-pass filter.

It is a block diagram which shows schematic structure of the whole photon detection apparatus provided with the light-receiving circuit in 1st Embodiment of this invention. 1 is a circuit block diagram showing a configuration of a light receiving circuit in a first embodiment of the present invention. It is a schematic diagram which shows the relationship between the wavelength of the input light of the light receiving circuit in 1st Embodiment of this invention, and relative spectral sensitivity. It is a circuit block diagram which shows the other structural example of the light receiving circuit of this invention. It is a block diagram which shows schematic structure of the whole photon detection apparatus provided with the light-receiving circuit in 2nd Embodiment of this invention. It is a block diagram which shows an example of a structure of a general illumination sensor. It is a block diagram which shows an example of a structure of a general proximity sensor (object detection apparatus). It is a schematic diagram which shows the relationship between the wavelength of the input light of a light receiving element which has a green transmission filter, and relative spectral sensitivity. It is a schematic diagram which shows the relationship between the wavelength of the input light of a light receiving element which has a red transmissive filter, and relative spectral sensitivity. It is a schematic diagram which shows the relationship between the wavelength of the input light of a light receiving element which has a green transmission filter and a red transmission filter, and relative spectral sensitivity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b, 1c, 1d Light reception circuit 2, 6 Signal conversion circuit 3 Pattern generation part 4 Light emission control circuit 5 Light emission element 7 Judgment part 9 Object 11, 12, 13 Light reception element 14 Current mirror circuit 15, 16 IV (current and voltage) ) Conversion circuit PD1, PD2 Photodiode 141, 142 Transistor 151, 152 Current source 153, 154 Transistor 155 Resistor 156 Operational amplifier (operational amplifier)

Claims (5)

A first color filter that transmits the first color component in the visible light region and the light in the infrared region;
A second color filter that transmits the second color component in the visible light region and the light in the infrared region;
A first light receiving element formed on a semiconductor substrate and having a light receiving surface covered with the first and second color filters stacked;
A second light receiving element formed on the semiconductor substrate and having a light receiving surface covered by the first color filter;
A current mirror circuit that receives a first current flowing through the first light receiving element according to the received light intensity of the input light from the observation space, and outputs a second current according to the first current;
A first current / voltage conversion circuit that converts a difference current between the third current flowing through the second light receiving element and the second current into a voltage according to the received light intensity of the input light, and outputs the voltage;
A light receiving circuit comprising: The current mirror circuit is:
A diode-connected first transistor through which the first current flows;
A second transistor having a control electrode connected to the control electrode of the first transistor and through which the second current flows;
Including
2. The light receiving circuit according to claim 1, wherein a size ratio of the first and second transistors is equal to a light receiving area ratio of the first and second light receiving elements.   The light receiving circuit according to claim 2, wherein a light receiving area of the second light receiving element is larger than a light receiving area of the first light receiving element. A third light receiving element formed on the semiconductor substrate, the light receiving surface of which is covered with the stacked first and second color filters;
A second current / voltage conversion circuit that converts a fourth current flowing through the third light receiving element into a voltage according to the received light intensity of the input light and outputs the voltage;
The light receiving circuit according to claim 1, further comprising: The first color filter transmits light in a green region and an infrared region,
5. The light receiving circuit according to claim 1, wherein the second color filter transmits light in a red region and an infrared region.

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