JPS5932741B2 - Optical automatic target tracking device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an automatic optical target tracking device that compares images of an imaging target area obtained at different times using an imaging device, and controls the imaging direction of the imaging device from the comparison output. Regarding improvements.

In such an automatic tracking device, a target image signal is extracted by detecting the level difference in the image signal due to the contrast difference between a specific target image and a background image in the image, and the deviation of this signal on the imaging screen is detected. generates an error signal, sends this signal as a servo signal to the camera platform support, and tracks the target so that the target image is always visible on the imaging screen.
A so-called point tracker method is used.

However, in this point tracker method, the tracking target is only the outer periphery of the target or a part of the target where a predetermined cost thrust can be obtained.
As the target moves, the contrast with the background often decreases, and parts of the target are often blocked by other obstacles, making automatic tracking impossible in many cases.

Therefore, in order to continue automatic tracking, it is necessary to add a memory circuit or the like to the tracking device to temporarily secure the image signal of the area where the target was present, and then re-capture the predetermined contrast area when the target appears again. Must not be. However, when a tracking device is mounted on an aircraft, for example, the relative positional relationship with the target object changes at a high speed, so partial tracking deviations are large, making it difficult to re-acquire the target object. In addition, in order to eliminate these drawbacks, it is necessary to add expensive and complicated equipment such as computers.
There is a drawback that expensive equipment is required to re-acquire and re-track the target in a short period of time. Furthermore, since the conventional device focuses on the contrast difference at one location in the point tracker, it is difficult to capture the true target object at the center of the image.

Furthermore, once the point tracker loses sight of the target, it requires an operator to re-acquire it, which is extremely inconvenient in practice. The present invention has been made in view of the above circumstances, and includes a target detection system using a point tracker circuit and a target detection system using an area tracker circuit, and when a target is detected by the point tracker circuit, the target is tracked by this circuit. When the target cannot be detected by this circuit, the area tracker circuit automatically switches to target detection, and the point tracking circuit itself activates the target acquisition function, and when re-acquiring, the point tracker circuit automatically tracks the target. The present invention provides an automatic target tracking device. An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a television image pickup device using a television image pickup tube or a television scanning type image pickup element array.

A television video signal obtained by imaging a region to be imaged by the imaging device 1 is guided to a point tracker circuit 2 and an area tracker circuit 3. Each servo control error signal output obtained from each of the circuits 2 and 3 is led to a switch 4. This switch 4 selects and derives the error signal from the point tracker circuit 2 as an output for servo control while the point tracker circuit 2 is performing a target detection operation. The switch 4 performs a switching operation to automatically derive the error signal from the area tracker circuit 3 as a servo control signal when the target detection signal is no longer obtained from the point tracker circuit 2. be. The servo control error signal derived from the switch 4 in this way is guided to the drive device 5, where the pan head 6 is driven once so that the error signal manual force becomes zero, and the imaging direction of the imaging device 1 is adjusted. control.

Note that the imaging device 1 is not limited to a normal television imaging device, but may also be a device that uses infrared photography or laser beams.

Furthermore, in the device of the present invention, the point tracker circuit 2 itself has a target search function (sweep mode), performs a target search when the area tracker circuit is activated, and when the target is captured again, points tracker circuit 2 performs the target search again by a switching signal. It is characterized in that the error signal from the picker circuit 2 is derived from the switch 4 as a servo control signal.

That is, the point tracker circuit 2 is constructed as shown in FIG.

In FIG. 2, the television image output signal as shown in FIG. 3a from the image pickup device 1 is sequentially analog-digital (
! A)) The signal is introduced into the converter 21, where it is converted into a digital signal as shown in FIG. These four tracker circuits 22, 23, and 2425 correspond to image gates Bl, B2, B3, and B4 on two orthogonal axes, respectively, as shown in FIG. Edges El, E2, E3,
They detect E4 and track the center A of the image, and both have the same circuit configuration. Therefore, the image signal from the A/D converter 21 is supplied to the gate circuit 221 of the tracker circuit 22.

