JPS60254108A - Automatic tracking device of camera - Google Patents

Abstract

PURPOSE:To perform stable tracking operation without any influence of noise by extracting and integrating a signal which shows features of a subject to be tracked, and detecting the relative movement of the subject from the integral value. CONSTITUTION:A tracking gate size determining circuit 10 controls a tracking gate setting circuit 11 and a range finding gate setting circuit 16 on the basis of signals from a position sensor P1 which detects the absolute position of a focusing lens 1 and a position sensor P2 which detects the absolute position of a zoom lens 2. Then, integrating circuits concluded in a color detecting circuit 12 integrates color difference signals (R-Y) and (B-Y) respectively and the integral signals are stored in a memory 13. Then signals (R-Y) and (B-Y) which are extracted and integrated newly are compared with the signals stored in the memory 13 by a movement decision circuit 14 to detect whether the subject moves or not, and the moving direction or moving position when the subject moves.

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, especially a video camera, and in particular, to a device for stably tracking a moving subject without being affected by noise. It relates to the means by which an action can be performed.

(Background Art) Regarding an automatic focus detection device that uses a video signal from a video camera, for example, US Pat.
Many proposals have been made, such as Publication No. 172.

Regarding the so-called mountain-climbing control method, which is one of the above-mentioned methods, see "TV camera using mountain-climbing servo method" by Ishida et al., p. 21 of "rNHK Technical Research", Vol. 17, No. 1 (volume No. 86) (published in 1966). "Automatic Focus Adjustment", and a method that combines this mountain climbing control with a rear focus drive lens was published in November 1981.
In the Technical Report of the Television Society of Japan on April 29th, Hankan et al. announced each method in detail as a ``contour detection autofocus 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 1 (A), so as shown in Figure 1 (B), the object to be focused on (hereinafter referred to as the target) is If the subject (in this example, a person) moves, an object at a different distance from the target subject (in this example, a house) will be in focus, and the target subject, the person, will become blurred. be. In addition, Figure 1 and Part 2 below
The figure shows a screen when distance measurement is performed using 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 movement of a moving subject, moves the distance measurement field of view to track the movement of the subject, and focuses the subject. An object of the present invention is to provide an automatic tracking device that operates stably without being affected by noise 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 7, etc. The following description will be made regarding an example in which features of a tracked object are extracted using color signal information, in the order of an overview of an automatic tracking focus detection function to which the present invention is applied and an embodiment of an automatic tracking device of the present invention. In carrying out this invention, feature extraction of the object is performed not only on the above color signal information but also on
This can be done using brightness signal information and other information such as shape, temperature, or characteristic contrast in the object.

(Outline of automatic tracking focus detection function to which this invention is applied) (
(Figs. 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. When the subject moves toward the upper right of the screen while maintaining the same distance as shown in A), the tracking means described later automatically detects the subject's movement, and the distance measurement field of view is adjusted as shown in Fig. 2 (A). The object is tracked and moved, and focus detection or focus adjustment is performed at this movement position. That is, some parameter representing the feature of the subject, such as the color of the subject and the background, is extracted with respect to the tracking field of view set by the tracking means, this extracted feature is stored, and the newly extracted feature is combined with the stored feature. The tracking field of view is moved to follow the movement of the subject by detecting whether the subject is moving or not, and if the subject moves, the moving direction or moving position based on the subject's characteristics. As the field of view moves, the distance measurement field of view is moved in the same positional relationship. 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 a subject, and is normally displayed on a finder screen or the like like a 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 is the same, so the focusing lens of the photographic lens is not adjusted, but in Figure 2 (CB), the subject moves to the upper right of the screen and the distance also changes. Since the distance changes, 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 can occur not only when the camera is fixed and the subject is moving, but also when the subject is stationary and the camera is moving, or when both are moving. It functions effectively even when moving together, and 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.

The tracking field of view is, in principle, a two-dimensional field of view, but to simplify the explanation, it is shown in Fig. 3 (A).
Assume that the tracking field of view has a one-dimensional extension extending in the horizontal direction as shown in FIG. Also, the tracking field of view is A, B,
Suppose that it is divided into three parts (hereinafter each part is referred to as a pixel) of C. In order to construct a two-dimensional tracking field of view, for example, pixels positioned above and below pixel B or A, B, and C in the figure may be provided as the center. Color difference signals (R-Y) and (B-Y) obtained as time-series signals from each pixel above
As shown in FIG.
, 100b, sample hold (S/H) circuit 1ota
, 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 (RY) and (BY) rectangular coordinates for each pixel A, B, and C, they are displayed as shown in FIG. 5, for example. In the diagram A o
Each point of l' B 5 and Co is shown in Fig. 3 (A
) represents signals extracted from each pixel of A, B, and C. Here, it is assumed that from pixel B, a signal representing only the clothing of the subject, for example, is extracted, and from pixels A and C, a signal in which signals representing the clothing of the subject and the background are added together is extracted. Furthermore, assume that the background colors on the left and right sides of the subject in the figure are different.

