JP2015227781A - Light-of-flight ranging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation of ranging accuracy while preventing reduction of a frame rate.SOLUTION: A light-of-flight ranging device 1 controls a plurality of light-emitting elements 8a to 8n to individually emit modulation light and a plurality of light-receiving elements 11a to 11n to individually receive incident light if the modulation light emitted from the respective light-emitting elements 8a to 8n possibly interferes with modulation light emitted from a different device. By splitting a space (light emission area) in which the light-emitting elements 8a to 8n emit the modulation light, the probability of the occurrence of light emission interference can be reduced in a period in which a light emission period of the device 1 overlaps a light emission period of the different device.

Description

  The present invention emits modulated light into a space, receives incident light including reflected light reflected by the object, accumulates charges, and based on the accumulated state of the charges from the own device to the object. The present invention relates to an optical flight type distance measuring device that measures a distance.

  Conventionally, modulated light (ranging light) is emitted into the space, incident light including reflected light reflected by the object is received and accumulated, and charges are accumulated from the self-device based on the accumulated state of the charges. An optical flight (TOF: Time of Flight) type distance measuring device for measuring the distance to an object is provided. The optical flight-type distance measuring device measures the distance from the device itself to the object for each pixel using the phase difference between the modulated light and the reflected light. When a plurality of this type of optical flight rangefinders exist in the same detection space, there is a space (light emitting area) where modulated light is emitted from its own device and a space where modulated light is emitted from other devices. Overlap and interference between modulated lights (light emission interference) may occur. When light emission interference occurs, there is an error in the phase difference between the modulated light emitted from the device itself and the reflected light reflected by the target object due to the influence of the modulated light emitted from the other device. There is a problem that the ranging accuracy is lowered. To deal with this problem, for example, Patent Document 1 discloses that a random additional period is added after the light emission period to form a light emission pattern at random. In the method of Patent Document 1, the modulated light emitted from another device is canceled through an exposure period of several thousand to several hundred thousand cycles, thereby preventing the occurrence of light emission interference and preventing the distance measurement accuracy from being lowered.

JP2013-76645A

  However, although the technique disclosed in Patent Document 1 can prevent a decrease in distance measurement accuracy, the period is extended in the time direction, so the frame rate (processing speed per frame) decreases. A new problem arises.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an optical flight-type distance measuring device that can prevent a decrease in distance measurement accuracy while preventing a decrease in frame rate. It is in.

  According to the first aspect of the present invention, the plurality of light emitting elements emit modulated light having a predetermined light emission frequency in different spaces. The light emission control circuit individually emits modulated light from the plurality of light emitting elements. The plurality of light receiving elements provided corresponding to the plurality of light emitting elements receive incident light including reflected light reflected from the object by the modulated light emitted from the corresponding light emitting elements, and accumulate electric charges. The light reception control circuit individually operates the plurality of light receiving elements and measures the distance from the own device to the object based on the charge accumulation state in the plurality of light receiving elements. In this case, the light emission control circuit performs a divided light emission process in which modulated light is emitted from a plurality of light emitting elements in a time division manner in a light emission period, and a space in which the modulated light is emitted from the plurality of light emitting elements is divided.

  When the space (light emitting area) where the modulated light is emitted from the light emitting element of its own device overlaps the space where the modulated light is emitted from the light emitting element of the other device, light emission interference between the modulated light occurs. In this case, in the configuration in which the space in which the modulated light is emitted during the light emission period is always the same, the influence of the modulated light emitted from the other device is all over the period in which the light emission period of the own device overlaps the light emission period of the other device. receive. As a result, there is a possibility that light emission interference occurs in the entire period in which the light emission periods overlap. On the other hand, in the present invention, by performing the divided light emission process, the space in which the modulated light is emitted during the light emission period is divided and switched. If the space in which the modulated light is emitted is divided and switched during the light emission period, it is not affected by the modulated light emitted from the other device in at least a part of the period in which the light emission period of the own device and the light emission period of the other device overlap. Period may occur. As a result, if a period that is not affected by the modulated light emitted from the other device occurs in at least a part of the period in which the light emission periods overlap, no light emission interference occurs during that period.

  That is, by performing the divided light emission process, it is possible to shorten (suppress) the period during which the light emission interference occurs compared to the case where the divided light emission process is not performed. Thereby, it is possible to reduce the possibility that an error occurs in the phase difference between the modulated light and the reflected light, and it is possible to prevent the distance measurement accuracy from being lowered. At this time, since it is not necessary to add a period corresponding to the conventional addition period, it is possible to prevent a decrease in the frame rate.

