JP5211938B2 - Irradiation light extraction apparatus and method - Google Patents

Description

  The present invention relates to an irradiation light extraction apparatus and method for projecting irradiation light onto an object and extracting the irradiation light reflected by the object.

  2. Description of the Related Art Conventionally, there has been known a technique for measuring the distance to an object by capturing the light applied to the object with a camera and extracting the irradiation light from the captured image. In such a distance measurement technique, Japanese Patent Application Laid-Open No. 2004-228867 discloses a technique for extracting only irradiation light for distance measurement irradiated on an object even when the object is illuminated by background light such as illumination. It has been.

In this Patent Document 1, irradiation light is extracted by performing frequency filtering and amplitude change pattern filtering on an analog value of an electrical signal obtained from received irradiation light.
"Correlation Image Sensor" IEEE Trans. Electron Device, vol.50, no.10 pp.2059-2066, 2003

  In the technique for extracting irradiation light described above, filtering is performed with reference to an analog value, and therefore it is difficult to measure the illuminance change of irradiation light with high accuracy due to the influence of nonlinear characteristics in the analog circuit. In particular, when the object is placed in a high illuminance environment such as sunlight, most of the illuminance values that appear as analog values are illuminance values due to sunlight, and the ratio of irradiation light is small. Therefore, there is a possibility that the illuminance change due to the influence of the non-linear characteristic of the analog circuit is greatly obtained and the irradiation light is reflected on the object with high accuracy.

  Then, this invention is proposed in view of the situation mentioned above, and it aims at providing the irradiation light extraction apparatus and method which can extract the irradiation light reflected by the target object accurately.

  In the present invention, irradiation light is projected from a projector to a predetermined irradiation range by controlling the irradiation time for each sampling time, which is a predetermined unit time, according to an illuminance pattern that changes the irradiation time at a predetermined frequency. Then, the irradiation light projected from the projector and reflected from the object is accumulated as an electrical signal for each sampling time, and expressed by the irradiation time for each sampling time from the electrical signal for each sampling time accumulated in the accumulating means. The above-described problem is solved by extracting the intensity of the irradiated light.

  According to the present invention, the irradiation time of the irradiation light is adjusted for each sampling time, and the intensity of the irradiation light is extracted from the electric signal received and accumulated by receiving the reflected light. Light irradiation can be performed digitally according to the ratio with the irradiation time, and the irradiation light can be extracted from the electrical signal accumulated during the sampling time. Therefore, according to the present invention, it is possible to eliminate the non-linear characteristic in the light irradiation and the non-linear characteristic when measuring the irradiation intensity, and it is possible to accurately extract the irradiation light reflected by the object.

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

[Configuration of irradiation light extraction device]
The present invention is applied to an irradiation light extraction apparatus configured as shown in FIGS. This irradiation light extraction device is mounted on a vehicle and displays distance information of other vehicles existing in front of the vehicle to the driver of the vehicle. This irradiation light extraction device includes a projector 10 provided in the front part of the vehicle, a camera 20 provided in the upper part of the vehicle interior, an arithmetic unit 30 provided in the instrument panel of the vehicle, and the width direction of the instrument panel. And a display 40 provided at a position near the center and visible to the driver. In the irradiation light extraction apparatus shown in FIG. 1, the camera 20 and the arithmetic unit 30 are configured by computer hardware including a CPU, a ROM, a RAM, etc., but in FIG. The explanation is given separately.

  The projector 10 projects pulse-shaped irradiation light that has been frequency-modulated into a predetermined irradiation range in front of the vehicle. The projector 10 is supplied with a control signal from the irradiation control unit 34 in the arithmetic unit 30. The projector 10 projects the pulsed irradiation light by switching the illuminance of the irradiation light between 100% and 0% according to the control signal.

  The camera 20 receives irradiation light reflected from a preceding vehicle that is a measurement object. When a preceding vehicle exists, the irradiation light projected by the projector 10 is irradiated to the preceding vehicle. Therefore, the light received by the camera 20 includes irradiation light reflected by the preceding vehicle in addition to disturbance light such as sunlight and fluorescent lamps. The camera 20 generates an image signal with brightness according to the illuminance of the received light. This image signal is a time-series electrical signal.

