JP6805504B2 - Distance measuring device, mobile device and distance measuring method - Google Patents

Description

The present invention relates to a distance measuring device, a moving body device, and a distance measuring method.

In recent years, a device that receives light projected from a light projecting system and reflected by an object and measures the distance to the object has been actively developed.

For example, Patent Document 1 discloses a device in which a floodlight system has a plurality of light sources and a plurality of drive circuits for driving the plurality of light sources, and a plurality of light sources are turned on to measure a distance to an object. ing.

However, in the apparatus disclosed in Patent Document 1, there is room for improvement in improving the measurement accuracy of the distance to the object.

The present invention includes a light projecting system including a plurality of light sources and a plurality of drive circuits for driving the plurality of light sources, a light receiving system that receives light projected from the light source system and reflected by an object, and the plurality of light sources. The light receiving system is provided with a plurality of light receiving elements, each light receiving element has two charge storage portions, and each light receiving element is provided from the correction system. Based on the timing signal of the above, the charge generated by the received light is accumulated, and the correction system also corrects the deviation between the light emission timing and the timing signal and turns on one light source in the plurality of light sources. The first distance is calculated based on the light receiving result at that time, and the second distance is calculated based on the light receiving result when the other light source different from the one light source and the one light source in the plurality of light sources are turned on. The distance is calculated, the deviation of the light emission timing of the plurality of light sources is corrected based on the first distance and the second distance, and the light emission timing of the one light source is corrected based on the first distance. It is a distance measuring device that corrects a deviation from the timing signal .

According to the present invention, the accuracy of measuring the distance to an object can be improved.

It is a figure which shows schematic structure of the distance measuring apparatus of a comparative example. It is a timing diagram which shows the modulation signal, the irradiation light pulse Le, the reflected light pulse Lr, the timing signal A, and the timing signal B of the distance measuring apparatus of the comparative example. FIG. 3A is a timing diagram showing the case where the delays of the irradiation light pulses Le1 and Le2 with respect to the modulated signal are the same, and FIG. 3B is a timing diagram showing the case where the delays of the irradiation light pulses Le1 and Le2 with respect to the modulated signal are different. It is a timing diagram which shows. It is a figure for demonstrating the error of the charge accumulation amount in the charge accumulation part A, B of the light receiving element of an area sensor. It is a figure which shows schematic structure of the distance measuring apparatus of one Embodiment. It is a flowchart for demonstrating the light emission timing deviation correction processing. It is a figure for demonstrating the structure of the timing control means of the modification 1. FIG. It is a figure for demonstrating the generation method of the modulation signal 1 and 2 of the modification 1. FIG. It is a figure for demonstrating the structure of the timing control means of the modification 2. FIG. It is a figure for demonstrating the generation method of the modulation signal 1 and 2 of the modification 2. FIG. It is a figure which shows schematic structure of the distance measuring apparatus of the modification 3. It is a timing diagram which shows the modulation signal X, PD signal 1 and 2. It is a flowchart for demonstrating the light emission timing deviation correction processing of the modification 3. It is a figure which shows roughly the structure of the distance measuring apparatus of the modification 4. It is a flowchart for demonstrating the light emission timing deviation correction processing of the modification 4. It is a figure for demonstrating the structure of the timing control means of the modification 5. It is a figure for demonstrating the generation method of the modulation signal 1, 2 of the modification 5. It is a figure for demonstrating the structure of the timing control means of the modification 6. It is a figure for demonstrating the method of generating the modulation signal 1, 2 of the modification 6.

First, prior to the description of the distance measuring device 1 of one embodiment, the distance measuring device 1'of the comparative example will be described.

<< Comparative example >>
As an example, the distance measuring device 1'is attached near the license plate at the front end of the vehicle as a moving body.

FIG. 1 schematically shows the configuration of the distance measuring device 1'of the comparative example. The distance measuring device 1'includes a light emitting system 10, a light receiving system 20, a timing control unit 31, and a distance calculation unit 32.

The projection system 10 includes two light sources 1 and 2, two drive circuits 1 and 2 for driving the light sources 1 and 2, and a projection optical system (not shown) for projecting light from each light source toward the front of the vehicle. ) And. As each light source, for example, a semiconductor laser or a light emitting diode is used.

When the modulation signal (pulse signal) from the timing control unit 31 is input, the drive circuits 1 and 2 apply a modulation current corresponding to the modulation signal to the light sources 1 and 2, respectively. As a result, modulated light corresponding to the modulation current is emitted from the light sources 1 and 2 and is projected as an irradiation light pulse Le via the projection optical system. At this time, the object to be measured (measurement target) is within the range of the light projection range (projection range of the projection optical system) of the light projection system 10 (within the range detectable by the sum of the light outputs of the light sources 1 and 2). If there is, the projected light (irradiation light pulse Le) is applied to the object.

The light receiving system 20 guides the area sensor 21 including a plurality of two-dimensionally arranged light receiving elements (for example, photodiodes, phototransistors, etc.) individually corresponding to the plurality of pixels and the reflected light from the object to the area sensor 21. It has a light receiving optical system (not shown) including a light collecting element.

Each light receiving element of the area sensor 21 has two charge storage portions A and B. Each light receiving element receives the modulated light (reflected light pulse Lr) that is applied to the object and reflected by the object, and according to the timing signals A and B from the timing control unit 31, the electric charge generated by the received light is received. Accumulate.

Specifically, each light receiving element stores the charge in the charge storage unit A when the timing signal A is “H” and in the charge storage unit B when the timing signal B is “H”.

The timing control unit 31 repeatedly outputs the modulation signal, the timing signal A, and the timing signal B, whereby charges are accumulated more and more. Then, after repeating the accumulation of electric charges a predetermined number of times, the output of the modulation signal, the timing signal A, and the timing signal B is stopped, and the received light data output instruction signal is output to the area sensor 21.

The area sensor 21 sequentially outputs the amount of charge accumulated in the charge storage units A and B of each light receiving element as light receiving data A and light receiving data B.

The distance calculation unit 32 receives the distance calculation instruction signal from the timing control unit 31, calculates the distance data in each pixel using the light receiving data A and B sent from the area sensor 21, and generates a distance image. The generated distance image is sent to the ECU (electronic control unit) of the vehicle and used for braking control such as auto braking and steering control such as auto steering. The "distance image" means an image in which the data of each of the plurality of pixels represents the distance to the measurement object.

The timing control unit 31 repeatedly generates modulation signals, timing signals A and B a predetermined number of times, outputs them to drive circuits 1, 2 and an area sensor 21, and then outputs a light receiving data output instruction signal to the area sensor 21 to obtain a distance. The calculation instruction signal is output to the distance calculation unit 32.

FIG. 2 shows a time chart of the modulation signal, the timing signals A and B, the irradiation light pulse Le, and the reflected light pulse Lr.

The modulated signal shown in FIG. 2A is a pulse signal having a pulse width Tw (pulse time width).

The irradiation light pulse Le shown in FIG. 2B is light projected from the projection system 10, and is output from the input timing of the modulation signal with a delay time td by each drive circuit.

The reflected light pulse Lr shown in FIG. 2C is light in which the irradiation light pulse Le is reflected by an object and received by the area sensor 21. The waveform of this light is substantially the same as the waveform of the irradiation light pulse Le, and is incident on the area sensor 21 with a time τ delay from the rising timing of the irradiation light pulse Le (light emission timing of the light source).

This time τ is the time from when the irradiation light pulse Le is projected from the light projecting system 10 to when it is reflected by the object and incident on the area sensor 21, and varies depending on the distance to the object. That is, if the time τ is known, the distance D to the object can be obtained by the following equation (1) using the speed of light C.
D = τ × C / 2 ... (1)

2 (d) and 2 (e) show timing signals A and B, which are signals indicating the charge accumulation timing, output from the timing control unit 31 to the area sensor 21, respectively.

The timing signal A is set to “H” at the same timing as the irradiation light pulse Le, and is set to “L” after the pulse width Tw. Then, the timing signal B is set to "H" at the same time when the timing signal A becomes "L", and is set to "L" after the pulse width Tw. Since the charge is accumulated in the charge storage unit A during the period when the timing signal A is “H”, the charge corresponding to the portion A in FIG. 2D is accumulated. Since the charge is accumulated in the charge storage unit B during the period when the timing signal B is “H”, the charge corresponding to the portion B in FIG. 2E is accumulated. Here, if the time τ is in the range of 0 ≦ τ ≦ Tw, the following equation (2) holds.
τ / Tw = B / (A + B) ... (2)

Therefore, the distance D can be obtained by the following equation using the above equations (1) and (2).
D = B / (A + B) x Tw x C / 2

FIG. 3 shows a waveform of an irradiation light pulse Le in which at least a part of the irradiation light pulses Le1 and Le2 having the same pulse width (Tw) with the light sources 1 and 2 as light sources overlaps.

FIG. 3A shows a case where the delays for the modulated signals are the same in the drive circuits 1 and 2 in the light projecting system 10, and the rise of the irradiation light pulse Le1 by the light source 1 only and the irradiation light pulse Le2 by the light source 2 only. The falling edge timing is the same, and the irradiation light pulse Le in which substantially all of the irradiation light pulses Le1 and Le2 overlap is the magnitude (pulse amplitude) obtained by adding the intensities of the irradiation light pulses Le1 and Le2. The width is Tw.

