JPS625556B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention converts an image signal obtained from an image sensor such as a TV camera into an analog-to-digital converter, and performs correlation calculation processing on the digital image signal. This invention relates to a correlation tracking device that tracks a target.

Conventional devices of this kind use a cross-shaped correlation calculation window, as shown in Figure 1, and perform correlation calculations independently in each direction horizontal and vertical to the scanning line to obtain the correlation coefficient. The correlation window is moved to a coordinate position that provides a value, and a desired target or scene within the field of view of an image sensor (not shown) is tracked.

That is, in the figure, a reference window 3 and correlation windows 4a and 4b are set surrounding a target (or scene) 2 in a screen 1. A signal of a pixel surrounded by the reference window 3 at a specific time is used as a reference signal, and a cross-correlation function between this signal and a signal of a pixel surrounded by each of the correlation windows 4a and 4b thereafter is determined. Then, by detecting the maximum points of these cross-correlation functions and finding the maximum correlation position, the position of the target 2 is found, and by setting a new reference window 3 at this position,
The target 2 is tracked by the reference window 3.

FIG. 2 shows the configuration of a conventional correlation tracking device, in which subfixes a and b correspond to the horizontal and vertical directions, respectively. An analog video signal obtained from an image sensor 5 such as a TV camera is processed by a synchronization separation circuit 6 where a synchronization signal is extracted and an analog
The signal is converted into a digital video signal by the digital converter 7 and supplied to the reference window setting circuit 8. or,
The synchronization separation circuit 6 is used as a time reference for each circuit. This is the output of the reference window setting circuit 8. The reference window image signals 9 are input to reference image memories 12a and 12b via selection circuits 10a and 10b, respectively. The selection circuits 10a, 10b are closed at a specific time, and the reference window image signal 9 is stored in the reference image memories 12a, 12b. Note that the corner turn memory 11 is a buffer for converting the scanning direction by 90 degrees since the raster of the original image signal is scanned in the horizontal direction when determining the correlation in the vertical direction. Correlation calculation circuits 14a and 14b receive reference image signals 13a and 1 at a specific point in time, in which signals sampled from images surrounded by a reference window at a specific point in time are stored.
3b, and the cross-correlation function between this reference signal and the image signal sampled from the image surrounded by the horizontal and vertical correlation windows is determined. The correlation calculation result is sent to the correlation function value evaluation circuit 15.
By detecting the maximum point of the correlation function, the position coordinates of the image that most closely matches the image surrounded by the initially set reference window are determined, and the new position of the target is detected. These position coordinates are fed back to the reference window setting circuit 8, and a reference window is set at the new target position. By the way, in conventional devices, correlation calculation circuits, etc. were provided separately for calculations in the horizontal and vertical directions, which resulted in a significant increase in the amount of hardware, making it difficult to use for mobile vehicles, aircraft, etc., which have severe load weight and volume restrictions. It was difficult to get on board.

The present invention was made in view of these drawbacks, and attempts to provide a compact and lightweight correlation tracking device that performs correlation calculations alternately in the horizontal and vertical directions by using hardware related to correlation calculations. It is something to do.

The apparatus according to the present invention will be explained in detail below.

In FIG. 3, the image sensor 5, synchronous separator 6, analog-to-digital converter 7, reference window setting circuit 8, reference window image signal 9, selection circuit 10, and corner turn memory 11 are the same as those described in FIG. This differs from FIG. 2 in that the reference image memory 12, the signal line of the reference image signal 13 at a specific point in time, the correlation calculation circuit 14, the correlation function value evaluation circuit 15, etc. are all combined into one set. The horizontal/vertical input switching circuit 16 and the horizontal/vertical output switching circuit 17 are circuits that are not present in conventional devices, and switch the input of the correlation calculation circuit 14 for each field or frame, thereby allowing the correlation calculation circuit 14 and the correlation function value evaluation circuit 15 to switch. It is designed so that it can be performed in groups.