  The camera 20 includes a photodetector 21, an integrator 22, and a digital sampling unit 23. The photodetector 21 converts the received light into an image signal. The integrator 22 accumulates the image signal converted by the light detector 21. This accumulated image signal consists of pixel values corresponding to illuminance. The digital sampling unit 23 converts the image signal stored in the integrator 22 into image data that is a digital signal. This image data is supplied from the digital sampling unit 23 in the camera 20 to the arithmetic unit 30.

  The arithmetic unit 30 controls the projector 10 and calculates the distance from the preceding vehicle based on time-series image data supplied from the camera 20. The arithmetic unit 30 includes a multiplier 31, a digital filter unit 32, a distance measurement unit 33, an irradiation control unit 34, a modulation unit 35, and a correction table storage unit 36.

  The multiplier 31 multiplies the image data supplied from the digital sampling unit 23 and the modulation signal supplied from the modulation unit 35. Image data obtained as a result of this multiplication is supplied to the digital filter section 32. The digital filter unit 32 performs digital filter processing for extracting only the modulation frequency component of the irradiation light for each pixel of the image data. The digital filter unit 32 becomes image data composed of the irradiation light component reflected by the preceding vehicle.

  The distance measuring unit 33 is supplied with image data consisting only of the irradiated light component that has been filtered by the digital filter unit 32. The distance measuring unit 33 performs geometric calculation from the position of each pixel of the image data, the mounting angle of the camera 20, the angle of the light emitted from the projector 10, and the arrangement of the projector 10 and the camera 20, to the preceding vehicle. The distance is calculated. The distance measuring unit 33 outputs the distance information of the preceding vehicle to the display 40.

  The display 40 displays the distance information of the preceding vehicle supplied from the arithmetic unit 30. In the irradiation light extraction device, not only the distance information of the preceding vehicle is displayed on the display 40, but the distance information may be presented by another instrument or may be presented by voice.

  The modulation unit 35 supplies a modulation signal to the multiplier 31 and the irradiation control unit 34. This modulation signal represents an illuminance pattern that changes the irradiation time at a predetermined frequency.

  The irradiation controller 34 controls the projector 10 according to the modulation signal supplied from the modulator 35. The irradiation control unit 34 outputs to the projector 10 a control signal that lengthens the irradiation time for each sampling time as the illuminance in the illuminance pattern increases.

  The correction table storage unit 36 stores a correction table representing nonlinear characteristics that the digital sampling unit 23 converts from an image signal to a digital signal. The correction table stored in the correction table storage unit 36 is read by the irradiation control unit 34. Then, the irradiation control unit 34 refers to the correction table and controls the irradiation time of the projector 10 so as to cancel the nonlinearity of the pixel value of the image data supplied from the digital sampling unit 23.

  Further, the correction table storage unit 36 may store a correction table representing sensitivity characteristics for detecting the irradiation light by the light detector 21. The correction table stored in the correction table storage unit 36 is read by the irradiation control unit 34. Then, the irradiation control unit 34 refers to the correction table, and sets the irradiation time of the projector 10 so as to cancel out the non-linearity due to the sensitivity characteristic of the photodetector 21 according to the image data output from the digital sampling unit 23. Control.

[Operation of irradiation light extraction device]
In the irradiation light extraction apparatus configured as described above, a specific operation will be described with reference to FIGS.

  In the irradiation light extraction device, the modulation signal output from the modulation unit 35 is a sine wave as shown in FIG. With respect to such a modulation signal, the irradiation controller 34 controls the projector 10 so as to have an irradiation time of a sampling time corresponding to the illuminance, as shown in FIG. Accordingly, the projector 10 increases the irradiation time in the sampling time as the modulation signal increases, and the irradiation time over the entire sampling time at the maximum value of the modulation signal, and the entire sampling time at the minimum value of the modulation signal. It will turn off. Here, the irradiation time at each sampling time is corrected by the correction table stored in the correction table storage unit 36.

  As shown in FIG. 3C, the camera 20 accumulates light every predetermined sampling time and generates image data. When there is a preceding vehicle, the image data becomes a discrete value proportional to the irradiation time for each sampling time as shown in FIG. The image data includes the same frequency component as the modulation signal generated by the modulation unit 35.

