JPH0614698B2 - Automatic tracking camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic tracking camera capable of automatically tracking and capturing a target subject.

[Background of the Invention]

Conventionally, in order to constantly observe a moving object (hereinafter, referred to as “subject”), an automatic tracking camera that automatically changes the direction of the imaging device, that is, the camera direction, along with the movement of the subject to track and image the subject has been proposed. Are known. In such an automatic tracking camera, it is necessary to recognize the subject first. For this reason, conventionally, an image obtained by picking up the subject using image processing technology (hereinafter referred to as the subject image)
Pattern recognition. That is, a pattern representing the characteristics of the subject is extracted from the shape and color of the subject, and the subject is recognized by comparing this pattern with a preset reference pattern.

Therefore, in order to perform such pattern recognition,
A large-scale computer is used, and the processing must be performed by a huge program, and the conventional automatic tracking camera is inevitably large-scaled and extremely expensive.

On the other hand, in recent years, a video camera has been remarkably popularized together with a video tape recorder, and has been widely used for industrial and home use. Moreover, such a video camera is used not only for the user to directly operate it to capture an image of a desired subject, but also as a sensor for a monitoring device. In this way, when using a video camera as a sensor, it is also meaningful to fix the video camera to monitor within a certain field of view, but the subject to be monitored may move. In a specific unmanned surveillance device in which the angle of view of the video camera is limited, it is necessary to provide the video camera with an automatic tracking function for tracking and imaging a moving subject.

However, as mentioned earlier, the conventional automatic tracking camera is large in scale and very expensive, so it is realistic to give an industrial or household video camera an automatic tracking function. It was impossible.

[Object of the Invention]

An object of the present invention is to provide a small-sized and inexpensive automatic tracking camera which has a greatly simplified structure except for the above-mentioned drawbacks of the prior art.

[Structure of Invention]

In order to achieve this object, the present invention detects a difference between images at a constant time interval, calculates a center of gravity of the difference between the images, and calculates the center of gravity of the difference between the images from the moving amount and the moving direction of the center of the captured image of the subject image. It is characterized in that the amount of movement and the direction of movement are detected to control the imaging device so that the subject image can be set within the reference area of the imaging screen.

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

FIG. 1 is a block diagram showing an embodiment of an automatic tracking camera according to the present invention, in which 1 is a subject, 2 is an imaging device, 3 is a camera circuit, 4 is a signal processing unit, and 5 is a control unit.

In the figure, an image pickup device 2 picks up an image of a moving subject 1 and generates an image signal. This image signal is supplied to the camera circuit 3 and subjected to predetermined processing such as amplification and the like,
It is supplied to the signal processing unit 4. The signal processing circuit 4 processes the supplied image signal to control the image of the subject 1 on the image pickup screen of the image pickup device 2 (the field of view projected on the image pickup surface), that is, the movement amount and the moving direction of the subject image. Generate a signal. This control signal is supplied to the control unit 5,
The control unit 5 controls the imaging device 2 to change its camera direction so that the subject image is in a predetermined area of the imaging screen (for example,
Track as if it were in the center.

FIG. 2 is a block diagram showing a specific example of the signal processing unit of FIG. 1, in which 6 is an input terminal, 7 is a separation circuit, 8 is an analog-digital conversion circuit, 9 is a frame memory, and 10 is a subtraction circuit. , 11 is a frame memory, 12 is an arithmetic unit, and 13 is an output terminal.

In the figure, an image signal from the camera circuit 3 (FIG. 1) is supplied from an input terminal 6 to a separation circuit 7 and separated into a luminance signal and a color signal. The separation circuit 7 includes the imaging device 2 (first
It is provided because the image signal obtained from Fig. 2) is generally a color video signal, but the fact that the same processing is performed for the luminance signal and the color signal and these signals are processed separately Since it does not have a particularly important meaning to the invention, it will be described below as an image signal.

The image signal from the separation circuit 7 is supplied to the analog-digital conversion circuit 8. The analog-digital conversion circuit 8 is
The image signal is digitized by setting M ₁ × M ₂ sample points per frame.

