JP6852416B2 - Distance measuring device, mobile body, robot, device and 3D measuring method - Google Patents

Description

The present invention relates to a distance measuring device, a moving body, a robot, a device, and a three-dimensional measuring method.

In recent years, the development of distance measurement technology for measuring the distance to an object has been actively carried out.

For example, in Patent Documents 1 and 2, the distance to an object is determined based on the time from when the pulsed light is projected until the pulsed light is reflected by the object and returned, so-called TOF (Time of Flight). ) A distance measuring technique using a calculation method is disclosed.

However, in the distance measuring techniques disclosed in Patent Documents 1 and 2, it is necessary to obtain high distance resolution (improve measurement accuracy) and measure distance over a wide range (wide range of measurable distance). There was room for improvement in terms of compatibility at a high level.

The present invention comprises a light source, a light source drive unit that supplies a plurality of drive pulses including first and second drive pulses having different pulse widths to the light source at different time zones, and the light source. It includes a light receiving system that receives light projected from the system and reflected by an object, and a control system that calculates the distance to the object based on the time difference between the light emitting timing of the light source and the light receiving timing of the light receiving system. Of the first and second drive pulses, the one having a smaller pulse width has a sinusoidal shape, and the one having a larger pulse width has a rectangular wavy shape. In the control system, the first drive pulse is supplied to the light source. The distance to the object calculated from the time difference obtained in the first time zone and the time difference calculated from the time difference obtained in the second time zone in which the second drive pulse is supplied to the light source. It is a distance measuring device characterized by obtaining three-dimensional information using the distance to an object.

According to the present invention, it is possible to obtain a high distance resolution and to measure a distance over a wide range at a high level.

It is an external view of the traveling body equipped with the distance sensor which concerns on one Embodiment of this invention. It is a block diagram for demonstrating the structure of the travel management apparatus. It is a figure for demonstrating the structure of a distance sensor. It is a figure for demonstrating the projection system. It is a figure for demonstrating the pulse control signal. It is a figure for demonstrating the light source drive signal. It is a figure for demonstrating the light receiving system. It is a figure for demonstrating the signal between a 3D information acquisition part and an image sensor. It is the schematic of one frame in a distance sensor. It is a timing chart for explaining one frame of a sine wave modulation system (four-phase system). It is a timing chart for explaining one frame of the rectangular wave modulation system (two-phase system). It is a figure which shows the configuration example of 1 frame in a distance sensor. It is a figure which shows the other configuration example of 1 frame in a distance sensor. It is a figure which shows the structure of one frame of Patent Document 1 and the structure of one frame of this embodiment. It is a timing chart for explaining the aliasing method. It is a timing chart for demonstrating the aliasing method in the presence of ambient light. It is a block diagram for demonstrating the configuration of a voice / alarm generator. It is a figure which shows an example of the structure of the 3D information acquisition part. It is a figure which shows an example of the structure which distributes charge to two places with respect to one light receiving part. It is a figure which shows an example of the structure of a position control device. It is a figure which shows an example of the structure of the voice synthesizer. It is a figure which shows an example of the structure of the alarm signal generator.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the appearance of the traveling body 1 equipped with the distance sensor 20 as the distance measuring device of one embodiment. The traveling body 1 transports the luggage to the destination unmanned. In this specification, in the XYZ three-dimensional Cartesian coordinate system, the direction orthogonal to the road surface will be described as the Z-axis direction, and the forward direction of the traveling body 1 will be described as the + X direction.

Here, as an example, the distance sensor 20 is attached to the front portion of the traveling body 1 and obtains three-dimensional information on the + X side (front) of the traveling body 1. The area that can be measured by the distance sensor 20 is also referred to as a measurement area.

As shown in FIG. 2 as an example, the traveling body 1 is provided with a display device 30, a position control device 40, a memory 50, a voice / alarm generator 60, and the like. These are electrically connected via a bus 70 capable of transmitting data.

Here, the travel management device 10 is composed of the distance sensor 20, the display device 30, the position control device 40, the memory 50, and the voice / alarm generator 60. That is, the travel management device 10 is mounted on the traveling body 1. Further, the travel management device 10 is electrically connected to the main controller 80 of the traveling body 1.
The main controller 80 is an arithmetic unit for executing a program that controls the entire traveling body 1.
The position control device 40 controls the three-dimensional information acquisition unit 203 based on the instruction from the main controller 80, calculates the position information of the traveling body 1 based on the information from the three-dimensional information acquisition unit 203, and calculates the calculation result. This is a device that transmits information to the main controller 80.
The position control device 40 is composed of a memory in which a program for executing the above operation is stored, an arithmetic unit for executing this program, a memory used for executing the program, and the like (see FIG. 20).

