JP4886622B2 - Scan converter, radar apparatus, and scan conversion method - Google Patents

Description

  The present invention relates to a scan converter used in a radar apparatus, and more particularly to a scan converter, a radar apparatus, and a scan conversion method used when displaying a radar video on a raster scan type display such as a CRT.

  In the conventional scan conversion method in the radar apparatus, the pixel coordinates (x, y) on the display are obtained one by one by converting the polar coordinates indicated by the azimuth θ and the distance r into orthogonal coordinates. In parallel with this coordinate conversion, echo data is calculated, and the calculated echo data is output to the display by writing the pixel coordinates (x, y) obtained by the scan converter to the frame buffer as an address.

  However, in the conventional scan conversion method, the calculation result of trigonometric functions such as sin and cos is used when converting from polar coordinates to orthogonal coordinates, so that it is not converted due to distance resolution, azimuth resolution, calculation error, rounding error, etc. Dots may occur. Echo data is not written at this point, and the echo data is completely lost. This phenomenon becomes prominent when the radius of the PPI (Plan Position Indicator) is increased, and this is particularly problematic when a high-resolution large-screen display is used.

Therefore, as a conventional technique, a method of interpolating missing data with software or correcting by expanding in the horizontal and vertical directions with hardware has been proposed (for example, see Patent Document 1). However, both are corrections after scan conversion, and it cannot always be said that the original video data is faithfully reproduced.
JP-A-7-92254

  As described above, the conventional scan conversion method uses a trigonometric function when converting from polar coordinates to Cartesian coordinates, so it takes time to calculate, and there are points that are not converted due to distance resolution, orientation resolution, calculation error, rounding error, etc. There is a case. In addition, even when a method for correcting missing data is used, when performing magnified display, especially when enlarging and displaying the periphery of the radar coverage, the time required for rendering increases and the rendering update rate decreases. There was a point.

  The present invention has been made paying attention to the above circumstances, and the object of the present invention is to provide a scan converter and a radar apparatus capable of reproducing data such as radar echoes at high speed without omission even when enlarged display is performed. And providing a scan conversion method.

  In order to achieve the above object, a scan converter according to the present invention is used in a radar apparatus that forms a reception beam in a plurality of directions and measures a signal intensity with respect to a distance from a reception echo in each direction. A scan converter that converts signal intensity information for each distance into a raster video for display on a display scope screen, and stores coordinates of both ends of a line segment corresponding to a detection distance corresponding to each of the plurality of directions. Storage means, receiving means for receiving information for designating a screen display area of the display scope, measurement results for each of the plurality of directions are input, and each time the measurement results are input, a line segment corresponding to the measurement direction The coordinates of both ends of the are read from the storage means, one of the coordinates of the read both ends is the starting point, the other coordinates The distance indicated by the measurement result is converted into a coordinate point on the line segment until it exceeds the designated screen display area toward a certain end point, and signal intensity information corresponding to the distance is drawn at the converted coordinate point. And converting means for converting into the raster video.

  The radar apparatus according to the present invention is used in a radar apparatus that forms a reception beam in a plurality of directions and measures a signal intensity with respect to a distance from a reception echo in each direction. A radar device for converting intensity information into a raster video for displaying on a screen of a display scope, the storage means storing the coordinates of both ends of a line segment corresponding to a detection distance corresponding to each of the plurality of directions; A receiving means for receiving information for designating a screen display area of a display scope, and measurement results for each of the plurality of directions are input. Each time the measurement results are input, coordinates of both ends of a line segment corresponding to the measurement direction are obtained. Read from the storage means, the specified point from one of the coordinates of the read both ends to the end point that is the other coordinate The distance indicated by the measurement result is converted into a coordinate point on the line segment until the surface display area is exceeded, and the signal strength information corresponding to the distance is drawn at the converted coordinate point to convert it to the raster video. Conversion means.

  Further, the scan conversion method according to the present invention is used in a radar apparatus that forms a reception beam in a plurality of directions and measures a signal intensity with respect to a distance from a reception echo in each direction. A scan conversion method for converting signal intensity information into a raster video for display on a display scope screen, storing coordinates of both ends of a line segment corresponding to a detection distance corresponding to each of the plurality of directions, and displaying the display Information specifying the screen display area of the scope is received, measurement results for each of the plurality of directions are input, and each time the measurement results are input, the coordinates of both ends of the line segment corresponding to the measurement direction are read and read. One of the coordinates at both ends is set as the start point, and the specified screen display area is exceeded toward the end point that is the other coordinate. Until the distance indicated by the measurement result is converted to a coordinate point on the line segment, and signal intensity information corresponding to the distance is converted to the raster video by drawing at the converted coordinate point. To do.

  In the scan converter, the radar apparatus, and the scan conversion method configured as described above, both end coordinates of the line segment corresponding to the detection distance corresponding to each direction are stored in advance. Also, information specifying the screen display area of the display scope is received. Each time the measurement result of each direction is input as a radar video, the start point and end point coordinates corresponding to each direction are read out, and the line segment from this start point to the end point is calculated. . Then, the measured distance is converted into the coordinate point of the line segment, and the signal intensity is drawn at the coordinate point corresponding to each distance, thereby converting into the raster video.

  With this configuration, trigonometric functions need not be calculated, and high-speed operation is possible with a simple circuit configuration. In addition, the processing time can be shortened by stopping the drawing processing of the portion beyond the screen display area.

  Therefore, according to the present invention, it is possible to provide a scan converter, a radar apparatus, and a scan conversion method capable of reproducing data such as radar echoes at high speed without omission even when enlarged display is performed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a first embodiment of a radar apparatus according to the present invention. The radar apparatus includes a scan converter 10, a transmitter 11, an antenna 12, a receiver 13, a signal processing device 14, a screen output device 15, a CPU 16, and a display device 17.

  The pulse waveform data generated in the transmitter 11 is up-converted to the transmission frequency, amplified in power, and then transmitted from the antenna 12 to the air as a radar pulse. The radar pulse transmitted from the antenna 12 is reflected by the target, captured as a radar echo by the reception beam formed by the antenna 12, and amplified and detected by the receiver 13. The radar apparatus rotates the antenna 12 at a predetermined speed to execute the transmission / reception process for a plurality of directions.

  The signal processing device 14 performs filter processing and the like on the received echoes of each direction supplied from the receiver 13 to remove unnecessary components such as noise and clutter, and calculates echo reflection intensity and the like. The calculated data is input to the scan converter 10 as a radar video, and the scan converter 10 converts the radar video into a raster video so that it can be output to a raster scan display such as a CRT. Under the control of the CPU 16, the screen output device 15 superimposes a map, a symbol, and the like in addition to the scan-converted radar image and outputs it to the display device 17. FIG. 2 is a screen display example when the display device 17 is configured with a PPI scope. In the PPI scope, the origin of display is the antenna position, and the sweep is performed in synchronization with the rotational direction of the beam, and the length from the origin to the outer circumference represents the distance.

FIG. 3 is a functional block diagram showing the scan converter 10 shown in FIG.
The scan converter 10 includes an input video buffer 1, a start point / end point memory 2, a CPU 3, a coordinate calculation unit 4, a signal intensity maximum value detection unit 5, a frame buffer 6, and a display area setting unit 7. The scan converter 10 draws a line segment of length r radially from the center point of the PPI scope, and performs scan conversion by assigning echo data to each linear pixel.

  In the input video buffer 1, signal strength information for each distance of a plurality of directions supplied from the signal processing device 14 is held. The start point / end point memory 2 stores the coordinates of both ends of the line segment corresponding to the detection distance corresponding to each direction from the radar center calculated by the CPU 3. The coordinate calculation unit 4 reads out the coordinates of both ends of the line segment corresponding to the designated orientation from the start point / end point memory 2, sets one of the read coordinates at both ends as the start point, the other as the end point, and the start point to the end point. Calculate the coordinate array that represents the line segment connecting For the calculation of the line segment, for example, Bresenham's line segment drawing algorithm is used. Since this algorithm can draw a line segment between two arbitrary points only by addition and subtraction, the calculation process can be performed at higher speed.

  The display area setting unit 7 sets a display area in the coordinate calculation unit 4 based on information representing the display area displayed on the screen of the display device 17 specified by the CPU 3. The coordinate calculation unit 4 calculates the coordinate arrangement in the display area set by the display area setting unit 7.