That is, as shown in FIG. 3 (A), M ₁ sample points are set for each of the M ₂ scan lines in the scan lines 14 of the frame F, and each sample point of the image signal is digitized. This is 1
For every 1 / M ₂ scanning lines of the total number of scanning lines in a frame, the image signal may be sampled and digitized every 1 / M ₁ period of the scanning line period.

Now, the position of the sample point 15 is (x, y) (where x and y are positive integers and 1 ≦ x ≦ M ₁ and 1 ≦ y ≦ M ₂ ), and the position of the sample point at the upper left corner is (1,1), the position of the sample point in the lower right corner
If (M ₁ , M ₂ ), the digitized image signal is Y
It can be represented by (x, y).

The image signal from the analog-digital conversion circuit 8 is supplied to the subtraction circuit 10 and the frame memory 9. The frame memory 9 stores the image signals for one frame, and the subtraction circuit 10
Subtracts the image signal of one frame stored in the frame memory 9 from the image signal of another frame at a fixed time interval from this frame, generates an image difference signal and stores it in the frame memory 11.

By the way, since the subject 1 (FIG. 1) is moving, the position of the subject image with respect to the imaging screen changes from moment to moment. For this reason, the image signal of the frame stored in the frame memory 9 and the constant time from this time. The waveform is different from the image signal of the frame of the interval according to the movement of the subject 1. As a result, the image difference signal obtained from the subtraction circuit 10 is the subject 1
Is a signal corresponding to the difference between the images of the above two frames due to the movement of the.

That is, in FIG. 4, the frames are sequentially obtained by the imaging scan of the imaging device 2. Now, the frames F ₁ , ...
..., frame F _N-2, the frame F _N-1, N of the frame F _N
Assuming frames, and, A an object image, B was an image of the stationary body, Subtracting the images of frames F ₁ from the image frame F _N, the image of the stationary body B is canceled, the frame F _N An image ΔF consisting of only the difference image A ′ between the subject image A and the subject image A in the frame F ₁ is obtained. The image difference signal stored in the frame memory 11 is a signal corresponding to the image ΔF. The image signal of frame F ₁ is Y ₁ (x, y), and the image signal of frame F _N is Y
_{Assuming that N} (x, y), Y _N (x, y) −Y ₁ (x, y) = ΔY (x, y) is the image difference signal. Note that x and y are the values defined in the explanation of FIG.

In this case, the image difference signal from the subtraction circuit 10 is stored in the frame memory 11 as a signal representing an absolute value.

The image difference signal stored in the frame memory 11 is read and supplied to the arithmetic unit 12 including a microcomputer.

The arithmetic unit 12 first uses the supplied image difference signal to calculate the center of gravity of the image represented by the image difference signal with the reference point (for example, the center point) of the imaging screen as the origin.

Therefore, first, the image difference signal ΔY (x, y) is binarized by setting 1 if it is larger than a predetermined threshold value and 0 if it is smaller than 2
If the binarized image signal is (x, y), the barycentric position (x _G , y _G ) is given by the following equation: Calculated by

By the way, the relationship between the moving amount and moving direction of the subject image on the imaging screen and the moving amount and moving direction of the center of gravity of the image represented by the image difference signal accompanying the movement of the subject is as follows.

1) The amount of movement of the center of gravity is 1/2 of the amount of movement of the subject image.

2) The moving direction of the center of gravity coincides with the moving direction of the subject image.

From this, the moving amount and moving direction of the subject image can be detected based on the moving amount and moving direction of the center of gravity.

Now, the position of the center point of the imaging plane and (x _0, y _0), the center point (x _0, y ₀₎ assuming a coordinate whose origin, the subject image is the center of the imaging screen including the origin Frame F ₁ when it is set to the area (hereinafter referred to as the reference area)
Assuming that the image signal of FIG. 4 is stored in the frame memory 9 (FIG. 2), the frame F after a certain time has passed.
_Since the position of the center of gravity of the image of the difference between the image of _N (FIG. 4) and the image of frame F ₁ is (x _G , y _G ), the center of gravity is (x _G −x ₀ ) It means that (y _G −y ₀ ) has been moved in the vertical direction. Accordingly, the object image is in the horizontal direction, the 2 × (x _G -x _{0) vertical, 2 × (y G -y 0} ) will be moved. The horizontal direction is the direction of the scanning line, and the vertical direction is the direction perpendicular to the scanning line.

