JPH0549925B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a horizon detection device used in an image processing device of an automatic navigation system for a ship or the like.

[Prior Art] A general configuration of a horizon detection device used in an image processing device of an automatic navigation system for a ship or the like is shown in FIG. In the figure, 1 is an imaging device, 2 is a video signal, 3 is an A/D converter, 4 is digital image data, 5 is a frame memory, 6 is read digital image data, 7 is a differential circuit, and 8 is a differential image 9 is a peripheral distribution calculation circuit, 10 is peripheral distribution data, 11 is a moving difference calculation circuit, 12 is moving difference data, 13 is a zero cross detection circuit, and 14 is a detection result.

In the above configuration, an image of the outside world is captured by the imaging device 1, and an analog video signal 2 is captured by the imaging device 1.
is obtained. This signal is converted into digital image data 4 by an A/D converter 3, and temporarily stored in a frame memory 5 in units of one screen. frame memory 5
The digital image data 6 read out is differentiated by a differentiating circuit 7. This converts the image data to F(x,
y), and the X and Y coordinates are the horizontal and vertical directions of the image, respectively, and the F(x, y) value is p-beat data for luminance. The differentiation circuit 7 performs differentiation in the Y direction, DFY( x,y)=F(x,y+1)−F(x,y)
…(1) Perform the following calculation. This is the output from the differentiator circuit 7.
For DFY(x,y) (differential image data) 8, the marginal distribution calculation circuit 9 performs the following calculation: SDFY(y)= ^〓x |DFY(x,y)|...(2). For SDFY (x, y) (marginal distribution data) 10, which is the output from the marginal distribution calculation circuit 9, the moving difference calculation circuit 11 calculates MD (y)=1/l・_y+l-1 〓 ^y SDFY( y)-1/l・_y-1 〓 ^yl SDFY(y)...(3) (where l: movement length). The maximum peak point of MD(y) (moving difference data) 12, which is the output from the moving difference calculation circuit 11, is found by the zero cross detection circuit 13, and the first zero cross is detected in the direction of increasing Y address starting from that Y coordinate. A point is detected and its value is output as the address of the horizontal line.

[Problems to be Solved by the Invention] However, with the horizon detection device having the above configuration, when there is a large temperature difference between the sea and the sky, as shown in the peripheral distribution in Figure 6a, the horizon can be detected relatively easily, but when there are many sea cradle (waves) as shown in Figure 6(b), or when the temperature difference is small and there are few sea cradle (waves) as shown in Figure 6(c), as a result, There was a high possibility of false detection in cases where remarkable horizontal line features did not appear in the peripheral distribution. Furthermore, even if the horizontal line feature is significant as shown in FIG. 6b, it is possible that the zero-cross detection may be erroneously detected. Figure 7 shows the state of false detection. In Figure 7a, the marginal distribution is pulse-like, so there is a zero-crossing point of the movement difference, but as shown in Figure 7b, the marginal distribution is step-like. , there is no zero-crossing point in the moving difference.

The present invention was made in view of the above-mentioned circumstances, and it is possible to detect the horizon not only when there is a large temperature difference between the sea and the sky, but also when there are many sea crags. To provide a horizon line detection device capable of improving the probability of detecting a horizon line by disabling detection in order to avoid false detection when the horizontal line is small and there are few sea clutters, and as a result, no remarkable horizon feature appears in the peripheral distribution. purpose.

[Means for Solving the Problems] The present invention digitizes an analog video signal captured by an imaging device using an A/D converter, temporarily stores it in a frame memory, and then performs image processing to extract data from the video signal. In a horizontal line detection device that detects a horizontal line, digital image data read from the frame memory is differentiated by a differentiating circuit, a marginal distribution is determined by a marginal distribution calculation circuit using the obtained differential image data, and a moving difference of this marginal distribution is calculated. The moving difference calculation circuit calculates the point, and the zero-crossing detection circuit detects the zero-crossing point that becomes a horizontal line candidate from the moving difference waveform, while the peak detection circuit detects the maximum peak point that becomes a horizontal line candidate from the moving difference waveform, and the zero-crossing detection circuit detects the maximum peak point that becomes a horizontal line candidate from the moving difference waveform. A statistical calculation circuit calculates a feature amount from the zero crossing point outputted by the above, the maximum peak point outputted from the peak detection circuit, and the marginal distribution outputted from the marginal distribution calculation circuit, and the horizontal line candidate outputted from the zero crossing detection circuit and the A comparative evaluation circuit determines whether to select one or none of the horizontal line candidates output from the peak detection circuit.

