JP7221029B2 - Error correction device, distance measuring device - Google Patents

Description

An embodiment of the present invention relates to technology for measuring a distance to an object by a TOF (Time Of Flight) method.

Conventionally, the TOF method is known as a technique for measuring the distance to an object based on the time from when light is projected onto the object until when the reflected light from the object is received.

In addition, as a related technology, a light emitting unit having a plurality of light emitting modes in which both the power and pulse width of the optical output are set to increase stepwise, and the reflected light of the optical signal transmitted from the light emitting unit are received. The light-receiving unit has a plurality of light-receiving modes that are set so that both the gain and the band of the circuit that emit light are set to increase stepwise, and the light-emitting unit has a plurality of operating modes that are set by combining the light-emitting modes and the light-receiving modes. and a distance measuring unit that repeatedly operates the light receiving unit and uses a non-saturated peak waveform extracted from the received light signal obtained in each operation mode to determine the distance to the object that reflected the light signal. , are known (see Patent Document 1).

JP 2015-137101 A

The power of the reflected light is attenuated by the reflectivity of the object. Also, the rising and falling timings of the pulse are detected as when the power of the reflected light exceeds a preset threshold and when it falls below the threshold. Therefore, in the conventional TOF distance measuring device, there is a problem that the pulse width of the reflected light fluctuates due to the reflectance of the object, and this fluctuation causes an error in the measured distance.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an error correcting device and a distance measuring device capable of reducing errors in the distance measured by the TOF method.

In order to solve the above-described problems, the error correction device according to the present embodiment receives reflected light of pulsed light emitted toward an object and reflected by the object, and detects timing of the reflected light, an error correction device for correcting an error in the distance measured by a distance measuring device for measuring the distance to the object based on the emission timing of the pulsed light, the error correcting device for correcting the error in the reflected light detected by the distance measuring device A pulse width acquisition unit that acquires a pulse width and a correction information in which a predetermined pulse width of reflected light and a correction value are associated with each other are referenced, and the correction information corresponds to the acquired pulse width of the reflected light. A correction value acquisition unit that acquires the attached correction value, and a distance correction unit that corrects the measured distance based on the acquired correction value.

Further, the distance measuring device according to the present embodiment includes a light source that emits pulsed light toward an object, a light receiving element that receives reflected light reflected by the object, emission timing of the pulsed light, and the a detector that detects the timing of receiving reflected light and the pulse width of the reflected light; a computing unit that calculates the distance to the object as a measured distance based on the timing of radiation and the timing of receiving light; The detected pulse width is referred to the pulse width acquisition unit and the correction information in which the predetermined pulse width of the reflected light and the correction value are associated, and the detected pulse width of the reflected light is obtained in the correction information. A correction value acquisition unit that acquires the associated correction value, and a distance correction unit that corrects the measured distance based on the acquired correction value.

According to the present invention, it is possible to reduce errors in the distance measured by the TOF method.

1 is a block diagram showing the configuration of a distance measurement system according to an embodiment; FIG. 2 is a block diagram showing the hardware configuration of an error correction device; FIG. It is a block diagram which shows the functional structure of an error correction apparatus. 4 is a flow chart showing the operation of the error correction device; 10 is a graph showing recorded distance errors; 7 is a graph showing correction values corresponding to pulse widths of reflected light; FIG. 10 is a graph showing distance error without correction; FIG. FIG. 10 is a graph showing distance error when correction is made; FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Overall Configuration and Configuration of Distance Measuring Device)
The configurations of the distance measurement system and the distance measurement device according to this embodiment will be described. FIG. 1 is a block diagram showing the configuration of the distance measurement system according to the embodiment.

As shown in FIG. 1 , the distance measurement system includes a distance measurement device 1 that measures the distance to an object T and an error correction device 2 that corrects errors in the distance measured by the distance measurement device 1 .

The distance measuring device 1 includes a light source 11 , a branching coupler 12 , a light projecting section 13 , a light receiving section 14 , a junction coupler 15 , a light receiving element 16 , a detection section 17 and a calculation section 18 . The light source 11 is a light emitter that emits pulsed light, and is a laser in this embodiment. The branching coupler 12 is connected to the light source 11, the light projecting section 13, and the joining coupler 15 by optical fibers. The junction coupler 15 is connected to each of the branch coupler 12, the light receiving section 14, and the light receiving element 16 by optical fibers.

The branching coupler 12 branches the pulsed light transmitted from the light source 11 into two, one of which is transmitted to the light projecting section 13 and the other of which is transmitted to the combining coupler 15 as reference light. The light projecting unit 13 emits the pulsed light transmitted from the branch coupler 12 to the outside of the distance measuring device 1 as emitted light. This emitted light is emitted toward the target object T, which is the object whose distance from the distance measuring device 1 is to be measured. The light receiving unit 14 is formed to receive the emitted light emitted by the light projecting unit 13 as reflected light reflected by the object T, and transmits the received reflected light to the junction coupler 15 . The merging coupler 15 merges the reference light transmitted from the branching coupler 12 and the reflected light transmitted from the light receiving section 14 and transmits them to the light receiving element 16 .

The light receiving element 16 is a sensor that receives the pulsed light transmitted by the junction coupler 15 and detects its intensity. The detection unit 17 detects the rise and fall timings of the pulses of the reference light and the reflected light detected by the light receiving element 16, respectively, using a threshold value set to a predetermined intensity in advance. The calculation unit 18 determines the timing at which the light receiving element 16 receives the reference light and the timing at which the reflected light is received, based on the rise, fall, or intermediate timing of the pulse detected by the detection unit 17. The distance to the object T is calculated by calculating the time difference and multiplying half of this time difference by the speed of light.

In such a TOF-type distance measuring device 1, attenuation of reflected light power due to the reflectance of the object T and the distance to the object T, furthermore Range errors can occur in the measured range due to variations in the sensitivity of the element 16 .

(Configuration of error correction device)
The hardware configuration and functional configuration of the error correction device 2 will be described. FIG. 2 is a block diagram showing the hardware configuration of the error correction device. FIG. 3 is a block diagram showing the functional configuration of the error correction device.

The error correction device 2 includes, as hardware, a CPU (Central Processing Unit) 21, a RAM (Random Access Memory) 22, a storage device 23, and an external I/F (Interface) 24, as shown in FIG.

The CPU 21 and RAM 22 cooperate to execute various functions described later, and the storage device 23 stores various data used for processing executed by the various functions. The external I/F 24 inputs and outputs data to and from the distance measuring device 1 as an external device. The storage device 23 stores correction information in which the pulse width of the reflected light is associated with a correction value for correcting the distance error in the measured distance for each of the short distance range, the middle distance range, and the long distance range. be.

3, the error correction device 2 has functions such as a pulse width acquisition unit 201, a pulse width correction unit 202, a distance acquisition unit 203, a distance determination unit 204, a correction value acquisition unit 205, and a distance correction unit 206. Prepare.

The pulse width acquisition unit 201 acquires the rising and falling timings of the reference light and the reflected light as pulse widths of the reference light and the reflected light from the distance measuring device 1 . A pulse width correction unit 202 corrects the pulse width of the reflected light acquired by the pulse width acquisition unit 201 . The distance acquisition unit 203 acquires the measured distance calculated by the calculation unit 18 from the distance measurement device 1 . The distance determination unit 204 determines to which distance range the measured distance acquired by the distance acquisition unit 203 belongs among a plurality of preset distance ranges. The correction value acquisition unit 205 obtains correction values stored in the storage device 23 based on the distance range to which the measured distance determined by the distance determination unit 204 belongs and the pulse width of the reflected light corrected by the pulse width correction unit 202. Get the value. A distance correction unit 206 corrects the measured distance acquired by the distance acquisition unit 203 using the correction value acquired by the correction value acquisition unit 205 .

(Operation of error correction device)
The operation of the error correction device will be explained. FIG. 4 is a flow chart showing the operation of the error correction device.

As shown in FIG. 4, first, the distance acquisition unit 203 acquires the measured distance from the distance measurement device 1 (S101), and the pulse width acquisition unit 201 acquires the pulse widths of the reference light and the reflected light from the distance measurement device 1. (S102), and the pulse width correction unit 202 corrects the pulse width of the reflected light acquired by the pulse width acquisition unit 201 (S103).

Here, the pulse width of the reflected light is corrected by the pulse width correction unit 202. W _bc is the pulse width of the reflected light after correction, W b is the pulse width of the reflected light acquired by the pulse width acquisition unit 201, and W _b is the pulse width of the reflected light. Assuming that the pulse width of the reference light acquired by the acquisition unit 201 is W _a , the pulse width of the reference light at room temperature is War , _and the preset coefficient is C, the pulse width of the reflected light after correction is W _bc . = W _b - C (W _a - W _ar ).

If the pulse width of the reflected light is corrected based on the fluctuation of the pulse width of the reference light, it is possible to reduce the measured distance due to fluctuations in the projection power of the light source 11 and fluctuations in the sensitivity of the light receiving element 16 caused by changes in the environmental temperature. Errors can be reduced.

Next, the distance determination unit 204 determines whether or not the measured distance acquired by the distance acquisition unit 203 is within a short distance range that is less than a preset first distance (S104).

When the measured distance is not within the short distance range (S104, NO), the distance determination unit 204 determines that the measured distance acquired by the distance acquisition unit 203 is equal to or greater than a second distance that is set larger than the first distance in advance. It is determined whether or not the object is within the long distance range (S105).

If the measured distance is not within the long distance range (S105, NO), that is, if the measured distance is within the middle distance range that is greater than or equal to the first distance and less than the second distance, the correction value acquisition unit 205 obtains the correction information In the middle distance range, a correction value associated with the corrected pulse width of the reflected light is acquired (S106), and the distance correction unit 206 corrects the measured distance based on this correction value (S107). Here, the measured distance is corrected by subtracting the correction value acquired by the correction value acquisition unit 205 from the measured distance acquired by the distance acquisition unit 203 .