As shown in FIG. 3 as an example, the distance sensor 20 includes a light projecting system 201, a light receiving system 202, a three-dimensional information acquisition unit 203, and the like. And these are stored in the housing. This housing has a window through which light projected from the light projecting system 201 and light reflected by an object and directed toward the light receiving system 202 passes, and glass is attached to the window.
The three-dimensional information acquisition unit 203 is a device for calculating and obtaining three-dimensional information (distance information) based on the control of the light projecting system 201 and the light receiving system 202 and the signal from the light receiving system 202, and the distance sensor 20 is used. It functions as a control system to control.
The three-dimensional information acquisition unit 203 is composed of a memory in which a program for executing the above operation is stored, an arithmetic unit for executing this program, a memory used for executing the program, and the like (see FIG. 18).

The light projecting system 201 is arranged on the −Z side of the light receiving system 202. As shown in FIG. 4, the light projecting system 201 includes a light source 21, a light source driving unit 25, and the like, as shown in FIG. 4 as an example.

The light source 21 is turned on and off by the light source driving unit 25. Here, the LED is used as the light source 21, but the present invention is not limited to this, and other light sources such as a semiconductor laser (end face emitting laser or surface emitting laser) may be used. The light source 21 is arranged so as to emit light in the + X direction. In the following, the signal generated by the light source driving unit 25 for driving the light source 21 is referred to as a “light source driving signal”.

The light source driving unit 25 generates a light source driving signal (see FIG. 6) based on the pulse control signal (see FIG. 5) from the three-dimensional information acquisition unit 203. This light source drive signal is transmitted to the light source 21 and the three-dimensional information acquisition unit 203. The light source drive signal output to the light source 21 is a pulse control signal from the three-dimensional information acquisition unit 203 amplified so that the light source 21 can emit light. That is, the light source driving unit 25 functions as an amplifier. In the following, the light source drive signal is also referred to as a “drive pulse”.

As a result, the light source 21 emits pulsed light having a pulse width instructed by the three-dimensional information acquisition unit 203. The pulsed light emitted from the light source 21 is set in the three-dimensional information acquisition unit 203 so that the duty is 50% or less. Further, in the following, the light emitted from the light source 21 is also referred to as a “projection wave” or a “projection pulse”.

When the traveling body 1 is driven, the main controller 80 of the traveling body 1 sends a position control start request to the position control device 40. Then, when the traveling body 1 reaches the target position, the main controller 80 of the traveling body 1 sends a position control end request to the position control device 40.

When the position control device 40 receives the position control start request and the position control end request, the position control device 40 sends them to the three-dimensional information acquisition unit 203.

A part of the light emitted from the distance sensor 20 and reflected by the object returns to the distance sensor 20. Hereinafter, for convenience, the light reflected by the object and returned to the distance sensor 20 is also referred to as “reflected light from the object”.

The light receiving system 202 detects the reflected light from the object. As an example, the light receiving system 202 includes an imaging optical system 28, an image sensor 29, and the like, as shown in FIG.

The imaging optical system 28 is arranged on the optical path of the reflected light from the object and collects the light. Here, the imaging optical system 28 is composed of one lens, but may be composed of two lenses, three or more lenses, or a mirror optical system. You may.

The image sensor 29 receives the reflected light from the object via the imaging optical system 28. The output signal (analog signal) of the image sensor 29 is converted into a digital signal by an ADC (analog digital converter) and sent to the three-dimensional information acquisition unit 203. Here, as the image sensor 29, an area image sensor in which light receiving units for each pixel are two-dimensionally arranged is used. Hereinafter, the reflected light from the object received by the image sensor 29 is also referred to as a “received wave” or a “received pulse”.

The image sensor 29 has two charge storage units for each light receiving unit (for example, a photodiode or a phototransistor), and when the TX1 signal is at a high level, one of the charges converted by photoelectric in the light receiving unit is used. When the TX2 signal is at a high level, the charge charged by the light receiving unit is stored in the other charge storage unit. Further, the image sensor 29 does not accumulate charges when the TXD signal is at a high level, and sets the amount of charges accumulated in the two charge storage units to 0 when the reset signal is at a high level.

The three-dimensional information acquisition unit 203 reaches the object based on the time difference between the modulation frequency control unit that controls the modulation frequency, which is the frequency of the drive pulse applied to the light source 21, and the emission timing of the light source 21 and the light reception timing of the image sensor 29. Includes a distance image generation unit that calculates the distance of and generates a distance image that is three-dimensional information of an object.

As shown in FIG. 8 as an example, the three-dimensional information acquisition unit 203 outputs a TX1 signal, a TX2 signal, a TXD signal, and a reset signal to the image sensor 29.