[Operation] With the above configuration, two horizontal line candidates, the zero crossing point and the peak point, are detected from the moving difference data, and by using the feature quantity of the peripheral distribution as the selection condition, the size of the temperature difference and the sea clutter can be determined. presence or absence, etc.
It is possible to stably detect the horizon even when weather conditions change, and when the weather is bad and it is difficult to detect the horizon, it is determined that the horizon cannot be detected, reducing false detections.

[Example] An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows the circuit configuration. 21 is an imaging device that performs imaging, 22 is an analog video signal that is the output of the imaging device 21, and 23 is an analog video signal that is the output of the imaging device 21. 24 is an A/D converter that digitizes the
digital image data that is the output of the D converter 23;
25 is a frame memory that stores digital image data 24 in units of one screen; 26 is a frame memory 2;
Digital image data read out from 5, 27 a differentiation circuit for differentiating the digital image data 26, 28
is the differential image data that is the output of the differential circuit 27, 2
Reference numeral 9 denotes a marginal distribution calculation circuit that calculates a marginal distribution from the differential image data 28; 30, the peripheral distribution data created by the marginal distribution calculation circuit 29; and 31, a second circuit that calculates a moving difference from the marginal distribution data 30.
32 is a moving difference calculation circuit 3.
1, 33 is a zero-cross detection circuit that detects the coordinates of the zero-cross point of the movement difference data 32, and 34 is a zero-cross detection circuit 33.
The zero-crossing point coordinates 35, which are the detection results of A statistics calculation circuit divides the peripheral distribution data 30 and calculates the average height ratio and the ratio between the maximum value and the average value; 36 is a peak detection circuit that detects the coordinates of the maximum peak point as a horizontal line candidate from the moving difference data 32; 37 is the peak point coordinate output by the peak detection circuit 36, 38 is the feature amount regarding the zero crossing point calculated by the statistics calculation circuit 35 from the zero crossing point coordinate 34 and the peripheral distribution data 30, and 39 is the peak point coordinate output by the statistics calculation circuit 35. Point coordinates 37 and peripheral distribution data 3
The feature amount related to the peak point calculated from 0, 40 is the feature amount 38, 39 output by the statistical amount calculation circuit 35
Comparative evaluation to determine whether either the zero-crossing point coordinates 34, which is the output of the zero-crossing detection circuit 33, or the peak point coordinates 37, which is the output of the peak detection circuit 36, is selected as a horizontal line candidate, or whether neither is selected. The circuit 41 is the determination result of the comparison evaluation circuit 40.

An image of the outside world is captured by an imaging device 21, and an analog video signal 22 is obtained. This signal is sent to the A/D converter 23 as digital image data F(x,
y) 24 and temporarily held in the frame memory 25 in units of one screen. The digital image data 26 read from the frame memory 25 is differentiated by a differentiation circuit 27. That is, DFY(x,y)=F(x,y+1)−F(x,y)
…(4) Perform the following calculation. For DFY (x, y) (differential image data) 28 which is the output from the differentiation circuit 27,
The marginal distribution calculation circuit 29 performs the calculation SDFY (x, y) = 〓 ^x | DFY (x, y) | (5). For SDFY (x, y) (marginal distribution data) 30, which is the output of the marginal distribution calculation circuit 29, the moving ^difference calculation circuit ₃₁ calculates )−1/ _l·l 〓 ^j=1 SDFY(y−j) …(6) The following calculation is performed. DY (y) (moving difference data) 32, which is the output from the moving difference calculation circuit 31, is detected by the zero crossing detection circuit 33 as shown in FIG. The zero-crossing point coordinates 34 at which the difference between the peaks is maximum is outputted to the statistics calculation circuit 35 and the comparison evaluation circuit 40 as a horizontal line candidate.

On the other hand, the moving difference data 32 that is the output of the moving difference calculating circuit 31 is also sent to the peak detection circuit 36, and the peak detecting circuit 36 finds the maximum positive value of the moving difference data 32, and the address of its Y coordinate ( The peak point coordinates 37) are output to the statistics calculation circuit 35 as horizontal line candidates. Statistics calculation circuit 35
is the marginal distribution data 30 from the marginal distribution calculation circuit 29 and the peak point coordinates 3 from the peak detection circuit 36.
7, the average height ratio "H1/H2" and the maximum average value "MAX/H" are calculated as shown in FIG. Similar calculations are performed on the zero-crossing point coordinates 34 from the circuit 33, and the result is sent to the comparison evaluation circuit 40 as a feature amount 38.

