JP2020106350A - Light projection/receiving device, light projection/receiving method, program, and recording medium - Google Patents

Abstract

To provide a light projection/receiving device, a light projection/receiving method, a program and a recording medium with which it is possible to detect the peak of a received light signal while adjusting the light reception sensitivity of a light receiving element in accordance with the distance to an object.SOLUTION: Provided is a distance measuring device 100 comprising: a light source 11A for emitting light toward an object; a photoelectric conversion element 12A for receiving light reflected by the object and outputting a current that corresponds to the received light; a first voltage application unit for gradually raising a voltage value and applying a first voltage to the photoelectric conversion element; a conversion unit for converting the current outputted from the photoelectric conversion element to a voltage and outputting the resulting voltage; and an adjustment circuit including a capacitor that has capacitance based on the interterminal capacitance of the photoelectric conversion element and connected at one end to the input of the conversion unit and a second voltage application unit for applying a second voltage 180 degrees out of phase with the first voltage to the other end of the capacitor.SELECTED DRAWING: Figure 1

Description

The present invention relates to a light projecting/receiving device, a light projecting/receiving method, a program, and a recording medium.

There is known a distance measuring device that measures a distance to an object by irradiating the object with laser light and receiving and analyzing the laser light reflected by the object (for example, Patent Document 1). .. As a distance measuring method of such a distance measuring device, there is a TOF (Time of Flight) method, for example. In the TOF method, the time from when the laser light is emitted to when the laser light is reflected by the object and returns is measured, and the distance to the object is calculated based on the measured time.

In such a distance measuring device, the light amount of the return light from the object is usually extremely smaller than the light amount of the emitted laser light. Therefore, it is necessary to increase the sensitivity of the light receiving element. For example, when the light receiving element is composed of an APD (Avalanche Photodiode), the light receiving sensitivity can be increased by increasing the reverse bias voltage applied to the APD.

However, since the amount of return light is inversely proportional to the square of the distance to the object, when the sensitivity of the light receiving element is set high, the amount of return light reflected at a short distance increases too much. There is. In particular, when the emitted laser light is reflected by an optical component such as a lens inside the distance measuring device, the reflected light becomes a reflected light at a close range, and thus has an extremely high intensity close to that of the emitted light. Therefore, when the sensitivity of the light receiving element is set high, the light receiving element may be saturated by receiving the reflected light from a short distance.

Therefore, a distance measuring device has been proposed that changes the light receiving sensitivity of the light receiving element according to the distance to the object (for example, Patent Document 2).

JP, 2005-129646, A JP, 2003-130953, A

When the light receiving element is composed of an APD, in order to increase the light receiving sensitivity according to the distance to the object, for example, a reverse bias voltage applied to the APD according to the time elapsed after the laser light is emitted. Raise. At that time, in addition to the original output current of the APD based on the reception of the return light and the photoelectric conversion, a charging/discharging current is generated due to the terminal capacitance between the anode and cathode of the APD. This charge/discharge current has a value obtained by differentiating the bias voltage applied to the cathode of the APD with respect to time. Therefore, for example, when the voltage value of the bias voltage is monotonically increased with time, the charging/discharging current becomes a constant current, and the current for the constant current is added to the output current of the APD.

The output current of the APD is IV-converted (current-voltage converted) at the output section provided at the subsequent stage of the APD and output as a voltage signal. When the charging/discharging current due to the inter-terminal capacitance is added to the output current of the APD and the current value is increased as described above, the current value may exceed the dynamic range of IV conversion in the output section. .. Since the current exceeding the dynamic range is not converted into a voltage, the voltage signal output from the output section has a vertically crushed waveform. Therefore, when the dynamic range of the IV conversion is lower than the charge/discharge current due to the inter-terminal capacitance, there is a problem that the peak of the voltage signal (light reception signal) based on the received return light cannot be detected. It was

In this way, when the bias voltage applied to the light receiving element is changed with time, the charge/discharge current due to the inter-terminal capacitance of the light receiving element exceeds the dynamic range of IV conversion, and the peak of the light receiving signal is detected. An example of the problem is that there is a possibility that it cannot be done.

The present invention has been made in view of the above points, and it is possible to adjust the light receiving sensitivity of a light receiving element according to the distance to an object and to project and receive a peak of a light receiving signal. One of the purposes is to provide a method, a program, and a recording medium.

