JP2877979B2 - Imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as a video camera which performs automatic focus adjustment based on an image pickup video signal obtained from an image pickup device.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing an example of a conventional imaging device. In FIG. 1, reference numeral 1 denotes a focus lens, which forms an image of a subject (not shown) on an image sensor 2 such as a CCD. The output of the image sensor 2 is connected to the video signal processing circuit 3, and one of the outputs is connected to the monitor TV4, so that the subject can be captured as a visible image. Reference numeral 6 denotes a high-pass filter (hereinafter, referred to as HPF).
A luminance signal (hereinafter, referred to as a Y signal) 5 which is the other output of the video signal processing circuit 3 is connected, and its H
The output of the PF 6 is connected to the integrating circuit 7, and the HPF 6 and the integrating circuit 7 constitute a focus evaluation value detecting means 18, and outputs a focus evaluation value 8.

Reference numeral 9 denotes a focus control means, to which the focus evaluation value 8 is inputted, and an output of the focus control means 9 being a signal generated based on the focus evaluation value 8 and connected to the focus motor 10. The focus lens 1 is driven according to the focus evaluation value 8.

[0004] Next, the operation of the conventional imaging apparatus configured as described above will be described with reference to FIGS. 4 and 5. In FIG. 3, a subject image (not shown) is formed on the image sensor 2 by a focus lens, photoelectrically converted, and input to the video signal processing circuit 3. Then, a visible image is obtained by being applied to the monitor TV4 as a composite video signal (not shown).

Next, in order to automatically focus a subject image on the image sensor 2 and obtain a clear image on the monitor TV 4, the following procedure is required. First, the Y signal 5 is extracted from the video signal processing circuit 3, the high-frequency component of the Y signal 5 is extracted by the HPF 6, integrated by the integrating circuit 7 for each horizontal scanning cycle, and integrated over one field. The focus evaluation value 8 which is a signal indicating the sharpness of the image can be obtained. That is, the above procedure is a focus evaluation value detection procedure.

Next, if the focus evaluation value 8 is input to the focus control means 9, the focus control means 9
The focus motor 1 that drives the focus lens 1 so as to constantly monitor the focus evaluation value 8 and guide it to the peak.
0 is controlled. In this manner, a closed loop of so-called hill-climbing autofocus (AF) is formed, and a stable focusing operation is realized.

Here, the hill-climbing AF will be described in more detail. As described above, the fact that the amount of the high frequency component of the Y signal 5 of the video image corresponds to the degree of focusing is utilized. In other words, each subject has a unique spatial frequency component, but since the focus lens 1 acts as a low-pass filter for this, an actual imaged video signal is output when the focus lens 1 is in focus. Only the spatial frequency components unique to the subject are included, but as the focus lens 1 deviates from this point, it corresponds to passing through a low-pass filter with a lower cutoff frequency, and the blurred image lacks high frequency components. Therefore, as shown in FIG. 5, the amount of the high frequency component of the video signal is
In other words, the focus evaluation value 8 forms a peak at the focal point on the distance axis of the focus lens. This is a hill climb AF
It is called.

In this hill-climbing AF, as shown in FIG. 4, focusing control is performed by following five steps shown in (101) to (105). That is, (101) Start: First, the focus lens 1 is started in an arbitrary direction, and the focus evaluation value 8 is measured. (102) Climbing: If the starting direction increases the focus evaluation value 8, the lens 1 continues to be driven in that direction; otherwise, the lens 1 is driven in the opposite direction. (103) Detection of the top: detecting that the position of the focus lens 1 has passed the in-focus point, that is, the top of the focus evaluation value 8 due to the change of the focus evaluation value 8 from the increasing direction to the decreasing direction, and stores it. (104) Stop: Return the focus lens 1 to the in-focus position stored in (103) and stop. (105) Standby: The focus control is stably performed by the algorithm of monitoring the state of the focus evaluation value 8 and returning to the start of (101) as necessary when a change occurs.

