JPH06230454A - Camera provided with object tracking function - Google Patents

Abstract

PURPOSE:To track an object again without missing the object after finishing exposure even when the object is moved in the midst of controlling the exposure in regard to a camera provided with an object tracking function by which the object moving in a field is automatically tracked. CONSTITUTION:This camera is provided with a photometry means 10 performing photometry by dividing the field into plural areas and outputting plural pieces of photometry information concerning the luminance of the field, an object tracking means 12 detecting the movement of the object by using output from the means 10 and tracking the object, and a movement predicting means 15 perdicting and calculating the movement of the object according to output from the means 12 while the photometry of the field can not be performed by the means 10 and obtaining the position of the object after the photometry of the object is restarted by the means 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera having an object tracking function capable of automatically tracking an object moving in a field.

[0002]

2. Description of the Related Art An apparatus for automatically tracking a moving object to perform focus detection or focus adjustment is disclosed in, for example, JP-A-60
-249477 (Title of the invention; Automatic tracking focus detection device).

This device, as shown schematically in FIG.
The subject light that has passed through the taking lens 20 is imaged on an image pickup device 21 having a CCD structure, and photoelectrically converted electric signals are taken out in time series and supplied to a signal processing circuit 22.
Converted to a standard video signal and output.

At the same time, a color difference signal is output from the signal processing circuit 22, a color detecting circuit 23 extracts color information as a characteristic of the target object, and the color information is stored in the tracking means 24. The tracking means 24 compares the stored color information with the newly extracted color information for each field, determines whether or not the subject has moved based on the comparison result, and when the target subject has moved, the movement is performed. The target object is automatically tracked by tracking, moving the distance measuring field of view, and performing focus detection and focus adjustment.

The determination of the movement of the target subject based on the color information is
Although detailed description is omitted, three consecutive pixels are set as the tracking visual field, and color difference signals (RY), (B-
Y) is plotted on Cartesian coordinates (RY) and (BY), and the change in the position on the coordinates is performed.

[0006]

By the way, when the conventional subject tracking technology described above is applied to a single-lens reflex camera using a silver salt film, electronic image information for subject tracking is obtained from the silver salt film. Therefore, it is necessary to separately provide a photometric element for tracking an object.

Since the single-lens reflex camera is constructed so that the light flux passing through the photographing lens is reflected by the quick return mirror and guided to the photographer's eye through an optical system such as a pentaprism installed at the top of the camera. The photometric element needs to be installed at a position where the light flux passes through the pentaprism.

Therefore, the light flux reflected by the quick return mirror is guided to the photometric element during the preparation for photographing, so that the subject can be tracked. However, during the exposure control, the quick return mirror rises and the light flux is reflected on the film surface. Since the light beam does not reach the photometric element, the subject tracking becomes temporarily impossible. Therefore, if the subject moves during this time, the subject will be lost after the exposure ends,
The inconvenience that tracking becomes impossible occurs.

It is therefore an object of the present invention to provide a camera having a subject tracking function that enables the subject to be tracked again without losing sight of the subject even after the subject moves during exposure control.

[0010]

The camera according to the present invention comprises:
The field of view is divided into a plurality of areas for photometry, and a plurality of photometric information that outputs a plurality of photometric information regarding the brightness of the field of view and the output of this photometric means are used to detect the movement of the subject and track the subject. Movement to calculate the subject's movement based on the output of the subject tracking means while the subject tracking means and the photometry means cannot measure the field, and obtain the subject position after resuming photometry of the subject's field And a prediction means.

The movement predicting means obtains the moving speed of the object based on the output of the object tracking means, and predicts the movement of the object based on the moving speed. In this case, the latest moving speed may be obtained by using the past moving speed information of the subject. Further, the prediction calculation by the movement prediction means is performed while the photometry means cannot measure the field due to the rise of the quick return mirror. Further, the camera according to the present invention has a configuration in which exposure calculation means for calculating an appropriate exposure value based on the output of the subject tracking means is added.

[0012]

According to the present invention, the object tracking section performs object tracking, the movement predicting section predicts the moving position of the object during the exposure operation, and the object tracking section based on the position information predicted by the moving predicting section after the exposure is completed. Resume subject tracking by.

In this case, since the subject position is predicted in the movement predicting section based on the moving speed of the subject,
It can be easily predicted. Moreover, since the latest moving speed of the subject is calculated using the past moving speed of the subject, stable prediction can be performed even if the moving speed of the subject is unstable.

Further, since the proper exposure value is calculated by the exposure calculation section based on the output of the subject tracking section, it is possible to always obtain the optimum exposure.

[0015]

1 and 2 are block diagrams of an optical system and a control system showing an embodiment of a camera having a subject tracking function according to the present invention.

In the optical system shown in FIG. 1, the light flux that has passed through the taking lens 1 is reflected by the quick return mirror 2 to form an image on the diffusing screen 3, and the image is taken through the condenser lens 4, the pentaprism 5 and the eyepiece 6. A part of the light flux imaged by the diffusion screen 3 while reaching the human eye is formed on the photometric element 9 through the condenser lens 4, the pentaprism 5, the photometric prism 7 and the photometric lens 8. Has been done.

As shown in FIG. 3, the photometric element 9 has a photometric area in which the field H is divided into 20 in the horizontal direction and 240 in the vertical direction. The photometric area at the lower left is (1,1) address and the upper right. An address is assigned to each photometric area with the photometric area of (20, 12).

The control system shown in FIG. 2 includes a photometric unit 10 that outputs the brightness information of each area measured by the photometric element 9, and an exposure calculation unit 11 that calculates appropriate exposure information based on the brightness information from the photometric unit 10. A subject tracking unit 12 that tracks a subject in the field based on the brightness information from the photometry unit 10, and a CPU configuration that calculates the aperture value, shutter speed, etc. based on the proper exposure information from the exposure calculation unit 11. Control circuit 1
3, an exposure control unit 14 that performs exposure control based on the control of the control circuit 13, and a movement prediction unit 15 that predicts the movement of the subject during exposure control and outputs the information to the subject tracking unit 12 after the exposure control is completed. Become.

The control circuit 13 starts an internal program when the release half-push switch 16 is closed, and starts photometry at the photometry section 10. Further, when the release full-push switch 17 is closed, the exposure control in the exposure control unit 14 is started based on the proper exposure information from the exposure calculation unit 11.

The movement predicting section 15 is a shutter release speed information and shutter release information input from the control circuit 13.
The movement position of the subject is predicted based on the tracking subject information input from the subject tracking unit 12, and after the exposure control unit 14 finishes the exposure, the predicted position information is output to the subject tracking unit 12.

Next, the subject tracking operation according to the present invention will be described in detail with reference to the flow chart shown in FIG. This operation starts when the release half-push switch 16 is closed.

First, the register n is set to the initial value "1" (step S1). This register n functions as a flag indicating whether or not the processing loop is the first time. Next, the photometry section 10 performs photometry on the field H, and the brightness information for each photometry area is captured (step S2).

Then, subject information is extracted from the luminance information of each photometric area and stored in the subject tracking section 12 (step S3). In the case of the first processing, since the subject to be tracked has not been specified yet, the subjects in the total 16 vertical and horizontal 4 photometric areas A in the center of the field H should be tracked. Remember as a subject. Therefore, after the photographer puts the object to be tracked in the area A, the information of the object to be tracked is stored by pressing the release button halfway.

Next, the exposure calculator 11 calculates the proper exposure value BVa (step S4). Proper exposure value BV
a is the average value BVobj of the brightness information of each area in the subject tracking area including 16 photometric areas, which will be described later, and the average value BVr of the brightness information of each of the other 224 (= 240-16) areas. Is calculated from the following formula. BVa = (BVobj + BVr) / 2 ... [Equation 1]

Then, it is determined whether the register n is "1", that is, whether the processing loop is the first time (step S5). If it is the first time, the register n is reset to "0" (step S6), the photometry of the object field H is performed by the photometry unit 10, and the brightness information of each area is again taken in (step S7).