Functional block diagram showing an embodiment of the present invention Functional block diagram showing the configuration of the image sensor Timing chart (1) The figure which shows the aspect by which the optical flight type distance measuring device is mounted in the vehicle Diagram showing the light emitting area The figure which shows the aspect which light emission interference generate | occur | produces (the 1) The figure which shows whole light emission processing and division | segmentation light emission processing The figure which shows the kind of modulated light where emission interference is assumed Flow chart (Part 1) Flow chart (Part 2) Timing chart (2) The figure which shows the aspect which light emission interference generate | occur | produces (the 2) The figure which shows the aspect which the light emission period overlaps (the 1) The figure which shows the aspect which the light emission period overlaps (the 2) The figure which shows the aspect which the light emission period overlaps (the 3)

  Hereinafter, an embodiment in which the present invention is applied to an optical flight rangefinder that can be mounted on a vehicle will be described with reference to the drawings. The optical flight-type distance measuring device 1 is a sensor in which one image sensor is configured as one pixel, and emits (irradiates) modulated light (ranging light) having a predetermined emission frequency into space. Then, the optical flight-type distance measuring device 1 receives incident light including reflected light, which is reflected by the modulated light emitted from the target object, and accumulates charges. Measure the distance to. The object is, for example, a person, a vehicle, a wall, or the like.

  The optical flight type distance measuring device 1 includes a control unit 2, a light emitting unit 3, and a light receiving unit 4. As a hardware configuration, the control unit 2 includes a light emission control circuit 5 that controls the light emission operation of the light emission unit 3, a light reception control circuit 6 that controls the light reception operation of the light reception unit 4, and a storage unit 7.

  The light emitting unit 3 includes light emitting elements 8a to 8n as a plurality of light sources, and a plurality of driving circuits 9a to 9n corresponding to the light emitting elements 8a to 8n in a one-to-one relationship. Each drive circuit 9a-9n inputs the light emission command signal from the light emission control circuit 5 simultaneously or individually. When the light emission command signal is input, the drive circuits 9a-9n output the light emission command to the corresponding light emitting elements 8a-8n. The drive circuits 9a to 9n are supplied with electric power from a vehicle battery (not shown) mounted on the vehicle via an electric power supply circuit (not shown). Each of the drive circuits 9a to 9n converts the power supplied from the vehicle battery via the power supply circuit into power of the amount of power (current amount) indicated by the light emission command signal input from the light emission control circuit 5, It supplies to each light emitting element 8a-8n corresponding.

  Each light emitting element 8a-8n is comprised from the device which can perform high-speed modulation (high-speed blink), such as LED (Light Emitting Diode) and a laser, for example. When the light emitting elements 8a to 8n receive light emission commands from the corresponding driving circuits 9a to 9n, the power supplied from the driving circuits 9a to 9n is driven as the operating power, and the modulated light is set in advance. Flashes. The space where each of the light emitting elements 8a to 8n emits modulated light is set so as not to overlap the space where the other light emitting elements 8a to 8n emit modulated light. That is, the plurality of light emitting elements 8a to 8n emit modulated light in different spaces.

  The light receiving unit 4 includes a selection circuit 10, a plurality of light emitting elements 8a to 8n of the light emitting unit 3, and a plurality of light receiving elements 11a to 11n corresponding one-to-one. When receiving the light reception command signal from the light reception control circuit 6, the selection circuit 10 outputs the light reception command to each of the light receiving elements 11a to 11n simultaneously or individually. In addition, when the read command signal is input from the light receiving control circuit 6, the selection circuit 10 outputs the read command to each of the light receiving elements 11a to 11n simultaneously or individually.

  When each light receiving element 11a to 11n receives a light reception command from the selection circuit 10, the light receiving elements 11a to 11n wait for reception of incident light including reflected light reflected by the object with the modulated light emitted from each light emitting element 8a to 8n. Transition from a possible state to a state where light can be received). Each of the light receiving elements 11a to 11n includes a plurality of imaging elements 12a to 12n that are regularly arranged. As shown in FIG. 2, each of the imaging elements 12 a to 12 n includes a photoelectric conversion element 13 and a charge accumulation unit 14. When the photoelectric conversion element 13 receives incident light including reflected light reflected by the object, the photoelectric conversion element 13 converts the received incident light into an electric charge corresponding to the amount of light received. The charge storage unit 14 includes first to fourth unit storage units 15a to 15d, and the charge converted by the photoelectric conversion element 13 is synchronized with the modulation period (period of one frame) of the modulated light. Distribute. The charge storage unit 14 stores the distributed charges in the first to fourth unit storage units 15a to 15d, respectively.