FIG. 9 shows a schematic view of one frame of the distance sensor 20. Basically, two or more TOF detections with different modulation frequencies (detection using the TOF calculation method) are performed, distance information with high distance resolution is acquired by TOF detection on the high frequency side, and TOF detection on the low frequency side is performed. Dealiasing is performed by determining the aliasing component included in the TOF detection information on the high frequency side. This content is disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2015-501927).

Here, an example in which one frame is composed of two subframes using different modulation frequencies will be described. The modulation frequency (frequency of one drive pulse) in one subframe is the first frequency f1, and the modulation frequency (frequency of the other drive pulse) in the other subframe is the second frequency f2.

The three-dimensional information acquisition unit 203 performs TOF detection at the first frequency f1 and stores the phase information in the memory in the distance image generation unit. Next, the modulation frequency control unit switches from the first frequency f1 to the second frequency f2, and performs TOF detection by the second frequency f2. Here, it is assumed that the relationship is that the first frequency f1> the second frequency f2. Contrary to the above, TOF detection at the second frequency f2 may be performed, and then TOF detection at the first frequency f1 may be performed.

Here, two TOF methods called "sine wave modulation method" and "square wave modulation method" will be described.

First, in the sine wave modulation method, the received wave is detected by dividing it into three or more in time, and each signal obtained is used to set the delay time Td of the input timing of the received wave with respect to the output timing of the floodlight wave. Obtained by calculating the phase difference angle.

As an example, a phase difference calculation method of a four-phase sine wave modulation method will be described with reference to FIG. With the one-frame configuration shown in FIG. 10, signals (A0, A90, A180, A270) obtained by dividing the received pulse into four phases of 0 °, 90 °, 180 °, and 270 ° are acquired, and the following (1) Find the phase difference angle Φ using the equation.
Φ = arctan {(A90-A270) / (A0-A180)} ... (1)

The delay time Td can be obtained from the equation (2) using the phase difference angle Φ.
Td = Φ / 2π × T (T = 2T0, T0: pulse width of drive pulse) ・ ・ ・ (2)

The ideal projection waveform for improving the distance measurement performance for such a phase difference calculation method is a sinusoidal waveform. Therefore, in the sine wave modulation method, as the name implies, the light source is driven by using a sine wave modulation signal (drive pulse).

On the other hand, in the "square wave modulation method", the received wave is detected by dividing it into two or more in time, and each signal obtained is used to delay the input timing of the received wave with respect to the output timing of the floodlight Td. Ask for ´.

As an example, a two-phase rectangular wave modulation method will be described with reference to FIG. With the one-frame configuration shown in FIG. 11, a signal (B0, B180) obtained by dividing the received wave into two phases of 0 ° and 180 ° is acquired, and the delay time Td'is obtained using the following equation (3). be able to.
Td'= {B180 / (B0 + B180)} x T1 (T1: pulse width of drive pulse) ... (3)

The ideal projection waveform for improving the distance measurement performance for such a phase difference calculation method is a rectangle. Therefore, in the square wave modulation method, as the name implies, the light source is driven by using a square wave modulation signal (drive pulse).

In Patent Document 1, TOF detection of the sine wave modulation method is performed for both the first frequency and the second frequency, and I = (A0-A180), Q = (A90-A270) I. The main purpose is to perform aliasing (removal of aliasing components) using the codes of the value and the Q value.

FIG. 12 shows a configuration diagram of one frame in the distance sensor 20 of the present embodiment.

The distance sensor 20 performs TOF detection by the sine wave modulation method for the first frequency f1, and TOF detection by the square wave modulation method for the second frequency f2 lower than the first frequency f1. .. The reason will be explained below.

Although it depends on the type of light source, for example, when a laser diode (LD) is used as the light source, if the pulse width of the modulation signal (drive pulse) is less than 10 ns (for example, the modulation frequency is on the high frequency side), the rise and fall will occur. The effect of waveform blunting becomes large, and the emission pulse (pulse light) has a shape close to a sinusoidal waveform. On the other hand, if the pulse width of the modulated signal is 10 ns or more (for example, the modulation frequency is on the low frequency side), the emission pulse has a shape close to a rectangle.

Here, in order to obtain high distance resolution, it is effective to perform TOF detection by the high frequency side modulation frequency (for example, TOF detection using a drive pulse having a relatively short pulse width), and the emission pulse by the high frequency side modulation frequency. Is close to a sine wave waveform, so it is compatible with the TOF detection of the sine wave modulation method.

On the other hand, when TOF is detected by the low frequency side modulation frequency for aliasing (for example, when TOF is detected using a drive pulse with a relatively long pulse width), the emission pulse is close to a rectangular waveform, so the rectangular wave modulation method is used. Good compatibility.