  The signal strength maximum value detection unit 5 detects the maximum value among the signal strengths corresponding to each pixel on the line segment obtained by the coordinate calculation unit 4. In the frame buffer 6, the color data based on the maximum value of the signal intensity detected by the signal intensity maximum value detection unit 5 is written in each pixel on the line calculated by the coordinate calculation unit 4, thereby performing the PPI scan (polar coordinate system). Performs scan conversion to raster scan (orthogonal coordinate system).

Next, the operation of the scan converter 10 configured as described above will be described.
In FIG. 3, the scan converter 10 receives θ (azimuth), r (distance), and I (signal intensity) from the signal processing device 14, and uses the values of θ and r as addresses to the input video buffer 1 that is a dual port memory. Write signal strength I. The start point / end point memory 2 stores both end coordinates (xs, ys) and (xe, ye) corresponding to the detection distance corresponding to each azimuth θ of the beam. Normally, initial values are stored, but when the parallel movement or enlargement / reduction of the center point of the PPI scope is performed, the CPU 3 calculates and updates all coordinates. In the case of the PPI scan, for example, (xs, ys) is coordinates (x0, y0) corresponding to the center of the radar, and (xe, ye) is R × sin θ + x0, R × where R is the radar detection distance. The value of cos θ + y0 is calculated by the CPU 3 and rounded to an integer.

  The coordinate calculation unit 4 reads both end coordinates of the line segment corresponding to the value of the azimuth θ held in the input video buffer 1 from the start point end point memory 2 and connects between (xs, ys) and (xe, ye). A coordinate array (x1, y1) to (xi, yi) (i is a natural number) representing the ellipse segment is calculated. For this calculation, Bresenham's line drawing algorithm is applied. Bresenham's algorithm requires only the coordinates of the start point and end point of a line segment, can determine the coordinates of a point on the line segment by addition / subtraction and shift operations, and is suitable for hardware because it does not require multiplication / division.

  A measurement result (a set of signal intensity I and distance r) corresponding to the azimuth θ is supplied from the input video buffer 1 to the signal intensity maximum value detection unit 5. The signal strength maximum value detection unit 5 converts each distance r into a coordinate point on the line segment obtained by the coordinate calculation unit 4, and detects the maximum value Imax from the signal strength I corresponding to this coordinate point. . The pixel coordinates on the line segment (x1, y1) to (xi, yi) are used as addresses, and pixel color data Imax1 to i obtained from the signal intensity maximum value detection unit 5 are written in the frame buffer 6 to perform PPI scanning. Perform scan conversion from (polar coordinate system) to raster scan (orthogonal coordinate system).

  By the way, the coordinate calculation unit 4 calculates the above-described coordinate arrangement in the display area displayed on the screen of the display device 17 set by the display area setting unit 7. The method is described in detail below.

  FIG. 4 is a flowchart showing the procedure of the line drawing process and its contents. When receiving the setting of the display area from the display area setting unit 7 (step S4a), the CPU 3 determines the position from the coordinate corresponding to the center of the radar to the set display area (step S4b).

  In this determination, when it is determined that the display area includes or is close to the center of the radar, line drawing is performed as shown in FIG. That is, the CPU 3 stores the point Ai on the circumference having the center point O as the start point and the radius of the maximum detection distance R as the end point in the start point / end point memory 2 (step S4c). The coordinate calculation unit 4 reads the coordinates corresponding to θ from the start point / end point memory 2, and performs line drawing from the center point O toward the point Ai on the circumference until the display area is exceeded (steps S4d and S4e). When the display area is exceeded in the determination in step S4e, the coordinate calculation unit 4 aborts the line drawing (step S4f), and performs the next line drawing process (step S4g).

  On the other hand, if it is determined in step S4b that the display area is far from the center of the radar (close to the outer periphery), line drawing is performed as shown in FIG. In this case, the CPU 3 stores the point Ai on the circumference having the radius of the maximum detection distance R as the start point and the center point O as the end point in the start point / end point memory 2 (step S4h). The coordinate calculation unit 4 reads the coordinates corresponding to θ from the start point / end point memory 2 and performs line drawing until the display area is exceeded from the point Ai on the circumference toward the center point O (steps S4i, S4j). When the display area is exceeded in the determination in step S4j, the coordinate calculation unit 4 aborts the line drawing (step S4k) and performs the drawing process for the next line (step S41).

