JP2010286359A - Signal processor, radar device including the signal processor, and method of detecting pixel omission of the signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a configuration reliably detecting pixel omission occurring at diversified positions and in diversified sizes in a signal processor for drawing information based on echo signals in an image, where pixels are disposed in a matrix, for displaying on a display while transmitting search signals by allowing orientation to differ. <P>SOLUTION: A pixel omission detection section equipped in a radar device detects pixel omission, based on positions of pixels of a current sweep line, namely a sweep line to be drawn this time and positions of pixels of the last sweep line, namely a sweep line processed last time. More specifically, the pixel omission detection section determines that an intermediate pixel is a pixel omission section when there are not less than one intermediate pixels sandwiched between a target pixel, namely a pixel on the current sweep line, and a corresponding pixel, namely a pixel on the last sweep line corresponding to the target pixel in the X- or Y-axis direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a signal processing device that transmits detection signals with different orientations and draws information based on echo signals on an image configured by arranging pixels in a matrix and displays the information on a display. is there. Specifically, the present invention relates to detection of missing pixels in the signal processing apparatus.

  A signal processing device such as a radar device displays an image obtained by plotting the target on the basis of the position of the own device (antenna) so that the user can intuitively grasp the positional relationship with the target. Here, in the display device, pixels are usually arranged in a grid (matrix), and therefore, when plotting a target on an image, the positions of the pixels are handled in an XY orthogonal coordinate system. . For example, a radar device used in a ship or the like outputs a radio wave at a predetermined cycle (for each predetermined angle) from a rotating antenna, and sequentially plots data obtained from the reflected wave of the radio wave in orthogonal coordinates. The position relationship between the ship and the surrounding target is visually represented on the display.

  However, since the information obtained by the radar device is distributed on a straight line drawn radially from the ship (center) corresponding to the transmission direction of the radio wave, the information becomes more adjacent as the distance from the center increases. The gap between the straight lines increases. Therefore, when information obtained by transmission / reception of radio waves is simply displayed on a display device, pixel omission occurs in a portion away from the center position, which causes the appearance of the display screen to be impaired. For this reason, the radar apparatus may perform interpolation processing by detecting such a pixel missing portion. Patent Document 1 discloses a radar device of this type.

Patent Document 1 discloses a radar device configured as follows. That is, the radar apparatus includes an image memory, a LAST detection unit, a pixel omission detection unit, and an interpolation unit. The image memory stores received data after coordinate conversion from polar coordinates to orthogonal coordinates. The LAST detecting means, each corresponding pixel of an arbitrary sample point i on the previous sweep line data theta _n-1, a plurality of proximity sample points on the previous sweep line data theta _n-1 and the current sweep line data theta _n A match determination is performed. Then, the LAST detection means detects the sample point i as a LAST sample point when the corresponding pixel of the sample point i does not match all the corresponding pixels of the other sample points. The pixel omission means detects whether or not each corresponding pixel of the other sample point matches an adjacent pixel that is in contact with the corresponding pixel of the LAST sample point on the sweep rotation side. The pixel missing detection means detects that there is a pixel missing state in which there is no sample point corresponding to the adjacent pixel when none of the results of the detection matches. Interpolation means interpolates with neighboring pixel data using the adjacent pixel as an interpolated pixel when detecting missing pixels.

JP-A-11-352211

  The pixel missing portion may not be detected properly because its position and size vary depending on parameters such as the rotation speed of the antenna, the period at which the antenna outputs radio waves, and the magnification of the displayed image. In this regard, Patent Document 1 can detect a missing pixel at a location adjacent to a pixel determined to have a LAST determination, but the pixel missing continuously occurs in the rotation direction of the antenna (sweep). There is a possibility that the pixel missing portion cannot be detected.

  In recent years, a display device such as a radar apparatus has become capable of precise image representation due to an increase in the number of pixels. For this reason, pixel omission that may not have occurred on a screen with the conventional number of pixels may occur, and improvement of pixel omission detection accuracy is one of the important solutions.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to transmit detection signals with different orientations and to provide information based on echo signals in an image formed by arranging pixels in a matrix. In the signal processing apparatus that draws the image and displays it on the display, it is desirable to provide a configuration that can reliably detect missing pixels that occur at various positions and sizes.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to the first aspect of the present invention, detection signals are transmitted with different orientations, and information based on echo signals is drawn on an image formed by arranging pixels in a matrix and displayed on a display. The following configuration is provided in the signal processing apparatus. That is, this signal processing apparatus includes a pixel position calculation unit and a pixel omission detection unit. The pixel position calculation unit obtains a position of a pixel corresponding to a point on a sweep line including information based on the echo signal using an XY orthogonal coordinate system. The missing pixel detection unit detects missing pixels based on the position of the pixel of the current sweep line that is the sweep line to be drawn this time and the position of the pixel of the previous sweep line that is the previously processed sweep line. The pixel missing detection unit includes a first pixel that is a pixel on the current sweep line, and a second pixel that is a pixel on the previous sweep line corresponding to the first pixel in the X-axis direction or the Y-axis direction. When there is an intermediate pixel that is one or more pixels sandwiched between the intermediate pixels, the intermediate pixel is determined as a pixel missing portion.

  As a result, pixel omission is detected in the X-axis direction or Y-axis direction, which is the direction in which the pixels are arranged, so that pixel omission can be detected without being affected by signal transmission / reception timing, screen size, etc. Can do.

  In the signal processing device, the pixel missing detection unit has a direction in which the second pixel corresponding to the first pixel is detected in accordance with an angle of the current sweep line or an angle of the previous sweep line. It is preferable to automatically switch the two-pixel detection direction between the X-axis direction and the Y-axis direction.

  Thereby, even when the transmission angle of the detection signal covers a wide range, it is possible to reliably detect missing pixels.

  The signal processing apparatus preferably has the following configuration. That is, the signal processing device includes a storage unit that can store the position of the pixel. The pixel missing detection unit stores the position of the first pixel in the storage unit, and acquires the position of the second pixel by referring to the content of the storage unit at the time of drawing the next sweep line.

  Accordingly, the position of the second pixel on the previous sweep line can be easily obtained by referring to the storage unit. Therefore, it is possible to simplify the process for detecting the missing pixels.

  However, in the signal processing device, the missing pixel detection unit can also acquire the position of the second pixel by calculation using Bresenham's algorithm.

  Accordingly, the position of the second pixel on the previous sweep line can be calculated based only on the coordinates of both ends of the previous sweep line. In addition, the Bresenham algorithm has a low calculation cost, and thus the configuration of the missing pixel detection unit can be easily simplified.

  However, in the signal processing device, the missing pixel detection unit can also obtain the position of the second pixel from information indicating the position of the point on the previous sweep line by calculation using a trigonometric function. .

  Accordingly, the position of the second pixel on the previous sweep line can be calculated based on the information indicating the position of the point of the previous sweep line without storing the position of the pixel on the previous sweep line.

  The signal processing apparatus preferably includes an interpolation processing unit that generates interpolation data for filling a pixel missing portion detected by the pixel missing detection unit.

  Thereby, since the interpolation process can be performed on the missing pixel portion detected without omission, an appropriate image can be displayed on the display device without causing an unupdated pixel.

  In the signal processing device, the interpolation processing unit may use the interpolation data for filling the intermediate pixel based on at least one of the content of the first pixel and the content of the second pixel corresponding to the intermediate pixel. It is preferable to produce them.

  As a result, it becomes easy to perform the pixel omission detection process and the interpolation process in parallel, thereby simplifying the process.

  In the signal processing apparatus, it is preferable that the interpolation processing unit uses the content of the first pixel as the interpolation data for filling the intermediate pixel.

  Thereby, since it is not necessary to hold or refer to the contents of the pixels on the past sweep line, the interpolation process can be simplified and the calculation cost can be reduced.