Therefore, by adopting a frame configuration (see FIG. 12) as in the present embodiment, it is possible to improve the detection accuracy in both TOF detection by the high frequency side modulation frequency and TOF detection by the low frequency side modulation frequency. Become.

Next, a more effective frame configuration example in the distance sensor 20 of the present embodiment will be described.

Here, as the structure of the image sensor used for general TOF detection, as described above, the structure in which the electric charge is distributed to two places in one light receiving unit is the mainstream (see, for example, Japanese Patent No. 5110520). ), It is assumed that such an image sensor will be used.
FIG. 19 shows an example of a structure in which electric charges are distributed to two places in one light receiving unit. As shown in FIG. 19, first and second charge storage units 20a and 20b are arranged on both sides of the light receiving unit 100. A first charge transfer unit 30a is arranged between the light receiving unit 100 and the first charge storage unit 20a. A second charge transfer unit 30b is arranged between the light receiving unit 100 and the second charge storage unit 20b.
The light receiving unit 100 converts the received light into a signal charge. A part of this signal charge is sent to the first charge storage unit 20a via the first charge transfer unit 30a, and the other part is sent to the second charge storage unit 20b via the second charge transfer unit 30b.

In this case, by adopting the frame configuration shown in FIG. 13, it is possible to reduce the time required for TOF detection by the second frequency f2 required for aliasing. That is, while the pixel has two charge distribution destinations, the phase information required for TOF detection by the second frequency f2 is also two, so that the signals of 0 ° and 180 ° are transmitted within the subframe period. Only one exposure period is required for acquisition. This effect will be described with reference to FIG. 14 in comparison with the frame configuration of the prior art (Patent Document 1).

In the present embodiment, it is possible to generate a surplus of the frame configuration as shown in FIG. 14 with respect to the prior art (Patent Document 1). This time can be used as it is for improving the frame rate, or can be used for improving the S / N by extending the signal storage time, and the performance of the distance sensor can be improved.

Next, the outline of the aliasing method in the present embodiment will be described with reference to FIG.

It is assumed that there is an object to be measured at a distance of d (obj) shown in the upper part of FIG. At this time, the phase difference of Td1 (obj) is detected by the phase difference detection operation by the four-phase sinusoidal modulation method TOF with the first frequency f1. At this time, since Td1 (obj) includes a delay equal to or longer than the period of the first frequency f1, the distance is erroneously determined as dA.

Here, paying attention to the phase difference detection by the two-phase rectangular wave modulation method TOF at the second frequency f2 in the lower part of FIG. 15, Td2 (obj) is detected. At this time, since Td2 (obj) does not include a delay equal to or longer than the period of the second frequency f2, the distance d (obj) can be detected. Therefore, by linking Td1 (obj) and Td2 (obj), the object remains as the distance measurement information of the distance resolution of the first frequency f1 without erroneously detecting the distance (without erroneously determining dA). It becomes possible to detect the distance d (obj) to.

Here, since the frequency is low in TOF detection by the second frequency f2, there is a large variation in the distance measurement performance of the first frequency f1, but the distance resolution should be at most a distance d1 minute. Variations are acceptable.

Further, d1 and d2 (maximum range of each modulation frequency in the TOF method) shown in FIG. 15 are
d1 = 2T0 × c / 2
d2 = T1 × c / 2
Will be.

The example shown in FIG. 15 is an example in the case where there is no ambient light. Therefore, an implementation method in an environment with ambient light will be described with reference to FIG.

When there is ambient light as shown in FIG. 16, the stored signal amount includes the received light component and the disturbance light component.

In the case of TOF detection by the sinusoidal modulation method at the first frequency f1, the difference between each signal is calculated when deriving Td1, so the disturbance light component (Na) is natural in the TOF calculation as shown below. Can be canceled.
Molecule in {} of the above formula (1): A90-A270 = (Sa90 + Na) -Sa270 + Na) = Sa90-Sa270
Fraction in {} of equation (1) above: A0-A180 = (Sa0 + Na)-(Sa180 + Na) = Sa0-Sa180

On the other hand, in the case of TOF detection by the two-phase square wave modulation method at the second frequency f2, unlike the sine wave modulation method, the disturbance light component cannot be canceled naturally as described below.
B180 / (B0 + B180) = (Sb180 + Nb) / (Sb0 + Sb180 + 2Nb)

Therefore, in the case of the two-phase pulse modulation method, there is a method of extracting a disturbance light component (Nb) by separately photographing a non-emission frame. However, increasing the number of acquired frames does not make it possible to simplify the frame configuration, which is an advantage of the present invention.

