JP6019621B2 - Distance measuring device - Google Patents

Description

  The present invention relates to a distance measuring apparatus that irradiates an object with intensity-modulated irradiation light and measures the distance to the object.

  An optical system that irradiates an object with irradiation light, images the reflected light of the irradiation light with an image sensor such as a CCD, and measures the distance to the object or the shape of the object based on the acquired image data. A distance measuring apparatus is known. In such a distance measuring device, if the reflected light of the irradiated light is weaker than the background light, the reflected light may be buried in the background light noise and the object may not be recognized correctly.

  Therefore, distance measurement is made possible by making the wavelength and blinking period different for the remote transmitter / receiver unit where the reflected light is weaker than the conventional one and the near transmitter / receiver unit where the reflected light is sufficiently strong. An apparatus has been proposed (see, for example, Patent Document 1).

JP 2010-107448 A

  However, when measuring the distance using a transmission signal intensity-modulated with a sine wave or the like in order to enhance robustness against noise, the amount of background light is the upper end of the linear observation region in the luminance sensitivity characteristic of the image sensor, or When observing reflected light in which a transmission signal is superimposed near the lower end, this reflected light may enter a non-linear region of the image sensor.

  In such a case, the upper end (upper peak area of the sine wave) or lower end (lower peak area of the sine wave) of the intensity-modulated signal acquired from the image captured by the imaging means is saturated. Thus, an error occurs in the synchronous detection judgment when performing the synchronous detection process on the transmission signal, and the intensity modulation signal is not detected even though there is sufficient reflection information, and the distance to the target object There was a problem that the accuracy of measurement and shape measurement was lowered.

  The present invention has been made in order to solve such a conventional problem, and an object of the present invention is to provide an intensity-modulated signal acquired from a captured image in a non-linear region of luminance sensitivity characteristics of an imaging unit. It is to provide a distance measuring device capable of measuring the distance and shape to an object with high accuracy even when detected by the above.

In order to achieve the above object, the present invention provides a light projecting unit that irradiates intensity-modulated irradiation light, an image capturing unit that captures an object irradiated with the irradiation light, and an image captured by the image capturing unit. And synchronous detection processing means for extracting a region where the luminance fluctuates in synchronization with the intensity modulation of light emission by the light projecting means as a synchronous detection region. Then, the synchronous detection means, when the luminance output values of the image captured by the imaging means brightness sensitivity characteristic of the image pickup means is detected by the non-linear region, the luminance output value luminance sensitivity characteristic of the imaging means linear Correction is performed using the luminance output value detected in the region.

  In the distance measuring device according to the present invention, when measuring the distance to the object using the intensity-modulated irradiation light, even when the luminance output value of the nonlinear region of the imaging means is partially observed, the irradiation light Thus, stable distance measurement or shape measurement can be carried out without mistaken synchronous detection measurement.

It is a block diagram which shows the structure of the distance measuring device which concerns on one Embodiment of this invention. It is a block diagram which shows the detailed structure of the synchronous detection process part of the distance measuring device which concerns on one Embodiment of this invention. It is explanatory drawing which shows the process sequence in the synchronous detection process part of the distance measuring device which concerns on one Embodiment of this invention. It is a timing chart which shows change of each signal in a synchronous detection processing part of a distance measuring device concerning one embodiment of the present invention. It is explanatory drawing which shows a mode that the distance to an observation target object is measured with the distance measuring device which concerns on one Embodiment of this invention. It is explanatory drawing which shows the image imaged with the camera of the distance measuring device which concerns on one Embodiment of this invention. It is explanatory drawing which shows the principle which measures the distance to an observation target object with the distance measuring device which concerns on one Embodiment of this invention. It is a characteristic view which shows a response | compatibility with an input light intensity and a luminance output value of the image pick-up element used for the distance measuring device which concerns on one Embodiment of this invention. It is explanatory drawing which shows a mode that a distortion arises in the upper end part of the luminance output signal of an image pick-up element with respect to the intensity | strength-modulated signal. It is explanatory drawing which shows a mode that a distortion arises in the lower end part of the luminance output signal of an image pick-up element with respect to the intensity | strength-modulated signal. It is explanatory drawing which shows the correction amount at the time of correct | amending the luminance output signal which the distortion produced. It is a flowchart which shows the process sequence of the distance measuring device which concerns on one Embodiment of this invention. It is a flowchart which shows the detailed process sequence of the synchronous detection process shown in FIG. It is explanatory drawing which shows distance resolution in case the depression angle of the camera by the distance measuring device which concerns on one Embodiment of this invention is 0 degree. It is explanatory drawing which shows distance resolution in the case of the depression angle (alpha) degree of the camera by the distance measuring device which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a distance measuring apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, the distance measuring device 100 is mounted on a vehicle (moving body), and projects light that irradiates irradiation light toward an observation target P that is a target of distance measurement around the vehicle. A unit (light projecting unit) 11, a camera (imaging unit) 12 that captures an image of the observation object P irradiated with the irradiation light, and a light projection control unit 14 that controls irradiation of the irradiation light by the light projecting unit 11. A synchronous detection processing unit (synchronous detection processing means) 13 for performing synchronous detection processing on the image signal captured by the camera 12, and an upper edge detection unit for detecting the upper edge of the observation object P from the synchronously detected image. 15 and a distance calculation unit 16 that calculates the distance from the vehicle to the observation object P based on the edge detected by the upper edge detection unit 15.

