Patent Application
20220291342
The present invention relates to a ranging system and a driver of a light emitting element.
Ranging systems that measure a distance to an object by irradiating the object with light and detecting the reflected light are known. For example, in Patent Literature 1, an object is irradiated with light from a light emitting unit, the reflected light from the object is received by a light receiving sensor, and a distance to the object is measured on the basis of time of flight (TOF).
Patent Literature 1: JP 2016-211881 A
However, the technology described in Patent Literature 1 has room for improvement in improving the accuracy of ranging.
Therefore, the present disclosure proposes a ranging system and a driver of a light emitting element capable of improving the accuracy of ranging.
A ranging system according to the present disclosure includes: a drive unit that causes a light emitting element to emit light and outputs a drive signal for irradiating a target with light; a sensor unit that detects reflected light from the target; a measurement unit that measures a delay time that is included in a time from timing at which a trigger signal for causing the light emitting element to emit light is output to timing at which the light emitting element actually emits light; and a processing unit that performs a process of calculating a distance to the target on a basis of output timing of the trigger signal, light receiving timing of the reflected light obtained by the sensor unit, and the delay time.
A driver of a light emitting element according to the present disclosure includes: a drive unit that causes the light emitting element to emit light and outputs a drive signal for irradiating a target with light; and a measurement unit that measures a delay time that is included in a time from timing at which a trigger signal for causing the light emitting element to emit light is input to timing at which the light emitting element actually emits light, wherein the driver outputs data corresponding to the delay time measured by the measurement unit.
Hereinafter, embodiments of the present disclosure will be described in detail on the basis of the drawings. Note that in each of the following embodiments, the same parts are denoted by the same symbols, and redundant description will be omitted.
In addition, the present disclosure will be described in the following order of items.
0. Configuration Shared by Embodiments
0.1 Comparative Example
1. First Embodiment
1.4 First Modification of First Embodiment
1.5 Second Modification of First Embodiment
1.6 Third Modification of First Embodiment
1.7 Fourth Modification of First Embodiment
11.7.3 Effects
1.8 Fifth Modification of First Embodiment
1.9 Sixth Modification of First Embodiment
1.10 Seventh Modification of First Embodiment
1.11 Eighth Modification of First Embodiment
1.12 Ninth Modification of First Embodiment
1.13 Tenth Modification of First Embodiment
1.14 Eleventh Modification of First Embodiment
2. Second Embodiment
2.4 First Modification of Second Embodiment
2.5 Second Modification of Second Embodiment
2.6 Third Modification of Second Embodiment
2.7 Fourth Modification of Second Embodiment
2.8 Fifth Modification of Second Embodiment
2.9 Sixth Modification of Second Embodiment
2.10 Seventh Modification of Second Embodiment
2.11 Eighth Modification of Second Embodiment
2.12 Ninth Modification of Second Embodiment
2.13 Tenth Modification of Second Embodiment
2.14 Eleventh Modification of Second Embodiment
3. Third Embodiment
4. Fourth Embodiment
5. Summary
The present disclosure relates to control of a light emitting element that emits light in response to a current, such as a laser diode.
In
The driver 10 drives the laser diode 12 in accordance with a signal from the signal processing unit 51 to cause the laser diode 12 to emit light. The controller 11 includes, for example, a central processing unit (CPU) and a memory and supplies, to the driver 10, a control signal 40 generated by the CPU in accordance with a program prestored in a memory to control the driver 10.
The driver 10 generates a drive signal for driving the laser diode 12 to emit light in a pulse shape in accordance with the signal supplied from the signal processing unit 51. This drive signal is input to the laser diode 12. The laser diode 12 emits light by the drive signal. That is, the laser diode 12 is caused to emit light on the basis of the drive signal generated by the controller 11. The driver 10 sends, to the signal processing unit 51, a signal indicating timing at which the laser diode 12 is caused to emit light.
The controller 11 can determine whether or not an error is occurring on the basis of a detection signal 42 supplied from the driver 10. For example, in a case where delay time that is measured exceeds a determination reference value, it can be determined that an error has occurred. When it is determined that an error has occurred, the controller 11 can output an error signal. The controller 11 can output an error signal to the outside of the ranging system 70, for example.
The ranging sensor unit 302 functions as a sensor unit that detects reflected light from a target. The ranging sensor unit 302 includes a light receiving element that outputs a light receiving signal by photoelectric conversion based on laser light that is received. As the light receiving element, for example, a single photon avalanche diode is applicable. The single photon avalanche diodes are also called SPADs and have a characteristic that electrons generated in response to incidence of one photon cause avalanche multiplication, thereby allowing a large current to flow. By using this characteristic of the SPADs, incidence of one photon can be detected with high sensitivity. A light receiving element applicable to the ranging sensor unit 302 is not limited to the SPADs, and an avalanche photodiode (APD) or a normal photodiode can also be applied.
The signal processing unit 51 calculates a distance D to a target 61, as a measurement target, on the basis of time t0 when laser light is emitted from the laser diode 12 and time t1 when the light is received by the ranging sensor unit 302.
In the above-described configuration, laser light 60 emitted from the laser diode 12 at timing of, for example, time t0 is reflected by the target 61, for example, and is received by the ranging sensor unit 302 at timing of time t1 as reflected light 62. The signal processing unit 51 obtains the distance D to the target 61 on the basis of the difference between time t1 at which the reflected light 62 is received by the ranging sensor unit 302 and time t0 at which the laser light has been emitted by the laser diode 12. The distance D is calculated by the following Equation (1) with a constant c as the speed of light (2.9979×108 [m/sec]).
D=(c/2)×(t1−t0) (1)
The signal processing unit 51 repeatedly executes the above process a plurality of times. The ranging sensor unit 302 may include a plurality of light receiving elements, and the distance D may be calculated on the basis of each light receiving timing at which the reflected light 62 is received by the respective light receiving elements. The signal processing unit 51 classifies time tm (referred to as light receiving time tm) from time t0 of the light emitting timing to the light receiving timing at which the light is received by the ranging sensor unit 302 on the basis of classes (bins) and generates a histogram.
Note that light received by the ranging sensor unit 302 at the light receiving time tm is not limited to the reflected light 62 which is the light emitted by the laser diode 12 and reflected by the target. For example, the ambient light around the ranging sensor unit 302 is also received by the ranging sensor unit 302.
The signal processing unit 51 counts the number of times of acquiring the light receiving time tm on the basis of the bins, obtains the frequency 310 for every bin, and generates a histogram. Here, the ranging sensor unit 302 also receives light other than the reflected light which is the light emitted from the laser diode 12 and reflected. Examples of such light other than the reflected light as a target include the ambient light. The portion indicated by an area 311 in the histogram includes ambient light components attributable to the ambient light. The ambient light is light randomly incident on the ranging sensor unit 302 and is noise with respect to the reflected light which is the target.
On the other hand, the reflected light as a target is light received depending on a specific distance and appears in the histogram as an active light component 312. A bin that corresponds to the frequency of a peak in the active light component 312 corresponds to the distance D to the target 61. The signal processing unit 51 can calculate the distance D to the target 61 in accordance with the above Equation (1) by acquiring representative time of the bin (for example, time at the center of the bin) as the above time t1. In this manner, by using the plurality of light reception results, it is possible to execute appropriate ranging for random noise.
Here,
(0.1 Comparative Example)
In order to facilitate understanding of the embodiments of the present disclosure, a comparative example will be described first.