  In addition, when the light receiving elements 11a to 11n receive a read command from the selection circuit 10, the light receiving elements 11a to 11n receive the charge amounts of the charges accumulated in the first to fourth unit accumulation units 15a to 15d of the imaging elements 12a to 12n. Output to the control circuit 4. The light reception control circuit 4 outputs a read command to the selection circuit 10 at a predetermined time interval, and reads out the charge amount of the charges accumulated in the first to fourth unit storage units 15a to 15d at a predetermined time interval. . Then, the light reception control circuit 4 calculates the delay time (phase difference) between the modulated light and the reflected light using the read charge amount, and measures the distance from the own device to the object for each pixel. The distance from the own device measured by the light receiving control circuit 4 to the object is output to the outside from an external output terminal (not shown), for example, so that the distance from the own device to the object is a predetermined distance (reference When the value is less than (value), an operation such as a warning is performed.

  Next, the control of the light emitting operation of the light emitting unit 3 and the light receiving operation of the light receiving unit 4 will be described with reference to FIG. The control unit 2 controls the light emission operation of the light emission unit 3 by the light emission control circuit 5 and the light reception operation of the light reception unit 4 by the light reception control circuit 6 by the microcomputer executing a control program stored in advance. .

  In the light emission period within one frame period, the control unit 2 converts the light emission command signal from the light emission control circuit 5 to each of the drive circuits 9a to 9a as a rectangular wave having a period of Ts, an on time of Ts / 2, and an off time of Ts / 2. 9n, and the light emission from each of the light emitting elements 8a to 8n is repeated for Ts / 2 hours and stopped for Ts / 2 hours. The control unit 2 is not limited to outputting the light emission command signal as a rectangular wave, and may output the light emission command signal as a sine wave or a sawtooth wave.

The control unit 2 outputs a light reception command signal from the light reception control circuit 6 to the selection circuit 10 during the light emission period, and accumulates charges in the first to fourth unit storage units 15a to 15d of the light receiving elements 11a to 11n. To control. In other words, the control unit 2 assumes that the time divided into four equal to the period Ts of the light emission command signal is T ₁ , T ₂ , T ₃ , and T ₄ in order, and is synchronized with the light emission of the light emitting elements 8a to 8n. The first unit accumulation unit 15a is turned on for Ts / 2 hours (accumulation Q1). The control unit 2, the second unit storage section 15b Ts / 2 hours to turn on by _{T 1} delayed timing from ON of the first unit storage portion 15a (accumulation Q2). Further, the control unit 2 turns on the third unit accumulation unit 15c for Ts / 2 time (accumulation Q3) at a timing delayed by (T ₁ + T ₂ ) from turning on the first unit accumulation unit 15a. Further, the control unit 2 turns on the fourth unit storage unit 15d for Ts / 2 hours (storage Q4) at a timing delayed by (T ₁ + T ₂ + T ₃ ) after the first unit storage unit 15a is turned on. In this way, the control unit 2 distributes the charges by shifting the period Ts by four equal intervals, and repeats the accumulation of charges whose phases are shifted by 0 degrees, 90 degrees, 180 degrees, and 270 degrees from the emission of the modulated light, respectively. .

  Generally, in order to measure the distance from its own device to an object, it is necessary to accumulate charges for a time of about several ms. On the other hand, the emission frequency (modulation frequency) of the modulated light emitted from each of the light emitting elements 8a to 8n is several tens of MHz. Therefore, one modulation period Ts is about several tens of ns. For this reason, in order to measure the distance from the own apparatus to the object, an exposure period (charge accumulation period) of several thousand to several hundred thousand cycles is required. The control unit 2 reads the charge amount stored in the first to fourth unit storage units 15a to 15d at each time interval of the exposure period.

  When the control unit 2 reads the charge amount of the charges accumulated in the first to fourth unit accumulating units 15a to 15d, it measures the distance from the own device to the object as follows. Between the modulated light emitted from each of the light emitting elements 8a to 8n and the reflected light reflected by the object and received by each of the light receiving elements 11a to 11n, the flight time during which the light reciprocates to the object Causes a delay time (phase difference). The control unit 2 calculates the delay time Td by the following equation (1), assuming that the charge amounts of the charges accumulated in the first to fourth unit accumulation units 15a to 15d are C1, C2, C3, and C4, respectively. .