  In the present embodiment, the case where the moving body is a vehicle will be described as an example. However, the present invention is not limited to this, and the present invention is also applicable to other moving bodies such as a railway vehicle and a ship. Is possible. Further, the distance measuring apparatus 100 according to the present embodiment can be configured using, for example, an integrated computer including a central processing unit (CPU) and storage means such as RAM, ROM, and hard disk.

  The light projecting unit 11 is, for example, a headlight including a projector headlight or a reflector, and irradiates the observation target P with irradiation light having a light distribution characteristic that forms a light emitting region in the horizontal direction. Then, by irradiating the observation target P with irradiation light, the luminance boundary between the irradiation region and the non-irradiation region can be clearly projected on the observation target P. Further, as the light source of the light projecting unit 11, a light source of visible light, infrared light, or ultraviolet light can be used.

  The camera 12 includes an image pickup device such as a CCD or a CMOS, picks up an image around the vehicle, and in addition to this, the reflected light reflected by the observation target P is irradiated light emitted from the light projecting unit 11. Is received.

  The light projecting control unit 14 outputs a trigger signal for pulse lighting and extinguishing timing when the irradiation light emitted from the light projecting unit 11 is PWM-controlled, and outputs a trigger signal for imaging timing by the camera 12 and a control signal for shutter time. Output. In addition, a carrier wave (carrier frequency) signal used in PWM control is output to the synchronous detection processing unit 13.

  The synchronous detection processing unit 13 sequentially stores images captured in time series by the camera 12, and all the pixels in the stored image (or in the case where the processing region is limited in the image, In all the pixels), the modulated signal included in the irradiation light output from the light projection control unit 14 is synchronously detected to output an irradiation light extraction image in which only pixels whose luminance changes in synchronization with the irradiation light intensity are extracted. . Then, the irradiation light extraction image is output to the upper edge detection unit 15. The detailed configuration of the synchronous detection processing unit 13 will be described later with reference to the block diagram shown in FIG.

  The upper edge detection unit 15 detects the position of the upper edge portion of the irradiation light from the irradiation light extracted image extracted by the synchronous detection processing unit 13, and the vertical position information in the image (the upper end of the irradiation light shown in FIG. 6). Position information in the vertical direction of the edge r1) is output.

  The distance calculation unit 16 uses the vertical position information of the upper edge output from the upper edge detection unit 15, based on the irradiation direction of the irradiation light upper edge, the angle formed by the visual axis of the camera 12, and the layout. Based on the principle, the distance to the surrounding object irradiated with the irradiation light is calculated. The calculation procedure will be described later with reference to FIG.

  FIG. 2 is a block diagram showing a detailed configuration of the synchronous detection processing unit 13. As illustrated, the synchronous detection processing unit 13 includes an image memory 21, an offset correction calculation unit 22, a DC component removal processing unit 23, a waveform multiplication unit 24, and a synchronous detection determination unit 25.