  As described above, in the first embodiment, both end coordinates of the line segment corresponding to the detection distance corresponding to each direction are stored in advance in the start point / end point memory 2. The display area setting unit 7 sets a display area in the coordinate calculation unit 4 based on information for designating the screen display area of the display device according to an instruction from the CPU 3. Each time the measurement results (distance and signal intensity) of each azimuth are input to the input video buffer 1 as radar video, the coordinate calculation unit 4 obtains the start and end coordinates of the line segment corresponding to each azimuth from the start / end point memory 2. read out. The coordinate calculation unit 4 converts the distance indicated by the measurement result to the coordinate point on the calculated line segment until it exceeds the display area set by the display area setting unit 7 from the read start point to the end point. By rendering the signal intensity corresponding to each distance in the frame buffer 6 of the converted coordinate point, it is converted into raster video.

  Therefore, according to the first embodiment, since calculation of trigonometric functions is not required, high-speed operation is possible with a simple circuit configuration, and more accurate display can be performed at high speed without causing loss of echo data. It becomes possible. In addition, compared to the case where all coordinates are calculated from the start point to the end point regardless of the screen display area, the calculation beyond the screen display area does not affect the screen display, so the processing is terminated. Thus, the processing time can be shortened. That is, the coordinate conversion process of the broken line portion in FIGS. This process is particularly effective when the display area is close to the center point of the PPI or close to the peripheral edge of the PPI.

  In the first embodiment, which of the center point and the point on the circumference is determined as the starting point is determined by the distance from the center of the radar to the display area. In this way, line drawing processing can be performed at high speed. This is because the CPU 3 can change the direction of line drawing only by switching the start point and end point according to the position of the screen display area.

(Second Embodiment)
In the second embodiment, a method for further speeding up the processing of the coordinate calculation unit 4 of the first embodiment will be described. In the second embodiment, since the configuration of the scan converter is the same as that of the first embodiment, description will be made with reference to FIG. 3 in the first embodiment.

  FIG. 7 is a flowchart showing the procedure of the line drawing process and its contents in the scan converter of the second embodiment. When receiving the setting of the display area from the display area setting unit 7 (step S7a), the CPU 3 determines the position from the coordinate corresponding to the center of the radar to the set display area (step S7b).

  In this determination, if it is determined that the display area includes the center of the radar or is close to the center of the radar, as shown in FIG. 8, the starting point is brought closer to the display area in order to further speed up the drawing. That is, the CPU 3 calculates a point Bi on the circle inside the screen display area from the center point O toward the point Ai on the circumference having the maximum detection distance R as a radius, and stores the point Bi in the start point / end point memory 2. Is stored as a starting point (step S7c). Then, the coordinate calculation unit 4 reads a point Bi from the start point / end point memory 2 as a start point and a point Ai on the circumference having a radius of the maximum detection distance R as an end point (step S7d), and a point Ai on the circumference from the point Bi. Line drawing is performed until the display area is exceeded (steps S7e, S7f). When the display area is exceeded in the determination in step S7f, the coordinate calculation unit 4 aborts the line drawing (step S7g), and performs the next line drawing process (step S7h).

  On the other hand, if it is determined in step S7b that the display area is close to the outer periphery of the PPI, line drawing is performed as shown in FIG. In this case, the CPU 3 calculates a point Ci on the circle outside the screen display area from the point on the circumference having the maximum detection distance R as the radius toward the center point O, and stores the point Bi in the start point / end point memory 2. Is stored as a starting point (step S7i). Then, the coordinate calculation unit 4 reads the point Ci as the start point and the center point O as the end point from the start point / end point memory 2 (step S7j), and draws a line until the display area is exceeded from the point Ci on the circumference toward the center point O. (Steps S7k, S7l). When the display area is exceeded in the determination in step S71, the coordinate calculation unit 4 aborts the line drawing (step S7m) and performs the next line drawing process (step S7n).

  In the second embodiment, the radar video is enlarged, and when the center of the PPI is not in the screen display area, line drawing is performed with the start point closer to the end point toward the screen display position. Thereby, the line drawing process can be further shortened than in the first embodiment. As a result, one line can be drawn in a substantially constant time regardless of the radar video screen display area and the enlargement ratio.

