JP2013044690A - Distance measuring equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide distance measuring equipment that measures a distance to a target with high accuracy even if the distance between a vehicle and the target changes.SOLUTION: A light projection part 11 projects temporally modulated region light having a horizontally spreading light-emitting region and horizontal straight upper and lower end sections. A camera 12 images the region light reflected by a target, to extract upper and lower edges from the captured image and to determine first and second measurement distances on the basis of the upper and lower edges, according to the triangulation principle. When the target moves away from the vehicle, the second measurement distance is selected. When the target approaches the vehicle, the first measurement distance is selected. Even if the distance to the target changes, distance measurement accuracy can be improved.

Description

  The present invention relates to a distance measuring device that is provided in a moving body such as a vehicle and measures a distance to an object existing around the moving body.

  As a distance measuring device for measuring a distance to an object existing around a moving body such as a vehicle, for example, a device described in Japanese Patent Application Laid-Open No. 2008-157718 (Patent Document 1) is known. In this patent document 1, it has a pair of light emitting element and light receiving element which have base line length, and detects the distance and direction to a measuring object by a triangulation method. In addition, the sheet beam collected by the toroidal lens is pulse-emitted multiple times, the light receiving position is extracted from the light receiving element in synchronization with the light emission timing, the irradiation direction of the sheet beam and the incident direction of the reflected light to the light receiving element, The distance to the object is measured based on the base line length of the light emitting element and the light receiving element.

JP 2008-157718 A

  However, in the prior art described in Patent Document 1 described above, distance measurement is performed when the distance between the measurement target and the optical device does not change, and this optical device is mounted on a moving body such as a vehicle. In this case, a change in the distance between the measurement object and the optical device may occur while a plurality of pulse lights are emitted. For this reason, there is a problem that the pulsed light projected onto the measurement object cannot be extracted with high accuracy and the accurate distance cannot be measured.

  The present invention has been made to solve such a conventional problem, and the object of the present invention is to measure the object even when the distance between the moving object and the object to be measured changes. An object of the present invention is to provide a distance measuring device capable of measuring a distance to an object with high accuracy.

  In order to achieve the above object, a distance measuring device according to the present invention has a light emitting region that extends in the horizontal direction around a moving body, and has a linear end portion in which an upper end portion and a lower end portion are horizontal. Projection means for projecting time-modulated pulse light, and imaging means for imaging the pulse light projected by the light projection means and reflected by the object. In addition, a detection unit that extracts pulsed light from an image captured by the imaging unit, a control unit that controls light projection by the light projection unit, imaging by the imaging unit, and detection by the detection unit, and a pulse detected by the detection unit An edge detection unit that detects an edge of light and a distance calculation unit that calculates a distance to the object based on an image position of the edge detected by the edge detection unit.

  The edge detection means includes an upper edge detection section that detects the upper edge of the pulsed light and a lower edge detection section that detects the lower edge, and the distance calculation means is based on the upper edge detected by the upper edge detection section. And calculating a distance to the object as the second measurement distance based on the first distance calculation unit that calculates the distance to the object as the first measurement distance and the lower edge detected by the lower edge detection unit. Includes a 2-distance calculator.

  Further, the time change of the first measurement distance and the time change of the second measurement distance are calculated, respectively, and based on the comparison result of the calculation result and the magnitude of the first measurement distance and the second measurement distance, Distance selection means for selecting one of the one measurement distance or the second measurement distance is provided.

  Since the distance measuring device according to the present invention selects one of the first measuring distance and the second measuring distance as the measuring distance, the distance between the moving body and the measuring object changes. Even if it exists, it becomes possible to measure the distance to a measuring object with high precision.

It is a block diagram which shows the structure of the distance measuring device which concerns on 1st Embodiment of this invention. It is a block diagram which shows the detailed structure of the synchronous detection process part used with the distance measuring device which concerns on 1st Embodiment of this invention. It is a timing chart which shows change of each signal in a synchronous detection processing part used with a distance measuring device concerning a 1st embodiment of the present invention. It is explanatory drawing which shows a mode that the distance to a measuring object is measured with the distance measuring device which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the image imaged with the camera of the distance measuring device which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the principle which measures the distance to a measuring object with the distance measuring device which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the image which imaged the measuring object currently spaced apart with respect to the vehicle by the distance measuring device which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the image which imaged the measuring object which has approached with respect to the vehicle by the distance measuring device which concerns on 1st Embodiment of this invention. It is a flowchart which shows the procedure of the distance measurement process by the distance measuring device which concerns on 1st Embodiment of this invention. It is a flowchart which shows the procedure of the synchronous detection process by the distance measuring device which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows distance resolution in case the depression angle of the camera by the distance measuring device which concerns on embodiment of this invention is 0 degree. It is explanatory drawing which shows distance resolution in case the depression angle of the camera by the distance measuring device which concerns on embodiment of this invention is (alpha) degrees. It is a block diagram which shows the structure of the distance measuring device which concerns on 2nd Embodiment of this invention. It is explanatory drawing which shows a mode that the distance to a measuring object is measured with the distance measuring device which concerns on 2nd Embodiment of this invention. It is explanatory drawing which shows the image imaged with the camera of the distance measuring device which concerns on 2nd Embodiment of this invention. It is a timing chart which shows change of each signal in a synchronous detection processing part used with a distance measuring device concerning a 2nd embodiment of the present invention.