[0.2 Configuration]
The signal processing unit 51 includes a phase locked loop (PLL) unit 21, a light emission waveform generating circuit (Tgen) 22 as a light emission waveform generating unit, a time digital converter (TDC) 23, a buffer B1, and a ranging sensor unit 302. The PLL unit 21 outputs a clock signal serving as a reference of the operation of the ranging system 70a. The PLL unit 21 includes, for example, a voltage-controlled oscillator that outputs a clock signal and controls an oscillation frequency of the clock signal on the basis of a phase difference between the clock signal that is output and a reference signal serving as a reference. The light emission waveform generating circuit 22 receives a trigger signal TRG′ as the input. The light emission waveform generating circuit 22 generates a light emission pattern signal for causing the laser diode 12 to emit light. The light emission waveform generating circuit 22 outputs a count start signal Cntstart simultaneously with the light emission pattern signal.
The TDC 23 outputs a digital signal corresponding to a time period starting from the timing at which the trigger signal TRG is input to the timing at which the ranging sensor unit 302 detects reflected light. The TDC 23 includes a counter for counting time, and counts time from the timing when the count start signal Cntstart is input to the timing when the ranging sensor unit 302 receives the reflected light.
The buffer B1 includes, for example, two complementary metal oxide semiconductor (CMOS) inverters connected in cascade. Alternatively, a differential buffer conforming to the low voltage differential signaling (LVDS) standards may be used. This similarly applies to buffers in the following description.
The driver 10 includes a buffer B2 and a drive unit (DRV) 24. The buffer B2 includes, for example, two CMOS inverters connected in cascade. The drive unit 24 outputs a drive signal for causing the laser diode 12 to emit light. More specifically, the drive unit 24 generates a drive current for causing the laser diode 12 to emit light and supplies the drive current that has been generated to the laser diode 12 as an output signal OUT.
An anode terminal of the laser diode 12 is connected to a power supply voltage VDD. A cathode terminal of the laser diode 12 is connected to the coupling unit 100c. Note that the anode terminal of the laser diode 12 may be connected to the coupling unit 100c, and the cathode terminal of the laser diode 12 may be connected to the ground. In this case, the drive current flows from the drive unit 24 to the laser diode 12 via the coupling unit 100c.
[0.3 Operation]
The delay time Tpd1 is not constant due to fluctuations in the power supply and the temperature environment and variations among individual drivers 10. For example, as indicated by a broken line H1 in
In the ranging system 70a, adjustment is necessary to match desired light emitting timing with the actual light emitting timing, and there is a possibility that the ranging accuracy decreases due to a propagation delay that fluctuates due to a change in the power supply and the temperature environment. In addition, a propagation delay within the signal processing unit 51 and a propagation delay in a substrate may also fluctuate, which results in a possibility that the ranging accuracy decreases. Therefore, it is necessary to improve the ranging accuracy in consideration of the fluctuation in the propagation delay time due to the power supply and the temperature environment and variations among individual drivers 10.
Next, a first embodiment of the present disclosure will be described.
[1.1 Configuration]
In
The signal processing unit 51 includes a ranging observation unit 52, a processing unit 53, and a ranging sensor unit 302. The processing unit 53 includes a light emission waveform generating circuit 22. The light emission waveform generating circuit 22, which is a light emission waveform generating unit, outputs a trigger signal TRG. The ranging observation unit 52 calculates a distance D to a target 61 on the basis of output timing of the trigger signal TRG and light receiving timing of the reflected light obtained by the ranging sensor unit 302. The processing unit 53 controls each unit of the signal processing unit 51. Since the ranging sensor unit 302 has already been described with reference to
The driver 10 includes a buffer B2, a TDC 23a, a drive unit 24, a logic unit 25, and a coupling unit 100f. The TDC 23a starts counting time by a trigger signal TRG and ends counting time when the drive unit 24 outputs an output signal OUT. The TDC 23a outputs digital data corresponding to a delay time which is a measurement result of counting time.
The logic unit 25 includes a storage unit 25M. The storage unit 25M stores digital data corresponding to a delay time which is a measurement result by the TDC 23a. The storage unit 25M includes, for example, a register. The storage unit 25M may be a memory. A clock signal Refclk serving as a reference of the operation of the TDC 23a is input to the coupling unit 100f.
In this embodiment, the processing unit 53 of the signal processing unit 51 is connected with the logic unit 25 of the driver 10 via the coupling units 100d and 100e. The processing unit 53 and the logic unit 25 can transmit and receive input/output signals I/O. Therefore, the processing unit 53 of the signal processing unit 51 can access the storage unit 25M of the logic unit 25. Therefore, the processing unit 53 can acquire the digital data corresponding to the delay time stored in the storage unit 25M of the logic unit 25.
[1.2 Operation]
The light emission waveform generating circuit 22 in the processing unit 53 of the signal processing unit 51 outputs the trigger signal TRG. The trigger signal TRG is input to the driver 10 via the coupling units 100a and 100b. The TDC 23a in the driver 10 starts counting time when the trigger signal TRG is input. The TDC 23a ends counting time when the drive unit 24 outputs the output signal OUT. The TDC 23a outputs the digital data corresponding to the delay time obtained by counting time. The TDC 23a sends the digital data corresponding to the delay time to the logic unit 25. The logic unit 25 stores the digital data corresponding to the delay time acquired from the TDC 23a in the storage unit 25M.
The processing unit 53 of the signal processing unit 51 accesses the logic unit 25 of the driver 10 via the coupling units 100d and 100e. The processing unit 53 acquires the digital data of the delay time stored in the storage unit 25M of the logic unit 25. The processing unit 53 sends the digital data of the delay time acquired from the storage unit 25M to the ranging observation unit 52. The ranging observation unit 52 calculates a distance D to a target 61 using the digital data corresponding to the delay time (hereinafter, it may be referred to as ranging.). That is, the ranging observation unit 52 performs ranging using the delay time. The ranging observation unit 52 subtracts the digital data corresponding to the delay time acquired from the storage unit 25M from a time period starting from timing at which the trigger signal TRG has been output to timing at which the ranging sensor unit 302 receives light. As a result, it is possible to know not the output timing of the trigger signal TRG but timing that is closer to the actual light emitting timing, and thus it is possible to remove the delay time attributable to an internal circuit of the driver 10. As a result, it is possible to obtain an effect of improving the accuracy of measurement of the distance D.
In
The TDC 23a starts counting time at the timing when the trigger signal TRG changes to the high level at a subsequent time, that is, at rise time Tt2. The TDC 23a counts time by counting the number of clock signals Refclk. Then, the TDC 23a ends counting time at the timing when the output signal OUT changes to the high level, that is, at rise time Td2. The TDC 23a sends digital data of the time count value “Tpd2” to the logic unit 25. The logic unit 25 stores the digital data of the time count value “Tpd2” in the storage unit 25M.
Thereafter, digital data of time count values of the TDC 23a is similarly stored in the storage unit 25M. Digital data of a time count value stored in the storage unit 25M is delay time from input of the trigger signal TRG to actual light emission by the laser diode 12. That is, it is possible to measure time Tpd1 and time Tpd2 which are delay times described with reference to
[1.2.1 First Operation Example]
An operation example of the entire ranging system 70b illustrated in
In
The driver 10 receives the trigger signal TRG and starts counting time by the TDC 23a (step S12). The driver 10 outputs a drive signal for causing the laser diode 12 to emit light, stops counting time by the TDC 23a at that timing, and obtains delay time (step S13). The driver 10 stores the digital data corresponding to the delay time in the storage unit 25M in the logic unit 25 (step S14).