The invention according to claim 1 is a distance measuring apparatus, which receives a light source that emits light toward an object, receives light reflected by the object, and outputs a current according to the received light. A photoelectric conversion element, a first voltage application section that gradually increases a voltage value and applies a first voltage to the photoelectric conversion element, and a conversion section that converts the current output from the photoelectric conversion element into a voltage and outputs the voltage. A capacitor having a capacitance based on a capacitance between terminals of the photoelectric conversion element and having one end connected to an input of the conversion unit; and a second voltage having a phase opposite to the first voltage applied to the other end of the capacitor And a second voltage applying section for adjusting the voltage.

The invention according to claim 7 is a light source, a photoelectric conversion element, a first voltage application section that applies a first voltage to the photoelectric conversion element, a conversion section that converts a current into a voltage and outputs the voltage, and the photoelectric conversion element. A light projecting/receiving light having a capacitor having a capacitance based on a capacitance between terminals of a conversion element and having one end connected to an input of the conversion unit, and a second voltage application unit applying a second voltage to the other end of the capacitor. A method of projecting and receiving light by an apparatus, wherein the light source emits light toward an object, and the first voltage application unit gradually increases a voltage value to apply the first voltage to the photoelectric conversion element. The step of applying the voltage, the photoelectric conversion element receiving the light reflected by the object, outputting a current corresponding to the received light, and the second voltage applying section using the first voltage. A step of applying the second voltage having a phase opposite to that of the second voltage to the other end of the capacitor, and the conversion unit converts the current output from the photoelectric conversion element and the current output from the capacitor into a voltage and outputs the voltage. And a step of performing.

The invention according to claim 8 is a light source, a photoelectric conversion element, a first voltage application section that applies a first voltage to the photoelectric conversion element, a conversion section that converts a current into a voltage and outputs the voltage, and the photoelectric conversion element. A light projecting/receiving light having a capacitor having a capacitance based on a capacitance between terminals of a conversion element and having one end connected to an input of the conversion unit, and a second voltage application unit applying a second voltage to the other end of the capacitor. A step of controlling the light source so as to emit light toward an object to a computer mounted on the apparatus; and a step of gradually increasing a voltage value to apply the first voltage to the photoelectric conversion element. 1 controlling the voltage application section, receiving the light reflected by the object, controlling the photoelectric conversion element so as to output a current according to the received light, and the first voltage Controls the second voltage applying unit to apply the second voltage having the opposite phase to the other end of the capacitor, and outputs the current output from the photoelectric conversion element and the current output from the capacitor as a voltage. And controlling the conversion unit so as to output the converted data.

The invention according to claim 9 is a light source, a photoelectric conversion element, a first voltage application section that applies a first voltage to the photoelectric conversion element, a conversion section that converts a current into a voltage and outputs the voltage, and the photoelectric conversion element. A light projecting/receiving light having a capacitor having a capacitance based on a capacitance between terminals of a conversion element and having one end connected to an input of the conversion unit, and a second voltage application unit applying a second voltage to the other end of the capacitor. A step of controlling the light source so as to emit light toward an object to a computer mounted on the apparatus; and a step of gradually increasing a voltage value to apply the first voltage to the photoelectric conversion element. 1 controlling the voltage application section, receiving the light reflected by the object, controlling the photoelectric conversion element so as to output a current according to the received light, and the first voltage Controls the second voltage applying unit to apply the second voltage having the opposite phase to the other end of the capacitor, and outputs the current output from the photoelectric conversion element and the current output from the capacitor as a voltage. And a step of controlling the conversion unit so as to output the converted data.

It is a block diagram which shows the structure of the distance measuring apparatus of a present Example. It is a circuit diagram which shows the structure of the light-receiving part of a present Example. 7 is a time chart showing a waveform of a bias voltage applied to an APD. 7 is a time chart showing a waveform of a current supplied to an output unit of a comparative example. 7 is a time chart showing a waveform of a voltage output from the output unit of the comparative example. 7 is a time chart showing the voltage waveform of the adjustment voltage and the charging/discharging current waveform of the adjustment capacitor of the present embodiment. It is a time chart which shows the waveform of the electric current supplied to the output part of this example, and the voltage output from the output part. It is a circuit diagram which shows the modification of a light-receiving part.

Hereinafter, preferred embodiments of the present invention will be described in detail. In the following description of the embodiments and the accompanying drawings, substantially the same or equivalent parts are designated by the same reference numerals.

FIG. 1 is a block diagram showing a schematic configuration of a distance measuring device 100 of this embodiment. The distance measuring device 100 is an optical distance measuring device that optically measures a distance to an object. The range finder 100 measures the distance to the object OJT by irradiating the laser beam toward a predetermined area and receiving the laser beam reflected by the object OJT in the predetermined area. The distance measuring device 100 includes an emitting unit 11, a light receiving unit 12, a control unit 13, and a distance calculating unit 14.