[0009]

In the conventional imaging apparatus configured as described above, the focus evaluation value 8 fluctuates for each field due to camera shake in hand-held imaging, particularly in imaging at the telephoto end when zooming. Despite having
Since the focusing control is continuously performed by the above algorithm, there is a problem that the focusing operation is not easily completed.

In order to avoid the above-described problem, a moving average of several fields of the focus evaluation value 8 over the several fields is adopted as a true focus evaluation value, thereby performing hill climbing. For example, focus lens 1
When the focus evaluation value 8 changes sharply with respect to the position of the subject, that is, when the focusing operation is performed with the depth of focus being shallow, the true focus position and the focus evaluation value are the maximum. Since the difference between the positions becomes relatively large, there is a problem that the focusing operation is terminated while the image is blurred.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to prevent the occurrence of a so-called blur lock in which a focusing time caused by a camera shake during hand-held shooting is extended or a focusing operation is terminated while the subject is blurred. It is an object of the present invention to provide an imaging device that can perform the imaging.

[0012]

According to a first aspect of the present invention, there is provided an imaging apparatus comprising: an evaluation value detection unit for detecting a high-frequency component level of an imaged video signal obtained from an imaging element as a focus evaluation value at predetermined time intervals; to monitor the change of the value, this focus
The focus lens is moved in a direction in which the point evaluation value increases, and focus control means for performing a focusing operation for fixing the focus lens at a position where the maximum evaluation value is obtained, and the movement of the imaging apparatus body and the direction of the movement are detected. I Ri detection of the motion vector detection means for obtaining
The motion vector is greater than the first predetermined value and the second
A diaphragm that detects the amount of displacement of the diaphragm mechanism when it is smaller than the fixed value.
A plurality of aperture values according to the aperture value detected by the aperture value detection means.
Calculate the moving average based on the focus evaluation value obtained at regular intervals.
Input the value to the focus control means
Things .

Arithmetic control means of the image pickup apparatus according to the second invention
Indicates that the output of the aperture value detecting means is smaller than a predetermined value.
Is a first predetermined number of focus evaluation values obtained at regular intervals.
To obtain the moving average, and the output of the aperture value detection means
If the value is larger than the first predetermined number, the second
Calculate the moving average using a predetermined number of focus evaluation values.
It is a thing.

An image pickup apparatus according to a third aspect of the present invention is an image pickup device
The level of the high-frequency component of the obtained video signal
Focus evaluation value detecting means for detecting a focus evaluation value for each interval
And monitor the detected change in the focus evaluation value to
Worth moves the focus Surenzu in the direction of increasing,
Focusing operation for fixing at the position where the maximum evaluation value is obtained
Focus control means, the movement of the imaging device and the direction of the movement.
The motion vector detecting means to detect and the displacement amount of the aperture mechanism
Aperture value detecting means for detecting, and the motion vector detecting means
Is smaller than a first predetermined value.
Is detected by the focus evaluation value detection means
The focus evaluation value input to the focus control means
The motion vector detected by the detection means is a first predetermined
If the value is larger than the value and smaller than the second predetermined value,
Values obtained at predetermined intervals according to the output of the threshold value detection means.
A moving average is calculated from the focus evaluation values obtained, and the
Input to the focus control means and detected by the motion detecting means.
When the output motion vector is larger than the second predetermined value,
The focus control means is controlled to inhibit the focusing operation.
And an arithmetic control means for controlling the operation.

[0015]

According to the first aspect of the present invention, there is provided an imaging apparatus comprising : a motion vector detecting means for detecting a motion of a device and a direction of the motion;
Stage and monitors the state of the aperture value and the diaphragm mechanism of the motion vector detected by, when the range value of motion vector is set in advance, it is determined that an unintentional hand movement state,
A plurality of focal points determined for each predetermined period according to the aperture value
A moving average is obtained using the evaluation value, and this value is adopted again as the focus evaluation value.