  The image memory 21 stores the number of images captured by the camera 12 by the number corresponding to the modulation period of the light projection control.

  The offset correction calculation unit 22 performs a process of correcting the DC offset component of the corresponding pixel in the image stored in the image memory 21 according to the presence state of the luminance output value of the nonlinear region of the image sensor. Also, as shown in FIG. 11 described later, when distortion occurs at the upper end or lower end of the luminance output value in the image, processing for correcting this distortion is performed.

  The DC component removal processing unit 23 performs a process of removing the DC offset component after offset correction from the image stored in the image memory 21.

  The waveform multiplication unit 24 multiplies the modulation signal for light projection control for each pixel of the image from which the DC component has been removed by the DC component removal processing unit 23.

  The synchronous detection determination unit 25 performs synchronization determination with the light modulation signal by determining whether the signal multiplied by the modulation signal by the waveform multiplication unit 24 is positive or negative.

  Next, a basic principle of general synchronous detection in the synchronous detection processing unit 13 will be described with reference to a schematic diagram shown in FIG. 3 and a timing chart shown in FIG. In the distance measuring apparatus 100 according to the present embodiment, the irradiation light is emitted from the light projecting unit 11 toward the observation target P, and the reflected light reflected by the observation target P is detected. It is detected separately from other lights. At this time, synchronous detection processing is used as processing for robustly detecting only irradiated irradiation 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. Hereinafter, a detailed description will be given with reference to FIGS.

  The transmission signal S (t) (t is time) shown in FIG. 3 is a binary signal that changes to “1” or “0” at a constant time interval, as shown in FIG. When transmitting the transmission signal S (t), a carrier wave sin (ωt) having a sufficiently high frequency ω with respect to the transmission signal S (t) is phase-modulated with the transmission signal S (t), and BPSK (Binary (Phase Shift Keying) Generates a transmission signal. Specifically, when S (t) = 1, the switching unit 31 is switched upward to output the carrier wave sin (ωt) as it is, and when S (t) = 0, the switching unit 31 is moved down. The waveform of the carrier wave sin (ωt) shifted in phase by π (180 degrees) is output.

  As a result, a signal having a phase-modulated waveform as shown in FIG. 4B (when S (t) = 0, the phase is shifted by 180 degrees) is generated. Is irradiated toward the observation object P (see symbol q1 in FIG. 3). That is, the modulation signal transmitted from the light projecting unit 11 is represented by “2 × (S (t) −0.5) × sin (ωt)”.

  On the other hand, the irradiation light irradiated to the observation target P is reflected by the observation target P (see symbol q2 in FIG. 3) and is captured by the camera 12. Then, the DC component is removed from the modulation signal included in the image, and the multiplication unit multiplies the carrier wave sin (ωt). When the modulated signal is multiplied by the carrier wave sin (ωt), the following equation (1) is obtained.

A × (S (t) −0.5) × sin (ωt) × sin (ωt)
= A × (S (t) −0.5) × (1-cos (2ωt)) / 2 (1)
A is a constant including the influence of reflection.
From the equation (1), the output signal of the multiplication unit is a signal in which the signal components of the sum of frequencies (DC component) and the difference (double harmonic component) are mixed. That is, as shown in FIG. 4 (c), a waveform whose frequency is doubled and amplitude is positive when S (t) = 1, and is negative when S (t) = 0. Is obtained.

  After that, smoothing is performed by removing high frequency components using an LPF (low-pass filter), and further, a positive / negative determination is made, and as shown in FIG. The binary signal S (t) can be taken out. In the above description, an example in which a BPSK transmission signal is used as a detection signal has been described. However, other amplitude modulation, phase modulation, frequency modulation, or a combination thereof can be used.

  The synchronous detection processing unit 13 shown in FIG. 2 stores an image captured by the camera 12 in the image memory 21 based on the principle shown in FIGS. A process of correcting the DC offset component of the corresponding pixel in accordance with the presence state of the luminance output value of the non-linear region of the camera 12 in the image stored in 21 and a process of correcting distortion of the luminance output value Do.

  Further, the DC component removal processing unit 23 performs a process of removing the DC offset component after the offset correction from the image stored in the image memory 21. After that, the waveform multiplication unit 24 multiplies the modulation signal for light projection control for each pixel of the image from which the direct DC component has been removed. Further, the synchronous detection determination unit 25 determines the synchronization with the light modulation signal by determining whether the signal multiplied by the modulation signal is positive or negative.

