JP2013083510A - Laser radar device and imaging target selection device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: when clutter of high luminance exists on the background, a clutter component cannot be removed from an image signal.SOLUTION: The laser radar device includes: a laser beam transmission part 11; a receiving part 12; an imaging part 13 having a plurality of imaging elements; a ranging unit 14 that calculates a relative distance to a target and outputs a reception timing signal; a timing generation part 15 that supplies a fist exposure timing signal overlapping a receiving period of the reception timing signal and a second exposure timing signal having a timing that does not overlap the receiving period, to the imaging part 13; and an image processing part 16 for generating image data in which pixels and luminance of the pixels are associated with each other, from the image signal captured by the exposure timing signals. The image processing part 16 generates an image including a target and background by use of the first exposure timing signal, generates an image including the background by use of the second exposure timing signal, and determines a difference in luminance between the images.

Description

  One embodiment relates to a laser radar device and an imaging target selection method using the laser radar device.

  2. Description of the Related Art Conventionally, a target acquisition and tracking device using a laser radar device that emits a laser beam such as infrared rays and performs image detection and distance measurement using reflected light from an object is known (see, for example, Patent Documents 1 and 2).

  The laser radar device irradiates the target with laser light, and performs processing for setting the arrival direction of the reflected light as a tracking point required by the laser radar device (see, for example, Patent Document 3). The tracking point indicates the position of the target object in the input image of the current frame. The laser radar device has a mechanism for driving the infrared camera vertically and horizontally so as to capture the tracking point at the center of the screen imaged by itself. When the reflected light is supplemented by the infrared camera, this mechanism directs the infrared camera in the direction of arrival of the reflected light. The infrared camera captures the target in the center of the field of view. The visual field captured by the infrared camera includes a background image. When an object with high brightness exists in the background, it may be difficult for the image processing unit to distinguish between reflected light and clutter. The clutter refers to the received light intensity of an unnecessary component by an object with high background brightness.

  Conventionally, in order to reduce clutter, a method of acquiring distance information to the background and controlling the exposure timing of the imaging apparatus based on the background distance information has been proposed (for example, see Patent Document 4). Exposure refers to imaging by an imaging device or photosensitivity. In the determination of the exposure timing, the timing for receiving the reflected light is obtained from the distance data with the separately measured target, and the exposure timing is adjusted to this timing.

JP 2011-17645 A JP 2004-28602 A JP 2005-265288 A JP-A-11-183620

  However, in the related art, when a clutter having a very high luminance exists in the background, the clutter component cannot be removed from the image signal in the image area.

  In order to solve such a problem, according to one embodiment, a transmitter that emits laser light, a receiver that receives reflected light reflected by an object from the transmitter, and the receiver An imaging unit having a plurality of imaging elements that receive the reflected light from the unit, and a relative distance between the imaging unit and the target at the time when the imaging unit captures an image, A range finder that outputs a reception timing signal having a waveform that rises and then falls after a reception period, and has a period that overlaps the reception period of the reception timing signal from the range finder and that receives the reflected light A timing generator that provides the imaging unit with a first exposure timing signal at a timing that matches the timing, and a second exposure timing signal that does not overlap the reception period; An image processing unit that generates image data in which a plurality of pixels and the luminance of each pixel are associated with each other from an image signal captured and output by the imaging unit according to each exposure timing signal generated by the imming generation unit, and this image processing The unit generates an image including the target and the background based on the first exposure timing signal, generates an image including the background based on the second exposure timing signal, and obtains the luminance difference between these images. A laser radar device is provided.

  According to another embodiment, after the laser beam is emitted, the target and the first exposure timing signal having a timing that matches a reception timing at which the reflected light reflected by the target to be imaged is expected to return. An image including a background is generated, an image signal including the background is generated by a second exposure timing signal having a timing that does not match the reception timing, and a luminance difference is obtained for each of a plurality of pixels between the images. An imaging target selection method using a laser radar device is provided, wherein the target is selected.

It is a block diagram of the laser radar apparatus which concerns on embodiment. It is a figure for demonstrating the ranging method by the rangefinder used for the laser radar apparatus which concerns on embodiment. It is a time chart which shows the relationship between the transmission-and-reception timing of the laser beam by the laser radar apparatus which concerns on embodiment, and exposure timing. It is a flowchart for demonstrating the imaging target selection method by the laser radar apparatus which concerns on embodiment. It is a figure which shows an example of the difference calculation of the brightness | luminance between the images by the laser radar apparatus which concerns on embodiment.