An image pickup apparatus according to a second aspect of the present invention provides a motion vector
When the aperture is within the preset range, the aperture value is
Is smaller than the first predetermined number of focus evaluation values.
When the moving average is calculated and the aperture value is larger than the predetermined value,
A second predetermined number of focus evaluation values larger than the first predetermined number;
Using these values as the focus evaluation value
I have.

According to a third aspect of the present invention, there is provided an imaging apparatus comprising:
Is less than the preset range,
Judgment and focus evaluation value detection without taking the moving average of the focus evaluation value
Focus operation using the focus evaluation value detected by the
Is, when in the range motion vector was previously set boss,
Judgment of camera shake state
A moving average is calculated using the focus evaluation value obtained for each interval,
This value is adopted again as the focus evaluation value, and the motion vector
If exceeds the preset range, panning is
The camera is in a tilted state and disables the focusing operation.
You.

[0018]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an imaging apparatus according to an embodiment of the present invention. In FIG. 1, the same components as those in the conventional example shown in FIG. Omitted.

In FIG. 1, a motion vector detecting means 11 receives a Y signal 5 and outputs a motion vector 1 as an output.
2 is input to the arithmetic and control unit 13. 1
Reference numeral 5 denotes an aperture value detection circuit which detects the amount of displacement of the aperture mechanism 14 as an aperture value 16 using a Hall element, and a known method can be used. The aperture value 16 corresponds to what is known as a so-called F-number, and is connected to the arithmetic control unit 13 as in the case of the motion vector 12, and when the aperture value is large, the aperture mechanism 14 is closed. It is in a state, and when it is small, it is in an open state.

The output of the arithmetic control means 13 is a focus evaluation value arithmetically processed according to the motion vector 12 and the aperture value 16 and is input to the focus control means 9. Incidentally, this value does not always match the focus evaluation value 8. Further, a focusing operation prohibition signal 17 is also input to the focus control means 9. Further, the output of the focus control means 9 is connected to a focus motor 10.

Next, the operation of the embodiment configured as described above will be described. However, description of the same parts as those of the conventional technique will be omitted. In FIG. 1, a motion vector detecting means 11 extracts a motion vector 12 based on a Y signal 5. Although a detailed description of the method for obtaining the motion vector 12 is omitted, a known means such as a representative point matching method using a field memory can be used. The motion vector 12 obtained by such a method is applied to the operation control means 13.

On the other hand, the aperture value 16 detected by the well-known aperture value detection circuit 15 is also added to the arithmetic control means 13. In this arithmetic control means 13, the motion vector 12 and the focus The aperture value 16, which is information on the depth, is constantly monitored.

If the motion vector 12 is smaller than a predetermined value, the arithmetic control means 13
The input focus evaluation value 8 is output to the focus control means 9 as it is. Further, it is assumed that the motion vector 12 is larger than a predetermined value and is not large enough to determine that the panning or the tilt is performed. Here, when the aperture value 16 is equal to or less than a predetermined value, that is, when the depth of focus is relatively shallow, a moving average of the focus evaluation value 8 for three fields is obtained, and the value is output to the focus control means 9. When the aperture value 16 is larger than a predetermined value, that is, when the depth of focus is relatively deep, 5
The moving average for the field is calculated, and the value is output to the focus control unit 9.

Here, the reason why the number of moving average fields of the focus evaluation value 8 that can be obtained by the aperture value 16 is variable will be described below. That is, when a moving average is calculated for the focus evaluation value 8, the fluctuation of the evaluation value due to camera shake is suppressed, and there is an advantage that a so-called blur lock problem due to a fake mountain can be avoided, but a focus lens which is at the top of a mountain. The position may be slightly different from the actual position. This problem may cause visual impairment, particularly when focusing is performed with a small aperture value 16, that is, with a small depth of focus. In order to avoid such a problem, the number of fields on which the moving average is performed is reduced as compared with when the depth of focus is deep. In the case where the depth of focus is deep, such a problem is practically impossible. In order to suppress the fluctuation of the focus evaluation value 8 due to camera shake, it is necessary to increase the number of fields for which the moving average is taken. You are making an effort. Incidentally, the determined value of the aperture value 16 in the present embodiment is a so-called F-number of 5.6.
Needless to say, the value is not limited to this value. In this case, two cases are used in this embodiment, but the present invention is not limited to this case.

Further, when the motion vector 12 becomes large enough to determine that the motion vector 12 is in the panning or tilt state, a focus operation prohibition signal 17 is output to the focus control means 9.

The focus control means 9 controls the driving of the focus motor 10 in accordance with the input information from the arithmetic control means 13 so as to maximize the input information, that is, the focus evaluation value, usually in accordance with the principle of hill-climbing servo. I do. When the focusing operation prohibition signal 17 is received, the prohibition is released, that is, the focusing operation is not performed until the motion vector 12 falls within a certain value.

By the above-described operation, accurate and quick focusing can be performed in any scene. Here, the output to the focus control means 9 is represented by the motion vector 12
Is divided into three cases depending on the value of the motion vector 12. If the absolute value of the motion vector 12 is x (the number of horizontal scanning lines), it is experimentally known that the following values are desirable. No camera shake: vertical direction x ≦ 2H: output without taking a moving average of focus evaluation value 8 ・ With camera shake: vertical direction 2H <x ≦ 40H: take a moving average of focus evaluation values 8 for 3 to 5 fields・ Tilt: Vertical direction x> 40H… Outputs focus operation prohibition signal 17

Although the value in the horizontal direction is omitted, the width may be considered to be a width that forms a square with the value in the vertical direction on the screen. However, the above values are only guidelines and are not limited to these values.

FIG. 2 is a block diagram of an image pickup apparatus according to another embodiment of the present invention. In FIG. 2, reference numeral 19 denotes an angular velocity sensor which is attached to the image pickup apparatus main body and detects shaking of the apparatus main body. The angular velocity sensor 19 is connected to the motion vector detecting
Generates the motion vector 12 by processing the information obtained from the angular velocity sensor 19, and inputs the motion vector 12 to the arithmetic and control unit 13. Since other configurations are the same as those of the embodiment of FIG. 1, the corresponding portions are denoted by the same reference numerals and description thereof will be omitted.

Next, the operation of FIG. 2 will be described. The motion of the imaging device is detected by the angular velocity sensor 19, and the output is input to the motion vector detection unit 11. The motion vector detecting means 11 performs processing such as amplification and shaping on a signal corresponding to the motion of the imaging device obtained by the angular velocity sensor 19, and then inputs the signal as a motion vector 12 to the arithmetic control means 13. The following description is the same as that of the above embodiment, and therefore will be omitted. In any case, a focusing operation with less waste can be performed, and accurate and quick focusing can be performed in any scene.

[0031]

As it is evident from the foregoing description, according to the first aspect, the dynamic
The motion vector detected by the
When it is larger than the first predetermined value and smaller than the second predetermined value
Are a plurality of fixed time intervals corresponding to the output of the aperture value detection means.
A moving average is calculated from the focus evaluation values obtained in
Is input to the focus control means to perform the focusing operation.
Runode, even if the camera shake occurs during the focusing operation,
Effect of the focus evaluation value variation due to its rather Rukoto appear in the input information to the focus control means, therefore, the Niseyama the focus evaluation value is determined as the focus during a focusing operation
Without, it is possible to perform a focusing operation of the toward the true focal point.

According to the second aspect, the detected motion vector
Torque is greater than a first predetermined value and smaller than a second predetermined value
The output of the aperture value detecting means is smaller than a predetermined value.
Sometimes, a first predetermined number of focus evaluations obtained at regular intervals
The moving average is calculated based on the value, and the output of the aperture
When the value is larger than the predetermined value, the value is larger than the first predetermined number.
A moving average is obtained from a second predetermined number of focus evaluation values, and
Enter the value into the focus control means to perform the focusing operation
The aperture value is small, that is, the depth of focus is shallow.
In such a case, the focus evaluation value
Position of the focus lens controlled by the focus control means.
Position is the focus lens position in the actual (true) focus state.
Can be prevented from shifting relative to the
When the value is large, suppress the fluctuation of the focus evaluation value due to camera shake
So that you can get the true
A focusing operation can be performed toward the mountain.