The emission unit 11 includes a laser light source 11A that emits laser light, and a laser emission drive unit 11B that drives the laser light source 11A. The laser light source 11A is a light source that emits laser light, and is composed of, for example, a laser diode that emits pulsed light. In the following description, the pulsed light emitted from the laser light source 11A is referred to as emitted light OL.

The light receiving unit 12 includes a light receiving element 12A and a light receiving signal detection unit 12B. The light receiving element 12A is composed of a photoelectric conversion element such as an APD (Avalanche Photodiode). The light receiving element 12A receives the reflected light RL, which is the laser light reflected by the object OJT in the predetermined area, and converts the light intensity of the received reflected light RL into a current signal. The received light signal detection unit 12B generates the received light signal RS by performing IV conversion on the current signal converted by the light receiving element 12A.

The control unit 13 includes, for example, a CPU (Central Processing Unit), and controls processing of each unit of the distance measuring apparatus 100. For example, the control unit 13 controls the drive of the laser light source 11A by the laser emission drive unit 11B. Further, the control unit 13 supplies the distance calculation unit 14 with information such as the emission timing and intensity of the emitted light OL, which is necessary for the distance calculation unit 14 to calculate the distance.

The distance calculation unit 14 calculates the distance to the object OJT based on the light reception signal RS generated by the light reception unit 12. For example, the distance calculation unit 14 calculates the distance to the object by the TOF (Time of Flight) method based on the information on the emission timing of the emitted light OL and the light reception timing of the reflected light RL.

Next, the configuration of the light receiving unit 12 in this embodiment will be described. FIG. 2 is a circuit diagram showing the configuration of the light receiving unit 12. The light receiving unit 12 supplies the APD 20, a bias voltage applying unit 21 that applies a bias voltage to the APD 20, an output unit 22 that converts the current signal output from the APD 20 into a voltage signal and outputs the voltage signal, and supplies the APD 20 to the output unit 22. The adjustment capacitor 30 and the adjustment voltage generator 31 for adjusting the generated current are included. The bias voltage applied to the APD 20 is a so-called reverse bias voltage (reverse bias voltage), but will be simply referred to as a bias voltage in the following description.

The cathode of the APD 20 is connected to the bias voltage applying unit 21, and the anode is connected to the output unit 22. The APD 20 receives the reflected light RL, converts it into a current signal, multiplies it by a multiplication factor according to the bias voltage applied to the cathode, and outputs it from the anode.

The bias voltage application unit 21 is connected to the AC power supply AS and the DC power supply DS and generates a bias voltage based on the AC voltage output from the AC power supply AS and the DC voltage output from the DC power supply DS. The bias voltage application unit 21 includes an operational amplifier 23, a capacitor 24, and a resistance element 25.

The operational amplifier 23 has a non-inverting input terminal connected to the AC power supply AS. The inverting input terminal and the output terminal of the operational amplifier 23 are connected to each other to form a voltage follower circuit. The operational amplifier 23 has a function as a buffer having a gain of 1.

The capacitor 24 has one end connected to the output end of the operational amplifier 23 and the other end connected to the cathode of the APD 20. The capacitor 24 has a function as a coupling capacitor that cuts a DC component from the output of the operational amplifier 23.

The resistance element 25 has one end connected to the DC power supply DS and the other end connected to a node connecting the other end of the capacitor 24 and the cathode of the APD 20.

The output unit 22 is configured as an IV conversion circuit that converts the current signal output from the APD 20 into a voltage signal and outputs the voltage signal. The output unit 22 includes an operational amplifier 26 and a resistance element 27.

The non-inverting input terminal of the operational amplifier 26 is connected to a predetermined potential (for example, ground). The output terminal and the inverting input terminal of the operational amplifier 26 are connected via a resistance element 27 as a feedback resistance. FIG. 3 is a time chart showing the light emission waveform of the emitted light OL by the emission unit 11 and the voltage waveform of the bias voltage applied to the APD 20 by the bias voltage application unit 21.

As can be seen from the light emission waveform in FIG. 3, the emission unit 11 emits the emission light OL with the emission timing at time t1. From time t1 to time t2 is the distance measurement period DMP for the distance measuring apparatus 100 to calculate the distance. The light receiving unit 12 receives the reflected light RL incident on the distance measuring device 100 during the distance measurement period DMP.

From time t2 to time t5 is the waiting/returning period WRP until the emitting unit 11 becomes ready to emit the next emitted light OL. In the waiting/returning period WRP, the emitting section 11 does not emit the emitted light OL, and the light receiving section 12 does not receive the reflected light RL.