Next, the subject tracking section 12 performs a subject tracking calculation (step S8). In this calculation, 16 regions (4 × 4) indicated by a thick frame in FIG. 5 are set as the subject tracking region R, numbers 1 to 16 are assigned to each photometric region, and the brightness information of each region is obtained. Let B1 to B16. Then, the subject tracking area R is shifted in the X direction, the Y direction, and the diagonal direction by one area in each of the forward and reverse directions to form a new object tracking area.
9 areas are considered together with the current subject tracking area R, and luminance information Bx (x = 1 to 16) of each area of the current subject tracking area R and each area of the new subject tracking area are set. A comparison value D is calculated by comparing with the brightness information Bx '. D = Σ | Bx-Bx '| ... [Equation 2]

In the symbol Σ (sigma), x is 1 to 16
Represents the sum of the data up to, and the brightness information Bx uses the information stored in step S3 when the loop is the first time, and uses the data stored during the previous subject tracking when the loop is the second time or later, As the brightness information Bx ', the latest brightness information obtained in the immediately preceding step S7 is used.

In this way, the comparison value D is obtained for the above nine object tracking areas, and the area having the smallest comparison value D is set as the moved object tracking area. This will be described with reference to the explanatory diagram shown in FIG. FIG. 6A shows the position of the object obtained when the object tracking is performed in step S8 by the above-described calculation method, and the brightness information and the position information of the 16 regions R in the thick line are used as the tracking object information. Remembered.

Now, let us say that the tracking subject has moved to the position shown in FIG. 6B when the processing loop has completed one cycle and has come to step S8 again. At this time, since the area indicated by the dotted line is stored as the previous object tracking area, the object tracking calculation is eight ways in which the area of the dotted line is shifted in the vertical, horizontal, and diagonal directions by one area each. The calculation of the equation 2 is performed for the nine types of dotted line frames as in the previous time.

Then, in the case of FIG. 6 (a), the subject to be tracked is located exactly in the center of the tracking frame.
The area when the tracking area is shifted diagonally to the upper right of the street has the strongest correlation with the previous time, and the comparison value D also has the smallest value at that time. Therefore, the subject tracking region R moves in the upper right direction with respect to the previous region, and the subject is tracked. The subject tracking unit 12 stores the position information and the brightness information of each of the 16 new subject tracking regions R, and prepares for the next subject tracking.

Next, returning to FIG. 4, the moving speed of the subject is calculated (step S9). The moving speed is used for predicting a subject position described later. Calculation of moving speed is step S
It is obtained from the latest subject position obtained in 8 and the subject position immediately before. Now, assume that the bottom left addresses of the subject tracking areas shown in FIGS. 6 (a) and 6 (b) are (x1, y1) and (x2, y2), respectively, and the data shown in FIG. 6 (a) are collected. From the time taken to collect the data shown in FIG. 6 (b) from t, the object speed V in the X and Y directions can be calculated.
x and Vy are respectively calculated as follows. Vx = (x2-x1) / t ... [Equation 3] Vy = (y2-y1) / t ... [Equation 4]

When the loop is the second and subsequent times, the object speeds Vx 'and Vx in the X and Y directions obtained last time are obtained.
It can be calculated using y ′ as follows. Vx = {(x2-x1) / t + 7 * Vx '} / 8 ... [Equation 5] Vy = {(y2-y1) / t + 7 * Vy'} / 8 ... [Equation 6]

When the moving speed is obtained by this method, the next moving speed is obtained in consideration of the history of past speeds, so that a stable moving speed can be obtained even when the moving speed of the subject is unstable. It should be noted that in the equations 5 and 6, the data is updated by 1/8, but this may be adjusted depending on the operation cycle and the speed of response.

Next, returning to FIG. 4 again, it is judged whether or not the release is half-pressed (step S10). If it is half-pushed, the process returns to step S4, and if not, it is determined whether the half-push timer has expired (step S11). If the timer has not expired, the process returns to step S4, and if the timer has expired, the process ends. Normally, when the loop is the first time, step S
The process returns from step 10 to step S4. In this way, the first processing ends. In the first processing, the moving speed of the subject needs to be calculated at least once before the full-press of the release is detected. When the first processing is finished, the loop starts the second processing and thereafter. .

First, in step S4, the exposure calculation unit 11 is again used.
To calculate the proper exposure value BVa (step S
4). Next, it is determined whether the register n is "1", that is, whether the processing loop is the first time (step S5). In this case, the register n is "0" because it is the second and subsequent processes.

Next, it is determined whether or not the release has been fully pressed (step S12). If not fully pressed, the process returns to step S7 and thereafter, and if fully pressed, the movement prediction unit 15 predicts the subject position (step S7).
13).

Here, the movement prediction of the subject position will be described with reference to the explanatory view shown in FIG. Now, suppose that the subject S is being tracked by the subject tracking area R as shown in FIG. The subject S is moving to the right in the figure as indicated by the arrow.

