Light-receiving device, optical sensor, and distance measurement device

Abstract

This light-receiving device comprises: a plurality of photodiodes; a plurality of current-voltage conversion amplification circuits respectively connected to the plurality of photodiodes; a selection circuit that selects and outputs one of the output signals of the plurality of current-voltage conversion amplification circuits; and a control circuit that outputs a plurality of first control signals for controlling the on-state or the off-state of each of the plurality of current-voltage conversion amplification circuits, and a second control signal for controlling the selection circuit. The control circuit outputs the first control signal to one current-voltage conversion amplifier circuit, outputs the second control signal after a predetermined time after the one current-voltage conversion amplifier circuit has turned on, and outputs the output signal of the one current-voltage conversion amplifier circuit to the selection circuit.

Description

Light receiving device, optical sensor and distance measuring device

[0001] The present invention relates to a light receiving device, an optical sensor, and a distance measuring device.

[0002] Distance measuring devices that measure the distance to an object using a time-of-flight (TOF) method are known. Distance measuring devices that use the TOF method can measure the distance to an object by detecting the time from when a measurement light is irradiated onto the object to when the reflected light of the measurement light is received.

[0003] For example, the laser distance measurement device disclosed in Patent Document 1 includes a MEMS mirror that deflects output light from a light source, a photodetector that detects reflected light from the output light reflected by an object, a photodetector circuit board that amplifies a signal based on the reflected light detected by the detector, a control circuit board that measures the distance to the object based on the signal output from the photodetector circuit board, and a rotation mechanism that rotates an optical system including the light source, the MEMS mirror, and the photodetector.

[0004] The photodetector has a plurality of detecting elements, the light receiving circuit board has a plurality of transimpedance amplifiers, a switching circuit, and an amplifier circuit, and the control circuit board has a control circuit, a TDC circuit, and a signal processing circuit.

[0005] The multiple transimpedance amplifiers on the light receiving circuit board are connected to the multiple detection elements of the photodetector, respectively, and convert the currents generated by the detection elements into voltages and output the resulting electrical signals to the switching circuit. The switching circuit outputs electrical signals based on the currents generated by the detection elements selected by the control circuit on the control circuit board to the amplifier circuit via the transimpedance amplifiers. The amplifier circuit amplifies the electrical signals output from the switching circuit and outputs them to the TDC circuit on the control circuit board. The TDC circuit on the control circuit board outputs signals indicating the time difference between the pulse signal input from the control circuit and the electrical signal input from the amplifier circuit to the signal processing circuit. The signal processing circuit calculates the distance to the object from the time corresponding to the signal input from the TDC circuit and the speed of light.

[0006] In the laser distance measurement device of Patent Document 1, with the above-described configuration, three-dimensional distance measurement can be performed by rotating the optical system using a rotation mechanism and scanning the output light two-dimensionally using a MEMS mirror.

[0007] Furthermore, in the laser distance measurement device of Patent Document 1, as described above, the detection elements that output the electrical signals can be switched by a switching circuit. In this case, a common amplifier circuit can be used to amplify the electrical signals based on the currents generated by the multiple detection elements. Patent Document 1 describes that this configuration can further simplify the circuitry compared to a configuration in which an amplifier circuit is provided for each detection element.

[0008] Japanese Patent Application Laid-Open No. 2018-128432

[0009] In the laser distance measurement device of Patent Document 1, the switching circuit is connected to multiple detection elements via multiple transimpedance amplifiers. In the configuration disclosed in Patent Document 1, it is thought that the detection element that outputs the electrical signal is switched by keeping all the transimpedance amplifiers on and connecting one of the transimpedance amplifiers to the amplification circuit.

[0010] However, turning all the transimpedance amplifiers on simultaneously as described above increases the power consumption of the device. Therefore, in order to reduce power consumption, the inventors attempted to provide switching circuits for each of the multiple transimpedance amplifiers and control the on / off of the power supply or output of each transimpedance amplifier.

[0011] However, when the power supply or output of a transimpedance amplifier is switched from off to on, a glitch (noise voltage) occurs due to an inrush current, and therefore, when multiple transimpedance amplifiers are switched on and off in sequence, the detection accuracy of reflected light may be reduced due to the influence of the glitch.

[0012] Therefore, an example of an object of the present invention is to provide a light receiving device, an optical sensor, and a distance measuring device that can reduce power consumption while preventing a decrease in detection accuracy.

[0013] (1) In order to achieve the above object, a light receiving device according to one aspect of the present invention includes a plurality of photodiodes, a plurality of current-voltage conversion amplifier circuits respectively connected to the plurality of photodiodes, a selection circuit that selects and outputs one of the output signals of the plurality of current-voltage conversion amplifier circuits, and a control circuit that outputs a plurality of first control signals that control the on / off state of each of the plurality of current-voltage conversion amplifier circuits and a second control signal that controls the selection circuit, wherein the control circuit outputs the first control signal to one of the current-voltage conversion amplifier circuits, and, after a predetermined time has elapsed since the one of the current-voltage conversion amplifier circuits was turned on, outputs the second control signal to cause the selection circuit to output the output signal of the one of the current-voltage conversion amplifier circuits.