  As described above, by using the present invention, enlarged scan conversion is possible without causing data loss such as radar echo. Also, the line drawing time can be shortened by setting the start and end points of the line and the line drawing direction in accordance with the screen display area / magnification ratio in the radar coverage area. As a result, the update rate of scan conversion can be improved.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in each embodiment. Furthermore, you may combine suitably the component covering different embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows 1st Embodiment of the radar apparatus which concerns on this invention. The figure which shows the example of a screen display of a PPI scope. 1 is a functional block diagram showing a first embodiment of a scan converter according to the present invention. 6 is a flowchart showing a procedure of line drawing processing and its contents in the scan converter of the first embodiment. FIG. 3 is a diagram illustrating line drawing by the scan converter according to the first embodiment. FIG. 3 is a diagram illustrating line drawing by the scan converter according to the first embodiment. 9 is a flowchart showing the procedure of line drawing processing and its contents in the scan converter of the second embodiment. The figure which shows the line drawing by the scan converter of 2nd Embodiment. The figure which shows the line drawing by the scan converter of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Scan converter, 11 ... Transmitter, 12 ... Antenna, 13 ... Receiver, 14 ... Signal processing device, 15 ... Screen output device, 16 ... CPU, 17 ... Display device, 1 ... Input video buffer, 2 ... Start point end point Memory, 3 ... CPU, 4 ... coordinate calculation unit, 5 ... signal intensity maximum value detection unit, 6 ... frame buffer, 7 ... display area setting unit.

Claims (5)

Used in a radar device that forms reception beams in a plurality of directions and measures the signal intensity with respect to the distance from reception echoes in the respective directions, and displays signal intensity information for the distances in the plurality of directions on the display scope screen. A scan converter that converts to raster video for
Storage means for storing coordinates of both ends of a line segment corresponding to a detection distance corresponding to each of the plurality of directions;
Receiving means for receiving information for designating a screen display area of the display scope;
The measurement results of each of the plurality of directions are input, and each time the measurement results are input, the coordinates of both ends of the line segment corresponding to the measurement direction are read from the storage means, A signal corresponding to the distance is calculated by converting the distance indicated by the measurement result into a coordinate point on the line segment until the specified screen display area is exceeded toward the end point which is the other coordinate from the start point. A scan converter, comprising: conversion means for converting the raster information into the raster video by drawing the intensity information at the converted coordinate points.   The conversion means starts from one of the coordinates at both ends read from the storage means based on the distance from the coordinate corresponding to the center of the radar to the designated screen display area. The scan converter according to claim 1.   The scan converter according to claim 1, wherein the conversion unit further brings the start point closer to the designated screen display area toward the end point. Used in a radar device that forms reception beams in a plurality of directions and measures the signal intensity with respect to the distance from reception echoes in the respective directions, and displays signal intensity information for the distances in the plurality of directions on the display scope screen. A radar device for converting to a raster video for
Storage means for storing coordinates of both ends of a line segment corresponding to a detection distance corresponding to each of the plurality of directions;
Receiving means for receiving information for designating a screen display area of the display scope;
The measurement results of each of the plurality of directions are input, and each time the measurement results are input, the coordinates of both ends of the line segment corresponding to the measurement direction are read from the storage unit, and any of the read coordinates of both ends is read. A signal corresponding to the distance is calculated by converting the distance indicated by the measurement result into a coordinate point on the line segment until the specified screen display area is exceeded toward the end point which is the other coordinate from the start point. A radar apparatus comprising: conversion means for converting intensity information into the raster video by drawing at converted coordinate points. Used in a radar device that forms reception beams in a plurality of directions and measures the signal intensity with respect to the distance from reception echoes in the respective directions, and displays signal intensity information for the distances in the plurality of directions on the display scope screen. A scan conversion method for converting to raster video for
Storing the coordinates of both ends of the line segment corresponding to the detection distance corresponding to each of the plurality of directions;
Accept information specifying the screen display area of the display scope,
Measurement results for each of the plurality of azimuths are input, and each time the measurement result is input, the coordinates of both ends of the line segment corresponding to the measurement azimuth are read, and either one of the read coordinates of both ends is the starting point. The distance indicated by the measurement result is converted into a coordinate point on the line segment until the specified screen display area is exceeded toward the end point which is the other coordinate, and signal intensity information corresponding to the distance is converted. A scan conversion method, wherein the raster video is converted into the raster video by drawing at the coordinate points.

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