FIG. 3B shows a case where the delay with respect to the modulated signal differs between the drive circuits due to the performance variation of the circuit elements and wirings constituting the drive circuits 1 and 2 in the floodlight system 10. Here, the delay of the drive circuit 2 is smaller than the delay of the drive circuit 1, and it is shown that the irradiation light pulse Le2 rises te earlier than the irradiation light pulse Le1 and falls te earlier. As shown in FIG. 3B, the waveform of the irradiation light pulse Le formed by overlapping the irradiation light pulses Le1 and Le2 whose rising and falling timings are deviated becomes a waveform having a pulse width Tw + te. The light reflected by the object to be measured and incident on the area sensor 21 also has the same pulse width Tw + te waveform.

FIG. 4 shows the state of charge accumulation in the charge storage units A and B when the waveform of the pulse width Tw + te is incident on the area sensor 21.

As shown in FIG. 4, the charge accumulation amount of the charge storage unit A is A + α, which is increased by α as compared with the charge accumulation amount of FIG. On the other hand, the charge accumulation amount of the charge storage unit B becomes B−α, which is smaller by α than the charge accumulation amount of FIG.

As described above, in the comparative example, the charge accumulation amount of the charge storage unit A and the charge storage unit B changes, so that an error occurs in the distance measurement.

Therefore, the inventors have developed the distance measuring device 1 of the present embodiment in order to reduce such an error.

<< Embodiment >>
The distance measuring device 1 of the present embodiment will be described below. FIG. 5 schematically shows the configuration of the distance measuring device 1 of the present embodiment.

As an example, the distance measuring device 1 is attached near the license plate at the front end of the vehicle as a moving body. In addition to vehicles, examples of the moving body on which the distance measuring device 1 is mounted include aircraft, ships, robots, and the like.

The distance measuring device 1 includes a light emitting system 10, a light receiving system 20, and a control device 40 including a timing control means 41 (adjustment means) and a distance calculation unit 42 (calculation means).

The projection system 10 includes two light sources 1 and 2, two drive circuits 1 and 2 for driving the light sources 1 and 2, and a projection optical system (not shown) for projecting light from each light source toward the front of the vehicle. ) And. As each light source, for example, a light emitting element such as a semiconductor laser (end face emitting laser (LD) or surface emitting laser (VCSEL)) or a light emitting diode is suitable, but other light emitting elements may be used.

When the drive circuit ON signal 1 from the timing control means 41 is at the "H" level, the drive circuit 1 applies a modulation current 1 corresponding to the modulation signal 1 to the light source 1, and the drive circuit ON signal 1 is at the "L" level. When, the drive current is always turned off.

When the drive circuit ON signal 2 from the timing control means 41 is at the “H” level, the drive circuit 2 applies a modulation current 2 corresponding to the modulation signal 2 to the light source 2, and the drive circuit ON signal 2 is at the “L” level. When, the drive current is always turned off.

The light source 1 emits modulated light corresponding to the modulated current 1, and the modulated light is projected as an irradiation light pulse Le1 by the projection optical system.

The light source 2 emits modulated light corresponding to the modulated current 2, and the modulated light is projected as an irradiation light pulse Le2 by the projection optical system.

That is, the irradiation light pulse Le projected from the light projection system 10 is light in which the irradiation light pulse Le1 and the irradiation light pulse Le2 overlap.

At this time, the object to be measured (measurement target) is within the range of the light projection range (projection range of the projection optical system) of the light projection system 10 (within the range detectable by the sum of the light outputs of the light sources 1 and 2). If there is, the projected light (irradiation light pulse Le) is applied to the object.

The projection optical system may be, for example, a scanning type including an optical deflector or a non-scanning type including, for example, a diffuser, but the horizontal and vertical projection ranges required for sensing (object detection) in front of the vehicle. Those that can secure the above are preferable.

Since the scanning type projection optical system projects collimated light, the irradiation power density on the object to be measured is relatively large, and the optical signal-to-noise ratio can be increased. On the other hand, since the non-scanning projection optical system projects a wide range of light, it is possible to measure the distances of multiple points of the measurement object at the same time with one projection, and it is possible to obtain a high-resolution spatial distribution at high speed. Can be done.

The light receiving system 20 guides the area sensor 21 including a plurality of two-dimensionally arranged light receiving elements (for example, photodiodes, phototransistors, etc.) individually corresponding to the plurality of pixels and the reflected light from the object to the area sensor 21. It has a light receiving optical system (not shown) including a light collecting element.

Each light receiving element of the area sensor 21 has two charge storage portions A and B. Each light receiving element receives the modulated light (reflected light pulse Lr) that is applied to the object and reflected by the object, and according to the timing signals A and B from the timing control means 41, the electric charge generated by the received light is received. Accumulate.

Specifically, each light receiving element stores charges in the charge storage unit A when the timing signal A is “H”, and charges the charge storage unit B when the timing signal B is “H”. Do.

The timing control means 41 repeatedly outputs the modulation signals 1 and 2, and the timing signals A and B, whereby the electric charge is accumulated steadily. Then, after repeating the accumulation of electric charges a predetermined number of times, the output of the modulation signals 1 and 2, the timing signals A and B is stopped, and the received light data output instruction signal is output to the area sensor 21.

The area sensor 21 sequentially outputs the amount of charge accumulated in the charge storage units A and B of each light receiving element as light receiving data A and B.

The distance calculation unit 42 receives the distance calculation instruction signal from the timing control means 41, calculates the distance data in each pixel using the light receiving data A and B sent from the area sensor 21, and generates a distance image. The method of calculating the distance data from the received light data A and B is as described above.

The timing control means 41 includes delay elements 1 and 2, an adjustment control unit 41a, and a signal generation unit 41b.

The delay element 1 delays the modulation signal X generated by the signal generation unit according to the level of the delay adjustment signal 1 from the adjustment control unit 41a, and outputs the modulation signal X as the modulation signal 1.

The delay element 2 delays the modulation signal X generated by the signal generation unit according to the level of the delay adjustment signal 2 from the adjustment control unit 41a, and outputs the modulation signal X as the modulation signal 2.

As described above, the lighting timings of the light sources 1 and 2 (the rising timings of the irradiation light pulses Le1 and Le2) can be changed by the delay adjustment signals 1 and 2.

The signal generation unit 41b generates a pulsed or sine wave modulated signal X, and repeatedly outputs it to the delay elements 1 and 2 a predetermined number of times. Further, the signal generation unit 41b generates timing signals A and B having the same waveform as the modulation signal X based on the delay information from the adjustment control unit 41a described later, and repeatedly outputs the timing signals A and B to the area sensor 21 a predetermined number of times.

Here, it is necessary to match the output timing of the timing signal A with the rising timing of the irradiation light pulse Le (light emission timing of the light source 1) as shown in FIG. The delay information is the delay time from the output timing of the modulation signal X to the rise of the irradiation light pulse Le, and based on this, the output timing of the timing signal A can be matched with the light emission timing of the light source 1. In this way, the timing signal A is set to “H” at the same timing as the irradiation light pulse Le, and is set to “L” after the pulse width Tw. Then, the timing signal B is set to "H" at the same time as the timing signal A becomes "L", and is set to "L" after the pulse width Tw.

Further, the signal generation unit 41b repeatedly generates and outputs the modulation signal X and the timing signals A and B a predetermined number of times, then outputs the received light data output instruction signal to the area sensor 21 and outputs the distance calculation instruction signal to the distance calculation unit 42. Output.

The adjustment control unit 41a generates delay adjustment signals 1 and 2 for controlling the delay amount of the delay elements 1 and 2 based on the distance data from the distance calculation unit 42. Further, the adjustment control unit 41a generates a drive circuit ON signal 1 and a drive circuit ON signal 2 for controlling the on / off of the drive circuits 1 and 2 of the projection system 10. Then, the adjustment control unit 41a controls these signals to correct the deviation of the light emission timings of the light sources 1 and 2.

Hereinafter, a method of correcting the deviation of the light emission timing between the light source 1 and the light source 2 (light emission timing deviation correction processing) in the distance measuring device 1 of the present embodiment will be described with reference to FIG. The flowchart of FIG. 6 is based on a processing algorithm executed by the control device 40. Here, the light emission timing deviation correction processing is performed periodically in consideration of performance variations over time and during manufacturing of the circuit elements and wirings constituting the drive circuits 1 and 2, but irregularly (for example, when the device is started). You may go.

Here, in executing the light emission timing deviation correction process, a reference reflector having a predetermined reflectance is set as a measurement target at a position of a reference distance Dref which is a reference reference in the light projection range of the projection system 10. The "reference distance Dref" is a distance at which only the light source 1 is turned on and the reference reflector can be detected. The reference distance Dref is generally determined by the light output (emission light amount) of the light source 1 and the reflectance of the reference reflector.

Since the light is attenuated in inverse proportion to the square of the distance, the light becomes weaker as the distance increases. It is possible to secure the amount of irradiation light at a distant place by using two light sources, light source 1 and light source 2, so that the distance can be measured even at a long distance, but if the object to be measured is near, the amount of irradiation light can be secured only by the light source 1. Distance measurement is possible

In the first step S1, only the light source 1 is turned on to measure the distance.

Specifically, the adjustment control unit 41a sets the drive circuit ON signal 1 to the “H” level and the drive circuit ON signal 2 to the “L” level.