  Hereinafter, a laser radar device according to an embodiment and an imaging target selection method using the laser radar device will be described with reference to FIGS. 1 to 5. In the drawings, the same portions are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a configuration diagram of a laser radar apparatus according to an embodiment. The laser radar apparatus according to the present embodiment generates a target image by performing target image detection and distance measurement by infrared transmission / reception. The laser radar device includes a transmitter 11 that emits laser light, a receiver 12 that receives reflected light reflected by an object of the laser light, and a plurality of image sensors that receive reflected light from the receiver 12. An infrared camera 13 (imaging unit), a range finder 14 that calculates a relative distance between the infrared camera 13 and the target at the time of imaging by the infrared camera 13 and outputs a reception timing signal, and a first timing synchronized with the reception timing. A timing generation unit 15 that provides the exposure timing signal of 1 and a second exposure timing signal that is not synchronized with the reception timing to the infrared camera 13, and a plurality of image signals that are captured and output by the infrared camera 13 using each exposure timing signal. An image processing unit 16 for generating image data in which the pixels and the luminance of each pixel are associated with each other; Biaxial gimbal mechanism 17, and a driving portion 18 of the gimbal mechanism 17. The timing generation unit 15, the image processing unit 16, and the driving unit 18 constitute a controller 29. The exposure timing refers to a rising position and a falling position of a timing pulse signal for instructing opening of the shutter.

  The transmitter 11 periodically emits pulsed laser light. The beam shape of the laser beam emitted from the transmitter 11 has a beam axis directed in the target direction, and the infrared intensity is distributed in the space around the beam axis. The receiving unit 12 includes a lens that collects reflected light, a photoelectric conversion photodiode, an avalanche photodiode, and the like.

  The infrared camera 13 includes a plurality of infrared CCDs (infrared charge coupled devices) arranged two-dimensionally on a substrate, an analog / digital converter provided at the subsequent stage of the infrared CCD as the imaging device, and each infrared CCD. A shutter that performs an operation of capturing or not capturing the reflected light and a detector that detects input of a control signal to the shutter are provided. The infrared camera 13 exposes by opening the shutter substantially only at the moment when the reflected light reaches the infrared camera 13. The timing generation unit 15 instructs the infrared camera 13 to open and close the shutter, that is, to perform exposure.

  The range finder 14 acquires distance information to the target. The distance measuring device 14 receives a signal indicating the irradiation time of the laser light from the transmission unit 11 or the timing generation unit 15 and receives a signal indicating the reception time of the reflected light from the reception unit 12.

  FIG. 2 is a diagram for explaining a distance measuring method by the distance measuring device 14. The above described symbols represent the same elements. The light wave radiated into the atmosphere by the transmitter 11 is scattered by the target 19, and part of the reflected wave generated by the scattering returns to the positions of the infrared camera 13 and the distance measuring device 13. If the distance to the target 19 is R, the speed of light is c, and the delay time until the light wave signal is reflected back by the target 19 is τ, the distance measuring device 14 sets the distance R to R = τ · c / 2. calculate.

  The reception timing signal output from the distance measuring device 14 has a waveform that rises from the scheduled arrival time of the reflected light and falls after continuing for the reception period. FIG. 3 shows the relationship between the laser beam transmission / reception timing and the exposure timing.

  FIG. 3A is a time chart showing the timing of laser light irradiation by the transmission unit 11. The delay time τ has a value proportional to the reciprocal propagation distance from the transmission position to the target 19 and returning from the target 19 after the laser light irradiation. FIG. 3B is a time chart showing the reception timing of the reflected light by the receiving unit 12. The scheduled arrival time of the reflected light is substantially equal to the time when the delay time τ elapses after the laser light is emitted. The distance measuring device 14 supplies the reception timing signal 20 shown in FIG. The waveform of the reception timing signal 20 rises from the scheduled arrival time of the reflected light and falls after continuing the reception period. FIG. 3C as a comparative example is a time chart showing the exposure timing of the infrared camera according to the conventional example. FIG. 3D is a time chart showing the exposure timing of the infrared camera 13 by the laser radar device according to the embodiment. In these drawings, the horizontal axis represents the time axis. The vertical axis represents the voltage level.

  In addition, the timing generation unit 15 (FIG. 1) has a first exposure timing signal that has a period that overlaps the reception period of the reflected light reception timing with respect to the infrared camera 13 and that has a timing that matches the arrival time of the reflected light, A second exposure timing signal having a timing that does not overlap with the reception period is supplied. As shown in FIG. 3D, the first exposure timing signal 21 has a waveform that overlaps the reception period of the reception timing signal 20. The second exposure timing signal 22 has a waveform that does not overlap the reception period.

  The image processing unit 16 includes an image difference calculation unit 23 and a frame memory 28. The image difference calculation unit 23 generates image data of the first frame based on the first exposure timing signal 21, and generates image data of the second frame based on the second exposure timing signal 22. The image processing unit 16 obtains a luminance difference between these image data.

  A frame refers to a period required to obtain one image signal in an image area. This frame is a value determined by the element capability of the infrared CCD. In one frame period, after the storage capacitors of the plurality of infrared CCDs of the imaging unit 13 are reset, the infrared CCDs store the charges swept from the photodiodes of the reception unit 12, and the charges are converted into voltage signals by the processor. This is the period until the frame memory 28 is written. For example, infrared CCDs operating at frame rates of 30 Hz, 60 Hz, and 120 Hz have frame periods of 33.3 msec, 16.7 msec, and 8.3 msec, respectively.

  The functions of the image processing unit 16 are executed by, for example, a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array), a volatile memory, and a nonvolatile memory.

  The transmission unit 11, the reception unit 12, the infrared camera 13, and the distance measuring device 14 of FIG. 1 are housed in a casing 24 together with the gimbal mechanism 17. The gimbal mechanism 17 rotates the casing 24 around the azimuth (AZ) axis and the elevation (EL) axis on the base 25. The drive unit 18 adjusts the directivity direction of the gimbal mechanism 17 to be the target detection direction. The laser radar device can track the target by the drive unit 18 rotating a motor (not shown) provided around each axis.

  In addition, the imaging target selection method by the laser radar apparatus according to the present embodiment generates an image signal including a target and a background at a timing that matches the reception timing at which the reflected light is scheduled to return, stores the image data, and receives the reception timing. A method of generating an image signal including a background at a different timing that does not match the image and storing the image data, obtaining a luminance difference for each pixel between these image data, and selectively extracting a target from the image area based on the difference result It is. In this method, a target is extracted based on the difference and a threshold value of luminance that is held in advance, and the target imaging direction and the distance measurement direction are each directed in the target extraction direction.

  The laser radar device according to the present embodiment having such a configuration scans the space area to be monitored. The gimbal mechanism 17 moves the infrared camera 13 in the azimuth and elevation directions. Various types of objects and natural objects are located behind the target as viewed from the infrared camera 13. The laser radar apparatus performs processing for extracting only the target so that the target can be easily seen from the background. An object with very high luminance as a bright background may be imaged as a bright object. The image processing unit 16 performs processing as shown in FIG. 4 at all times or according to the sunshine conditions.

  FIG. 4 is a flowchart for explaining the imaging target selection method. In step A1, the image processing unit 16 generates an image at the timing when the reflected light returns, as in the first exposure timing signal 21 in FIG. The image processing unit 16 forms an image area having a predetermined size in the vertical and horizontal directions, for example, by 10,000 pixels of 100 pixels × 100 pixels. For each of the 10,000 pixels, for example, the image processing unit 16 reads out the luminance level represented by a value in 2048 steps corresponding to 11 bits from the frame memory 28. After imaging with the first exposure timing signal 21, the infrared camera 13 sweeps out 11-bit representation of digital brightness level information to the frame memory 28 for all 10,000 pixels. Image data including both the target and the background is generated for the first frame.

  FIG. 5A is a diagram illustrating an example of an image when the exposure timing is matched with the reception timing of the laser reflected light. This figure shows an image formed from a frame of frame number n. A target echo 27 is captured in the image area 26. An image other than the target echo 27 in the image area 26 represents a background image. Images having different brightness appear at different positions in the image area 26.

  Subsequent to the first frame, in step A2, the image processing unit 16 generates an image at a timing at which reflected light does not return as in the second exposure timing signal 22 of FIG. After the exposure by the second exposure timing signal 22, the infrared camera 13 sends the luminance level information of 10,000 pixels to the frame memory 28. Image data including only the background is generated for the second frame.

  FIG. 5B is a diagram illustrating an example of an image captured when the exposure timing is shifted from the reception timing of the laser reflected light. The figure shows an image formed from a frame of frame number (n + 1) next to frame number n. There is no target echo 27 in the image area 26.

  In step A <b> 3, the image processing unit 16 calculates a difference in luminance level with respect to all of these 10,000 pixels. The image processing unit 16 extracts the image level of the target only by taking the luminance difference between the image data of the frame n where the reflected light returns and the frame (n + 1) where the reflected light does not return.

  FIG. 5C is a diagram illustrating an example of an image after the image processing unit 16 calculates the difference. The image processing unit 16 calculates difference information of luminance levels in 11-bit representation for all 10000 pixels, and forms an image after the difference calculation. Only the target echo 27 is extracted in the image area 26. In the image area 26, unnecessary background images other than the target echo 27 are removed.

  In this way, clutter can be reliably reduced. The above example is an explanation of the calculation using the two frames appearing first in FIG. 3D, and the image processing unit 16 performs the same processing as the above processing a plurality of times for the frames after the first two frames. Repeat.