In order to take advantage of the present invention, the ambient light intensity (x) may be determined without increasing the number of acquired frames. Therefore, the ambient light intensity (x) is obtained by the following method.
(1) In the calibration step in which no ambient light enters, the received luminance value (Ya0) at the first frequency f1 and the received luminance value (Yb0) at the second frequency f2 are measured and stored. Assuming that the emission intensity at the first frequency f1 is Pa0, the emission intensity at the second frequency f2 is Pb0, and the subject reflectance, the distance to the subject, and other loss of the optical system are R0, the received luminance value (Ya0), The received luminance value (Yb0) can be expressed as follows.
Ya0 = Pa0 x R0
Yb0 = Pb0 × R0

Finally, in this calibration step, the value of Ya0 / Yb0 = Pa0 / Pb0 may be stored (the emission intensity ratio at the first and second frequencies f1 and f2 is stored).

Next, the processing in an actual usage environment with ambient light will be described. First, the received luminance value (Ya) is derived from the acquired data of the sinusoidal modulation method at the first frequency f1. This received luminance value is, for example,
Ya = √ {(A0-A180) ² + (A90-A270) ² } ... (4)
Can be obtained as.

As can be seen from the above equation (4), the ambient light component (Na) is automatically removed from Ya. Next, the received luminance value (Yb') is derived from the acquired data of the two-phase square wave modulation method at the second frequency f2. Here, assuming that the received luminance value of the two-phase square wave modulation method that does not include ambient light is Yb, for example,
Yb'= B0 + B180 = Yb + 2Nb ... (5)
Can be obtained as.
Here, since Ya / Yb = Ya0 / Yb0, the above equation (5) is modified.
Nb can be derived from the calculation of 2Nb = Yb'-(YaYb0 / Ya0).
Therefore, by using this method, it is possible to remove the ambient light without using a non-emission frame at the time of TOF detection of the two-phase square wave modulation method.

Returning to FIG. 2, when the position control device 40 receives the three-dimensional information from the three-dimensional information acquisition unit 203, the position control device 40 displays the three-dimensional information on the display device 30. Further, the position control device 40 performs position control based on the three-dimensional information so that the position of the traveling body 1 becomes a predetermined position.

As an example, the voice / alarm generator 60 includes a voice synthesizer 61, an alarm signal generator 62, a speaker 63, and the like, as shown in FIG.

The voice synthesizer 61 has a plurality of voice data, and when it receives information on danger from the position control device 40, it selects the corresponding voice data and outputs it to the speaker 63.
The voice synthesizer 61 is a device composed of a memory in which a program for selecting voice data and output to the speaker 63 is stored, a calculation device for executing this program, a memory used for executing the program, and the like. There is (see FIG. 21).

When the alarm signal generation device 62 receives the danger information from the position control device 40, the alarm signal generation device 62 generates a corresponding alarm signal and outputs the corresponding alarm signal to the speaker 63.
The alarm signal generation device 62 is a device composed of a memory in which a program for creating an alarm signal and outputting to the speaker 63 is stored, an arithmetic unit for executing this program, a memory used for executing the program, and the like. (See FIG. 22).

The distance sensor 20 of the present embodiment described above supplies the light source 21 and a plurality of (for example, two) drive pulses including the first and second drive pulses having different pulse widths to the light source 21 at different time zones. The time difference between the light emitting system 201 including the light source driving unit 25, the light receiving system 202 that receives the light projected from the light projecting system 201 and reflected by the object, and the light emitting timing of the light source 21 and the light receiving timing of the light receiving system 202. It is equipped with a control system that calculates the distance to the object based on.

Of the first and second drive pulses, the smaller pulse width is preferably sinusoidal, and the larger pulse width is preferably rectangular wavy. The "sine wave shape" includes a sine wave and a waveform similar to a sine wave. “Square wave” includes a square wave and a waveform similar to a square wave.

In this case, the drive pulse having a smaller pulse width that increases the rising and falling waveform bluntness of the floodlight waveform has a sinusoidal shape, and the drive pulse having a larger pulse width that reduces the waveform bluntness has a rectangular wavy shape. Therefore, each drive pulse and the corresponding projection pulse are similar. Therefore, the pulse width of each drive pulse and the pulse width of the corresponding projection pulse are also approximated.

Therefore, it is possible to reduce the measurement error when calculating the distance to the object from the delay time of the light receiving timing of the light receiving pulse (reflected light pulse) of the light receiving system 202 with respect to the input timing of each drive pulse to the light source 21. That is, the detection accuracy can be improved when either the first drive pulse or the second drive pulse is used.

As a result, it is possible to obtain high distance resolution and measure distance over a wide range at a high level.