Next, the adjustment control unit 41a sets the delay adjustment signal 1 to a predetermined value, considers the value of the delay adjustment signal 1 and the representative value of the delay amount of the drive circuit 1, generates delay information, and generates signal generation unit 41b. Output to.

The signal generation unit 41b generates the modulation signal X, and also generates the timing signals A and B based on the modulation signal X and the delay information. At this time, since only the drive circuit ON signal 1 is at the “H” level, only the light source 1 emits light according to the modulation signal 1 output from the modulation signal X with a delay according to the delay adjustment signal 1.

As a result, the irradiation light pulse Le1 from only the light source 1 is applied to the reference reflector, the reflected light pulse Lr from the reference reflector is received by the area sensor 21, and the charge storage units A and B are subjected to the timing signals A and B. Charges are accumulated in each.

The charge storage data of the charge storage units A and B are output to the distance calculation unit 32 as the light reception data A and B, the distance calculation is performed, and the measurement distance 1 is calculated.

Here, the delay amount of the drive circuit 1 may differ from the representative value due to variations in the performance of the circuit elements and wiring. In this case, the light emission timing of the light source 1 and the output timing of the timing signal A based on the representative value are deviated, and the measurement distance 1 does not match the reference distance Dref. Conversely, when the measurement distance 1 and the reference distance Drf do not match, there is a discrepancy between the light emission timing of the light source 1 (rising timing of the irradiation light pulse Le1) and the output timing of the timing signal A. become.

Therefore, in the next step S2, it is determined whether or not the measurement distance and the reference distance Dref match. If the judgment here is denied, the process proceeds to step S3, and if affirmed, the process proceeds to step S4.

In step S3, the light emission timing of the light source 1 is adjusted. Specifically, the delay adjustment signal 1 is generated based on the difference between the measurement distance and the reference distance Dref, and is output to the delay element 1. Then, the delay element 1 outputs the modulation signal 1 in which the modulation signal X is delayed according to the delay adjustment signal 1 to the drive circuit 1. A modulation current 1 corresponding to the modulation signal 1 is applied from the drive circuit 1 to the light source 1, and an irradiation light pulse Le1 which is a modulation light corresponding to the modulation current 1 is emitted from the light source 1.

When step S3 is executed, the process returns to step S1. Then, in step S1, only the light source 1 is turned on and the distance measurement is performed again, and in step S2, it is confirmed whether the measurement distance 1 matches the reference distance Dref.

In step S4, the light sources 1 and 2 are turned on to measure the distance.

Specifically, the adjustment control unit 41a sets the drive circuit ON signal 2 to the “H” level in addition to the drive signal ON signal 1. Here, the value of the delay adjustment signal 2 is set to the value of the delay adjustment signal 1 used (in step S1) when only the light source 1 is turned on and the distance is measured.

After that, the modulation signals X and the timing signals A and B are output from the signal generation unit 41b, the distance calculation is performed in the same manner as in step S1, and the measurement distance 2 is calculated.

Here, if the delay amount of the drive circuit 2 is different from the delay amount of the drive circuit 1, the light emission timings of the light sources 1 and 2 are shifted, and the irradiation light pulses Le1 from the light sources 1 and 2 are shifted as described with reference to FIG. , The waveform of the irradiation light pulse Le on which Le2 overlaps is different from the desired waveform (rectangular in FIG. 3), and an error occurs in the measurement distance.

Therefore, in the next step S5, it is determined whether or not the measurement distance 2 and the reference distance Dref match. If the judgment here is denied, the process proceeds to step S6, and if it is affirmed, the flow ends. When the determination in step S5 is affirmed, it is the case that the light emission timings of the light sources 1 and 2 match.

In step S6, the light emission timing of the light source 2 is adjusted. Specifically, the adjustment control unit 41a generates a delay adjustment signal 2 based on the difference between the measurement distance 2 and the reference distance Dref, and outputs the delay adjustment signal 2 to the delay element 2. Then, the delay element 2 outputs the modulation signal 2 in which the modulation signal X is delayed according to the delay adjustment signal 2 to the drive circuit 2. A modulation current 2 corresponding to the modulation signal 2 is applied from the drive circuit 2 to the light source 2, and an irradiation light pulse Le2 which is a modulation light corresponding to the modulation current 2 is emitted from the light source 2.

When step S6 is executed, the process returns to step S4. Then, in step S4, the light sources 1 and 2 are turned on and the distance measurement is performed again, and in step S5, it is confirmed whether the measurement distance 2 matches the reference distance Dref.

By adjusting the light emission timings of the light sources 1 and 2 as described above, the deviation of the light emission timings of the light sources 1 and 2 can be corrected, and after the correction, the light sources 1 and 2 are turned on to measure the distance. As a result, the error in the measurement distance can be reduced, and the measurement accuracy of the distance can be improved.

The distance measuring device 1 of the present embodiment described above includes a plurality of light sources (for example, two light sources 1 and 2) and a plurality of drive circuits (for example, two drive circuits 1 and 2) for driving the plurality of light sources. It includes a light projecting system 10, a light receiving system 20 that receives light projected from the light projecting system 10 and reflected by an object, and a correction system that corrects a deviation in light emission timing of a plurality of light sources.

In this case, the detection error can be reduced by receiving the light projected from the light projecting system 10 and reflected by the object by the light receiving system 20 in a state where the deviation of the light emitting timings of the plurality of light sources is corrected.

As a result, the accuracy of measuring the distance to the object can be improved.

Further, the correction system includes a control device 40 that corrects the deviation of the light emission timing of the plurality of light sources based on the light receiving result in the light receiving system 20.

In this case, the distance to the object can be measured and the deviation of the light emission timings of the plurality of light sources can be corrected by using the light receiving result of the light receiving system 20.

Further, by turning on a plurality of light sources together and superimposing the projected light, the amount of the projected light can be increased, and the maximum detection distance at which an object can be detected can be lengthened. ..

Further, a plurality of modulation signals (for example, two modulation signals 1 and 2) for causing the light sources 1 and 2 to emit light are input to the drive circuits 1 and 2, respectively, and the control device 40 receives light from the light receiving system 20. Based on the result, the calculation means (distance calculation unit 42) that calculates the distance to the object and the input timing of the modulation signals 1 and 2 to the drive circuits 1 and 2 are adjusted based on the calculation result by the calculation means. The adjusting means (timing control means 41) is included.

In this case, the measurement accuracy of the distance to the object can be improved by a simple configuration.

Further, the adjusting means is a first distance (measurement distance 1) which is a calculation result by the distance calculation unit 42 when the light source 1 is turned on, and a distance calculation unit 42 when the light sources 1 and 2 are turned on. It is preferable to adjust the input timing of the modulation signals 1 and 2 to the drive circuits 1 and 2 according to the difference in the second distance (measurement distance 2) which is the calculation result of. Specifically, it is preferable to adjust the input timing of the modulated signals 1 and 2 to the drive circuits 1 and 2 so that the difference between the first and second distances is small (including 0).

In this case, a simple method of generating a common (single) modulation signal X that is the source of the modulation signals 1 and 2 and adjusting the output timing of the modulation signal X to the drive circuits 1 and 2 is used. It is possible to correct the deviation of the light emission timings of the light sources 1 and 2.

Further, when the distance measuring device 1 is arranged in the light projecting range of the light projecting system 10 and further includes a reference reflector whose distance can be measured by the light output of the light source 1, the light emission timings of the light sources 1 and 2 are corrected. (Light emission timing correction processing) can be performed at any time.

Further, the adjustment means is adjusted with the adjustment control unit 41a that generates adjustment signals (delay adjustment signals 1 and 2) for adjusting the input timings of the modulation signals 1 and 2 based on the first and second distances. It is preferable to have adjusting elements (delay elements 1 and 2) for adjusting the input timings of the modulated signals 1 and 2 according to the signal.

Further, when the light receiving system 20 includes an area sensor 21 having a light receiving unit corresponding to a plurality of pixels, it is possible to generate a distance image representing distance information for each part of an object (for each pixel). In this case, the size and shape of the object can be detected, and more detailed object information can be obtained.

When the area sensor 21 has two charge storage units A and B for each pixel, the two charge storage units A charge the reflected light in a predetermined time zone based on the light emission timing of the light sources 1 and 2. , B can be accumulated.

Further, according to the moving body device including the distance measuring device 1 of the present embodiment and the moving body on which the distance measuring device 1 is mounted, control of the moving body (for example, braking) is performed based on a highly accurate measurement distance. Control, steering control, etc.) can be performed with high accuracy.

Further, the distance measuring method of the present embodiment is a distance measuring method for measuring the distance to an object, and is a reference reflector by turning on one of a plurality of light sources (light sources 1 and 2) (light source 1). A first irradiation step of irradiating light to the reference reflector, and a first measurement step of receiving the light irradiated in the first irradiation step and reflected by the reference reflector and measuring the distance to the reference reflector. In the second irradiation step in which one light source (light source 1) and the other light source (light source 2) are turned on to irradiate the reference reflector with light, and in the second irradiation step, the reference reflector is irradiated. Based on the second measurement step of receiving the reflected light and measuring the distance to the reference reflector and the measurement results (measurement distances 1 and 2) in the first and second measurement steps, one and A step of correcting a deviation in the lighting timing (light emission timing) of another light source, and a step of lighting one or another light source to project light, receiving the light reflected by the object, and calculating the distance to the object. And, including.