  According to the 2nd viewpoint of this invention, a radar apparatus provided with the said signal processing apparatus is provided.

  According to the third aspect of the present invention, detection signals are transmitted with different orientations, and information based on echo signals is drawn on an image formed by arranging pixels in a matrix and displayed on a display. In the signal processing apparatus, a pixel missing detection method including the following steps is provided. That is, in the first step, the position of the pixel corresponding to the point on the sweep line including the information based on the echo signal is obtained in the XY orthogonal coordinate system. In the second step, the position of the first pixel, which is a pixel on the sweep line to be drawn this time, and the pixel on the sweep line processed last time and corresponding to the first pixel in the X-axis direction or the Y-axis direction. The position of a certain second pixel is acquired. In the third step, it is determined whether or not there is an intermediate pixel that is one or more pixels so as to be sandwiched between the first pixel and the second pixel whose positions are acquired in the second step. If this is the case, the intermediate pixel is determined to be a pixel missing portion.

  As a result, pixel omission is detected in the X-axis direction or Y-axis direction, which is the direction in which the pixels are arranged, so that pixel omission can be detected without being affected by signal transmission / reception timing, screen size, etc. Can do.

  The signal processing device pixel missing detection method preferably includes a fourth step of performing an interpolation process so as to fill the pixel missing portion detected in the third step.

  Thereby, since the interpolation process can be performed on the missing pixel portion detected without omission, an appropriate image can be displayed on the display device without causing an unupdated pixel.

1 is a block diagram schematically showing the configuration of a radar apparatus according to a first embodiment of the present invention. The figure explaining switching of a pixel missing detection direction. The figure explaining the pixel missing detection in the X-axis direction. The figure explaining the direction of an interpolation process. The flowchart which showed the procedure which performs pixel missing detection and interpolation processing of 1st Embodiment. The figure explaining the drawing algorithm of Bresenham. The flowchart which showed the procedure which performs pixel missing detection and interpolation processing of 2nd Embodiment. The figure explaining the pixel missing detection of 3rd Embodiment. The figure explaining acquisition of the pixel position of the corresponding pixel using a trigonometric function. The figure explaining the pixel missing detection only in the X-axis direction which sets a setting pixel based on the pixel located on the circumference which the front-end | tip of a sweep line draws. The figure explaining the pixel missing detection only in the X-axis direction which sets a setting pixel based on the position of the farthest point pixel of the last sweep line.

  Next, an embodiment of the invention will be described. FIG. 1 is a block diagram schematically showing the configuration of a radar apparatus 10 as a signal processing apparatus according to an embodiment of the present invention.

  A radar apparatus 10 according to the first embodiment shown in FIG. 1 includes a radar antenna 1, a receiving unit 11, an A / D conversion unit 12, a sweep memory 13, an echo intensity calculation unit 14, and a display image memory 15. The drawing address generation unit 16, the pixel missing detection unit 31, the interpolation address generation unit 32, the interpolation content generation unit 33, and the display device 19 are provided as main components.

  The radar antenna 1 can transmit (radiate) a detection signal that is a pulsed radio wave and can receive an echo signal that is a reflected wave of the transmitted radio wave. The radar antenna 1 rotates in a horizontal plane at a predetermined cycle, and the detection signal is repeatedly output while changing the direction at a cycle shorter than the rotation cycle. The angular resolution of the radar apparatus 10 is determined by the number of times the detection signal is transmitted while the radar antenna 1 rotates once.

  The receiving unit 11 detects the reflected wave received by the radar antenna 1, amplifies it, and outputs it to the A / D conversion unit 12. The A / D converter 12 converts the analog signal sent from the receiver 11 into an appropriate digital signal.

  The sweep memory 13 is configured to be able to store received data for one sweep converted into a digital signal by the A / D converter 12. Here, “sweep” refers to a series of operations from transmission of a detection signal to transmission of the next detection signal, and “received data for one sweep” refers to after reception of a detection signal. The data received during the period until the next detection signal is transmitted.

  Since the radio wave has the property of going straight, the received data for one sweep represents the situation on one straight line drawn from the own ship to the direction of the radar antenna 1. When the radar antenna 1 transmits a detection signal in the direction of the straight line, an echo signal from a target close to the ship is received at an early timing, and an echo signal from a far target is received at a late timing. Accordingly, in the received data for one sweep, there is information on whether or not there is a target on the straight line, and information on how far the target is from the ship if there is a target. include. The sweep memory 13 can store received data for one sweep in chronological order.

  The echo intensity calculator 14 reads the received data for one sweep from the sweep memory 13 in time series order and sequentially calculates the amplitude, thereby obtaining the echo intensity at a plurality of points set at equal intervals in the received data. Calculate each. This substantially corresponds to detecting the echo intensity of the reflected wave at each of a plurality of times set with a certain time interval from the time when the detection signal is transmitted from the radar antenna 1.

  The echo intensity data group acquired by the echo intensity calculator 14 (hereinafter, this data group may be referred to as “one sweep echo data group”) is output to the display image memory 15 in time series. And stored sequentially. The drawing address generation unit 16 determines which pixel in the image data of the display image memory 15 stores the echo intensity data group for one sweep.

  The display image memory 15 is configured to be able to store image data (raster data) including a plurality of pixel data for displaying an image on the display 19. An image held in the display image memory 15 (hereinafter referred to as a display image) is expressed by arranging a large number of pixels in a grid pattern (m pixel × n pixel matrix).

  The display image data stored in the display image memory 15 is read at an appropriate timing and displayed on the display 19. The display image memory 15 can store information on echo intensity and the like as the pixel data for each pixel.

  The drawing address generation unit 16 serving as a pixel position calculation unit has a corresponding pixel position on the display image for each of the echo intensity data constituting the one-sweep echo intensity data group obtained by the echo intensity calculation unit 14. (Address) can be obtained. The drawing address generator 16 receives a signal representing the angle θ of the radar antenna 1 when the detection signal is transmitted. The drawing address generator 16 calculates the position of the pixel corresponding to each data of the echo intensity based on the angle θ of the radar antenna 1 and the radar range by the following method.

  That is, when an echo signal is returned when a time t has elapsed since the detection signal was transmitted from the radar antenna 1, during the time t, the radio wave has a distance r between the radar antenna 1 and the target. It was a round trip. Therefore, when a polar coordinate system with the radar antenna 1 as the origin is defined in a horizontal plane, the position of the target corresponding to the echo intensity when the time t has elapsed since the radar antenna 1 transmitted the detection signal is The antenna angle from a predetermined azimuth reference (for example, north) at the time of transmission of the detection signal can be expressed as (r, θ) = (c × t / 2, θ) in the above polar coordinate system. Where c is the speed of light. In the polar coordinate system, the antenna angle θ is determined to be 0 ° when the radar antenna 1 is facing a predetermined direction (north direction), and the direction in which the radar antenna 1 normally rotates is positive. As the predetermined azimuth, a hull coordinate system (bow forward reference) can also be used.

  On the other hand, the display image held in the display image memory 15 is expressed by pixels arranged in a grid (matrix) as described above. In the present embodiment, the position of each pixel in the display image is handled in an XY orthogonal coordinate system in which the upper left corner of the image is the origin, the X axis is the right direction, and the Y axis is the lower direction.

ただし、ｔは、レーダアンテナ１が探知信号を送信した時点からの経過時間である。ｋは、表示器１９の表示領域のサイズ及びレーダレンジ等を考慮して定められる定数であり、θはアンテナ角度である。なお、（Ｘ，Ｙ）は、前記表示用画像を構成する画素の位置（アドレス）を特定するものであるため、Ｘ及びＹの計算結果において、小数点以下の端数は適宜丸められる。 Then, the drawing address generation unit 16 calculates the position of the pixel where the echo intensity information should be stored in the display image. Specifically, the position (X, Y) of this pixel is calculated according to the following equation (1) when the position of the ship (radar antenna 1) in the XY orthogonal coordinate system is (Xs, Ys). The

Here, t is an elapsed time from the time when the radar antenna 1 transmits the detection signal. k is a constant determined in consideration of the size of the display area of the display 19 and the radar range, and θ is the antenna angle. Note that (X, Y) specifies the position (address) of the pixels constituting the display image, and therefore, the fractional part after the decimal point is rounded appropriately in the calculation results of X and Y.

  In the present embodiment, each data constituting an echo intensity data group for one sweep is output from the echo intensity calculator 14 to the display image memory 15 in time series. Then, the drawing address generator 16 sequentially obtains pixel positions (X, Y) corresponding to the respective echo intensity data according to the equation (1) and outputs them to the display image memory 15. Therefore, when processing a group of echo intensity data for one sweep, the drawing address generator 16 repeatedly calculates (X, Y) while θ is constant in the above equation and t is increased from zero. It will be.

  Based on the above calculation, the position (X, Y) of the pixel on the display image corresponding to the echo intensity data group for one sweep in the XY orthogonal coordinate system is based on the position (Xs, Ys) of the ship. It is on a straight line with the angle θ. In the following description, this straight line may be referred to as a “sweep line”.

  Therefore, it can be said that the drawing address generation unit 16 has a function of obtaining the pixel position (X, Y) in the display image corresponding to the point on the straight line (the point on the sweep line). . The drawing address generation unit 16 also functions as a coordinate conversion unit that converts a point (r, θ) on the sweep line expressed in polar coordinates into a pixel position (X, Y) in the XY orthogonal coordinate system. It can be said that it has.

  The pixel position (X, Y) obtained as a result of the calculation by the drawing address generator 16 moves sequentially so as to move away from the ship position (Xs, Ys) as t increases from zero. The movement locus draws one straight line (the sweep line). A group of echo intensity data for one sweep is stored as pixel data in the pixel at the calculated position so as to draw one sweep line in the display image.

  At this time, in a range close to the position of the ship (reference position), a plurality of straight lines pass through one pixel, and a plurality of polar coordinate system data is input to overlap with one pixel. Therefore, in this embodiment, a representative value is determined based on a plurality of data input to the pixel, and this representative value is stored as the pixel data. As a method for determining the representative value, an appropriate method such as a method of using the maximum value among a plurality of data as a representative value or a method of using an average value calculated from a plurality of data as a representative can be employed.

  Further, in the following description, storing the echo intensity information as pixel data in the pixel of the display image stored in the display image memory 15 means “drawing” (or “filling” the pixel). )).

Since the angle θ of the radar antenna 1 is changed every time a detection signal is transmitted, the angle of the sweep line also changes accordingly. In the following description, the sweep line currently processed (to be drawn) is referred to as “current sweep line”, and the corresponding antenna angle is θ _n . The sweep line processed (drawn) immediately before is referred to as “previous sweep line”, and the corresponding antenna angle is θ _n−1 (where θ _n > θ _n−1 ).

  The missing pixel detection unit 31 is for detecting missing pixels present in the image data. The pixel missing detection unit 31 detects a pixel missing generated between the current sweep line and the previous sweep line based on the position of the pixel on the current sweep line and the position of the pixel on the previous sweep line. .

  The pixel omission detection unit 31 includes a corresponding pixel position storage memory (storage unit, second pixel position storage memory) 40 for storing the position of the pixel on the sweep line. The corresponding pixel position storage memory 40 is configured by appropriate hardware such as a RAM. The details of the pixel omission detection by the pixel omission detection unit 31 will be described later.

  The interpolation address generation unit 32 generates an interpolation address indicating a pixel position (address in the display image memory 15) corresponding to a portion determined to be missing by the pixel missing detection unit 31.

  The interpolation content generation unit 33 as an interpolation processing unit generates content (interpolation data) to be filled in the portion determined by the pixel loss detection unit 31 as having a pixel loss. In the present embodiment, the interpolation content generation unit 33 generates the interpolation data based on the output of the echo intensity calculation unit 14. The interpolation data is written into the display image memory 15 based on the interpolation address generated by the interpolation address generator 32, and interpolation is performed thereby.

  The display 19 is a raster scan type display device configured by a CRT or LCD. The image data of the display image read from the display image memory 15 is displayed by the display 19.

  In the radar apparatus 10 having the above configuration, the echo intensity calculation unit 14 obtains an echo intensity data group for one sweep based on the echo signal when the detection signal is transmitted from the radar antenna 1. Further, the drawing address generation unit 16 determines the positions of a plurality of pixels (XY orthogonal) for storing the echo intensity data group for one sweep in the display image memory 15 based on the angle θ of the radar antenna 1 at the time of transmitting the detection signal. Sequentially (in the coordinate system).

  Based on the above results, each data constituting the echo intensity data group is displayed as if the sweep line of the angle θ is drawn in the display image held by the display image memory 15. It is stored in the memory 15 as pixel data. By repeating the above processing while changing the angle θ of the radar antenna 1 little by little, one sweep line based on the position of the ship can be drawn in the image data of the display image memory 15 one by one.

  The image data obtained in this way is read out from the display image memory 15 at an appropriate timing, and is displayed on the display 19 after being appropriately combined with other information. As a result, an image in which a large number of sweep lines are drawn in a radial pattern is displayed on the display 19, and the user can know the positional relationship between the ship and its surrounding targets by viewing the image. As the radar antenna 1 rotates, a new sweep line is repeatedly drawn on the image in the display image memory 15, and as a result, the image displayed on the display 19 is also updated as needed.

  Next, pixel missing detection and interpolation processing of the radar apparatus 10 according to the first embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a diagram illustrating switching of the pixel missing detection direction. FIG. 3 is a diagram for explaining detection of missing pixels in the X-axis direction.

  In the pixel omission detection unit 31 according to the present embodiment, pixel omission is detected in the direction in which pixels are arranged in the display image memory 15 (X-axis direction or Y-axis direction). It is to detect.

Hereinafter, a case where pixel omission is detected in the X-axis direction will be described. That is, there are a plurality of pixels to which information such as echo intensity should be written in order to draw the current sweep line in the display image, but attention is paid to one of these pixels, and this pixel is set as the target pixel (first pixel). The target pixel can be obtained by the drawing address generator 16 based on the antenna angle θ _{n and the} like. Next, a pixel having the same Y coordinate as the pixel of interest (in other words, a pixel corresponding to the pixel of interest in the X-axis direction) is selected from a plurality of pixels in which echo intensity was written when the sweep line was drawn last time. look for. And let the found pixel be a corresponding pixel (2nd pixel).

  Next, the positional relationship between the target pixel and the corresponding pixel is examined. That is, when the target pixel and the corresponding pixel are adjacent or overlap each other in the X-axis direction, it is determined that no pixel omission occurs in the X-axis direction. On the other hand, if there is one or more pixels (intermediate pixels) sandwiched between the target pixel and the corresponding pixel, it is determined that pixel omission has occurred (the intermediate pixel is a pixel omission portion).

  The method described above is a method for detecting missing pixels in the X-axis direction, but the same applies when detecting missing pixels in the Y-axis direction. That is, when the pixel missing detection direction is the Y-axis direction, one pixel is selected from the pixel group to be written to draw the sweep line this time, and is set as the target pixel. In addition, a pixel having the same X coordinate as the pixel of interest (a pixel corresponding to the pixel of interest in the Y-axis direction) is searched from the pixel group written to draw the sweep line last time, and this is used as the corresponding pixel. If one or more pixels sandwiched between the target pixel and the corresponding pixel exist, it is determined that the pixel (intermediate pixel) portion is missing.