Td = tan ⁻¹ [(C1-C3) / (C2-C4)] (1)
The light receiving elements 11a to 11n receive background light as incident light as well as reflected light. However, the charge of the reflected light (of the reflected light component) of the incident light depends on the delay time. 4 unit storage units 15a to 15d. For this reason, the charge amounts of the reflected light accumulated in the first to fourth unit accumulation units 15a to 15d are different. On the other hand, the electric charge by the background light (background light component) in the incident light is equally allocated to the first to fourth unit accumulating units 15a to 15d. Therefore, the charge amount of the background light accumulated in the first to fourth unit accumulating units 15a to 15d is substantially equal. In the above equation (1), the amount of charge of the background light is canceled out, so that the delay time Td can be calculated without being affected by the background light.

When calculating the delay time Td, the control unit 2 uses the calculated delay time Td, period Ts, and speed of light c to calculate the distance D from the own device to the object using the following equation (2).
D = (Td / 2π) · (c / 2Ts)
The controller 2 may read the charge amounts stored in the first to fourth unit accumulators 15a to 15d at the same time or individually. It is also possible to read over a plurality of frames. Further, in the present embodiment, the case where the charge storage unit 14 is configured by the four unit storage units 15a to 15d is exemplified, but the distance D from the own device to the object is calculated based on the charge amounts of different phases. If possible, the number of unit storage units may be any number of two or more.

  As a mode in which the optical flight type distance measuring device 1 is mounted on a vehicle, there is a mode shown in FIG. As shown in FIG. 4 (a), for example, in the aspect in which the optical flight type distance measuring device 1 is mounted on the front part and the rear part of the vehicle A, the front and rear of the vehicle A become the light emission area X of the light emitting part 3, The object is monitored. Further, as shown in FIG. 4B, for example, in the aspect in which the optical flight type distance measuring device 1 is mounted on the side portion of the vehicle A, the side of the vehicle A becomes the light emitting area of the light emitting portion 3, and the object Will be monitored. Further, as shown in FIG. 4C, for example, in the aspect in which the optical flight type distance measuring device 1 is mounted on the front side corner and the rear side corner of the vehicle A, the front side and rear side ( The periphery of the vehicle) becomes the light emitting area X of the light emitting unit 3, and is the object to be monitored. In addition, for example, the number and position of the optical flight type distance measuring device 1 mounted on the vehicle A may be any way, for example, the optical flight type distance measuring device 1 may be mounted only on the front portion of the vehicle A. Also good.

  The light emitting area X of the light emitting unit 3 is the sum of the light emitting areas of the light emitting elements 8a to 8n. That is, as shown in FIG. 5, for example, if the number of light emitting elements 8a to 8n is six (n = f), the light emitting area X of the light emitting unit 3 is the light emitting area Xa of each of the light emitting elements 8a to 8f. This is the sum of ~ Xf. The light emitting areas Xa to Xf are partitioned in the horizontal direction (direction parallel to the road surface) and may be uniform (same area) or non-uniform (different areas). The light emitting area X of the light emitting unit 3 is determined by the desired area to be monitored. That is, if there is a request to relatively increase the area to be monitored, the light emitting areas Xa to Xn of the light emitting elements 8a to 8n are determined so that the light emitting area X of the light emitting unit 3 is relatively wide. On the other hand, if there is a request to relatively reduce the area to be monitored, the light emitting areas Xa to Xn of the light emitting elements 8a to 8n are determined so that the light emitting area X of the light emitting unit 3 is relatively narrow.

  When there are a plurality of optical flight type distance measuring devices 1 in the same detection space, there is a possibility that interference (emission interference) between the modulated light emitted from the own device and the modulated light emitted from another device may occur. That is, as shown in FIG. 6A, for example, when the distance between the vehicle A and the vehicle B facing each other approaches on a straight road, the light emitting area X in front of the vehicle of the optical flight rangefinder 1 of the vehicle A and the vehicle There is a possibility that light emission interference may occur due to overlap with the light emitting area Y in front of the vehicle of the optical flight distance measuring device 1 of B. As shown in FIG. 6B, for example, when the distance between the vehicle A and the vehicle B approaches even at an intersection, the light emission area X in front of the vehicle of the optical flight type distance measuring device 1 of the vehicle A and the light of the vehicle B When the light emitting area Y in front of the vehicle of the flight-type distance measuring device 1 overlaps, light emission interference may occur. Further, as shown in FIG. 6C, for example, when the distance between the vehicle A and the vehicle B approaches in the parking lot, the light emitting area X on the right rear side of the optical flight rangefinder 1 of the vehicle A and the vehicle B There is a possibility that light emission interference may occur due to the overlap with the light emitting area Y on the left front side of the optical flight type distance measuring device 1. When the light emission interference occurs, it is influenced by the modulated light emitted from another device (for example, the optical flight type distance measuring device 1 of the vehicle B), and from its own device (for example, the optical flight type distance measuring device 1 of the vehicle A). There is a problem that an error occurs in the phase difference between the emitted modulated light and the reflected light that is reflected by the object, and the ranging accuracy is lowered.

  In consideration of the possibility that such light emission interference may occur, in the optical flight type distance measuring device 1, the control unit 2 performs an overall light emission process that does not spatially divide the light emission area X of the light emission unit 3, and light emission. The divided light emission processing for spatially dividing the light emitting area X of the unit 3 in the horizontal direction (in the direction parallel to the road surface) is switched.

  As shown in FIG. 7A, when performing the entire light emission processing, the control unit 2 simultaneously outputs a light emission command signal, simultaneously emits modulated light from each of the light emitting elements 8a to 8n, and emits the light emission command signal. The light receiving command signal is simultaneously output in synchronization with the output of the light receiving element, and the respective light receiving elements 11a to 11n receive the incident light simultaneously. On the other hand, as shown in FIGS. 7B and 7C, when performing the divided light emission processing, the control unit 2 outputs the light emission command signals individually with a time difference, and modulates light from each of the light emitting elements 8a to 8n. The light receiving command signals are individually output in synchronization with the output of the light emission command signal, and the respective light receiving elements 11a to 11n individually receive the incident light with the time difference.

  In this case, as shown in FIG. 7 (b), when performing the divided light emission processing (non-random), the control unit 2 changes the order in which the light emission command signal is output from the upper side to the lower side (in FIG. The direction of rotation is one direction from the upper side to the lower side. That is, the control unit 2 sets the light emission order of each of the light emitting elements 8a to 8n to, for example, one direction from the upper side to the lower side (the order having regularity). Therefore, in the divided light emission processing (non-random), the light emission order of the light emitting elements 8a to 8n is the same in all frames. On the other hand, as shown in FIG. 7C, the control unit 2 makes the order of outputting the light emission command signal random when performing the divided light emission processing (random). That is, the control part 2 makes the light emission order of each light emitting element 8a-8n random (it makes it an order without regularity). Therefore, in the divided light emission process (random), the light emission order of the light emitting elements 8a to 8n differs for each frame. In addition, when the divided light emission process is performed, the control unit 2 supplies the power supplied to the light emitting elements 8a to 8n that emit the modulated light, and the plurality of light emitting elements 8a that simultaneously emit the modulated light when the entire light emission process is performed. ˜8n higher than the power supplied individually.

  In addition, as shown in FIG. 8, the storage unit 7 stores the type of modulated light assumed to emit light interference with the modulated light emitted from the light emitting unit 3, and the respective frequencies (f1 to f6 in FIG. 8), A priority level is assigned and stored. The priority is the possibility that light emission interference with the modulated light emitted from the light emitting unit 3 occurs. The modulated light assumed to emit light interference with the modulated light emitted from the light emitting unit 3 includes modulated light emitted from the optical flight rangefinder 1 mounted on the vehicle, other than the optical flight rangefinder 1. Includes modulated light emitted from other devices. F1 to f6 are different values. In FIG. 8, six types of modulated light assumed to emit light interference with the modulated light emitted from the light emitting unit 3 are illustrated, but any number may be used.

Next, the operation of the above-described configuration will be described with reference to FIGS.
In the optical flight rangefinder 1, when the one-frame process is started, the control unit 2 proceeds to a light emission interference presence / absence determination process (S1). When the control unit 2 proceeds to the light emission interference presence / absence determination process, the control unit 2 sets “1” to n (a parameter indicating the type of frequency) (S11), and sets the drive frequency of the light receiving unit 4 according to n (S12). That is, the control unit 2 refers to the storage unit 7, sets the drive frequency of the light receiving unit 4 to f1, and causes the light receiving unit 4 to wait for the reception of the modulated light having the light emission frequency f1.

  Next, as shown in FIG. 11, the control unit 2 outputs a light reception command signal without outputting a light emission command signal during the light emission period, and outputs the first to first imaging elements 12 a to 12 n of the light receiving elements 11 a to 11 n. Charges are accumulated in the fourth unit accumulation units 15a to 15d (S13). At this time, if there is no other device that emits the modulated light having the emission frequency f1 around the device, the modulated light having the emission frequency f1 is not received by the light receiving unit 4 as incident light. . That is, charges corresponding to the amount of light received from only the background light are accumulated in the light receiving elements 11a to 11n. On the other hand, if another device that emits modulated light having a light emission frequency of f1 exists around the device itself, the light having a light emission frequency of f1 is received by the light receiving unit 4 as incident light. That is, charges corresponding to the amounts of received light of background light and modulated light emitted from other devices are accumulated in the respective light receiving elements 11a to 11n.