In this case, the detection error can be reduced by receiving the light projected by the light source and reflected by the object by the light receiving system 20 in a state where the deviation of the lighting timings of the plurality of light sources is corrected.

As a result, the accuracy of measuring the distance to the object can be improved.

When there are a plurality of other light sources, it is preferable to perform a cycle including a second irradiation step, a second measurement step, and a correction step for each other light source. In this case, it is possible to correct the difference in lighting timing between one light source and all other light sources.

<< Modification 1 >>
FIG. 7 shows a block diagram of the timing control means 51 included in the control device of the distance measuring device of the first modification.

As shown in FIG. 7, the timing control means 51 of the first modification 1 generates and modulates the modulation signals 1 and 2 input to the drive circuits 1 and 2, respectively, based on the clock signal (also referred to as “clock”). The delay control of the signal 1 and the modulated signal 2 is controlled in clock units based on the adjustment data 1 and the adjustment data 2.

More specifically, the timing control means 51 is based on a clock generation unit 51a that generates a reference clock, drive circuits ON signals 1 and 2 for performing on / off control of drive circuits 1 and 2, and a distance image (distance data). The adjustment control unit 51b that generates the adjustment data 1 and 2 and the delay information, and the clock signal, the adjustment data 1 and 2, the start signal, and the modulation signals 1 and 2 based on the delay information are generated, and further, the clock signal, the start signal, It is configured to include timing signals A and B, a light receiving data output instruction signal, and a signal generation unit 51c that generates a distance calculation instruction signal based on delay information.

FIG. 8 shows in a time chart how the modulation signals 1 and 2 are generated based on the clock signal in the modification 1.

Here, the case where the adjustment data 1 is “8” and the adjustment data 2 is “10” is shown, and the case where the pulse width of each modulation signal is “8” is shown.

When the start signal is input to the signal generation unit 51c, the built-in start counter starts counting the clock from the clock generation unit 51a. The signal generation unit 51c changes the modulated signal 1 to the “H” level when the value of the start counter becomes “8”, which is the same as the value of the adjustment data 1. After that, the signal generation unit 51c starts counting with the pulse width counter 1, and changes the modulated signal 1 to the “L” level when the pulse width reaches “8”. The pulse width counter 1 is reset to "1" and starts counting again, and when it reaches "8", the modulation signal 1 is changed to the "H" level. This is repeated to generate the modulated signal 1.

On the other hand, the signal generation unit 51c changes the modulation signal 2 to the “H” level when the count value of the start counter becomes “10”, which is the same as the value of the adjustment data 2. After that, the signal generation unit 51c starts counting with the pulse width counter 2, and changes the modulated signal 2 to the “L” level when the pulse width reaches “8”. The pulse width counter 2 is reset to "1" and starts counting again, and when it reaches "8", the modulated signal 2 is changed to the "H" level. This is repeated to generate the modulated signal 2.

Since the modulation signals 1 and 2 are output according to the values of the adjustment data 1 and 2 in this way, the output timing of the modulation signals 1 and 2 can be adjusted by adjusting the adjustment data 1 and 2, and the light source 1 It is possible to match the light emission timings of 2.

As described above, in the modification 1, since the modulation signals 1 and 2 are generated by the logic circuit using the clock signal, the modulation signals 1 and 2 can be generated with a small-scale circuit configuration.

Even in the distance measuring device of the first modification, the timing control means 51 (adjusting means) is a distance calculation unit when one of a plurality of light sources (for example, two light sources 1 and 2) is turned on (light source 1). According to the difference between the first distance, which is the calculation result of, and the second distance, which is the calculation result by the distance calculation unit when the other light source (light source 2) of one light source and the plurality of light sources is turned on. Then, the input timing of the modulation signals 1 and 2 to the drive circuits 1 and 2 is adjusted.

The control device including the timing control means 51 and the distance calculation unit further includes a clock generation unit 51a for generating a clock signal and a counter for counting the clock signal, and the timing control means 51 further includes a counter count value. Then, the modulation signals 1 and 2 are generated based on the first and second distances (the input timing of the modulation signals 1 and 2 to the drive circuits 1 and 2 is adjusted).

<< Modification 2 >>
FIG. 9 shows a block diagram of the timing control means 61 included in the control device of the distance measuring device of the second modification.

In the second modification, as shown in FIG. 9, the adjustment data 1 and 2 generated by the adjustment control unit 61b are input to the clock generation unit 61a, and the clock signals 1 and 2 are generated by the clock generation unit 61a. It is configured to be output to the generation unit 61c. The phases of the clock signals 1 and 2 are changed according to the adjustment data 1 and 2, and the clock signals 1 and 2 are output to the signal generation unit 61c.

FIG. 10 shows a time chart showing how the modulation signals 1 and 2 are generated based on the clock signals 1 and 2 and the adjustment data 1 and the adjustment data 2 in the modification 2.

Here, the case where the adjustment data 1 is “8” and the adjustment data 2 is “10.5” is shown, and the case where the pulse width of each modulation signal is “8” is shown.

In the signal generation unit 61c, when the start signal is input, the built-in start counter 1 starts counting with the clock signal 1, and when the value of the start counter 1 becomes “8”, which is the same as the value of the adjustment data 1, the modulation signal is signaled. Change 1 to "H" level. After that, the signal generation unit 61c starts counting with the pulse width counter 1 and changes the modulated signal 1 to the “L” level when the pulse width reaches “8”. The pulse width counter 1 is reset to "1" and starts counting again, and when it reaches "8", the modulation signal 1 is changed to the "H" level. This is repeated to generate the modulated signal 1.

On the other hand, the signal generation unit 61c generates the modulation signal 2 based on the clock signal 2, but when the adjustment data 2 of "10.5" is input to the clock generation unit 61a, the fractional part "0.5", That is, the clock signal 2 is generated and output with the phase delayed by 1/2 clock. That is, as shown in FIG. 10, the clock signal 2 is lagging in phase by 1/2 clock with respect to the clock signal 1. The modulation signal 2 is generated using this clock signal 2.

More specifically, in the signal generation unit 61c, when the start signal is input, the start counter 2 starts counting with the clock signal 2, and when the count value of the start counter 2 becomes the integer value “10” of the adjustment data 2. The modulated signal 2 is changed to the "H" level. After that, the signal generation unit 61c starts counting with the pulse width counter 2, and changes the modulated signal 2 to the “L” level when the pulse width reaches “8”. The pulse width counter 2 is reset to "1" and starts counting again, and when it reaches "8", the modulated signal 2 is changed to the "H" level. This is repeated to generate the modulated signal 2.

As described above, in the modification 2, the clock signal 1 and the clock signal 2 whose phases are adjusted are generated from the clock generation unit 61a, the clock signal 1 generates the modulated signal 1, and the clock signal 2 generates the modulated signal 2. By generating it, it is possible to control (adjust) with an accuracy of a time shorter than the clock width of the clock signal 1, the light emission timings of the light sources 1 and 2 can be adjusted more accurately, and the error of the measurement distance is further increased. It can be made smaller.

Even in the distance measuring device of the second modification, the timing control means 61 (adjusting means) is a distance calculation unit when one of a plurality of light sources (for example, two light sources 1 and 2) is turned on (light source 1). According to the difference between the first distance, which is the calculation result of, and the second distance, which is the calculation result by the distance calculation unit when the other light source (light source 2) of one light source and the plurality of light sources is turned on. Then, the input timing of the modulation signals 1 and 2 to the drive circuits 1 and 2 is adjusted.

The control device including the timing control means 61 and the distance calculation unit includes a clock generation unit 61a that generates a plurality of clock signals having different phases based on the first and second distances, and a plurality of clock signals that count the plurality of clock signals. A counter is further included, and the input timing of the modulation signals 1 and 2 to the drive circuits 1 and 2 is adjusted based on the count values of the plurality of counters and the first and second distances.

In the second modification, the clock signal 2 is delayed by 1/2 clock in phase with the clock signal 1, but instead, for example, N is an integer of 3 or more and the phase is delayed by 1 / N clock. You may.

<< Modification 3 >>
FIG. 11 schematically shows the configuration of the distance measuring device 1A of the modified example 3.

The distance measuring device 1A includes a light emitting system 10, a light receiving system 20, a detecting means 30, and a control device 40A including a timing control means 41A (adjusting means) and a distance calculating unit 42 (calculating means). ..

The projection system 10 includes two light sources 1 and 2, two drive circuits 1 and 2 for driving the light sources 1 and 2, and a projection optical system (not shown) for projecting light from each light source toward the front of the vehicle. ) And. As each light source, for example, a light emitting element such as a semiconductor laser or a light emitting diode is suitable, but other light emitting elements may be used.

When the drive circuit ON signal 1 from the timing control means 41A is at the “H” level, the drive circuit 1 applies a modulation current 1 corresponding to the modulation signal 1 to the light source 1, and the drive circuit ON signal 1 is at the “L” level. When, the drive current is always turned off.

When the drive circuit ON signal 2 from the timing control means 41A is at the “H” level, the drive circuit 2 applies a modulation current 2 corresponding to the modulation signal 2 to the light source 2, and the drive circuit ON signal 2 is at the “L” level. When, the drive current is always turned off.

The light source 1 emits modulated light corresponding to the modulated current 1, and the modulated light is projected as an irradiation light pulse Le1 by the projection optical system.