Based on the data obtained as described above, the arithmetic unit 12 generates a control signal, and this control signal is supplied from the output terminal 13 to the control unit 5 (FIG. 1).

Therefore, in FIG. 1, the imaging device 2 is controlled and the camera direction can be changed so that the subject image is set in the reference area of the imaging screen. The signal processing unit 4 has stopped the processing operation, and when the camera direction is directed to the subject and the subject image is set to the reference area of the imaging screen, the signal processing unit 4 restarts the above-described processing operation.

In this way, the measurement of the movement of the subject and the control of the image pickup apparatus 1 are alternately repeated to perform automatic tracking.

According to this embodiment, it is possible to perform automatic tracking without using pattern recognition technology, and to configure with a circuit for processing signals and a relatively small arithmetic unit such as a microcomputer. The amount of information to be processed is very small because the amount of change in the image due to the movement of the subject is the processing target, the calculation processing can be performed quickly, and the frame memory used is relatively small. A device having a capacity can be used, the response speed is improved, and the device is small, lightweight and inexpensive.

The origin of the image capturing screen does not necessarily have to be the center point of the image capturing screen, and can be set at any point. Therefore, the subject image set by automatic tracking can be set at a desired position. it can.

FIG. 5 is an explanatory view of another embodiment of the automatic tracking camera according to the present invention, in which 16 is an image pickup screen and 17 and 18 are view angles.

In this embodiment, the movement of the object is detected using the angle of view, and the basic configuration is the same as in FIGS. 1 and 2.

In FIG. 5, two view angles 17 and 18 are assumed in the image pickup screen 16 of the image pickup apparatus 2 (FIG. 1). The center point of each of the field angles 17 and 18 is made to coincide with the center point of the imaging screen 16, the small field angle 17 is set to be the reference region, and the field angle 18 is set to a desired size. Therefore, automatic tracking is performed so that the subject image is always within the angle of view 17. Also, the angle of view
18 is used to determine whether or not the subject has moved, and is a region between the angle of view 17 and the angle of view 18 (hereinafter,
If an image difference signal occurs in the movement determination area), it is determined that the subject has moved.

FIG. 6 is a flow chart showing the operation of this embodiment, and the operation of this embodiment will be described with reference to FIGS. 2, 5, and 6.

As described in the previous embodiment, first, the frame memory 9
The image signal of one frame is stored in (step 19), and the subtraction circuit 10 subtracts the image difference signal from the image signal of one frame after a fixed time.
Obtained and stored in the frame memory 11 (process 20). next,
The arithmetic unit 12 reads out the addresses corresponding to the movement determination area between the field angles 17 and 18 of the frame memory 11, and when the image difference signal is written in these addresses, that is, there is "1" data. Sometimes a flag is set (process 21).

Next, it is determined whether or not the flag is set (determination 22). If the flag is not set, it is determined that the subject has not moved, and the process returns to the process 20. in this case,
The memory 9 stores the previously-stored one-frame image signal as it is, and further obtains an image difference signal from the one-frame image signal after a predetermined time.

If the flag is set and it is determined to be "YES" in determination 22, it is determined whether or not there is an instruction to end the automatic tracking operation (determination 23). If there is no such instruction, in image 18, The same processes as those for calculating the center of gravity, detecting the moving amount and moving direction of the subject image, and setting the camera direction under the control of the image pickup apparatus 2 (FIG. 1) are performed as in the previous embodiment (process 24). When the setting of the camera direction is completed, the process returns to step 19 and the same operation is performed again.