Therefore, points A and Co are at different positions on the color difference signal coordinates.

When the subject shown in Fig. 3 (A) moves to the right within the screen as shown in Fig. 3 (CB), the ratio of the subject to the background in pixels A and C changes, and as a result, pixels A and C change. The signals obtained from C vary as shown in FIG. 5 A1 and C1, respectively. On the other hand, since pixel B remains within the object as shown in FIG. 3(B), the signal obtained from pixel B hardly changes if the clothing is almost monochromatic. Therefore, here, for simplicity, it is assumed that B1=B. In this case, as shown in Figure 5,
Point C1 approaches point Bo (=Bx), and point A1 approaches point Bo (
-Bt), so the line segment BIC1 becomes the line segment BoC
, becomes smaller, and line segment AOB1 becomes larger than line segment AOB. Conversely, if the line segment BICI becomes larger than the line segment BOCo and the line segment AIB becomes smaller than the line segment AOBO, it means that the subject is moving to the left in FIG. 3(B). Assuming that the background color is the same on both the left and right sides of the subject, when the subject moves to the right in Figure 3 (B) within the screen, the above point A1 will be located on the extension of the line segment AoB. One point C1 occupies a position above the line segment BOC. This invention can be applied to either of the above cases.

(Embodiment of the automatic tracking device of this invention) (Figs. 6 and 7)
Figure) Figure 6 shows an embodiment of the automatic tracking device of the present invention,
In the figure, the photographing optical system includes a focusing lens I, a zoom lens 2, an aperture 3, and a relay lens 4, and a subject image is received on an image sensor 5 (for example, C0C, D, etc.). 6
is a clock signal generation circuit, whose output is frequency-divided by a frequency divider 7 to a required ratio, and this frequency-divided output is sent to an image sensor drive circuit 8, a tracking gate setting circuit 11, and a ranging gate setting circuit 16, which will be described later. Granted. 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. These treatments are well known to those skilled in the art;
A 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 color difference signals (RY) and (
B-Y) is output to the tracking gate (corresponding to the tracking field of view) setting circuit 11 and the ranging gate setting circuit 16. The output of the tracking gate setting circuit 11 is supplied to the color detection circuit 12,
The color of the object is detected and 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 seconds, which is the period of one field of the television signal, or during a period of several fields thereof. In the following, both will be explained as being processed in one field period.

In the next field, the newly extracted signal and the signal stored in the memory 13 are compared in 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 there is movement, the tracking gate setting circuit 11 is controlled by the gate movement circuit 15 to move the tracking field of view, perform the same calculation in the next field, and repeat the above process until tracking is completed. return.

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) automatic focus adjustment (A
F) The circuit 17 performs focus detection by known means such as hill climbing control, and its output drives the motor M to control the position of the focusing lens l.

In Fig. 6, Pl is a position sensor that detects the absolute position of the focusing lens l (corresponding to the subject distance), and P2 is a position sensor that detects the absolute position of the zoom lens 2 (corresponding to the focal length). The tracking gate size determining circuit 10 controls the tracking gate setting circuit 11 and the ranging gate setting circuit 16 based on these signals, and determines the sizes of the tracking field of view and the ranging field of view, respectively. Now, the focal length of the photographic lens is f, and the subject distance is R.
1 The longitudinal dimension of the imaging surface is y, and the tracking field of view length (Fig. 3 (
If we set the total length of pixels A, B, and C in A) as a, and the length of the tracking field of view on the subject as W, nz''=, !=, then k
=fW/Ryc' is given. To give a numerical example, f=
30 mm, R = 5000 mm, y = 8.8 mm, and when the tracked subject is an adult and W = 500 mm, then = 0.34. Here, y is an image sensor, for example C, C.

Since W is determined by the size of D and the object to be tracked, if k is calculated by the tracking gate size determination circuit lO from the output values of the position sensors P1, P20') using the above formula, it will always be optimal for the object. A tracking field of view of the size can be obtained.

FIG. 7 shows details of the color detection circuit 12, memory 13, and movement determination circuit 14 described above, and shows the (
Distance calculation circuit 21 from R-Y) signal and (B-Y) signal
Accordingly, the line segment AoB on the (R-Y) and (B-Y) coordinates in FIG.