[0014] According to the light receiving device, the on / off state of each of the plurality of current-voltage conversion amplifier circuits can be switched by the plurality of first control signals output from the control circuit. This allows the on / off state of each of the plurality of current-voltage conversion amplifier circuits to be switched, for example, depending on the timing at which each of the plurality of photodiodes receives reflected light. In this case, the power consumption of the light receiving device can be reduced compared to when all of the current-voltage conversion amplifier circuits are kept on and a selection circuit is used to select and output one of the output signals of the current-voltage conversion amplifier circuits.

[0015] Furthermore, after a predetermined time has elapsed since any current-voltage conversion amplifier circuit was switched on, the output signal of that current-voltage conversion amplifier circuit is output from the selection circuit. In this case, even if a glitch occurs in each current-voltage conversion amplifier circuit, the glitch can be prevented from being output from the selection circuit as part of the output signal of the current-voltage conversion amplifier circuit. This allows for accurate detection of the reflected light received by the multiple photodiodes.

[0016] (2) In the above-described light receiving device, the predetermined time may be set to be longer than the length of time from when the current-voltage conversion amplifier circuit is switched from an off state to an on state to when a glitch occurring in the current-voltage conversion amplifier circuit converges.

[0017] In this case, even if a glitch occurs in each current-voltage conversion amplifier circuit, it is possible to reliably prevent the glitch from being output from the selection circuit as part of the output signal of the current-voltage conversion amplifier circuit.

[0018] (3) In the above-described light receiving device, while the selection circuit is outputting the output signal of one current-voltage conversion amplifier circuit, the control circuit may output a first control signal to the other current-voltage conversion amplifier circuit to turn on the other current-voltage conversion amplifier circuit, and after a predetermined time has passed since the other current-voltage conversion amplifier circuit turned on, the control circuit may output a second control signal to cause the selection circuit to output the output signal of the other current-voltage conversion amplifier circuit.

[0019] In this case, for example, if the photodiodes PD1 and PD2 receive reflected light in this order, even if the current-voltage conversion amplifier circuit connected to the photodiode PD2 is turned on between the time when the photodiode PD1 receives the reflected light and the time when the photodiode PD2 receives the reflected light, it is possible to prevent a glitch from the current-voltage conversion amplifier circuit from being output from the selection circuit. Therefore, it is possible to quickly switch the on and off states of the multiple current-voltage conversion amplifier circuits and prevent a glitch from each current-voltage conversion amplifier circuit from being output from the selection circuit. This improves the resolution of the light receiving device and the accuracy of detecting reflected light.

[0020] (4) In the above-described light receiving device, when the signal output by the selection circuit is switched from the output signal of one current-voltage conversion amplifier circuit to the output signal of another current-voltage conversion amplifier circuit based on the second control signal, the control circuit may output a first control signal to the one current-voltage conversion amplifier circuit to turn off the one current-voltage conversion amplifier circuit. In this case, the power consumption of the light receiving device can be further reduced.

[0021] (5) The light receiving device may further include an output processing unit that controls whether to enable or disable output of output signals from the plurality of current-voltage conversion amplifier circuits to the selection circuit, wherein the control circuit further outputs a third control signal that controls the output processing unit, and the output processing unit outputs an output signal of at least one of the plurality of current-voltage conversion amplifier circuits to the selection circuit based on the third control signal. In this case, the output signal of the current-voltage conversion amplifier circuit can be appropriately output to the selection circuit in accordance with the timing at which each of the plurality of photodiodes receives reflected light.

[0022] (6) In the above-described photodetector, the multiple current-voltage conversion amplifier circuits may be divided into multiple groups, each group including two or more current-voltage conversion amplifier circuits, the output processing unit may include output processing circuits in the same number as the multiple groups, one output processing circuit may be provided for each of the multiple groups, the output processing circuit may select one of the output signals of the two or more current-voltage conversion amplifier circuits included in the group and output the selected signal to the selection circuit, and the selection circuit may select one of the output signals output from the multiple output processing circuits based on a second control signal and output the selected signal. In this case, processing by the output processing circuit is easier than when a single common output processing circuit controls signal output from the multiple current-voltage conversion amplifier circuits to the selection circuit. This simplifies the design of the photodetector.

[0023] (7) In the above-described light receiving device, the predetermined time may be set longer than the time from when the current-voltage conversion amplifier circuit is switched from an off state to an on state until a glitch occurring in the current-voltage conversion amplifier circuit converges, or may be set longer than the time from when the output signal to the selection circuit becomes valid until a glitch occurring in the output processing unit converges. In this case, even if a glitch occurs in each current-voltage conversion amplifier circuit or the output processing unit, the glitch can be prevented from being output from the selection circuit as part of the output signal of the current-voltage conversion amplifier circuit. This allows for accurate detection of reflected light received by the photodiode.

[0024] (8) In the above-described light-receiving device, the multiple photodiodes may be arranged in a row, and two current-voltage conversion amplifier circuits connected to any two adjacent photodiodes may belong to different groups. In this case, the output signals of the two current-voltage conversion amplifier circuits may be output to the selection circuit in a time-overlapping manner by different output processing circuits. For example, while the output signal of one current-voltage conversion amplifier circuit is being output to the selection circuit, the output signal of the other current-voltage conversion amplifier circuit may start being output to the selection circuit. This improves the switching speed of the signals output from the selection circuit.

[0025] (9) An optical sensor according to one aspect of the present invention includes the above-described light receiving device and a light projecting device that projects measurement light into a measurement target space in synchronization with a second control signal from a control circuit. This optical sensor can reduce power consumption while preventing a decrease in detection accuracy.

[0026] (10) The optical sensor may further include a light scanning unit that scans the measurement light in a predetermined direction in the measurement target space. In this case, the measurement light can be scanned in a desired direction.

[0027] (11) A distance measuring device according to one aspect of the present invention includes the optical sensor described above and a distance measuring unit that calculates the distance to an object based on the measurement light and the light reflected from the object in the measurement target space. This distance measuring device can reduce power consumption while preventing a decrease in detection accuracy.

[0028] According to the present invention, a light receiving device, an optical sensor, and a distance measuring device are provided that can reduce power consumption while preventing a decrease in detection accuracy.

[0029] FIG. 1 is a block diagram showing a schematic configuration of a distance measuring device according to an embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of a light receiving device. FIG. 3 is a diagram showing a more specific configuration of the light receiving device. FIG. 4 is a diagram showing the waveform of a control signal output from a control circuit. FIG. 5 is a diagram for explaining the flow of an output signal from a transimpedance amplifier to a selection circuit. FIG. 6 is a diagram for explaining the flow of an output signal from a transimpedance amplifier to a selection circuit. FIG. 7 is a diagram for explaining the flow of an output signal from a transimpedance amplifier to a selection circuit. FIG. 8 is a diagram for explaining the flow of an output signal from a transimpedance amplifier to a selection circuit. FIG. 9 is a diagram for explaining the flow of an output signal from a transimpedance amplifier to a selection circuit.

[0030] Hereinafter, a light receiving device, an optical sensor, and a distance measuring device according to an embodiment of the present invention will be described with reference to the drawings.

[0031] (Configuration of Distance Measuring Device) Fig. 1 is a block diagram showing the schematic configuration of a distance measuring device according to one embodiment of the present invention. The distance measuring device 100 according to this embodiment projects measurement light into a space to be measured, receives light reflected by an object (hereinafter referred to as the target object) in the space to be measured, and calculates the distance to the target object based on the timing at which the reflected light is received. As shown in Fig. 1, in this embodiment, the distance measuring device 100 includes an optical sensor 10, a power supply unit 12, a drive mechanism 14, and a distance measuring unit 24. The optical sensor 10 includes a light projecting device 16, a light deflecting unit 18, a light scanning unit 20, and a light receiving device 22.

[0032] The light projecting device 16 includes, for example, a light source and a light source driving unit (not shown). The light source is, for example, a semiconductor laser or an LED. The light source driving unit is a circuit that drives the light source to emit light. In this embodiment, the light projecting device 16 is driven by a second control signal SG output from a control circuit 36 ​​(described later) of the optical scanning unit 20. ｂ The measurement light is pulsed light having a pulse width of, for example, several hundred picoseconds to several tens of nanoseconds.

[0033] The optical deflection unit 18 includes a reflecting unit such as a mirror and a focusing unit such as a light-receiving lens. The reflecting unit of the optical deflection unit 18 deflects the measurement light emitted from the light-projecting device 16 or the light reflected from the measurement target space in a predetermined direction. The focusing unit of the optical deflection unit 18 focuses the reflected light toward the light-receiving device 22. The optical scanning unit 20 includes a swing element that swings the reflecting unit of the optical deflection unit 18. The optical scanning unit 20 swings the reflecting unit of the optical deflection unit 18 to scan the measurement light deflected by the optical deflection unit 18 in a predetermined direction (e.g., vertical or horizontal) in the measurement target space. Note that the optical sensor 10 does not necessarily have to include the optical deflection unit 18. In this case, the optical scanning unit 20 only needs to be configured to scan the measurement light emitted from the light-projecting device 16 in a predetermined direction in the measurement target space.

