JP2025040062A - Light receiving device, light sensor and distance measuring device - Google Patents

Abstract

To provide a light receiving device, a photosensor, and a ranging device capable of preventing a decrease in detection precision and reducing power consumption.SOLUTION: A light receiving device includes: multiple photodiodes; multiple current/voltage conversion amplification circuit connected to each of the multiple photodiodes; a selection circuit for selecting one of output signals of the multiple current/voltage conversion amplification circuits and outputting it; and a control circuit for outputting first multiple control signals for controlling an on state or an off state of each of the multiple current/voltage conversion amplification circuits and a second control signal for controlling the selection circuit. The control circuit outputs the first control signals to one current/voltage conversion amplification circuit, and outputs an output signal of the one current/voltage conversion amplification circuit to the selection circuit by outputting the second control signals in a predetermined time after the one current/voltage conversion amplification circuit is turned on.SELECTED DRAWING: Figure 2

Description

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

Distance measuring devices that use the TOF (Time Of Flight) method to measure the distance to an object are known. Distance measuring devices that use the TOF method can measure the distance to an object by detecting the time from when measurement light is irradiated onto the object to when the reflected light of that measurement light is received.

For example, the laser distance measurement device disclosed in Patent Document 1 includes a MEMS mirror that deflects the output light output from a light source, a photodetector that detects the reflected light of the output light reflected by an object, a light-receiving 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 light-receiving circuit board, and a rotation mechanism that rotates an optical system including the light source, the MEMS mirror, and the photodetector.

The photodetector has multiple detection elements. The receiver circuit board has multiple transimpedance amplifiers, a switching circuit, and an amplifier circuit. The control circuit board has a control circuit, a TDC circuit, and a signal processing circuit.

The multiple transimpedance amplifiers on the receiving circuit board are respectively connected to the multiple detection elements of the photodetector, convert the current generated by the detection elements into a voltage, and output it as an electrical signal to the switching circuit. The switching circuit outputs an electrical signal based on the current generated from the detection element selected by the control circuit on the control circuit board to the amplifier circuit via the transimpedance amplifier. The amplifier circuit amplifies the electrical signal output from the switching circuit and outputs it to the TDC circuit on the control circuit board. The TDC circuit on the control circuit board outputs a signal 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.

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

In addition, in the laser distance measurement device of Patent Document 1, as described above, the detection element that outputs the electrical signal can be switched by a switching circuit. In this case, a common amplifier circuit can be used to amplify the electrical signal based on the current generated by the multiple detection elements. Patent Document 1 describes that this configuration can further simplify the circuit compared to a configuration in which an amplifier circuit is provided for every detection element.

JP 2018-128432 A

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 believed 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 amplifier circuit.

However, if all the transimpedance amplifiers are turned on at the same time as described above, the power consumption of the device increases. Therefore, in order to reduce power consumption, the inventor 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.

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

Therefore, one example of the objective 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.

(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 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 or off state of each of the plurality of current-voltage conversion amplifier circuits, and a second control signal which controls the selection circuit, and the control circuit outputs the first control signal to one of the current-voltage conversion amplifier circuits, and a predetermined time after one of the current-voltage conversion amplifier circuits is turned on, outputs the second control signal to cause the selection circuit to output the output signal of one of the current-voltage conversion amplifier circuits.

According to the above-mentioned light receiving device, the on and off states of the multiple current-voltage conversion amplifier circuits can be switched by the multiple first control signals output from the control circuit. This allows the on and off states of the current-voltage conversion amplifier circuits to be switched, for example, depending on the timing at which each of the multiple photodiodes receives reflected light. In this case, the power consumption of the light receiving device can be reduced compared to a case in which all the current-voltage conversion amplifier circuits are kept on and one of the output signals of the current-voltage conversion amplifier circuits is selected and output by the selection circuit.

In addition, after a predetermined time has elapsed since any current-voltage conversion amplifier circuit is switched to the on state, 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 makes it possible to accurately detect the reception of reflected light at multiple photodiodes.

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

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.

(3) In the above-mentioned 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 elapsed 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.

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 in the current-voltage conversion amplifier circuit from being output from the selection circuit. Therefore, it is possible to quickly switch between the on and off states of multiple current-voltage conversion amplifier circuits and prevent a glitch in each current-voltage conversion amplifier circuit from being output from the selection circuit. This makes it possible to improve the resolution of the light receiving device while improving the detection accuracy of the reflected light.

(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.

(5) The above-mentioned light receiving device may further include an output processing section that controls whether to enable or disable the output of output signals from the multiple current-voltage conversion amplifier circuits to the selection circuit, and the control circuit may further output a third control signal that controls the output processing section, and the output processing section may output at least one output signal of the multiple 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 may be appropriately output to the selection circuit according to the timing at which each of the multiple photodiodes receives reflected light.

(6) In the above-mentioned light receiving device, the multiple current-voltage conversion amplifier circuits are divided into multiple groups each including two or more current-voltage conversion amplifier circuits, the output processing section includes output processing circuits in the same number as the number of the multiple groups, one output processing circuit is provided for each of the multiple 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 may select and output one of the output signals output from the multiple output processing circuits based on a second control signal. In this case, processing of the output processing circuit is easier than when signal output from the multiple current-voltage conversion amplifier circuits to the selection circuit is controlled by a single common output processing circuit. This makes it easier to design the light receiving device.

(7) In the above light receiving device, the predetermined time may be set longer than the time length from the time when the current-voltage conversion amplifier circuit is switched from the off state to the on state to the time when a glitch that has occurred in the current-voltage conversion amplifier circuit converges, or may be set longer than the time length from the time when the output signal to the selection circuit becomes effective to the time when a glitch that has occurred 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 makes it possible to accurately detect the reception of reflected light at the photodiode.

(8) In the above light receiving device, the multiple photodiodes are arranged in a row, and the 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 can be output to the selection circuit in a time-overlapping manner by different output processing circuits. For example, during the period when the output signal of one current-voltage conversion amplifier circuit is output to the selection circuit, the output signal of the other current-voltage conversion amplifier circuit can start to be output to the selection circuit. This can improve the switching speed of the signals output from the selection circuit.

(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 space to be measured 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.

(10) The optical sensor may further include an optical 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.

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

The present invention provides a light receiving device, an optical sensor, and a distance measuring device that can reduce power consumption while preventing a decrease in detection accuracy.

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 the 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 the control circuit. FIG. 5 is a diagram for explaining the flow of an output signal from the transimpedance amplifier to the selection circuit. FIG. 6 is a diagram for explaining the flow of an output signal from the transimpedance amplifier to the selection circuit. FIG. 7 is a diagram for explaining the flow of an output signal from the transimpedance amplifier to the selection circuit. FIG. 8 is a diagram for explaining the flow of an output signal from the transimpedance amplifier to the selection circuit. FIG. 9 is a diagram for explaining the flow of an output signal from the transimpedance amplifier to the selection circuit.

The following describes the light receiving device, light sensor, and distance measuring device according to the embodiment of the present invention with reference to the drawings.

(Configuration of distance measuring device)
Fig. 1 is a block diagram showing a schematic configuration of a distance measuring device according to an embodiment of the present invention. The distance measuring device 100 according to this embodiment is a device that projects measurement light into a measurement target space, receives light reflected by an object (hereinafter referred to as an object) in the measurement target space, and calculates a distance to the object based on the timing of receiving the reflected light. As shown in Fig. 1, in this embodiment, the distance measuring device 100 includes an optical sensor 10, a power supply unit 12, a driving mechanism 14, and a distance measuring unit 24. The optical sensor 10 includes a light projecting device 16, an optical deflection unit 18, an optical scanning unit 20, and a light receiving device 22.

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 emission of the light source. In this embodiment, the light projecting device 16 projects measurement light into the measurement target space in synchronization with a second control signal SG _b output from a control circuit 36 (described later) of the optical scanning unit 20. The measurement light is pulsed light having a pulse width of, for example, several hundred picoseconds to several tens of nanoseconds.

The light 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 light deflection unit 18 deflects the measurement light emitted from the light projecting device 16 or the reflected light from the measurement target space in a predetermined direction. The focusing unit of the light deflection unit 18 focuses the reflected light toward the light receiving device 22. The light scanning unit 20 includes a swinging element that swings the reflecting unit of the light deflection unit 18. The light scanning unit 20 swings the reflecting unit of the light deflection unit 18 to scan the measurement light deflected by the light 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 need to include the light deflection unit 18. In this case, the light 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.

Figure 2 is a diagram showing a schematic configuration of the light receiving device 22. As shown in Figure 2, the light receiving device 22 includes a light detection unit 30, a conversion unit 32, a selection circuit 34, and a control circuit 36. The light detection unit 30 includes a plurality of photodiodes PD1 to PD16. In this embodiment, the photodiodes PD1 to PD16 are arranged in a row. The reflected light (pulse 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 order. As a result, the reflected light (pulse light) is detected by the photodiodes PD1 to PD16 in order. For example, a known APD array can be used as the light detection unit 30. In addition, the reflected light can be incident on the photodiodes PD1 to PD16 in order not only when the reflected light is incident on the photodiodes PD1 to PD16 once each, but also when the reflected light is incident on the photodiodes PD1 to PD16 multiple times each. For example, reflected light may be incident on each of the photodiodes PD1 to PD16 twice in sequence.

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 them 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.

The selection circuit 34 selects one of the output signals of the transimpedance amplifiers TIA1 to TIA16 based on a second control signal _SGb (described later) output from the control circuit 36, and outputs the selected signal 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.

The control circuit 36 outputs a first control signal SG _a for controlling the on or off state of each of the transimpedance amplifiers TIA1 to TIA16, and a second control signal SG _b for controlling the selection circuit 34. In this embodiment, the control circuit 36 outputs the first control signal SG _a to each of the multiple transimpedance amplifiers TIA1 to TIA16. Note that the on state of the transimpedance amplifier refers to a state in which power is supplied to the transimpedance amplifier and a signal is output, and the off state refers to a state in which power is not supplied to the transimpedance amplifier or a signal is not output.

In this embodiment, the control circuit 36 outputs a plurality of first control signals SG a so as 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. In addition, in this embodiment, the control circuit 36 outputs a second control signal SG _b so that the output signals from the plurality of transimpedance amplifiers TIA1 to TIA16 are sequentially output from the selection circuit _34. In addition, 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 a control signal to the light projecting device 16 to project the measurement light in synchronization with the second control signal SG _b output to the selection circuit 34. In other words, the control circuit 36 causes the light projecting device 16 to project the measurement light in synchronization with the switching of the output signal output from the selection circuit 34. In addition, when the reflected light is made to be incident on the photodiodes PD1 to PD16 multiple times in sequence, a control signal is output from the control circuit 36 to the light-projecting device 16 so that the measurement light is projected multiple times each time the output signal output from the selection circuit 34 is switched.

In this embodiment, the control circuit 36 outputs a first control signal SG _a to one transimpedance amplifier, and after a predetermined time has elapsed since the transimpedance amplifier was turned on, outputs a second control signal SG _b to cause 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.

In the present embodiment, for example, while the selection circuit 34 is outputting an output signal of one transimpedance amplifier, the control circuit 36 outputs a first control signal SG _a to the other transimpedance amplifier to turn on the other transimpedance amplifier, and after a predetermined time has elapsed since the other transimpedance amplifier turned on, outputs a second control signal SG _b to cause the selection circuit 34 to output the output signal of the other transimpedance amplifier. This makes it possible to prevent a glitch in the transimpedance amplifier TIA2 from being output from the selection circuit 34, even if the transimpedance amplifier TIA2 connected to the photodiode PD2 is turned on during the period from when the photodiode PD1 receives the reflected light to when the photodiode PD2 receives the reflected light, for example, when the photodiode PD1 and the photodiode PD2 receive the reflected light. Therefore, it is possible to prevent a glitch in the transimpedance amplifiers TIA1 to TIA16 from being output from the selection circuit 34, while switching between the on and off states of the transimpedance amplifiers TIA1 to TIA16 at high speed. In this case, the resolution of the light receiving device 22 can be improved by quickly switching the on/off states of the transimpedance amplifiers TIA1 to TIA16, while preventing the selection circuit 34 from outputting glitches, thereby improving the detection accuracy of reflected light.