When a series of these operations are repeated and there is an instruction to end the automatic tracking operation, it is determined to be “YES” in determination 23 and the automatic tracking operation is stopped.

In this embodiment, since the image difference signal within the angle of view 18 is processed, the amount of information processed is much smaller than when processing the image difference signal over the entire imaging screen,
The automatic tracking operation is performed more quickly, and the frame memories 9 and 11 (FIG. 2) having a smaller capacity can be used. Also, since the processing range of the image difference signal is limited to a small range within the angle of view 18,
The influence of noise on the arithmetic processing for detecting the subject image is significantly reduced, and the accuracy of automatic tracking is greatly improved.

Further, in this embodiment, the movement determination area between the angles of view 17 and 18 is received to detect the movement of the subject image, and after the movement of the subject is detected, the arithmetic processing for setting the camera direction is performed. As soon as it is determined that the subject has not moved, the image difference signal indicating that the next frame is the frame stored in the frame memory 9 (FIG. 2) is detected. Then (that is, when the subject image exceeds the angle of view 17), it is immediately detected, and the response characteristic of automatic tracking is improved.

It should be noted that the angles of view 17 and 18 can be set to arbitrary positions on the imaging screen 16 if the centers thereof match each other, and thus the range of capturing the subject can be set arbitrarily.

FIG. 7 is a block diagram showing a main part of still another embodiment of the automatic tracking camera according to the present invention, in which 25 is an automatic focus adjusting device, and the parts corresponding to those in FIGS. 1 and 2 are the same. A reference numeral is given and a part of the description is omitted.

In this embodiment, when the moving direction of the moving body 1 (FIG. 1) is close to the image pickup device 2 (FIG. 1), the zoom magnification is changed to obtain wide-angle image pickup, or the angle of view is enlarged. The subject image can be limited to a predetermined size by assuming the angles of view 17 and 18 in the imaging screen 16 as in the embodiment described above with reference to FIG. .

FIG. 8 is a flow chart showing the main part of the operation of this embodiment. The operation of this embodiment is represented by the flowchart of FIG. 6 except that the processing 24 performs the processing shown in the flowchart of FIG.

In FIGS. 5, 7, and 8, as described in the previous embodiment, when it is detected that the subject image is moving due to the movement determination area between the field angles 17 and 18, the arithmetic unit
At 12, a process of detecting in which part of the movement determination area the image difference signal exists (process 26). That is, the movement determination area is divided into some partial movement determination areas, and in process 26, the presence or absence of an image difference signal is detected for each partial movement determination area.

Next, the calculation processing for calculating the center of gravity of the image difference signal for the angle of view 17 and detecting the moving amount and moving direction of the subject image is performed as described in the previous embodiment, and the control based on the calculation result is performed. The signal is supplied to the control unit 5.

Next, the arithmetic unit 12 determines, based on the detection result of the process 26, whether or not the image difference signal exists in the partial movement determination regions in a plurality of directions opposite to the angle of view 11 (determination 28 ). This determination 28 is to detect whether or not the moving direction of the subject 1 (FIG. 1) is the direction of the imaging device 2 (FIG. 1). If this determination is “NO”, the subject 1 Does not approach the image pickup apparatus 2, and the process returns to the process 19 in FIG.

On the other hand, if the determination 28 is “YES”, calculation processing for calculating the zoom magnification is performed (processing 2
9). This calculation process is to obtain the distance from the center point of the angle of view 17 after changing the camera direction in process 27 to the farthest sample point (FIG. 3) of the subject image.

Now, the movement vector of the subject image is (Δx, Δy), the angle of view
Assuming that the coordinates of the center point of 17 are (x _c , y _c ) and the coordinates of each sample point of the subject image before processing 27 are (x, y), the subject image is moved by (−Δx, −Δy) by processing 27. Therefore, the distance d from the center point of the angle of view 17 of each sample point of the subject image after the process 27 is Is. When the distance d of each sample point is calculated from this equation, the maximum distance dmax of these is next selected. The sample point for this dmax is the sample point farthest from the center point of the angle of view 17 of the subject image after setting the camera direction.