[0034] FIG. 2 is a diagram showing a schematic configuration of the light-receiving device 22. As shown in FIG. 2, the light-receiving device 22 includes a light-detecting unit 30, a converting unit 32, a selection circuit 34, and a control circuit 36. The light-detecting unit 30 includes multiple photodiodes PD1 to PD16. In this embodiment, the photodiodes PD1 to PD16 are arranged in a line. Reflected light (pulsed light) of the measurement light scanned in a predetermined direction by the light scanning unit 20 is incident on the photodiodes PD1 to PD16 in sequence. As a result, the reflected light (pulsed light) is detected sequentially by the photodiodes PD1 to PD16. The light-detecting unit 30 may be, for example, a known APD array. Note that the reflected light being incident sequentially on the photodiodes PD1 to PD16 includes not only the case where the reflected light is incident on the photodiodes PD1 to PD16 once in sequence, but also the case where the reflected light is incident on the photodiodes PD1 to PD16 multiple times in sequence. For example, the reflected light may be incident twice on each of the photodiodes PD1 to PD16 in turn.

[0035] The conversion unit 32 includes a plurality of transimpedance amplifiers TIA1 to TIA16. The transimpedance amplifiers TIA1 to TIA16 are connected to the photodiodes PD1 to PD16, respectively. The transimpedance amplifiers TIA1 to TIA16 convert the output currents of the photodiodes PD1 to PD16 into voltages and output the voltages as output signals to the selection circuit 34. In this embodiment, the transimpedance amplifiers TIA1 to TIA16 each correspond to a current-voltage conversion amplifier circuit.

[0036] The selection circuit 34 receives a second control signal SG ｂ , one of the output signals of the transimpedance amplifiers TIA1 to TIA16 is selected based on the signal, and output to the distance measuring unit 24 (see FIG. 1). Although not shown, the light receiving device 22 may further include an amplifier circuit that amplifies the output signal output from the selection circuit 34 and outputs the amplified signal to the distance measuring unit 24.

[0037] The control circuit 36 ​​outputs a first control signal SG that controls the on / off state of each of the transimpedance amplifiers TIA1 to TIA16. ａ and a second control signal SG that controls the selection circuit 34. ｂ In this embodiment, the control circuit 36 ​​outputs the first control signal SG ａ The on state of the transimpedance amplifier means that power is supplied to the transimpedance amplifier and a signal is output, and the off state means that power is not supplied to the transimpedance amplifier or a signal is not output.

[0038] In this embodiment, the control circuit 36 ​​controls the plurality of first control signals SG to sequentially switch the plurality of transimpedance amplifiers TIA1 to TIA16 from an off state to an on state, and sequentially return the plurality of transimpedance amplifiers TIA1 to TIA16 to an off state. ａIn this embodiment, the control circuit 36 ​​outputs the second control signal SG ｂ Although not shown, the control circuit 36 ​​outputs a control signal to the light projecting device 16 to cause the light projecting device 16 to project the measurement light. In this embodiment, the control circuit 36 ​​outputs the second control signal SG ｂ In synchronization with the switching of the output signal output from the selection circuit 34, the control circuit 36 ​​outputs a control signal to the light projector 16 to project the measurement light. In other words, the control circuit 36 ​​causes the light projector 16 to project the measurement light in synchronization with the switching of the output signal output from the selection circuit 34. When the reflected light is made to be incident on the photodiodes PD1 to PD16 in turn multiple times, the control circuit 36 ​​outputs a control signal to the light projector 16 so that the measurement light is projected multiple times each time the output signal output from the selection circuit 34 is switched.

[0039] In this embodiment, the control circuit 36 ​​outputs a first control signal SG ａ After a predetermined time has elapsed since the transimpedance amplifier was turned on, the second control signal SG ｂ , causing the selection circuit 34 to output the output signal of that transimpedance amplifier. Therefore, even if a glitch occurs in each transimpedance amplifier as it changes from an off state to an on state, it is possible to prevent the glitch from being output from the selection circuit 34 as part of the output signal of the transimpedance amplifier.

[0040] In this embodiment, the control circuit 36 ​​outputs the first control signal SG to the other transimpedance amplifiers while the selection circuit 34 outputs the output signal of one transimpedance amplifier. ａ to turn on the other transimpedance amplifier, and after a predetermined time has elapsed since the other transimpedance amplifier was turned on, the second control signal SG ｂto cause the selection circuit 34 to output the output signal of the other transimpedance amplifier. As a result, for example, when the photodiodes PD1 and PD2 receive reflected light in this order, even if the transimpedance amplifier TIA2 connected to the photodiode PD2 is turned on between the time when the photodiode PD1 receives the reflected light and the time when the photodiode PD2 receives the reflected light, it is possible to prevent a glitch of the transimpedance amplifier TIA2 from being output from the selection circuit 34. Therefore, while the on and off states of the transimpedance amplifiers TIA1 to TIA16 are switched at high speed, it is possible to prevent a glitch of the transimpedance amplifiers TIA1 to TIA16 from being output from the selection circuit 34. In this case, the high-speed switching of the on and off states of the transimpedance amplifiers TIA1 to TIA16 improves the resolution of the light receiving device 22, while preventing the selection circuit 34 from outputting a glitch, thereby improving the detection accuracy of the reflected light.