If the subject S moves to the position shown in FIG. 7 (b) while the release is fully pressed and the exposure control is being performed, to start the subject tracking again after the exposure is finished, As described above, the subject S is tracked from a position centered on the subject tracking region R immediately before the release. However, since the subject S has moved to a position far away from the tracking region R at that time, tracking becomes impossible in the state shown in FIG. 7B.

However, if the moving direction of the subject S and the time required for the exposure control are known at the time shown in FIG. 7A, the position of the subject S can be predicted at the time when the exposure control ends. Therefore, using the position information (Xn, Yn) of the subject obtained in step S8, the moving velocities Vx, Vy of the subject found in step S9, the time tm required for the quick return mirror 2 to move up and down, and the shutter speed te, From the formula, the predicted position of the subject S after the exposure (Xn + 1, Yn +
1) ask. Xn + 1 = Xn + (tm + te) * Vx ... [Equation 7] Yn + 1 = Yn + (tm + te) * Vy ... [Equation 8]

The predicted position of the subject thus obtained (Xn + 1
, Yn + 1) as object position information after the end of exposure and subject tracking is performed based on this data, even if the subject moves during exposure control, the tracking area R is As shown in (), the subject S can be captured by moving to the predicted position, and subject tracking can be performed reliably.

Next, returning to FIG. 4 again, based on the proper exposure value obtained in step S4, the exposure control section 14 drives the diaphragm mechanism and the shutter mechanism to perform exposure control (step S14), and again after step S7. Return to processing.

[0042]

According to the present invention, the subject tracking unit tracks the subject during the preparation for photographing, and the movement predicting unit predicts the movement position of the moving subject after the end of exposure during the exposure control, Since the subject tracking is restarted based on the predicted position information after the end of the exposure, it is possible to prevent the subject from being lost due to the movement of the subject during the exposure control and the subject tracking becoming impossible.

[Brief description of drawings]

FIG. 1 is a block diagram of an optical system showing a configuration of an embodiment of a camera having a subject tracking function according to the present invention.

FIG. 2 is a block diagram of a control system showing a configuration of an embodiment of a camera having a subject tracking function according to the present invention.

FIG. 3 is a diagram showing an example of a photometric area of the photometric element shown in FIG.

FIG. 4 is a flowchart showing an example of a subject tracking operation according to the present invention.

FIG. 5 is a diagram for explaining a subject tracking method according to the present invention.

FIG. 6 is a diagram for explaining a subject tracking method according to the present invention.

FIG. 7 is a diagram for explaining a subject position prediction method according to the present invention.

FIG. 8 is a diagram for explaining a conventional subject tracking method.

[Explanation of symbols]

 1 Shooting Lens 2 Quick Return Mirror 3 Diffusing Screen 4 Condenser Lens 5 Penta Prism 6 Eyepiece 7 Photometric Prism 8 Photometric Lens 9 Photometric Element 10 Photometric Section 11 Exposure Calculation Section 12 Subject Tracking Section 13 Movement Prediction Section 14 Control Circuit 15 Exposure Control unit 16 Release half-press switch 17 Release full-press switch

Claims (5)

[Claims] 1. A photometric device that divides a field into a plurality of regions to perform photometry, and outputs a plurality of photometric information relating to the brightness of the field, and a movement of an object is detected using the output of the photometric device. A subject tracking unit for tracking the subject, and a predictive calculation of the movement of the subject based on the output of the subject tracking unit while the photometry of the object field is not possible by the photometry unit, A camera having a subject tracking function, comprising: a movement predicting unit that obtains the subject position after resuming photometry of a field. 2. The movement predicting means obtains the moving speed of the object based on the output of the object tracking means, and predicts the movement of the object based on the moving speed. A camera with the subject tracking function. 3. The camera having a subject tracking function according to claim 2, wherein the movement predicting means obtains the latest movement speed using information on the past movement speed of the subject. 4. The subject according to claim 1, wherein the movement predicting unit predicts and calculates the movement of the subject while the photometry unit cannot perform photometry of the field due to a rise of a quick return mirror. A camera with a tracking function. 5. A camera having a subject tracking function according to claim 1, further comprising exposure calculation means for calculating an appropriate exposure value based on an output of the subject tracking means.