  Next, a light projection pattern of irradiation light (light having a light emitting region in the horizontal direction) projected from the light projecting unit 11 will be described. As described above, the light projecting unit 11 mounted on the vehicle irradiates the upper end portion of the light projecting area with the irradiation light having a bright and dark horizontal pattern. Hereinafter, this light distribution pattern will be described with reference to FIGS. FIG. 5 is an explanatory diagram showing a state in which irradiation light is irradiated toward the observation target P from the light projecting unit 11 mounted on the vehicle Q, and FIG. 6 irradiates the observation target P with the irradiation light. It is a figure which shows the image imaged with the camera 12 at the time.

  Even if the relative positional relationship between the vehicle Q and the observation target P changes due to the change in the attitude of the vehicle Q or the movement of the observation target P, the region is stably displayed. In order to extract light, irradiation light needs to be continuously observed at the same location on the observation target P in a time-series image frame necessary for detection.

  Actually, since there is no restriction on the movement of the vehicle and the observation object P, even when the vehicle Q and the observation object P move arbitrarily, it is sufficient to realize stable extraction of irradiation light. It is necessary to set the extraction area of the irradiation light. Therefore, in the present embodiment, as shown in FIG. 6, irradiation light having a light emitting region that spreads in the horizontal direction (long in the horizontal direction) is used.

  Next, the principle of measuring the distance to the observation object P using the upper edge of the region light will be described with reference to the schematic diagram shown in FIG. As shown in FIG. 7, 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 observation object P, and the camera 12 images the area light reflected on the surface of the observation object P. Here, based on the irradiation angle (0 degree in the example of FIG. 7) of the area light upper end of the light projecting unit 11, the distance (height difference) Dy between the light projecting unit 11 and the camera 12, and the depression angle α of the camera 12 is observed. Depending on the distance Z to the object P, the vertical direction β at which the upper end of the region light is observed changes. Therefore, the distance Z to the observation object P can be calculated based on the principle of triangulation using the vertical position y at the upper end of the irradiation area observed by the camera 12.

  Next, the reason why non-detection errors occur in distance measurement using intensity-modulated irradiation light will be described with reference to FIGS.

  FIG. 8 is a diagram showing luminance sensitivity characteristics of the image sensor, and shows the relationship between the light intensity (horizontal axis) incident on the image sensor of the camera 12 and the luminance output value (vertical axis). The observation target P is irradiated with background light such as sunlight in addition to the irradiation light irradiated from the light projecting unit 11, and an image captured by the camera 12 according to the DC component intensity of the background light. The incident light intensity changes.

  When the DC component of the background light is large (in the case of the background light N1) and the reflected light (A1) of the irradiation light whose intensity is modulated is superimposed on the background light, the incident light intensity ( Since the brightness of the image captured by the camera 12 increases, detection is performed in the nonlinear region P1 of the image sensor mounted on the camera 12, and the brightness output value detected by the camera 12 is the waveform (B1). Such a signal waveform causes distortion at the upper end.

  On the other hand, when the DC component of the background light is small (in the case of the background light N2) and the reflected light (A2) of the irradiation light whose intensity is modulated is superimposed on the background light, the incident light intensity is small. Therefore, the detection is performed in the nonlinear region P2 of the image sensor, and the luminance output value detected by the camera 12 is a signal waveform in which distortion is generated at the lower end as in the waveform (B2) as described above.

  FIG. 9 is a characteristic diagram showing a time-series luminance change of a pixel in which a signal with a distorted upper end is observed. A region C shown in FIG. 9 shows a sample point group that is detected by saturation due to the nonlinear characteristic of the camera 12. In the state where the received waveform is distorted, the DC offset component (= A / 2; see the above formula (1)) cannot be obtained accurately, and if the synchronous detection calculation is performed, An error occurs in the restoration of the binary signal S (t) by the positive / negative determination. That is, since the nonlinear regions P1 and P2 shown in FIG. 8 exist, the luminance output value is distorted with respect to the intensity of incident light imaged by the camera 12 (because the region C in FIG. 9 exists). Thus, accurate synchronous detection processing cannot be performed.