Whether the pixel missing detection direction is the X-axis direction or the Y-axis direction is determined according to the angle θ of the radar antenna 1 (the sweep angle that is the angle of the sweep line) θ. As shown in FIG. 2, when the sweep angle θ is in the range from −45 degrees (315 degrees) to 45 degrees and in the range from 135 degrees to 225 degrees, pixel missing is detected in the X-axis direction. Further, when the sweep angle is in the range from 45 degrees to 135 degrees and in the range from 225 degrees to 315 degrees, pixel missing is detected in the Y-axis direction. Note that the determination of the detection direction of the missing pixels is performed by a sweep angle determination unit (not shown). As the sweep angle referred to in this determination, one or both of the current sweep line angle θ _n and the previous sweep line angle θ _n−1 can be used.

Hereinafter, the effect of automatically switching the pixel missing detection direction as described above will be described. That is, the sweep line angle θ _n changes every moment in the range of 0 ° to 360 °. For example, when the sweep line becomes an angle nearly parallel to the Y-axis direction this time (θ _n is set to 0 ° or 180 °). If the pixel missing detection direction is the Y-axis direction, the corresponding pixel corresponding to the target pixel may not be determined. However, in the present embodiment, when the current sweep line is substantially parallel to the Y-axis direction, the pixel missing detection direction is the X-axis direction, so that pixel missing detection can be appropriately performed. Similarly, when the sweep line has an angle nearly parallel to the X-axis direction, pixel missing detection can be appropriately performed by setting the pixel missing detection direction to the Y-axis direction. In the present embodiment, the stored contents of the corresponding pixel position storage memory 40 are referred to in order to acquire the position of the pixel on the previous sweep line.

  That is, the sweep line currently processed (current sweep line) is the previous sweep line in relation to the next processed sweep line. Therefore, the pixel omission detection unit 31 uses the pixel position (X, Y) calculated by the drawing address generation unit 16 when the sweep line is drawn on the display image this time for pixel omission detection at the next sweep line drawing. In order to do this, the corresponding pixel position storage memory 40 is stored.

  The missing pixel detection unit 31 acquires the X coordinate of the corresponding pixel by designating the Y coordinate of the target pixel as an index of the corresponding pixel position storage memory 40 and referring to the stored content. Then, by calculating the difference between the X coordinate of the target pixel and the X coordinate of the corresponding pixel, the presence or absence of an intermediate pixel sandwiched between the two pixels is determined. When the pixel missing detection direction is the Y-axis direction, the corresponding pixel position storage memory 40 is indexed with the X coordinate, and the Y coordinate corresponding to the X coordinate is stored.

  Next, with reference to FIG. 3, an example of detecting pixel omission in the X-axis direction will be specifically described. FIG. 3 conceptually shows a part of the display image, and one square corresponds to one pixel. As shown in FIG. 3, a display image is configured by arranging a plurality of pixels vertically and horizontally, and a pixel in which the previous sweep line is drawn and a pixel in which the current sweep line is drawn are schematically illustrated. Has been.

  As described above, drawing of pixels for forming a sweep line in the display image is sequentially performed from pixels close to the position (Xs, Ys) of the pixel corresponding to the ship. Each time one pixel is drawn, the pixel missing detection is performed with the pixel as the target pixel. In this way, by performing pixel missing detection processing every time one pixel of the current sweep line is drawn, it is possible to detect missing pixels occurring between the current sweep line and the previous sweep line without omission. .

  Hereinafter, the case where the pixel of interest (Xd, Yk) in the image of FIG. When (Xd, Yk) is obtained as a result of the drawing address generation unit 16 calculating the position of the pixel corresponding to the point on the sweep line this time, the pixel omission detection unit 31 determines the Y coordinate of the pixel (target pixel). A value, that is, Yk is designated as an index, and the contents of the corresponding pixel position storage memory 40 are referred to. The corresponding pixel position storage memory 40 stores Xb, which is the X coordinate at the time of drawing the previous sweep line, as the X coordinate value corresponding to Yk. Thereby, the position (Xb, Yk) of the corresponding pixel corresponding to the target pixel can be obtained.

  Next, the missing pixel detection unit 31 calculates the difference between the X coordinates of the target pixel and the corresponding pixel. In this example, since the difference value is 2 or more (Xd−Xb = 2), both pixels are not adjacent and do not overlap (in other words, one or more pixels sandwiched between both pixels) Is present). Accordingly, the pixel missing detection unit 31 determines that there is a pixel missing.

  After the determination of missing pixels, the stored contents of the corresponding pixel position storage memory 40 are updated. That is, the Y coordinate (Yk) of the target pixel is designated as an index, and the stored contents of the corresponding pixel position storage memory 40 corresponding to the Y coordinate are overwritten with the X coordinate (Xd) of the target pixel. As a result, the position of the pixel pointed to by the corresponding pixel position storage memory 40 moves in the X-axis direction as indicated by the white arrow in FIG.

  Next, a case where the pixel of (Xc, Yl) is the target pixel will be described. In this case, when Yl is specified as an index and the stored contents of the corresponding pixel position storage memory 40 are referred to, it can be seen that the X coordinate of the pixel corresponding to the target pixel in the X-axis direction (corresponding pixel) is Xb. When the difference value between the X coordinates of the two pixels is calculated, Xc−Xb = 1. Therefore, the two pixels are adjacent to each other. Accordingly, the pixel missing detection unit 31 determines that there is no pixel missing.

  In the present embodiment, when the pixel omission detection unit 31 determines that there is a pixel omission, the pixel omission detection unit 31 also outputs the number of pixel omissions. The number of missing pixels means the number of pixels (intermediate pixels) sandwiched between the target pixel and the corresponding pixel, and can be obtained by subtracting 1 from the difference value of the X coordinate. If the number of missing pixels is zero, it means that no missing pixels have been detected.

  Next, the interpolation process will be described with reference to FIG. FIG. 4 is a diagram for explaining the direction of the interpolation process.

  In the present embodiment, as shown in FIG. 4, when the pixel missing detection direction is the X-axis direction, interpolation processing is performed in a direction parallel to the X-axis direction, and when the pixel missing detection direction is the Y-axis direction. Interpolation processing is performed in a direction parallel to the Y-axis direction. Thus, the pixel missing detection direction and the interpolation processing direction are always in a parallel relationship. In this specification, the “direction” of the interpolation process refers to a target pixel in which data is written by the interpolation process and a reference pixel whose contents are referred to generate the data, from the reference pixel. The direction toward the target pixel.

  In the interpolation processing of this embodiment, the data of the pixel of interest adjacent to the intermediate pixel (that is, the data of the current sweep line) is used as it is as interpolation data for filling the intermediate pixel determined to be missing. . For example, when the pixel (Xk, Ya) in FIG. 3 is the target pixel, there are five intermediate pixels between the corresponding pixel (Xe, Ya) corresponding in the X-axis direction, and these are detected as missing pixels. . At this time, the pixel data of the target pixel (Xk, Ya) is copied as it is to the five intermediate pixels.

  As a result, as shown in FIG. 4, the interpolation processing is performed so that the direction is parallel to the X axis or the Y axis and is almost opposite to the rotation direction of the radar antenna 1. This interpolation process can be performed at a high speed in parallel with the drawing of the pixel of interest because the content of the pixel of interest is simply copied and drawn to the intermediate pixel. Further, since it is not necessary to refer to the pixel data of the pixel (corresponding pixel) on the previous sweep line for the interpolation processing, the processing speed can be increased.

  Next, with reference to FIG. 5, a processing procedure for pixel missing detection and interpolation data will be described. FIG. 5 is a flowchart illustrating a procedure for performing pixel omission detection and interpolation processing according to the first embodiment.

  First, the pixel position (X, Y) of the pixel to be drawn based on the current sweep line is input to the pixel missing detection unit 31 by one pixel (S101). The pixel dropout detection unit 31 refers to the corresponding pixel position storage memory 40 for the position of the corresponding pixel corresponding to the target pixel in the X-axis direction or the Y-axis direction when the input pixel is the target pixel. get. Then, the difference of the X coordinate value or the difference of the Y coordinate value between the target pixel and the corresponding pixel is calculated (S102).

  The missing pixel detection unit 31 determines whether or not the calculated difference value is 1 or less (S103). If the difference value is 2 or more, the missing pixel detection unit 31 outputs the number of missing pixels to the interpolation address generation unit 32 (S104), and the interpolation address generation unit 32 determines the interpolation address ( That is, an intermediate pixel position between the target pixel and the corresponding pixel is generated (S105). Subsequently, the interpolation content generation unit 33 performs interpolation processing by using the content of the pixel of interest as interpolation data as it is and copying it to the intermediate pixel (S106, S107).

  When the interpolation process ends, the contents of the corresponding pixel position storage memory 40 referred to in S102 are updated with the position of the target pixel (S108), and the process ends. If the difference value is equal to or smaller than 1 in the determination in S103, the corresponding pixel position storage memory 40 is updated without performing the processing in S104 to S107, and then this processing ends.

  The above processing is repeated every time the position (X, Y) of the pixel to be drawn for forming the sweep line in the image this time is input by one pixel from the drawing address generating unit 16, so that The resulting pixel omissions are detected sequentially, and interpolation processing can be performed without omission.

  As described above, the radar apparatus 10 according to the first embodiment is configured as follows. That is, the radar apparatus 10 includes a drawing address generation unit 16 and a pixel missing detection unit 31. The drawing address generator 16 obtains the position of the pixel corresponding to the point on the sweep line using the XY orthogonal coordinate system. The missing pixel detection unit 31 detects missing pixels based on the pixel position of the current sweep line and the pixel position of the previous sweep line. The missing pixel detection unit 31 is sandwiched between the target pixel that is the pixel on the current sweep line and the corresponding pixel that is the pixel on the previous sweep line corresponding to the target pixel in the X-axis direction or the Y-axis direction. When there is an intermediate pixel that is one or more pixels, the intermediate pixel portion is determined to be a missing pixel portion.

  As a result, pixel omission is detected in the X-axis direction or Y-axis direction, which is the direction in which the pixels are arranged, so that pixel omission can be detected without being affected by signal transmission / reception timing, image size, etc. Can do.

  Further, in the radar apparatus 10 according to the present embodiment, the direction in which pixel omission is detected is automatically switched according to the angle of the sweep line.

  Thus, even when the detection signal is transmitted all around 360 degrees, pixel omission can be reliably detected over the entire angle range of the sweep line, and interpolation processing described later can be performed without omission.

  Further, the radar apparatus 10 of the present embodiment includes a corresponding pixel position storage memory 40 that can store the position of the pixel. The pixel missing detection unit 31 stores the position of the target pixel in the corresponding pixel position storage memory 40, and acquires the position of the corresponding pixel by referring to the contents of the corresponding pixel position storage memory 40 at the time of drawing the next sweep line. .

  Thereby, the position of the corresponding pixel on the previous sweep line can be easily obtained by referring to the corresponding pixel position storage memory 40. Therefore, it is possible to simplify the process for detecting the missing pixels.

  Further, the radar apparatus 10 according to the present embodiment includes an interpolation content generation unit 33 for filling a pixel missing portion detected by the pixel missing detection unit 31.

  Thereby, since the interpolation process can be performed on the missing pixel portion detected without omission, an appropriate image can be displayed on the display device 19 without causing an unupdated pixel. This makes it possible to reliably update all the pixels while the radar antenna 1 (sweep line) rotates once.

  Further, in the radar apparatus 10 of the present embodiment, the interpolation content generation unit 33 generates interpolation data for filling the intermediate pixel based on the content of the target pixel corresponding to the intermediate pixel.

  Thereby, the pixel missing detection process and the interpolation process can be performed in parallel, and the process can be simplified as a whole.

  In the radar apparatus 10 of the present embodiment, the interpolation content generation unit 33 uses the content of the pixel of interest corresponding to the intermediate pixel as interpolation data for filling the intermediate pixel.

  Thereby, since it is not necessary to hold or refer to the contents of the pixels on the past sweep line, the interpolation process can be simplified and the calculation cost can be reduced.

  Next, pixel missing detection processing according to the second embodiment will be described with reference to FIGS. 6 and 7. FIG. 6 is a diagram for explaining Bresenham's drawing algorithm. FIG. 7 is a flowchart illustrating a procedure for performing pixel omission detection and interpolation processing according to the second embodiment. Note that, in the configuration of the second embodiment, the processes other than the processing for calculating and calculating the positions of the pixels on the current sweep line and the previous sweep line are the same as those in the first embodiment, and thus the description thereof is omitted.

  In the radar apparatus 10 of the present embodiment, the drawing address generation unit 16 calculates the position (address) of the pixel on the current sweep line using the Bresenham drawing algorithm instead of using the equation (1). It is configured. Similarly, the pixel omission detection unit 31 is also configured to calculate the pixel position (address) on the previous sweep line using Bresenham's drawing algorithm.

ただし、この式には除算が含まれており、計算負荷が大きい。この点、前記Ｂｒｅｓｅｎｈａｍのアルゴリズムは、画素がマトリクス状に配置された画像に対し、少ない計算量で効率的に直線を描画するために用いられる。 First, a general Bresenham drawing algorithm will be described. As shown in FIG. 6A, consider a case in which a straight line connecting the start point (x ₁ , y ₁ ) to the end point (x ₂ , y ₂ ) is drawn in the XY coordinate system. The function representing this straight line can be described as the following equation (2).

However, this formula includes division, and the calculation load is heavy. In this respect, the Bresenham algorithm is used to efficiently draw a straight line with a small amount of calculation for an image in which pixels are arranged in a matrix.

In Bresenham's drawing algorithm, it is first determined whether the pixel position is to be calculated based on the X-axis direction or the Y-axis direction. In this determination, between the two given points, the distance in the X-axis direction (Δx = x ₂ −x ₁ ) and the distance in the Y-axis direction (Δy = y ₂ −y ₁ ) are examined. The long distance should be used as a reference. For example, if the coordinates of two points are in a relationship of Δy> Δx, the pixel position is calculated with reference to the Y-axis direction. In this case, the Y coordinate value is incremented by ₁ from y ₁ to y ₂ , and in the process, the X coordinate value is incremented by 1 at an appropriate timing from the initial value x ₁ , and the Y coordinate value becomes y the value of X-coordinate is set to be a x ₂ when a _two. As a result, the position of the pixel specified by the X coordinate and the Y coordinate moves from the (x ₁ , y ₁ ) one by one in the Y axis direction with or without moving by 1 in the X axis direction, ( x ₂ , y ₂ ) is reached. Then, the movement trajectory draws a target straight line.

  More specifically, it can be considered as follows. That is, if the Y coordinate is continuously incremented by 1 without changing the X coordinate at all, the drawing result becomes a straight line parallel to the Y axis. Therefore, to draw an oblique straight line as shown in FIG. 6A, it is necessary to increase the X coordinate by 1 at an appropriate timing in the process of increasing the Y coordinate. Therefore, in this algorithm, a parameter called an error value eX in the X-axis direction is introduced in order to determine the timing for increasing the X coordinate.

The value of the error value eX is proportional to the deviation in the X-axis direction that occurs between the current pixel position and the ideal straight line to be drawn. The initial value of the error value eX is set to zero, but when the Y coordinate is increased by 1 without changing the X coordinate of the pixel, (x ₂ −x ₁ ) is added every time. When the error value eX exceeds (y ₂ −y ₁ ), the X coordinate is incremented by 1 and (y ₂ −y ₁ ) is subtracted from eX.