  Thus, the irradiation light extraction device can eliminate the influence of the nonlinear characteristics of the projector 10 when adjusting the irradiation intensity with the illuminance by controlling the irradiation intensity in the projector 10 on and off on the time axis. Further, even when the irradiation light reflected by the preceding vehicle is detected, the intensity of the light irradiated from the projector 10 can be restored according to the accumulation time of the irradiation light.

  Therefore, according to this irradiation light extraction device, the nonlinear characteristic of the projector 10 when irradiating the irradiation light of the projector 10 can be eliminated, and the nonlinear characteristic of the photodetector 21 when measuring the irradiation intensity can be eliminated. Can be eliminated. Thereby, the irradiation light extraction device can accurately measure the illuminance of the irradiation light reflected by the preceding vehicle.

The arithmetic unit 30 irradiates the irradiation light reflected by the preceding vehicle out of the irradiation light that is frequency-modulated by the irradiation control unit 34 and the modulation unit 35 from the image data as a digital signal from the digital sampling unit 23 of the camera 20. Extract light. Here, as shown in FIG.
sin (ω ₂ t + β) (Formula 1)
The modulation signal expressed by Equation 1 is generated by the modulation unit 35. Here, in sin (ω ₂ t + β), ω ₂ is a value corresponding to the modulation frequency, and β is an arbitrary phase.

Then, the irradiation control unit 34 controls the irradiation time of the light projector 10 for each modulated signal _{(sin (ω 2 t + β} )) such that the illuminance in accordance with the sampling time. In the modulated irradiation light, a component (reflected light) reflected by the preceding vehicle is detected by the camera 20. A digital signal (observed digital data) obtained by detecting reflected light with the camera 20 is represented by sin (ω ₁ t + α). Here, in sin (ω ₁ t + α), ω ₁ is a modulation frequency, and α is an arbitrary phase.

This digital signal includes sin (ω ₁ t + α) representing the irradiation light component emitted from the projector 10, a direct current component DC such as sunlight, and a periodic alternating current component G · sin (ω ₂ t + γ such as a fluorescent lamp. ) And
G · sin (ω ₁ t + α) + DC + G · sin (ω ₂ t + γ) (Formula 2)
It is expressed. Here, the phase α in the above expression 2 representing the digital signal is a phase change amount with respect to the phase β in the irradiation light irradiated from the projector 10. Further, G in the above formula is an attenuation amount.

Then, the modulation signal of the above equation 1 and the digital signal representing the reflected irradiation light of the above equation 2 are multiplied by the multiplier 31,
G · {cos (β−α) / 2−cos (2ωt + α + β) / 2}
+ DC · sin (ω ₁ t + β)
+ Cos ((ω ₁ −ω ₂ ) t + β−α) / 2
−cos ((ω ₁ + ω ₂ ) t + α + β) / 2 (Formula 3)
This is the signal expressed by the above equation 3. The signal of Expression 3 is subjected to low-pass filter processing by the digital filter unit 32. As a result, the signal obtained as a result of the low-pass filter processing is time-variant is removed from the signal of Equation 3,
G · cos (β−α) / 2 (Formula 4)
It becomes. According to Equation 4, only a digital signal including the same frequency component as the modulation frequency ω ₁ is observed as a DC component, and a DC component such as sunlight or an AC component different from the modulation frequency such as a fluorescent lamp is removed and becomes zero. ing. That is, the digital signal obtained by the camera 20 is multiplied by the same modulation frequency as the irradiation light projected from the projector 10, and only the irradiation light component included in the digital signal is extracted by performing a low-pass filter process. be able to.

  Next, with reference to FIG. 5, a procedure for calculating and presenting the distance to the preceding vehicle by the irradiation light extraction apparatus to which the present invention is applied will be described.

  In a situation where the ignition switch of the vehicle is turned on, in step S1, the modulation unit 35 generates a sinusoidal modulation signal. This modulation signal represents the illuminance pattern of the projector 10 as described above.