The processing unit 53 of the signal processing unit 51 acquires digital data corresponding to the delay time from the storage unit 25M in the logic unit 25 (step S15).
Next, it is determined whether or not to end the process (step S16). If the process is not ended, the flow returns to step S11, and the above processes are performed (NO in step S16→S11). If the process is ended, the process ends (YES in step S16→S17).
Note that the above processes described with reference to
[1.2.2 Second Operation Example]
In
Next, it is determined whether or not to end the process (step S16). If the process is not ended, the flow returns to step S11, and the above processes are performed (NO in step S16→S11). If the process is ended, the process ends (YES in step S16→S17).
In step S14a, if the data of the delay time exceeds the determination reference value, the process proceeds to step S18. In this case, the signal processing unit 51 stops the operation of the drive unit 24, notifies the error information to the outside, and stores the error information in a predetermined register (step S18). The signal processing unit 51 confirms the error information stored in the register (step S19). Then, the process proceeds to step S16.
Note that the above processes described with reference to
[1.3 Effects]
By using the digital data of the delay time for calculating the distance D to the target 61, the ranging observation unit 52 can know not the output timing of the trigger signal TRG but timing that is closer to the actual light emitting timing. As a result, the ranging observation unit 52 can remove the delay time attributable to an internal circuit of the driver 10. More specifically, the distance D to the target 61 can be calculated by measuring delay time that is included in a time period starting from the output timing of the trigger signal TRG to the timing at which the light emitting element actually emits light and being based on the output timing of the trigger signal TRG, the light receiving timing of the reflected light obtained by the ranging sensor unit 302, and the delay time. As a result, it is possible to obtain an effect of improving the accuracy of measurement of the distance D. In addition, the delay time can be measured using the light emission pattern signal generated by the light emission waveform generating circuit 22a.
(1.4 First Modification of First Embodiment)
[1.4.1 Configuration]
The signal processing unit 51 of the ranging system 70b′ includes the storage unit 25M. A driver 10 does not include the storage unit 25M in a logic unit 25. Other configurations are similar to those of the ranging system 70b described with reference to
The storage unit 25M is only required to be provided in at least one of the signal processing unit 51 or the logic unit 25. The storage unit 25M may be provided in both the signal processing unit 51 and the logic unit 25, and the storage units 25M may exchange data.
[1.4.2 Operation]
A TDC 23a of the driver 10 sends digital data of a time count value to the logic unit 25. The logic unit 25 sends the digital data of the time count value to the signal processing unit 51. The signal processing unit 51 stores the digital data of the time count value in the storage unit 25M. Other operations are similar to the operations described by referring to
[1.4.3 Effects]
Since the storage unit 25M is provided in the signal processing unit 51, the area of a chip of the driver 10 can be reduced.
(1.5 Second Modification of First Embodiment)
[1.5.1 Configuration]
In
[1.5.2 Operation]
A processing unit 53 of the signal processing unit 51 outputs the trigger signal TRG′. The trigger signal TRG′ is input to the driver 10. When the trigger signal TRG′ is input via a buffer B2, the light emission waveform generating circuit 22a operates the drive unit 24.
The TDC 23a counts time from the timing at which the trigger signal TRG′ changes to a high level, that is, rise time, to the timing at which the output signal OUT output from the drive unit 24 changes to a high level, that is, rise time. The TDC 23a sends digital data of a time count value to the logic unit 25. The logic unit 25 stores the digital data of the time count value in the storage unit 25M. The subsequent operation is similar to the operations described by referring to
[1.5.3 Effects]
By using the digital data corresponding to the delay time for calculating the distance D to the target 61, the ranging observation unit 52 can know not the output timing of the trigger signal TRG but timing that is closer to the actual light emitting timing. As a result, the ranging observation unit 52 can remove the delay time attributable to an internal circuit of the driver 10. As a result, it is possible to obtain an effect of improving the accuracy of measurement of the distance D.
(1.6 Third Modification of First Embodiment)
[1.6.1 Configuration]
The signal processing unit 51 of the ranging system 70c′ includes the storage unit 25M. A driver 10 does not include the storage unit 25M in a logic unit 25. Other configurations are similar to those of the ranging system 70c described with reference to
[1.6.2 Operation]
A TDC 23a of the driver 10 sends digital data of a time count value to the logic unit 25. The logic unit 25 sends the digital data of the time count value to the signal processing unit 51. The signal processing unit 51 stores the digital data of the time count value in the storage unit 25M. Other operations are similar to the operations described by referring to
[1.6.3 Effects]
Since the storage unit 25M is provided in the signal processing unit 51, the area of a chip of the driver 10 can be reduced.
(1.7 Fourth Modification of First Embodiment)
[1.7.1 Configuration]
The ranging system 70c′ illustrated in
Other configurations in the driver 10 are similar to those described with reference to
[1.7.2 Operation]
The PLL unit 21a receives a clock signal Refclk as input and outputs a clock signal Refclk′ having a phase matching the phase of the clock signal Refclk. The clock signal Refclk′ is input to a TDC 1. The TDC 1 counts time on the basis of the clock signal Refclk′. The subsequent operation is similar to the operations described by referring to
[1.7.3 Effects]
By using the digital data of the delay time for calculating the distance D to the target 61, the ranging observation unit 52 can know not the output timing of the trigger signal TRG but timing that is closer to the actual light emitting timing. As a result, the ranging observation unit 52 can remove the delay time attributable to an internal circuit of the driver 10. As a result, it is possible to obtain an effect of improving the accuracy of measurement of the distance D.
(1.8 Fifth Modification of First Embodiment)
[1.8.1 Configuration]
In
The replica drive unit 24R outputs a replica output signal OUTrep, which simulates the output signal OUT output by the drive unit 24, on the basis of a signal output by the waveform generating circuit 22a. The replica drive unit 24R either constantly outputs the replica output signal OUTrep (in the case of a first operation example to be described later) or operates similarly to the drive unit 24 and outputs the replica output signal OUTrep which is the same as the output signal OUT (in the case of a second operation example to be described later).
Other configurations in the driver 10 are similar to those described with reference to
[1.8.2 Operation]
In
[1.8.2.1 Operation Example]
[1.8.3 Effects]
There are cases where it is not desired to provide a path branching to the TDC 23a on the output side of the original drive unit 24 and the laser diode 12. For example, the path branching to the TDC 23a may affect the current value of the output signal OUT to the laser diode 12. In this example, since the delay time is measured using the replica drive unit 24R, it is possible to obtain an effect that there is no such influence.
(1.9 Sixth Modification of First Embodiment)
[1.9.1 Configuration]
The ranging system 70e illustrated in
Other configurations in the driver 10 are similar to those described with reference to
[1.9.2 Operation]
In
Here, by adjusting the delay amount of the buffer BV, it becomes possible to match the timing at which the drive unit 24 outputs the output signal OUT to cause the laser diode 12 to emit light with the timing at which the replica output signal OUTrep from the buffer BV and the replica drive unit 24R is input to the TDC 23a.
