JPH02236117A - Horizontal line detector - Google Patents

Abstract

PURPOSE:To improve the detection probability of the horizontal line by converting digital image data into a differential image and a high frequency image, detecting a candidate of the horizontal line for each image and comparing said candidates with each other. CONSTITUTION:An image data 26 read from a frame memory 25 is formed into a differential image data 28 and a high frequency image 38 in a differential circuit 27 and a high frequency image generating circuit 37, respectively. A zero crossing point which is a candidate of the horizontal line is detected at a zero cross detection circuit 33 from a first moving differential waveform 32 of the differential image data 28, and a predetermined statistic quantity 36 is operated by a first static quantity operating circuit 35. On the other hand, a maximum peak point which is a candidate of the horizontal line is detected from the high frequency image 38 by a peak detection circuit 43, and a predetermined statistic quantity 46 is obtained by a second static quantity operating circuit 45. These values 36 and 46 are compared with each other by a comparing/evaluating circuit 47.

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] Digital image data used in an image processing device of an automatic navigation system of a ship, etc., 7 is a differential circuit, 8 is differential image data, 9 is a peripheral distribution calculation circuit, IO is peripheral distribution data, 11 is a moving difference calculation circuit, l2 is moving difference data, l3 is a zero cross detection circuit, and 14 is a detection result.

With the above configuration, an image of the outside world is captured by the imaging device 1, and an analog video signal 2 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. The digital image data 6 read from the frame memory 5 is differentiated by a differentiating circuit 7. This converts the image data to F
(x, DPY(x.y)=P(x.y+1)−P
The calculation (x, y) - (1) is performed. For DFY(x.Y) (differential image data) 8 which is the output from the differentiation circuit 7, the marginal distribution calculation circuit 9 calculates SDPY(y)-Σl DFY(x,y)l
・=(2)X Perform the calculation. SDFY (x, y) (marginal distribution data) which is the output from the marginal distribution calculation circuit 9! For O, the movement difference calculation circuit 11 performs the following calculation (where l!: movement length). The maximum peak of MD (V) (moving difference data > 12) which is the output from the moving difference calculation circuit 11 is found in the zero crossing detection circuit l3, and the first zero crossing point in the direction of increasing Y address starting from that Y coordinate. is detected and its value is output as the horizontal line address.

[Problems to be Solved by the Invention] However, the horizon line detection device configured as described above (FIG. 6)
As shown in C), when the temperature difference is small and there is little sea clutter, and as a result, no noticeable horizontal line feature appears in the peripheral distribution, there is a high possibility of false detection. Also,
As shown in FIG. 6(b), even if the horizontal line feature is significant, the zero cross detection may result in an erroneous detection.

Figure 7 shows the state of false detection, and Figure 7 (a)
Since the marginal distribution is pulse-like, there is a zero-crossing point in the moving difference, but if the marginal distribution is step-like as shown in FIG. 7(b), there is no zero-crossing point in the moving difference.

The present invention has been developed 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 is a lot of sea clutter. The present invention aims to provide a horizon line detection device that can improve the probability of detecting a horizon line by not detecting it when the sea clutter is small and sea clutter is small and, as a result, no noticeable horizon feature appears in the peripheral distribution.

[Means for Solving the Problems] The present invention includes a statistics calculation circuit that divides a peripheral distribution at zero-crossing points output from a zero-crossing detection circuit and calculates an average height ratio and a ratio between a maximum value and an average value; A circuit that generates a high-frequency image from digital image data, a second marginal distribution calculation circuit that takes the absolute value of the high-frequency image and adds it for each line, a second moving difference calculation circuit that numerically differentiates the marginal distribution, and a moving difference calculation circuit that A peak detection circuit that detects the maximum peak value as a horizontal line candidate from the values, and a second statistics calculation circuit that divides the peripheral distribution by the peak coordinates and calculates the average height ratio and the ratio between the maximum value and the average value. and, based on the outputs of the statistics calculation circuit and the second statistics calculation circuit, select a horizontal line candidate that is the output of the zero cross detection circuit, select a horizontal line candidate that is the output of the peak detection circuit, or either By detecting horizontal line candidates from the curve, stable horizontal line detection is possible even when weather conditions such as the magnitude of temperature difference or the presence or absence of sea clutter change, and By calculating features such as the average height ratio and maximum average value of the surrounding distribution during processing, it is possible to determine that detection is impossible when the weather is bad and the horizon is difficult to detect, reducing false detections. .