Since the process 29 is performed only after the image difference signal is detected in the movement determination region between the angle of view 17 and 18, the image difference signal in this movement determination region is regarded as the image signal of the subject image before the process 27. Therefore, x and y are the coordinate values of the sample points in the movement determination area. Also, Δx and Δy are the processing
It is obtained from the moving amount and moving direction of the subject image detected by 27.

From the dmax thus obtained and the zoom magnification from the automatic focusing device 25, the zoom magnification is calculated so that the sample point corresponding to dmax falls within the angle of view 17, and as a result,
A control signal is supplied to the automatic focus adjustment device 25, and the zoom lens is controlled so that the entire subject image fits within the angle of view 17. Then, when the control of the zoom lens is completed, the process returns to the process 19 of FIG.

In this embodiment, the frame written in the frame memory 9 is renewed for each calculation process including the process for detecting the movement of the subject image in the calculation device 12 (that is, in FIG. If the result of the determination 22 is "NO", the process returns to step 19.) This is to prevent an error in the zoom magnification.

In this embodiment, the subject image can be stored within the angle of view 17 regardless of the distance of the subject from the image pickup device, and the presence or absence of movement of the subject image can be accurately detected. The amount of movement and the direction of movement can also be detected accurately, and automatic tracking can be performed accurately regardless of the moving direction of the subject.

Although frame memories are used as the memories 11 and 12 in the above embodiments, field memories may be used.

〔The invention's effect〕

As described above, according to the present invention, there is no need for complicated processing, there is no error even with a simple circuit configuration, and moreover, quick automatic tracking can be performed, which is small, lightweight and inexpensive, It is possible to provide an automatic tracking camera having an excellent function that the above-mentioned conventional art does not have.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an automatic tracking camera according to the present invention, FIG. 2 is a block diagram showing a specific example of the signal processing unit of FIG. 1, and FIG. 3 (A) is an image of one frame. Of FIG. 3, FIG. 3 (B) is an explanatory view showing the sampling points of the image signal in the scanning line of FIG. 3 (A), and FIG. 4 is for the image difference signal generation of FIG. 5 is an explanatory view of another embodiment of the automatic tracking camera according to the present invention, FIG. 6 is a flowchart showing the operation of the embodiment of FIG. 5, and FIG. 7 is according to the present invention. FIG. 8 is a block diagram showing the main part of still another embodiment of the automatic tracking camera, and FIG. 8 is a flowchart showing the main part of the operation of the embodiment of FIG. 2 ... Imaging device, 3 ... Camera circuit, 4 ... Signal processing unit, 5 ... Control unit, 9 ... Frame memory, 10 ... Subtraction circuit, 11 ... Frame memory, 12 ... Computing device, 16 ... Imaging screen , 17, 18 …… Angle of view 25 …… Automatic focus adjustment device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiro Kinugasa 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Home Appliances Research Laboratory, Hitachi, Ltd. (72) Inventor Yoshiaki Mochimaru 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa In the Tate Video Engineering Co., Ltd. (72) Inventor Noritaka Narita 292 Yoshida-cho, Totsuka-ku, Yokohama City, Kanagawa Prefecture In the Nititsu Video Engineering Co., Ltd. (56) Reference JP 54-89417 (JP, A) JP 54 -161821 (JP, A)

Claims (1)

[Claims] 1. An automatic tracking camera, which measures a moving amount and a moving direction of an object to be tracked and is controlled so that the object can be imaged according to the measurement result, is supplied with an image signal obtained from an imaging device at a constant time interval. Difference signal detection means for obtaining an image difference signal representing the difference between the images, and a predetermined area of the image pickup screen of the image pickup device as a first angle of view,
Movement detecting means for detecting a difference between images outside the first angle of view and within a second angle of view including the first angle of view; An arithmetic means for calculating the barycentric position of the difference between the images and detecting the moving amount and moving direction of the subject image on the imaging screen can be provided, and the image of the subject can be set within a predetermined area of the imaging screen. An automatic tracking camera having the above-mentioned configuration.