The TDC 23a starts counting time from the time when the trigger signal TRG′ rises and ends counting time at the output timing of the replica output signal OUTrep output from the replica drive unit 24R. The TDC 23a sends digital data of a time count value to the logic unit 25. The logic unit 25 stores the digital data of the time count value in the storage unit 25M. The subsequent operation is similar to the operations described by referring to
[1.9.3 Effects]
There are cases where it is not desired to provide a path branching to the TDC 23a on the output side of the original drive unit 24 and the laser diode 12. For example, the path branching to the TDC 23a may affect the current value of the output signal OUT to the laser diode 12. In this example, since the delay time is measured using the replica drive unit 24R, it is possible to obtain an effect that there is no such influence.
In addition, by adjusting the delay amount of the buffer BV, it becomes possible to match the timing at which the laser diode 12 is caused to emit light with the timing at which the replica output signal OUTrep is input to the TDC 23a. As a result, the delay time can be measured more accurately, and the ranging accuracy can be improved.
(1.10 Seventh Modification of First Embodiment)
[1.10.1 Configuration]
A ranging system 70f illustrated in
Other configurations in the driver 10 are similar to those described with reference to
[1.10.2 Operation]
In
[1.10.3 Effects]
There are cases where it is not desired to provide a path branching to the TDC 23a on the output side of the original drive unit 24 and the laser diode 12. For example, the path branching to the TDC 23a may affect the current value of the output signal OUT to the laser diode 12. In this example, since the delay time is measured using the replica drive unit 24R, it is possible to obtain an effect that there is no such influence.
Furthermore, by adjusting the delay amount of the buffer BV on the basis of the temperature of the driver 10, it is possible to match the timing at which the laser diode 12 is caused to emit light with the timing at which the replica output signal OUTrep is input to the TDC 23a. As a result, the delay time can be measured more accurately, and the ranging accuracy can be improved.
(1.11 Eighth Modification of First Embodiment)
[1.11.1 Configuration]
The ranging system 70g illustrated in
Other configurations in the driver 10 are similar to those described with reference to
[1.11.2 Operation]
In
The TDC 23a counts time from the timing at which a trigger signal TRG′ changes to a high level, that is, rise time, to the timing at which the output signal 220 of the buffer B3 changes to a high level, that is, rise time. The TDC 23a sends digital data of a time count value to the logic unit 25. The logic unit 25 stores the digital data of the time count value in the storage unit 25M. The subsequent operation is similar to the operations described by referring to
[1.11.3 Effects]
In a case where the output signal OUT of the drive unit 24 cannot be used due to mounting circumstances of the driver 10, it is possible to improve the ranging accuracy by counting time using a signal on the input side of the drive unit 24.
(1.12 Ninth Modification of First Embodiment)
[1.12.1 Configuration]
In
In a case where a plurality of drive units 241 to 24N is included, it is conceivable to measure the delay time for all the drive units 241 to 24N. However, in that case, wiring becomes complicated, which is not realistic. Therefore, it is conceivable to set a part of the plurality of drive units 241 to 24N as a measurement target. The measurement result of the drive unit as the measurement target can be used for ranging by all the other drive units.
The ranging system 70h illustrated in
The ranging system 70h′ illustrated in
The ranging system 70h″ illustrated in
[1.12.2 Operation]
The ranging system 70h illustrated in
The ranging system 70h′ illustrated in
The ranging system 70h″ illustrated in
[1.12.3 Effects]
In a case where a plurality of drive units 241 to 24N is included, by using an output signal before branching or by using some drive units as measurement targets, it is possible to prevent the wiring from becoming complicated, to measure the delay time, and to improve the ranging accuracy.
(1.13 Tenth Modification of First Embodiment)
[1.13.1 Configuration]
The ranging system 70i illustrated in
[1.13.2 Operation]
In the ranging system 70i illustrated in
[1.13.3 Effects]
In the ranging system 70i illustrated in
(1.14 Eleventh Modification of First Embodiment)
[1.14.1 Configuration]
The ranging system 70j illustrated in
Other configurations in the driver 10 are similar to those described with reference to
[1.14.2 Operation]
In the ranging system 70j illustrated in
[1.14.3 Effects]
Since the ranging system 70j illustrated in
Next, a second embodiment of the present disclosure will be described. In the first embodiment, the driver 10 measures the delay time. Meanwhile, in the second embodiment, a signal processing unit 51 measures the delay time.
[2.1 Configuration]
The signal processing unit 51 includes a PLL unit 21, a light emission waveform generating circuit (Tgen) 22 as a light emission waveform generating unit, TDCs 23 and 23a, buffers B1, B5, and B6, and a ranging sensor unit 302. The light emission waveform generating circuit 22 outputs trigger signal TRG. The trigger signal TRG is a light emission pattern signal for causing the laser diode 12 to emit light. The light emission waveform generating circuit 22 outputs the trigger signal TRG and outputs a count start signal Cntstart. The buffer B5 receives the trigger signal TRG output from the buffer B1 as input and outputs the trigger signal TRG toward the TDC 23a. The buffer B6 receives a signal input from the coupling unit 100g and outputs the signal toward the TDC 23a. The buffers B5 and B6 include, for example, two CMOS inverters connected in cascade.
Like the TDC 23, the TDC 23a includes a counter for counting time. The TDC 23a starts counting time when the signal output from the buffer B5 is input. The TDC 23a ends the counting time when the signal output from the buffer B6 is input. Although the timing at which the laser diode 12 actually emits light is unknown, in this example, the time until the timing immediately before the light emission, which is close to the light emitting timing, is measured as a delay time. That is, the TDC 23a functions as a measurement unit that measures a delay time that is a time included in the time from the timing at which the trigger signal TRG for causing the laser diode 12 to emit light is output to the timing at which the laser diode 12 actually emits light. Other configurations of the signal processing unit 51 are similar to those of the ranging system 70a described with reference to
The driver 10 includes buffers B2 and B4 and a drive unit 24. A signal on the input side of the drive unit 24 is branched. The branched signal is derived from the light emitting timing and is input to the buffer B4. The buffer B4 returns the branched signal to the signal processing unit 51. The buffer B4 receives the signal output from the buffer B2 and outputs the signal to the signal processing unit 51 via the coupling units 100g and 100h. Other configurations of the driver 10 are similar to those of the ranging system 70a described with reference to
[2.2 Operation]
The TDC 23a functioning as a measurement unit bifurcates the transmission path of the trigger signal TRG in the signal processing unit 51 and starts counting time from the rise timing of a returned signal. Then, the TDC 23a bifurcates the transmission path of the trigger signal TRG on the input side of the drive unit 24, ends counting time at the rise timing of the signal obtained by returning the trigger signal TRG, and sets the time count value as the delay time. That is, the trigger signal TRG for causing the laser diode 12 to emit light is output, and ranging is performed using the delay time generated by a delay element in the path extending to a point where the trigger signal TRG actually drives the laser diode 12. That is, a time difference between signals returned through different systems is measured as a delay time, and ranging is performed using the delay time.
An operation example of the entire ranging system 70k illustrated in
In
The signal processing unit 51 measures a time difference between the signal derived from the light emitting timing and the trigger signal TRG, that is, a delay time (step S23). The signal processing unit 51 adjusts the count start timing for ranging using the time difference obtained by the measurement, that is, the delay time, and performs ranging (step S24).
