JPH0586701B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to an automatic tracking device for a moving subject in an automatic focus detection or automatic focus adjustment device for a camera, particularly a video camera, and is particularly capable of tracking a subject moving at high speed. Concerning the means to do so.

(Background Art) Regarding the automatic focus detection method using the video signal of a video camera, for example, US Pat.
Many proposals have been made, including Publication No. 17172. Regarding the so-called mountain-climbing control method, which is one of the above methods, see page 21 of "NHK Technical Research" Vol. A method that combines hill-climbing control and a rear focus drive lens is described in the paper "Automatic Focus Adjustment of Television Cameras," and in the Technical Report of the Television Society of Japan on November 29, 1981, "Contour Detection Autofocus" is written by Hankan et al. Each method has been announced in detail as "Cass method".

By the way, in this type of device, the distance measurement field of view is fixed at the center of the photographing screen as shown in Figure 1A, so the object to be focused on (hereinafter referred to as the target object) (hereinafter referred to as the target object) is person in the example)
If the camera moves, an object at a different distance from the target subject (a house in this example) will come into focus, and the target subject, a person, will become blurred. Note that FIG. 1 and FIG. 2, which will be described later, show screens when distance measurement is performed with a camera equipped with an automatic focusing device with negligible difference.

(Purpose) The present invention eliminates the above-mentioned drawbacks of conventional automatic focus detection devices, automatically detects the moving position of a moving subject, moves the distance measurement field of view to track the movement of the subject, and focuses the subject. It is an object of the present invention to provide an automatic tracking device equipped with a means that enables tracking of a subject moving at high speed when performing detection or focus adjustment.

(Explanation based on Examples) Hereinafter, the means taken in this invention to achieve the above object will be exemplified and explained with reference to FIGS. 2 to 12 and the like. The following description will discuss an example of extracting the features of a tracked object using color signal information, an overview of the automatic tracking focus detection function to which this invention is applied, an automatic tracking focus detection device to which this invention is applied, and an example of the invention. The sequence of standard color update operations associated with embodiments of automatic tracking devices and embodiments of the present invention will be described. In carrying out this invention, feature extraction of the object can be performed using not only the color signal information described above, but also luminance signal information and other information such as shape, temperature, or characteristic contrast in the object. .

(Outline of automatic tracking focus detection function to which the present invention is applied) (Figures 2 to 5) First, an overview of an example of the automatic tracking focus detection function to which the present invention is applied will be explained. The target subject (person) is shown in Figure 2A.
When moving to the upper right of the viewfinder screen while maintaining the same distance as shown in Figure 2A, the tracking means described later automatically detects the movement of the subject and changes the distance measurement field of view to the upper right of the viewfinder screen.
As shown in the figure, the camera tracks the movement of the subject and moves it.
Focus detection or focus adjustment is performed at this moving position. That is, some parameters representing the characteristics of the object, such as the colors of the object and the background, are extracted with respect to the tracking field of view set by the tracking means, and the extracted characteristics are stored;
Based on the memorized features and the newly extracted features of the subject, it is possible to detect whether or not the subject has moved, and if the subject has moved, the direction or position of movement, and the tracking field of view can be used to determine the movement of the subject. The distance measuring field of view is moved in the same positional relationship as the tracking field of view is moved. Therefore, FIG. 2 can also be regarded as showing the relationship between the movement of the subject and the movement of the tracking field of view. Note that the tracking field of view is one of the means for determining the movement of the subject, and is normally displayed on a viewfinder screen or the like like the distance measurement field of view, and the subject is not observed through this. Furthermore, if the tracking field of view were to be displayed on the screen, the tracking field of view and the ranging field of view would be displayed in the same positional relationship on the screen as described above, but the sizes of these can be adjusted depending on the tracking field of view as necessary. Alternatively, either distance measurement field of view can be made larger.

In Figure 2 A, the distance measurement is the same, so there is no need to adjust the focusing lens of the photographic lens, but in Figure 2 B, the distance changes as the subject moves to the upper right of the screen. Therefore, the focusing lens moves according to the distance measurement results. Therefore, the size of the tracking field of view is changed by a tracking gate size determining means, which will be described later, and is always maintained at a size suitable for the subject, and focus detection or focus adjustment is performed in this state. Here, since the movement between the subject and camera is relative, the tracking effect described above applies not only when the camera is fixed and the subject moves, but also when the subject stops and the camera moves. Also, the size of the tracking field of view can be adjusted not only when the subject distance changes, but also when changing the focal length of the lens.

In principle, the tracking field of view has a two-dimensional extent, but for the sake of simplicity, here, as shown in Figure 3A, the tracking field of view has a one-dimensional extent extending in the horizontal direction. Suppose there is. It is also assumed that the tracking visual field is divided into three parts A, B, and C (each part is hereinafter referred to as a pixel). In order to configure a two-dimensional tracking field of view, it is sufficient to provide, for example, pixels located above and below pixel B or A, B, and C in the same figure as the center. As shown in FIG. 4, the color difference signals (R-Y) and (R-Y) obtained as time-series signals from each pixel are connected to integration circuits 100a and 100b, and a sample and hold (S/H) circuit 101a, respectively. , 101b and A/D conversion circuits 102a, 102b perform integration, sample hold, and A/D conversion processing, and store them in memories 103a, 103b, respectively.
When these stored values are plotted on the rectangular coordinates (RY) and (BY) for each pixel A, B, and C, they are displayed as shown in FIG. 5, for example. In the figure, points A ₀ , B ₀ and C ₀ represent signals obtained from pixels A, B and C in FIG. 3A, respectively. Here, it is assumed that pixel B provides a signal representing only, for example, the clothing of a person who is the subject, and pixels A and C provide a signal in which signals representing the clothing of the subject and the background are added together. Furthermore, assume that the background colors on the left and right sides of the subject in the figure are different. Therefore, the point
A ₀ and C ₀ have different positions on the color difference signal coordinates.