Further, the light receiving system 202 includes an image sensor 29 (imaging element) that receives light reflected by an object, converts it into an electric signal, divides the electric signal in time, and distributes the electric signal into a plurality of time-by-time signals. , The control system obtains the time difference between the light emission timing of the light source 21 and the light reception timing of the image sensor 29 using the signal, calculates the distance from the time difference to the object, and acquires the three-dimensional information of the object. The three-dimensional information acquisition unit 203 including the acquisition unit 203 includes the distance to the object calculated from the time difference obtained in the first time zone in which the first drive pulse is supplied to the light source 21, and the second drive. Three-dimensional information is obtained using the distance to the object calculated from the above time difference obtained in the second time zone in which the pulse is supplied to the light source 21.

In this case, a decrease in shooting time or exposure time can be suppressed.

Further, in the first time zone, the number of temporal divisions of the electric signal is Na (Na ≧ 3), each divided signal is Ci (1 ≦ i ≦ Na), and I = Σ [Ci × sin {( 2π / Na) × (i-1))} (1 ≦ i ≦ Na), Q = Σ [Ci × cos {(2π / Na) × (i-1)}] (1 ≦ i ≦ Na), φ = Arctan (I / Q), when the pulse width of the first drive pulse is T0 and the time difference is Td, Td = φ / 2π × 2T0 is established.

In this case, a higher distance resolution can be obtained more reliably.

Further, in the second time zone, the number of temporal divisions of the electric signal is Nb (Nb ≧ 2), each divided signal is Di (1 ≦ i ≦ Nb), and the time difference is Td ′. When the pulse width T1 of the drive pulse of is set so that the electric signal is divided into Di and Di + 1 which are in phase with each other in time, Td'= Di + 1 / (Di + Di + 1) × T1 is satisfied. To do.

In this case, the distance can be measured more reliably over a wide range.

Further, it is preferable that the image sensor 29 distributes electric charges to N locations (for example, N ≧ 2) with respect to one light receiving portion.

Further, in the second time zone, it is preferable that the number of temporal divisions of the electric signal is N or less.

Further, N = 2, the three-dimensional information acquisition unit 203 detects the ambient light intensity using the luminance information obtained from the image sensor 29 in the first time zone, and the image sensor 29 in the second time zone. It is preferable to remove the ambient light component from the luminance information obtained from.

Further, the lengths of the plurality of time zones in which the plurality of drive pulses are supplied to the light source 21 may be the same or different.

Further, in the above embodiment, the frequencies (modulation frequencies) of the plurality of drive pulses are different, but they may be the same, in short, the pulse widths of the plurality of drive pulses may be different.

Since the traveling body 1 has the distance sensor 20, the traveling body 1 can travel with excellent reliability.

Further, in the three-dimensional measurement method of the present embodiment, the first light emitting step of supplying the first drive pulse to the light source 21 to emit light, and the first light emitting step, the light source 21 emits light and is reflected by an object. In the first light receiving step of receiving light, the second light emitting step of supplying a second driving pulse having a pulse width different from that of the first driving pulse to the light source 21 to emit light, and the second light emitting step. It includes a second light receiving step of receiving the light emitted from the light source 21 and reflected by the object, and a step of obtaining three-dimensional information of the object based on the light receiving results in the first and second light receiving steps. ..

Of the first and second drive pulses, the smaller pulse width is preferably sinusoidal, and the larger pulse width is preferably rectangular wavy.

In this case, the drive pulse having a smaller pulse width at which the rising and falling waveform bluntness of the floodlight waveform becomes large is a sinusoidal shape, and the drive pulse having a large pulse width at which the waveform bluntness becomes small is a square wave. Therefore, each drive pulse and the corresponding projection pulse are similar. Therefore, the pulse width of each drive pulse and the pulse width of the corresponding projection pulse are also approximated.

Therefore, it is possible to reduce the measurement error when calculating the distance to the object from the delay time of the light receiving timing of the light receiving pulse with respect to the input timing of each drive pulse to the light source 21. That is, the detection accuracy can be improved when either the first drive pulse or the second drive pulse is used.

As a result, it is possible to obtain high distance resolution and measure the distance over a wide range at a high level, and it is possible to measure the three-dimensional object information with high accuracy.

In the above embodiment, the case where one frame is divided into a plurality of subframes has been described, but the present invention is not limited to this. For example, the TOF detection of the high frequency / sine wave modulation method may be performed in one frame, and the TOF detection of the low frequency / square wave modulation method may be performed in another frame.

In the above embodiment, three or more drive pulses having different pulse widths may be supplied to the light source at different time zones. In this case, three or more drive pulses having different pulse widths are divided into a side having a large pulse width and a side having a small pulse width, the drive pulse on the side having a small pulse width has a sinusoidal shape, and the drive pulse on the side having a large pulse width has a rectangular wave shape. It is preferable to do so.