  FIG. 10 is a characteristic diagram showing a time-series luminance change of a pixel in which a signal with a distorted lower end is observed, and the region C is also detected as being saturated. Then, as in FIG. 9 described above, this region C makes it impossible to perform accurate synchronous detection processing.

  In the present embodiment, by correcting signal distortion in the nonlinear regions P1 and P2 of the image sensor of the camera 12 by the following method, highly accurate synchronous detection processing is executed to improve distance measurement accuracy.

  Hereinafter, a method for correcting the signal distortion in the nonlinear region will be described. In the present embodiment, when the output value of the nonlinear region is observed in the sample point group included in the intensity modulation signal detected by the camera 12, and the number of sample points is less than or equal to half the number of sample points in the modulation period. In addition, using the sample point group detected in the linear region of the image sensor of the camera 12 (sample point group detected in the region D in FIG. 9), the luminance output value of the sample point in the region C in FIG. The insufficient overshoot amount is calculated to correct the luminance output value at each sample point. Then, by performing the synchronous detection process using the correction waveform acquired by the correction and the carrier wave, the synchronous detection process can be continuously executed without being undetected (without being disabled in synchronous detection). become.

  Hereinafter, the process of correcting the luminance output value of the sample point will be described with reference to FIG. As shown in FIG. 11, the modulation signal is G1, the luminance output is G2, and the luminance output values for the modulation signal output values (amplitude values of the BPSK signal) b1, b2, and b3 are a1, a2, and a3, respectively. Further, a1 and a2 are luminance output values in the linear region, a3 is a luminance output value in the non-linear region, and a correction value (overshoot) of the luminance output is Δa. Then, the following equation (2) is established.

(A2-a1) / (b2-b1) = {(a3 + Δa) -a2} / (b3-b2)
... (2)
Then, when the formula (2) is modified, the following formula (3) is obtained.

(A3 + Δa) = {(a2-a1). (B3-b2) / (b2-b1)} + a2
... (3)
Therefore, “a3 + Δa” can be obtained by the above equation (3), and the luminance output value detected in the nonlinear region of the image sensor can be corrected by the equation (3). That is, the luminance output values indicated by the symbols B1 and B2 in FIG. 8 can be corrected to a waveform without distortion. This process is calculated by the offset correction calculation unit 22 shown in FIG.

  In the above description, the example of correcting the waveform with the upper end distorted (in the case of FIG. 9) has been described. However, the same correction can be made when the lower end is distorted (in the case of FIG. 10).

  Next, the processing procedure of the distance measuring apparatus according to this embodiment will be described with reference to the flowcharts shown in FIGS.

  First, in step S1, an image is acquired from the camera 12 and stored in the image memory 21 (see FIG. 2). In step S2, it is determined whether or not the number of frames required for synchronous detection is stored in the image memory 21, and if the number of images required for synchronous detection is not stored, the process returns to step S1 to synchronize. If the number of images necessary for detection is stored, the process proceeds to step S3.

  In step S3, a synchronous detection process to be described later is executed. Thereafter, the process proceeds to step S4. In step S4, the upper edge of the synchronously detected area is extracted, and the process proceeds to step S5.

  In step S5, a distance measurement process by triangulation is performed based on the data of the upper edge detected in the process of step S4. That is, the distance to the observation object P is measured based on the method shown in FIG. Thereafter, the process proceeds to step S6.

  In step S6, the distance value obtained in step S5 is output to the lower system. Thereafter, this process is terminated. Thus, the distance from the attachment position of the camera 12 to the observation object P can be measured.

  Next, the procedure of the synchronous detection process shown in step S3 will be described with reference to the flowchart shown in FIG.

  First, synchronous detection processing is started in step S11. In step S12, the time-series image data of the number required for synchronous detection is acquired from the image stored in the image memory 21. Thereafter, the process proceeds to step S13.

  In step S13, it is determined whether or not there is a luminance output value corresponding to the nonlinear region of the image sensor in the time-series data in pixel units. If it is determined that the luminance output value exists, the process proceeds to step S14, and it is determined that it does not exist. If so, the process proceeds to step S16.