The emission unit 11 emits the emission light OL again at the time point t5 after the distance measurement period DMP and the standby/return period WRP. That is, the time period from the time point t1 to the time point t5 is one cycle of the distance calculation by the distance measuring device 100.

The bias voltage application unit 21 generates a bias voltage based on the AC voltage supplied from the AC power supply AS and the DC voltage supplied from the DC power supply DS. In the present embodiment, the bias voltage application unit 21 generates a bias voltage such that the voltage value monotonously increases until time t2, starting from time t1 when the emitting unit 11 emits the emitted light OL.

In FIG. 3, the case where the voltage value of the bias voltage is raised in a linear function is shown as an example. For example, the bias voltage application unit 21 generates a bias voltage such that the voltage value increases at a constant rate from the minimum value Vo to the maximum value Vx from the time point t1 to the time point t2. The portion corresponding to the voltage value from 0V to the minimum value Vo is the voltage component of the DC voltage supplied from the DC power supply DS. The portion where the voltage value changes from the minimum value Vo to the maximum value Vx is the voltage component of the AC voltage supplied from the AC power supply AS.

Further, the bias voltage application unit 21 maintains the voltage value of the bias voltage at the maximum value Vx which is a constant value for a predetermined period PP1 from the time point t2 to the time point t3. Then, after the elapse of the predetermined period PP1, the bias voltage application unit 21 gradually reduces the bias voltage. For example, the bias voltage applying section 21 linearly decreases the voltage value from the maximum value Vx to the minimum value Vo at a decrease rate corresponding to the increase rate from the time t1 to the time t2 after the lapse of the predetermined period PP1. Generate a bias voltage. The bias voltage application unit 21 reduces the bias voltage to the minimum value Vo, and then maintains the voltage value of the bias voltage at a constant minimum value Vo for a predetermined period PP2 from the time t4 to the time t5. To do.

The bias voltage applying unit 21 applies the bias voltage to the cathode of the APD 20 while changing the voltage value of the bias voltage with time. Since the voltage value of the bias voltage increases at a constant rate from the time t1 over the distance measurement period DMP, it becomes a voltage value proportional to the elapsed time after the emission light OL is emitted.

According to such a configuration, the voltage value of the bias voltage is small in the time zone in which the reflected light from a short distance is received, and the voltage value of the bias voltage is large in the time zone in which the reflected light from a long distance is received. Since the multiplication factor of the current signal by the APD 20 changes according to the voltage value of the bias voltage, the multiplication factor is small for the reflected light RL from a short distance and the multiplication factor is large for the reflected light RL from a long distance. Become.

Since the light amount of the reflected light RL is inversely proportional to the square of the distance to the object, unlike the present embodiment, if the light receiving sensitivity of the light receiving element 12 is set in accordance with the reflected light RL from a long distance, The light receiving element 12 may be saturated by receiving the reflected light RL from a short distance.

However, according to the bias voltage application unit 21 of the present embodiment, by applying the bias voltage according to the elapsed time after the emission light OL is emitted to the APD 20, the light receiving unit 12 according to the distance to the object. It is possible to adjust the light receiving sensitivity of. Therefore, it is possible to set the sensitivity of the light receiving element to be high with respect to the reflected light from a long distance while preventing the light receiving element from being saturated by receiving the reflected light from a short distance.

Referring to FIG. 2 again, the light receiving unit 12 includes the adjusting capacitor 30 and the adjusting voltage generating unit 31. The adjustment capacitor 30 and the adjustment voltage generation unit 31 have a function of adjusting the current supplied from the APD 20 to the output unit 22. This function will be described below.

When the bias voltage application unit 21 applies a bias voltage to the APD 20, an inter-terminal capacitance Capd as shown by a broken line in FIG. 2 is generated between the anode and cathode of the APD 20. Due to the inter-terminal capacitance Capd, the charge/discharge current Iapd flows between the anode of the APD 20 and the input end of the output unit 22. The adjustment capacitor 30 and the adjustment voltage generation unit 31 adjust the current supplied from the APD 20 to the output unit 22 according to the charge/discharge current Iapd generated by the inter-terminal capacitance Capd of the APD 20.

The adjustment capacitor 30 has one end connected to the adjustment voltage generation unit 31 and the other end connected to a node connecting the anode of the APD 20 and the input end of the output unit 22. The adjustment capacitor 30 has a capacitance value equivalent to the inter-terminal capacitance Capd of the APD 20, for example.