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

[Description of First Embodiment]
FIG. 1 is a block diagram showing a configuration of a distance measuring apparatus 100 according to the first embodiment of the present invention. As shown in FIG. 1, the distance measuring device 100 is mounted on a moving body such as a vehicle, and projects a region light toward a measurement target that is a target for distance measurement around the vehicle. (Light projecting means) 11, a camera (imaging means) 12 that captures an image of a measurement object irradiated with area light, and a light projection control section (control means) that controls irradiation of area light by the light projecting section 11. 13, a synchronous detection processing unit (detection means) 14 for performing synchronous detection processing on the image signal captured by the camera 12, and an upper edge (details will be described later) of the measurement object are detected from the synchronously detected image. From the vehicle, based on the upper edge detection unit 15, the lower edge detection unit 16 that detects the lower edge (details will be described later) of the measurement object from the synchronously detected image, and the upper edge detected by the upper edge detection unit 15. The distance to the measurement object A first distance calculation unit 17a to be output; a second distance calculation unit 17b that calculates a distance from the vehicle to the measurement object based on the lower edge detected by the lower edge detection unit 16; a first distance calculation unit 17a; A distance selection unit 18 that selects a distance calculated by any one of the second distance calculation units 17b.

  The light projecting unit 11 is, for example, a headlight including a projector headlight or a reflector, and irradiates area light (pulse light) having a light distribution characteristic that forms a light emitting area extending in the horizontal direction. The area light formed in the horizontal direction is time-modulated and irradiated onto the measurement object, and the luminance boundary between the irradiation area and the non-irradiation area (both upper and lower luminance boundaries) is sharply defined on the measurement object. Realize the light distribution projected on the screen. For example, it has the light distribution characteristic which has the brightness | luminance boundary shown with the code | symbol Y1, Y2 shown in FIG. Further, the light projecting unit 11 emits light of any one of visible light, infrared light, and ultraviolet light, or a combination thereof.

  The camera 12 includes, for example, an image sensor such as a CDD or a CMOS, and captures various images around the vehicle and receives reflected light from the measurement object of the region light emitted from the light projecting unit 11. In addition, the camera 12 has detection sensitivity for light of any one of visible light, infrared light, and ultraviolet light projected from the light projecting unit 11 or a combination thereof.

  The light projecting control unit 13 controls the length of lighting and extinguishing time when the light projecting unit 11 is turned on (PWM modulation control), and outputs a signal indicating the imaging timing to the camera 12 to perform synchronous detection processing. A carrier wave (sin (2πfct)) necessary for extracting pulsed light from an image captured in synchronization with the pulsed light projected from the light projecting unit 11 is output to the unit 14.

  The synchronous detection processing unit 14 uses a plurality of images acquired in time series from the camera 12, and when all the pixels in the image or the processing area is limited in the image, in all the pixels in the processing area, Of the region light emitted from the light projecting unit 11, only the light synchronized with the light pulse is extracted. That is, only the light at the time of on is extracted from the region light that repeatedly turns on (lights on) and off (lights off).

  The upper edge detection unit 15 detects the upper edge of the region light based on the region light extraction image extracted by the synchronous detection processing unit 14. Specifically, as shown in FIG. 5, when the measurement object 31 is irradiated with area light, the edge r <b> 1 serving as a boundary line above the area light on the measurement object 31 is detected as the upper edge. .

  The lower edge detection unit 16 detects the lower edge of the region light based on the region light extraction image extracted by the synchronous detection processing unit 14. Specifically, as shown in FIG. 5, when the measurement object 31 is irradiated with area light, the edge r <b> 2 that is the lower boundary line of the area light on the measurement object 31 is detected as the lower edge. To do. Details of the upper edge and the lower edge will be described later.

  The first distance calculation unit 17 a uses the triangulation principle based on the image of the upper edge detected by the upper edge detection unit 15, and the angle formed by the irradiation direction of the upper edge of the region light and the visual axis of the camera 12. Based on the layout, the distance to the measurement object 31 is calculated as the first measurement distance. Further, the second distance calculation unit 17b uses the triangulation principle based on the image of the lower edge detected by the lower edge detection unit 16, and the irradiation direction of the lower edge of the area light and the visual axis of the camera 12 are determined. Based on the angle formed and the layout, the distance to the measurement object is calculated as the second measurement distance. A detailed calculation procedure will be described later.

  The distance selection unit 18 acquires the first measurement distance calculated by the first distance calculation unit 17a and the second measurement distance calculated by the second distance calculation unit 17b, and changes with time of each measurement distance (for example, The first measurement distance is selected when the measurement object 31 approaches the host vehicle, and the second measurement is performed when the measurement object is separated. Select a distance. By such a selection process, an accurate distance without a time delay can be acquired, and the selected distance is output to a downstream system (not shown).

  Next, the basic principle of synchronous detection in the synchronous detection processing unit 14 will be described with reference to the block diagram shown in FIG. 2 and the timing chart shown in FIG. In general, synchronous detection is used as a process for robustly detecting only the irradiated region light. In the present embodiment, this synchronous detection processing is performed on all the pixels of the image captured by the camera 12 or all the pixels in the image region set as the processing region, and the irradiation light is extracted at each pixel. Here, an example in which BPSK (Binary Phase Shift Keying) is used as the synchronous detection will be described with reference to FIGS.

  As shown in FIG. 2, the transmission signal is a binary signal, and is represented by S (t) (t is time). For example, as shown in FIG. 3A, the binary signal S (t) changes between “1” and “0” at regular time intervals. When transmitting the binary signal S (t), the carrier wave sin (2πfct) having a sufficiently high frequency fc with respect to the binary signal S (t) is phase-modulated with the binary signal S (t), and the BPSK transmission signal is obtained. Generate. As a result, a waveform as shown in FIG. 3B is generated and projected (see symbol q1 in FIG. 2). A sine wave is generally used as the carrier wave, and the transmitted BPSK modulation signal is expressed by the following equation (1).

sin (2πfct + (S (t) −1) × π)
= (2 × S (t) −1) × sin (2πfct) (1)
Accordingly, the transmission signal S (t) changes as shown in FIG. The light projecting unit 11 sends out pulse light whose intensity is modulated with a signal obtained by DC offset of the BPSK modulated signal.

  The transmitted pulsed light is applied to the object to be measured, reflected, and received by the camera 12 (see symbol q2). A carrier wave is superimposed on each pixel of the image captured by the camera 12 (see q3), and a time-series signal as shown in FIG. 3C is obtained. Thereafter, the high-frequency component of the time-series signal is removed by the low-pass filter (LPF), and the time-series signal after the removal of the high-frequency component is subjected to positive / negative sign determination, thereby demodulating as shown in FIG. A transmission signal S (t) is obtained.

  The process of receiving this BPSK modulated signal on the receiving side and demodulating S (t) from this received signal is called synchronous detection, and the contents of the process are described by mathematical expressions as follows.

  First, as shown in the following equation (2), the received signal is multiplied by a carrier wave sin (2πfct).

sin (2πfct + (S (t) −1) π) × sin (2πfct) (2)
Next, from the product-sum formula of the trigonometric function, formula (2) is changed to the following formula (3) (see FIG. 3C).

− (Cos (4πfct + (S (t) −1) π) −cos ((S (t) −1) π)) / 2 (3)
Then, when the high frequency component of the frequency 2fc of the first term in the equation (3) is removed using a low-pass filter (LPF), the second term remains, so that the received signal is expressed by the following equation (4). Will be demodulated.

cos ((S (t) -1) π) / 2 (4)
The sign of this demodulated signal is synchronized with “1” and “0” of S (t), which is the transmission signal, and it can be seen that the transmission signal S (t) can be demodulated by making a positive / negative determination (FIG. 3). (See (d)).

  In the above description, an example in which the carrier wave sin (2πfct) is phase-modulated with the binary signal S (t) has been described. However, other modulation methods such as amplitude modulation and frequency modulation may be used.

  Next, the projection pattern of the area light projected from the light projecting unit 11 will be described with reference to FIGS. As described above, the light projecting unit 11 mounted on the vehicle Q projects the region light that has a bright and dark horizontal pattern at the upper end and lower end of the light projecting region and can be switched on and off. To do. Hereinafter, the light distribution pattern of the region light will be described. FIG. 4 is an explanatory diagram showing a state in which the area light is irradiated toward the measurement target 31 from the light projecting unit 11 mounted on the vehicle Q, and FIG. It is explanatory drawing which shows the image imaged with the camera 12 at the time.

  When measuring distance using the principle of triangulation, when using synchronous detection to ensure the robustness of measurement detection, the technique of irradiating slit-shaped light, which is a well-known technique, is the measurement target. When the relative distance between the object 31 and the object 31 is changed, the irradiation light position in the image is shifted, so that there is a problem that the irradiation light cannot be extracted by synchronous detection.

  In the present embodiment, the relative distance between the vehicle Q and the measurement object 31 is changed by using the region light having the bright and dark pattern light in the horizontal direction as a substitute for the slit-shaped irradiation light. Even in this case, it is possible to continue the extraction of the region light by the synchronous detection. At this time, when the distance is measured using only the upper edge of the region light subjected to the synchronous detection processing, the distance between the vehicle Q and the measurement target 31 is large (the measurement target 31 is relatively far away). The upper edge of the latest region light changes with respect to the upper edge of the synchronous detection region at the start of detection. For this reason, the distance is calculated using the upper edge extracted in the image frame at the start of detection, and the calculated distance causes a problem that a delay corresponding to the synchronous detection processing time occurs. Specifically, as shown in FIG. 7 to be described later, the upper edge extracted from the first frame image in FIG. 5A and the upper edge extracted from the n frame image in FIG. Since the distances are different, the measurement accuracy of the distance may be reduced.

  Therefore, in the present embodiment, the above problem is solved by using the lower edge in addition to the upper edge. As shown in FIG. 4, area light having a pattern in which light and darkness is generated at the upper and lower parts is projected toward the periphery of the vehicle Q from the light projecting unit 11, and the measurement object 31 is irradiated with the area light. The

  Then, the camera 12 receives the region light reflected by the measurement object 31, thereby obtaining an image in which the upper edge r1 and the lower edge r2 are copied as shown in FIG. In the present embodiment, the distance measurement based on the upper edge r1 and the distance measurement based on the lower edge r2 are performed, and the distance is measured by either distance measurement according to the distance change between the measurement object 31 and the vehicle Q. By selecting a different distance, it is possible to prevent a time delay of the measurement distance.

  Next, the principle of calculating the distance to the measurement object 31 using the upper edge and the lower edge of the area light will be described with reference to the schematic diagram shown in FIG. As shown in FIG. 6, the camera 12 is arranged at a position offset in a direction (vertical direction) perpendicular to the spreading direction (horizontal direction) of the region light irradiated from the light projecting unit 11. The area light projected from the light projecting unit 11 is irradiated onto the measurement object 31, and the camera 12 images the area light reflected on the surface of the measurement object 31.

  Here, the upper end portion of the region light projected from the light projecting unit 11 is the horizontal (up and down angle 0 °) direction, the lower end portion is the direction of the downward angle θ, the distance Dy upward from the light projecting unit 11, and the rear The camera 12 is installed at a position offset by the distance Dz, and the measurement object 31 is imaged with the camera 12 directed toward the downward angle α. The angle β in the direction in which the top edge irradiated to the measurement object 31 can be seen and the angle γ in which the bottom edge can be seen become measurement values, and the distance Z to the measurement object 31 is expressed by the following equations (5) and (6) respectively. It can be calculated independently.

Z = Dy / tan (α + β) (5)
Z = (Dy + Dz · tan θ) / (tan (α + γ) −tan θ) (6)
That is, when the upper edge r1 shown in FIG. 5 is used, the distance Z (first measurement distance) can be calculated by the equation (5), and when the upper edge r2 is used, the equation (6) is used. A distance Z (second measurement distance) can be calculated.

  The vertical angle θ of the area light can be calculated based on the time required for the synchronous detection process, the minimum value of the detection distance, and the maximum value of the relative speed, and the vertical angle of the area light is set to be equal to or greater than the predetermined angle. As a result, the synchronous detection region can be continuously measured. The vertical angle θ of the area light is, for example, a required angle of 3 ° or more when the processing time is 0.25 seconds, the minimum detection distance is 2 m, and the maximum measurement value of the relative speed is 30 km / h.

  Next, even when the relative distance between the vehicle Q and the measurement object 31 changes, the principle that the distance between the two can be accurately measured without causing a time delay will be described with reference to FIGS. To do.

  FIG. 7 is an explanatory diagram showing an image obtained by synchronously detecting an image acquired by the camera 12 when the distance between the vehicle Q and the measurement object 31 is long. FIG. The image of the first frame is shown, and FIG. 5B shows the image after the number of frames (n) necessary for the synchronous detection processing.

  A region where region light can be extracted continuously from the n images from FIG. 7A to FIG. 7B is inside the region R1 shown in FIG. 7B. The upper end of this region R1 is the same height as the upper end of the first frame in FIG. 7A, and when the distance is measured from the upper end of the synchronous detection region, the distance at the start of the synchronous detection process is calculated. It will be. That is, since the upper edge extracted from the image of the nth frame is r3 (upper outside of the region R1) shown in 7 (b), it is originally desired to measure the distance based on this upper edge r3. However, since the distance is actually measured using the upper end of the region R1 as the upper edge, the distance at the start of synchronous detection is calculated. On the other hand, the lower end coincides with the lower end of the region light of the nth frame in FIG. 7B, and the distance calculated from the lower end of the synchronous detection region is the distance in the latest image.

  Therefore, when the measurement object 31 moves away from the vehicle Q, it is advantageous to improve the measurement accuracy by measuring the distance between the two using the lower edge of the region R1.

  FIG. 8 is an explanatory diagram showing an image obtained by synchronously detecting an image acquired by the camera 12 when the distance between the vehicle Q and the measurement object 31 is short. FIG. An image of the first frame at the start is shown, and FIG. 7B shows an image after the number of frames (n) necessary for the synchronous detection processing. A region where region light can be extracted continuously from the n images from FIG. 8A to FIG. 8B is within the region indicated by R2 in FIG. 8B. The lower end of this region R2 is the same height as the lower end of the first frame in FIG. 8A, and when the distance is measured from the lower end of the synchronous detection region, the distance at the start of the synchronous detection process is calculated. It becomes. That is, the lower edge extracted from the image of the nth frame is r4 (lower outside of the region R2) shown in FIG. 8B, and it is originally desired to measure the distance based on this lower edge r4. However, since the distance is actually measured using the lower end of the region R2 as the lower edge, the distance at the start of synchronous detection is calculated. On the other hand, the upper end coincides with the upper end of the region light of the nth frame in FIG. 8B, and the distance calculated from the upper end of the synchronous detection region is the distance in the latest image.

  Therefore, when the measurement object 31 approaches the vehicle Q, it is advantageous to improve the measurement accuracy by measuring the distance between the two using the upper edge of the region R2. In the present embodiment, distance measurement using the upper edge (first measurement distance) and distance using the lower edge depending on whether the distance between the measurement object 31 and the vehicle Q is relatively long or short. By selecting one of the measurements (second measurement distance), highly accurate distance measurement is realized.

  Next, the operation of the distance measuring apparatus according to the first embodiment will be described with reference to the flowchart shown in FIG. First, in step S1, an image of the measurement object 31 existing around the vehicle is acquired by the camera 12.

  In step S2, a synchronous detection process flow is executed. Thereafter, the process proceeds to step S3. The synchronous detection process flow will be described later with reference to the flowchart shown in FIG.

  In step S3, the upper edge detecting unit 15 extracts the upper edge from the synchronously detected image, and the lower edge detecting unit 16 extracts the lower edge from the synchronously detected image.

  In step S4, the first distance calculation unit 17a is a distance from the vehicle Q to the measurement object 31 using the principle of triangulation based on the upper edge (the distance Z calculated by the above-described equation (5)). Is calculated as a first measurement distance D1), and the second distance calculation unit 17b uses the triangulation principle based on the lower edge to determine the distance from the vehicle Q to the measurement object 31 (the above-described equation (6)). This is a calculated distance Z, which is referred to as a second measurement distance D2.

  In step S5, it is determined whether or not the second measurement distance D2 is larger than the first measurement distance D1, and if larger, the process proceeds to step S6, and if not, the process proceeds to step S7.

  In step S6, the amount of change of the first measurement distance D1 and the second measurement distance D2 from the previous measurement value is detected. If the amount of change of the first measurement distance D1 is 0 or more (positive value), the second measurement distance D2 It is determined whether or not the amount of change is smaller. That is, it is determined whether or not “dD2 / dt> dD1 / dt ≧ 0”, and when the change amount of the first measurement distance D1 is a positive value and smaller than the change amount of the second measurement distance D2. (YES in step S6), the process proceeds to step S8. On the other hand, when the change amount of the first measurement distance D1 is 0 or less (negative value) and smaller than the change amount of the second measurement distance D2 (NO in step S6), the process proceeds to step S7.

  In step S7, the first measurement distance D1 is selected. That is, if NO is determined in step S5 (D1 ≧ D2), the first measurement distance D1 obtained from the upper edge is more likely to be a more accurate distance, so that the calculation load is reduced. In step S6, the first measurement distance D1 (measurement distance based on the upper edge) is selected. Furthermore, when it is determined NO in step S6, that is, the time change of the first measurement distance D1 is a negative value (that is, the distance tends to decrease), and the time change of the second measurement distance D2 Is smaller, the measurement object 31 is determined to be approaching the vehicle Q, and the first measurement distance D1 is selected.

  On the other hand, in step S8, the second measurement distance D2 is selected. That is, when the time change of the first measurement distance D1 is a positive value (that is, the distance tends to increase) and is smaller than the time change of the second measurement distance D2, the measurement object 31 is a vehicle. The second measurement distance D2 (measurement distance based on the lower edge) is selected as determined to be separated from Q. Then, the selected measurement distance (first measurement distance D1 or second measurement distance D2) is output to the subsequent system. Then, when the above process is finished, this process is finished.

  Next, the synchronous detection process executed in the process of step S2 of FIG. 9 will be described with reference to the flowchart shown in FIG.

  First, synchronous detection processing is started in step S11, and in step S12, a carrier wave sin (2πfct) defined by the light projection control unit 13 for the acquired image (image captured by the camera 12) (FIG. 2) is mixed. Specifically, all pixels set in the processing area in the image are multiplied by a sine wave in a phase corresponding to the acquisition timing.

  In step S13, an image obtained by mixing the carrier wave sin (2πfct) is stored in a frame memory (not shown) included in the synchronous detection processing unit 14. When performing continuous detection processing, if n consecutive frames of images are required, a frame memory for n frames is secured. For example, the oldest image data is updated with the latest image data by a ring buffer structure. To do.

  In step S14, time-series data of pixel data at a predetermined address is read from the image data stored in the frame memory. For example, assuming that the pixel data of the pixel position (xi, yj) acquired at the latest time t is I (xi, yj, t), the data for the latest n pixels used for synchronous detection, I (xi, yj, t ), I (xi, yj, t−1),..., I (xi, yj, t−n + 1).

  In step S15, a low-pass filter (see LPF in FIG. 2) is applied.

  In step S16, the positive / negative judgment of the transmission signal is performed on the time-series data of the pixels to which the low-pass filter is applied. For example, “1” is assigned if the pixel value is a positive value, and “0” is assigned if the pixel value is a negative value, and the transmitted signal sequence (bit sequence) is restored.

  In step S17, it is determined whether or not the detection has been completed for all the pixels in the processing region. If the detection processing has not been completed for all the pixels in the processing region (NO in step S17), the process proceeds to step S14. The processing is returned, the time-series pixel data at the next pixel position (for example, (xi + 1, yj)) is read, and the processing from step S15 is repeated.

  If the detection process has been completed for all the pixels (YES in step S17), the synchronous detection image is output in step S18 and the process ends. In this way, the distance between the vehicle Q and the measurement object 31 can be obtained based on the upper edge detected by the upper edge detection unit 15.

  Thus, in the distance measuring device 100 according to the first embodiment, the light projecting unit 11 projects area light having a light emission pattern having a light emitting area extending in the horizontal direction, and the camera 12 measures the measurement object. The area light reflected at 31 is imaged. Further, the upper edge and the lower edge are extracted from the image of the measurement object 31 captured when the light emission pattern is on by synchronously detecting the captured area light. Then, the distance between the vehicle Q and the measurement object 31 is calculated as the first measurement distance D1 based on the extracted upper edge, and the distance between the vehicle Q and the measurement object 31 is calculated based on the lower edge. 2 Calculated as the measurement distance D2.

  Furthermore, the temporal changes of the first measurement distance D1 and the second measurement distance D2 are calculated, and one of the first measurement distance D1 and the second measurement distance D2 is selected based on the calculation result. Therefore, even when the distance between the vehicle Q and the measurement object 31 changes, the distance between them can be measured with high accuracy.

  Further, when the second measurement distance D2 is larger than the first measurement distance D1, based on the time change (dD1 / dt) of the first measurement distance D1 and the time change (dD2 / dt) of the second measurement distance D2. Since one of the first measurement distance D1 and the second measurement distance D2 is selected, a more accurate measurement distance can be selected by a relatively simple method.

  Further, when the time change (dD1 / dt) of the first measurement distance D1 is a negative value and smaller than the time change (dD2 / dt) of the second measurement distance D2, the vehicle Q and the measurement object 31 Therefore, the first measurement distance D1 is selected, the time change of the first measurement distance D1 (dD1 / dt) is a positive value, and the time change of the second measurement distance D2 (dD2 / If the distance is smaller than dt), the distance between the vehicle Q and the measurement object 31 tends to increase, so the second measurement distance D2 is selected. Therefore, it is possible to select an appropriate measurement distance (D1 or D2) corresponding to a change in the distance between the vehicle Q and the measurement object 31, and obtain the distance to the measurement object 31.

  Further, the irradiation light by the light projecting unit 11 and the imaging timing by the camera 12 are controlled by the light projecting control unit (control means) 13 and are synchronized by the carrier wave (sin (2πfct)) generated by the light projecting control unit 13. Irradiation light is extracted by performing synchronous detection by the detection processing unit 14. Since this synchronous detection process uses at least one of phase modulation, amplitude modulation, and frequency modulation, it is possible to avoid interference when distance measurement is simultaneously performed by a plurality of devices, and detection robustness can be avoided. Improvements can be made.

  Furthermore, since the light source of the light projecting unit 11 emits infrared rays or ultraviolet rays, it is possible to detect the irradiation light more robustly by providing the camera 12 with a filter that transmits light of a specific spectrum with high efficiency. It becomes. In addition, it is possible to prevent dazzling without disturbing the visual recognition of others by irradiation with pulsed light.

  Next, it will be described that the resolution can be improved by setting the visual axis of the camera 12 to have a predetermined depression angle with respect to the direction in which the upper edge is irradiated.

  In order to observe a wide area with one camera 12, a wide-angle lens is usually used. A general wide-angle lens employs an equidistant projection lens (so-called fθ lens) as a projection method, and the peripheral visual field has a lower resolution than the central visual field. In combination with such a wide-angle lens, it is important that the camera viewing axis has a depression angle (or elevation angle) and an area with high resolution is set appropriately for the area to be monitored.

  Hereinafter, for the sake of simplicity in the combination with the fθ lens, it is assumed that the upper edge of the irradiated light is horizontal with respect to the road surface, and the distance measurement value to the object to be observed when there is a depression angle of the camera visual axis. The improvement in the resolution will be described with reference to FIGS. FIG. 11 shows a case where there is no depression angle on the camera visual axis, and FIG. 12 shows a case where there is a depression angle.

  11 and 12, the pixel position in the visual axis direction is y (j), and the pixel position adjacent to y (j) is y (j + 1). At this time, as shown in FIG. 11, when the depression angle (elevation angle) is 0 degree, the angular resolution of one pixel determined by the pixel positions y (j) and y (j + 1) is the distance resolution at the real space distance. Let dD (0). On the other hand, as shown in FIG. 12, when the depression angle (elevation angle) is α degrees, the angular resolution of one pixel determined by the pixel positions y (j) and y (j + 1) is the distance resolution dD at the real space distance. Assume that (α). In this case, since dD (α) <dD (0) is established, when the depression angle (elevation angle) is given to the camera visual axis, the real space resolution with respect to the angular resolution of one pixel is increased. That is, by providing the depression angle α, it is possible to increase the real spatial resolution when extracting the upper edge.

  As described above, the upper edge of the region light projected by the light projecting unit 11 is formed in a region lateral to the camera 12, and the camera 12 is offset in a direction perpendicular to the upper edge irradiation direction. Measurement accuracy when distance is measured based on the principle of triangulation even when a general wide-angle lens (fisheye lens) is used, as long as the top edge irradiation direction and the visual axis form a predetermined angle. Will improve.

[Description of Second Embodiment]
Next, a second embodiment will be described. FIG. 13 is a block diagram showing a configuration of a distance measuring apparatus according to the second embodiment of the present invention. As shown in FIG. 13, the distance measuring device 101 includes two light projecting units, that is, an upper light projecting unit (first light projecting unit) 20 and a lower light projecting unit, in contrast to the first embodiment described above. The difference is that a (second light projecting unit) 21 is provided, and a π phase shifter 22 that displaces the phase of the light pattern of the region light projected from the lower light projecting unit 21 by π [rad]. Since the other configuration is the same as that of FIG. 1 described above, the same reference numerals are given and description of the configuration is omitted.

  In the distance measuring apparatus 101 according to the second embodiment, two light projecting units (upper light projecting unit 20 and lower light projecting unit 21) having different irradiation angles in the vertical direction are installed, and the respective light projecting units 20 and 21 are installed. Uses a light source having bright and dark edges only at the upper end. Then, the modulation signal supplied to the lower light projecting unit 21 is set to an opposite phase to the modulation signal of the upper light projecting unit 20 using the π phase shifter 22.

  As shown in FIG. 14, when area light is projected toward the measurement target 31 from the upper light projecting unit 20 and the lower light projecting unit 21, an image as illustrated in FIG. 15 is captured by the camera 12. . As shown in FIG. 15, pulse light is projected onto the area indicated by P <b> 1 by the upper stage light projecting unit 20, and pulse light is projected onto the area indicated by P <b> 2 by the lower stage light projecting part 21.

  A portion where the regions P1 and P2 overlap (that is, the region P2) is a region where the modulation signal is canceled by the opposite phase, and thus is not a synchronous detection detection region detected by the synchronous detection processing unit 14. Therefore, on the image of the measurement object 31, there are an upper edge r <b> 11 due to the region light projected from the upper light projecting unit 20 and an upper edge r <b> 12 due to the region light projected from the lower light projecting unit 21. It will be. If the upper end edges r11, r12 are the upper end edge and the lower end edge (r1, r2 shown in FIG. 5) shown in the first embodiment, the two upper end edges r11, r12 are used to When the distance between Q and the measuring object 31 changes, highly accurate distance measurement is possible.

  FIG. 16 is a timing chart showing changes in the modulation signal and the synchronous detection signal by the distance measuring apparatus 101 according to the second embodiment. FIG. 16A shows the transmission signal S (t), which is indicated by bit signals “0” and “1”. (B) shows the modulation signal of the region light projected from the upper light projecting unit 20, and (c) shows the modulation signal of the region light projected from the lower light projection unit 21. 16B and 16C, the region light projected from the upper light projecting unit 20 and the region light projected from the lower light projecting unit 21 have opposite phases (phase difference π [rad]). It is understood that

  FIG. 16D shows the luminance change of the region light of the upper light projecting unit 20 by the modulation signal shown in FIG. 16B, and the region light detected in the region projected only by the upper light projecting unit 20. Changes in brightness. FIG. 16E shows the luminance change in a region (region P2 in FIG. 15) where the region light projected from the upper light projecting unit 20 and the region light projected from the lower light projecting unit 21 are mixed. Show. It is understood that almost no change in luminance occurs in this region.

  That is, in the region where the change in luminance shown in 16 (d) is detected, the transmission signal is demodulated by synchronous detection processing as shown in FIG. 16 (f), and “0” as shown in FIG. “1” signal can be acquired, but synchronous detection cannot be performed in the region shown in FIG.