  In step S14, it is determined whether or not the luminance output corresponding to the nonlinear region is less than half (50% or less) within the modulation period. Specifically, it is determined whether or not the number of sample points shown in region C of FIG. 9 is less than or equal to half of the total number of sample points (for one period). If it is determined that the number is less than half (YES in step S14), the amplitude is corrected based on the luminance output value of the linear region in step S15. Specifically, Δa, which is the amount of overshoot, is calculated using the method shown in FIG. 11, and the amplitude of the luminance output value is corrected. Thereafter, the process proceeds to step S16.

  In step S16, an average process is performed on a pixel basis, and the DC offset component is removed by dividing the average value of each pixel from each time series data. Thereafter, the process proceeds to step S17. In step S17, the offset-adjusted time series data is multiplied by the carrier wave. Thereafter, the process proceeds to step S18.

  In step S18, it is determined whether the positive / negative determination result of the result after multiplication and the transmission signal S (t) are synchronized. If they are synchronized, the process proceeds to step S19, and the pixel is set to a synchronous color (as an example). White: Overwrite with “255” in the case of 8-bit gradation. On the other hand, if not synchronized, the process proceeds to step S20, and the pixel is overwritten with an asynchronous color (for example, black: “0” in the case of 8-bit gradation). Thereafter, the process proceeds to step S22.

  If it is determined in step S14 that the number of luminance outputs in the non-linear area is larger than half of the whole, in step S21, it is determined that synchronization determination is impossible (for example, in the case of gray: 8-bit gradation, “ 127 ") and output. That is, when the number of luminance outputs in the non-linear region is larger than half of the whole, correction using the data in the linear region is difficult, and in this case, it is determined that synchronous detection cannot be performed. Thereafter, the process proceeds to step S22.

  In step S22, it is determined whether or not the determination has been completed for all the pixels. If the determination has not been completed, the process returns to step S12, and the synchronous detection determination is performed for the pixels that have not been completed. On the other hand, if all the pixels have been determined, the process proceeds to step S23 to output a synchronous detection image. Thereafter, this process is terminated.

  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 of the resolution will be described with reference to FIGS. FIG. 14 shows a case where there is no depression angle on the camera visual axis, and FIG. 15 shows a case where there is a depression angle.

  14 and 15, 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. 14, 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 in the real space distance. Let dD (0). On the other hand, as shown in FIG. 15, 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.

  Thus, in the distance measuring device according to the present embodiment, the irradiation light whose intensity is modulated at a predetermined modulation frequency is irradiated from the light projecting unit 11 toward the detection target region (the region including the observation target P). Further, the reflected light reflected from the detection target region is captured by the camera 12, and the captured images are stored and stored in the image memory 21 in time series. Then, synchronous detection processing is performed based on image data captured in time series, and luminance information of pixels synchronized with the irradiation light is extracted. At this time, the waveform of the luminance signal detected in the nonlinear region of the image sensor mounted on the camera 12 may be distorted.

  That is, the upper end portion (upper peak value) or lower end portion (lower peak value) of the image pickup signal output from the image pickup device of the camera 12 is the upper end of the linear region of the luminance sensitivity characteristic of the image pickup device within the modulation period of the irradiation light. 8 or more (region P1 in FIG. 8) or below the lower end (region P2 in FIG. 8). In such a case, the luminance signal waveform is distorted, and the accuracy of synchronous detection is reduced. To do. In the present embodiment, by correcting the luminance information of the non-linear region using the luminance change of the linear region portion, high-precision synchronization is performed in the synchronous detection process even in a situation where distortion occurs in a part of the imaging signal from the camera 12. Detection can be performed, and stable distance measurement and shape measurement can be performed.

  In addition, when the observation time of the nonlinear region is less than half of the modulation period of irradiation light (in other words, when the observation time of the linear region is more than half of the modulation period of irradiation light), the output value of the nonlinear region Since the correction is performed, stable irradiation light extraction can be performed without generating an erroneous determination in the synchronization determination. In addition, when the observation time of the nonlinear region is not less than half of the modulation period of the irradiation light, the determination is not performed and the display is performed in a color that cannot be determined as illustrated in step S21 in FIG. Can be surely recognized by the user.