Specifically, in the TDC 23a, the count start timing for ranging is delayed by a time corresponding to the delay time. That is, the TDC 23a starts counting time after elapse of the time corresponding to the delay time from the output timing of the trigger signal TRG and ends counting time at the light receiving timing of the reflected light obtained by the ranging sensor unit 302. The signal processing unit 51 calculates the distance to the target 61 on the basis of the time count result of the TDC 23a. As a result, ranging can be performed by adjusting the start timing of counting time.
Next, it is determined whether or not to end the process (step S25). If the process is not ended, the flow returns to step S21, and the above process is performed (NO in step S25→S21). If the process is ended, the process ends (YES in step S25→S26).
The above processes described with reference to
Note that, similarly to the first embodiment, a storage unit 25M may be provided, and digital data corresponding to the delay time measured in step S23 may be stored in the storage unit 25M. In this case, the count start timing for ranging is adjusted in step S24 using the digital data of the delay time stored in the storage unit 25M.
Here, an exemplary calculation of delay time by the ranging system 70k according to the second embodiment illustrated in
A delay time caused by a path through which the trigger signal TRG is input to the TDC 23a via the buffers B1 and B6 in the signal processing unit 51 is denoted by T1. That is, the difference between the time when the trigger signal TRG is output and the time when a signal TRG_SPD corresponding to the trigger signal TRG is input to the TDC 23a is the delay time T1. The delay time T1 can be expressed by the following Equation (2).
T1=t_io1+t_ldd+t_io1′+t_io2 (2)
In addition, a delay time caused by a path in which the trigger signal TRG travels from the signal processing unit 51 to the driver 10 and returns to the signal processing unit 51 via the driver 10 is denoted by T2. The difference between the time when the trigger signal TRG is output and the time when the signal TRG_DRV derived from the trigger signal TRG is input to the TDC 23a is the delay time T2. The delay time T2 can be expressed by the following Equation (3).
T2=t_io1+t_io2 (3)
On the basis of Equations (2) and (3), the difference between the delay time T1 and the delay time T2 is expressed by the following Equation (4).
T1−T2=t_ldd+t_io1′ (4)
Equation (4) is equivalent to a delay time Tdly measured by the TDC 23a. The delay time Tdly is input to a light emission waveform generating circuit 22 which is a light emission waveform generating unit. The light emission waveform generating circuit 22 delays the rise timing of a count start signal Cntstart by a time corresponding to the delay time Tdly. The delay time Tdly is a difference between the delay time in the signal processing unit 51 and the delay time in the driver 10, and the accuracy of ranging can be improved by using the delay time Tdly.
Furthermore, rise timing of main signals of the ranging system 70k illustrated in
As illustrated in
The light emission waveform generating circuit 22 can use the delay time Tdly to adjust the next or subsequent rise timing of the count start signal Cntstart. That is, as indicated by an arrow Y in
[2.3 Effects]
By using the delay time Tdly which is a difference between the delay time in the signal processing unit 51 and the delay time in the driver 10, the count start time of the TDC 23a can be matched with or brought closer to the actual light emitting timing. As a result, the accuracy of ranging can be further improved.
(2.4 First Modification of Second Embodiment)
[2.4.1 Configuration]
In the ranging system 70k of the second embodiment described with reference to
[2.4.2 Operation]
The ranging system 70m according to the first modification of the second embodiment illustrated in
[2.4.3 Effects]
In the ranging system 70m according to the first modification of the second embodiment, a subsequent stage of the drive unit 24, that is, a point close to the laser diode 12 is set as a measurement target. Therefore, the accuracy of ranging can be further improved.
(2.5 Second Modification of Second Embodiment)
[2.5.1 Configuration]
In the ranging system 70m of the first modification of the second embodiment described with reference to
[2.5.2 Operation]
The attenuator 28 attenuates the signal level to a signal level that a buffer B4 can handle. The signal attenuated by the attenuator 28 is output to the signal processing unit 51 via the buffer B4. Other operations are the same as those of the ranging system 70k of the second embodiment, and thus description thereof will be omitted.
[2.5.3 Effects]
The attenuator 28 can attenuate to a signal level that the buffer B4 can handle.
(2.6 Third Modification of Second Embodiment)
[2.6.1 Configuration]
In the ranging system 70k of the second embodiment described with reference to
[2.6.2 Operation]
The trigger signal TRG output from the light emission waveform generating circuit 22 is input to the TDC 23a without passing through the buffer B1. Therefore, the delay time due to the buffer B1 can be removed. Other operations are the same as those of the ranging system 70k of the second embodiment, and thus description thereof will be omitted.
[2.6.3 Effects]
Since the trigger signal TRG is directly input to the TDC 23a, the delay time due to the buffer B1 can be removed to measure the delay time.
(2.7 Fourth Modification of Second Embodiment)
[2.7.1 Configuration]
As illustrated in
[2.7.2 Operation]
The TDC 23 starts counting time at the rise timing of the trigger signal TRG. The TDC 23 ends the counting time at the rise timing of the output signal of the buffer B5. The delay time can be measured by this counting time. In addition, the TDC 23 starts counting time at the rise timing of the trigger signal TRG and ends counting time at the timing when the ranging sensor unit 302 receives light. The delay time is subtracted from the time obtained from this counting time. As a result, it is possible to know not the output timing of the trigger signal TRG but timing that is closer to the actual light emitting timing, and thus it is possible to remove the delay time attributable to an internal circuit of the driver 10. Other operations are the same as those of the ranging system 70k of the second embodiment, and thus description thereof will be omitted.
[2.7.3 Effects]
In the ranging system 70r according to the fourth modification of the second embodiment, a subsequent stage of a drive unit 24, that is, a point close to a laser diode 12 is set as a measurement target. Therefore, the accuracy of ranging can be further improved.
(2.8 Fifth Modification of Second Embodiment)
[2.8.1 Configuration]
As illustrated in
A drive unit 24 includes a transistor Tr2. The gate of the transistor Tr2 is connected to the output of the buffer B2.
Note that, as illustrated in
[2.8.2 Operation]
The transistor Tr2 in the drive unit 24 is turned on by an output signal of the buffer B2, and a current flows through the laser diode 12. As a result, the laser diode 12 emits light. In addition, the transistor Tr1 is turned on, and a signal having passed through the dummy load 29 is input to the buffer B4. As a result, a signal to the buffer B4 is output after elapse of a time corresponding to a time required for a current to flow through the laser diode 12 and to actually emit light. Other operations are the same as those of the ranging system 70k of the second embodiment, and thus description thereof will be omitted.
[2.8.3 Effects]
By disposing the dummy load 29, it becomes possible to return, to the signal processing unit 51, a signal in consideration of a delay time until a current flows through the laser diode 12 and the laser diode 12 emits light. As a result, the accuracy of ranging can be further improved.
(2.9 Sixth Modification of Second Embodiment)
[2.9.1 Configuration]
As illustrated in
Note that, as illustrated in
[2.9.2 Operation]
The transistor Tr21 in the drive unit 241 and the transistor Tr22 in the drive unit 242 are turned on by an output signal of a buffer B2, and a current flows in the laser diodes 121 and 122. As a result, the laser diodes 121 and 122 emit light. In addition, the transistor Tr1 is turned on, and a signal to the buffer B4 is output after elapse of a time corresponding to a time required for a current to flow through the laser diode 12 and to actually emit light. Other operations are the same as those of the ranging system 70k of the second embodiment, and thus description thereof will be omitted.