The light source 2 emits modulated light corresponding to the modulated current 2, and the modulated light is projected as an irradiation light pulse Le2 by the projection optical system.

That is, the irradiation light pulse Le projected from the light projection system 10 is light in which the irradiation light pulse Le1 and the irradiation light pulse Le2 overlap.

At this time, the object to be measured (measurement target) is within the range of the light projection range (projection range of the projection optical system) of the light projection system 10 (within the range detectable by the sum of the light outputs of the light sources 1 and 2). If there is, the projected light (irradiation light pulse Le) is applied to the object.

The projection optical system may be, for example, a scanning type including an optical deflector or a non-scanning type including, for example, a diffuser, but the horizontal and vertical projection ranges required for sensing (object detection) in front of the vehicle. Those that can secure the above are preferable.

The light receiving system 20 guides the area sensor 21 including a plurality of two-dimensionally arranged light receiving elements (for example, photodiodes, phototransistors, etc.) individually corresponding to the plurality of pixels and the reflected light from the object to the area sensor 21. It has a light receiving optical system (not shown) including a light collecting element.

Each light receiving element of the area sensor 21 has two charge storage portions A and B. Each light receiving element receives the modulated light (reflected light pulse Lr) that is applied to the object and reflected by the object, and according to the timing signals A and B from the timing control means 41, the electric charge generated by the received light is received. Accumulate.

Specifically, each light receiving element stores charges in the charge storage unit A when the timing signal A is “H”, and charges the charge storage unit B when the timing signal B is “H”. Do.

The timing control means 41A repeatedly outputs the modulation signals 1 and 2, and the timing signals A and B, whereby the electric charge is accumulated steadily. Then, after repeating the accumulation of electric charges a predetermined number of times, the output of the modulation signals 1 and 2, the timing signals A and B is stopped, and the received light data output instruction signal is output to the area sensor 21.

The area sensor 21 sequentially outputs the amount of charge accumulated in the charge storage units A and B of each light receiving element as light receiving data A and B.

The distance calculation unit 42 receives the distance calculation instruction signal from the timing control means 41A, calculates the distance data in each pixel using the light receiving data A and B sent from the area sensor 21, and generates a distance image. The method of calculating the distance data from the received light data A and B is as described above.

The timing control means 41A includes delay elements 1 and 2, adjustment control units 41Aa, signal generation units 41Ab, and time measurement units 1 and 2.

The delay element 1 delays the modulation signal X generated by the signal generation unit according to the level of the delay adjustment signal 1 from the adjustment control unit 41Aa, and outputs the modulation signal X as the modulation signal 1.

The delay element 2 delays the modulation signal X generated by the signal generation unit according to the level of the delay adjustment signal 2 from the adjustment control unit 41Aa, and outputs the modulation signal X as the modulation signal 2.

As described above, the lighting timings of the light sources 1 and 2 (the rising timings of the irradiation light pulses Le1 and Le2) can be changed by the delay adjustment signals 1 and 2.

The signal generation unit 41Ab generates a pulsed or sine wave modulated signal X, and repeatedly outputs it to the delay elements 1 and 2 a predetermined number of times. Further, the signal generation unit 41Ab generates timing signals A and B having the same waveform as the modulation signal X based on the delay information from the adjustment control unit 41Aa described later, and repeatedly outputs the timing signals A and B to the area sensor 21 a predetermined number of times.

Here, it is necessary to match the output timing of the timing signal A with the rising timing of the irradiation light pulse Le (light emission timing of the light source 1) as shown in FIG. The delay information is the delay time from the output timing of the modulation signal X to the rise of the irradiation light pulse Le, and based on this, the output timing of the timing signal A can be matched with the light emission timing of the light source 1. In this way, the timing signal A is set to “H” at the same timing as the irradiation light pulse Le, and is set to “L” after the pulse width Tw. Then, the timing signal B is set to "H" at the same time as the timing signal A becomes "L", and is set to "L" after the pulse width Tw.

Further, the signal generation unit 41Ab repeatedly generates and outputs the modulation signal X and the timing signals A and B a predetermined number of times, then outputs the received light data output instruction signal to the area sensor 21 and outputs the distance calculation instruction signal to the distance calculation unit 42. Output.

The adjustment control unit 41Aa generates delay adjustment signals 1 and 2 for controlling the delay amount of the delay elements 1 and 2 based on the delay values 1 and 2 from the time measurement units 1 and 2.

Specifically, the delay value 1 and the delay value 2 are compared, and the delay adjustment signal 2 is generated so that the delay value 2 becomes the same as the delay value 1, or the delay value 1 becomes the same as the delay value 2. The delay adjustment signal 1 is generated. Alternatively, the delay adjustment signal 1 and the delay adjustment signal 2 may be generated so as to have a predetermined delay value set in advance. The delay adjustment signal does not necessarily have to be generated so that the delay value 1 and the delay value 2 match, and in short, the delay adjustment signal may be generated so that the difference between the delay value 1 and the delay value 2 becomes small.

Further, the adjustment control unit 41Aa generates a drive circuit 1 of the projection system 10, a drive circuit ON signal 1 for on / off control of the drive circuit 2, and a drive circuit ON signal 2. Then, the adjustment control unit 41Aa controls these signals to correct the deviation of the light emission timings of the light sources 1 and 2.

The detection means 30 receives the mirror 1 in which a part of the light emitted from the light source 1 is incident, the mirror 2 in which a part of the light emitted from the light source 2 is incident, and the light reflected by the mirror 1. It has a PD1 (photodiode) and a PD2 (photodiode) that receives the light reflected by the mirror 2.

That is, the mirror 1 is arranged so as to reflect a part of the light from the light source 1 toward the PD1. The mirror 2 is arranged so as to reflect a part of the light from the light source 2 toward the PD 2. The remaining portion (most) of the light emitted from the light source 1 and the remaining portion (most) of the light emitted from the light source 2 are projected as irradiation light pulses Le1 and Le2, respectively, via the projection optical system (not shown). To.

The PD1 receives the light reflected by the mirror 1, converts it into an electric signal, and outputs the PD signal 1 to the time measuring unit 1. The PD2 receives the light reflected by the mirror 2, converts it into an electric signal, and outputs the PD signal 2 to the time measuring unit 2.

The time measurement unit 1 measures the time difference between the rising timings of the modulation signal X and the PD signal 1, and outputs the time difference as the delay value 1. The time measuring unit 2 measures the time difference between the rising timings of the modulated signal X and the PD signal 2, and outputs the time difference as the delay value 2. Each time measurement unit can be realized by a circuit called a TDC (Time to Digital Converter) circuit.

Here, when the modulation signal X is output from the signal generation unit 41Ab, the light source is turned on with the delay of the delay element and the drive circuit, the light from the light source is received by the PD, and the PD signal is modulated from the PD. It is output with a delay from the signal X.

FIG. 12 shows the modulation signal X, the PD signal 1, the PD signal 2, the delay value 1 measured, and the delay value 2. In FIG. 12, the light source 1 lights up with a delay of td1 with respect to the modulation signal X, the PD1 signal is output to the time measurement unit 1 with a delay of td1, and the light source 2 delays td2 with respect to the modulation signal X. The PD2 signal is output to the time measuring unit 2 with a delay of td2. The time measurement unit 1 measures td1 and outputs it as a delay value 1 to the adjustment control unit 41Aa, and the time measurement unit 2 measures td2 and outputs it as a delay value 2 to the adjustment control unit 41Aa.

Hereinafter, a method of correcting the deviation of the light emission timing between the light source 1 and the light source 2 (light emission timing deviation correction processing) in the distance measuring device 1A of the modification 3 will be described with reference to FIG. The flowchart of FIG. 13 is based on a processing algorithm executed by the control device 40A. Here, the light emission timing deviation correction processing is performed periodically in consideration of performance variations over time and during manufacturing of the circuit elements and wirings constituting the drive circuits 1 and 2, but irregularly (for example, when the device is started). You may go.

In the first step S11, the adjustment control unit 41Aa outputs the delay adjustment signal 1 and the delay adjustment signal 2 so as to have the minimum delay.

In the next step S12, the light sources 1 and 2 are pulse-lit. Specifically, the signal generation unit 41Ab generates and outputs a modulated signal X having a pulse waveform as shown in FIG. The modulation signal X is input to the delay elements 1 and 2, and is output to the drive circuits 1 and 2 as the modulation signals 1 and 2 with a delay based on the delay adjustment signals 1 and 2. The modulated signal X is also output to the time measurement units 1 and 2, and the time measurement units 1 and 2 start time measurement.

Then, the drive circuits 1 and 2 generate drive currents 1 and 2 for lighting the light sources 1 and 2 based on the modulation signals 1 and 2, and a part of the light from each light source is irradiated through the projection optical system. It is projected as an optical pulse. At this time, the rest of the light from the light source 1 is reflected by the mirror 1 and incident on the PD1. Similarly, the rest of the light from the light source 2 is reflected by the mirror 2 and incident on the PD 2.

At this time, PDs 1 and 2 output PD signals 1 and 2 shown in FIG. 12 to the time measuring units 1 and 2 based on the incident light.

Here, the drive circuits 1 and 2 are accompanied by a circuit delay when the drive currents 1 and 2 are generated, but the circuit delays of the drive circuits 1 and 2 may differ due to variations in the circuit elements. Therefore, the PD signals 1 and 2 are input to the time measurement units 1 and 2 at different timings as shown in FIG.