The adjustment voltage generation unit 31 generates an adjustment voltage for adjusting the charge/discharge current Iapd generated by the inter-terminal capacitance Capd of the APD 20. The adjustment voltage generation unit 31 includes an operational amplifier 32, a resistance element 33, and a resistance element 34.

The non-inverting input terminal of the operational amplifier 32 is connected to a predetermined potential (for example, ground). The inverting input terminal of the operational amplifier 32 is connected to the AC power supply AS via the resistance element 33. The output terminal and the inverting input terminal of the operational amplifier 32 are connected via a resistance element 34 as a feedback resistance.

The adjustment voltage generation unit 31 generates an adjustment voltage that changes with time in the direction opposite to the bias voltage (that is, an adjustment voltage having a phase opposite to the bias voltage) based on the AC voltage supplied from the AC power supply AS. The generated adjustment voltage is converted into an adjustment current via the adjustment capacitor 30 and supplied to the input terminal of the output unit 22. That is, the adjustment voltage generation unit 31 and the adjustment capacitor 30 form an adjustment circuit that supplies an adjustment current to the output unit 22.

FIG. 4 shows a light receiving section having a bias voltage applying section 21 similar to that of the present embodiment and not having an adjusting capacitor 30 and an adjusting voltage generating section 31 as in the present embodiment (hereinafter referred to as a light receiving section of a comparative example. 4B is a diagram schematically showing a waveform of a current supplied to the output unit 22 in FIG.

Assuming that the light receiving unit 12 receives the reflected light RL at the time point after the return time RT from the time point t1 when the emitting unit 11 outputs the outgoing light OL, the waveform of the current signal supplied from the APD 20 to the output unit 22 is ideal. Specifically, the signal waveform is shown as "desired current waveform" in FIG. That is, the ideal current waveform has a peak immediately after receiving the reflected light RL and has 0 A in other periods.

However, as shown in FIG. 2, when a bias voltage is applied to the cathode of the APD 20, an inter-terminal capacitance Capd is generated between the anode and the cathode of the APD 20. A charge/discharge current based on the inter-terminal capacitance Capd flows between the anode of the APD 20 and the input end of the output unit 22. The charge/discharge current Iapd based on the inter-terminal capacitance Capd has a value obtained by differentiating the bias voltage applied to the cathode of the APD 20 with respect to time.

Referring again to FIG. 4, the waveform of the current signal actually output from the APD 20 due to the charging/discharging current Iapd based on the inter-terminal capacitance Capd becomes a signal waveform shown as “current waveform of comparative example” in FIG. 4. .. That is, since the bias voltage applying unit 21 of the comparative example raises and lowers the voltage value of the bias voltage in a linear function as shown by the alternate long and short dash line, a constant charge/discharge current is output from the APD 20 during the rising and falling periods. It flows to and from the part 22. As a result, in the distance measurement period DMP, the current waveform of the current supplied to the output unit 22 becomes a current waveform in which the current value of the charge/discharge current Iapd is increased from the ideal current waveform. Further, during the period in which the voltage value of the bias voltage in the standby/recovery period WRP monotonously decreases, a constant current corresponding to the charge/discharge current Iapd flows from the output unit 22 to the APD 20 (that is, from the APD 20 to the output unit 22 is negative). A constant current flows).

FIG. 5 is a time chart showing the waveform of the current supplied to the output unit 22 of the comparative example and the voltage waveform obtained by IV converting the current in the output unit 22.

The current supplied to the output unit 22 is a current obtained by increasing the waveform of the output current from the APD 20 by the current corresponding to the charging/discharging current Iapd. When the resistance value of the resistance element 27 of the output unit 22 is R1, when a constant current corresponding to the charge/discharge current Iapd is IV converted by the output unit 22, the voltage based on the charge/discharge current Iapd is V=−Iapd×R1. Becomes

However, the current exceeding the dynamic range range of the IV conversion by the output unit 22 is not converted into a voltage. For example, assuming that the current range of the dynamic range for IV conversion is −DA to DA and the voltage range is −DV to DV, the current before the IV conversion has a portion that exceeds DA and a portion that falls below −DA. Even if it does, that part is not reflected in the voltage after IV conversion. As a result, the voltage after I-V conversion has a voltage waveform that is flattened and inverted in the voltage range -DV to DV, as shown as "I-V conversion output waveform" in FIG.

Therefore, when the upper limit of the dynamic range of the IV conversion is set lower than the current value of the charging/discharging current Iapd, no peak appears in the light receiving signal RS output from the output unit 22 in the light receiving unit of the comparative example. , It is impossible to obtain the information on the light receiving timing necessary for calculating the distance. In order to obtain the peak of the received light signal RS, the dynamic range of IV conversion must be widened, which causes a problem that the circuit scale increases.

On the other hand, in the distance measuring apparatus of the present embodiment, an adjustment voltage that changes with time in the direction opposite to the bias voltage is generated, converted into an adjustment current and supplied to the output unit 22, so that the APD 20 transfers the output voltage to the output unit 22. It is possible to regulate the current supplied.

FIG. 6 is a time chart showing the voltage waveform of the adjustment voltage and the charging/discharging current waveform of the adjustment capacitor in the distance measuring apparatus of this embodiment.

The bias voltage has a constant voltage value from the minimum value Vo to the maximum value Vx (that is, as a linear function) from the time point t1 when the emitting section 11 emits the emitted light OL as a starting point until the time point t2. Rise. From time t2 to time t3, the voltage value of the bias voltage is maintained at the maximum value Vx which is a constant value. In addition, from time t3 to time t4, the voltage value of the bias voltage decreases linearly from the maximum value Vx to the minimum value Vo at the decrease rate corresponding to the increase rate from time t1 to time t2. Then, from time t4 to time t5, the voltage value of the bias voltage is maintained at the minimum value Vo which is a constant value.

The current value of the charging/discharging current Iapd based on the inter-terminal capacitance Capd of the APD 20 is a current value obtained by differentiating the bias voltage with respect to time. Therefore, the charging/discharging current Iapd has a current waveform shown as “Capd charging/discharging current waveform” in FIG.

On the other hand, the adjustment voltage generator 31 generates an adjustment voltage that changes with time in the opposite direction to the bias voltage. That is, the voltage value of the adjustment voltage decreases linearly from the maximum value Vr1 to the minimum value Vr2 from the time point t1 when the emitting section 11 emits the emitted light OL as a starting point. From time t2 to time t3, the voltage value of the bias voltage is maintained at the minimum value Vr2 which is a constant value. Further, from time t3 to time t4, the voltage value of the adjustment voltage linearly increases from the minimum value Vr2 to the maximum value Vr1 at an increase rate corresponding to the decrease rate from time t1 to time t2. Then, from time t4 to time t5, the voltage value of the adjustment voltage is maintained at the maximum value Vr1 which is a constant value.

The adjustment voltage is converted into an adjustment current as a charging/discharging current by the adjustment capacitor 30, and is supplied to the input terminal of the output unit 22. The current value of the charging/discharging current Icrev by the adjusting capacitor 30 is a current value obtained by differentiating the adjusting voltage with respect to time. Therefore, the charging/discharging current Icrev has a current waveform shown as "Crev charging/discharging current waveform" in FIG.

In this way, the adjustment current has a current waveform that cancels the charge/discharge current Iapd based on the inter-terminal capacitance Capd of the APD 20. Therefore, of the current supplied to the output unit 22, it is possible to cancel the charge/discharge current Iapd based on the inter-terminal capacitance Capd of the APD 20.

FIG. 7 is a time chart showing the waveform of the current supplied to the output unit 22 of the present embodiment and the voltage waveform obtained by IV converting the current in the output unit 22.

Of the current supplied to the output unit 22 of the present embodiment, the current component of the charge/discharge current Iapd based on the inter-terminal capacitance Capd of the APD 20 is canceled by the adjustment current. Therefore, in the present embodiment, the state in which the current supplied to the output unit 22 exceeds the dynamic range does not occur due to the increase in the current value corresponding to the charge/discharge current Iapd.

Therefore, even if the upper limit of the dynamic range of the IV conversion is set lower than the current value of the charging/discharging current Iapd, it is supplied to the output unit 22 as shown in FIG. 7 as “current waveform of this embodiment”. The current can be contained within the dynamic range current range −DA to DA. If the current supplied to the output unit 22 falls within the dynamic range of the IV conversion, the voltage subjected to the IV conversion by the output unit 22 collapses up and down like the voltage waveform of the comparative example (see FIG. 4). It does not have such a voltage waveform. That is, as shown as "voltage waveform of this embodiment" in FIG. 7, the output unit 22 can perform I-V conversion of the entire current range of the supplied current.

Therefore, according to the distance measuring apparatus of the present embodiment, the peak of the light receiving signal RS output from the output unit 22 is detected without widening the dynamic range of the IV conversion, and the light receiving timing required for calculating the distance is detected. Information can be obtained.

The specific circuit configurations of the bias voltage application unit 21 and the adjustment voltage generation unit 31 are not limited to those shown in FIG. For example, the bias voltage and the adjustment voltage can be configured to be generated by a common differential amplifier.

FIG. 8 is a circuit diagram showing a light receiving unit 12 as a modified example having such a configuration. The light receiving unit 12 of the modified example includes a voltage generation unit 40 having the functions of the bias voltage application unit 21 and the adjustment voltage generation unit 31.

The voltage generation unit 40 includes a differential amplifier 41, a resistance element 42, a resistance element 43, a resistance element 44, and a resistance element 45 in addition to the capacitor 24 and the resistance element 25.

The inverting input terminal of the differential amplifier 41 is connected (eg, grounded) to a predetermined potential via the resistance element 42. The non-inverting input terminal of the differential amplifier 41 is connected to the AC power supply AS via the resistance element 44. The inverting output terminal and the inverting input terminal of the differential amplifier 41 are connected via a resistance element 43 as a feedback resistance. The non-inverting output terminal and the non-inverting input terminal of the differential amplifier 41 are connected via a resistance element 45 as a feedback resistor.

The bias voltage is generated based on the voltage output from the inverting output terminal of the differential amplifier 41 and the DC voltage output from the DC power supply DS. On the other hand, the adjustment voltage is generated by the voltage output from the non-inverting output terminal of the differential amplifier 41. The voltage output from the inverting input terminal and the voltage output from the non-inverting output terminal of the differential amplifier 41 both have voltage waveforms corresponding to the AC voltage supplied from the AC power supply AS, and signals in opposite directions. It has a waveform. Therefore, the voltage generator 40 can generate the bias voltage and the adjustment voltage having the same waveform as that shown in FIG.

Note that the embodiment of the present invention is not limited to the one shown in the above example. For example, in the above embodiment, the case where the adjustment capacitor 30 has a capacitance value equivalent to the inter-terminal capacitance Capd of the APD 20 has been described as an example. However, the capacitance value of the adjustment capacitor 30 may be different from the inter-terminal capacitance Capd of the APD 20. The adjustment capacitor 30 can adjust the current supplied to the output unit 22 based on the adjustment voltage generated by the adjustment voltage generation unit 31 at least to the level not exceeding the dynamic range of the IV conversion of the output unit 22. It only has to have a capacity value capable of generating a charge/discharge current.

Further, in the above-described embodiment, the case where the voltage value of the bias voltage is raised in a linear function according to the elapsed time after the emitted light OL is emitted has been described as an example. However, the manner of increasing the voltage value of the bias voltage is not limited to this. For example, the voltage value of the bias voltage may be increased quadratically while increasing the increase rate with the lapse of time after the emission light OL is emitted. Similarly, the adjustment voltage may be changed in a quadratic function according to the increase in the voltage value of the bias voltage.

Further, the specific circuit configurations of the bias voltage application section and the adjustment voltage generation section are not limited to those shown in each of the above embodiments, and may increase or decrease according to the elapsed time after the emission light OL is emitted. It suffices that the bias voltage and the adjustment voltage can be generated.

Further, in the above-described embodiment, the example in which the voltage value of the bias voltage is increased from the time t1 when the emitting unit 11 emits the emitted light OL has been described. However, the starting point is not limited to this, and the rising of the voltage value of the bias voltage may be started after a predetermined period from time t1. For example, immediately after the emitted light OL is emitted, the voltage value of the bias voltage is increased during the period in which the reflected light RL reflected by the optical system components inside the distance measuring apparatus 100 is expected to enter the light receiving unit 12. It is also possible to adopt a configuration that does not allow it. With such a configuration, it is possible to more reliably prevent the saturation of the APD 20 due to receiving the reflected light RL from the inside of the distance measuring device 100.

Further, in the above embodiment, an example in which the distance calculation unit calculates the distance based on the TOF method has been described, but the present invention can also be applied to a distance measuring device that calculates the distance based on the phase difference method. is there.

In addition, the series of processes described in the above embodiments can be performed by computer processes according to a program stored in a recording medium such as a ROM.