  In the next step S2, the irradiation control unit 34 converts the modulation signal generated in step S1 into irradiation time of irradiation light for every predetermined sampling time. That is, the irradiation control unit 34 increases the irradiation time during which the illuminance is 100% during the sampling time as the amplitude of the modulation signal is higher. Here, the irradiation control unit 34 may adjust the irradiation time for each sampling time with respect to the modulation signal according to the correction table stored in the correction table storage unit 36.

  In the next step S3, the irradiation controller 34 causes the projector 10 to output irradiation light so as to control the irradiation time for each sampling time. Accordingly, the irradiation light extraction device outputs pulsed irradiation light from the projector 10 to a predetermined irradiation range.

  In step S4, the light detector 21 of the camera 20 receives the light including the irradiation light reflected by the preceding vehicle and performs photoelectric conversion.

  In the next step S5, the integrator 22 accumulates the electrical signal generated in step S4 for a predetermined sampling time.

  In the next step S <b> 6, the digital sampling unit 23 A / D converts the image signal that is the electrical signal accumulated in step S <b> 5 into image data that is a digital signal, and outputs the image data to the arithmetic unit 30.

  In step S <b> 7, the multiplier 31 of the arithmetic unit 30 multiplies the image data that is the digital signal output in step S <b> 6 and the modulation signal generated by the modulation unit 35. As a result, a signal as expressed by Equation 3 is obtained, and the signal is supplied from the multiplier 31 to the digital filter unit 32.

  In the next step S8, the digital filter unit 32 performs a filtering process on the signal supplied from the multiplier 31 in step S7, removes the AC component included in the image data, and emits irradiation light that is a DC component. Extract.

  In the next step S9, the distance measuring unit 33 analyzes the image data including only the DC component obtained in step S8, and obtains the distance from the preceding vehicle. Here, the distance measurement unit 33 performs a triangulation calculation based on a geometric relationship such as the mounting position of the projector 10 and the camera 20 and the pixel position, and obtains the distance from the preceding vehicle.

  In the next step S10, the display 40 displays the distance from the preceding vehicle calculated by the distance measuring unit 33 of the calculation unit 30 in step S9.

[Effect of the embodiment]
As described above in detail, according to the irradiation light extraction device to which the present invention is applied, the irradiation time of the irradiation light for each sampling time is controlled to emit the irradiation light from the projector 10, and the electricity accumulated every sampling time is stored. Since the intensity of the irradiation light expressed by the irradiation time for each sampling time is extracted from the signal, the light irradiation of the projector 10 is performed digitally by the ratio of the irradiation time for each sampling time and the non-irradiation time. Irradiation light can be extracted from the electrical signal accumulated during the sampling time. Therefore, according to this irradiation light extraction device, the nonlinear characteristic of the light detector 21 when measuring the nonlinear characteristic and irradiation intensity of the projector 10 can be eliminated, and the irradiation light reflected by the preceding vehicle can be accurately extracted. can do.

  Moreover, according to this irradiation light extraction device, since the irradiation light component is extracted by the digital filter unit 32 from the digital signal generated by the digital sampling unit 23, even when there are a plurality of photodetectors 21. A plurality of digital signals generated by a plurality of digital sampling units 23 corresponding to the respective photodetectors 21 can be sequentially processed. Thereby, according to this irradiation light extraction apparatus, a number of parts can be reduced and size reduction and cost reduction are realizable.

  Furthermore, according to the irradiation light extraction apparatus to which the present invention is applied, a process for converting the stored electrical signal into a digital signal, a process for multiplying the digital signal by the illuminance pattern, and a digital filter for deleting the high frequency component of the multiplied digital signal By performing the processing, the irradiation light can be extracted, and the irradiation light can be extracted with high accuracy regardless of the non-linear characteristics of the analog processing.

  Furthermore, according to this irradiation light extraction device, a table representing nonlinear characteristics that the digital sampling unit 23 converts from an electrical signal to a digital signal is stored, and the nonlinearity of the digital sampling unit 23 is referenced with reference to the table. Since the irradiation time of the projector 10 is controlled so as to cancel out, even if there is a deviation in the characteristic of converting to a digital signal according to the value of the electrical signal obtained as a result of accumulation, the irradiation from the projector 10 is performed so as to reduce the deviation. The illuminance of the irradiated light can be controlled. Therefore, according to this irradiation light extraction device, irradiation light can be extracted with higher accuracy.

  Furthermore, according to the irradiation light extraction device, a table representing sensitivity characteristics for detecting the irradiation light is stored, and the sensitivity is referred to according to the digital signal output from the digital sampling unit 23 with reference to the table. Since the irradiation time of the projector 10 is controlled so as to cancel out the non-linearity due to the characteristics, even if the sensitivity of the photodetector 21 is low due to the intensity of the received irradiation light, the projector is designed to reduce the sensitivity fluctuation. It is possible to control the illuminance of irradiation light emitted from 10. Therefore, according to this irradiation light extraction device, irradiation light can be extracted with higher accuracy.

  Furthermore, according to the irradiation light extraction device, the preceding vehicle is determined based on the intensity of the irradiation light obtained by the multiplication process of the digital signal converted from the accumulated electrical signal and the modulation signal and the digital filter process of removing the high frequency component. Thus, the distance to the preceding vehicle can be obtained with high accuracy.

  The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and various modifications can be made depending on the design and the like as long as the technical idea according to the present invention is not deviated from this embodiment. Of course, it is possible to change.

  That is, in the description of the irradiation light extraction device described above, the target object has been described as a preceding vehicle. However, the present invention is not limited to this, and the distance to an obstacle existing in the rear or rear side may be obtained. Of course.

It is a block diagram which shows the structure of the irradiation light extraction apparatus to which this invention is applied. It is a perspective view which shows the attachment state of a projector, a camera, and an arithmetic unit. It is a time chart which shows operation | movement of the irradiation light extraction apparatus to which this invention is applied. It is a figure explaining the digital processing in the irradiation light extraction apparatus to which this invention is applied. It is a flowchart which shows the operation | movement procedure of the irradiation light extraction apparatus to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light projector 20 Camera 21 Optical detector 22 Integrator 23 Digital sampling part 30 Arithmetic unit 31 Multiplier 32 Digital filter part 33 Distance measurement part 34 Irradiation control part 35 Modulation part 36 Correction table memory | storage part 40 Display

Claims (6)

A projector for projecting irradiation light within a predetermined irradiation range;
Irradiation control means for controlling the irradiation time of the projector for each sampling time that is a predetermined unit time according to an illuminance pattern that changes the irradiation time at a predetermined frequency;
Accumulating means for accumulating irradiation light projected from the projector and reflected from the object as an electrical signal for each sampling time;
Irradiation light extraction means, comprising: irradiation light extraction means for extracting the intensity of irradiation light represented by the irradiation time for each sampling time from the electrical signal for each sampling time stored in the storage means.   The irradiation light extraction unit includes a sampling unit that converts an electrical signal stored in the storage unit into a digital signal, a multiplication unit that multiplies the illuminance pattern by the digital signal sampled by the sampling unit, and the multiplication unit The irradiation light extraction device according to claim 1, comprising: a digital filter unit that deletes a high-frequency component of the digital signal calculated in step 1. The sampling unit comprises storage means for storing a table representing non-linear characteristics for conversion from an electric signal to a digital signal,
The said irradiation control means controls the irradiation time of the said projector so that the nonlinearity of the said sampling part may be offset with reference to the table memorize | stored in the said memory | storage means. 4. Irradiation light extraction apparatus as described in. Storage means for storing a table representing sensitivity characteristics for detecting irradiation light;
The illumination control unit refers to a table stored in the storage unit, and controls the irradiation time of the projector so as to cancel out the nonlinearity due to the sensitivity characteristic. 4. Irradiation light extraction apparatus as described in.   5. The apparatus according to claim 1, further comprising a distance calculation unit that calculates a distance to the object based on an intensity of the irradiation light extracted by the irradiation light extraction unit. Irradiation light extraction device. According to an illuminance pattern that changes the irradiation time at a predetermined frequency, the irradiation time for each sampling time that is a predetermined unit time is controlled, and the irradiation light is projected from the projector to a predetermined irradiation range,
The irradiation light projected from the projector and reflected from the object is accumulated as an electrical signal for each sampling time,
The irradiation light extraction method characterized by extracting the intensity of the irradiation light represented by the irradiation time for each sampling time from the electrical signal for each sampling time stored in the storage means.

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