In the next step S13, the delay values 1 and 2 are measured. Specifically, the time measurement unit 1 stops the time measurement when the PD signal 1 is input, and outputs the time from the input of the modulation signal X to the input of the PD signal 1 as the delay value 1 to the adjustment control unit 41Aa. To do. The delay value 1 is td1 in FIG. When the PD signal 2 is input, the time measurement unit 2 stops the time measurement, and outputs the time from the input of the modulation signal X to the input of the PD signal 2 as the delay value 2 to the adjustment control unit 41Aa. The delay value 2 is td2 in FIG.

In the next step S14, the adjustment control unit 41Aa determines whether or not the delay values 1 and 2 are equal. Specifically, when the delay values 1 and 2 are equal, the measured delay value is output as delay information to the signal generation unit 41Ab, and the light emission timing deviation correction process is completed. On the other hand, if the delay values 1 and 2 are different, the process proceeds to S15.

In the next step S15, the light emission timing of the light source is adjusted. Specifically, the adjustment control unit 41Aa adjusts at least one of the delay adjustment signals 1 and 2 based on the difference between the delay values 1 and 2.

For example, when the delay value 1 is larger than the delay value 2, the delay adjustment signal 2 is increased, and the output delay of the modulated signal 2 is adjusted to be large. When the delay value 2 is larger than the delay value 1, the delay adjustment signal 1 is increased. Is increased so that the output delay of the modulated signal 1 is increased. Further, the delay adjustment signals 1 and 2 may be adjusted so that the delay values 1 and 2 approach (preferably match) the preset delay values. In short, at least one of the delay adjustment signals 1 and 2 may be adjusted so that the difference between the delay values 1 and 2 becomes small.

In this way, the deviation of the light emission timings of the light sources 1 and 2 can be corrected (suppressed). When step S15 is executed, the process returns to step S12.

That is, since the deviation of the light emission timings of the light sources 1 and 2 is suppressed, the distance error is reduced and accurate distance measurement is performed even in the distance measuring device 1A of the modification 3 in which the light from the light sources 1 and 2 is superimposed and projected. It becomes possible to do.

<< Modification 4 >>
FIG. 14 schematically shows the configuration of the distance measuring device 1B of the fourth embodiment. In the distance measuring device 1B, as shown in FIG. 14, the detecting means 30A has a single PD (photodiode), the timing control means 41B has a single time measuring unit, and the adjusting control unit 41Ba has a single time measuring unit. It has a delay value holding unit.

Further, here, the mirror 1 guides a part of the light from the light source 1 to the PD, and the mirror 2 guides a part of the light from the light source 2 to the PD. That is, a part of the light from the light source 1 and a part of the light from the light source 2 are incident on the same PD. Although the two mirrors 1 and 2 are provided in FIG. 14, a single mirror having the functions of the mirrors 1 and 2 may be provided instead.

Hereinafter, a method of correcting the deviation of the light emission timing between the light source 1 and the light source 2 (light emission timing deviation correction processing) in the distance measuring device 1B of the modified example 4 will be described with reference to FIG. The flowchart of FIG. 15 is based on a processing algorithm executed by the control device 40B. Here, the light emission timing deviation correction processing is performed periodically in consideration of performance variations over time and during manufacturing of the circuit elements and wirings constituting the drive circuits 1 and 2, but irregularly (for example, when the device is started). You may go.

In the first step S21, the adjustment control unit 41Ba of the control device 40B outputs the delay adjustment signal 1 and the delay adjustment signal 2 so as to have the minimum delay.

In the next step S22, the light source 1 is pulse-lit. Specifically, the adjustment control unit 41Ba sets the drive circuit ON signal 1 to “H” and the drive circuit ON signal 2 to “L” so that only the light source 1 can be turned on.

The signal generation unit 41Bb generates and outputs a modulated signal X having a pulse waveform as shown in FIG. The modulation signal X is input to the delay elements 1 and 2 and is output to the drive circuits 1 and 2 as the modulation signals 1 and 2 with a delay based on the delay adjustment signals 1 and 2. The modulated signal X is also output to the time measurement unit, and the time measurement unit starts time measurement.

Then, since the drive circuit ON signal 1 is "H", the drive circuit 1 generates a drive current 1 for lighting the light source 1 based on the modulation signal 1, and the irradiation light pulse Le1 is emitted from the light source 1. Will be done. On the other hand, in the drive circuit 2, since the drive circuit ON signal 2 is “L”, the drive current 2 is not generated and the light source 2 remains off. A part of the light from the light source 1 is projected through the projection optical system (not shown), and the rest is reflected by the mirror 1 and incident on the PD. At this time, the PD signal is output from the PD to the time measuring unit based on the incident light.

In the next step S23, the delay value 1 is measured. Specifically, the time measurement unit stops the time measurement when the PD signal is input, and outputs the time from the input of the modulation signal X to the input of the PD signal as a delay value to the adjustment control unit 41Ba. The adjustment control unit 41Ba holds this delay value in the delay value holding unit. Here, the delay value held by the delay value holding unit is set to the delay value 1.

In the next step S24, the light source 2 is pulse-lit. Specifically, the adjustment control unit 41Ba sets the drive circuit ON signal 1 to “L” and the drive circuit ON signal 2 to “H” so that only the light source 2 can be turned on. The signal generation unit 41Bb generates and outputs a modulated signal X of the pulse waveform shown in FIG. The modulation signal X is input to the delay elements 1 and 2 and is output to the drive circuits 1 and 2 as the modulation signals 1 and 2 with a delay based on the delay adjustment signals 1 and 2. The modulated signal X is also output to the time measurement unit, and the time measurement unit starts time measurement.

Then, since the drive circuit ON signal 2 is “H”, the drive circuit 2 generates a drive current 2 for lighting the light source 2 based on the modulation signal 2, and the irradiation light pulse Le2 is emitted from the light source 2. Will be done. On the other hand, in the drive circuit 1, since the drive circuit ON signal 1 is “L”, the drive current 1 is not generated and the light source 1 remains off. Part of the light from the light source 2 is projected through the projection optical system, and the rest is reflected by the mirror 2 and incident on the PD. At this time, the PD signal is output from the PD to the time measuring unit based on the incident light.

In the next step S25, the delay value 2 is measured. Specifically, the time measurement unit stops the time measurement when the PD signal is input, and outputs the time from the input of the modulation signal X to the input of the PD signal as a delay value to the adjustment control unit 41Ba. The delay value here is a delay value 2.

In the next step S26, it is determined whether or not the delay values 1 and 2 are equal. Specifically, the adjustment control unit 41Ba compares the delay value 1 held in the delay value holding unit with the delay value 2 measured in step S25. As a result of the comparison, when the delay values 1 and 2 are equal, the measured delay value is output as delay information to the signal generation unit 41Bb, and the light emission timing deviation correction process is completed. On the other hand, if the delay values 1 and 2 are different as a result of the comparison, the process proceeds to step S27.

In step S27, the light emission timing of the light source is adjusted. Specifically, the adjustment control unit 41Ba adjusts at least one of the delay adjustment signals 1 and 2 based on the difference between the delay values 1 and 2.

For example, when the delay value 1 is larger than the delay value 2, the delay adjustment signal 2 is increased, and the output delay of the modulated signal 2 is adjusted to be large. When the delay value 2 is larger than the delay value 1, the delay adjustment signal 1 is increased. Is increased so that the output delay of the modulated signal 1 is increased. Further, the delay adjustment signals 1 and 2 may be adjusted so that the delay values 1 and 2 approach (preferably match) the preset delay values. In short, at least one of the delay adjustment signals 1 and 2 may be adjusted so that the difference between the delay values 1 and 2 becomes small.

In this way, the deviation of the light emission timings of the light sources 1 and 2 can be corrected (suppressed). When step S27 is executed, the process returns to step S22.

That is, since the deviation of the light emission timings of the light sources 1 and 2 is suppressed, it is possible to reduce the distance error and perform accurate distance measurement in the distance measuring device 1B that superimposes and projects the light from the light sources 1 and 2. It becomes.

As described above, in the distance measuring device 1B of the modified example 4, it is possible to realize a highly accurate distance measurement at low cost by configuring a number of PDs and a time measuring unit smaller than the number of light sources.

The distance measuring devices 1A and 1B of the modified examples 3 and 4 described above include a plurality of light sources (for example, two light sources 1 and 2) and a plurality of drive circuits (for example, two drive circuits 1) for driving the plurality of light sources. A correction system that corrects the deviation between the light emitting system 10 including 2), the light receiving system 20 that receives the light projected from the light projecting system 10 and reflected by the object, and the light emitting timing (lighting timing) of a plurality of light sources. And have.

In this case, the detection error can be reduced by receiving the light projected from the light projecting system 10 and reflected by the object by the light receiving system 20 in a state where the deviation of the light emitting timings of the plurality of light sources is corrected.

As a result, the accuracy of measuring the distance to the object can be improved.

Further, the correction system includes a detection means for detecting a part of light from each of the plurality of light sources, and a control device for correcting the deviation based on the detection result by the detection means.

In this case, the deviation of the light emission timings of the plurality of light sources can be directly and accurately corrected by using the detection means for detecting a part of the light from each light source.