The above processing is repeated until the Y coordinate value is incremented by ₁ from y ₁ until it reaches y ₂ , thereby obtaining the position of the pixel to which data is to be written in order to draw the target straight line on the image. Further, the value of the error value eX is always an integer, and processing such as division is not necessary, so that the amount of calculation can be reduced.

  In this embodiment, the current sweep line can be drawn at high speed by setting the start point of the straight line as the position (Xs, Ys) of the radar antenna 1 and the end point as the farthest point on the current sweep line. Similarly, the position of the pixel on the previous sweep line is calculated by setting the start point of the straight line as the position (Xs, Ys) of the radar antenna 1 and the end point as the farthest point on the previous sweep line. Can do. In the current sweep line, the position of the end point is appropriately calculated according to the above equation (1). Further, the calculated position of the end point of the current sweep line is stored in an appropriate storage unit, and is used as the position of the end point of the previous sweep line when drawing the next sweep line.

  Next, the process of drawing the sweep line this time using the Bresenham drawing algorithm will be described in detail. That is, when drawing a sweep line using the Bresenham drawing algorithm, if a group of echo intensity data for one sweep is simply stored in the pixel data in association with the Y coordinate (or X coordinate), the sweep angle θ The information of the echo intensity is written in the display image by being stretched or contracted in the sweep line direction, thereby causing image distortion. Therefore, in the present embodiment, when drawing a sweep line based on a group of echo intensity data for one sweep, the Bresenham drawing algorithm is extended and used as follows.

That is, a group of echo intensity data for one sweep is composed of R pieces of data, and each echo intensity data can be read from an appropriate storage unit by specifying an index from No. 0 to (R-1). And Also, r is a variable (access variable) for accessing the index of the echo intensity data group. In this case, in this embodiment, as shown in FIG. 6B, in the virtual image in which the pixels are arranged in a matrix, the r axis and the Y axis are determined to be orthogonal to each other, and (0, y The position (r, Y) of the pixel to which data is to be written in order to draw a straight line from ₁ ) to (R-1, y ₂ ) is obtained by Bresenham's drawing algorithm as described above. At this time, the calculation of the pixel position is performed with reference to the r-axis direction.

  The calculation result (r, Y) thus obtained indicates the correspondence between the index of the echo intensity data and the Y coordinate of the pixel to which the echo intensity data is to be written. If the Y coordinate is repeatedly calculated by the above method while increasing the access variable r by 1 from 0, the Y coordinate increases by 1 at an appropriate timing. At this timing, the X coordinate corresponding to the Y coordinate is obtained by the aforementioned drawing algorithm, and the echo intensity data designated by the r-th index is written into the obtained pixel (X, Y). By repeating the above processing while increasing r by 1 from 0 to R-1, echo intensity data can be stored in the pixel at the correct position, and image distortion can be prevented.

However, the above example is a case where the pixel position is calculated based on the Y-axis direction when the pixel position of the sweep line is acquired in the XY coordinate system. When calculating the pixel position based on the X-axis direction, an orthogonal coordinate system with the r-axis and the X-axis is defined in the virtual image and a straight line is drawn from (0, x ₁ ) to (R-1, x ₂ ). become.

  The extended Bresenham drawing algorithm is used when the drawing address generator 16 obtains a point on the current sweep line. On the other hand, the pixel missing detection unit 31 only needs to obtain the position of the corresponding pixel corresponding to the pixel of interest, and therefore, a normal Bresenham drawing algorithm that is not expanded may be used. In other words, when detecting missing pixels in the X-axis direction, it is sufficient to obtain the corresponding X coordinate of the pixel on the previous sweep line by the normal Bresenham drawing algorithm at the timing when the Y coordinate of the target coordinate changes. is there.

  Next, with reference to FIG. 7, a procedure for performing pixel omission detection and interpolation processing according to the second embodiment will be described. First, the drawing address generation unit 16 generates a position (address) indicating a pixel at a point on the current sweep line and inputs the position (address) to the pixel omission detection unit 31 (S201). In the present embodiment, as described above, the position of the point on the current sweep line is calculated using the expanded Bresenham drawing algorithm.

  The pixel dropout detection unit 31 reads the position of the pixel farthest from the position of the ship on the previous sweep line from an appropriate storage unit. Then, the pixel dropout detection unit 31 uses the pixel input in S201 as the pixel of interest, and calculates the position of the pixel (corresponding pixel) on the previous sweep line corresponding to this in the X-axis direction using the Bresenham drawing algorithm. (S202). Subsequent processing (S203 to S207) is the same as that of the first embodiment (S103 to S107), and thus description thereof is omitted. In this embodiment, since the position of the corresponding pixel is sequentially obtained by calculation, the pixel position storage memory update process (S108) performed in the first embodiment is omitted.

  The process described above is repeated every time one pixel position is input from the pixel (Xs, Ys) at the position of the ship to the pixel farthest from the ship on the current sweep line. As a result, the drawing of the sweep line this time and the interpolation process can be performed in parallel at high speed. When the processing of the last pixel (that is, the pixel farthest from the ship) is completed, the coordinates of the pixel are stored in an appropriate storage unit, and this content is referred to in the processing of S202 at the next drawing of the sweep line. Is done.

  As described above, in the present embodiment, the position of the corresponding pixel on the previous sweep line is calculated using Bresenham's drawing algorithm, and pixel omission is detected based on this. In this embodiment, if only the position of the pixel farthest from the ship is stored on the sweep line, the position of the corresponding pixel can be calculated based on the stored position, so that the corresponding pixel position storage memory 40 sets the pixel address for each pixel. Compared to the configuration of the first embodiment stored in the storage area, it is advantageous from the viewpoint of efficient use of the storage area.

  As described above, in the radar apparatus 10 according to the second embodiment, the pixel dropout detection unit 31 acquires the position of the corresponding pixel by calculation using the Bresenham algorithm.

  Thereby, the position of the corresponding pixel on the previous sweep line can be calculated based on the position of the pixel of the own ship and the position of the pixel farthest from the own ship in the previous sweep line. In addition, the Bresenham algorithm has a low calculation cost, and thus the configuration of the pixel missing detection unit 31 can be easily simplified.

  Next, with reference to FIGS. 8 and 9, a pixel omission detection unit 31 according to the third embodiment that detects corresponding pixels using information in the polar coordinate system will be described. FIG. 8 is a diagram for explaining pixel omission detection according to the third embodiment. FIG. 9 is a diagram illustrating the acquisition of the pixel position of the corresponding pixel using a trigonometric function. Note that the third embodiment is the same as the first embodiment except for the configuration related to the process of acquiring the corresponding pixel position of the previous sweep line, and thus the description may be omitted.

  FIG. 8 and FIG. 9 show detection of corresponding pixels when the direction of detecting missing pixels is the X-axis direction. As shown in FIG. 8, the corresponding pixel corresponding to the target pixel on the current sweep line is a pixel corresponding to the target pixel in the direction in which pixel omission is detected (X-axis direction), and is on the previous sweep line, The Y coordinate value is the same pixel as the Y coordinate value of the target pixel.

  By the way, as described in the first embodiment, the sweep line converts the polar coordinate system information of a plurality of sample data (echo intensity data group for one sweep) indicating the echo intensity into the XY orthogonal coordinate system. It is drawn with. Therefore, if the sample data in which the Y coordinate value when converted to the XY Cartesian coordinate system is the same as the Y coordinate value of the pixel of interest can be identified among the plurality of sample data on the previous sweep line, the sample data The value of the X coordinate can be obtained from the data, and the pixel position of the corresponding pixel is determined. A method for calculating the pixel position of the corresponding pixel will be specifically described below.