This gate circuit 221 opens a gate of a predetermined width set by a gate signal generator 225 at a gate position indicated by a gate position signal from a sweep signal generation circuit 224, and corresponds to image gate B1 in FIG. 4, for example. A portion corresponding to E1 in FIG. 4 is extracted from the captured image output signal. This extracted signal is supplied to the edge detection circuit 222,
For example, the edge signal of the target image is extracted by a differentiator and the first
is supplied to the AND circuit 261. Edge detection circuit 22
The output of 2 is also supplied to a level detection circuit 223.

The level detection circuit 223 detects the output level of the edge detection circuit 222, and when the output level is equal to or higher than a predetermined value, it is determined to be a target edge signal, and the edge position information is E1, which is based on 0 in FIG.
The position information is supplied to the sweep signal generation circuit 224 as a sweep control signal. The sweep signal generation circuit 224 receives a gate signal for setting the gate width from the gate signal generator 225, and also receives a signal representing edge position information from the level detection circuit 223, so that the sweep signal generation circuit 224 adjusts the gate so that the center of the gate is at the edge detection position. A gate position signal for controlling the gate is supplied to the gate circuit 221.

In other words, the gate circuit 221. The closed loop of the edge detection circuit 222, level detection circuit 223, and sweep signal generation circuit 224 functions as a tracking mode when an edge signal of the target image is detected, and the gate signal is sent so that the center of the gate is always at the detection position of the edge signal. control. On the other hand, when the edge signal of the target image is not obtained and the target is lost, the loop is opened and automatically switches to the sweep mode, causing the gate signal to perform a search sweep in the direction of arrow a in Figure 4. . That is, when the edge signal of the target image cannot be obtained, the level detection circuit 2
23 does not output edge position information. in this case,
The sweep signal generation circuit 224 automatically switches from the tracking mode to the sweep mode, and repeatedly sweeps the gate by the sweep width set by the sweep width setting circuit 226 (for example, a in FIG. 4). Now, the output signal of the sweep signal generation circuit 224 is also supplied to the error detection circuit 271, and similarly, the gate position of the sweep signal generation circuit output is also supplied from another tracker circuit 23 (corresponding to image gate B2 in FIG. 4). The signal is error detector 2
71. The error detection circuit 271 calculates the sum of the gate position signals from both sweep signal generation circuits to find the center position of the target image, and calculates the center position of the target image one frame before (for example, 1/30 s
The difference from the center position determined before ec) is detected and supplied to the gate circuit 281 as a horizontal error signal. In addition, the first
The edge detection circuit output signal of another tracker circuit 23 paired with this AND circuit 261 is introduced as the other input of the AND circuit 261, and when an edge signal is obtained in either case, the output signal of the first AND circuit 261 turns on the gate. The signal is supplied to the gate circuit 281 and the second AND circuit 262 as a signal.

Therefore, the gate circuit 281 is connected to the paired trouble force circuit 2.
The horizontal error signal is derived only when the targets 2 and 23 capture the target, and the horizontal error signal is not output when the target is lost.

The above has explained the point tracker circuit system and its operation for the horizontal gates Bl and B2 in FIG. 4, but the same applies to the vertical gates B3 and B4. A vertical error signal is derived via the gate circuit 282 and supplied to the switch 4 together with the output of the gate circuit 281.

Further, from the third AND circuit 263, the tracker circuit 24,
In step 25, an output is derived only when both target images are captured, and is supplied to a second AND circuit 262. Therefore, the output of the second AND circuit 262 is derived as a detection signal only when the point tracker circuit 2 captures the target, and no output is derived when the target is lost, so this is used as the switching signal. It is supplied to the switching device 4. The switch 4 connects tracker circuits 22, 23, 2
4 and 25 are both detecting edge signals of the target image, the driving device 5 uses the horizontal and vertical error signals as servo signals.
When at least one of the tracker circuits 22, 23, 24, and 25 no longer detects an edge signal, an error signal from the area tracker circuit 3, which will be described later, is supplied to the drive device 5 as a servo signal. The driving device 5 controls the imaging direction of the imaging device 1 by driving the pan head 6 so that the input error signal becomes zero. In the present invention, when the servo signal to the drive device 5 is switched to the error signal from the area tracker circuit 3, at the same time, the point tracker circuit 2 switches to the sweep mode, sweeps the image gate, and sends the point tracker circuit 2 to the error signal. It also operates to search for the target, and when an edge signal of the target image is detected by each image gate of the point tracker circuit 2, it switches to tracking mode again and the center of the image gate detects the edge signal. At the same time, the servo signals are also switched to the horizontal and vertical error signals from the point tracker circuit 2.

Next, the area tracker circuit 3 can employ, for example, an area tracker one-type detection device as described in Japanese Patent Application No. 53-21800.

That is, vertical signals and horizontal signals are individually extracted from the image screen from the image pickup device 1 using elongated cross gate signals, and the signals are detected when the image on the screen (the image of the imaging target area selected as the target) moves. It detects the phase change of the video signal and supplies it to the switch 4 as an error signal.

That is, in FIG. 5, which shows a signal processing circuit for only one of the cross gate signals, the video signal from the image pickup device 1 is supplied to the analog gate circuit 31, where a horizontal video signal on the monitor screen is obtained.

The output of the analog gate circuit 31 is supplied to an analog-to-digital converter 32 which successively digitizes the analog picture pattern. The analog-to-digital (!A) converter 32 includes a smoothing circuit 321, a first delay circuit 322, and a comparator 3.
Consists of 23.

The video signal output from the analog gate circuit 31 is branched, one of which is supplied to a smoothing circuit 321 constituting the A/D converter 32 to derive a smoothed signal and supplied to a comparator 323. On the other hand, the other video signal branched from the analog gate circuit 31 is supplied to the delay circuit 322, and after receiving compensation for the delay time so that the time delay matches the signal on the smoothing circuit 321 path, the signal is sent to the comparator 323.
supplied to

In this comparator 323, the signal from the smoothing circuit 321 and
Similarly, the amplitude level is compared with the signal from the delay circuit 322, and only when the output amplitude from the delay circuit 322 is large, a level "1" is derived, otherwise a binary pulse signal is derived with a level "0". The binary pulse code output thus obtained from the A/D converter 32 is a digital output of a signal in a predetermined region (area) of the image signal obtained in one horizontal scan, and is an image of the predetermined region. It's a pattern.

This image pattern is supplied to the electronic switch 33.
The electronic switch 33 selectively switches the output signal of the A/D converter 32 to the first one according to the frame image obtained by the imaging device 1.
The signal is switched and supplied to the memory circuit 341 and the second memory circuit 342.

For example, first, the reference image pattern is stored in the first memory circuit 3.
41, and the latest image patterns successively obtained frame by frame from the image pickup device 1 are successively stored in the second storage circuit 342 in an updated manner.

Then, the positional deviation between the reference image pattern stored in the first storage circuit 341 and the latest image pattern stored in the second storage circuit 342 is detected by the detector 36 within one frame time, and the area tracker circuit is output as an error signal.

That is, the output of the second storage circuit 342 is supplied via the second delay circuit 35 to an adder 361 that sets a delay time arbitrarily and constitutes the detector 36 . The adder 361 introduces digital image patterns from the first storage circuit 341 and the second delay circuit 35, performs a match (AND) of both digital signals, and derives a cumulative addition signal of the match signals. .

For example, if the reference image pattern stored in the first storage circuit 341 is 000111 and the comparison image pattern stored in the second storage circuit 342 is 111000, the comparison image pattern is delayed by a time corresponding to 3 steps. If the match signal is supplied to the adder 361 as 000111, the cumulative addition value of the match signal becomes 3, which is the maximum.