  In general, in an imaging apparatus used in a laser radar apparatus, the exposure period, the rising position of the exposure timing signal, and the falling position of the exposure timing can be changed and adjusted. The laser radar device according to the present embodiment shifts these positions. The laser radar apparatus uses the infrared camera 13 to capture images at a timing when the reflected light from the object of the laser light irradiated on the target by the laser radar apparatus itself is captured and a timing at which only the background is captured without reflecting the laser reflected light. I do. The laser radar device according to the present embodiment alternately acquires an image at a timing when reflected light is captured and an image at a timing when reflected light is not captured. Only the laser reflected light can be extracted by the laser radar device obtaining a difference between images picked up alternately at the timing when the echo from the object appears and when the echo does not appear. Thereby, the effect of suppressing the clutter component can be obtained.

  As described above, the laser radar apparatus according to the present embodiment is adapted to match the exposure timing with the timing when the laser reflected light is not intentionally received, in addition to matching the exposure timing with the reception timing of the laser reflected light. In this laser radar device, by matching the reception timing of the laser reflected light and the exposure timing of the infrared camera alternately and not matching, the difference between the obtained camera images of adjacent frames is obtained. The background clutter can be removed, and only the laser reflected light representing the target can be extracted.

  In the laser radar apparatus according to the conventional example, the exposure timing is matched with the reception timing of the laser reflected light, and the exposure period for maintaining the exposure is shortened. This laser radar apparatus suppresses the background component and reduces the clutter component by shortening the light receiving period for taking in the background component other than the laser reflected light and the unnecessary echo component. Nevertheless, if there is a clutter with very high brightness, the influence of the background clutter remains, and there are cases where the clutter component cannot be reduced completely. On the other hand, in the laser radar device according to the present embodiment, the influence of background clutter can be reduced.

  In the conventional example, since the frame rate of the infrared CCD is slow, if the difference is calculated between the captured image data, it takes time to calculate, and a system using a laser radar device cannot be realized. In recent years, infrared CCDs having a frame rate of 120 Hz, 240 Hz, or higher have been obtained, and it has become possible to form images with infrared CCDs that can sweep image data at high speed. When the frame rate is doubled, for example, the laser radar device can form two images while obtaining image data of two adjacent frames. The laser radar apparatus according to the present embodiment can perform both generation of a display image and difference calculation by operating the infrared camera 13 at a high frame rate.

  The above-described embodiment is not limited to the embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In the above embodiment, the distance measuring device 14 is provided in the transmission unit 11, but the distance measuring device 14 may be provided in the controller 29.

  Although several embodiments have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 11 ... Transmission part, 12 ... Reception part, 13 ... Infrared camera (imaging part), 14 ... Distance measuring device, 15 ... Timing generation part, 16 ... Image processing part, 17 ... Gimbal mechanism, 18 ... Drive part, 19 ... Target , 20 ... reception timing signal, 21 ... exposure timing signal (first exposure timing signal), 22 ... exposure timing signal (second exposure timing signal), 23 ... image difference calculation unit, 24 ... casing, 25 ... base, 26: Image area, 27: Target echo, 28: Frame memory, 29: Controller.

Claims (4)

A transmitter that emits laser light;
A receiver that receives the reflected light of the laser beam reflected by the object from the transmitter;
An imaging unit having a plurality of imaging elements each receiving the reflected light from the receiving unit;
Calculates the relative distance between the imaging unit and the target at the time when the imaging unit captures an image, and outputs a reception timing signal having a waveform that rises from the scheduled arrival time of the reflected light and lasts for a reception period. A range finder,
A first exposure timing signal having a period that overlaps the reception period of the reception timing signal from the distance measuring device and a timing that matches the reception timing of the reflected light, and a second exposure that does not overlap the reception period A timing generation unit for supplying a timing signal to the imaging unit;
An image processing unit that generates image data in which a plurality of pixels and the luminance of each pixel correspond to each other from an image signal captured and output by the imaging unit according to each exposure timing signal generated by the timing generation unit;
The image processing unit generates an image including the target and the background based on the first exposure timing signal, generates an image including the background based on the second exposure timing signal, and determines the luminance between the images. A laser radar device characterized by obtaining a difference.   The apparatus further comprises a gimbal mechanism of the laser beam sending unit and the imaging unit, and a drive unit that adjusts a directivity direction of the gimbal mechanism to the detection direction of the target, and the target is tracked by the drive unit. The laser radar device according to claim 1. After emitting the laser light, an image including the target and the background is generated by a first exposure timing signal having a timing that matches a reception timing at which the reflected light reflected by the target to be imaged is to return,
Generating an image signal including the background by a second exposure timing signal having a timing that does not match the reception timing;
An imaging target selection method using a laser radar device, wherein a difference in luminance is obtained for each of a plurality of pixels between these images and the target is selected.   4. The laser radar apparatus according to claim 3, wherein the target is extracted based on the difference and a threshold value of brightness held in advance, and the imaging direction of the target and the ranging direction are respectively directed in the target extraction direction. The imaging target selection method by.

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