The missing pixel detection unit of the radar apparatus 10 of the third embodiment is configured to calculate the pixel position of the corresponding pixel using the polar coordinate system data of the sample data that is a point on the previous sweep line indicating the echo intensity. Has been. Further, the missing pixel detection unit 31 of the third embodiment is configured to include a previous sweep angle storage unit for storing the sweep angle θ _n−1 of the previous sweep line.

The sweep angle is updated at an appropriate timing as drawing of the current sweep line is completed. More specifically, the angle θ of the current sweep line when drawing is completed is used as the previous sweep line angle θ _n−1 in order to detect missing pixels when drawing the next sweep line. Is remembered.

  Hereinafter, the calculation process of the pixel position of the corresponding pixel of the pixel omission detection unit 31 will be described. First, as shown in FIG. 9, the pixel missing detection unit 31 obtains a length Δr in the distance direction between adjacent sample data on the previous sweep line. Δr can be obtained from the difference Δt in detection time between adjacent sample data and the speed of light c. As Δr, a value set in advance according to the time interval for detecting the echo intensity of the reflected wave can be used.

Next, by performing a calculation using a trigonometric function based on Δr and the sweep angle θ _n−1 , the amount of change in X between sample data ΔX = Δr sin θ _n−1 and the amount of change in Y ΔY = Δr cos θ _n− seek _1.

  Subsequently, variables Xt and Yt representing the X coordinate and Y coordinate are initialized to the coordinates of the position of the ship (that is, Xt = Xs, Yt = Ys). Then, ΔX is added to the variable Xt, and ΔY is subtracted from Yt. Next, it is checked whether or not the Yt value after subtraction matches the Y coordinate value of the target pixel. If they match, the coordinate (Xt, Yt) is set as the pixel position of the corresponding pixel. If not, the addition of Xt and the subtraction of Yt are repeated until the Yt value matches the Y coordinate value of the target pixel.

  In this configuration, it is assumed that after the initialization process (Xt = Xs, Yt = Ys), ΔY is subtracted n times from Yt, and as a result, the value of Yt matches the value of the Y coordinate of the target pixel. In this case, since the value obtained by adding ΔX n times to the initial value of Xt is the value of the X coordinate, the pixel position of the corresponding pixel is (Xs + n × ΔX, Ys−n × ΔY). It should be noted that even when pixel omission detection is performed in the Y-axis direction, it is possible to calculate the pixel position of the corresponding pixel by performing the same processing.

  As described above, in the radar apparatus 10 according to the third embodiment, the pixel dropout detecting unit 31 calculates the corresponding pixel by calculation using a trigonometric function from information on the polar coordinate system indicating the position of the point on the previous sweep line. Get the position.

  Accordingly, the position of the corresponding pixel on the previous sweep line can be calculated based on the information on the polar coordinate system indicating the position of the point on the previous sweep line without storing the position of the pixel on the previous sweep line.

Note that the configuration for calculating the pixel position of the corresponding pixel by a trigonometric function using the information (r, θ) of the polar coordinate system shown in the third embodiment can be changed as follows. That is, first, a variable r indicating the distance from the ship is initialized with 0 (r = 0). Then, Δr (distance between adjacent sample data) is added to r, and the trigonometric function is used by using the position (Xs, Ys) of the ship, the angle θ _n-1 and r (value obtained by adding Δr). X coordinate and Y coordinate are obtained (X = Xs + rsin θ _n−1 , Y = Ys−r cos θ _n−1 ). The addition of the variable r is repeated until the Y coordinate value matches the Y coordinate value of the target pixel. That is, every time Δr is added to r, the X coordinate and the Y coordinate are calculated, and the calculated Y coordinate value is compared with the Y coordinate value of the target pixel. When the calculated Y coordinate value matches the Y coordinate value of the target pixel, the X coordinate value and Y coordinate value at that time are set as the pixel position of the corresponding pixel. It should be noted that even when pixel omission detection is performed in the Y-axis direction, it is possible to calculate the pixel position of the corresponding pixel by performing the same processing.

  Although the embodiment of the present invention has been described above, the above configuration can be further modified as follows.

  The generation method of the interpolation data is not limited to the above-described embodiment, and an appropriate method can be adopted in consideration of image quality, processing efficiency, and the like. For example, the contents of the corresponding pixel instead of the target pixel can be copied and filled in the intermediate pixel as it is, or the intermediate pixel can be filled with data obtained by linear interpolation between the target pixel and the corresponding pixel. In addition to linear interpolation, an appropriate method such as parabolic interpolation, cubic interpolation, or spline interpolation may be employed as a method for generating interpolation data.

  Furthermore, the direction of the interpolation process can be inclined with respect to the detection direction of the missing pixels. Further, the interpolation processing is not limited to a method performed in one direction. For example, the interpolation process can be performed so as to extend from the target pixel or the corresponding pixel to the peripheral pixel (a region including a plurality of pixels centered on the target pixel or the corresponding pixel). As described above, as a procedure for processing the interpolation data in the missing pixel portion, an appropriate method can be adopted depending on circumstances.

  The radar apparatus 10 of the above embodiment is configured to switch the pixel missing detection direction according to the angle θ of the radar antenna 1 (see FIG. 2), but without switching the pixel missing detection direction, It is possible to change to a configuration that detects pixel omission only in the Y-axis direction. In this configuration, as described in the description with reference to FIG. 2, when pixel missing detection is performed in the X-axis direction (or Y-axis direction), the sweep line angle is X-axis (pixel missing detection direction is Y-axis). In the state of approaching the Y axis), there is a high possibility that the target pixel cannot be detected. Therefore, in the radar apparatus 10 that does not switch the pixel missing detection direction, it is preferable to separately process pixel missing in a range in which the target pixel cannot be detected.

  Next, with reference to FIG. 10, a modified example in which pixel omission detection is performed only in the X-axis direction and pixel omission in a range where the target pixel cannot be detected will be separately processed. FIG. 10 is a diagram for explaining pixel omission detection only in the X-axis direction in which a setting pixel serving as a target pixel is set based on a pixel located on the circumference drawn by the tip of the sweep line. Since the configuration other than the pixel omission detection and interpolation processing is the same as the configuration of the above embodiment, detailed description thereof will be omitted.

  The modification of FIG. 10 performs pixel omission detection by virtually setting a target pixel in a range where the target pixel cannot be detected. In the following description, a pixel that is virtually set as the target pixel in this way may be referred to as a “set pixel”.

  As shown in FIG. 10, when the Y coordinate is (Ye), the target pixel (Xf, Ye) can be detected on the sweep line this time, but the Y coordinate is (Yd), (Yc), (Yb). ), The target pixel on the sweep line cannot be detected. Therefore, consider a circle centered on the ship position (Xs, Ys) and having a radius of the length of the sweep line, and a pixel located on this circumference is a virtual target pixel (set pixel).

  As shown in FIG. 10, in the range where the target pixel cannot be detected, the pixels whose pixel addresses are (Xk, Yd), (Xk, Yc), and (Xj, Yb) are set pixels. Then, corresponding to the set pixel in the X-axis direction, the pixel existing on the previous sweep line is set as the corresponding pixel, and pixel missing detection similar to that in the above embodiment is performed. Note that the white arrow in FIG. 10 has a different meaning from the white arrow in FIG. 3 and conceptually shows processing for determining a corresponding pixel corresponding to the target pixel (and the set pixel).

  For example, in the example of FIG. 10, when the set pixel is (Xk, Yd), the corresponding pixel is (Xc, Yd), and pixel omission detection is performed based on this. The pixel omission detection process is the same as that described in the above embodiment except that the pixel of interest is a set pixel, and thus the description thereof is omitted.

  Since the set pixel set by this method is on the circumference having the radius of the sweep line as a radius, it is one of the neighboring pixels of the outermost pixel drawn by one sweep line. Therefore, by performing pixel omission detection using the set pixel set in this way as a target pixel, it is possible to detect without omission the pixel omission portion existing inside the circle drawn by the sweep line.

