JPS6157757B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention stores the contents of a memory circuit that stores an image (hereinafter referred to as a reference image) that has a two-dimensional spread surrounded by a reference window set within a screen, based on the reference window of an initial screen. If the shape of the reference image becomes significantly different from the initial image after the image is memorized, it can be stably changed by rewriting it to the reference image of this screen on an appropriate screen.
The present invention relates to a correlated image tracking device that tracks a target image.

In conventional devices of this type, a reference image is stored in a memory circuit on an initial screen, and a correlation calculation is performed between this stored reference image and a continuing image in the screen to calculate the relationship between the two. The target image was tracked by finding the matching position, but the target image was enlarged, reduced,
Alternatively, when the camera turns, etc., a clear matching position cannot be found between the reference image on the initial screen and the image on the current screen, and tracking becomes impossible.

In order to eliminate this drawback, the present invention measures the initial correlation of the correlation function form in the continuous screens by constantly measuring the maximum value and spread width of the correlation function in the initial screen and continuous screens. When a change from the functional form is observed, and this change becomes significant, the memory circuit erases the old reference image on the initial screen and stores the newest reference image on the current screen, thereby storing the correlation calculation results. This method enables a clear alignment position to be obtained, and will be described in detail below.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, in which a video signal 1 output from an imaging device such as a TV camera is converted into a digital image signal 3 by an analog-to-digital converter 2. .

In FIG. 2 showing the relationship between the screen, the target image, and the reference window, a reference window 6 is manually set surrounding the target image 5 on the screen 4, and a calculation window 7 is set surrounding these. There is. When a capture command is given, a new field immediately after it (referred to as the initial field) is created.
The digital image signal 3 of the picture surrounded by the reference window in 2 is selected by the reference window gate 8 and written into the reference data storage circuit 9. Further, in the same field, the digital image signal 3 of the image surrounded by the calculation window 7 surrounding the reference window 6 is selected by the calculation window gate 10 and written into the calculation data storage circuit 11. When writing to the calculation data storage circuit 11 is completed, reading of the contents of the reference data storage circuit and the calculation data storage circuit is executed. The readout outputs from these two memory circuits are each output from the correlation calculator 1.
2, and a correlation calculation is performed. FIG. 3 is a diagram showing an example of this correlation calculation result,
The X and Y axes indicate the amount of shift in the horizontal and vertical directions of the reference image in the correlation calculation, respectively, and the vertical axis indicates the correlation value C.
shows. The correlation value output 13 of the correlation calculator 12 is supplied to the maximum/minimum value detection circuit 14, and the correlation value C
The maximum value C _MAX and the minimum value C _MIN of are detected.
Also, the horizontal/vertical shift amount output 1 of the correlation calculator 12
5 is supplied to the correlation width determination circuit 16, and the correlation value C
A horizontal expansion width W _x and a vertical expansion width W _y where C _MAX is half the value of C _MIN and (C _MAX + C _MIN )/2 are determined. _These data C _{MAX , W}
Assuming _AX (1) _{, W} . Note _that the matching position of the reference image (S _x (1), _{S y (} 1)) is found from the horizontal and vertical shift _amounts S The reference window and calculation window centers of the next field are set at this position.

In the n-th field after the initial field, the reference data storage circuit 9 stores the reference data in the initial field. Further, in the calculation data storage circuit 11, a digital image signal of an image surrounded by the current calculation window centered at the matching position in the previous field is selected by the calculation window gate 10 and written. Then, in the same way as in the initial field, a correlation calculation is performed, and the maximum value C _{MAX (o)} of the correlation value C and the horizontal and vertical expansion widths W _{X (o)} and W _{y (o)} are determined, These data are input to the microprocessor 17.

Generally, when a target image is enlarged, reduced, rotated, etc., the shape of the target image included in the current calculation window will be greatly different from the shape of the target image stored in the reference data storage circuit in the initial field. Therefore, the maximum value C _MAX of the correlation curve shown in FIG. 3 decreases, and the spreading widths W _x and W _y increase, making it difficult to find a clear matching position. In order to solve this problem, the present invention uses the following method.

In the microprocessor 17, the C _MA input from the initial field and the current field is
_X (1), C _{MAX (o)} , W _X (1), W _{X (o)} and W _y (1), W _{y (o)}
Using α, β, and γ as constants, find the following evaluation function value Fn.

F _o = α | C _{MAX (o)} / C _MAX (1) - C _MAX (1) / C _{MAX (o)} | + β | W _{X (o)} / W _X (1) - W
_{X ( 1 ) / W} When the shape of the target image in the field is not significantly different, the shape of the correlation curve in FIG. 3 has the same shape as that in the initial field, and C _MAX(o) C _MAX (1), W _X(o) W _X (1), and W
_y(o) W _y (1), which is FO.

However, if the shape of the target image is greatly different from that of the initial field, and C _MAX(o) , W _X(o) , and W _y(o) each have values far different from those in the initial field, F _o takes on a large positive value.
The microprocessor 17 monitors this F _o and outputs a rewrite command to the reference data storage circuit 9 when it exceeds a predetermined threshold Th. When this command is output, in the next field, the matching position detected in the current field (S _{x (o)} , S _{y (
o)} The contents of the reference data storage circuit 9 are rewritten to the digital image signal of the image surrounded by the reference window centered at ), the same correlation calculation as the initial field is executed, and the tracking of the target image by the reference window is stabilized. will be continued.

As described above, according to the present invention, changes in the shape of the tracked target image are observed, and if the current target image shape becomes significantly different from the initially stored shape, the target image is memorized again. Therefore, it is possible to stably track the target image regardless of changes such as enlargement, reduction, turning, etc. of the target image.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention;
Fig. 2 is a diagram showing the relationship between the screen, the target image, and the reference window, and Fig. 3 is a diagram showing an example of the correlation calculation results. Digital image signal, 4 is a screen, 5 is a target image, 6 is a reference window, 7 is a calculation window, 8 is a reference window gate, 9 is a reference data storage circuit, 10 is a calculation window gate, 11 is a calculation data storage circuit, 12 13 is a correlation value output, 14 is a maximum/minimum value detection circuit, 15 is a horizontal/vertical shift amount output, 16 is a correlation width determining circuit, and 17 is a microprocessor.

Claims (1)

[Claims] 1. Store an image with a two-dimensional spread surrounded by a reference window set within one screen in a memory circuit,
A correlation calculation is performed between this image and the above-mentioned screen and images with a two-dimensional spread within the continuous screen, and the image position that most closely matches the image surrounded by the reference window is found among the images within each of the above-mentioned screens. Find from
In a correlated image tracking device that uses these image positions as tracking points in each screen, the maximum value and spread width of each correlation function are determined in the initial screen and in the continuous screen, and the initial screen The comparison value between the maximum value calculated within the initial screen and the maximum value calculated within the subsequent screen, and the comparison value between the expansion width calculated within the initial screen and the expansion width calculated within the subsequent screen. When the determined evaluation value exceeds the determined threshold, on the next screen, an image with a two-dimensional spread surrounded by a reference window set within the screen is re-stored in the memory circuit. A correlated image tracking device characterized by: