WO2019142778A1

WO2019142778A1 - Reception device, control method, program, and storage medium

Info

Publication number: WO2019142778A1
Application number: PCT/JP2019/000904
Authority: WO
Inventors: 野中　慶也
Original assignee: パイオニア株式会社
Priority date: 2018-01-22
Filing date: 2019-01-15
Publication date: 2019-07-25

Abstract

A distance measurement device 100 has an LD driver 12, a laser diode 13, a MEMS mirror 14, a reception element 21, a current/voltage conversion circuit 22, and a signal processing unit 20 and other components. The LD driver 12, the laser diode 13, and the MEMS mirror 14 for reflecting a light pulse while changing an angle function as an emission unit and emit a light pulse while changing an emission direction. The reception element 21 receives return light of a light pulse reflected by an object. The signal processing unit 20 determines the gain M of the current/voltage conversion circuit 22 for amplifying an output signal of the reception element 21, on the basis of the change dθ in the angle of the MEMS mirror 14 after emission of the light pulse by the emission unit.

Description

Receiving device, control method, program, and storage medium

The present invention relates to a technology for receiving an electromagnetic wave reflected by an object.

Conventionally, a distance measuring device that performs scanning with laser light is known. For example, according to Patent Document 1, a plurality of distance values are calculated by dynamically changing the transmission intensity or the reception amplification factor at predetermined time intervals, and the received wave is not saturated among the calculated distance values, And the laser radar apparatus which can output the high distance value of the intensity | strength of a received wave as a ranging distance is disclosed.

JP 2008-275331 A

According to the method of Patent Document 1, while the received wave is not saturated and a distance value with high intensity of the received wave can be output as a ranging distance, laser light is used multiple times to determine one ranging distance. Because it is necessary to emit light and calculate a plurality of distance values, there arises a problem that it is difficult to obtain distance measurement distances efficiently and at high density.

The present invention has been made to solve the problems as described above, and it is possible to accurately output even when an electromagnetic wave reflected by an object present at a distance or near distance is received. The main object of the present invention is to provide a receiver capable of

The invention described in the claims is a receiving device, which has a reflecting portion that reflects an electromagnetic wave while changing an angle, and an emitting portion that emits an electromagnetic wave while changing an emitting direction, and the electromagnetic wave reflected by an object. A receiving unit for receiving; and a determining unit for determining a gain of an amplifying unit for amplifying an output signal of the receiving unit based on an amount of change in angle of the reflecting unit after the emitting unit emits the electromagnetic wave. It is characterized by having.

The invention described in the claims is a receiving device, which has a reflecting portion that reflects an electromagnetic wave while changing the angle, and the emitting portion that emits an electromagnetic wave while changing the emitting direction, and the above reflected by the object A receiver comprising: a receiver configured to receive an electromagnetic wave; and a determiner configured to determine a gain of the receiver based on an amount of change in the angle of the reflector after the emitter emits the electromagnetic wave. .

The invention described in the claims is a control method executed by a receiving apparatus having a reflection unit that reflects an electromagnetic wave while changing an angle, and an emission process of emitting an electromagnetic wave while changing an emission direction, and reflection by an object Receiving step of receiving the electromagnetic wave by the receiving portion, and gain of an amplifying portion amplifying the output signal of the receiving portion based on an angle change amount of the reflecting portion after emitting the electromagnetic wave in the emitting step And determining a step of determining

The invention described in the claims includes a reflection unit that reflects an electromagnetic wave while changing an angle, and an emission unit that emits an electromagnetic wave while changing an emission direction, and a reception unit that receives the electromagnetic wave reflected by an object. A program executed by the computer of the receiving apparatus, the amplifying unit amplifying the output signal of the receiving unit based on the amount of change in the angle of the reflecting unit after the emitting unit emits the electromagnetic wave. The computer functions as a determination unit to determine the gain of

It is a schematic structure of a distance measuring device common to the first embodiment and the second embodiment. The waveform in the time series of a trigger signal and a segment extraction signal is shown. The structural example of a receiving block is shown. It is a figure explaining the time change of the angle of a MEMS mirror. The side view of the MEMS mirror which showed the state at the time of reflection of transmitting light, and reflection of return light is shown. It is a functional block of the gain correction | amendment process in 1st Example. An example of the correspondence of the angle change amount of the MEMS mirror in one segment period and the amplification factor of an amplifier is shown. It is a flowchart which shows the procedure of the gain correction | amendment process in 1st Example. It is a functional block of the gain correction | amendment process in 2nd Example. An example of the correspondence of the elapsed time in one segment period and the amplification factor of an amplifier is shown. It is a flowchart which shows the procedure of the gain correction | amendment process in 2nd Example. 7 shows an example of a conversion map referred to in the modification.

According to a preferred embodiment of the present invention, there is provided a receiving apparatus comprising: a reflector configured to reflect an electromagnetic wave while changing an angle; and an emitter configured to emit an electromagnetic wave while changing an emission direction, and to be reflected by an object A determination unit that determines a gain of an output signal of the receiving unit based on a receiving unit that receives the electromagnetic wave and an angle change amount of the reflecting unit after the emitting unit emits the electromagnetic wave And. Generally, the farther the distance is, the larger the amount of change in the angle of the reflecting portion that occurs before the electromagnetic wave emitted toward the object returns to the receiving portion, and the reception strength becomes weaker. Taking the above into consideration, the receiving apparatus determines the gain of the amplifying unit for amplifying the output signal of the receiving unit based on the above-mentioned angle change amount, thereby receiving the electromagnetic wave received without causing saturation and deficiency of the signal level. It is possible to preferably generate an output signal according to the intensity of.

In one aspect of the receiving apparatus, the determination unit determines the gain to be a smaller value as the amount of change in angle is smaller. In other words, the determination unit changes the gain to a smaller value as the angle change amount is smaller. According to this aspect, in the receiving device, the closer the object is to the distance, the smaller the amount of change in the angle of the reflecting portion that occurs before the electromagnetic wave emitted toward the object returns to the receiving portion, and the receiving intensity becomes stronger. The gain of the amplification unit can be suitably determined in consideration of

In another aspect of the receiver, the determination unit changes the gain in accordance with the angle change amount. In other words, the determination unit determines the gain in accordance with the angle change amount. According to this aspect, the reception device can set the gain of the amplification unit to an appropriate value in accordance with the distance at which the object to be distance-measured exists.

In another aspect of the receiving apparatus, the reflecting unit is a MEMS mirror, and the determining unit determines the gain based on an angle of the reflecting unit and the amount of change in the angle. In general, in the scanning by the MEMS mirror, the speed of the angular change of the MEMS mirror differs depending on the scanning position. Therefore, in this aspect, the receiving apparatus can more accurately determine the gain of the amplification unit by further considering the angle of the MEMS mirror which is the reflection unit.

In another aspect of the receiving device, the receiving device further includes a correction unit that corrects an output signal from the amplification unit based on a gain of the amplification unit when the output signal is output. According to this aspect, the receiving device can preferably generate an output signal that does not depend on the gain of the amplification unit.

In another aspect of the receiving device, the receiving device further includes a calculating unit that calculates a distance to the object based on the output signal corrected by the correcting unit. According to this aspect, the receiving device can accurately calculate the distance to the object based on the corrected output signal.

In another aspect of the receiving apparatus, the emitting unit periodically and repeatedly emits the electromagnetic wave, and the determining unit determines the gain based on the amount of change in angle within one cycle. According to this aspect, the receiving apparatus can accurately determine the gain of the amplification unit in each cycle when emitting electromagnetic waves periodically and repeatedly.

According to another preferred embodiment of the present invention, the receiving device has a reflecting portion that reflects the electromagnetic wave while changing the angle, and an emitting portion that emits the electromagnetic wave while changing the emitting direction, and the object reflected by the object The receiver includes: a receiver configured to receive the electromagnetic wave; and a determiner configured to determine a gain of the receiver based on an amount of change in angle of the reflector after the emitter emits the electromagnetic wave. According to this aspect, the receiving apparatus determines the gain of the receiving unit based on the above-mentioned angle change amount, thereby producing an output signal according to the intensity of the received electromagnetic wave without causing saturation and deficiency of the signal level. Can be suitably generated.

According to another preferred embodiment of the present invention, there is provided a control method executed by a receiving apparatus having a reflecting portion for reflecting an electromagnetic wave while changing an angle, comprising: an emitting step for emitting an electromagnetic wave while changing an emitting direction; An amplification process for amplifying an output signal of the receiving unit based on an amount of change in angle of the reflecting unit after receiving the electromagnetic wave reflected by the object by the receiving unit; Determining the gain of the part. By executing this control method, the receiving apparatus can preferably generate an output signal according to the intensity of the received electromagnetic wave without causing saturation and deficiency of the signal level.

According to another preferred embodiment of the present invention, there is provided a reflecting portion for reflecting an electromagnetic wave while changing an angle, and an emitting portion for emitting an electromagnetic wave while changing an emitting direction, and the electromagnetic wave reflected by an object. A program executed by a computer of a receiving apparatus having a receiving unit, the output unit amplifying the output signal of the receiving unit based on an amount of change in angle of the reflecting unit after the emitting unit emits the electromagnetic wave. The computer functions as a determination unit that determines the gain of the amplification unit. By executing this program, the computer can preferably generate an output signal according to the intensity of the received electromagnetic wave without causing saturation and deficiency of the signal level. Preferably, the program is stored in a storage medium.

Hereinafter, preferred first and second embodiments of the present invention will be described with reference to the drawings.

First Embodiment
[overall structure]
FIG. 1 is a schematic configuration of a distance measuring apparatus 100 common to the first embodiment and the second embodiment. The distance measuring apparatus 100 discretely measures the distance to an object present in the external world by emitting a pulse laser which is an electromagnetic wave to a predetermined angle range in the horizontal direction and the vertical direction, and measures the position of the object Generate three-dimensional point cloud information to be shown. The distance measuring apparatus 100 is, for example, a Time of Flight type lidar (Lidar: Light Detection and Ranging or Laser Illuminated Detection And Ranging). The range finder 100 mainly includes a crystal oscillator 10, a synchronization control unit 11, an LD driver 12, a laser diode 13, a MEMS mirror 14, a drive driver 15, an angle sensor 16, and a reception block 17. And a signal processing unit 20.

The crystal oscillator 10 outputs a pulse-like clock signal “S1” to the synchronization control unit 11 and the A / D converter 23.

The synchronization control unit 11 outputs a pulse-like trigger signal “S2” to the LD driver 12. Hereinafter, a period from the assertion of the trigger signal S2 to the next assertion is also referred to as a "segment period". Further, the synchronization control unit 11 outputs a segment extraction signal “S3” that determines the timing of extracting the output of the A / D converter 23 to the signal processing unit 20. The trigger signal S2 and the segment extraction signal S3 are logic signals and are synchronized as shown in FIG. 2 described later.

The LD driver 12 supplies a pulse current to the laser diode 13 in synchronization with the trigger signal S2 input from the synchronization control unit 11. The laser diode 13 is, for example, an infrared pulse laser, and emits a light pulse (also referred to as “transmission light”) based on the pulse current supplied from the LD driver 12.

The MEMS mirror 14 reflects the light pulse emitted from the laser diode 13 to the outside while changing the angle in the range of a predetermined horizontal angle and vertical angle, and the light reflected by the object irradiated with the light pulse (“ ) Is reflected toward the light receiving element 21. In this case, the MEMS mirror 14 emits a light pulse for each segment obtained by equally dividing the above-described horizontal angle. The MEMS mirror 14 is an example of the "reflecting portion" in the present invention. The drive driver 15 applies a drive current to the MEMS mirror 14 to drive the MEMS mirror 14 in the horizontal direction and the vertical direction.

The MEMS mirror 14 is provided with an angle sensor 16. The angle sensor 16 is, for example, a piezo sensor that detects the position of the MEMS mirror 14 in the horizontal direction and the vertical direction. The angle sensor 16 supplies the signal processing unit 20 with an angle detection signal “S4” related to the detection angle of the MEMS mirror 14. The LD driver 12, the laser diode 13, and the MEMS mirror 14 are examples of the "emission part" in the present invention.

The receiving block 17 outputs a voltage signal proportional to the intensity of the return light from the object, and mainly includes the light receiving element 21, a current / voltage conversion circuit (transimpedance amplifier) 22, and an A / D converter 23. And. A specific configuration example of the reception block 17 will be described later with reference to FIG.

The light receiving element 21 is, for example, an avalanche photodiode, and generates a weak current according to the light quantity of the reflected light from the object guided by the MEMS mirror 14, that is, the return light. The light receiving element 21 supplies the generated weak current to the current-voltage conversion circuit 22. The current voltage conversion circuit 22 amplifies the weak current supplied from the light receiving element 21 and converts it into a voltage signal, and inputs the converted voltage signal to the A / D converter 23. The A / D converter 23 converts the voltage signal supplied from the current-voltage conversion circuit 22 into a digital signal based on the clock signal S1 supplied from the crystal oscillator 10, and supplies the converted digital signal to the signal processing unit 20. . The light receiving element 21 is an example of the “receiving unit” in the present invention, and the current-voltage conversion circuit 22 is an example of the “amplifying unit” in the present invention.

The signal processing unit 20 determines the reception amplification factor (gain) to be set in the reception block 17 based on the angle detection signal S4 supplied from the angle sensor 16, and receives the control signal “S5” related to the reception amplification factor. Supply to. Thus, the signal processing unit 20 functions as a "determination unit" in the present invention. Further, the signal processing unit 20 functions as a “computer” in the present invention when it is executed by a program.

Further, the signal processing unit 20 generates a digital signal which is an output of the A / D converter 23 in a period in which the segment extraction signal S3 is asserted as a signal (also referred to as a “segment signal”) related to the light reception intensity for each segment. Do. Then, the signal processing unit 20 generates point group information indicating the distance and angle of the object based on the segment signal. Specifically, the signal processing unit 20 detects a peak from the waveform of the segment signal, and estimates an amplitude and a delay time corresponding to the detected peak. Then, the signal processing unit 20 determines, among the peaks of the waveform indicated by the segment signal, information of a distance corresponding to a delay time of a peak at which the estimated amplitude is a predetermined threshold or more and information of an angle corresponding to the target segment. A set is generated as information of each point constituting point cloud information.

Preferably, the signal processing unit 20 and the like may be configured by hardware such as an application specific integrated circuit (ASIC) or a field-programmable gate array (FPGA) so as to realize high-speed control.

FIG. 2 shows waveforms of the trigger signal S2 and the segment extraction signal S3 in time series. As shown in FIG. 2, the rising edges of the trigger signal S2 and the segment extraction signal S3 are synchronized, and the segment extraction signal S3 is asserted for a predetermined period longer than the period in which the trigger signal S2 is asserted. Then, the signal processing unit 20 extracts a signal output by the A / D converter 18 while the trigger signal S2 is asserted as a segment signal. Then, as the assert period during which the segment extraction signal S3 is asserted is longer, the maximum distance measurement distance (distance measurement limit distance) from the rider unit 100 is longer.

FIG. 3 shows a configuration example of the reception block 17. The receiving block 17 shown in FIG. 3 is a TIA (transimpedance amplifier) type receiver with a clamp diode, and the light receiving element 21, the current-voltage conversion circuit 22, the A / D converter 23, the clamp diode 24, and the

low resistance

25 and 26 and a preamplifier 27. The current-voltage conversion circuit 22 includes a capacitor 30, a feedback resistor 31, and an operational amplifier (operational amplifier) 32.

A high voltage "Vr" supplied from the signal processing unit 20 or the like is applied to the light receiving element 21 as a reverse bias, and a detection current proportional to the return light from the object flows. Then, the detected current output from the light receiving element 21 is amplified by the current voltage conversion circuit 22 and converted into a voltage signal. Here, the amplification factor (also referred to as “gain M”) of the current-voltage conversion circuit 22 (that is, the operational amplifier 32) can be adjusted by the control signal S5 supplied from the signal processing unit 20. The voltage signal output from the current-voltage conversion circuit 22 is amplified by the preamplifier 27 and supplied to the A / D converter 23.

When attempting to realize distance measurement for an object at a long distance by the distance measuring apparatus 100, the laser is such that the intensity of the voltage signal input to the A / D converter 23 is equal to or higher than the intensity distinguishable by the A / D converter 23. It is necessary to increase the output of the diode 13 and also to increase the light receiving sensitivity (image magnification) of the receiving block 17. On the other hand, in such a setting state, when the object is at a short distance and the return light whose light intensity becomes excessive is received, the voltage signal input to the A / D converter 23 is saturated and the segment signal is appropriately Not generated Taking the above into consideration, in the first and second embodiments, the distance measuring apparatus 100 dynamically adjusts the gain M of the current-voltage conversion circuit 22 to either an object existing in the vicinity or an object existing in the distance The distance to the subject is accurately measured.

[Gain correction processing]
Next, processing for dynamically changing the gain M (also referred to as "gain correction processing") in the first embodiment will be described in detail. Generally, the signal processing unit 20 measures the amount of change in the angle of the MEMS mirror 14 (also referred to as “the amount of change in angle dθ”) after the light pulse is emitted, and corresponds to the amount of change in angle dθ. The gain M is gradually changed within each segment period. As a result, the signal processing unit 20 substantially expands the dynamic range of the A / D converter 23, and preferably suppresses saturation or deficiency of the signal level of the voltage signal input to the A / D converter 23.

First, the time change of the angle of the MEMS mirror 14 will be described with reference to FIGS. 4 and 5.

FIG. 4A shows a schematic scan line of transmission light on a virtual irradiation surface (virtual irradiation surface) separated by a predetermined distance ahead. Here, the irradiation points 50 to 52 indicate points at which transmission light emitted at a certain timing is irradiated on the virtual irradiation surface. 4B shows a side view of the MEMS mirror 14 when the transmission light corresponding to the irradiation point 50 is reflected, and FIG. 4C shows the MEMS when the transmission light corresponding to the irradiation point 51 is reflected. FIG. 4D shows a side view of the mirror 14 and FIG. 4D shows a side view of the MEMS mirror 14 when the transmission light corresponding to the irradiation point 52 is reflected. The broken lines in FIGS. 4A to 4D are lines virtually representing the normal of the MEMS mirror 14.

As shown in FIGS. 4B to 4D, the MEMS mirror 14 reflects the transmission light corresponding to the irradiation point 50, reflects the transmission light corresponding to the irradiation point 51, and emits the irradiation light. The angle changes when the transmission light corresponding to the point 52 is reflected. As described above, since the MEMS mirror 14 controls the emission direction of the transmission light by continuously changing the angle, the angle change occurs between the reflection of the transmission light and the incidence of the return light.

FIG. 5 (A) shows a side view of the MEMS mirror 14 when the transmission light is reflected, and FIG. 5 (B) shows when the return light of the transmission light shown in FIG. 5 (A) is incident on the MEMS mirror 14 Side view of the MEMS mirror 14 of FIG. In the examples of FIGS. 5A and 5B, the angle change of the MEMS mirror 14 occurs by the angle change amount dθ between the time when the transmission light is reflected and the time when the return light is incident. In FIG. 5B, the position of the MEMS mirror 14 when the transmission light is reflected is virtually shown by a broken line. Then, the angle change amount dθ becomes larger as the time from the reflection of the transmission light to the incidence of the return light becomes longer. Therefore, when the target to which the transmission light is irradiated is present at a short distance, the time from the reflection of the transmission light to the incidence of the return light is short, so the angle change amount dθ becomes almost zero. On the other hand, when the target to which the transmission light is irradiated is present in the distance, the angle change amount dθ has a value corresponding to the time from the reflection of the transmission light to the incidence of the return light.

FIG. 6 shows a functional block diagram of the signal processing unit 20 related to gain correction processing in the first embodiment. As shown in FIG. 6, the signal processing unit 20 functionally converts the angle storage unit 40, the reset unit 41, the angle change amount calculation unit 42, the gain setting unit 43, the output correction unit 44, and And a map 45.

The angle storage unit 40 stores the angle of the MEMS mirror 14 detected by the angle sensor 16 when the laser diode 13 emits light. For example, the angle storage unit 40 stores the angle of the MEMS mirror 14 detected by the angle sensor 16 when the trigger signal S2 is asserted. The angle storage unit 40 is, for example, a latch circuit. The reset unit 41 clears the angle storage unit 40 for each segment period. For example, the reset unit 41 clears the angle storage unit 40 at an arbitrary timing from the end of the assert period of the segment extraction signal S3 shown in FIG. 2 to the next assertion of the trigger signal S2 and the segment extraction signal S3.

The angle change amount calculation unit 42 is an angle difference between the angle of the MEMS mirror 14 (also referred to as “light emission angle”) stored in the angle storage unit 40 and the current angle of the MEMS mirror 14 output by the angle sensor 16. Is calculated as the angle change amount dθ. Then, the angle change amount calculation unit 42 supplies the calculated angle change amount dθ to the gain setting unit 43.

The gain setting unit 43 calculates a gain M to be set from the angle change amount dθ output from the angle change amount calculation unit 42 with reference to a conversion map 45 described later. Then, the gain setting unit 43 supplies the control signal S5 specifying the calculated gain M to the current-voltage conversion circuit 22. Here, as described later, the gain setting unit 43 sets the gain M so that the gain M decreases as the angle change amount dθ decreases, and the gain M increases as the angle change amount dθ increases.

The output correction unit 44 stores the gain M supplied from the gain setting unit 43 and the output signal of the A / D converter 23. Then, the output correction unit 44 corrects the output signal of the A / D converter 23 based on the gain M. Specifically, the output correction unit 44 corrects the level of the output signal of the A / D converter 23 so as not to depend on the change of the gain M. For example, the output correction unit 44 corrects the signal level of the output signal of the A / D converter 23 to a signal level predicted to be obtained when the gain M is a predetermined reference value. In this case, the output correction unit 44 increases or decreases the level of the output signal of the A / D converter 23 by a predetermined ratio according to, for example, the ratio between the gain M notified from the gain setting unit 43 and the above-described reference value. Thus, the output correction unit 44 suitably generates an output signal that does not depend on the gain M.

The conversion map 45 is a map that defines an appropriate gain M for the angle change amount dθ, and is referred to by the gain setting unit 43.

FIG. 7 shows the correspondence between the angle change amount dθ and the gain M in one segment period specified by the conversion map 45. In the conversion map 45 shown in FIG. 7, the gain M is smaller as the angle change amount dθ is smaller, and the gain M is defined such that the gain M is larger as the angle change amount dθ is larger. By referring to such a conversion map 45, the gain setting unit 43 determines an appropriate gain M according to the amount of angle change dθ for each segment period, substantially expanding the dynamic range of the A / D converter 23. It can be done.

The correspondence between the amount of angle change dθ and the gain M shown in FIG. 7 will be supplementarily described. As described in FIGS. 4 and 5, the smaller the angle change amount dθ, that is, the shorter the time from reflection of transmission light to incidence of its return light, the object irradiated with the transmission light is It exists at a short distance, and the intensity of the return light becomes strong. Therefore, the smaller the angle change amount dθ, the higher the signal level of the voltage signal input to the A / D converter 23. Therefore, in order to prevent the saturation in the A / D converter 23, it is necessary to reduce the gain M. Similarly, the larger the angle change amount dθ, ie, the longer the time from reflection of transmission light to incidence of its return light, the longer the object irradiated with the transmission light, the return light The strength of the Therefore, the larger the angle change amount dθ, the smaller the signal level of the voltage signal input to the A / D converter 23. Therefore, in order to prevent the shortage of the signal level in the A / D converter 23, it is necessary to increase the gain M. is there. Taking the above into consideration, in the conversion map 45 shown in FIG. 7, the gain M is smaller as the angle change amount dθ is smaller, and the gain M is defined such that the gain M is larger as the angle change amount dθ is larger.

FIG. 8 is a flowchart showing the procedure of the gain correction process in the first embodiment.

First, the reset unit 41 of the signal processing unit 20 clears the angle storage unit 40 at a predetermined timing before emission of transmission light by the laser diode 13 (step S101). Thereafter, the laser diode 13 emits transmission light based on the trigger signal S2 supplied from the synchronization control unit 11 (step S102). Then, the angle storage unit 40 sets the angle of the MEMS mirror 14 detected by the angle sensor 16 at the timing when the laser diode 13 emits the transmission light (that is, the timing when the trigger signal S2 and the segment extraction signal S3 assert). Are stored (step S103).

Next, the angle change amount calculation unit 42 calculates an angle difference between the light emission angle stored in the angle storage unit 40 and the current angle of the MEMS mirror 14 output by the angle sensor 16 as the angle change amount dθ (see Step S104). Then, the gain setting unit 43 sets the gain M according to the angle change amount dθ in the current-voltage conversion circuit 22 (step S105). In this case, gain setting unit 43 calculates gain M from angle change amount dθ with reference to conversion map 45 as shown in FIG. 7, and generates control signal S5 for specifying calculated gain M as current-voltage conversion circuit 22. Supply to. Then, after storing the gain M supplied from the gain setting unit 43 and the output signal of the A / D converter 23, the output correction unit 44 stores the output signal of the A / D converter 23 according to the gain M. It corrects (step S106).

Then, the signal processing unit 20 determines whether it is the next light emission timing (step S107). Then, when the signal processing unit 20 determines that it is the next light emission timing (step S107; Yes), the process returns to step S101 to clear the angle storage unit 40. On the other hand, when the signal processing unit 20 determines that it is not the next light emission timing (step S107; No), the process returns to step S104, and the angle difference from the current angle of the MEMS mirror 14 output by the angle sensor 16 is The angle change amount dθ is calculated. By doing this, the signal processing unit 20 appropriately increases the gain M according to the gradually rising angle change amount dθ for each segment period, and the saturation in the A / D converter 23 and the shortage of the signal level Etc. can be suitably prevented. In step S107, when the assert period of the segment extraction signal S3 ends, the signal processing unit 20 may determine that the next light emission timing has come sufficiently, and the process may return to step S101.

As described above, the distance measuring apparatus 100 according to the first embodiment includes the LD driver 12, the laser diode 13, the MEMS mirror 14, the receiving element 21, the current-voltage conversion circuit 22, the signal processing unit 20, and the like. Then, the LD driver 12, the laser diode 13, and the MEMS mirror 14 that reflects the light pulse while changing the angle function as an emitting unit, and emit the light pulse while changing the emitting direction. The light receiving element 21 receives the return light of the light pulse reflected by the object. Then, the signal processing unit 20 determines the gain M of the current-voltage conversion circuit 22 that amplifies the output signal of the light receiving element 21 based on the angle change amount dθ of the MEMS mirror 14 after the emitting unit emits the light pulse. Do. As a result, the dynamic range of the A / D converter 23 can be substantially expanded, and saturation or deficiency of the signal level in the A / D converter 23 can be suitably suppressed.

Second Embodiment
In the second embodiment, the signal processing unit 20 calculates, for each segment period, an elapsed time (also referred to as “elapsed time Td”) from the time of emission of transmission light instead of the angle change amount dθ. Is different from the first embodiment in that the gain M is changed according to. In addition, about the structure similar to 1st Example, the same code | symbol is suitably attached and the description is abbreviate | omitted.

FIG. 9 shows a functional block diagram of the signal processing unit 20 related to gain correction processing in the second embodiment. As shown in FIG. 9, the signal processing unit 20 according to the second embodiment functionally includes an elapsed time calculation unit 42A, a gain setting unit 43A, and an output correction unit 44A.

When the elapsed time calculation unit 42A detects the timing at which the light pulse is emitted based on the trigger signal S2 supplied from the synchronization control unit 11, the light pulse is further detected based on the clock signal S1 supplied from the crystal oscillator 10. The elapsed time Td from the emission to the present is calculated. Then, the elapsed time calculation unit 42A supplies the calculated elapsed time Td to the gain setting unit 43A.

The gain setting unit 43A refers to the conversion map 45A, and determines the gain M to be set from the elapsed time Td supplied from the elapsed time calculation unit 42A. Then, the gain setting unit 43A transmits a control signal S5 instructing application of the determined gain M to the current-voltage conversion circuit 22.

The output correction unit 44A stores the gain M supplied from the gain setting unit 43A and the output signal of the A / D converter 23. Then, the output correction unit 44A corrects the output signal of the A / D converter 23 based on the gain M. Specifically, like the output correction unit 44 of the first embodiment, the output correction unit 44A corrects the level of the output signal of the A / D converter 23 so as not to depend on the change of the gain M. For example, the output correction unit 44A corrects the level of the output signal of the A / D converter 23 to a signal level predicted to be obtained when the gain M is a predetermined reference value. Thus, the output correction unit 44A suitably generates an output signal that does not depend on the gain M.

FIG. 10 shows the correspondence between the elapsed time Td and the gain M in one segment period specified by the conversion map 45A. In the conversion map 45A shown in FIG. 10, the gain M is defined so that the gain M decreases as the elapsed time Td decreases, and the gain M increases as the elapsed time Td increases.

The correspondence between the elapsed time Td and the gain M shown in FIG. 10 will be supplementarily described. Generally, the shorter the elapsed time Td, the closer the object irradiated with the transmission light is, and the stronger the intensity of the return light. Therefore, as the elapsed time Td is shorter, the signal level of the voltage signal input to the A / D converter 23 is higher, so the gain M needs to be reduced to prevent the saturation in the A / D converter 23. On the other hand, the longer the elapsed time Td, the longer the object irradiated with the transmission light, and the weaker the intensity of the return light. Therefore, as the elapsed time Td is longer, the signal level of the voltage signal input to the A / D converter 23 is smaller. Therefore, in order to prevent the shortage of the signal level in the A / D converter 23, it is necessary to increase the gain M. . Taking the above into consideration, in the conversion map 45A shown in FIG. 10, the gain M is smaller as the elapsed time Td is shorter, and the gain M is defined so that the gain M is larger as the elapsed time Td is longer.

FIG. 11 is a flowchart showing the procedure of gain correction processing in the second embodiment.

The laser diode 13 emits transmission light based on the trigger signal S2 supplied from the synchronization control unit 11 (step S201). Then, the elapsed time calculation unit 42A calculates an elapsed time Td which is an elapsed time from the timing when the laser diode 13 emits the transmission light (that is, the timing when the trigger signal S2 and the segment extraction signal S3 are asserted) (step S202). . Then, the gain setting unit 43A sets the gain M according to the elapsed time Td calculated by the elapsed time calculation unit 42A in the current-voltage conversion circuit 22 (step S203). In this case, gain setting unit 43A calculates gain M from elapsed time Td with reference to conversion map 45A as shown in FIG. 10, and sends control signal S5 specifying the calculated gain M to current-voltage conversion circuit 22. Supply.