  The control unit 2 determines whether or not the modulated light emitted from the other device is received (the modulated light is detected) by determining the charge accumulation states of the light receiving elements 11a to 11n (S14). . When the control unit 2 determines that the charge accumulated in each of the light receiving elements 11a to 11 corresponds to the amount of received light of only the background light, and determines that the modulated light is not detected (S14: NO), the control unit 2 emits light at the frequency fn. It is specified that there is no possibility of interference (S15). That is, in this case, the control unit 2 specifies that there is no possibility of light emission interference occurring at the frequency f1.

  The control unit 2 determines whether or not all the frequencies (f1 to f6 in FIG. 8) stored in the storage unit 7 have been checked (S16), and determines that there is a frequency that has not been checked (S16: NO), n is incremented (S17), the process returns to the above step S12, and the processes after S12 are repeated. That is, in this case, the control unit 2 refers to the storage unit 7, switches the driving frequency of the light receiving unit 4 from f 1 to f 2, and causes the light receiving unit 4 to wait for reception of the modulated light having the light emission frequency f 2. Thereafter, when the control unit 2 specifies that there is no possibility of occurrence of light emission interference at the frequency f2, the drive frequency of the light receiving unit 4 is switched from f2 to f3, and thereafter, the above processing is repeated in the same manner. .

  If the control unit 2 determines that there is no frequency that has not been investigated, that is, that all the frequencies stored in the storage unit 7 have been investigated (S16: YES), light emission interference occurs at all the frequencies to be investigated. It is specified that there is no possibility (S18). Then, the control unit 2 determines to perform the entire light emission process (S19), ends the light emission interference presence / absence determination process, and returns.

  On the other hand, when the control unit 2 determines that the modulated light is detected because the modulated light is emitted from the other device as illustrated in FIG. 11 (S14: YES), the modulation emitted from the other device is also performed in the past several frames. It is determined whether light has been received (modulated light has been detected) (S20). When determining that the modulated light has not been detected in the past several frames (S20: NO), the control unit 2 specifies that light emission interference may occur at the frequency fn, and the light emission interference is single-shot, It is specified that the cycle in which the light emission interference occurs is not synchronized (asynchronous) (S21). Then, the control unit 2 determines to perform the divided light emission process (non-random) (S22), ends the light emission interference presence / absence determination process, and returns. If the control unit 2 determines that the modulated light has been detected even in the past several frames (S20: YES), the control unit 2 specifies that light emission interference may occur at the frequency fn, and the light emission interference is continuous (periodic). It is specified that the period in which the light emission interference occurs is synchronized (S23). Then, the control unit 2 determines that the divided light emission process (random) is to be performed (S24), ends the light emission interference presence / absence determination process, and returns.

  In this way, the control unit 2 determines whether to perform the entire light emission process, the divided light emission process (non-random), or the divided light emission process (random), ends the light emission interference presence / absence determination process, and returns. The light emitting operation of the light emitting unit 3 and the light receiving operation of the light receiving unit 4 are performed in accordance with the light emission processing performed. When performing the light emitting operation of the light emitting unit 3 and the light receiving operation of the light receiving unit 4 in accordance with the entire light emission process, the control unit 2 simultaneously emits modulated light from the light emitting elements 8a to 8n and the light receiving elements 11a to 11n. Simultaneously receives incident light. When performing the light emitting operation of the light emitting unit 3 and the light receiving operation of the light receiving unit 4 according to the divided light emission process (non-random), the control unit 2 individually modulates the modulated light from the light emitting elements 8a to 8n in a regular order. And the light receiving elements 11a to 11n individually receive incident light in a regular order. When performing the light emitting operation of the light emitting unit 3 and the light receiving operation of the light receiving unit 4 according to the divided light emission processing (random), the control unit 2 individually modulates the modulated light from the light emitting elements 8a to 8n in a non-regular order. While making it light-emit, each light receiving element 11a-11n light-receives incident light individually in the order without a regularity.