The above-mentioned predetermined time is set, for example, to be longer than the time length from when the transimpedance amplifier is switched from the off state to the on state to when the glitch occurring in the transimpedance amplifier converges. In this case, even if a glitch occurs in each transimpedance amplifier, it is possible to reliably prevent the glitch from being output from the selection circuit 34 as part of the output signal of the transimpedance amplifier.

Referring to FIG. 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 configuration of the optical sensor 10 other than the light receiving device 22 can use the configuration of an optical sensor of a known distance measuring device.

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 include an input terminal to which power is supplied from outside the distance measurement device 100.

The drive mechanism 14 includes, for example, a motor, and rotates the light projector 16, the light deflection unit 18, the light scanning unit 20, and the light receiving unit 22 (hereinafter abbreviated as the light projector 16, etc.). In this embodiment, the drive mechanism 14 rotates the light projector 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 projector 16, etc. around a rotation axis extending in the vertical direction. By rotating the light projector 16, etc. by the drive mechanism 14 in this way, 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 that can perform three-dimensional distance measurement, so a detailed description of the drive mechanism 14 is omitted.

(Effects of this embodiment)
In this embodiment, the on and off states of the transimpedance amplifiers TIA1 to TIA16 can be switched by the multiple first control signals SG _a output from the control circuit 36. For example, the on and off states of the transimpedance amplifiers TIA1 to TIA16 can be switched according to 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 the case where one of the output signals of the transimpedance amplifiers TIA1 to TIA16 is selected and output by the selection circuit 34 while all of the transimpedance amplifiers TIA1 to TIA16 are kept on.

In addition, in this embodiment, after a predetermined time has elapsed since any transimpedance amplifier is switched to the on state, 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 from the selection circuit 34 as part of the output signal of the transimpedance amplifier. This makes it possible to accurately detect the reception of reflected light by the photodiodes PD1 to PD16.

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.

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

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

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

The selection circuit 34 has multiple input terminals IT1 to IT4. The input terminals IT1 to IT4 are connected to the output processing circuits 381 to 384, respectively.

The control circuit 36 outputs a plurality of first control signals SG _an (n=1 to 16) to the conversion unit 32, 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. The first control signals SG _a1 to SG _a16 correspond to the transimpedance amplifiers TIA1 to TIA16, respectively. The second control signals SG _b1 to SG _b4 correspond to the input terminals IT1 to IT4, respectively. The third control signals SG _c1 to SG _c4 correspond to the output processing circuits 381 to 384, respectively.

In this embodiment, the corresponding transimpedance amplifiers TIA1 to TIA16 are turned on in synchronization with the rising edge to high level of the first control signal SG _an output from the control circuit 36 to the conversion unit 32. Also, the corresponding transimpedance amplifiers TIA1 to TIA16 are turned off in synchronization with the falling edge to low level of the first control signal SG _an . In this embodiment, the first control signal SG _an is generated so that multiple transimpedance amplifiers belonging to the same group are not turned on at the same time.

Further, based on the second control signal SG _bn output from the control circuit 36 to the selection circuit 34, the selection circuit 34 outputs a signal input to one of the input terminals IT1 to IT4. In this embodiment, when the second control signal SG _bn is at a high level, the selection circuit 34 outputs a signal input to the corresponding input terminal IT1 to IT4. Note that, in this embodiment, the second control signal SG _bn is generated so that one of the input terminals IT1 to IT4 is selected. In other words, the second control signal SG _bn is generated so that two or more input terminals are not selected simultaneously by the selection circuit 34. In this embodiment, the measurement light is projected by the light projecting device 16 in synchronization with the switching of the selected input terminals IT1 to IT4.