On the other hand, if the measured distance is within the long distance range (S105, YES), the correction value acquisition unit 205 acquires a correction value associated with the corrected pulse width of the reflected light for the long distance range in the correction information. (S108), and the distance correction unit 206 corrects the measured distance based on this correction value (S107).

Further, in step S104, if the measured distance is within the short distance range (S104, YES), the correction value acquisition unit 205 associates the short distance range with the corrected pulse width of the reflected light in the correction information. (S109), and the distance correction unit 206 corrects the measured distance based on this correction value (S107).

(Correction information)
Correction information will be described. FIG. 5 is a graph showing recorded distance errors. FIG. 6 is a graph showing correction values corresponding to pulse widths of reflected light.

As described above, the correction information associates the pulse width of the reflected light with the correction value separately for each of the short distance range, the middle distance range, and the long distance range, and is stored in the storage device 23 in advance. be done.

This correction information is created based on recorded data recorded in advance. Assuming that the distance to the object T is known, the recorded data is a predetermined short distance belonging to the short distance range and a predetermined long distance belonging to the long distance range. are recorded while changing the reflectance of As shown in FIG. 5, each recorded data includes the distance error of the measured distance and the pulse width of the reflected light corresponding thereto. plotted.

Next, for each of the short distance and the long distance, a graph is created by obtaining an approximate curve from a plurality of plotted recorded data, as shown in FIG. Correction information that associates the pulse width of the reflected light with the correction value is created for each of the long-distance ranges. The middle distance range is created by linearly interpolating correction information for the short distance range and correction information for the long distance range.

(Effect of error correction device)
Effects of the error correction device will be described. FIG. 7 is a graph showing the distance error when no correction is made. FIG. 8 is a graph showing the distance error when correction is made.

According to the error correction device 2, the distance error in the measured distance as shown in FIG. 7 can be reduced as shown in FIG. In addition, while the reflectance and the measured distance affect the distance error in FIG. 7, it can be seen from FIG. 8 that the influence of the reflectance and the measured distance is reduced by the correction.

In this embodiment, the error correction device 2 is described as a device different from the distance measurement device 1, but it may be provided as one function of the distance measurement device 1. FIG. In addition, the error correction device 2 does not necessarily need to acquire information related to the error of the measured distance directly from the distance measuring device 1, but may acquire it from a database in which information related to the error of the measured distance is recorded, for example. Also good. Correction information may also be obtained from an external database.

Embodiments of the invention are provided by way of example and are not intended to limit the scope of the invention. This novel embodiment can be embodied in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

2 error correction device 201 pulse width acquisition unit 205 correction value acquisition unit 206 distance correction unit

Claims (4)

A pulsed light emitted toward an object receives reflected light reflected by the object, and a distance to the object is calculated based on the detection timing of the reflected light and the emission timing of the pulsed light. An error correction device that corrects an error in the distance measured by the distance measurement device to be measured,
a pulse width acquisition unit that acquires the pulse width of the reflected light detected by the distance measuring device and acquires the pulse width of the reference light of which part of the pulsed light is detected in the distance measuring device;
a pulse width correcting unit that corrects the pulse width of the reflected light based on the difference between the pulse width of the reference light at a predetermined normal temperature and the pulse width of the obtained reference light;
Correction value acquisition for referring to correction information in which a predetermined pulse width of reflected light and a correction value are associated, and obtaining a correction value associated with the corrected pulse width of reflected light in the correction information. Department and
and a distance correction unit that corrects the measured distance based on the acquired correction value. the correction information associates a pulse width of reflected light with a correction value for each of a plurality of distance ranges;
The error correction device further comprises a distance determination unit that determines to which of the plurality of distance ranges the measured distance belongs,
2. The error correction device according to claim 1, wherein the correction value acquiring unit acquires the correction value associated with the acquired pulse width of the reflected light for the distance range to which the measured distance belongs. The pulse width correction unit subtracts a value obtained by multiplying a difference between the pulse width of the reference light at room temperature and the pulse width of the obtained reference light by a predetermined coefficient from the pulse width of the reflected light, thereby adjusting the reflected light. 3. The error correction device according to claim 1, wherein the pulse width of light is corrected. a light source that emits pulsed light toward an object;
a light receiving element that receives reflected light reflected by the object;
a detection unit that detects the emission timing of the pulsed light, the pulse width of the reference light that is part of the pulsed light, the light reception timing of the reflected light, and the pulse width of the reflected light;
a calculation unit that calculates a distance to the object as a measured distance based on the radiation timing and the light reception timing ;
a pulse width correction unit that corrects the pulse width of the reflected light based on the difference between the pulse width of the reference light at a predetermined room temperature and the detected pulse width of the reference light;
Correction value acquisition for referring to correction information in which a predetermined pulse width of reflected light and a correction value are associated, and obtaining a correction value associated with the corrected pulse width of reflected light in the correction information. Department and
and a distance correction unit that corrects the measured distance based on the acquired correction value.

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