[0041] The predetermined time is set to be longer than the time from when the transimpedance amplifier is switched from an off state to an on state to when a glitch occurring in the transimpedance amplifier converges. In this case, even if a glitch occurs in each transimpedance amplifier, the glitch can be reliably prevented from being output from the selection circuit 34 as part of the output signal of the transimpedance amplifier.

[0042] 1, the distance measuring unit 24 of the distance measuring device 100 calculates the distance to the object based on the measurement light and the reflected light. In this embodiment, the distance measuring unit 24 includes, for example, a TDC circuit, and detects the time difference between the projection time of the measurement light and the reception time of the reflected light based on the output signals of the transimpedance amplifiers TIA1 to TIA16 output from the light receiving device 22. Furthermore, the distance measuring unit 24 calculates the distance to the object from the detected time difference and the speed of light. Note that the components of the optical sensor 10 other than the light receiving device 22 can utilize the configuration of an optical sensor of a known distance measuring device.

[0043] The power supply unit 12 outputs a predetermined power supply voltage to the optical sensor 10, the drive mechanism 14, and the distance measurement unit 24 in order to operate the optical sensor 10, the drive mechanism 14, and the distance measurement unit 24. The power supply unit 12 may also have an input terminal to which power is supplied from outside the distance measurement device 100.

[0044] The drive mechanism 14 includes, for example, a motor and rotates the light projecting device 16, the light deflection unit 18, the light scanning unit 20, and the light receiving device 22 (hereinafter abbreviated as the light projecting device 16, etc.). In this embodiment, the drive mechanism 14 rotates the light projecting device 16, etc. around a rotation axis parallel to the scanning direction of the measurement light. For example, when the light scanning unit 20 scans the measurement light in the vertical direction, the drive mechanism 14 rotates the light projecting device 16, etc. around a rotation axis extending in the vertical direction. By rotating the light projecting device 16, etc. in this manner using the drive mechanism 14, three-dimensional distance measurement can be performed. Note that the configuration of the drive mechanism 14 can be the same as that of a known distance measuring device capable of three-dimensional distance measurement, and therefore a detailed description of the drive mechanism 14 will be omitted.

[0045] (Effects of this embodiment) In this embodiment, the plurality of first control signals SG output from the control circuit 36 ａ This allows the on and off states of each of the multiple transimpedance amplifiers TIA1 to TIA16 to be switched between. For example, the on and off states of each of the transimpedance amplifiers TIA1 to TIA16 can be switched between depending on the timing at which each of the photodiodes PD1 to PD16 receives reflected light. In this case, the power consumption of the light receiving device 22 (range measuring device 100) can be reduced compared to when all of the transimpedance amplifiers TIA1 to TIA16 are kept on and the selection circuit 34 selects and outputs one of the output signals of the transimpedance amplifiers TIA1 to TIA16.

[0046] Furthermore, in this embodiment, after a predetermined time has elapsed since any transimpedance amplifier is switched on, the output signal of that transimpedance amplifier is output from the selection circuit 34. In this case, even if a glitch occurs in each transimpedance amplifier, the glitch can be prevented from being output as part of the output signal of the transimpedance amplifier from the selection circuit 34. This allows the reception of reflected light by the photodiodes PD1 to PD16 to be detected with high accuracy.

[0047] As described above, the light receiving device 22 according to this embodiment can reduce power consumption while preventing a decrease in the detection accuracy of reflected light.

[0048] (Specific example of light receiving device) Fig. 3 is a diagram showing a more specific configuration of a light receiving device. Note that, in the configuration of the light receiving device 22a shown in Fig. 3, the configuration that is different from the above-mentioned light receiving device 22 will be mainly described below, and a description of the configuration that is common to the above-mentioned light receiving device 22 will be omitted.

[0049] As shown in FIG. 3, the light receiving device 22a includes an output processing unit 38. The output processing unit 38 includes multiple output processing circuits 381 to 384. The multiple transimpedance amplifiers TIA1 to TIA16 of the conversion unit 32 are divided into multiple groups, each including two or more transimpedance amplifiers. In this embodiment, the transimpedance amplifiers TIA1 to TIA16 are classified into group G1 consisting of transimpedance amplifiers TIA1, TIA3, TIA5, and TIA7; group G2 consisting of transimpedance amplifiers TIA2, TIA4, TIA6, and TIA8; group G3 consisting of transimpedance amplifiers TIA9, TIA11, TIA13, and TIA15; and group G4 consisting of transimpedance amplifiers TIA10, TIA12, TIA14, and TIA16. In this embodiment, groups G1 to G4 are provided with output processing circuits 381 to 384, respectively.

[0050] In this embodiment, the transimpedance amplifiers TIA1 to TIA16 are grouped so that two transimpedance amplifiers connected to any two adjacent photodiodes in the photodetector unit 30 belong to different groups. For example, the transimpedance amplifiers TIA1 and TIA2 connected to photodiodes PD1 and PD2 adjacent to each other in the photodetector unit 30 belong to different groups G1 and G2.

[0051] The selection circuit 34 has a plurality of input terminals IT1 to IT4, which are connected to output processing circuits 381 to 384, respectively.