After storing the gain M supplied from the gain setting unit 43A and the output signal of the A / D converter 23, the output correction unit 44A corrects the output signal of the A / D converter 23 according to the gain M. (Step S204).

Then, the signal processing unit 20 determines whether it is the next light emission timing (step S205). When the signal processing unit 20 determines that it is the next light emission timing (step S205; Yes), the process returns to step S201. On the other hand, when the signal processing unit 20 determines that it is not the next light emission timing (step S205; No), the process returns to step S202 and continues based on the clock signal S1 and the like supplied from the crystal oscillator 10 Perform the addition. By doing this, the signal processing unit 20 appropriately increases the gain M according to the elapsed time for each segment period, and suitably prevents saturation or shortage of the signal level in the A / D converter 23 and the like. it can. In step S205, when the assert period of the segment extraction signal S3 ends, the signal processing unit 20 may determine that the next light emission timing is approached, and the process may return to step S201.

As described above, the distance measuring apparatus 100 according to the second embodiment includes the LD driver 12, the laser diode 13, the MEMS mirror 14, the receiving element 21, the current-voltage conversion circuit 22, the signal processing unit 20, and the like. Then, the LD driver 12, the laser diode 13, and the MEMS mirror 14 that reflects the light pulse while changing the angle function as an emitting unit, and emit the light pulse while changing the emitting direction. The light receiving element 21 receives the return light of the light pulse reflected by the object. Then, the signal processing unit 20 determines the gain M of the current-voltage conversion circuit 22 that amplifies the output signal of the light receiving element 21 based on an elapsed time Td which is an elapsed time after the emitting unit emits the light pulse. . As a result, the dynamic range of the A / D converter 23 can be substantially expanded, and saturation or deficiency of the signal level in the A / D converter 23 can be suitably suppressed.

<Modification>
Next, modifications suitable for the first and second embodiments will be described. The following modifications may be arbitrarily combined and applied to the above-described embodiment.

(Modification 1)
In the first and second embodiments, the signal processing unit 20 may raise the gain M of the current-voltage conversion circuit 22 stepwise, instead of continuously increasing the gain M of the current-voltage conversion circuit 22.

For example, the signal processing unit 20 provides one or more timings for changing the gain M in the segment period, and determines the gain M based on the angle change amount dθ or the elapsed time Td at each change timing of the provided gain M. The control signal S5 specifying the determined gain M is transmitted to the current-voltage conversion circuit 22. In this case, the initial value of the gain M is preset to be smaller than the gain M determined at each change timing. The signal processing unit 20 sets the gain M to an initial value at an arbitrary timing from the end of the assert period of the segment extraction signal S3 to the timing at which the trigger signal S2 and the segment extraction signal S3 are asserted. The gain M is returned to the initial value every time.

Thus, the signal processing unit 20 preferably substantially expands the dynamic range of the A / D converter 23 even when the gain M is gradually increased, and the signal level of the A / D converter 23 can be reduced. Saturation or deficiency can be suitably suppressed.

(Modification 2)
In the first embodiment, the angle change amount calculation unit 42 may switch the conversion map 45 to be referred to in accordance with the angle of the MEMS mirror 14.

FIG. 12A shows a schematic scan line of light pulses on a virtual irradiation surface (virtual irradiation surface) separated by a predetermined distance ahead. In general, in the scanning by the MEMS mirror 14, the scanning speed (ie, the MEMS mirror) in the left and right end areas of the scanning area in the main scanning direction (see dashed frames 60 and 61) compared to other areas (ie, scanning areas near the center) The angular velocity of 14) becomes slower. Therefore, when the MEMS mirror 14 is directed to the left and right end regions of the scanning region, the angle change amount dθ measured at the same elapsed time is smaller than in the other cases. In consideration of the above, in the present modification, the angle change amount calculation unit 42 switches the conversion map 45 to be referred to in accordance with the angle of the MEMS mirror 14.

FIG. 12B shows an angle range (also referred to as a “first angle range”) of the MEMS mirror 14 in which the pulse light is irradiated to the scanning region near the center other than the broken line frames 60 and 61 in FIG. FIG. 12C shows the relationship between the angle change amount dθ indicated by the conversion map 45 referred to when referred to and the gain M, and FIG. The relationship between the amount of angle change dθ and the gain M indicated by the conversion map 45 referred to at the time of (also referred to as “second angle range”) is shown.

When the angle of the MEMS mirror 14 is within the second angle range, the angle change of the MEMS mirror 14 is relatively slower than when the angle of the MEMS mirror 14 is within the first angle range, as shown in FIG. In the conversion map 45 shown, the rate of increase of the gain M with respect to the change of the angle change amount dθ is higher than that of the conversion map 45 shown in FIG. 12 (B). Then, when the detection angle of the MEMS mirror 14 supplied from the angle sensor 16 falls within the first angle range, the angle change amount calculation unit 42 refers to the conversion map 45 shown in FIG. M is determined, and when the detection angle of the MEMS mirror 14 falls within the second angle range, the gain M is determined with reference to the conversion map 45 shown in FIG. 12 (B).