Furthermore, based on a third control signal _SGcn output from the control circuit 36 to the output processing unit 38, the output processing circuits 381 to 384 control whether to enable or disable the output of the output signals of the transimpedance amplifiers of the corresponding groups to the selection circuit 34. In this embodiment, the output processing circuits 381 to 384 output the output signals of the transimpedance amplifiers to the selection circuit 34 when the third control signal _SGcn is at a high level.

The operation of the light receiving device 22a will be described below with an example. Note that the following describes a case where the photodiode that receives reflected light is switched to the photodiodes PD1 to PD3 in order. Figure 4 is a diagram showing the waveform of the control signal output from the control circuit 36. Figure 4 also shows a glitch output from the output processing circuits 381 and 382 to the selection circuit 34. Figures 5 to 9 are diagrams for explaining the flow of the output signals from the transimpedance amplifiers TIA1 to TIA3 to the selection circuit 34.

4, when the photodiode PD1 receives reflected light, the first control signal SG _a1 , the second control signal SG _b1 , and the third control signal SG _c1 are all at high level. In this case, as shown in FIG. 5, the output signal of the transimpedance amplifier TIA1 based on the output current of the photodiode PD1 is output to the input terminal IT1 of the selection circuit 34 by the output processing circuit 381. 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 the ON state.

4, the third control signal _SGc2 rises before the reflected light is received by the photodiode PD2. This enables the 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, since 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, the glitch can be prevented from being output from the selection circuit 34.

After a predetermined time has elapsed since the third control signal _SGc2 rose, the photodiode that receives the reflected light is switched to the photodiode PD2. In synchronization with this, the second control signal _SGb1 and the third control signal _SGc1 fall, and the second control signal _SGb2 rises. As a result, as shown in FIG. 7, 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 to the input terminal IT2 of the selection circuit 34 by the output processing circuit 382. 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).

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

4, the first control signal SG _a3 and the third control signal SG _c1 rise before the reflected light is received by the photodiode PD3. The first control signal SG a1 falls in synchronization with the rise of the first control signal SG _a3 and the third control signal SG _c1 . This switches the on/off state of the transimpedance amplifiers TIA1 and _TIA3 , and enables the 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, since 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, 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, even if a glitch occurs in the transimpedance amplifier TIA3 or the output processing circuit 381, the glitch can be prevented from being output from the selection circuit 34.

After a predetermined time has elapsed since the first control signal SG _a3 and the third control signal SG _c1 rise, the photodiode that receives the reflected light is switched to the photodiode PD3. In synchronization with this, the second control signal SG _b2 and the third control signal SG _c2 fall, and the second control signal SG _b1 rises. As a result, as shown in FIG. 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 to the input terminal IT1 of the selection circuit 34 by the output processing circuit 381. 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).

Referring to FIG. 4, the time length from the time when the transimpedance amplifier TIA3 is turned on or the time when the signal output of the output processing circuit 381 is enabled to the time when the input terminal IT1 is selected by the selection circuit 34 is preferably set to be longer than the time length from the time when the transimpedance amplifier TIA3 is turned on or the time when the signal output of the output processing circuit 381 is enabled to the time when the glitch occurring in the transimpedance amplifier TIA3 or the output processing circuit 381 converges. This can reliably prevent the glitch occurring in the transimpedance amplifier TIA3 or the output processing circuit 381 from being output from the selection circuit 34.

In the light receiving device 22a according to this embodiment, the output processing section 38 controls whether to enable or disable the output of the output signals from the multiple transimpedance amplifiers TIA1 to TIA16 to the selection circuit 34. Specifically, the output processing section 38 outputs at least one output signal from the multiple transimpedance amplifiers TIA1 to TIA16 to the selection circuit 34 based on a third control signal _SGcn output from the control circuit 36. 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.

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 the signal output from the multiple transimpedance amplifiers TIA1 to TIA16 to the selection circuit 34 is controlled by a single common output processing circuit. This makes it easier to design the light receiving device 22a.