Next, when the subject shown in Figure 3A moves to the right within the screen as shown in Figure 3B, the ratio of the subject to the background within pixels A and C changes, resulting in The resulting signal is shown in Figure 5.
They change as shown in A ₁ and C ₁ respectively. on the other hand,
Since pixel B remains within the object as shown in FIG. 3B, the signal obtained from pixel B will hardly change if the clothing is substantially monochromatic. Therefore, here, for simplicity, B ₁ =
Let B be ₀ . In this case, as shown in Figure 5, the point
C ₁ approaches point B ₀ (=B ₁ ), and point A ₁ approaches point B ₀ (=B ₁ )
As it moves away from , line segment B ₁ C ₁ becomes smaller than line segment B ₀ C ₀ , and line segment A ₁ B ₁ becomes larger than line segment A ₀ B ₀ . Conversely, line segment B ₁ C ₁ becomes larger than line segment B ₀ C ₀ ,
If the line segment A ₁ B ₁ becomes smaller than the line segment A ₀ B ₀ , it means that the subject is moving to the left in FIG. 3B.

If the background color is the same on both sides of the subject, when the subject moves to the right in Figure 3B within the screen, the above point _A1 will be located on the extension of the line segment _{A0B0 .} , and the point C ₁ is located on the line segment B ₀ C ₀ . This invention can be applied to either of the above cases.

(Automatic tracking focus detection device to which this invention is applied) (FIGS. 6 and 7) FIG. 6 shows an example of an automatic tracking focus detection device to which this invention is applied, and in the figure, the photographing optical system is It consists of a focusing lens 1, a zoom lens 2, an aperture 3, and a relay lens 4, and a subject image is received on an image sensor 5 (eg, C, C, D). 6 is a clock signal generation circuit, the output of which is sent to a frequency divider 7.
The frequency is divided to a required ratio, and this frequency-divided output controls an image sensor drive circuit 8, a tracking gate setting circuit 11, and a ranging gate setting circuit 16, which will be described later. The image sensor 5 is driven by an image sensor drive circuit 8 to output a time-series signal, and this output is subjected to necessary synchronization signal synthesis, modulation, and correction processing in a signal processing circuit 9 to form an output video signal, for example, an NTSC signal. be done. Since these processes are well known to those skilled in the art, detailed explanation thereof will be omitted. Note that in the following description, it is assumed that the output video signal is an NTSC signal.

The signal processing circuit 9 simultaneously processes a color difference signal (R-
Y) and (B-Y) as the tracking gate (corresponding to the tracking field of view) setting circuit 11 and ranging gate setting circuit 1
Output to 6. The output of the tracking gate setting circuit 11 is supplied to a color detection circuit 12 to detect the color of the subject, and this is stored in the memory 13 via manual mechanical input means such as a switch (not shown). Note that the color detection circuit 12 includes an integration circuit 100, a sample hold circuit 101, and an A/D conversion circuit 102 shown in FIG. The above processing is performed according to the average value during 1/60 second, which is the period of one field of the television signal, or during a period of several fields thereof. The following explanation will be given assuming that both are processed in one field period. Next, in the first field, the newly extracted signal and the signal stored in the memory 13 are processed by the movement determination circuit 14, and the presence or absence of movement of the subject and the direction of movement of the subject are detected. If movement occurs, the tracking gate setting circuit 11 is controlled by the predetermined gate movement circuit 15 to move the tracking field of view, and the same calculation is performed in the next field, and the above is repeated until tracking is completed. Repeat the process.

When tracking is completed, the gate moving circuit 15 sets the ranging field of view set by the ranging gate setting circuit 16 to the same relative position as the tracking field of view, and the video signal within this ranging field of view (signal processing circuit 9 output) in the automatic focus adjustment (AF) circuit 17,
For example, focus detection is performed by a known means such as mountain climbing control, and the motor M is driven by the output thereof.
The position of the focusing lens 1 is controlled.

In Figure 6, P ₁ is a position sensor that detects the absolute position of the focusing lens 1 (corresponding to the subject distance), and P ₂ is the absolute position of the zoom lens 2 (corresponding to the focal length). Based on these signals, the tracking gate size determining circuit 10 controls the tracking gate setting circuit 11 and the distance measurement gate setting circuit 16 to determine the size of the tracking field of view and the distance measurement field of view, respectively. stipulate.

FIG. 7 shows the color detection circuit 12 and memory 13 described above.
6 shows the details of the movement determination circuit 14, and the (R-Y) signals and (B-
Y) From the signal, the length D _A0 of the line segment A ₀ B ₀ on the (R-Y) and (B-Y) coordinates in FIG. 5 is determined by the distance calculation circuit 21.

Claims (1)

[Scope of Claims] 1. Imaging means for photoelectrically converting a subject image formed on an imaging plane and outputting an imaging signal; and within the imaging plane, at least a central region and on both sides thereof for tracking the subject image. a setting means for setting a tracking field of view divided into three regions consisting of adjacent regions; a setting means for storing a signal obtained from the central region among the divided regions as a signal representing the characteristics of the subject image; extracting means for outputting, at predetermined intervals, difference signals between the signals obtained from each of the adjacent regions on both sides of the area and the signal from the central region; and means for detecting relative movement between the subject image and the tracking field of view at the predetermined period based on the subject image, and moving the set position of the tracking field of view to follow the subject image. Automatic tracking device for cameras. 2. The automatic tracking device in a camera according to claim 1, wherein the signal obtained from the central area is fixed and stored as a signal representing the characteristics of the object to be tracked at the time of designation.