[2.9.3 Effects]
According to the ranging system 70t of the present example, even in a case where a plurality of laser diodes is included, the delay time can be measured, and the accuracy of ranging can be improved.
Note that one output side of the plurality of drive units 241 and 242 may be bifurcated without providing the dummy load 29, and the output signal may be returned to the signal processing unit 51 side. Furthermore, instead of disposing the dummy load 29, a replica drive unit that simulates the drive unit 24 may be disposed, and an output signal of the replica drive unit may be returned to the signal processing unit 51 side.
(2.10 Seventh Modification of Second Embodiment)
[2.10.1 Configuration]
As illustrated in
[2.10.2 Operation]
The transistor Tr21 in the drive unit 241 and the transistor Tr22 in the drive unit 242 are turned on by an output signal of a buffer B2, and a current flows in the laser diodes 121 and 122. As a result, the laser diodes 121 and 122 emit light. Other operations are the same as those of the ranging system 70k of the second embodiment, and thus description thereof will be omitted.
[2.10.3 Effects]
According to the ranging system 70u of the present example, even in a case where a plurality of laser diodes is included, the delay time can be measured, and the accuracy of ranging can be improved.
(2.11 Eighth Modification of Second Embodiment)
[2.11.1 Configuration]
As illustrated in
[2.11.2 Operation]
In the ranging system 70v illustrated in
The TDCs 23a and 23b start counting time from the rise of a trigger signal TRG. The TDC 23a ends counting time at the rise timing of a drive signal of the drive unit 241 input via the buffer B41 and the buffer B51. The TDC 23b ends counting time at the rise timing of a drive signal of the drive unit 242 input via the buffer B42 and the buffer B52. The TDC 23a measures a delay time Tdly1. The TDC 23b measures a delay time Tdly2. Other operations are the same as those of the ranging system 70k of the second embodiment, and thus description thereof will be omitted.
[2.11.3 Effects]
According to the ranging system 70v of the present example, the delay time can be individually measured for each of the plurality of drive units, and the accuracy of ranging can be improved.
(2.12 Ninth Modification of Second Embodiment)
[2.12.1 Configuration]
The driver 10 includes the multiplexer (MUX) 30, and the signal processing unit 51 includes the multiplexer (MUX) 31. The multiplexer 30 selects and inputs an output signal of a drive unit 241 and an output signal of a drive unit 242. The multiplexer 31 selects a TDC 23a or a TDC 23b. The multiplexer 31 inputs an output signal of a buffer B5 to one of the TDC 23a or the TDC 23b that is selected. The multiplexer 30 and the multiplexer 31 can be simultaneously switched.
[2.12.2 Operation]
In the ranging system 70w illustrated in
The TDCs 23a and 23b start counting time from the rise of a trigger signal TRG. The TDC 23a and the TDC 23b end counting time by an output signal of a multiplexer 31. Other operations are the same as those of the ranging system 70k of the second embodiment, and thus description thereof will be omitted.
[2.12.3 Effects]
According to the ranging system 70w of the present example, by using the multiplexer, it is possible to suppress an increase in the number of wires between the signal processing unit 51 and the driver 10 even in a case where the delay time is individually measured for a plurality of drive units.
(2.13 Tenth Modification of Second Embodiment)
[2.13.1 Configuration]
In the ranging system 70x, the time estimated using the delay time measured for some laser diodes among a plurality of laser diodes is regarded as the delay time for other laser diodes.
The ranging system 70x includes a plurality of laser diodes and includes multiplexers 30 and 31 to perform switching as in the ranging system 70w described with reference to
An average value of the delay time measured for the laser diode 12F and the delay time measured for the laser diode 12L is obtained, and the delay time of the average value that has been obtained can be used for ranging using all the laser diodes.
In addition, a value obtained by performing linear interpolation on delay times measured for the laser diodes may be used for ranging. For example, a value, which is obtained by performing linear interpolation on delay times of laser diodes at several positions of two-dimensionally arrayed laser diodes, is used for ranging.
[2.13.2 Operation]
If the delay time of the LD (1, 1) is the shortest and the delay time of the LD (11, 8) is the longest, the LD (1, 1) and the LD (11, 1) are set as measurement targets. The delay time of the other laser diodes can be estimated by performing linear interpolation between the delay time of the LD (1, 1) and the delay time of the LD (11, 1). If the wiring length from the light emission waveform generating circuit 22 is known, the estimation can be made by performing weighting depending on the length.
[2.13.3 Effects]
According to the ranging system 70x of the tenth modification of the second embodiment, by performing linear interpolation or the like, it is possible to improve the accuracy of ranging without setting all the laser diodes included in the LD array as measurement targets.
(2.14 Eleventh Modification of Second Embodiment)
[2.14.1 Configuration]
The buffer B7 includes two CMOS inverters connected in cascade like other buffers. The PLL unit 21a receives a clock signal Refclk as the input. The light emission waveform generating circuit 22a operates a drive unit 24. Other configurations are similar to those of the ranging system 70k described with reference to
[2.14.2 Operation]
The PLL unit 21a receives a clock signal Refclk as input and outputs a clock signal Refclk′ having a phase matching the phase of the clock signal Refclk. When a trigger signal TRG is input from a signal processing unit 51, the light emission waveform generating circuit 22a operates the drive unit 24. The drive unit 24 outputs an output signal OUT. Furthermore, the path of the output signal OUT output from the drive unit 24 branches, and the output signal OUT is sent to the signal processing unit 51 via a buffer B4.
[2.14.3 Effects]
A signal in consideration of the delay time by the light emission waveform generating circuit 22a can be returned to the signal processing unit 51. As a result, the accuracy of ranging can be further improved.
The LDD chip 1000 is a semiconductor chip and is coupled with an external circuit by wire bonding to a plurality of pads 1001 arranged in a peripheral portion. For example, a power supply voltage VDD is supplied to the LDD chip 1000 externally via a pad 1001.
In the example of
An LD array 1200b is disposed, for example, in the area of a broken line H2. In that case, it is preferable that each drive unit 24 of the driver 10 be arranged immediately below the LD array 1200b. With this arrangement, it is possible to bring the positions of laser diodes included in the LD array 1200b and the positions of the drive units corresponding thereto close to each other. As a result, it is possible to obtain an effect of facilitating wiring between the laser diode and the drive unit.
It is preferable that the TDC 23 provided in the driver 10 in the first embodiment be arranged in the vicinity of the LD array 1200b. It is preferable that the TDC 23 be disposed, for example, in the area indicated by a broken line H3. As a result, it is possible to obtain an effect of facilitating the wiring for extracting an output signal OUT output from the drive unit 24 and inputting the output signal OUT to the TDC 23.
Note that it is preferable that the temperature sensor 26 provided in the ranging system 70f illustrated in
A ranging system includes a drive unit 24, a ranging sensor unit 302 that is a sensor unit, a TDC 23a that is a measurement unit, and a ranging observation unit 52 that is a processing unit. The drive unit 24 outputs a drive signal for causing the laser diode 12, which is a light emitting element, to emit light to irradiate a target 61 with the light. The ranging sensor unit 302 detects reflected light from the target 61. The TDC 23a measures a delay time that is a time included in the time from the timing at which a trigger signal for causing the light emitting element to emit light is output to the timing at which the light emitting element actually emits light. The ranging observation unit 52 calculates a distance to a target 61 on the basis of the output timing of the trigger signal, light receiving timing of the reflected light obtained by the ranging sensor unit 302, and the delay time.
As a result, ranging can be performed using the delay time having been measured, and the accuracy of ranging can be further improved.
The TDC 23a as the measurement unit starts counting time from the rise timing of the trigger signal, ends counting time at the output timing of a drive signal to the laser diode 12 as the light emitting element, and uses the time count value as the delay time.
As a result, it is possible to measure the delay time which is a time included in the time until the timing at which the laser diode 12, as the light emitting element, actually emits light.
The ranging system may include a light emission waveform generating circuit 22a which is a light emission waveform generating unit. The light emission waveform generating circuit 22a generates a light emission pattern signal for causing the light emitting element to emit light.
As a result, the delay time can be measured using the light emission pattern signal generated by the light emission waveform generating circuit 22a.
The ranging system may include a replica drive unit 24R imitating the drive unit 24. The TDC 23a, as the measurement unit, ends counting time at the output timing of a signal of the replica drive unit 24R.
As a result, the accuracy of ranging can be improved using the replica drive unit 24R.
The ranging system may include a buffer BV which is a delay amount adjusting unit. The delay time of the signal passing through the replica drive unit 24R can be adjusted by the buffer BV that is the delay amount adjusting unit.
As a result, even in a case where the replica drive unit 24R is used, the accuracy of ranging can be improved.
The ranging system may include a temperature sensor 26 that detects a temperature. The delay amount of the buffer BV, which is the delay amount adjusting unit, is adjusted on the basis of the temperature detected by the temperature sensor 26.
As a result, the accuracy of ranging can be enhanced even in a case where the temperature changes.
The TDC 23a, which is the measurement unit, may start counting time from the rise timing of the trigger signal, end counting time at the output timing of a signal on the input side of the drive unit 24, and set the time count value as the delay time.
As a result, even in a case where the output signal of the drive unit 24 cannot be used, it is possible to measure the delay time.
The ranging system may include a plurality of drive units corresponding to a plurality of light emitting elements. The TDC 23a, which is the measurement unit, starts counting time from the rise timing of the trigger signal, ends counting time at the output timing of one drive signal of the plurality of drive units, and sets the time count value as the delay time.
As a result, it is possible to measure the delay time using one drive signal of the plurality of drive units corresponding to the plurality of light emitting elements and use the delay time that has been measured when ranging using another light emitting element is performed.
The ranging system may include a selector 27 that selects one of drive signals output from the plurality of drive units. The TDC 23a as the measurement unit ends counting time at the output timing of the drive signal selected by the selector 27 and sets the time count value as the delay time.
As a result, in a case where the delay time is measured using respective drive signals of the plurality of drive units, it is possible to prevent the wiring from becoming complicated.
The ranging system may include a plurality of TDCs 23a and 23b corresponding to a plurality of drive units 24.
As a result, for example, the ranging can be performed using an average value of delay times measured by the two TDCs 23a and 23b, and the ranging accuracy can be further improved.
The ranging system may include a storage unit 25M that stores data corresponding to the delay time. The ranging observation unit 52, which is the processing unit, performs a process of calculating the distance to the target using the data stored in the storage unit 25M.
As a result, ranging can be performed using the data stored in the storage unit 25M.
The ranging system may include a signal processing unit 51 including the ranging observation unit 52 as the processing unit and a driver 10 including the drive unit 24, and a storage unit 25M may be provided in at least one of the driver 10 or the signal processing unit 51.
As a result, ranging can be performed using the data stored in the storage unit 25M.
The ranging observation unit 52, which is the processing unit, may start counting time after a time corresponding to the delay time from the output timing of the trigger signal TRG, end counting time at the light receiving timing of the reflected light, and calculate the distance to the target 61 on the basis of the time count result.
As a result, ranging can be performed by adjusting the start timing of counting time.
The ranging system may include a signal processing unit 51 including the ranging observation unit 52 as the processing unit and a driver 10 including the drive unit 24, and the TDC 23a as the measurement unit may be provided in the signal processing unit 51. The TDC 23a bifurcates the transmission path of the trigger signal in the signal processing unit 51, starts counting time from the rise timing of a signal obtained by returning the trigger signal, bifurcates the transmission path of the trigger signal on the input side of the drive unit 24, ends counting time at the rise timing of the signal obtained by returning the trigger signal, and sets the time count value as the delay time.
As a result, the delay time can be measured in the signal processing unit 51.
The ranging system may include a signal processing unit 51 including the ranging observation unit 52 as the processing unit and a driver 10 including the drive unit 24, and the TDC 23a as the measurement unit may be provided in the signal processing unit 51. The TDC 23a bifurcates the transmission path of the trigger signal in the signal processing unit 51, starts counting time from the rise timing of a signal obtained by returning the trigger signal, bifurcates the transmission path of the trigger signal on the output side of the drive unit, ends counting time at the rise timing of the signal obtained by returning the trigger signal, and sets the time count value as the delay time.
As a result, the delay time can be measured in the signal processing unit 51.
The ranging system may include an attenuator 28 that bifurcates on the output side of the drive unit 24 and attenuates the signal level of a signal obtained by returning the trigger signal. A buffer B4 that receives the signal attenuated by the attenuator 28 as input and outputs the signal to the signal processing unit 51 may be included.
As a result, the attenuator 28 can attenuate the signal level to a signal level that the buffer B4 can handle.
The ranging system may include a dummy load 29 that receives, as the input, a signal branched from the transmission path of the trigger signal on the input side of the drive unit 24. The dummy load 29 has a time constant corresponding to the time required for a current to flow through the light emitting element to actually emit light and may output a signal, which has passed through the dummy load 29, to the signal processing unit 51 from the driver 10 as a signal obtained by returning the trigger signal.
By disposing the dummy load 29, it becomes possible to return, to the signal processing unit 51, a signal in consideration of a delay time until a current flows through the laser diode 12 and the laser diode 12 emits light. As a result, the accuracy of ranging can be further improved.
A plurality of drive units corresponding to a plurality of light emitting elements and a plurality of TDCs 23a and 23b provided corresponding to the plurality of drive units may be included. Each of the plurality of TDCs 23a and 23b bifurcates the transmission path of the trigger signal on one of the output sides of the plurality of drive units, ends counting time at the rise timing of the signal obtained by returning the trigger signal, and sets the time count value as the delay time.
As a result, even in a case where a plurality of drive units corresponding to a plurality of light emitting elements is included, the accuracy of ranging can be improved.
The ranging system may include a first multiplexer 30 and a second multiplexer 31. The first multiplexer 30 selects and outputs a signal output from the plurality of drive units. The second multiplexer 31 inputs the output of the first multiplexer 30 to a selected one of the plurality of TDCs 23a and 23b.
As a result, even in a case where a plurality of drive units corresponding to a plurality of light emitting elements is included, the accuracy of ranging can be improved.
In a case where the ranging system includes a plurality of light emitting elements, the delay time for light emitting elements disposed in the middle may be obtained by interpolation of two delay times.
As a result, even when the delay time is not measured for all of the plurality of light emitting elements, the accuracy of ranging can be further improved using the delay time obtained by interpolation.
A driver of a light emitting element includes a drive unit 24 and a TDC 23a as the measurement unit. The drive unit 24 outputs a drive signal for causing the light emitting element to emit light to irradiate the target with light. The TDC 23a measures a delay time that is a time included in the time from the timing at which a trigger signal for causing the light emitting element to emit light is input to the timing at which the light emitting element actually emits light. Data corresponding to the delay time measured by the TDC 23a is output and stored in the storage unit 25M, for example.
