JP2009288128A - Radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems in a laser radar device for scanning and measuring in the beam direction to an observation object domain wherein, a high SNR cannot be acquired, and fine shape restoration of a target is difficult, since a median procedure for smoothing an image is used for compensation of image deterioration caused by wrong detection or the like. <P>SOLUTION: In this radar device, a laser beam from discharge/detection elements arranged in an array shape is radiated into a space by scanning reciprocally a beam direction by a beam scanning part, and the laser beam reflected by the target is detected by the discharge/detection elements, to thereby measure a distance to the target. In the device, a plurality of image data acquired by each different beam scanning are stored in an image storage part, and a reference value of the distance to the target is set by a reference value setting part, and a plurality of data acquired by observing the same domain by each different beam scanning are compared with the reference value by a data comparison part, and image data determined from the comparison result by a data determination part and then output are stored in an output storage part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radar apparatus that measures a distance to an object using a beam-like electromagnetic wave, and more particularly to a technique for compensating for image degradation such as distance information.

  A radar device is known as a device for measuring the position of an object existing at a remote point. The radar device radiates waves such as electromagnetic waves and sound waves to the space, receives the waves reflected by the target object, and analyzes the signal to measure the distance and angle from the radar device to the object. The distance of the object can be measured, for example, by performing a pulse modulation on the radiated electromagnetic wave and measuring the time difference between the radiated transmission pulse and the reception pulse that is a reflected wave from the object.

  Further, if the radiated electromagnetic wave is made into a beam shape and the angle of this transmission beam is measured while scanning, observation in different angular directions becomes possible. In particular, a laser radar that uses light as an electromagnetic wave is a pencil beam that has a very small beam spread, and can observe an object with high angular resolution. Therefore, for example, it is used for measurement of multidimensional distance images. There exists a thing as described in "Laser handbook" (nonpatent literature 1) as a measurement of the distance using such a pencil beam. However, laser radar as a distance measurement using a pencil beam has a problem that the observation period (frame period) is long and the field of view is narrow due to the narrow beam width.

The problem that the observation width (frame period) is long and the field of view is narrow due to such a narrow beam width can be improved by using a plurality of detection elements arranged in an array, for example. Yes. As such a technique, there exists a thing of Unexamined-Japanese-Patent No. 2005-331273 (patent document 1), for example.
As described above, in a radar apparatus that performs beam scanning, the measurement of a predetermined area is usually performed by repeating reciprocating scanning with respect to the observation target area or unidirectional scanning only on the forward path or only on the return path. Has been done.

  When the above observations are made, the distance between the target and the antenna is often not high SNR (Signal to Noise Ratio) due to atmospheric attenuation in the laser radar processing equipment. Image degradation occurs. The false detection indicates a case where the noise level is higher than the power peak of the reflected wave from the target and the correct distance cannot be measured.

JP 2005-331273 A Laser Society / Edition, “Laser Handbook”, Ohmsha April 2005, p559-561

  A median method has been used as a compensation method for the occurrence of image degradation due to false detection or the like because a high SNR cannot be obtained. However, since this method smoothes the image, it is difficult to restore the fine shape of the target object.

  The present invention has been made to solve the above-described problems, and an object thereof is to compensate for image deterioration such as distance information.

The radar apparatus according to the present invention is
A beam radiating portion in which a plurality of emitting / detecting elements for radiating beam-like waves to space and detecting beam-like waves reflected by a target in space are arranged in an array, and a beam emitted from the beam radiating portion A radar device that includes a beam scanning unit that reciprocally scans the direction and measures the distance to the target, an image storage unit that stores a plurality of image data obtained by different beam scans, and a distance to the target Comparison result of a reference value setting unit for setting a reference value, a data comparison unit for comparing a plurality of data obtained by observing the same region by different beam scans and a reference value set by the reference value setting unit, and a comparison result of the data comparison unit A data determination unit that determines and outputs image data from the image data, and an output storage unit that stores the result of the data determination unit.

  According to the radar apparatus of the present invention, a plurality of data is obtained by observing the same observation region by different beam scans, and the difference from the reference value is the smallest compared with the reference value of the distance to the target set separately. Since the data is used as the observation data, the degradation of the image such as distance information is compensated, and the accuracy of the finally obtained image is improved.