[0052] The control circuit 36 ​​outputs a plurality of first control signals SG ａｎ (n=1 to 16) to the conversion unit 32, and outputs a plurality of second control signals SG ｂｎ (n=1 to 4) to the selection circuit 34, and outputs a plurality of third control signals SG ｃｎ (n=1 to 4) to the output processing unit 38. Note that the first control signal SG ａ１ ~SG ａ１６ correspond to the transimpedance amplifiers TIA1 to TIA16, respectively. ｂ１ ~SG ｂ４ correspond to the input terminals IT1 to IT4, respectively. ｃ１ ~SG ｃ４ correspond to the output processing circuits 381 to 384, respectively.

[0053] In this embodiment, the first control signal SG output from the control circuit 36 ​​to the conversion unit 32 ａｎ In synchronization with the rising of the first control signal SG to a high level, the corresponding transimpedance amplifiers TIA1 to TIA16 are turned on. ａｎ In this embodiment, the first control signal SG ａｎ is generated.

[0054] The second control signal SG output from the control circuit 36 ​​to the selection circuit 34 ｂｎ In this embodiment, the selection circuit 34 outputs a signal input to one of the input terminals IT1 to IT4 based on the second control signal SG ｂｎ is at a high level, the signal input to the corresponding input terminal IT1 to IT4 is output. In this embodiment, the second control signal SG ｂｎ In other words, the second control signal SG ｂｎ In this embodiment, the light projecting device 16 projects measurement light in synchronization with switching of the selected input terminals IT1 to IT4.

[0055] Also, the third control signal SG output from the control circuit 36 ​​to the output processing unit 38 ｃｎ Based on the third control signal SG ｃｎ is at a high level, the output signal of the transimpedance amplifier is output to the selection circuit 34.

[0056] The operation of the light receiving device 22a will be described below using an example. The following description will be given of a case where the photodiode that receives reflected light is switched sequentially among the photodiodes PD1 to PD3. FIG. 4 is a diagram showing the waveform of a control signal output from the control circuit 36. FIG. 4 also shows glitches output from the output processing circuits 381 and 382 to the selection circuit 34. FIGS. 5 to 9 are diagrams for explaining the flow of output signals from the transimpedance amplifiers TIA1 to TIA3 to the selection circuit 34.

[0057] Referring to FIG. 4, when the photodiode PD1 receives reflected light, the first control signal SG ａ１ , second control signal SG ｂ１ , and the third control signal SGｃ１ are at a high level. In this case, as shown in FIG. 5, an output signal of the transimpedance amplifier TIA1 based on the output current of the photodiode PD1 is output by the output processing circuit 381 to the input terminal IT1 of the selection circuit 34. The selection circuit 34 outputs the output signal of the transimpedance amplifier TIA1 input to the input terminal IT1 to the distance measurement unit 24 (see FIG. 1). In this example, when the photodiodes PD1 to PD3 receive reflected light, the transimpedance amplifiers TIA2, TIA9, and TIA10 are in an on state.

[0058] Referring to FIG. 4, before the reflected light is received by the photodiode PD2, the third control signal SG ｃ２ rises. This enables signal output from the output processing circuit 382 to the selection circuit 34. As a result, as shown in FIG. 6, not only the output signal of the transimpedance amplifier TIA1 but also the output signal of the transimpedance amplifier TIA2 can be output to the selection circuit 34. However, because the selection circuit 34 selects the input terminal IT1, the output signal from the output processing circuit 382 is not output from the selection circuit 34. Therefore, as shown in FIG. 4, even if a glitch occurs in the transimpedance amplifier TIA2 or the output processing circuit 382 when the signal output from the output processing circuit 382 to the selection circuit 34 becomes enabled, it is possible to prevent the glitch from being output from the selection circuit 34.

[0059] Third control signal SG ｃ２ After a predetermined time has elapsed since the rise of the second control signal SG, the photodiode that receives the reflected light is switched to the photodiode PD2. ｂ１ and the third control signal SG ｃ１ falls, and the second control signal SG ｂ２7, the signal output from the output processing circuit 381 to the selection circuit 34 is disabled, while the output signal of the transimpedance amplifier TIA2 based on the output current of the photodiode PD2 is output by the output processing circuit 382 to the input terminal IT2 of the selection circuit 34. The selection circuit 34 outputs the output signal of the transimpedance amplifier TIA2 input to the input terminal IT2 to the distance measurement unit 24 (see FIG. 1).

[0060] 4, the length of time from when the signal output of output processing circuit 382 becomes valid to when input terminal IT2 is selected by selection circuit 34 is preferably set longer than the length of time from when the signal output of output processing circuit 382 becomes valid to when a glitch occurring in output processing circuit 382 converges. This makes it possible to reliably prevent a glitch occurring in transimpedance amplifier TIA2 or output processing circuit 382 from being output from selection circuit 34.

[0061] Referring to FIG. 4, before the reflected light is received by the photodiode PD3, the first control signal SG ａ３ and the third control signal SG ｃ１ Also, the first control signal SG ａ３ and the third control signal SG ｃ１ In synchronization with the rising edge of the first control signal SG ａ１falls. This switches the on / off states of the transimpedance amplifiers TIA1 and TIA3, and enables signal output from the output processing circuit 381 to the selection circuit 34. As a result, as shown in FIG. 8, not only the output signal of the transimpedance amplifier TIA2 but also the output signal of the transimpedance amplifier TIA3 can be output to the selection circuit 34. However, because the selection circuit 34 selects the input terminal IT2, the output signal from the output processing circuit 381 is not output from the selection circuit 34. Therefore, as shown in FIG. 4, even if a glitch occurs in the transimpedance amplifier TIA3 or the output processing circuit 381 when the transimpedance amplifier TIA3 is turned on and the signal output from the output processing circuit 381 to the selection circuit 34 is enabled, the glitch can be prevented from being output from the selection circuit 34.

[0062] First control signal SG ａ３ and the third control signal SG ｃ１ After a predetermined time has elapsed since the rise of the second control signal SG, the photodiode that receives the reflected light is switched to the photodiode PD3. ｂ２ and the third control signal SG ｃ２ falls, and the second control signal SG ｂ１ 9, the signal output from the output processing circuit 382 to the selection circuit 34 is disabled, while the output signal of the transimpedance amplifier TIA3 based on the output current of the photodiode PD3 is output by the output processing circuit 381 to the input terminal IT1 of the selection circuit 34. The selection circuit 34 outputs the output signal of the transimpedance amplifier TIA3 input to the input terminal IT1 to the distance measurement unit 24 (see FIG. 1).

[0063] 4, the length of time from when the transimpedance amplifier TIA3 is turned on or when the signal output of the output processing circuit 381 is enabled to when the input terminal IT1 is selected by the selection circuit 34 is preferably set longer than the length of time from when the transimpedance amplifier TIA3 is turned on or when the signal output of the output processing circuit 381 is enabled to when a glitch occurring in the transimpedance amplifier TIA3 or the output processing circuit 381 converges. This makes it possible to reliably prevent a glitch occurring in the transimpedance amplifier TIA3 or the output processing circuit 381 from being output from the selection circuit 34.

[0064] In the light receiving device 22a according to this embodiment, the output processing unit 38 controls whether to enable or disable the output of the output signals from the plurality of transimpedance amplifiers TIA1 to TIA16 to the selection circuit 34. Specifically, the output processing unit 38 controls whether to enable or disable the output of the output signals from the plurality of transimpedance amplifiers TIA1 to TIA16 to the selection circuit 34. ｃｎ Based on this, the output signal of at least one of the plurality of transimpedance amplifiers TIA1 to TIA16 is output to the selection circuit 34. In this case, the output signals of the transimpedance amplifiers TIA1 to TIA16 can be appropriately output to the selection circuit 34 according to the timing at which each of the photodiodes PD1 to PD16 receives reflected light.

[0065] In the light receiving device 22a according to this embodiment, output processing circuits 381 to 384 are provided to correspond to the groups G1 to G4, respectively. In this case, the processing of the output processing circuits 381 to 384 is easier than when a single common output processing circuit controls the signal outputs from the multiple transimpedance amplifiers TIA1 to TIA16 to the selection circuit 34. This simplifies the design of the light receiving device 22a.

[0066] Furthermore, in the light receiving device 22a according to this embodiment, two transimpedance amplifiers connected to any two adjacent photodiodes in the photodetector unit 30 belong to different groups. In this case, the signal outputs from the two transimpedance amplifiers to the selection circuit 34 can be enabled in a time-overlapping manner by different output processing circuits. For example, while a signal output from one transimpedance amplifier to the selection circuit 34 is enabled, a signal output from another transimpedance amplifier to the selection circuit 34 can be enabled. This improves the switching speed of the signals output from the selection circuit 34.

[0067] Furthermore, in this embodiment, after a predetermined time has elapsed since any transimpedance amplifier was switched on, or after a predetermined time has elapsed since the output from the output processing circuit corresponding to that transimpedance amplifier became valid, the output signal of that transimpedance amplifier is output from the selection circuit 34. In this case, even if a glitch occurs in each transimpedance amplifier or each output processing circuit, it is possible to prevent the glitch from being output from the selection circuit 34 as part of the output signal of the transimpedance amplifier. This allows for accurate detection of the reflected light received by the photodiodes PD1 to PD16.

[0068] (Modifications) In the above embodiment, the case where each of the groups G1 to G4 has four transimpedance amplifiers has been described, but each group may have two or three transimpedance amplifiers, or may have five or more transimpedance amplifiers. Furthermore, the number of photodiodes provided in the light detection unit 30 may be 15 or less, or 17 or more. Furthermore, the transimpedance amplifiers may be divided into three or less groups, or five or more groups.