The lengths DAO and BO are determined and stored in the memory 22. From the next field signal, DAI-Bl
Or DAl, BO is considered.

Here, for the sake of simplicity, if we consider the case where B, = B o, DAl, B1'' DAl, BO, and the divider 23 calculates DAl, B1/DAO, BO. This value is The comparator circuit 25 compares the first threshold set by the threshold setter 24 with the first threshold, and if there is a change exceeding the threshold, outputs "1" to the movement determination circuit 14.Similarly, the distance calculation From circuit 31 to comparison circuit 35
Dct, s1/Dco, B by the circuit up to.

is calculated, and if there is a change exceeding the second threshold value, the comparison circuit 35 outputs "1'" to the movement determination circuit 14. To explain a specific numerical example, in the example shown in FIG. 5, both the first and second thresholds are set to 2, and DAl, B1/DAO, BO=2.2°DCl, B1/
Since DCO, BO=0.36, only the comparison circuit 25 outputs "I II". In this case, the movement determination circuit 1
4 sets the gate setting timing for a predetermined time (for example, NTSC
In the case of this method, a signal that is delayed by about 17125 times one horizontal scanning period is generated. Conversely, if only the comparison circuit 35 outputs '1', the movement determination circuit 14 generates a signal that advances the gate setting timing by the predetermined time described above. Therefore, in response to the output l'' of the comparator circuit 25 or 35, the movement determination circuit 14 generates a signal that changes the gate setting timing by, for example, the above-mentioned predetermined time, and in response to this signal, the gate movement determination circuit By controlling the gate setting circuits 11 and 16 as described above, the tracking field of view and the ranging field of view can be moved in the direction in which the subject is moving, and focus detection can be performed at that position. Memories 22 and 3 are displayed at the new position where the tracking field of view has moved after tracking.
It is also possible to sequentially update the values stored in 2 and repeat the same process.

As described above, in the embodiment of the present invention shown in FIGS. 6 and 7, the color difference signal (R-
Y) and (B-, Y) are respectively integrated, and the integrated signals are stored in the memory 13, and the newly extracted and integrated (R-Y) and (B-Y) signals and the memory The movement determination circuit 14 compares the signal stored in 13 with the signal stored in 13, and detects whether or not the tracked subject has moved, and if the tracked subject moves, the moving direction or moving position, so that it is not affected by noise. It is possible to perform stable tracking operations without any problems.

(Effects) As described above, according to the present invention, there is provided a means for extracting a signal representing the characteristics of a tracked subject, a means for integrating the extracted signal, and a means for integrating the signal based on the integrated signal. Since the camera includes means for detecting relative movement of the tracked object, stable tracking operation can be performed without being affected by noise.

[Brief explanation of drawings]

Figure 1 shows the relationship between the distance measurement field of view and the subject image in a conventional camera. Figure 1 (A) shows when the distance measurement field and the subject image match, and Figure 1 (B) shows the relationship between the distance measurement field of view and the subject image. Figure 2 shows the relationship between the distance measurement field of view and the subject image in a camera embodying the present invention. Figure 3 (B) is an explanatory diagram showing the case where the subject moves within the screen and the distance becomes distant, and Figure 3 (A)
is an explanatory diagram showing the relationship between the tracking field of view and the subject image when the tracking field of view is divided in an automatic tracking device implementing the present invention, and (B) is a state in which the subject moves within the screen in the same figure (A). A block diagram of a device for processing signals obtained from the divided field of view in Figure 3;
FIG. 5 is an explanatory diagram showing a situation in which the signals obtained from the device in FIG. 4 are plotted on a two-dimensional plane, and FIG. 6 is a combination of the optical system and electrical control system in an embodiment of the automatic tracking device of the present invention. FIG. 7 is a block diagram showing details of the main parts of the apparatus shown in FIG. 6. Explanation of symbols ■: Focusing lens, 2: Zoom lens, 5: Image sensor,
8: Image sensor drive circuit, 9: Signal processing circuit, 11: Tracking gate setting circuit, 12: Color detection circuit, 13: Memory, 1
4: movement determination circuit, 15: gate movement circuit, 16: ranging gate setting circuit, 17: automatic focus adjustment circuit.

Claims (1)

[Claims] Means for extracting a signal representing characteristics of a tracked object; means for integrating the extracted signal; and means for calculating the relative movement of the tracked object based on the integrated signal. An automatic tracking device in a camera, comprising: means for detecting;