JPH0686293A - Image tracking device - Google Patents

Abstract

PURPOSE:To prevent the tracking performance from being spoiled even against a sudden variation of a luminance level by providing an average value calculating circuit and a subtracter in an input stage of image data, eliminating a DC component from the image data and executing a correlation operation by using only an AC component of the image data. CONSTITUTION:An average value calculating circuit 1 calculates an average value of a one-line portion, outputs an average value signal (b) to a subtracter 2, and the subtracter 2 subtracts the signal (b) from input image data (a), and outputs image data (c) from which a DC portion is eliminated, to a correlation arithmetic circuit 3 and a template memory 5. As for the image data, the correlation arithmetic circuit 3 calculates an expression in accordance with the image data (c) outputted from the subtracter 2. In the expression, the number of samples in a template data area, the number of samples of input image data, luminance of template data, and luminance of the input image data are denoted as (m), (n), TK, and Xi, respectively, and at the time of (i)=A, the minimum correlation value signal Di is obtained. In such a way, [A+(m-1)/2] can be obtained as a target position signal (e).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image tracking device for detecting the position of a moving target, and more particularly to an image tracking device using a correlation tracking method.

[0002]

2. Description of the Related Art A conventional correlation tracking type image tracking device is
As shown in FIG. 2, a correlation calculation circuit 3 which inputs the image data a and outputs a correlation value signal d with the template data f of the region of a specific size stored one frame before,
A maximum correlation position detection circuit 4 that detects the maximum correlation position of the correlation value signal d in one frame and outputs a target position signal e, and a region of a specific size in the vicinity of the target position e from the image data a. And the template memory 5 which stores the data of the above and outputs it as the template data f in the next frame.

The operation of the template data area as one-dimensional data (data for one line) will be described below. FIGS. 3i) and ii) show an example of image data (hereinafter referred to as template data) of an area of a specific size near the target position stored in the previous frame and image data input in the frame.

The number of samples in the region of the template data is m, the number of samples in the input image data is n, the brightness of the template data is T _k (k = 1, 2, ..., M), and the brightness of the input image data is X _l. (1 = 1, 2, ..., N).

Various arithmetic expressions are used for the correlation arithmetic circuit 3 of FIG. 2 in order to speed up the processing, but here the following mathematical expression 1 which is one of the simplest arithmetic expressions is used. And

[0006]

[Equation 1]

The correlation calculation circuit 3 outputs D _i as a correlation value signal d according to the input image data a. The maximum correlation position detection circuit 4 detects the minimum value of D _{i and} sets i at that time to i
_{If it is min} , [ _imin + (m-1) / 2] is output as the target position signal e.

The template memory has a [Xi
_min , Xi _{min + 1} , ..., Xi _{min + m-1} ] is stored as template data f of the next frame.

Referring to the example of FIG. 3, the correlation value signal d is 0 when i = A, and d> 0 when i ≠ A. Therefore, the target position signal e becomes [A + (m-1) / 2], and [X _A , X _{A + 1} , ...
X _{A + m-1} ] is stored.

As described above, the correlation tracking type image tracking device tracks the target value 6 by the correlation value with the template data of a certain size, so that it is resistant to the noise of the image signal and gradually increases in size. It has excellent tracking characteristics even for a moving target that changes (approaches or moves away).

[0011]

However, this conventional correlation tracking type image tracking device has a drawback that tracking is impossible when the brightness level (offset) of the input image data changes abruptly. That is, when the input image data changes from FIG. 3ii) to the next frame as shown in FIG. 3iii), Formula 1 is not the minimum at i = A.

In view of the above-mentioned drawbacks, a technical object of the present invention is to provide an image tracking device capable of effectively tracking a change in the brightness level of input image data.

[0013]

According to the present invention, a correlation calculation circuit for inputting image data and outputting a correlation value signal with template data of an area of a predetermined size stored one frame before, A maximum correlation position detection circuit that detects a maximum correlation position based on the correlation value signal and outputs a target position signal, and a template that stores image data of a predetermined size area near the maximum correlation position as template data for the next frame. In an image tracking device using a correlation tracking method having a memory, an average value calculation circuit that outputs an average value signal for one line of the image data to an image data input stage, and the image data and the average value signal And a subtractor for outputting the subtracted image data obtained by removing the DC component from the image data based on the difference to the correlation calculation circuit. Tail device is obtained.

That is, the image tracking device of the present invention inputs the image data and outputs an average value calculation circuit for outputting the average value signal of the image data of one line, and the difference between the input image data and the average value signal. A subtractor that outputs image data that has been calculated and has the DC component removed, and the subtracter output image data,
Correlation calculation circuit for outputting a correlation value signal with the template data of the area of the specific size stored one frame before, and maximum correlation for detecting a maximum correlation position based on the correlation value signal and outputting a target position signal A position detection circuit and a template memory for storing image data of the area of the specific size as template data for the next frame are provided in the vicinity of the target position signal.

[0015]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of an image tracking device according to the present invention, and the same parts as those in FIG. 2 are designated by the same reference numerals. In the figure, the image tracking device of the present embodiment is different from the conventional one in that an average value calculation circuit 1 and a subtractor 2 are provided in the input stage of the image data. The average value calculation circuit 1 calculates the average value for one line and outputs the average value signal b to the subtractor 2. Subtractor 2
The average value signal b is subtracted from the input image data a, and the image data c from which the DC component is removed is output to the correlation calculation circuit 3 and the template memory 5.

Explaining the example of FIG. 3, when the image data a of FIG. 3ii) is input, the subtracter 2 output image data c is as shown in FIG. 4ii). Therefore, the data as shown in FIG. 4i) is stored in the template memory.

In the next frame, even if an image whose abrupt offset level is changed as shown in FIG. 3iii) is input as the image data a, the subtracter 2 output image data c is
As shown in FIG. 4iii), the level is the same as that of the previous frame.

The correlation calculation circuit 3 calculates the equation 1 according to the output image data c of the subtracter 2 and outputs the correlation value signal d. The maximum correlation position detection circuit 4 detects the minimum value of the correlation value signal d and outputs the target position signal e based on i at that time. As shown in FIG. 4iii), the correlation value signal d is i = A
When the target position signal e is [A + (m-
1) / 2] is output.

[0020]

As described above, according to the present invention, the correlation calculation is performed after the DC component of the input image data is removed, so that the tracking can be performed even when the brightness level (offset level) changes rapidly. It has an effect that performance is not impaired.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional image tracking device.

FIG. 3 is a diagram showing an example of input image data and template data.

FIG. 4 is a diagram showing an example of image data and template data from which DC components have been removed.

[Explanation of symbols]

 1 Average value calculation circuit 2 Subtractor 3 Correlation calculation circuit 4 Maximum correlation position detection circuit 5 Template memory 6 Target value

Claims (1)

[Claims] 1. A correlation calculation circuit for inputting image data and outputting a correlation value signal with template data of an area of a predetermined size stored one frame before, and a maximum correlation position based on the correlation value signal. An image using a correlation tracking method having a maximum correlation position detection circuit that detects and outputs a target position signal, and a template memory that stores image data of a region of a predetermined size near the maximum correlation position as template data for the next frame. In the tracking device, an average value calculation circuit that outputs an average value signal for one line of the image data to an image data input stage, and a DC component based on the difference between the image data and the average value signal And a subtractor for outputting the subtracted image data removed from the correlation calculation circuit to the correlation calculation circuit.