According to the third aspect, the detected motion vector
When the torque is smaller than the first predetermined value, the focus evaluation value is detected.
The focus evaluation value detected by the
Motion vector detected by inputting to the stage and performing focusing operation
Is larger than the first predetermined value and smaller than the second predetermined value.
The aperture value detected by the aperture value detection means.
Focus evaluations obtained at regular intervals according to the threshold value
Calculates the moving average based on the value, and uses that value as focus control means
To perform a focusing operation and detect the motion vector
Is greater than the second predetermined value, the focus control means
Control to prohibit focusing operation by
Appropriate focusing operation is controlled according to various movements of the device.
If camera shake occurs during the focusing operation
Even if the focus evaluation value is false,
Focusing operation can be performed toward the focal point.
When the issued motion vector is larger than the second predetermined value,
That is, during panning or tilting,
Eliminate unnecessary movement of focus lens by prohibiting focus movement
Can achieve accurate and quick automatic focusing.
To provide an imaging device with comfortable operability.
It works.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of an example of a conventional imaging device.

FIG. 4 is a flowchart illustrating a procedure of a hill-climbing autofocus.

FIG. 5 is a diagram illustrating the operation of hill-climbing autofocus.

[Explanation of symbols]

1 : focus lens 2 : imaging element 8 : focus evaluation value 9 : focus control means 11 : motion vector detection means 12 : motion vector 13 : arithmetic control means 15 :
Aperture value detection circuit 18 : Focus evaluation value detection means

Claims (3)

(57) [Claims] 1. A monitoring and focus evaluation value detection means for detecting the level of the high-frequency components of the video image signal obtained from the image pickup device as a focus evaluation value every predetermined period, the change in the detected focus evaluation value, the focus Evaluation value
There moves the focus lens in a direction of increasing the focus control means for performing a focusing operation to fix at a position where the maximum evaluation value, the motion vector detecting means for detecting the direction of the imaging equipment movement and motion, aperture An aperture value detecting means for detecting a displacement amount of the mechanism, and a motion vector detected by the motion vector detecting means.
Torque is greater than a first predetermined value and smaller than a second predetermined value
At a certain time interval according to the output of the aperture value detecting means.
A moving average is calculated from the focus evaluation values obtained in
Imaging device, characterized in that had a <br/> and an arithmetic control means for inputting to the focus control means. 2. The arithmetic control means , when the output of the aperture value detection means is smaller than a predetermined value, one of
According to a first predetermined number of focus evaluation values obtained at regular intervals
A moving average is obtained, and when the output of the aperture value detecting means is larger than a predetermined value,
A second predetermined number of focus evaluation values greater than the first predetermined number.
2. The moving average according to claim 1, wherein a moving average is obtained.
Imaging device . 3. An image pickup device according to claim 1, wherein said image signal is high.
Detects frequency component level as focus evaluation value at fixed intervals
Focus evaluation value detecting means for monitoring a change in the detected focus evaluation value, and
Move the focus lens in the direction that
Focuser that performs focusing operation to fix at a position that is the evaluation value
Motion control means and a motion vector for detecting the motion of the imaging device and the direction of the motion
Aperture detection means, aperture value detection means for detecting the amount of displacement of the aperture mechanism, and a motion vector detected by the motion vector detection means.
When torque is small Ri by a first predetermined value, the focus evaluation value
The focus evaluation value detected by the detection
Input to the control means, and the motion vector detected by the
When it is larger than the first predetermined value and smaller than the second predetermined value
It includes a plurality in accordance with the output of the aperture detecting means, predetermined time intervals
A moving average is calculated from the focus evaluation values obtained in
Is input to the focus control means, and the motion vector detected by the
2 is larger than the predetermined value, the focus control means
Calculation control means for controlling so as to inhibit the focusing operation.
An imaging device, comprising: