JP2015117970A - Radar equipment - Google Patents

Abstract

A radar device includes a light source, a pixel, and a light detection control unit. The light source 2 is installed inside the radar apparatus 1 and emits light. The pixel 21 includes a SPAD (Single Photon Avalanche Diode) installed inside the radar apparatus 1 and detects the light reflected by the object by SPAD. The light detection control unit 24 starts the SPAD operation after the timing when the internally scattered light generated by the light emitted from the light source 2 being reflected inside the radar apparatus 1 enters the SPAD.
[Selection] Figure 2

Description

  The present invention relates to a radar apparatus that obtains information on an object that reflects light by irradiating light and receiving reflected light.

  Conventionally, when irradiation light passes through a radar apparatus in a radar apparatus that obtains information (for example, a distance to the object) about an object that reflects light by irradiating light and detecting light reflected by the object. Is known that employs a coaxial optical system in which the optical axis when the reflected light passes through the radar apparatus and coincides with the optical axis (see, for example, Non-Patent Document 1).

  In the radar apparatus described in Non-Patent Document 1, a SPAD (Single Photon Avalanche Diode) is used as a light receiving element, and a detection signal can be output by the incidence of one photon.

19th Image Sensing Symposium OS2-03

  However, in a radar apparatus that employs a coaxial optical system, the distance from the radar apparatus to a nearby object is measured due to the influence of internally scattered light that is generated when reflected light passing through the radar apparatus is reflected inside the radar apparatus. There was a problem that I could not.

  The present invention has been made in view of these problems, and an object of the present invention is to extend a range in which the distance of an object can be measured in the vicinity of a radar apparatus in a radar apparatus using SPAD.

The radar apparatus according to the present invention, which has been made to achieve the above object, includes light irradiation means, reflected light detection means, and operation start means.
In the radar apparatus of the present invention, first, light irradiation means installed inside the radar apparatus irradiates light. And the reflected light detection means provided with SPAD (Single Photon Avalanche Diode) installed in the inside of the said radar apparatus detects the light reflected by the object by SPAD. Further, the operation starting means starts the SPAD operation after the timing at which the internally scattered light generated by the light irradiated by the light irradiating means being reflected inside the radar apparatus enters the SPAD.

  In the radar apparatus configured as described above, the light reflected by the object is detected by SPAD. The SPAD operates in a state where a reverse bias voltage larger than the breakdown voltage is applied, and light is incident on the SPAD to generate an avalanche current.

  When the avalanche current is generated, as shown in FIG. 6, the voltage between the anode and the cathode in the SPAD decreases, and when the voltage between the terminals becomes less than the breakdown voltage, the avalanche current stops. Further, after the avalanche current is generated, an after pulse may be generated due to charges trapped in the SPAD for several tens to several hundreds of ns. Therefore, the voltage applied to the SPAD is rapidly increased. It cannot be recharged. For this reason, the period from the generation of the avalanche current due to the internally scattered light in SPAD to the end of the recharge is a non-detectable period in which the light reflected by the object cannot be detected by the radar apparatus. This makes it impossible to detect an object located near the radar device.

  Note that the after-pulse is generated by trapping a charge generated when a SPAD responds when light enters the SPAD, and then releasing the charge by thermal excitation or the like. Is a phenomenon in which SPAD behaves as if incident, and causes noise.

  On the other hand, in the radar apparatus of the present invention, the SPAD operation is started after the timing when the internally scattered light enters the SPAD. As a result, the SPAD of the reflected light detection means does not generate an avalanche current even when internally scattered light is incident. For this reason, in the radar apparatus of the present invention, there is no period during which the avalanche current is generated in the non-detectable period.

  Furthermore, in the radar apparatus of the present invention, charge is not trapped in the SPAD due to the avalanche current, and generation of after pulses can be suppressed. For this reason, the voltage applied to the SPAD can be increased and recharged faster than when an avalanche current is generated. That is, during the non-detectable period, the recharging period can be shortened.

  As described above, in the radar apparatus of the present invention, the period during which avalanche current is generated does not exist and the period during which recharging is performed is shortened, so that the undetectable period can be shortened. As a result, the range in which the distance of the object can be measured in the vicinity of the radar apparatus can be expanded by the amount that the non-detectable period can be shortened.

It is a figure which shows the structure and operation | movement of the radar apparatus 1 of 1st Embodiment. It is a block diagram which shows the structure of the radar apparatus 1 of 1st Embodiment. 2 is a plan view showing a schematic configuration of a pixel 21. FIG. FIG. 3 is a circuit diagram illustrating configurations of a light receiving element 31 and a lead-out circuit 32 according to the first embodiment. It is a timing chart which shows the operation start control of SPAD in 1st Embodiment. It is a figure which shows the voltage between terminals for a recharge to complete | finish after avalanche current generate | occur | produces by SPAD. It is a circuit diagram which shows the structure of the light receiving element 31 and lead-out circuit 32 of 2nd Embodiment. It is a timing chart which shows the operation start control of SPAD in 2nd Embodiment. It is a block diagram which shows the structure of the radar apparatus 1 of 3rd Embodiment. It is a timing chart which shows the operation start control of SPAD in 3rd Embodiment. It is a figure which shows the structure and operation | movement of the radar apparatus 1 of 4th Embodiment. It is a block diagram which shows the structure of the radar apparatus 1 of 5th Embodiment. It is a top view which shows schematic structure of the pixel 21 of 5th Embodiment. It is a circuit diagram which shows the structure of the pixel 21 of 5th Embodiment. It is a circuit diagram which shows the structure of the light receiving element 31 and the lead-out circuit 32 of 6th Embodiment. It is a timing chart which shows the operation start control of SPAD in 6th Embodiment.

(First embodiment)
A first embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the radar apparatus 1 includes a light source 2, a collimating lens 3, a polarizing beam splitter 4, a quarter wavelength plate 5, an optical scanning unit 6, a light receiving lens 7, a light detector 8, and components thereof. And a housing 9 for storing the.

The light source 2 is composed of, for example, a semiconductor laser diode and irradiates linearly polarized pulsed laser light as a radar wave.
The collimating lens 3 converts the laser light emitted from the light source 2 into parallel light, and irradiates it toward the polarization beam splitter 4.

  The polarization beam splitter 4 has a function of transmitting a component having a predetermined polarization direction in the laser light incident on the polarization beam splitter 4 and reflecting a component having a polarization direction other than the predetermined polarization direction.

The polarization beam splitter 4 is arranged so that the predetermined polarization direction matches the polarization direction of the laser light emitted from the light source 2.
The quarter-wave plate 5 has a function of converting linearly polarized light into circularly polarized light and converting circularly polarized light into linearly polarized light, and is disposed between the polarizing beam splitter 4 and the optical scanning unit 6.

  The optical scanning unit 6 oscillates a mirror 61 that reflects laser light around a rotation shaft 62 provided on the mirror 61, thereby scanning the laser light incident from the quarter-wave plate 5 in advance. The scanning angle range R1 is used. The optical scanning unit 6 is configured by a micro electro mechanical system (MEMS) or a polygon mirror.

The light receiving lens 7 guides the laser beam incident from the side of the optical scanning unit 6 and reflected by the polarization beam splitter 4 to the photodetector 8.
The photodetector 8 detects the laser light incident from the light receiving lens 7.

Next, a method for detecting an object reflecting a radar wave in the radar apparatus 1 configured as described above will be described.
First, the laser light emitted from the light source 2 is converted into parallel light by the collimating lens 3, passes through the polarization beam splitter 4, and further passes through the quarter wavelength plate 5. As a result, the laser light is converted from linearly polarized light to circularly polarized light and reaches the optical scanning unit 6 (see the light L1).

Then, the laser beam that has reached the optical scanning unit 6 is reflected by the mirror 61, and is irradiated as a radar wave in a direction corresponding to the scanning angle of the mirror 61 (see the light L2).
Thereafter, when laser light reflected by the object B (hereinafter also referred to as reflected laser light) reaches the optical scanning unit 6 (see the light L3), it is reflected by the mirror 61 and passes through the quarter-wave plate 5 again (see FIG. See light L4). As a result, the reflected laser light is converted from circularly polarized light into linearly polarized light and reaches the polarization beam splitter 4 (see the light L4).

  The polarization direction of the reflected laser light converted into linearly polarized light by the quarter wavelength plate 5 is shifted by 90 ° from the polarization direction of the laser light before being irradiated from the light source 2 and converted into circularly polarized light. For this reason, the reflected laser light that has reached the polarizing beam splitter 4 is reflected by the polarizing beam splitter 4 and irradiated toward the light receiving lens 7 (see the light L5). Thereby, the reflected laser beam reaches the photodetector 8, and the object that reflects the radar wave can be detected.

The radar apparatus 1 further includes a scanning control unit 11 and a processing unit 12 as shown in FIG.
The light source 2 outputs a light emission signal indicating that the laser beam has been irradiated at the timing of irradiation with the pulsed laser beam.

The scanning control unit 11 detects the scanning angle of the optical scanning unit 6 and controls the laser beam scanning by the optical scanning unit 6 based on the detection result.
The processing unit 12 measures the distance to the object that reflected the laser light based on the difference between the time when the light emission signal is input from the light source 2 and the time when the reflected laser light is detected by the photodetector 8. I do.

The photodetector 8 includes a pixel 21, a drive circuit 22, a clutter detection pixel 23, and a light detection control unit 24.
The pixel 21 outputs a detection signal when laser light is incident on its light receiving surface.

As shown in FIG. 3, the pixel 21 includes four light receiving elements 31 and a lead-out circuit (Read Out Circuit) 32 provided corresponding to each of the four light receiving elements 31. Note that the light receiving element 31 of the present embodiment is a SPAD (Single Photon Avalanche Diode). SPAD is an avalanche photodiode that operates in Geiger mode and can detect the incidence of a single photon. Between the anode and the cathode of the SPAD, the reverse bias voltage V _B is applied (see Figure 4). When the reverse bias voltage V _B photons to the light receiving portion 36 of the SPAD state is the breakdown voltage or more is incident, avalanche current generated by SPAD. For this reason, when a photon is incident, the SPAD can output a detection signal indicating that the incident has been detected.

  The lead-out circuit 32 is a circuit that converts a signal output from the light receiving element 31 into a digital pulse signal when laser light enters the light receiving element 31. The circuit configuration of the lead-out circuit 32 will be described later.

  The four light receiving elements 31 are arranged in a two-dimensional matrix so that two light receiving portions 36 are arranged in the column direction and two in the row direction. Further, the four lead-out circuits 32 are arranged so as to be adjacent to the corresponding light receiving element 31 along the row direction D1. However, the lead-out circuit 32 is arranged so that the two light receiving elements 31 are arranged along the row direction D1 between the two lead-out circuits 32 arranged in the same row.

As shown in FIG. 4, the lead-out circuit 32 includes a quench resistor 41, a digital converter 42, an inverter 43, and a buffer 44.
The quench resistor 41 is an N-channel MOSFET (hereinafter referred to as an N-type transistor). The drain of the N-type transistor constituting the quench resistor 41 is connected to the anode of the SPAD constituting the light receiving element 31, and the source is grounded. A quench resistance gate voltage V _QG is applied to the gate of the N-type transistor that functions as the quench resistance 41.

The digital converter 42 includes a resistor 51 and an N-type transistor 52. A power supply voltage V _DD is applied to the drain of the N-type transistor 52 via the resistor 51, and the source is grounded. The gate of the N-type transistor 52 is connected to a connection point CP1 between the anode of the SPAD and the quench resistor 41.

The inverter 43 includes a P-channel MOSFET (hereinafter referred to as a P-type transistor) 53 and an N-type transistor 54. A power supply voltage V _DD is applied to the drain of the P-type transistor 53, and the source is connected to the drain of the N-type transistor 54. The gate of the P-type transistor 53 and the gate of the N-type transistor 54 are connected to a connection point CP2 between the drain of the N-type transistor 52 and the resistor 51. The source of the N-type transistor 54 is grounded.

  The buffer 44 is a circuit for impedance conversion. The input terminal of the buffer 44 is connected to a connection point CP 3 between the source of the P-type transistor 53 and the drain of the N-type transistor 54.

Next, the operation of the lead-out circuit 32 configured as described above will be described.
First, when the reverse bias voltage V _B equal to or higher than the breakdown voltage is applied to the SPAD, the light receiving element 31 becomes operable.

When reflected light enters the light receiving element 31 and an avalanche current is generated, the avalanche current flows through the quench resistor 41, and the voltage at the connection point CP1 increases. When the voltage at the connection point CP1 becomes higher than the on-voltage of the N-type transistor 52, the N-type transistor 52 is turned on, and the voltage at the connection point CP2 changes from the power supply voltage V _DD to 0V.

As a result, the P-type transistor 53 changes from the OFF state to the ON state and the N-type transistor 54 changes from the ON state to the OFF state, so that the voltage at the connection point CP3 changes from 0V to the power supply voltage V _DD .

As a result, the voltage _{VOUT at} the output terminal of the buffer 44 becomes high level.
Thereafter, when the voltage rise at the connection point CP1 continues, the voltage applied between the anode and the cathode of the SPAD becomes smaller than the breakdown voltage, and the avalanche current stops. As a result, the voltage at the connection point CP1 is lowered, the N-type transistor 52 is turned off, and the voltage _{VOUT at} the output terminal of the buffer 44 becomes low level.

  As described above, the lead-out circuit 32 is in a state where the N-type transistor 52 is turned on when the reflected light is incident and the avalanche current is generated, and then the N-type transistor 52 is turned off after the avalanche current is stopped. A digital pulse signal that goes high during the period is output.

2, the drive circuit 22 to each of the light receiving elements 31 constituting the pixels 21, supplies a reverse bias voltage V _B. In accordance with the control signal output from the light detection control unit 24, the drive circuit 22 uses the reverse bias voltage V _B , the detectable voltage V _B1 (see FIG. 5) at which the pixel 21 can output the detection signal, and the pixel 21 can be set to any one of the undetectable voltage V _B2 (see FIG. 5) from which a detection signal cannot be output.

Further, the drive circuit 22 supplies a quench resistance gate voltage V _QG to each of the quench resistances 41 of the lead-out circuit 32 constituting the pixel 21. In accordance with the control signal output from the light detection control unit 24, the drive circuit 22 uses the quench resistor gate voltage V _QG , the quench voltage V _QCH that causes the N-type transistor to act as a quench resistor, and the recharge voltage V when recharging SPAD. It can be set to any one of _RCG .

  The clutter detection pixel 23 is SPAD like the pixel 21, and a reverse bias voltage higher than the breakdown voltage is constantly applied. For this reason, when a photon enters the clutter detection pixel 23, the clutter detection pixel 23 outputs a detection signal indicating that the incidence has been detected.

Light detection control unit 24 receives the detection signal from the clutter detection pixels 23, on the basis of this detection signal, the drive circuit 22 controls the reverse bias voltage V _B and quench resistance gate voltage V _QG supplied.

Specifically, as shown in FIG. 5, when the light source 2 emits pulsed laser light (see time t01), the pulsed laser light is reflected in the housing 9, and internally scattered light (hereinafter referred to as clutter). Occurs (see time t02). Then, when the clutter enters the clutter detection pixel 23, the clutter detection pixel 23 detects the clutter. When the detection signal is input from the clutter detection pixel 23, the light detection controller 24 outputs an operation start signal for starting the operation of SPAD to the drive circuit 22 as the control signal. Thus, the drive circuit 22, a reverse bias voltage _{V B,} the breakdown from the voltage _{V BRK} lower undetectable voltage _{V B2,} changing to a higher than the breakdown voltage _{V BRK} detectable voltage _{V B1} (see time t03). Further driving circuit 22 changes the quench resistance gate voltage _{V QG} from the quench voltage _{V QCH} to recharge voltage _{V RCG} (see time t03).

As a result, the inter-terminal voltage V _SPAD between the anode and the cathode in the SPAD of the light receiving element 31 rises from the undetectable voltage V _B2 to the detectable voltage V _B1 (see times t03 to t04). When the SPAD terminal voltage V _SPAD reaches the detectable voltage V _B1 , the photodetection control unit 24 outputs a recharge end signal for ending the recharge to the drive circuit 22 as the control signal. As a result, the drive circuit 22 changes the quench resistance gate voltage V _QG from the recharge voltage V _RCG to the quench voltage V _QCH (see time t04).

In addition, the light detection control unit 24 outputs an operation stop signal for stopping the operation of the SPAD to the drive circuit 22 as the control signal before the light source 2 next irradiates the pulse laser beam. As a result, the drive circuit 22 changes the reverse bias voltage V _B from the detectable voltage V _B1 to the undetectable voltage V _B2 (not shown).

  In the radar apparatus 1 configured as described above, first, the light source 2 installed inside the radar apparatus 1 irradiates pulse laser light. Then, the pixel 21 provided with SPAD installed inside the radar apparatus 1 detects the laser beam reflected by the object by SPAD. Further, the light detection control unit 24 starts the SPAD operation after the timing when the clutter enters the SPAD.

In the radar apparatus 1 configured as described above, the laser beam reflected by the object is detected by SPAD. SPAD operates in a state in which a reverse bias voltage V _B greater than the breakdown voltage V _BRK is applied, and light enters the SPAD to generate an avalanche current.

When the avalanche current is generated, as shown in FIG. 6, the inter-terminal voltage V _SPAD between the anode and the cathode in the _SPAD decreases, and when the inter-terminal voltage V _SPAD becomes less than the breakdown voltage V _BRK , the avalanche current stops. . Further, after the avalanche current is generated, an after pulse may be generated due to charges trapped in the SPAD for several tens to several hundreds of ns. Therefore, the voltage applied to the SPAD is rapidly increased. It cannot be recharged. For this reason, the period from the generation of an avalanche current due to clutter in SPAD to the end of recharging is a dead time in which the light reflected by the object cannot be detected by the radar apparatus. This makes it impossible to detect an object located near the radar device.

  Note that the after-pulse is generated by trapping a charge generated when a SPAD responds when light enters the SPAD, and then releasing the charge by thermal excitation or the like. Is a phenomenon in which SPAD behaves as if incident, and causes noise.

  On the other hand, the radar apparatus 1 starts the SPAD operation after the timing when the clutter enters the SPAD. Thereby, the SPAD in the pixel 21 does not generate an avalanche current even when the clutter is incident. For this reason, in the radar apparatus 1, there is no period during which the avalanche current is generated in the dead time.

  Furthermore, in the radar apparatus 1, electric charges are not trapped in the SPAD due to the avalanche current, and generation of after pulses can be suppressed. For this reason, the voltage applied to the SPAD can be increased and recharged faster than when an avalanche current is generated. That is, the recharging period of the dead time can be shortened.

  As described above, in the radar apparatus 1, the dead time can be shortened by the absence of a period during which the avalanche current is generated and the shortening of the recharging period. As a result, the range in which the distance of the object can be measured in the vicinity of the radar apparatus 1 can be expanded by the amount that the dead time can be shortened.

  The radar apparatus 1 also includes clutter detection pixels 23 that detect clutter. Then, the light detection control unit 24 starts the SPAD operation after the clutter detection pixel 23 detects the clutter.

  For this reason, the light detection control unit 24 can perform control such that the SPAD operation is started immediately after the clutter detection pixel 23 detects clutter and immediately after the clutter detection pixel 23 no longer detects clutter. . As a result, it is possible to shorten the period from the end of the clutter incident on the SPAD in the pixel 21 to the start of the SPAD operation, and to avoid an increase in the dead time.

The photodetection control unit 24 controls the reverse bias voltage _{V B} applied to the SPAD in the pixel 21, to vary the magnitude of the reverse bias voltage _{V B} from less than the breakdown voltage _{V BRK} higher than the breakdown voltage _{V BRK} As a result, the operation of SPAD in the pixel 21 is started.

To control the reverse bias voltage V _B is a circuit for changing the magnitude of the reverse bias voltage V _B may be disposed outside the pixel 21. For this reason, the operation of SPAD in the pixel 21 can be controlled without reducing the light receiving area of the light receiving element 31 disposed in the pixel 21.

  The radar apparatus 1 also includes an N-type transistor that functions as a SPAD quench resistor 41 in the pixel 21. Then, the photodetection control unit 24 increases the voltage applied to the gate of the quench resistor 41 when starting the SPAD operation than before starting the SPAD operation.

  By increasing the voltage applied to the gate of the quench resistor 41, the resistance value of the quench resistor 41 can be decreased, and the amount of current flowing through the SPAD can be increased. Thereby, the time for recharging SPAD can be shortened, and the dead time can be further shortened.

  In addition, a light detection control unit 24 that starts the SPAD operation is disposed outside the pixel 21. For this reason, the operation of SPAD in the pixel 21 can be controlled without reducing the light receiving area of the light receiving element 31 disposed in the pixel 21.

  In the embodiment described above, the light source 2 is the light irradiation means in the present invention, the pixel 21 is the reflected light detection means in the present invention, the light detection control unit 24 is the operation start means in the present invention, and the clutter detection pixel 23 is in the present invention. It is an internal scattered light detection means.

(Second Embodiment)
A second embodiment of the present invention will be described below with reference to the drawings. In the second embodiment, parts different from the first embodiment will be described.

The radar apparatus 1 of the second embodiment is the same as that of the first embodiment except that the pixel 21, the drive circuit 22, and the light detection control unit 24 of the photodetector 8 are changed.
First, the pixel 21 is the same as that of the first embodiment except that the configuration of the lead-out circuit 32 is changed. Specifically, as shown in FIG. 7, the second embodiment is the same as the first embodiment except that selectors 45 and 55 are added.

The selector 45 is an N-type transistor. The drain of the N-type transistor constituting the selector 45 is connected to the source of the N-type transistor constituting the quench resistor 41, and the source is grounded. A selector voltage V _SEL (described later) is applied to the gate of the N-type transistor.

The selector 55 is a P-type transistor. The drain of the P-type transistor constituting the selector 55 is connected to the node CP1 of the SPAD anode, and the source voltage V _DD is applied to the source. A selector voltage _VSEL is applied to the gate of the P-type transistor.

Next, in addition to the reverse bias voltage V _B and the quench resistor gate voltage V _QG , the drive circuit 22 applies a selector voltage V _SEL to each of the selectors 45 and 55 of the lead-out circuit 32 constituting the pixel 21. Except for the point to supply, it is the same as 1st Embodiment. The drive circuit 22 always supplies the detectable voltage V _B1 as the reverse bias voltage V _B. The drive circuit 22 in accordance with a control signal outputted from the photodetection control unit 24, the selector voltage _{V SEL,} and the ON voltage _{V ON} of the selector 55 is turned off, operating the SPAD with a selector 45 to the ON state, The selector 45 is turned off and the selector 55 is turned on, so that the selector 45 can be set to any one of the off voltages V _OFF for stopping the SPAD operation.

The light detection control unit 24 is the same as that in the first embodiment except that the selector voltage V _SEL is controlled instead of the reverse bias voltage V _B.
Specifically, as shown in FIG. 8, when the light source 2 emits pulsed laser light (see time t11), the pulsed laser light is reflected in the housing 9 to generate clutter (see time t12). ). Then, when the clutter enters the clutter detection pixel 23, the clutter detection pixel 23 detects the clutter. When the detection signal is input from the clutter detection pixel 23, the light detection controller 24 outputs an operation start signal for starting the operation of SPAD to the drive circuit 22 as the control signal. Accordingly, the drive circuit 22 changes the selector voltage V _SEL from the off voltage V _OFF to the on voltage V _ON (see time t13). Further driving circuit 22 changes the quench resistance gate voltage _{V QG} from the quench voltage _{V QCH} to recharge voltage _{V RCG} (see time t13).

Accordingly, the terminal voltage _{V SPAD} the light receiving element 31, the lower the breakdown voltage _{V BRK} voltage rises to a higher than the breakdown voltage _{V BRK} detectable voltage _{V B} (see time t13 to t14). When the SPAD terminal voltage V _SPAD reaches the detectable voltage V _B , the photodetection control unit 24 outputs a recharge end signal for ending the recharge to the drive circuit 22 as the control signal. As a result, the drive circuit 22 changes the quench resistance gate voltage V _QG from the recharge voltage V _RCG to the quench voltage V _QCH (see time t14).

In addition, the light detection control unit 24 outputs an operation stop signal for stopping the operation of the SPAD to the drive circuit 22 as the control signal before the light source 2 next irradiates the pulse laser beam. As a result, the drive circuit 22 changes the selector voltage V _SEL from the ON voltage V _ON to the OFF voltage V _OFF (not shown).

In the radar apparatus 1 configured as described above, the light detection control unit 24 controls the selectors 45 and 55 connected to the SPAD in the pixel 21 to change the selector 45 from the off state to the on state. by changing to the oFF state 55 from the on state, the magnitude of the terminal voltage _{V SPAD} of the light receiving element 31 by changing the breakdown voltage _{V BRK} or from less than the breakdown voltage _{V BRK,} the operation of the SPAD in the pixel 21 Let it begin.

For this reason, the operation of the SPAD in the pixel 21 can be controlled by a simple control of switching the on and off states of the selectors 45 and 55.
In the embodiment described above, the selectors 45 and 55 are switches in the present invention.

(Third embodiment)
A third embodiment of the present invention will be described below with reference to the drawings. In the third embodiment, parts different from the first embodiment will be described.

As shown in FIG. 9, the radar apparatus 1 according to the third embodiment is the same as the first embodiment except that the photodetector 8 is changed.
The photodetector 8 is the same as that of the first embodiment except that the clutter detection pixel 23 is omitted and the light detection control unit 24 is changed.

The light detection control unit 24 receives a light emission signal from the light source 2. Then, as shown in FIG. 10, the light detection control unit 24 reverses after a delay time set in advance so that the clutter is incident on the clutter detection pixel 23 after the light emission signal is input. The bias voltage V _B is changed from the undetectable voltage V _B2 to the detectable voltage V _B1 .

The light detection control unit 24 sets the delay time by delaying the input light emission signal with a delay element.
In the radar apparatus 1 configured as described above, the light detection control unit 24 acquires a light emission signal output at the timing when the light source 2 emits the pulsed laser light, and then a preset delay time has elapsed. The SPAD operation in the pixel 21 is started.

As a result, the clutter detection pixel 23 for detecting the clutter becomes unnecessary, and the configuration of the radar apparatus 1 can be simplified.
(Fourth embodiment)
A fourth embodiment of the present invention will be described below with reference to the drawings. In the fourth embodiment, parts different from the first embodiment will be described.

As shown in FIG. 11, the radar device 1 according to the fourth embodiment is different from the first embodiment in that the reflector device 70 is provided inside the housing 9.
The reflection plate 70 is installed around an opening OP formed in the housing 9 in order to irradiate laser light to the outside of the radar apparatus 1.

The radar apparatus 1 emits pulse laser light having a diameter larger than the diameter of the opening OP from the light source 2.
In the radar apparatus 1 configured as described above, a part of the pulsed laser light scanned by the optical scanning unit 6 and irradiated toward the opening OP is reflected by the reflecting plate 70, and clutter is generated. Thereby, the probability that the clutter detection pixel 23 detects the clutter can be improved.

(Fifth embodiment)
A fifth embodiment of the present invention will be described below with reference to the drawings. In the fifth embodiment, parts different from the first embodiment will be described.

  As shown in FIG. 12, the radar apparatus 1 according to the fifth embodiment is different from the first embodiment in that the drive circuit 22, the clutter detection pixel 23, and the light detection control unit 24 are omitted from the photodetector 8. .

  Further, as shown in FIG. 13, the pixel 21 in the fifth embodiment is different from the first embodiment in that it includes three light receiving elements 31 and one clutter detection element 80. The clutter detection element 80 is a SPAD.

  As shown in FIG. 14, the pixel 21 includes a light receiving element 31, a clutter detection element 80, a quench resistor 41, selectors 45 and 55, a D-type flip-flop circuit 91, a quench resistor 92, and a lead-out. Circuits 93 and 94 are provided. Note that three light receiving elements 31, quench resistors 41, selectors 45 and 55, and lead-out circuits 93 are provided for each pixel 21 (two of the three are shown in FIG. 14).

Between the anode and the cathode of the light receiving element 31 and the clutter detection element 80, the reverse bias voltage V _B is applied. Further, the anode of the SPAD constituting the light receiving element 31 is grounded via the quench resistor 41 and the selector 45. Further, the anode of the SPAD constituting the clutter detection element 80 is grounded via the quench resistor 92. The quench resistor 92 is an N-type transistor like the quench resistor 41.

The D-type flip-flop circuit 91 includes an input terminal D, a clock terminal CLK, an output terminal Q, and a reset terminal CLR. A power supply voltage V _DD is applied to the input terminal D. The clock terminal CLK is connected to a connection point CP11 between the SPAD anode and the quench resistor 92. The output terminal Q is connected to the gates of the selectors 45 and 55.

  For this reason, when the avalanche current is generated in the clutter detection element 80 and the avalanche current flows through the quench resistor 92 and the voltage at the connection point CP11 becomes high level, the D-type flip-flop circuit 91 starts from the output terminal Q. Start signal output. As a result, the selector 45 changes from the off state to the on state, and the selector 55 changes from the on state to the off state, so that the SPAD constituting the light receiving element 31 starts its operation.

  The signal output from the output terminal Q is input to the reset terminal CLR via a delay circuit (not shown). The delay circuit delays the input signal by a preset delay time and outputs the delayed signal. Therefore, a high level signal is input to the reset terminal CLR after the delay time has elapsed since the high level signal was output from the output terminal Q. When a high level signal is input to the reset terminal CLR, the D-type flip-flop circuit 91 stops outputting the high level signal. That is, when an avalanche current is generated in the clutter detection element 80, the D-type flip-flop circuit 91 outputs a pulse signal that is continuously at a high level for the delay time. The delay time is set so that the output of the pulse signal ends before the light source 2 next irradiates the pulse laser beam.

  The lead-out circuits 93 and 94 are configured by deleting the quench resistor 41 and the selectors 45 and 55 from the lead-out circuit 32. That is, the lead-out circuits 93 and 94 include a digital converter 42, an inverter 43, and a buffer 44.

  The input terminal of the lead-out circuit 93 is connected to the anode of the SPAD that constitutes the light receiving element 31, and the output terminal is connected to the processing unit 12. For this reason, the lead-out circuit 93 outputs a digital pulse signal that becomes a high level to the processing unit 12 while the avalanche current is generated in the corresponding light receiving element 31.

  The input terminal of the lead-out circuit 94 is connected to the anode of the SPAD constituting the clutter detection element 80, and the output terminal is connected to the processing unit 12. Therefore, the lead-out circuit 94 outputs to the processing unit 12 a digital pulse signal that becomes high level while the avalanche current is generated in the clutter detection element 80.

  The radar apparatus 1 configured as described above includes a clutter detection element 80. The D-type flip-flop circuit 91 starts the operation of the SPAD constituting the light receiving element 31 after the clutter detection element 80 detects the clutter.

  The radar apparatus 1 performs processing for measuring the distance to the object based on the difference between the time when the light emission signal is input from the light source 2 and the time when the light receiving element 31 detects the reflected laser light. Is provided. Then, the processing unit 12 further inputs a signal output when the clutter detection element 80 detects laser light through the lead-out circuit 94 and performs processing for measuring the distance to the object.

  Thus, the radar apparatus 1 can use the clutter detection element 80 as an element for detecting the reflected laser beam reflected by the object after the clutter detection element 80 detects the clutter. Detection efficiency can be improved.

  In the embodiment described above, the D-type flip-flop circuit 91 is the operation start means in the present invention, the clutter detection element 80 is the internal scattered light detection means in the present invention, and the processing unit 12 is the information processing means in the present invention.

(Sixth embodiment)
The sixth embodiment of the present invention will be described below with reference to the drawings. In the sixth embodiment, parts different from the first embodiment will be described.

As shown in FIG. 15, the radar apparatus 1 according to the sixth embodiment is different from the first embodiment in that a quench resistor 46 is added to the lead-out circuit 32.
The quench resistor 46 is an N-type transistor. The drain of the N-type transistor constituting the quench resistor 46 is connected to the anode of the SPAD constituting the light receiving element 31, and the source is grounded. A quench resistance gate voltage V _QG2 is applied to the gate of the N-type transistor that functions as the quench resistance 46.

Further, the drive circuit 22 is different from the first embodiment in that the quench resistance gate voltage V _QG1 is supplied to each of the quench resistors 41 of the lead-out circuit 32 constituting the pixel 21. The drive circuit 22 is configured such that the quench resistor gate voltage V _QG1 can be set to a constant quench voltage V _QCH1 that causes the N-type transistor to act as a quench resistor.

Further, the drive circuit 22 is different from the first embodiment in that the quench resistance gate voltage V _QG2 is supplied to each of the quench resistors 46 of the lead-out circuit 32 constituting the pixel 21. Drive circuit 22 in accordance with a control signal output from the light detection control unit 24, the quench resistance gate voltage V _QG2, quench voltage V _QCH2 exerting N-type transistor as a quench-resistant, clear that the N-type transistor in the OFF state The voltage V _OFF2 can be set to any one.

Light detection control unit 24 receives the detection signal from the clutter detection pixels 23, on the basis of this detection signal, the drive circuit 22 controls the reverse bias voltage V _B and quench resistance gate voltage V _QG2 supplied.

Specifically, as shown in FIG. 16, when the light source 2 emits pulsed laser light (see time t21), the pulsed laser light is reflected in the housing 9 to generate clutter (see time t22). ). Then, when the clutter enters the clutter detection pixel 23, the clutter detection pixel 23 detects the clutter. When the detection signal is input from the clutter detection pixel 23, the light detection controller 24 outputs an operation start signal for starting the operation of SPAD to the drive circuit 22 as the control signal. Thus, the drive circuit 22, a reverse bias voltage _{V B,} the breakdown from the voltage _{V BRK} lower undetectable voltage _{V B2,} changing to a higher than the breakdown voltage _{V BRK} detectable voltage _{V B1} (see time t23). Furthermore, the drive circuit 22 changes the quench resistance gate voltage V _QG2 from the off voltage V _OFF1 to the quench voltage V _QCH2 (see time t23).

As a result, the inter-terminal voltage V _SPAD between the anode and the cathode in the SPAD of the light receiving element 31 rises from the undetectable voltage V _B2 to the detectable voltage V _B1 (see times t23 to t24). When the SPAD terminal voltage V _SPAD reaches the detectable voltage V _B1 , the photodetection control unit 24 outputs a recharge end signal for ending the recharge to the drive circuit 22 as the control signal. As a result, the drive circuit 22 changes the quench resistance gate voltage V _QG2 from the quench voltage V _QCH2 to the off voltage V _OFF1 (see time t24).

  The radar apparatus 1 configured as described above includes two N-type transistors functioning as SPAD quench resistors 41 and 46 in the pixel 21. Then, the light detection control unit 24 changes the quench resistor 46 from the off state to the on state when starting the SPAD operation. As a result, the amount of current flowing through the SPAD increases, so that the time for recharging the SPAD can be shortened, and the dead time can be further shortened.

In the embodiment described above, the quench resistor 41 is the first transistor in the present invention, and the quench resistor 46 is the second transistor in the present invention.
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.

  For example, in the third embodiment, the delay time is set by delaying the input light emission signal with the delay element. However, the delay time may be set with a timer.

  DESCRIPTION OF SYMBOLS 1 ... Radar device, 2 ... Light source, 21 ... Pixel, 24 ... Light detection control part, 91 ... D type flip-flop circuit

Claims (11)

A radar apparatus (1) that obtains information about an object that reflects light by irradiating light and detecting light reflected by the object,
A light irradiating means (2) installed inside the radar device for irradiating light;
A reflected light detecting means (21) comprising a SPAD (Single Photon Avalanche Diode) installed inside the radar apparatus, and detecting the light reflected by the object by the SPAD;
Operation start means (24, 91) for starting the operation of the SPAD after the timing when the internally scattered light generated by the light irradiated by the light irradiation means being reflected inside the radar apparatus enters the SPAD A radar apparatus comprising: An internal scattered light detecting means (23, 80) for detecting the internal scattered light;
The operation starting means is
The radar apparatus according to claim 1, wherein the operation of the SPAD is started after the internal scattered light detection means detects the internal scattered light. An information processing means (12) for performing an information processing for acquiring information on the object by inputting a signal output when the reflected light detection means detects light;
The information processing means includes
The radar apparatus according to claim 2, wherein the information processing is performed by inputting a signal output when the internal scattered light detection means (80) detects light. The radar apparatus according to claim 2 or 3, further comprising a reflector (70) that reflects light inside the radar apparatus. The operation starting means (24)
The operation of the SPAD is started after a preset delay time has elapsed after obtaining a signal output at the timing when the light irradiation means irradiates light. The radar device according to any one of 4. The operation starting means (24)
The operation of the SPAD is started by controlling the reverse bias voltage applied to the SPAD and changing the magnitude of the reverse bias voltage from less than the breakdown voltage to more than the breakdown voltage. The radar apparatus according to any one of claims 5 to 6. The operation start means (24, 91)
By controlling the switches (45, 55) connected to the SPAD and changing the switch from the OFF state to the ON state, the magnitude of the reverse bias voltage applied to the SPAD is changed from less than the breakdown voltage to the breakdown voltage. The radar apparatus according to any one of claims 1 to 5, wherein the operation of the SPAD is started by changing the above. The operation starting means (24)
The amount of current flowing through the SPAD is increased when the operation start unit starts the operation of the SPAD than before the operation of the SPAD is started. The radar apparatus according to item 1. Comprising a transistor (41) functioning as a quench resistor of the SPAD;
The operation starting means is
When the operation starting means starts the SPAD operation, the amount of current flowing through the SPAD is increased by increasing the voltage applied to the gate of the transistor than before starting the SPAD operation. The radar apparatus according to claim 8. A first transistor (41) and a second transistor (46) functioning as a quench resistor of the SPAD;
The operation starting means is
The radar apparatus according to claim 8, wherein when the operation start unit starts the operation of the SPAD, the second transistor is changed from an off state to an on state. The radar device according to any one of claims 1 to 10, wherein a circuit functioning as the operation start means (24) is disposed outside a light receiving unit of the SPAD.