Further, in the above embodiment, the light projection system is a non-scanning type, but a scanning type including an optical deflector (for example, a polygon mirror, a galvano mirror, a MEMS mirror, etc.) may be used. In this case, for example, a plurality of lights emitted from a plurality of light emitting units (line light sources) arranged in one direction are scanned in a direction non-parallel to the arrangement direction of the light emitting units (for example, a direction perpendicular to the direction). A distance image may be generated by receiving light from a plurality of light receiving units (line image sensors) arranged in parallel in the arrangement direction corresponding to the plurality of light emitting units. Alternatively, the light from a single light emitting unit may be two-dimensionally scanned by the light deflecting means, and the reflected light from the object may be received by the area image sensor to generate a distance image.

Further, in the above embodiment, the case where a single LED (light emitting unit) is made to emit pulse light and the reflected light from the object is received by the area image sensor has been described, but the present invention is not limited to this.

For example, a plurality of two-dimensionally arranged light emitting units may be sequentially pulse-lit, and the reflected light from the object of each light emitting pulse may be sequentially received by a single light receiving unit to generate a distance image.

Further, for example, in the case of simply measuring the distance to a certain object instead of the three-dimensional information (distance image) of the object, even if the light emitting part of the light projecting system and the light receiving part of the light receiving system are both singular. good.

Further, in the above embodiment, the position control device 40 may perform a part of the processing in the three-dimensional information acquisition unit 203, or the three-dimensional information acquisition unit 203 performs a part of the processing in the position control device 40. You may.

Further, in the above embodiment, the case where the travel management device 10 includes one distance sensor 20 has been described, but the present invention is not limited to this. A plurality of distance sensors 20 may be provided depending on the size of the traveling body, the measurement area, and the like.

Further, in the above embodiment, the case where the distance sensor 20 is used for the travel management device 10 for monitoring the traveling direction of the traveling body has been described, but the present invention is not limited to this. For example, it may be used as a device for monitoring the rear or side surface of a traveling body.

Further, in the above embodiment, the case where the distance sensor 20 is used for a traveling body (moving body) has been described, but the present invention is not limited to this. For example, it may be used for a moving body such as an aircraft or a ship, a robot in which a distance sensor 20 autonomously moves while confirming its own position, or a three-dimensional measuring device for measuring a three-dimensional shape of an object.

As can be seen from the above description, 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).

That is, the distance measuring device and the distance measuring method of the present invention can also be used for acquiring two-dimensional information of an object and detecting the presence or absence of an object.

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 embodiment by the inventors will be described below.

A so-called "TOF (Time of Flight) sensor" that emits modulated reference light to one of the three-dimensional sensors, detects the time until the reference light is reflected by the subject and returns, and obtains the distance has already been introduced. It is known, and among various three-dimensional sensing methods, development for various applications has been promoted recently due to its responsiveness in principle.

For example, it is expected to be applied to gesture recognition and position control of moving objects such as robots and automobiles.

The TOF method includes a direct TOF method that directly detects the time difference between the emission timing and the light reception timing of the reference light, and an indirect TOF method that detects the time difference from an operation using a light reception signal. Generally, the indirect TOF method is used. Is said to be advantageous for short-range measurement.

In the indirect TOF method, it is known that the higher the modulation frequency of the reference light, the better the measurement distance resolution. On the other hand, when the reflected light returns to the sensor with a delay of one cycle or more of the reference light, it is determined. It is not possible to determine how many cycles the delay has occurred, and generally the distance within the delay of one cycle is the measurable distance.

Further, if the modulation frequency is increased with the aim of improving the measurement distance resolution, there is a problem that the measurable distance range is short and limited.

Patent Documents 1 and 2 disclose an aliasing method using two types of modulation frequencies in order to avoid this problem.

In Patent Document 1, the phase shift of the reflected light from the subject is detected by two frequencies, and aliasing (delay of one cycle or more) is determined. Phase signals of 0 °, 90 °, 180 °, and 270 ° are acquired for any frequency, and the difference between each signal amount: I value of I = 0 ° -180 °, Q = 90 ° -270 °. , Q value code information is used to determine aliasing.

In Patent Document 2, a TOF sensor having a high distance resolution and a wide range of measurement is realized by detecting TOF by arithmetic processing using those intermediate frequencies using three or more frequencies. As an example, when the frequencies of f1, f2, and f3 are used, for example, the high frequency intermediate frequency that contributes to the distance resolution is the average value of these three frequencies, and the low frequency intermediate frequency that contributes to the wide ranging range is set. It is given by f1-f2.

However, no countermeasures are described for the shooting speed or the exposure time that is sacrificed because the TOF detection operation is required at each of the two modulation frequencies.

Therefore, as a countermeasure, the inventors have proposed the above embodiment in order to achieve both high distance resolution and distance measurement over a wide range at a high level.

1 ... traveling body (moving body), 20 ... distance sensor (distance measuring device), 21 ... light source (part of projection system), 25 ... light source driving unit (part of projection system), 28 ... imaging optics System (part of light receiving system), 29 ... Image sensor (part of light receiving system), 201 ... Light source system, 202 ... Light receiving system (light receiving means), 203 ... Three-dimensional information acquisition unit.

Special Table 2015-501927 Japanese Patent Application Laid-Open No. 2013-538342

Claims (14)

A light projection system including a light source and a light source drive unit that supplies a plurality of drive pulses including first and second drive pulses having different pulse widths to the light source at different time zones.
A light receiving system that receives light that is projected from the light projecting system and reflected by an object,
A control system for calculating the distance to the object based on the time difference between the light emission timing of the light source and the light reception timing of the light receiving system is provided.
Of the first and second drive pulses, the one having a smaller pulse width has a sinusoidal shape, and the one having a larger pulse width has a rectangular wavy shape.
In the control system, the distance to the object calculated from the time difference obtained in the first time zone in which the first drive pulse is supplied to the light source and the second drive pulse are supplied to the light source. A distance measuring device characterized in that three-dimensional information is obtained using the distance to the object calculated from the time difference obtained in the second time zone. The light receiving system includes an image pickup device that converts light reflected and received by the object into an electric signal, and divides the electric signal into a plurality of time-by-time signals.
The control system calculates the time difference with the signal, the distance measuring apparatus according to claim 1, characterized in that to calculate the distance from the difference between said time to acquire three-dimensional information of the object. In the first time zone
The number of temporal divisions of the electric signal is Na (Na ≧ 3),
Each divided signal is Ci (1 ≦ i ≦ Na),
I = Σ [Ci × sin {(2π / Na) × (i-1))}] (1 ≦ i ≦ Na),
Q = Σ [Ci × cos {(2π / Na) × (i-1)}] (1 ≦ i ≦ Na),
φ = arctan (I / Q),
The pulse width of the first drive pulse is T0,
When the time difference is Td,
The distance measuring device according to claim 2, wherein Td = φ / 2π × 2T0 is satisfied. In the second time zone,
The number of temporal divisions of the electric signal is Nb (Nb ≧ 2),
Each divided signal is divided into Di (1 ≦ i ≦ Nb),
Let the time difference be Td'
When the pulse width T1 of the second drive pulse is set to be divided into Di and Di + 1 in which the electric signal is in phase with each other,
The distance measuring device according to claim 2 or 3, wherein Td'= {Di + 1 / (Di + Di + 1)} × T1 is satisfied. The distance measuring device according to any one of claims 2 to 4, wherein the image pickup device can distribute electric charges to N locations with respect to one light receiving unit. The distance measuring device according to claim 5, wherein the number of temporal divisions of the electric signal is N or less in the second time zone. N = 2
The control system detects the ambient light intensity using the luminance information obtained from the image sensor in the first time zone, and the ambient light from the luminance information obtained from the image sensor in the second time zone. The distance measuring device according to claim 5 or 6, wherein the component is removed. The distance measuring device according to any one of claims 1 to 7, wherein the length of the first time zone is different from the length of the second time zone. The distance measuring device according to any one of claims 1 to 8, wherein the frequency of the first drive pulse is different from the frequency of the second drive pulse. The distance measuring device according to any one of claims 1 to 8, wherein the frequencies of the plurality of drive pulses are the same. A mobile body having the distance measuring device according to any one of claims 1 to 10. A robot that moves autonomously using the distance measuring device according to any one of claims 1 to 10. A device for three-dimensional measurement using the distance measuring device according to any one of claims 1 to 10. The first light emitting step of supplying the first drive pulse to the light source in the first time zone to emit light,
In the first light emitting step, the first light receiving step of receiving the light emitted from the light source and reflected by the object, and
In the first time zone, a first distance calculation step of calculating a distance from a time difference between a light emitting timing of the first light emitting step and a light receiving timing of the first light receiving step,
A second light emitting step in which a second drive pulse having a pulse width different from that of the first drive pulse is supplied to the light source in a second time zone to emit light.
A second light receiving step of receiving the light emitted from the light source and reflected by the object in the second light emitting step,
In the second time zone, the second distance calculation step of calculating the distance from the time difference between the light emission timing of the second light emitting step and the light receiving timing of the second light receiving step,
Including a step of obtaining three-dimensional information of the object based on the calculation results in the first and second distance calculation steps.
A three-dimensional measurement method characterized in that, of the first and second drive pulses, the one having a smaller pulse width has a sinusoidal shape, and the one having a larger pulse width has a rectangular wavy shape.

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