As described above, in the present modification, it is possible to set a more appropriate gain M in consideration of the difference in scanning speed according to the angle of the MEMS mirror 14.

(Modification 3)
The configuration of the distance measuring apparatus 100 shown in FIG. 1 is an example, and the configuration to which the present invention can be applied is not limited to this. For example, the distance measuring apparatus 100 may include a rotating mirror that is rotated by a motor, instead of the MEMS mirror 14. In this case, the angle sensor 16 detects the rotation angle of the rotating mirror, and the signal processing unit 20 calculates the amount of angle change dθ based on the rotation angle detected by the angle sensor 16.

Similarly, the configuration of the reception block 17 shown in FIG. 3 is an example, and the configuration to which the present invention is applicable is not limited thereto. For example, the receiving block 17 may have a configuration in which an amplifier is provided between the light receiving element 21 and the A / D converter 23 and the gain of the amplifier can be adjusted.

(Modification 4)
The signal processing unit 20 may change the gain of the light receiving element 21 instead of changing the gain M of the current-voltage conversion circuit 22.

For example, in the case of the first embodiment, instead of the conversion map 45, the signal processing unit 20 applies the voltage Vr to be applied to the light receiving element 21 to obtain an appropriate gain of the light receiving element 21 for each angle change amount dθ. Store the map shown. Then, the signal processing unit 20 determines the voltage Vr to be applied to the light receiving element 21 based on the angle change amount dθ of the MEMS mirror 14 from the light emission timing of the transmission light by referring to the map, and the voltage Vr Is applied to the light receiving element 21. Thus, the signal processing unit 20 can appropriately set the gain of the light receiving element 21 so as not to cause saturation or deficiency of the light reception amount.

Similarly in the second embodiment, the signal processing unit 20 indicates the voltage Vr to be applied to the light receiving element 21 to obtain an appropriate gain of the light receiving element 21 every elapsed time Td, instead of the conversion map 45A. A map may be stored, and the voltage Vr to be applied to the light receiving element 21 may be determined with reference to the map. Also in this modification, the output correction unit 44 or the output correction unit 44A specifies the gain of the light receiving element 21 based on the voltage Vr applied to the light receiving element 21, and based on the gain, The output signal may be corrected as in the first and second embodiments.

DESCRIPTION OF SYMBOLS 10 Crystal oscillator 11 Synchronization control part 12 LD driver 13 Laser diode 14 MEMS mirror 15 Drive driver 16 Angle sensor 17 Reception block 20 Signal processing part 100 Ranging device

Claims

An emitting unit that has a reflecting unit that reflects an electromagnetic wave while changing the angle, and that emits an electromagnetic wave while changing the emitting direction;
A receiver for receiving the electromagnetic wave reflected by the object;
A determination unit that determines a gain of an amplification unit that amplifies an output signal of the reception unit based on an amount of change in angle of the reflection unit after the emission unit emits the electromagnetic wave;
Receiving device having:
The receiving apparatus according to claim 1, wherein the determination unit determines the gain to a smaller value as the amount of change in angle is smaller.
The receiving device according to claim 1, wherein the determination unit changes the gain in accordance with the amount of change in angle.
The reflection unit is a MEMS mirror,
The receiver according to any one of claims 1 to 3, wherein the determination unit determines the gain based on an angle of the reflection unit and the amount of change in the angle.
The receiver according to any one of claims 1 to 4, further comprising a correction unit that corrects an output signal from the amplification unit based on a gain of the amplification unit when the output signal is output.
The receiving device according to claim 5, further comprising a calculating unit that calculates a distance to the object based on the output signal corrected by the correcting unit.
The emitting unit periodically and repeatedly emits the electromagnetic wave,
The determining unit determines the gain based on the angle change amount in one cycle.
The receiver according to any one of claims 1 to 6.
An emitting unit that has a reflecting unit that reflects an electromagnetic wave while changing the angle, and that emits an electromagnetic wave while changing the emitting direction;
A receiver for receiving the electromagnetic wave reflected by the object;
A determination unit that determines a gain of the receiving unit based on an amount of change in angle of the reflecting unit after the emitting unit emits the electromagnetic wave;
Receiving device having:
A control method executed by a receiving apparatus having a reflection unit that reflects an electromagnetic wave while changing an angle,
An emitting step of emitting an electromagnetic wave while changing an emitting direction;
A receiving step of receiving the electromagnetic wave reflected by the object by a receiving unit;
Based on the amount of change in angle of the reflecting portion after emitting the electromagnetic wave in the emitting step,
A determination step of determining a gain of an amplification unit for amplifying an output signal of the reception unit;
Controlling method.
The computer of the receiving apparatus has a reflection unit that reflects the electromagnetic wave while changing the angle, and an emission unit that emits the electromagnetic wave while changing the emission direction, and a reception unit that receives the electromagnetic wave reflected by the object The program to be
A program that causes the computer to function as a determination unit that determines a gain of an amplification unit that amplifies an output signal of the reception unit based on an amount of change in angle of the reflection unit after the emission unit emits the electromagnetic wave.
A storage medium storing the program according to claim 10.