The comparative evaluation circuit 40 first performs evaluation at the zero cross point based on a table as shown in FIG. If the feature quantity 38 is in the zero-crossing point selection area of the table above, the zero-crossing detection circuit 3
The zero cross point coordinates 34 from 3 are output as the determination result 41. If it is other than that, evaluation is performed at the peak point. This is to determine whether or not the feature amount 39 is within the peak point selection area of the table. If it is within the area, the peak detection circuit 36
The peak point coordinates 37 from 1 are output as a horizontal line candidate as a determination result 41. Furthermore, the feature amount 38
If it is outside the peak point selection area of the table, the temperature difference between the sea and sky is small and there are few sea crucifers, and as a result, no noticeable horizontal line feature appears in the peripheral distribution, making it difficult to detect the horizon. It determines that there is an unknown signal and outputs an unknown signal.

[Effects of the Invention] As detailed above, according to the present invention, an analog video signal captured by an imaging device is digitized by an A/D converter, temporarily stored in a frame memory, and then image-processed to generate the video. In a horizontal line detection device that detects a horizontal line from a signal, the digital image data read from the frame memory is differentiated by a differentiating circuit, a marginal distribution is calculated by a marginal distribution calculation circuit using the obtained differential image data, and the marginal distribution is A moving difference is calculated by a moving difference calculation circuit, and a zero crossing detection circuit detects a zero crossing point that is a horizontal line candidate from the moving difference waveform, and a peak detection circuit detects a maximum peak point that is a horizontal line candidate from the moving difference waveform. A statistical calculation circuit calculates a feature quantity from the zero crossing point outputted by the zero crossing detection circuit, the maximum peak point outputted by the peak detection circuit, and the marginal distribution outputted by the marginal distribution calculation circuit, and the horizontal line that is the output of the zero crossing detection circuit is calculated. Since the comparative evaluation circuit determines whether to select either the candidate or the horizontal line candidate that is the output of the peak detection circuit, or to select neither, the two of the zero crossing point and the peak point are determined from the moving difference data. By detecting two horizontal line candidates and using the feature values of the surrounding distribution as selection conditions, stable horizon detection is possible even when weather conditions change, such as the magnitude of temperature difference or the presence or absence of sea cucumber. It is possible to provide a horizon line detection device that determines that detection is impossible when the horizontal line is difficult to detect due to poor horizontal line detection, and can reduce false detections.

[Brief explanation of the drawing]

1 to 4 show one embodiment of the present invention, FIG. 1 is a block diagram showing the circuit configuration, and FIG. 2 is a block diagram showing the circuit configuration.
The figure shows the detection of horizontal line candidates using zero-crossing points, Figure 3 shows the detection of horizontal line candidates using peak points, Figure 4 shows the evaluation table of the comparative evaluation circuit, and Figure 5 shows the conventional horizontal line detection. FIG. 6 is a block diagram showing the circuit configuration of the device, FIG. 6 is a diagram showing the peripheral distribution under each weather condition, and FIG. 7 is a diagram showing the correspondence between the peripheral distribution and the movement difference. 1, 21... Imaging device, 2, 22... Video signal, 3, 23... A/D converter, 4, 6, 24,
26... Digital image data, 5, 25... Frame memory, 7, 27... Differential circuit, 8, 28...
... Differential image data, 9, 29 ... Marginal distribution calculation circuit, 10, 30 ... Marginal distribution data, 11, 31
...Moving difference calculation circuit, 12, 32...Moving difference data, 13, 33...Zero cross detection circuit, 1
4, 34... Zero cross point coordinates, 35... Statistics calculation circuit, 36... Peak detection circuit, 37... Peak point coordinates, 38, 39... Feature quantity, 40... Comparison evaluation circuit, 41... Judgment result.

Claims (1)

[Claims] 1. Horizontal line detection in which an analog video signal captured by an imaging device is digitized by an A/D converter, temporarily stored in a frame memory, and then subjected to image processing to detect a horizontal line from the video signal. In the apparatus, a differentiation circuit that differentiates the digital image data read from the frame memory, a marginal distribution calculation circuit that calculates the marginal distribution of the differential image data output from the differentiation circuit, and a marginal distribution output from the marginal distribution calculation circuit. A moving difference calculation circuit that calculates a moving difference of , a zero-crossing detection circuit that detects a zero-crossing point that is a horizontal line candidate from a moving difference waveform output from this moving difference calculation circuit, and a zero-crossing detection circuit that detects a zero-crossing point that is a horizontal line candidate from a moving difference waveform output from the moving difference calculation circuit. A peak detection circuit detects a maximum peak point that is a horizontal line candidate, and features are calculated from the zero crossing point output from the zero crossing detection circuit, the maximum peak point output from the peak detection circuit, and the marginal distribution output from the marginal distribution calculation circuit. a statistics calculation circuit to be sought; and whether to select either the horizontal line candidate that is the output of the zero-cross detection circuit or the horizontal line candidate that is the output of the peak detection circuit, or neither of them, based on the output of the statistics calculation circuit; 1. A horizontal line detection device comprising: a comparative evaluation circuit for making a determination.