[0069] In the above embodiment, when the signal output by the selection circuit 34 is switched from the output signal of one transimpedance amplifier to the output signal of another transimpedance amplifier, the one transimpedance amplifier is maintained in an on state. However, when the signal output by the selection circuit 34 is switched from the output signal of one transimpedance amplifier to the output signal of another transimpedance amplifier, the control circuit 36 ​​may not output the first control signal SG ａ For example, when the light receiving device 22a changes from the state shown in FIG. 6 to the state shown in FIG. 7, the control circuit 36 ​​may output the first control signal SG ａ In this case, the power consumption of the light receiving device 22a can be further reduced.

[0070] In the above-described embodiment, one transimpedance amplifier is always on in each of the groups G1 to G4. However, all transimpedance amplifiers may be off in any of the groups. For example, all transimpedance amplifiers may be off in a group corresponding to an output processing circuit whose signal output is disabled. Specifically, in the state of the light receiving device 22a shown in FIG. 6, the transimpedance amplifiers TIA9 to TIA16 (see FIG. 3) corresponding to the output processing circuits 383 and 384 may be off.

[0071] 10 Optical sensor 12 Power supply section 14 Drive mechanism 16 Light projector 18 Light deflection section 20 Light scanning section 22, 22a Light receiving device 24 Distance measuring section 100 Distance measuring device

Claims

1. A light receiving device comprising: a plurality of photodiodes; a plurality of current-voltage conversion amplifier circuits respectively connected to the plurality of photodiodes; a selection circuit which selects and outputs one of the output signals of the plurality of current-voltage conversion amplifier circuits; and a control circuit which outputs a plurality of first control signals which control the on / off state of each of the plurality of current-voltage conversion amplifier circuits, and a second control signal which controls the selection circuit, wherein the control circuit outputs the first control signal to one of the current-voltage conversion amplifier circuits, and, a predetermined time after the one current-voltage conversion amplifier circuit is turned on, outputs the second control signal to cause the selection circuit to output the output signal of the one current-voltage conversion amplifier circuit.

2. The photodetector according to claim 1, wherein the predetermined time is set to be longer than the length of time from when the current-voltage conversion amplifier circuit is switched from the off state to the on state to when a glitch occurring in the current-voltage conversion amplifier circuit converges.

3. The photodetector according to claim 1, wherein while the selection circuit is outputting the output signal of the one current-voltage conversion amplifier circuit, the control circuit outputs the first control signal to the other current-voltage conversion amplifier circuit to turn on the other current-voltage conversion amplifier circuit, and after the specified time has elapsed since the other current-voltage conversion amplifier circuit was turned on, the control circuit outputs the second control signal to cause the selection circuit to output the output signal of the other current-voltage conversion amplifier circuit.

4. The photodetector according to claim 3, wherein when the signal output by the selection circuit is switched from the output signal of the one current-voltage conversion amplifier circuit to the output signal of the other current-voltage conversion amplifier circuit based on the second control signal, the control circuit outputs the first control signal to the one current-voltage conversion amplifier circuit to turn off the one current-voltage conversion amplifier circuit.

5. The photodetector according to claim 1, further comprising an output processing section that controls enabling and disabling of output signals from the plurality of current-voltage conversion amplifier circuits to the selection circuit, wherein the control circuit further outputs a third control signal that controls the output processing section, and the output processing section outputs at least one output signal from the plurality of current-voltage conversion amplifier circuits to the selection circuit based on the third control signal.

6. The photodetector according to claim 5, wherein the plurality of current-voltage conversion amplifier circuits are divided into a plurality of groups each including two or more of the current-voltage conversion amplifier circuits, the output processing unit includes output processing circuits in the same number as the number of the plurality of groups, one output processing circuit is provided for each of the plurality of groups, the output processing circuit selects one of the output signals of the two or more current-voltage conversion amplifier circuits included in the group and outputs it to the selection circuit, and the selection circuit selects and outputs one of the output signals output from the plurality of output processing circuits based on the second control signal.

7. The photodetector according to claim 5, wherein the specified time is set longer than the length of time from the point at which the current-voltage conversion amplifier circuit is switched from the off state to the on state to the point at which a glitch occurring in the current-voltage conversion amplifier circuit converges, or is set longer than the length of time from the point at which output of the output signal to the selection circuit becomes effective to the point at which a glitch occurring in the output processing unit converges.

8. The light receiving device according to claim 6, wherein the plurality of photodiodes are arranged in a line, and two of the current-voltage conversion amplifier circuits connected to any two of the photodiodes arranged adjacent to each other belong to different groups.

9. An optical sensor comprising: the light receiving device according to any one of claims 1 to 8; and a light projecting device which projects measurement light into a space to be measured in synchronization with the second control signal from the control circuit.

10. The optical sensor according to claim 9, further comprising an optical scanning unit that scans the measurement light in a predetermined direction in the measurement target space.

11. A distance measuring device comprising: an optical sensor according to claim 9; and a distance measuring unit that calculates a distance to an object based on the measurement light and reflected light from the object in the measurement target space.

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