100 distance measuring device 11 emitting part 11A laser light source 11B laser emission driving part 12 light receiving part 12A light receiving element 12B light receiving signal detecting part 13 control part 14 distance calculating part 21 bias voltage applying part 22 output part 23 operational amplifier 24 capacitor 25 resistance element 26 operational amplifier 27 resistance element 30 adjustment capacitor 31 adjustment voltage generation unit 32 operational amplifier 33, 34 resistance element 34 resistance element 41 differential amplifier 42, 43, 44, 45 resistance element

Claims (9)

A light source that emits light toward an object,
A photoelectric conversion element that receives light reflected by an object and outputs a current according to the received light,
A first voltage applying section for gradually increasing a voltage value to apply a first voltage to the photoelectric conversion element;
A converter that converts the current output from the photoelectric conversion element into a voltage and outputs the voltage.
A capacitor having a capacitance based on a capacitance between terminals of the photoelectric conversion element and having one end connected to an input of the conversion unit, and a second voltage having a phase opposite to the first voltage is applied to the other end of the capacitor. An adjusting circuit having a second voltage applying section,
A light emitting and receiving device comprising: The first voltage applying unit applies a voltage whose voltage value increases with time as a first voltage to the photoelectric conversion element over a predetermined period after the light is emitted from the light source,
The adjustment circuit applies a voltage whose voltage value decreases at a decrease rate corresponding to an increase rate of the voltage value of the first voltage to the other end of the capacitor as the second voltage. The light emitting and receiving device described. The light emitting and receiving device according to claim 1, wherein the first voltage application unit monotonically increases the voltage value of the first voltage for a predetermined period after light is emitted from the light source. apparatus. The projection unit according to claim 1, wherein the first voltage application unit increases the voltage value of the first voltage while increasing the increase rate with the lapse of time after the light is emitted from the light source. Light receiving device. The first voltage applying unit,
A buffer connected to an AC power supply,
A biasing capacitor connected between the output end of the buffer and one end of the photoelectric conversion element,
Including
The light projecting/receiving device according to claim 1, wherein the second voltage applying unit includes an inverting amplifier connected to the AC power supply. One of a pair of input terminals is connected to an AC power supply, the other has a differential amplifier connected to a predetermined potential,
The first voltage application unit includes a bias capacitor connected between one of a pair of output ends of the differential amplifier and one end of the photoelectric conversion element,
The capacitor of the adjustment circuit is connected between the other of the pair of output ends of the differential amplifier and the input end of the conversion unit. The light emitting and receiving device according to. A light source, a photoelectric conversion element, a first voltage application section that applies a first voltage to the photoelectric conversion element, a conversion section that converts a current into a voltage and outputs the voltage, and a capacitance based on the inter-terminal capacitance of the photoelectric conversion element. And a second voltage applying section for applying a second voltage to the other end of the capacitor, and a light emitting/receiving method performed by a light emitting/receiving apparatus. hand,
The light source emits light toward an object,
The first voltage applying section gradually increasing the voltage value to apply the first voltage to the photoelectric conversion element;
The photoelectric conversion element receives the light reflected by an object, and outputs a current according to the received light,
The second voltage applying section applies the second voltage having a phase opposite to that of the first voltage to the other end of the capacitor;
A step of converting the current output from the photoelectric conversion element and the current output from the capacitor into a voltage and outputting the voltage;
A light emitting and receiving method comprising: A light source, a photoelectric conversion element, a first voltage application section that applies a first voltage to the photoelectric conversion element, a conversion section that converts a current into a voltage and outputs the voltage, and a capacitance based on the inter-terminal capacitance of the photoelectric conversion element. A computer having one end connected to the input of the conversion unit and a second voltage application unit applying a second voltage to the other end of the capacitor,
Controlling the light source to emit light toward an object;
Controlling the first voltage applying section to gradually increase the voltage value and apply the first voltage to the photoelectric conversion element;
Receiving the light reflected by the object, controlling the photoelectric conversion element so as to output a current corresponding to the received light, and
Controlling the second voltage applying section to apply the second voltage having a phase opposite to the first voltage to the other end of the capacitor;
Controlling the converter to convert the current output from the photoelectric conversion element and the current output from the capacitor into a voltage and output the voltage;
A program characterized by causing to execute. A light source, a photoelectric conversion element, a first voltage application section that applies a first voltage to the photoelectric conversion element, a conversion section that converts a current into a voltage and outputs the voltage, and a capacitance based on the inter-terminal capacitance of the photoelectric conversion element. A computer having one end connected to the input of the conversion unit and a second voltage application unit applying a second voltage to the other end of the capacitor,
Controlling the light source to emit light toward an object;
Controlling the first voltage applying section to gradually increase the voltage value and apply the first voltage to the photoelectric conversion element;
Receiving the light reflected by the object, controlling the photoelectric conversion element to output a current according to the received light, and
Controlling the second voltage applying section to apply the second voltage having a phase opposite to the first voltage to the other end of the capacitor;
Controlling the converter to convert the current output from the photoelectric conversion element and the current output from the capacitor into a voltage and output the voltage;
A recording medium for recording a program for executing.

Images