  Further, the upper end edge of the irradiation light emitted from the light projecting unit 11 is formed in a region in the lateral direction with respect to the camera 12, and the camera 12 is arranged offset in a direction perpendicular to the upper end edge irradiation direction. At the same time, since the upper edge irradiation direction and the visual axis of the camera 12 form a predetermined angle, even when a general wide-angle lens (fisheye lens) is used, the measurement accuracy when measuring the distance based on the principle of triangulation is improved. .

  Further, if the light source provided in the light projecting unit 11 emits infrared light or ultraviolet light, the camera 12 is provided with a filter that transmits light of a specific spectrum with high efficiency. It becomes possible to detect more robustly.

  Further, amplitude modulation, phase modulation, and frequency modulation can be used as a synchronization signal used in the light projecting unit 11 and the synchronous detection processing unit 13, and BPSK that is a combination of amplitude modulation and phase modulation is used. Thus, it is possible to improve robustness.

  Next, a modification of the above-described embodiment will be described. As a simple method, the DC offset component (= A / 2) obtained by the average processing of the observed luminance output value is calculated according to the ratio of the output value of the nonlinear region existing in the luminance output value. The same effect can be obtained by correcting.

  For example, when it is detected that the output value of the non-linear region in the high luminance region exists in N [%] in the modulation period, the offset amount increased by N / 2 [%] (= (1 + N / 200) × By correcting to A / 2), stable distance measurement can be performed without causing an error in the synchronous detection processing. Here, by performing correction in a state where N [%] is 50% or less, erroneous synchronization can be prevented.

  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 unit is replaced with an arbitrary configuration having the same function. Can do.

  The present invention can be used for highly accurate distance measurement by correcting the luminance output value in the nonlinear region of the image sensor.

DESCRIPTION OF SYMBOLS 11 Light projection part 12 Camera 13 Synchronous detection process part 14 Light projection control part 15 Upper end edge detection part 16 Distance calculation part 21 Image memory 22 Offset correction calculation part 23 DC component removal process part 24 Waveform multiplication part 25 Synchronous detection determination part 31 Switching Part 100 Distance measuring device P Observation target

Claims (6)

A light projecting means mounted on a moving body and radiating irradiation light having a light emitting region in the horizontal direction and intensity-modulated;
Imaging means mounted on the moving body and imaging the object irradiated with the irradiation light;
A light projection control means for controlling the light emission intensity of the irradiation light emitted from the light projection means in accordance with the timing of the image pickup by the image pickup means;
Synchronous detection processing means for extracting, as a synchronous detection area, a region whose luminance fluctuates in synchronization with the intensity modulation of the emitted light from the image captured by the imaging means,
Edge detection means for detecting an edge of the synchronous detection region;
Distance calculating means for calculating a distance to the object based on the edge portion detected by the edge portion detecting means;
It said synchronous detection means, the luminance output values of the image captured by the imaging means, when the luminance sensitivity characteristic of the image pickup means is detected by the non-linear region, the luminance sensitivity characteristic of the imaging means the luminance output value Is corrected using a luminance output value detected in a linear region.
  The synchronous detection processing unit corrects the output value of the nonlinear region when the output value of the linear region of the imaging unit is observed in half or more of the modulation period of the irradiation light irradiated from the light projecting unit. The distance measuring device according to claim 1, wherein:   3. The synchronous detection processing unit corrects a DC offset component according to a ratio of a time during which the luminance value of the nonlinear region is output to a whole modulation period. The distance measuring device described in 1.   The light projecting unit and the imaging unit use one of amplitude modulation, phase modulation, and frequency modulation, or a combination thereof, as intensity modulation of irradiation light. The distance measuring device according to any one of the above.   The light projecting unit includes a light source that irradiates at least one of visible light, infrared light, and ultraviolet light, and the image capturing unit has a visible light region according to the light source included in the light projecting unit. The distance measuring device according to claim 1, wherein the distance measuring device has sensitivity in the infrared region and the ultraviolet region.   The said imaging means is provided in the perpendicular direction with respect to the direction where the upper end edge of the said light projection means is irradiated, and has a predetermined depression angle, The any one of Claims 1-5 characterized by the above-mentioned. The distance measuring device according to item.