As shown in FIG. 4, it is assumed that the blocks 18 indicating the frame (or field) divisions of the image are shifting over time, and the timing signal 19 for horizontal/vertical switching at that time is obtained from the synchronization separation circuit 6.

The operation shown in FIG. 3 will be explained below in relation to the timing shown in FIG.

When the block is (2n-2), the horizontal/vertical switching timing signal 19 is 1, and at this point the horizontal/vertical input switching circuit 16 is tilted upward, that is, toward the reference window image signal side. The correlation calculation circuit 14 and the correlation function value evaluation circuit 15 perform horizontal correlation processing, and by the time of block (2n-1), the reference window setting circuit 8 is output through the horizontal/vertical output switching circuit 17 which has also fallen upward. outputs the position signal of the next horizontal reference window. At the time of the same block (2n-2), the reference window image signal 9 of the block period is stored in the corner turn memory 11.

Next, at the point of block (2n-1),
Horizontal/vertical input switching circuit 16, horizontal/vertical output circuit 1
7 falls down and correlation processing is corner turn memory 1
Vertical processing is performed based on the output of 1.

Next, at block (2n), horizontal processing is performed again in the same way as block (2n-2), and then vertical processing, and so on. repeated alternately.

Note that the function of the present invention is the same as that of the conventional apparatus in that a reference image at a specific time point can be used as an input for correlation calculation using a reference image memory.

As described above, in this invention, by performing processing in the horizontal and vertical directions sequentially, the required hardware for the correlation processing is reduced to about half, and it can be used in mobile vehicles, which was previously impossible to install.
An extremely small and lightweight correlation tracking device that can be mounted on an aircraft or the like can be realized.

[Brief explanation of the drawing]

Fig. 1 is a layout diagram showing the relationship between the screen, the reference window, and the target to be tracked, Fig. 2 is a block diagram showing the configuration of a conventional correlation tracking device, and Fig. 3 is a correlation calculation that is a feature of the present invention. FIG. 4 is a diagram illustrating switching timing of correlation calculation according to the present invention. 1 is the screen, 2 is the target, 3 is the reference window, 4a, 4b
is a correlation window, 5 is an image sensor, 6 is a synchronous separation circuit,
7 is an analog-digital converter, 8 is a reference window setting circuit, 9 is an image signal within the reference window, 10a, 10b
11 is a selection circuit, 11 is a corner turn memory, and 12 is a selection circuit.
a and 12b are reference image memories, 13a and 13b are reference image signals at specific times, 14a and 14b are correlation calculation circuits, 15a and 15b are correlation function value evaluation circuits, 16 is a horizontal/vertical input switching circuit, and 17 is a horizontal/vertical output In the switching circuit, 18 is a block indicating a frame (or field) division, and 19 is a timing signal for horizontal and vertical switching. It should be noted that the same or corresponding parts in the figures are indicated by the same reference numerals.

Claims (1)

[Claims] 1. An image sensor, an analog-to-digital converter that converts the image signal obtained by the image sensor into analog-to-digital, and the analog-to-digital converter that exists within the reference window set by the reference window setting means at a specific time. a reference image memory for storing the digital signal as a reference window image signal;
At the time of the field or frame where horizontal correlation calculation processing is performed between the correlated signal obtained from the digital signal after the digital signal obtained at the specific point in time and the image signal within the reference window of the reference image memory. At the same time, the raster scanning direction of the reference window image signal is stored at 90 degrees, and the vertically transformed reference window image signal is stored at the time of the field or frame where vertical correlation processing is performed. a corner turn memory that outputs an image signal; horizontal and vertical input switching means that alternately switches between the correlated signal and the output of the corner turn memory according to horizontal and vertical switching timing; and the correlated signal and the reference image memory. and a correlation calculation processing means for alternately inputting the output of the corner turn memory and the output of the reference image memory and performing correlation calculation processing in the horizontal and vertical directions alternately for each field or each frame. Characteristic correlation tracking device.