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

FIG. 1 shows the circuit configuration. 2l is an imaging device that performs imaging, 22 is an analog video signal that is the output of the imaging device 2l, and 23 is an analog video signal that is the output of the imaging device 2l. Digital A/D
Converter, 24 is the digital image data output from the A/D converter 23, 25 is a frame memory that stores the digital image data 24 in units of one screen, 2B is the frame memory 2
Digital image data read out from 5, 27 a differentiation circuit for differentiating the digital image data 2G, 28 a differentiation circuit 2
7 is the output of differential image data, 29 is a first marginal distribution calculation circuit that creates a marginal distribution from the differential image data 28 by calculation, and 30 is the first marginal distribution created by the first marginal distribution calculation circuit 29. data, 3l is a first moving difference calculation circuit that calculates a moving difference from the first peripheral distribution data 30, and 32 is a first moving difference calculation circuit created by the first moving difference calculation circuit 3l.
33 is a zero-crossing detection circuit for detecting the zero-crossing point of the first moving difference data 32;
4 is a zero cross point which is the detection result of the zero cross detection circuit 33, and 35 is a first point which divides the peripheral distribution from the zero cross point 34 and the first peripheral distribution data 30 and calculates the average height and the ratio of the maximum value and the average value. statistics calculation circuit,
36 is the calculation result of the first statistics calculation circuit 35, 37 is a high frequency image generation circuit that generates a high frequency image using the digital image data 2B read out from the frame memory 25, 38 is high frequency canvas data, and 41 is the second A second moving difference calculation circuit that calculates a moving difference from the peripheral distribution data 40, 42 is a second moving difference calculation circuit created by the second moving difference calculation circuit 4l.
43 is a peak detection circuit that detects the maximum peak value as a horizontal line candidate from the second moving difference data 42, 44 is a peak coordinate output from the peak detection circuit 43, and 45 is the peak coordinate 44 that detects the maximum peak value as a horizontal line candidate. 4G is the calculation result of the second statistics calculation circuit 45; 47 is the calculation result of the second statistics calculation circuit 45; 4G is the calculation result of the second statistics calculation circuit 45; 1 statistics calculation circuit 3
5 outputs the calculation result 3G and the second statistics calculation circuit 45
The comparison evaluation circuit, 48
is the determination result of the comparison evaluation circuit 47.

An image of the outside world is captured by an imaging device 2l, and an analog video signal 22 is obtained. This signal is sent to A/D converter 2
3, it is converted into digital image data F (x, y) 24 and temporarily stored 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 differentiating circuit 27.

That is, DFY(x.y) − F(x.y+1) − P(x
．． y) =- (4) is performed. DFY (x.y) (differential image data) 28, which is the output from the differentiation circuit 27, is processed by the first marginal distribution calculation circuit 29.
is SDPY <y>-Σl DPY (x . y) I
- (5) Perform the operation X. For the SDFY (x, y) (marginal distribution data) 30 that is the output of the first marginal distribution calculation circuit 29, the first moving difference calculation circuit 3l calculates the
(x, y) 38 is generated and output to the second marginal distribution calculation circuit 39. The second marginal distribution calculation circuit 39 performs calculations similar to the above equation (5) to calculate second moving difference data 42 and sends it to the peak detection circuit 43.

The peak detection circuit 43 outputs the zero crossing point 34 at which the difference between the positive peak and the negative peak sandwiching the second moving point is maximum to the first statistics calculation circuit 35 and the comparison evaluation circuit 47 as a horizontal line candidate.

On the other hand, the digital image data F (x, y) 2G read out from the frame memory 25 is input to the high frequency image generation circuit 37.
From the Y coordinate address of the horizontal line candidate, the average height ratio rH1/H2J and the maximum average value rM are determined as shown in FIG.
AX/HJ is calculated and sent to the comparison evaluation circuit 47 as the calculation result 4B.

The comparison evaluation circuit 47 first performs evaluation at the zero cross point based on a table as shown in FIG.

If the calculation result 3B, which is the feature quantity of the marginal distribution output from the first statistics calculation circuit 35, is in the zero-crossing point selection area of the table, the zero-crossing detection circuit 33
The zero-crossing point 34 from If it is other than that, evaluation is performed at the peak point.

This is to determine whether or not the calculation result 46, which is the feature quantity of the marginal distribution sent from the second statistics calculation circuit 45, is within the peak point selection area of the table. The peak position 1l 144 from the detection circuit 43 is output as a determination result 48 as a horizontal line candidate. moreover,
The calculation result 46 of the second statistic calculation circuit 45 was outside the peak point selection area of the table [Effects of the Invention] As detailed above, according to the present invention, digital image data can be divided into two types, a differential image and a high-frequency image. By converting it into By calculating feature values such as ratios and maximum average values, it is possible to determine that detection is impossible when the weather is bad and the horizon is difficult to rise, reducing false detection and, as a result, increasing the detection probability sufficiently. A horizontal line detection device capable of
jJ UL can be done.

[Brief explanation of drawings]

1 to 4 show one embodiment of the present invention. FIG. 1 is a block diagram showing the circuit 1 & configuration, FIG. 2 is a diagram showing detection of the horizontal line IA h (i) by the zero cross point,
FIG. 3 is a diagram showing the detection of horizontal line candidate 11b using the peak point of a high-frequency image, FIG. 4 is a diagram showing an evaluation table for comparative evaluation U path, and FIG. 5 is a diagram showing the circuit 11i configuration of a conventional horizontal line detection device. The block diagram and the m6 diagram are diagrams showing the peripheral distribution under each weather condition, and the tA7 diagram is a diagram showing the correspondence between the peripheral distribution and the movement difference. 1.21...IAJ image device, 2.22...Video signal, 3.23.A/D converter, 4. 6, 24,
2C...Digital image data, 5+ 25...Frame memory, 7, 27...Differential path, 8,2T...Differential image data, 9...Marginal distribution calculation circuit, 10...
Marginal distribution data, 11... Moving difference calculation circuit, 12.
...Movement difference data, l3...Zero cross detection circuit,
l4...Detection result, 29...First marginal distribution calculation circuit, 30...First marginal distribution data, 3l...First
moving difference calculation circuit, 32... first moving difference data, 33... zero cross detection circuit, 34... zero cross point, 35... first statistics calculation circuit, 3B.
...Arithmetic result, 37...High frequency image generation circuit, 38.
...High frequency image, 39...Second marginal distribution calculation circuit,
40... Second peripheral distribution data, 41... Second moving difference calculation circuit, 42... Second moving difference data, 4
3...Peak detection circuit, 44...Peak coordinates, 45
...Second statistics calculation circuit, 4B...Computation result, 4
7... Comparison evaluation circuit, 48... Judgment result. Patent Applicant: Ryozo Tsutsui, Director, Technology Research Headquarters, Defense Agency Figure 4 (a) (b) Figure 6 (a) (C) (b)

Claims (1)

[Scope of Claims] A horizon line detection device that 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 detect a horizon line, comprising: the frame memory; a differentiation circuit that differentiates digital image data read out from the differentiation circuit; a first 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 first marginal distribution calculation circuit. a first moving difference calculation circuit that calculates a moving difference; a zero-crossing detection circuit that detects a zero-crossing point that is a horizontal line candidate from the moving difference waveform output from this first moving difference calculation circuit; and an output of this zero-crossing detection circuit. a first statistics calculation circuit that calculates a feature amount from the zero crossing point and the marginal distribution outputted from the first marginal distribution calculation circuit; an image generation circuit; a second marginal distribution calculation circuit that calculates a marginal distribution from the high frequency image output from the high frequency image generation circuit; and a second marginal distribution calculation circuit that calculates a moving difference of the marginal distribution output from the second marginal distribution calculation circuit. a moving difference calculation circuit; a peak detection circuit for detecting a maximum peak point that is a horizontal line candidate from the movement difference waveform outputted by this second moving difference calculation circuit; 2
a second statistics calculation circuit that calculates a feature quantity from the marginal distribution output from the marginal distribution calculation circuit; and an output of the zero-cross detection circuit based on the outputs of the first statistics calculation circuit and the second statistics calculation circuit. 1. A horizontal line detection device comprising: a comparison evaluation circuit that determines whether to select one of a certain horizontal line candidate and the horizontal line candidate output from the peak detection circuit, or to select neither of the horizontal line candidates.