In addition, in the light receiving device 22a according to this embodiment, the two transimpedance amplifiers connected to any two photodiodes arranged adjacent to each other in the light detection 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, during a period in which a signal output from one transimpedance amplifier to the selection circuit 34 is enabled, a signal output from the other transimpedance amplifier to the selection circuit 34 can be enabled. This can improve the switching speed of the signal output from the selection circuit 34.

In addition, in this embodiment, the output signal of any transimpedance amplifier is output from the selection circuit 34 after a predetermined time has elapsed since the transimpedance amplifier was switched to the on state, or after a predetermined time has elapsed since the output from the output processing circuit of that transimpedance amplifier became effective. In this case, even if a glitch occurs in each transimpedance amplifier or each output processing circuit, the glitch can be prevented from being output from the selection circuit 34 as part of the output signal of the transimpedance amplifier. This makes it possible to accurately detect the reception of reflected light by the photodiodes PD1 to PD16.

(Modification)
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. The number of photodiodes provided in the light detection unit 30 may be 15 or less, or 17 or more. The transimpedance amplifiers may be divided into three or less groups, or five or more groups.

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 the 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 output the first control signal SG _a to the one transimpedance amplifier to turn the one transimpedance amplifier off. 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 so that the transimpedance amplifier TIA1 is turned off. In this case, the power consumption of the light receiving device 22a can be further reduced.

In the above embodiment, one transimpedance amplifier is always on in each of groups G1 to G4, but 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 in which 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.

10 Optical sensor 12 Power supply section 14 Drive mechanism 16 Light projection device 18 Light deflection section 20 Light scanning section 22, 22a Light receiving device 24 Distance measurement section 100 Distance measurement device

Claims (11)

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;
a control circuit that outputs a plurality of first control signals that control an on state or an off state of each of the plurality of current-voltage conversion amplifier circuits, and a second control signal that controls the selection circuit;
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.
Light receiving device. the predetermined time is set to be longer than a time length from a point in time when the current-voltage conversion amplifier circuit is switched from the off state to the on state to a point in time when a glitch occurring in the current-voltage conversion amplifier circuit is converged.
The light receiving device according to claim 1 . the control circuit outputs the first control signal to the other current-voltage conversion amplifier circuit while the selection circuit is outputting the output signal of the one current-voltage conversion amplifier circuit, thereby turning on the other current-voltage conversion amplifier circuit, and outputs the second control signal after the predetermined time has elapsed since the other current-voltage conversion amplifier circuit was turned on, thereby causing the selection circuit to output the output signal of the other current-voltage conversion amplifier circuit.
The light receiving device according to claim 1 . 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.
The light receiving device according to claim 3 . an output processing unit that controls whether to enable or disable output of the output signals from the plurality of current-voltage conversion amplifier circuits to the selection circuit;
The control circuit further outputs a third control signal that controls the output processing unit,
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.
The light receiving device according to claim 1 . 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 the number of which is equal to the number of the 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 the selected one to the selection circuit;
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.
The light receiving device according to claim 5 . The predetermined time is set to be longer than the time length from the time when the current-voltage conversion amplifier circuit is switched from the off state to the on state to the time when a glitch occurring in the current-voltage conversion amplifier circuit converges, or is set to be longer than the time length from the time when the output of the output signal to the selection circuit becomes effective to the time when a glitch occurring in the output processing unit converges.
The light receiving device according to claim 5 . The plurality of photodiodes are arranged in a line,
Two of the current-voltage conversion amplifier circuits connected to any two of the photodiodes arranged adjacent to each other belong to different groups.
The light receiving device according to claim 6. The light receiving device according to any one of claims 1 to 8,
a light projecting device that projects measurement light into a measurement target space in synchronization with the second control signal from the control circuit,
Light sensor. Further comprising a light scanning unit that scans the measurement light in a predetermined direction in the measurement target space.
The optical sensor of claim 9. An optical sensor according to claim 9;
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,
Distance measuring device.

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