As a result, ranging can be performed using the data corresponding to the delay time, and the accuracy of ranging can be further improved.
Note that the effects described herein are merely examples and are not limiting, and other effects may also be achieved. In addition, the configurations described herein can be combined as appropriate.
Note that the present technology can also have the following configurations.
(1)
A ranging system comprising:
a drive unit that causes a light emitting element to emit light and outputs a drive signal for irradiating a target with light;
a sensor unit that detects reflected light from the target;
a measurement unit that measures a delay time that is included in a time from timing at which a trigger signal for causing the light emitting element to emit light is output to timing at which the light emitting element actually emits light; and
a processing unit that performs a process of calculating a distance to the target on a basis of output timing of the trigger signal, light receiving timing of the reflected light obtained by the sensor unit, and the delay time.
(2)
The ranging system according to (1),
wherein the measurement unit starts counting time from rise timing of the trigger signal, ends counting time at output timing of the drive signal to the light emitting element, and sets the time count value as the delay time.
(3)
The ranging system according to (1) or (2), further comprising a light emission waveform generating unit that generates a light emission pattern signal for causing the light emitting element to emit light.
(4)
The ranging system according to (2), further comprising
a replica drive unit that simulates the drive unit,
wherein the measurement unit ends counting time at output timing of a signal by the replica drive unit.
(5)
The ranging system according to (4), further comprising a delay amount adjusting unit that adjusts a delay time of the signal passing through the replica drive unit.
(6)
The ranging system according to (5), further comprising a temperature sensor that detects a temperature, wherein a delay amount of the delay amount adjusting unit is adjusted on a basis of the temperature detected by the temperature sensor.
(7)
The ranging system according to (2),
wherein the measurement unit starts counting time from the rise timing of the trigger signal, ends counting time at output timing of a signal on an input side of the drive unit, and sets the time count value as the delay time.
(8)
The ranging system according to (2), further comprising a plurality of the drive units corresponding to a plurality of the light emitting elements,
wherein the measurement unit starts counting time from the rise timing of the trigger signal, ends counting time at output timing of one of the drive signals of the plurality of the drive units, and sets the time count value as the delay time.
(9)
The ranging system according to (2), further comprising a selector that selects one of the drive signals output from a plurality of the drive units,
wherein the measurement unit ends counting time at output timing of the drive signal selected by the selector and sets the time count value as the delay time.
(10)
The ranging system according to (2), further comprising a plurality of the measurement units corresponding to a plurality of the drive units.
(11)
The ranging system according to any one of (1) to (10), further comprising
a storage unit that stores data corresponding to the delay time,
wherein the processing unit performs the process of calculating the distance to the target using the data stored in the storage unit.
(12)
The ranging system according to (11), further comprising a signal processing unit including the processing unit; and a driver including the drive unit,
wherein the storage unit is provided in at least one of the driver and the signal processing unit.
(13)
The ranging system according to any one of (1) to (12),
wherein the processing unit starts counting time after a time corresponding to the delay time from the output timing of the trigger signal, ends counting time at the light receiving timing of the reflected light, and calculates the distance to the target on a basis of the time count result.
(14)
The ranging system according to (2), further comprising: a signal processing unit including the processing unit; and a driver including the drive unit,
wherein the measurement unit is provided in the signal processing unit, and
the measurement unit bifurcates a transmission path of the trigger signal in the signal processing unit, starts counting time from rise timing of a signal obtained by returning the trigger signal, bifurcates the transmission path of the trigger signal on an input side of the drive unit, ends counting time at rise timing of a signal obtained by returning the trigger signal, and sets the time count value as the delay time.
(15)
The ranging system according to (2), further comprising: a signal processing unit including the processing unit; and a driver including the drive unit,
wherein the measurement unit is provided in the signal processing unit, and
the measurement unit bifurcates a transmission path of the trigger signal in the signal processing unit, starts counting time from rise timing of a signal obtained by returning the trigger signal, bifurcates the transmission path of the trigger signal on an output side of the drive unit, ends counting time at rise timing of a signal obtained by returning the trigger signal, and sets the time count value as the delay time.
(16)
The ranging system according to (15), further comprising:
an attenuator that bifurcates on the output side of the drive unit and attenuates a signal level of a signal obtained by returning the trigger signal; and
a buffer that receives a signal attenuated by the attenuator as input and outputs the signal to the signal processing unit.
(17)
The ranging system according to (14), further comprising
a dummy load that receives, as input, a signal branched from the transmission path of the trigger signal on the input side of the drive unit,
wherein the dummy load has a time constant corresponding to a time required for a current to flow through the light emitting element to actually emit light, and
a signal which has passed through the dummy load is output from the driver to the signal processing unit as a signal obtained by returning the trigger signal.
(18)
The ranging system according to (2), further comprising: a plurality of the drive units corresponding to a plurality of the light emitting elements; and a plurality of the measurement units provided in correspondence to the plurality of the drive units,
wherein each of the plurality of measurement units bifurcates the transmission path of the trigger signal on a respective output sides of the plurality of drive units, ends counting time at rise timing of a signal obtained by returning the trigger signal, and sets the time count value as the delay time.
(19)
The ranging system according to (18), further comprising: a first multiplexer that selects and outputs one of output signals of the plurality of drive units; and a second multiplexer that inputs the output of the first multiplexer to a selected one of the plurality of the measurement units.
(20)
The ranging system according to (18) or (19),
wherein the plurality of the light emitting elements includes a first light emitting element and a second light emitting element, and
the delay time for a light emitting element provided between the first light emitting element and the second light emitting element is obtained by interpolation between the delay time of the first light emitting element and the delay time of the second light emitting element.
(21)
A driver of a light emitting element, comprising:
a drive unit that causes the light emitting element to emit light and outputs a drive signal for irradiating a target with light; and
a measurement unit that measures a delay time that is included in a time from timing at which a trigger signal for causing the light emitting element to emit light is input to timing at which the light emitting element actually emits light,
wherein the driver outputs data corresponding to the delay time measured by the measurement unit.
(22)
The driver of the light emitting element according to (21), further including a storage unit that stores data corresponding to the delay time measured by the measurement unit, in which the driver outputs the data stored in the storage unit.
10 DRIVER
11 CONTROLLER
12 LASER DIODE
21, 21a PLL UNIT
22, 22a LIGHT EMISSION WAVEFORM GENERATING CIRCUIT
23, 23a, 23a1, 23b1 TDC
24 DRIVE UNIT
24R REPLICA DRIVE UNIT
25 LOGIC UNIT
25M STORAGE UNIT
26 TEMPERATURE SENSOR
27 SELECTOR
28 ATTENUATOR
29 DUMMY LOAD
30, 31 MULTIPLEXER
51 SIGNAL PROCESSING UNIT
52 RANGING OBSERVATION UNIT
53 PROCESSING UNIT
61 TARGET
70, 70a to 70k, 70m, 70p to 70y RANGING SYSTEM
12, 121 to 12N LASER DIODE
24, 241 to 24N DRIVE UNIT
302 RANGING SENSOR UNIT
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/032471 | 8/27/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62893041 | Aug 2019 | US | |
| 62893405 | Aug 2019 | US |