Embodiment 1 FIG.
In the beam scanning according to the first embodiment of the present invention, the observation range is measured by reciprocating the beam direction with respect to the predetermined observation range. In that case, assuming that there are pixels to be observed repeatedly in the observation region in each scan, a simulation diagram is shown in FIG. FIG. 1 shows the same number of pixels every time a platform equipped with a radar device having n array elements arranged in a row according to the first embodiment moves in the direction of arrow V by half of one pixel width of the array pixels. Several n beams arranged in a row are emitted. When this operation is repeated m / 2 times, the platform on which the radar device is mounted moves half by one pixel width in the original direction (the direction opposite to the arrow V), and the pixels n are arranged in one column for each movement. And move while emitting the same number of n beams.

  The beam scanning method is not limited to this, and any method may be used as long as it can observe the ground surface or a target and an overlapping portion exists between each scanning. In addition, the altitude of the platform on which the radar device is mounted is L (m), and the distance resolution is dh (m). The traveling direction of the platform is the array element direction, and the direction perpendicular to the array element direction is the scan direction. At that time, a plurality of points on the ground surface or the target are observed using a plurality of sensing elements arranged in an array. The entire area observed by each pulse array transmission / reception is defined as an array pixel column. A simplified diagram is shown in FIG. Assume that there are n array elements, and n observation points (array pixels) associated therewith can be observed. Further, if the irradiation depression angle to each array pixel is represented by θ (n) and θ (n) is known, the distance D (n) in the line-of-sight direction to the flat ground is represented by Equation 1.

Further, the array pixel interval P is expressed by Equation 2.

However, the scanning method, usage environment, etc. are not limited to those shown in FIGS. In this embodiment, such a situation is assumed for the sake of simplification of the description. However, any environment in which the target or the ground surface can be observed is acceptable. If it is a formula, it is not necessary to use these formulas. The array element shown in FIG. 2 emits an n-width beam, reciprocally scans as shown in FIG. 1, and obtains a radar image using observation data.
Hereinafter, in the present embodiment, it is assumed that observed data is image data, and the image data includes distance information. This is also effective when the pixel value includes something other than distance information. In addition, it is assumed that the alignment of each pixel has been completed in the N radar images having the same observation area, and the image composition processing has been performed.

  FIG. 3 is a simplified diagram of the names of each direction and the obtained image. It is assumed that an n × m pixel radar image having n pixels in the array element direction and m pixels in the scan direction is created. The pixel value stored in each pixel is a distance D (n, m).

  FIG. 4 is a block diagram showing the configuration of the image processing portion according to the first embodiment of the present invention. The image storage unit 1 stores a composite of N images observed by different scans, and the output storage unit 3 stores the output of the control unit 2. In this embodiment, it is assumed that N = 2 for simplification of description. In the control unit 2, a determination is made for the value that enters each pixel, and the correct value is stored in the output storage unit 3. As a function of the control unit 2, first, which one of the two distance data is selected in the overlapping pixel is controlled. At this time, the determination is performed using a reference distance value (reference value). The reference value setting unit 21 sets the reference value. Next, the data comparison unit 22 compares which pixel data is valid using the reference value set by the reference value setting unit 21. Based on the comparison result, the data determination unit 23 determines what data is stored in the target pixel.

A method for setting a reference value in the reference value setting unit 21 will be described.
The user uses the reference value setting unit 21 to set a predetermined reference value, and the data comparison unit 22 uses this reference value for comparison.
Another method is to perform the processing shown in FIG. In step ST200, the image data of the target (target) in the observed radar image and the image data of the database held in advance are read and compared (ST200), and the image data in the database is referred to. Thus, the reference value is set and read (ST210).

  In addition to using a database as a reference value setting method in the reference value setting unit 21, there is a method of setting a reference value from the top to the bottom in the scanning direction. The simulation is shown in FIG. When setting the reference value of the array pixel column (m), the average value of the values of each pixel in the array pixel column (m−1) is used. In order to calculate the average value of each pixel in the array pixel column (m-1), not only the values of all the pixels in the array pixel column (m-1) are used, but also the array pixel column (m-1 ) May be the value of every other pixel or the average value of every other value. This average value corresponds to the reference value of the center pixel of the array pixel array (m), and there is a method in which each pixel of the array pixel array (m) is set based on this reference value. This is passed to the data comparison unit 22. Incidentally, the value of each pixel of the array pixel array (m−1) is used after compensation, that is, after the value determined by the data determining unit 23 is used or before compensation, that is, before determined by the data determining unit 23. Whether to use the value of can be determined freely.

  In addition, in setting the reference value in the reference value setting unit 21, not only the array pixel column (m-1) but also the array pixel column (m-1) to the array pixel when obtaining the reference value of the array pixel column (m). It is also possible to use pixel values of a plurality of array pixel columns in the column (1).

  Further, a reference value setting method in the reference value setting unit 21 will be described. First, let B (n, m) be the reference value for each pixel. After setting the reference value B (n / 2, m) of the center pixel of the array pixel row in the above method, the known dip angle θ and equation (2) are used, and further, the reference distance is calculated using equation (3). calculate. Since the distance between adjacent pixels of each array pixel is determined by Equation (3), it is possible to set the reference values of other array pixels on the same array column as long as the reference value of the array center pixel is known. As an example, if you want to find the reference value of the pixel on the 1 pixel platform side of B (n / 2, m),

  Is required. However, although the expression (3) is used for the calculation, it is not necessary to use this, and any other expression may be used as long as it can calculate the theoretical distance of the line-of-sight direction of each array pixel.

  Regarding the reference value setting method in the reference value setting unit 21, in addition to the above method, when a reference value is set for each pixel, the values of B (1, m) and B (n, m) are set to H / W There is also a method of feeding back to the signal detection unit 4 (beam radiation unit arranged in an array). The configuration diagram is shown in FIG. In an ideal embodiment of this method, analog peak detection is assumed. Next, when the approximate value of the distance or time of the array pixel to be observed is known, the surrounding peak can be detected. As the effect, an effect of lowering the erroneous detection occurrence probability is assumed. However, instead of the reference value, the values D (1, m) and D (n, m) stored in the array pixels are also possible, and the H / W signal detector 4 (beams arranged in an array) Any value can be used as long as the value can be referred to in the radiation unit.

  Further, the method of the reference value in the reference value setting unit 21 can be set using the pixel value in the window 5100 surrounding the pixel 3000 for which the reference value is to be set as shown in FIG. As the setting method, there is a method of taking an average value of pixel values in the window 5100, or the like. The size of this window 5100 is variable.

Processing of the data comparison unit 22 will be described.
After the reference value is set by the reference value setting unit 21, the data comparison unit 22 selects data using the reference value set by the reference value setting unit 21 in the data duplication area. The processing flow is shown in FIG. As described above, the present invention is a compensation method for pixels in which the same region is observed. Therefore, first, assume that there is image data 1 and image data 2 in which the same region is observed. The reference value set by the reference value setting unit 21 is read (ST500). Next, image data 1 and image data 2 are read (ST510). The difference between the reference value set by the reference value setting unit 21 and the image data 1 and the image data 2 is calculated (ST520). The two difference data are compared, the image data with the smaller difference is adopted as the value of the pixel, and temporarily stored in the image output unit (ST530).

The process of the data determination unit 23 will be described.
A processing flow diagram of the data determining unit 23 is shown in FIG. The data determining unit 23 first sets an effective range threshold (ST600). Next, the comparison result of the data comparison unit 22 is read (ST610), and it is determined whether the comparison result is within the effective range threshold (ST620). If the comparison result is within the effective range threshold value, the process proceeds to step ST640 as it is and stored in the output storage unit 3. If not, the process proceeds to the image data creation process (ST630). This process has an effect of discriminating whether the image data is not malignant, and is for reducing the influence of image deterioration given by malignant data.
The effective range threshold value may be any value as long as an appropriate value can be obtained, such as setting by the user, use of a database, or use of other pixel values.

  The data creation process is described below. When the malignant data pixel 4000 exists as shown in FIG. 11, a window 5200 is set around the malignant data pixel 4000, and the average value of the surrounding pixels is substituted into the malignant data pixel 4000. In addition, there are methods such as median processing and a method of setting the value of the malicious data pixel 4000 to 0. Any other data may be used as long as different data is substituted into the malignant data pixel 4000 to suppress image deterioration.