  As shown in FIG. 12, the vehicle A and the vehicle B face each other in a straight path, and a part of the light emitting area X in front of the vehicle A (light emitting areas Xe and Xf) and a part of the light emitting area Y in front of the vehicle B Are assumed, and a part of the light emission period of the vehicle A and a part of the light emission period of the vehicle B overlap as shown in FIGS. Further, it is assumed that the optical flight type distance measuring device 1 of the vehicle B performs the entire light emission process (does not have a function of performing the divided light emission process). FIG. 13 shows a case where the optical flight type distance measuring device 1 of the vehicle A performs the entire light emission processing. In this case, there is a possibility that light emission interference occurs in the entire period (t2 to t3, t6 to t7) where a part of the light emission period of the vehicle A and a part of the light emission period of the vehicle B overlap.

  On the other hand, FIG. 14 shows a case where the optical flight type distance measuring device 1 of the vehicle A performs the divided light emission processing (non-random). In this case, a period in which no light emission interference occurs occurs during a period (t2 to t3, t6 to t7) in which a part of the light emission period of the vehicle A and a part of the light emission period of the vehicle B overlap. That is, in the period (t21 to t3, t61 to t7) in which the modulated light is emitted from the light emitting elements 8e and 8f, the light emitting areas Xe and Xf and the light emitting area Y may overlap and light emission interference may occur. In the period (t2 to t21, t6 to t61) in which the modulated light is emitted from 8d, the light emission area Xd and the light emission area Y do not overlap and there is no possibility of light emission interference.

  FIG. 15 shows a case where the optical flight type distance measuring device 1 of the vehicle A performs divided light emission processing (random). Also in this case, a period in which no light emission interference occurs in a period (t2 to t3, t6 to t7) in which a part of the light emission period of the vehicle A and a part of the light emission period of the vehicle B overlap. That is, in the period (t2 to t3) in which the light emission period overlaps, in the period (t21 to t22) in which the modulated light is emitted from the light emitting element 8f, the light emission area Xf and the light emission area Y may overlap and light emission interference may occur. However, in the period (t2 to t21, t22 to t3) during which modulated light is emitted from the light emitting elements 8b and 8c, the light emitting areas Xb and Xc and the light emitting area Y do not overlap and there is no possibility of light emission interference. Further, in the period (t6 to t7) in which the light emission period overlaps, in the period (t62 to t7) in which the modulated light is emitted from the light emitting element 8e, the light emission area Xe and the light emission area Y may overlap and light emission interference may occur. However, in the period (t6 to t62) during which modulated light is emitted from the light emitting elements 8a and 8c, the light emitting areas Xa and Xc and the light emitting area Y do not overlap and there is no possibility of light emission interference.

  By performing the divided light emission processing in this way, the period during which light emission interference may occur is reduced (suppressed) and the possibility of light emission interference occurring is reduced as compared with the case of performing the entire light emission processing. In FIG. 12, the case where the vehicle A and the vehicle B face each other on a straight path has been described. However, the same applies to the case where the vehicle A and the vehicle B approach each other in an intersection or a parking lot as shown in FIG.

As described above, according to the present embodiment, the following effects can be obtained.
When it is determined that there is a possibility of light emission interference in the optical flight rangefinder 1, modulated light is emitted in a time-division manner from the plurality of light emitting elements 8a to 8n during the light emission period, and from the plurality of light emitting elements 8a to 8n. A divisional light emission process for dividing a space where modulated light is emitted is performed. Thereby, it is possible to reduce the possibility that light emission interference occurs in a period in which the light emission period of the own device and the light emission period of the other device overlap, and to prevent a decrease in distance measurement accuracy.

  Further, when there is a possibility that light emission interference occurs, the divided light emission process is performed. When there is no possibility that light emission interference occurs, the whole light emission process is performed, and the divided light emission process and the whole light emission process are switched. Thereby, it is possible to achieve both of preventing the occurrence of light emission interference by the divided light emission process and ensuring a wide detection space by the whole light emission process.

  Further, the power supplied to the light emitting elements 8a to 8n that emit the modulated light when performing the divided light emission process is individually supplied to the plurality of light emitting elements 8a to 8n that simultaneously emit the modulated light when the entire light emission process is performed. I made it higher than electric power. Thereby, when performing the division | segmentation light emission process, each light emission power of each light emitting element 8a-8n can be raised, and the required exposure period can be shortened by that much.

  In addition, the possibility of occurrence of light emission interference is determined in units of one frame. Thereby, the divided light emission processing and the whole light emission processing can be switched in units of one frame. Further, when it is determined that there is a possibility that light emission interference may occur in only one frame, the divided light emission processing (non-random) is performed. As a result, it is possible to reduce the possibility of light emission interference while omitting the process of randomly determining the light emission order. Further, when it is determined over a plurality of frames that light emission interference may occur, the divided light emission process (random) is performed. Thereby, depending on the degree of overlap of the light emitting areas, if the light emission order is always the same, it is also assumed that the possibility of light emission interference cannot be reduced, but by randomly determining the light emission order, The possibility of occurrence of light emission interference can be reduced.

  In addition, light emission interference may occur for each of the plurality of modulated lights according to the priority given to the plurality of modulated lights that are expected to cause light emission interference with the modulated light emitted from the light emitting unit 3. The presence or absence of sex was determined. As a result, the process for determining whether or not there is a possibility of occurrence of light emission interference can be efficiently determined in order from the frequency at which the light emission interference is likely to occur, and it is efficiently determined that the divided light emission process is performed. Can do.

The present invention is not limited to the above-described embodiment, and can be modified or expanded as follows.
You may apply to uses other than a vehicle.
In the split light emission process (random), in one light emission period, modulated light is emitted from a specific light emitting element a plurality of times, modulated light is not emitted from a specific light emitting element, or from some of the light emitting elements. Any light emission order may be used as long as the light emission order has no regularity, such as simultaneous emission of modulated light.

  In the drawings, 1 is an optical flight type distance measuring device, 5 is a light emission control circuit, 6 is a light reception control circuit, 7 is a storage unit, 8a to 8n are light emitting elements, and 11a to 11n are light receiving elements.

Claims (9)

A plurality of light emitting elements (8a to 8n) that emit modulated light having a predetermined light emission frequency in different spaces;
A light emission control circuit (5) for individually emitting modulated light from the plurality of light emitting elements;
A plurality of light receiving elements (11a to 11n) that are provided corresponding to the plurality of light emitting elements, receive incident light including reflected light reflected from the object by the modulated light emitted from the corresponding light emitting elements, and accumulate charges. )When,
A light receiving control circuit (6) for individually operating the plurality of light receiving elements and measuring a distance from the device to an object based on a charge accumulation state in the plurality of light receiving elements;
The light emission control circuit performs a divided light emission process in which modulated light is emitted in a time division manner from a plurality of light emitting elements in the light emission period, and a space in which the modulated light is emitted from the plurality of light emitting elements is divided. Optical flight type distance measuring device (1). In the optical flight type distance measuring device according to claim 1,
The light emission control circuit switches between the divided light emission processing and the whole light emission processing that simultaneously emits modulated light from the plurality of light emitting elements during a light emission period and does not divide a space in which the modulated light is emitted from the plurality of light emitting elements. An optical flight-type distance measuring device. In the optical flight type distance measuring device according to claim 2,
The light emission control circuit individually supplies power supplied to a light emitting element that emits modulated light when performing the divided light emission process to a plurality of light emitting elements that simultaneously emit modulated light when performing the overall light emission process. An optical flight-type distance measuring device characterized by being higher than electric power. In the optical flight type distance measuring device according to any one of claims 1 to 3,
The light reception control circuit determines whether or not light emission interference may occur based on a charge accumulation state in the plurality of light receiving elements during a period in which modulated light is not emitted from the plurality of light emitting elements,
The light emission type distance measuring device, wherein the light emission control circuit performs the divided light emission processing when the light reception control circuit determines that there is a possibility of light emission interference. In the optical flight type distance measuring device according to claim 4,
The optical flight distance measuring device, wherein the light receiving control circuit determines whether or not light emission interference may occur in units of one frame. In the optical flight type distance measuring device according to claim 5,
The light emission control circuit has regularity in the light emission order for emitting modulated light from the plurality of light emitting elements when the light reception control circuit determines that there is a possibility of light emission interference in only one frame. An optical flight-type distance measuring device that is set in a certain order. In the optical flight type distance measuring device according to claim 5 or 6,
The light emission control circuit has a regular light emission sequence for emitting modulated light from the plurality of light emitting elements when the light reception control circuit determines that light emission interference may occur over a plurality of frames. An optical flight-type distance measuring device that is set in an order that does not have any. In the optical flight type distance measuring device according to any one of claims 4 to 7,
The light reception control circuit, when there is a plurality of modulated lights that are likely to cause light emission interference with the modulated light, the plurality of modulated lights according to the priority given to the plurality of modulated lights. An optical flight-type distance measuring device characterized by determining whether or not there is a possibility of occurrence of light emission interference for each of the above. In the optical flight type distance measuring device according to claim 8,
An optical flight comprising a storage unit (7) for storing correspondence between a plurality of types of modulated light assumed to be likely to cause light emission interference with the modulated light and the frequency of the modulated light Type ranging device.

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