  Interpolation data generated by the interpolation content generation unit 33 is written at a location where a missing pixel is detected. As a method for generating this interpolation data, an appropriate method such as determining the contents of the interpolation data based on the data of the surrounding pixels of the set pixel or the corresponding pixel, the data of the pixels in the azimuth direction (diagonal), etc. should be adopted. Can do.

  Further, the method for setting the setting pixels is not limited to the above modification. Next, with reference to FIG. 11, another modified example in which the set pixel is set with reference to the pixel at the farthest position on the previous sweep line and the missing pixel detection is performed only in the X-axis direction will be described. FIG. 11 is a diagram for explaining detection of missing pixels only in the X-axis direction by setting a set pixel based on the position of the farthest point pixel on the previous sweep line. This modification is the same as the modification described above except that the setting method of the setting pixels is different.

  In this modification, as shown in FIG. 11, the farthest point pixel which is a pixel on the previous sweep line and which is the farthest from the position (Xs, Ys) of the radar antenna 1 is detected. In FIG. 11, the farthest point pixel of the previous sweep line is a pixel whose pixel address is (Xj, Ya). Next, a pixel that is on the sweep line this time and has the same X coordinate as the farthest point pixel (a pixel corresponding to the farthest point pixel in the Y-axis direction) is searched, and this pixel and the farthest point pixel Pixels existing between are set as set pixels (virtual attention pixels). In this modified example, as shown in FIG. 11, in the range where the target pixel cannot be detected, pixels with pixel addresses (Xj, Yd), (Xj, Yc), and (Xj, Yb) are set pixels. Then, corresponding pixels are set based on the set pixels, and pixel missing detection processing and interpolation processing are performed as in the above embodiment.

  As described above, even in a configuration in which pixel missing detection is detected only in the X-axis direction without switching the pixel missing detection direction as shown in FIG. 2, by performing special processing within a range in which the target pixel cannot be detected, Can be reliably detected and the interpolation process can be appropriately performed. It should be noted that even when pixel omission is detected only in the Y-axis direction, it is possible to detect pixel omission without omission by performing the same processing.

  Further, in addition to the configuration of the above embodiment, an interpolation sweep line can be drawn. The interpolated sweep line is a sweep line generated so as to interpolate between sweep lines obtained based on actual data. In this case, the previous sweep line and the current sweep line may be sweep lines based on actual data or may be interpolated sweep lines. However, it can be said that the configuration of the above-described embodiment that can detect and interpolate pixel omission without omission is more suitable for a configuration that does not generate an interpolation sweep line (or a configuration that has fewer) than the conventional configuration.

  Moreover, in the said embodiment, although the corresponding | compatible pixel position memory 40 is employ | adopted as a memory | storage part, the structure of a memory | storage part can be changed suitably. For example, the pixel position of the corresponding pixel (second pixel) may be stored by a plurality of counters. When the size of the display image is m pixels × n pixels, it is sufficient to prepare the counters used in this configuration for the larger value of m and n. For example, when the pixel omission detection direction is the X-axis direction, an index of the Y coordinate is attached to the plurality of pixel position storage memories, and the X coordinate corresponding to the Y coordinate is stored in each pixel position storage memory. The Therefore, even in this configuration, when a missing pixel is detected, the value of the X coordinate of the pixel of the sweep line (previous sweep line) corresponding to the Y coordinate is easily referred to by specifying the Y coordinate and referring to the contents of the counter. Can be acquired.

  The configuration of the radar apparatus 10 according to the above embodiment can be applied to devices other than marine equipment.

  In the above embodiment, the example in which the present invention is applied to the radar apparatus has been described, but the present invention is not limited to the radar apparatus. That is, the present invention is applicable to any signal processing apparatus configured to transmit detection signals with different orientations and display information based on echo signals on a display device in an image formed by arranging pixels in a matrix. Can be applied. An example of this type of signal processing device is a scanning sonar device.

10 Radar equipment (signal processing equipment)
16 Drawing address generator (pixel position calculator)
19 Display 31 Missing Pixel Detection Unit 33 Interpolation Content Generation Unit (Interpolation Processing Unit)
40 Corresponding pixel position storage memory (storage unit)

Claims (11)

In a signal processing device that transmits detection signals with different orientations and draws information based on echo signals on an image configured by arranging pixels in a matrix and displays the information on a display device.
A pixel position calculation unit for obtaining a position of a pixel corresponding to a point on a sweep line including information based on the echo signal in an XY orthogonal coordinate system;
A pixel omission detection unit that detects pixel omission based on the position of the pixel of the current sweep line that is the sweep line to be drawn this time and the position of the pixel of the previous sweep line that is the previously processed sweep line;
An interpolation processing unit for generating interpolation data for filling a pixel missing portion detected by the pixel missing detection unit;
With
The pixel missing detection unit includes a first pixel that is a pixel on the current sweep line, a second pixel that is a pixel on the previous sweep line corresponding to the first pixel in the X-axis direction or the Y-axis direction, A signal processing device, wherein when there is an intermediate pixel that is one or more pixels sandwiched between two pixels, the intermediate pixel is determined to be a pixel missing portion. The signal processing device according to claim 1,
The pixel omission detection unit sets a second pixel detection direction, which is a direction for detecting the second pixel corresponding to the first pixel, according to the angle of the current sweep line or the angle of the previous sweep line, as an X axis. A signal processing device that automatically switches between a direction and a Y-axis direction. The signal processing device according to claim 1 or 2,
A storage unit capable of storing the pixel position;
The missing pixel detection unit stores the position of the first pixel in the storage unit, and obtains the position of the second pixel by referring to the content of the storage unit at the time of drawing the next sweep line. A characteristic signal processing apparatus. The signal processing device according to claim 1 or 2,
The signal processing apparatus, wherein the missing pixel detection unit acquires the position of the second pixel by calculation using a Bresenham algorithm. The signal processing device according to claim 1 or 2,
The signal processing device is characterized in that the pixel missing detection unit acquires the position of the second pixel from information indicating the position of the point on the previous sweep line by calculation using a trigonometric function. A signal processing device according to any one of claims 1 to 5,
A signal processing apparatus comprising: an interpolation processing unit that generates interpolation data for filling a pixel missing portion detected by the pixel missing detection unit. The signal processing device according to claim 6,
The interpolation processing unit generates the interpolation data for filling the intermediate pixel based on at least one of the content of the first pixel and the content of the second pixel corresponding to the intermediate pixel. Signal processing device. The signal processing device according to claim 7,
The signal processing apparatus, wherein the interpolation processing unit uses the content of the first pixel as the interpolation data for filling the intermediate pixel.   A radar apparatus comprising the signal processing apparatus according to claim 1. In a method for detecting missing pixels of a signal processing apparatus that transmits detection signals with different orientations and draws information based on echo signals on an image configured by arranging pixels in a matrix and displays the information on a display.
A first step of obtaining a position of a pixel corresponding to a point on a sweep line including information based on the echo signal in an XY orthogonal coordinate system;
The position of the first pixel that is the pixel on the sweep line to be drawn this time, and the second pixel that is the pixel on the sweep line that was processed last time and that corresponds to the first pixel in the X-axis direction or the Y-axis direction. A second step of obtaining a position;
It is checked whether or not there is an intermediate pixel that is one or more pixels so as to be sandwiched between the first pixel and the second pixel whose positions are acquired in the second step. A third step of determining the intermediate pixel as a missing pixel portion;
A pixel omission detection method for a signal processing device, comprising: It is a pixel missing detection method of the signal processing device according to claim 10,
A pixel missing detection method for a signal processing apparatus, comprising: a fourth step of performing an interpolation process so as to fill a pixel missing portion detected in the third step.

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