  Thus, in the distance measuring apparatus 101 according to the second embodiment, the upper light projecting unit 20 and the lower light projecting unit 21 having a horizontal luminance edge are provided at the upper end, and the upper and lower light projecting units 20 and 21 are arranged above and below. Area light is irradiated with the overhead angle varied by a predetermined angle, and time modulation of area light projected from the upper light projecting unit 20 and time modulation of area light projected from the lower light projecting unit 21 are mutually performed. The phase is reversed. Then, by using the upper edge extracted from the area light projected from the upper light projecting unit 20 and the upper edge extracted from the area light projected from the lower light projecting unit 21, the first embodiment described above is used. The same effect as the form can be obtained.

  As a result, as in the first embodiment described above, even if the distance between the vehicle Q and the measurement object 31 changes, one of the two upper edges is selected and the distance is selected. By calculating | requiring, the distance between both can be measured with high precision.

  In addition, it is possible to use visible light, infrared light, etc. as a wavelength of the light projected from a light projection part, In that case, the camera 12 used the element which can observe the wavelength to project. It should be.

  The distance measuring device of the present invention has been described based on the illustrated embodiment. However, the present invention is not limited to this, and the configuration of each part is replaced with an arbitrary configuration having the same function. Can do.

  The present invention can be used to measure the distance between a vehicle and a measurement object with high accuracy.

DESCRIPTION OF SYMBOLS 11 Light projection part 12 Camera 13 Light projection control part 14 Synchronous detection process part 15 Upper end edge detection part 16 Lower end edge detection part 17a 1st distance calculation part 17b 2nd distance calculation part 18 Distance selection part 20 Upper stage light projection part 21 Lower stage light projection Optical unit 22 π phase shifter 31 Measuring object 100, 101 Distance measuring device

Claims (7)

Light projection that is mounted on a movable body and has a light emitting region that extends in the horizontal direction around the movable body, and that emits time-modulated pulsed light that has a linear end with the upper end and the lower end being horizontal. Means,
An imaging unit that is mounted on the moving body and images the pulsed light that is projected by the light projecting unit and reflected by the object;
Detection means for extracting the pulsed light from the image captured by the imaging means;
Control means for controlling light projection by the light projection means, imaging by the imaging means, and detection by the detection means;
Edge detection means for detecting an edge of the pulsed light detected by the detection means;
Distance calculating means for calculating a distance between the object based on the image position of the edge detected by the edge detecting means;
The edge detection means includes an upper edge detection unit that detects an upper edge of the pulsed light, and a lower edge detection unit that detects a lower edge.
The distance calculation means is detected by a first distance calculation unit that calculates a distance to the object as a first measurement distance based on the upper edge detected by the upper edge detection unit, and the lower edge detection unit. A second distance calculation unit that calculates a distance to the object as a second measurement distance based on the lower edge of
Further, the time change of the first measurement distance and the time change of the second measurement distance are calculated, respectively, and based on the comparison result of the calculation result and the magnitude of the first measurement distance and the second measurement distance, A distance selecting means for selecting one of the first measurement distance and the second measurement distance;
A distance measuring device comprising: The distance selecting means is
The magnitudes of the first measurement distance and the second measurement distance are compared, and when the second measurement distance is larger than the first measurement distance, the time change of the first measurement distance and the second measurement distance The distance measuring device according to claim 1, wherein either one of the first measurement distance and the second measurement distance is selected based on a calculation result of time change. The distance selecting means is
When the time change of the first measurement distance is a negative value and smaller than the time change of the second measurement distance, the first measurement distance is selected,
3. The second measurement distance is selected when the time change of the first measurement distance is a positive value and smaller than the time change of the second measurement distance. The distance measuring device according to claim.   The control unit and the detection unit control the light projecting unit and the imaging unit using at least one of amplitude modulation, phase modulation, and frequency modulation as the time modulation. The distance measuring device according to any one of claims 1 to 3.   The light projecting means has a light source that emits at least one of visible light, infrared light, and ultraviolet light, and the imaging means has a visible light region, an infrared region, and The distance measuring device according to claim 1, wherein the distance measuring device has sensitivity in at least one of the ultraviolet regions.   The distance measuring apparatus according to claim 1, wherein the imaging unit is provided in a vertical direction with respect to the light projecting unit, and a shooting direction has a predetermined depression angle. The light projecting means has a light emitting region in the horizontal direction, and a first light projecting unit that projects pulsed light having a linear end with the upper end being horizontal, and
A second light projecting unit configured to project pulsed light having a linear end portion having a light emitting area in the horizontal direction and a horizontal upper end portion, the depression angle being set larger than that of the first light projecting unit; Including,
The pulsed light projected from the first light projecting unit and the pulsed light projected from the second light projecting unit have opposite phases,
The upper edge detection means detects the edge of the upper edge that is projected from the first light projecting section and extracted by the detection means as an upper edge,
The said lower end edge detection means detects the edge of the upper end part projected by the said 2nd light projection part, and is extracted by the said detection means as a lower end edge. The distance measuring device according to item 1.