Therefore, both signals compared when the maximum value of the cumulative addition value is detected match, and the amount of delay at this time corresponds to the deviation between the reference image pattern and the comparison image pattern. Now, the second delay circuit 35 derives a signal that is sequentially delayed by a minute time (time corresponding to a unit step) with respect to the previous delayed output and supplies it to the adder 361. Amplitude level information corresponding to the degree of deviation from the signal is supplied to the error detector 362. Therefore,
The error detector 362 is configured to detect the maximum value of the amplitude level and output a signal corresponding to the amount of delay of the second delay circuit 35 at the time of detection as an error signal. In other words, the error detector 362 is supplied with a time difference signal representing the amount of delay from the second delay circuit 35 via, for example, an adder 361, and when maximum amplitude level information is obtained, the comparison image at that time is Outputs a time difference signal that is the amount of pattern delay. This time difference signal corresponds to the deviation of the image patterns stored in the first and second storage circuits 341 and 342, that is, the amount of displacement. Error detector 362
A displacement amount, that is, an error signal is detected from the switch 4, and at the same time when the maximum amplitude level falls below the reference value, an electronic switch 33 is sent to update the image information stored in the first storage circuit 341. A switch switching control signal is provided. Although FIG. 5 above particularly describes a configuration in which the direction control of the image pickup device is controlled only in the horizontal direction, a vertical control system is also added to the configuration of the analog gate circuit 31 to control the subsequent signals. If a processing system is also installed, tracking in the upper, lower, left, and right directions on the screen can be easily achieved.
The area tracker circuit 3 as described above converts the image pattern into a digital signal, and converts the image pattern into a digital signal, and converts the image pattern into a digital signal.
The third imaging pattern is compared with the third imaging pattern so as to sequentially detect the phase difference, and the comparison result is used to control the imaging direction of the imaging device 1. There is a high probability that an imaging area including the following can be secured.

Therefore, according to the automatic optical target tracking device according to the present invention as described above, the point tracker circuit 2 and the area tracker circuit 3 are provided, and the point tracker circuit 2
When detecting a target, the output of this device is used as a servo signal to track the target in tracking mode, and when the device cannot detect a target, this is automatically detected and the output of the area tracker circuit 3 is used as a servo signal. At the same time, the point tracker circuit 2 itself operates in a sweep mode to sweep the search gate and reacquire the target.

Then, at the same time as reacquisition, target tracking is continued using the output of the point tracker circuit 2 as a servo signal. As a result, according to the present invention, the automatic tracking function in the imaging target area is further improved, and the target object can always be captured and tracked at the center position of the screen, resulting in a great practical effect of the apparatus of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of an automatic optical target tracking device according to the present invention, FIG. 2 is a circuit configuration diagram showing the point tracker circuit of FIG. 1, and FIGS. FIG. 5 is a circuit configuration diagram showing the area tracker circuit of FIG. 1. 1... Image pickup device, 2... Point tracker circuit, 3... Area tracker circuit, 4...
...Switcher, 5...Drive device, 6...
... Pan head.

Claims (1)

[Claims] 1 An image pickup device that performs television scanning, and the image signal output of this image pickup device is guided through a gate circuit to output a detection signal indicating the presence or absence of an edge signal of the target image, and the edge signal of the target image is detected. In this case, the gate position of the gate circuit is controlled to be at the edge signal detection position, and the position information of the target image is derived from the gate position information of the gate circuit, and the target image obtained in the next imaging frame is derived from the gate position information of the gate circuit. a point tracker circuit that outputs the difference from the position information of the target image as an error signal, and when an edge signal of the target image is not detected, repeatedly sweeps the gate of the gate circuit by a preset sweep width until an edge signal is obtained. and an area tracker circuit that detects the phase difference between the image signal obtained in the latest imaging frame and the image signal obtained in the previous imaging frame from which the image signal output of the image pickup device is guided, and outputs the detected phase difference as an error signal. is connected to this area tracker circuit and the point tracker circuit, and the detection signal is supplied as a switching signal, and when an edge signal of the target image is detected in the point tracker circuit, an error signal from the point tracker circuit is supplied. A switching device outputs an error signal from the area tracker circuit when an edge signal of the target image is not detected, and a switching device controls the error signal output from the switching device to change the imaging direction of the imaging device toward the target. An automatic optical target tracking device comprising a drive device for driving tracking.