Further, a plurality of modulation signals (for example, modulation signals 1 and 2) for driving the plurality of light sources are input to the plurality of drive circuits, respectively, and the control device controls the lighting timing of each of the plurality of light sources and the light sources. Includes an adjusting means (timing control means) for adjusting the input timing of the modulated signal to the drive circuit based on the detection timing by the detecting means when is lit.

In this case, the measurement accuracy of the distance to the object can be improved by a simple configuration.

Further, the adjusting means adjusts the input timing of the modulated signal to the drive circuit so that the time difference between the lighting timing and the detection timing becomes small between the light sources.

In this case, a simple method of generating a common (single) modulation signal X that is the source of the modulation signals 1 and 2 and adjusting the output timing of the modulation signal X to the drive circuits 1 and 2 is used. It is possible to correct the deviation of the light emission timings of the light sources 1 and 2.

Further, the adjusting means includes an adjustment control unit that generates an adjustment signal for adjusting the input timing of the modulation signal to the drive circuit based on the time difference between the lighting timing and the detection timing, and drives the modulation signal according to the adjustment signal. It is preferable to have adjusting elements (delay elements 1 and 2) for adjusting the input timing to the circuit.

Further, the detection means includes a light guide unit having an optical member (for example, mirrors 1 and 2) equal to or less than the number of light sources that guides light from each of a plurality of light sources (for example, light sources 1 and 2), and the light guide unit. It is preferable to include a light receiving portion having a light receiving element (for example, a photodiode or a phototransistor) which is equal to or less than the number of light sources for receiving the light guided by the light source.

When the light receiving unit has a smaller number of light receiving elements than the light source, it is preferable that the control device can switch the input / non-input of the modulated signal to the light source for each light source.

Further, as the optical member of the light guide unit, a branching element that branches the light from the light source into transmitted light and reflected light may be used instead of the mirror. In this case, for example, the transmitted light from the branching element can be projected and the reflected light can be incident on the PD.

Further, the light guide unit may have a condensing element (for example, a condensing lens or a condensing mirror) on the optical path between the optical member (for example, a mirror or a branch element) and the light receiving element.

Further, the light from the light source may be directly incident on the light receiving element without providing the light guide portion.

Further, the distance measuring methods of the modifications 3 and 4 are distance measuring methods for measuring the distance to an object, in which one of a plurality of light sources (for example, light sources 1 and 2) is turned on (light source 1). A first detection step of detecting light from the one light source, and a first calculation step of calculating a first time difference which is a time difference between the lighting timing of one light source and the detection timing in the first detection step. , A second detection step of lighting the other light source (light source 2) among the plurality of light sources to detect the light from the other light source, and the lighting timing of the other light source and the detection timing in the second detection step. A second calculation step of calculating the second time difference, which is the time difference of the above, a step of correcting the difference in lighting timing of the first and other light sources based on the first and second time differences, and the first and other light sources. Includes a step of turning on a light source, projecting light, receiving light reflected by an object, and calculating the distance to the object.

In this case, the detection error is reduced by receiving the light projected from the light projecting system 10 and reflected by the object by the light receiving system 20 in a state where the deviation of the lighting timing (light emission timing) of the plurality of light sources is corrected. it can.

As a result, the accuracy of measuring the distance to the object can be improved.

When there are a plurality of other light sources, it is preferable to perform a cycle including a second detection step, a second calculation step, and a correction step for each other light source. In this case, it is possible to correct the deviation of the light emission timing between one light source and all the other light sources.

<< Modification 5 >>
FIG. 16 shows a block diagram of the timing control means 51A included in the control device of the distance measuring device of the modified example 5.

In the timing control means 51A of the modification 5, as shown in FIG. 16, modulation signals 1 and 2 are generated based on the clock signal, and delay control of the modulation signals 1 and 2 is performed based on the adjustment data 1 and 2. It is controlled in clock units.

More specifically, the timing control means 51A adjusts based on the clock generation unit 51Aa that generates the reference clock signal, the drive circuits ON signals 1 and 2 that control the on / off of the drive circuits 1 and 2, and the delay values 1 and 2. The adjustment control unit 51Ab that generates data 1 and 2 and the modulation signals 1 and 2 are generated based on the clock signal, the adjustment data 1 and 2, and the start signal, and the timing signals A and B are further generated based on the clock signal and the start signal. , A signal generation unit 51Ac that generates a light receiving data output instruction signal and a distance calculation instruction signal.

FIG. 17 shows a method in which the signal generation unit 51Ac generates modulation signals 1 and 2 based on the clock signal and adjustment data 1 and 2.

Here, the case where the adjustment data 1 is “8” and the adjustment data 2 is “10” is shown, and the case where the pulse width is “8” is shown. In the signal generation unit 51Ac, for example, when a start signal is input from the ECU, the built-in start counter starts counting. When the value of the counter becomes "8", which is the same as the value of the adjustment data 1, the modulation signal 1 is changed to the "H" level. After that, counting is started by another pulse width counter 1, and when the pulse width reaches "8", the level is changed to "L". The pulse width counter 1 is reset to "1" and starts counting again, and when it reaches "8", the modulated signal 1 is changed to the "H" level. This is repeated to generate the modulated signal 1.

On the other hand, the modulated signal 2 changes the modulated signal 2 to the “H” level when the count value of the start counter becomes “10”, which is the same as the value of the adjustment data 2. After that, counting is started by another pulse width counter 2, and when the pulse width reaches "8", the level is changed to "L". The pulse width counter 2 is reset to "1" and starts counting again, and when it reaches "8", the modulated signal 2 is changed to the "H" level. This is repeated to generate the modulated signal 2.

Since the modulation signals 1 and 2 are output according to the values of the adjustment data 1 and 2 in this way, the output timing of the modulation signals 1 and 2 can be adjusted by adjusting the adjustment data 1 and 2, and the light source 1 It is possible to correct the deviation of the light emission timing of 2.

As described above, since the modulation signals 1 and 2 are generated by the logic circuit using the clock signal, the modulation signals 1 and 2 can be generated with a small-scale circuit configuration.

In the distance measuring device of the modified example 5 described above, the control device further includes a clock generation unit 51Aa for generating a clock and a counter for counting the clock, and the adjusting means (timing control means 51A) counts the counter. The input timing of the modulated signal to the drive circuit is adjusted based on the value, the light emission timing of each of the plurality of light sources, and the time difference (each delay value) of the detection timing by the detection means when the light source is turned on.

<< Modification 6 >>
FIG. 18 shows a block diagram of the timing control means 61A included in the control device of the distance measuring device of the modified example 6. In the modification 6, as shown in FIG. 18, adjustment data 1 and 2 are input to the clock generation unit 61Aa, and clocks 1 and 2 are generated and output by the clock generation unit 61Aa. The clocks 1 and 2 are output with their phases changed according to the adjustment data 1 and 2.

FIG. 19 shows a method in which the signal generation unit 61Ac generates the modulation signal 1 and the modulation signal 2 based on the clock signals 1 and 2 and the adjustment data 1 and 2.

Here, the case where the adjustment data 1 is “8” and the adjustment data 2 is “10.5” is shown, and the case where the pulse width is “8” is shown. In the signal generation unit 61Ac, for example, when a start signal is input from the ECU, the built-in start counter 1 starts counting with the clock 1 (clock signal 1). When the value of the start counter 1 becomes “8”, which is the same as the value of the adjustment data 1, the modulation signal 1 is changed to the “H” level. After that, counting is started by another pulse width counter 1, and when the pulse width reaches "8", the level is changed to "L". The pulse width counter 1 is reset to "1" and starts counting again, and when it reaches "8", the modulated signal 1 is changed to the "H" level. This is repeated to generate the modulated signal 1.

On the other hand, the modulation signal 2 is generated based on the clock 2 (clock signal 2), but when the adjustment data 2 of "10.5" is input to the clock generation unit 61Aa, the fractional part "0.5", that is, Clock 2 is generated and output with a phase delay of 1/2 clock. As a result, as shown in FIG. 19, the clock phase is delayed by 1/2 from the clock 1. The modulation signal 2 is generated by using this clock 2. In the signal generation unit 61Ac, for example, when a start signal is input from the ECU, the built-in start counter 2 starts counting at the clock 2. When the count value of the start counter 2 reaches the integer value “10” of the adjustment data 2, the modulation signal 2 is changed to the “H” level. After that, counting is started by another pulse width counter 2, and when the pulse width reaches "8", the level is changed to "L". The pulse width counter 2 is reset to "1" and starts counting again, and when it reaches "8", the modulated signal 2 is changed to the "H" level. This is repeated to generate the modulated signal 2.

As described above, the clock generation unit 61Aa generates the phase-adjusted clocks 1 and 2, the clock 1 generates the modulation signal 1, and the clock 2 generates the modulation signal 2, thereby generating the modulation signals 1 and 2. The output timing of the above can be adjusted with an accuracy shorter than the time of the clock width, and the emission timings of the light sources 1 and 2 can be adjusted more accurately, so that the distance measurement error can be further reduced.

In the distance measuring device of the modified example 6 described above, the control device is based on the light emission timing of each of the plurality of light sources and the time difference (each delay value) of the detection timing by the detection means when the light source is turned on. A clock generation unit 61Ac that generates a plurality of clocks having different phases and a plurality of counters that count the plurality of clocks are further included, and the adjusting means (timing control means 61A) includes the count values of the plurality of counters and the above. The input timing of the modulated signal to the drive circuit is adjusted based on the time difference.

In the above embodiment and each modification, an area sensor is used as the photodetector of the light receiving system, but the present invention is not limited to this, and for example, a plurality of light receiving elements (for example, a photodiode or a phototransistor) arranged one-dimensionally are used. A line sensor including the above or a single light receiving element may be used. In this case, for example, using a scanning projection optical system, the output signal (waveforms are substantially the same) of the light receiving element when a plurality of light sources corrected for the deviation of the light emission timing are simultaneously emitted as a reference value. The light receiving timing at the light receiving element may be obtained based on the timing at which the output signal matches the threshold value, and the distance from the light receiving timing and the light emitting timing of the light source to the object may be obtained. In this case as well, the detection error can be reduced, and the measurement accuracy of the distance to the object can be improved.

Further, in the above-described embodiment and each modification, the projection system does not have to have a projection optical system. That is, the light from the light source may be directly projected.

That is, the distance measuring device and the distance measuring method of the present invention can be widely applied to all distance measuring techniques using TOF (Time of Flight).

Further, the distance measuring device and the distance measuring method of the present invention can also be used for object recognition for recognizing a two-dimensional shape or a three-dimensional shape of an object, and object detection for detecting the presence or absence of an object.

Further, the distance measuring device of the present invention is not limited to the use mounted on a moving body, but can also be used for a purpose mounted on a stationary object or a device alone.

In addition, the numerical values, shapes, and the like used in the description of the above-described embodiment can be appropriately changed without departing from the spirit of the present invention.

The thinking process that led to the invention of the above-described embodiment and each modified example will be described below.

Conventionally, the target space is irradiated with modulated light, the distance to the target is obtained from the phase difference between the light reflected from the target and the irradiation light existing in the target space, and the value of each pixel represents the distance. A distance measuring device using a distance image sensor (area sensor) for generating a dimensional distance image is known.

In this distance measuring device, the stronger the light irradiating the target space, the stronger the reflected light, so that the SN ratio of the received signal of the distance image sensor increases and the measurement accuracy improves. Therefore, a method is known in which a plurality of light sources are used as an irradiation means for the target space and the light intensity is increased by superimposing the light.

For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 2015-108629) discloses an optical range finder having a laser range finder that irradiates pulsed light using a plurality of light sources (laser diodes) and a plurality of drive circuits. Has been done.

In this optical ranging device, a plurality of light sources are connected to a plurality of corresponding drive circuits, and by applying a common lighting signal (modulation signal) to the plurality of drive circuits, a current flows through the plurality of light sources. Light.

However, if the switching timing (current flow) of each drive circuit is different due to the performance variation of the circuit elements and wirings constituting each drive circuit, the lighting timing of each light source will be different. As a result, we have found a problem that the emission time width of a plurality of superposed lights becomes longer than the desired time width and a measurement error occurs.

Therefore, in order to solve this problem, the inventors have come up with the above-described embodiment and each modification.

1, 1A, 1B ... Distance measuring device, 10 ... Flooding system, 20 ... Light receiving system, 21 ... Area sensor, 30, 30A ... Detection means, 40, 40A, 40B ... Control device, 41 ... Timing control means (adjustment means) , Part of the control device), 42 ... Distance calculation unit (calculation means, part of the control device), 51a, 51Aa, 61a, 61Aa ... Clock generation unit.

JP-A-2015-108629

Claims (19)

A floodlight system including a plurality of light sources and a plurality of drive circuits for driving the plurality of light sources, respectively.
A light receiving system that receives light that is projected from the light projecting system and reflected by an object,
A correction system for correcting the deviation of the light emission timing of the plurality of light sources is provided.
The light receiving system includes a plurality of light receiving elements, each light receiving element has two charge storage units, and each light receiving element accumulates charges generated by the received light based on a timing signal from the correction system. ,
The correction system also corrects the deviation between the light emission timing and the timing signal, and calculates the first distance based on the light receiving result when one light source of the plurality of light sources is turned on, and the plurality of light sources. The second distance is calculated based on the light receiving result when the other light source different from the one light source and the one light source are turned on in the light source, and the first distance and the second distance are set. A distance measuring device that corrects the deviation of the light emission timings of the plurality of light sources based on the above, and corrects the deviation between the light emission timings of the one light source and the timing signal based on the first distance. The correction system, the distance measuring apparatus according to claim 1, characterized in that it comprises a control device for correcting the deviation based on the light receiving result of the light receiving system. A plurality of modulated signals for driving the plurality of light sources are input to the plurality of drive circuits, respectively.
The control device is
A calculation means for calculating the distance to the object based on the light reception result, and
The distance measuring device according to claim 2, further comprising an adjusting means for adjusting the input timing of the modulated signal to the drive circuit based on the calculation result by the calculation means. Said adjusting means based on the first distance and the second distance, the distance measuring apparatus according to claim 3, characterized in that for adjusting the input timing. The distance measuring device according to claim 4, further comprising a reference reflector which is arranged in the light projecting range of the light projecting system and whose distance can be measured by the light output of the one light source. The adjusting means
An adjustment control unit that generates an adjustment signal for adjusting the input timing based on the first and second distances.
The distance measuring device according to claim 4 or 5, further comprising an adjusting element that adjusts the input timing in response to the adjusting signal. The control device is
A clock generator that generates a clock and
Further including a counter for counting the clock,
The distance measurement according to any one of claims 4 to 6, wherein the adjusting means adjusts the input timing based on the count value of the counter and the first and second distances. apparatus. The control device is
A clock generator that generates a plurality of clocks having different phases based on the first and second distances,
Further including a plurality of counters for counting the plurality of clocks, respectively.
The adjustment means according to any one of claims 4 to 6, wherein the adjustment means adjusts the input timing based on the count values of the plurality of counters and the first and second distances. Distance measuring device. The correction system is
A detection means for detecting light from each of the plurality of light sources, and
The distance measuring device according to claim 1, further comprising a control device for correcting the deviation based on the detection result of the detecting means. A plurality of modulated signals for driving the plurality of light sources are input to the plurality of drive circuits, respectively.
The control device is
It is characterized by including an adjusting means for adjusting the input timing of the modulated signal to the drive circuit based on the light emission timing of each of the plurality of light sources and the detection timing of the detection means when the light source emits light. 9. The distance measuring device according to claim 9. The distance measuring device according to claim 10, wherein the adjusting means adjusts the input timing so that the time difference between the light emitting timing and the detection timing becomes small between the light sources. The adjusting means
An adjustment control unit that generates an adjustment signal for adjusting the input timing based on the time difference.
The distance measuring device according to claim 11, further comprising an adjusting element that adjusts the input timing in response to the adjusting signal. The control device is
A clock generator that generates a clock and
Further including a counter for counting the clock,
The distance measuring device according to claim 11, wherein the adjusting means adjusts the input timing based on the count value of the counter and the time difference. The control device is
A clock generator that generates a plurality of clocks having different phases based on the time difference,
Further including a plurality of counters for counting the plurality of clocks, respectively.
The distance measuring device according to claim 11 or 12, wherein the adjusting means adjusts the input timing based on the count values of the plurality of counters and the time difference. The detection means
A light guide unit having an optical member equal to or less than the number of the light sources, which guides a part of the light from each of the plurality of light sources.
The invention according to any one of claims 9 to 14, further comprising a light receiving unit having a detection light receiving element equal to or less than the number of the light sources, which receives the light guided by the light guide unit. Distance measuring device. The distance measuring device according to any one of claims 1 to 15, wherein the light receiving system includes an area sensor having a plurality of the light receiving elements corresponding to a plurality of pixels. The distance measuring device according to any one of claims 1 to 16 .
A mobile device including a mobile body on which the distance measuring device is mounted. A distance measuring method for measuring a distance to an object using the distance measuring device according to claim 1.
The first irradiation step of illuminating the reference reflector by turning on one of the plurality of light sources, and
The first measuring step of receiving the light irradiated in the first irradiation step and reflected by the reference reflector and measuring the distance to the reference reflector.
A second irradiation step of lighting the one light source and the other light source among the plurality of light sources to irradiate the reference reflector with light, and
A second measuring step of receiving the light irradiated in the second irradiation step and reflected by the reference reflector and measuring the distance to the reference reflector.
Based on the measurement results in the first and second measurement steps, the step of correcting the deviation of the lighting timing of the first and other light sources and the step of correcting the deviation of the lighting timing of the first and other light sources.
A distance measuring method including a step of turning on the one and other light sources, projecting light, receiving light reflected by the object, and calculating the distance to the object. A distance measuring method for measuring a distance to an object using the distance measuring device according to claim 1.
A first detection step of turning on one of a plurality of light sources to detect light from the one light source, and
A first calculation step for calculating a first time difference, which is a time difference between the light emission timing of the one light source and the detection timing in the first detection step, and
A second detection step of turning on another light source among the plurality of light sources to detect light from the other light source, and
A second calculation step of calculating a second time difference, which is a time difference between the light emission timing of the other light source and the detection timing in the second detection step, and
A step of correcting the deviation of the light emission timing of the first and other light sources based on the first and second time differences, and
A distance measuring method including a step of turning on the one and other light sources, projecting light, receiving light reflected by the object, and calculating the distance to the object.

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