  As described above, the accuracy of the finally obtained image may be improved by automatically selecting valid data existing in overlapping pixels and performing processing when both are malignant. . It is also possible to improve the H / W processing speed by feeding back the data being processed to the H / W.

  The radar device according to the present invention is mounted on, for example, an aircraft and may be used for a radar or the like that observes weather conditions on the surface of the earth.

FIG. 6 is a simulation diagram when measurement is performed by reciprocating the beam direction with respect to a predetermined observation range so that overlapping observation pixels exist. It is a simplified diagram for explanation in which the entire observation region is an array pixel array by pulse array transmission / reception. It is a simple figure of the name of an observation direction, and the image obtained. FIG. 2 is a block diagram showing a configuration of an image processing portion according to Embodiment 1 of the present invention. It is a processing flow figure of a reference value setting part. It is a simulation diagram when the reference value is set from the upper side to the lower side in the scanning direction in the reference value setting unit. It is a block diagram which shows the other structure of an image processing apparatus. It is explanatory drawing of the reference value setting example in a reference value setting part. It is a processing flow figure in a data comparison part. It is a processing flowchart of a data determination part. It is operation | movement explanatory drawing of a data creation process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1; Image storage part, 2; Control part, 3; Output storage part, 21; Reference value setting part, 22: Data comparison part, 23: Data determination part, 4; H / W signal detection part

Claims (10)

  A beam radiating portion in which a plurality of emitting / detecting elements for radiating beam-like waves to space and detecting beam-like waves reflected by a target in space are arranged in an array, and a beam emitted from the beam radiating portion A radar device that includes a beam scanning unit that reciprocally scans the direction and measures the distance to the target, an image storage unit that stores a plurality of image data obtained by different beam scans, and a distance to the target Comparison of a reference value setting unit for setting a reference value, a data comparison unit for comparing a plurality of image data obtained by observing the same region by different beam scans and a reference value set by the reference value setting unit, and a data comparison unit A radar apparatus comprising: a data determination unit that determines and outputs image data from a result; and an output storage unit that stores a result of the data determination unit.   The radar apparatus according to claim 1, wherein the reference value setting unit extracts and sets a reference value of a pixel for which a reference value is to be obtained from a database prepared in advance.   The radar apparatus according to claim 1, wherein the reference value setting unit sets a reference value of a pixel for which a reference value is to be obtained, as designated by a user.   2. The radar apparatus according to claim 1, wherein the reference value setting unit calculates and sets the reference value by using an average of reference values of surrounding pixels of a pixel whose reference value is to be obtained.   The reference value setting unit sets a reference value for all elements in the array element direction that is perpendicular to the scan direction in time-sequential order in the scan direction for beam scanning, and the reference value to be set is 1 for which image data has already been determined. The radar apparatus according to claim 1, wherein an average value of pixel values of a plurality of pixels in the array element array in front of the array is used.   The reference value setting unit sets a reference value for all elements in the array element direction that is perpendicular to the scan direction in time-sequential order in the scan direction in which the beam is scanned. An average value of a plurality of pixels in the previous array element row is used as a reference value for the central pixel of the array element row, and a reference value is set for each array element in the array element row based on this reference value. The radar apparatus according to claim 1, wherein:   The data comparison unit performs a process of taking a difference between the reference value set by the reference value setting unit and a plurality of pixel values obtained by observing the pixel, and selecting a pixel value having the smallest difference. Item 7. The radar device according to any one of Items 2 to 6.   8. The radar apparatus according to claim 7, wherein the data determination unit sends the image data having the smallest difference from the reference value selected by the data comparison unit as a pixel value to the output storage unit.   The data determining unit sets an effective range threshold of the image data pixel value by the user, and when the pixel value of the image data selected by the data comparison unit is within the effective range threshold, sends the image data to the output storage unit, 9. The radar apparatus according to claim 8, wherein when the value is outside the threshold value, an alternative pixel value is calculated, and the calculated alternative pixel value is sent to the output storage unit.   The data determination unit sets an effective range threshold value of the image data pixel value using a database prepared in advance, and outputs and stores the image data when the pixel value of the image data selected by the data comparison unit is within the effective range threshold value 9. The radar apparatus according to claim 8, wherein when the value is outside the effective range threshold value, the substitute pixel value is calculated, and the calculated substitute pixel value is sent to the output storage unit.

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