JP3459679B2 - Automatic focusing 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 automatic focusing device for automatically focusing the focus of an image pickup device such as a video camera.

[0002]

2. Description of the Related Art Conventionally, as an automatic focusing device of this kind, a high frequency component included in a video signal obtained from an image pickup device is extracted by a bandpass filter or the sharpness of an edge portion of a subject is extracted by a differentiating circuit or the like. There is known a method in which the focus state of the subject image is determined by doing so and the lens is moved so that the extracted amount, that is, the focus value is maximized, to obtain the focus state of the subject image. Next, an automatic focusing device according to this method will be described with reference to FIGS.

FIG. 5 is a block diagram showing the structure of a conventional image pickup apparatus. Reference numeral 1 is a lens, 2 is an image pickup element such as a CCD, and 3 is a lens.
Is a preamplifier, 4 is a process circuit, 5 is a bandpass filter (hereinafter abbreviated as “BPF”), 6 is a detection circuit, 7 is a logic control unit (hereinafter referred to as “microcomputer”), 8 is a motor drive circuit, 9 Is a motor for moving the lens 1.

Next, the operation will be described. The image of the subject is projected on the image pickup surface of the image pickup device 2 by the lens 1, and a video signal converted into an electric signal is obtained by the image pickup device 2. This video signal is amplified to a proper level by the preamplifier 3 and then converted into a standardized video signal such as NTSC by the process circuit 4. The output of preamplifier 3 is B
The PF 5 extracts a high frequency component contained in the video signal, and the detection circuit 6 obtains an output corresponding to the absolute amount of this high frequency component.

As shown in FIG. 6, the output of the detection circuit 6 changes depending on the amount of movement of the lens 1 at a certain position (point B).
Has a maximum value at. This is because when the amount of extension of the lens 1 changes, the focus state of the subject image projected on the image pickup surface of the image pickup element 2 changes, and when this is in focus, the sharpness of the projected image becomes maximum and the image pickup element This is because the absolute amount of the high frequency component contained in the signal becomes maximum when the signal is converted into the electric signal in 2.

The microcomputer 7 outputs the output of the detection circuit 6 to A /
D-convert and take in the lens 1 in the direction that maximizes this.
The rotation direction of the motor 9 is controlled via the motor drive circuit 8 so as to move. Then, by stopping the motor 9 at the position where the output of the detection circuit 6 is maximum, a focused state can be obtained.

In the above process, for example, first in FIG.
If the lens 1 is extended to the position shown by the dot,
First, an auxiliary vibration called a wobbling is performed to determine the direction of the point B, which is the in-focus position. In this method, the lens 1 is reciprocated back and forth several times with a very short width around the point A, and the direction of inclination of the point A is detected from the output of the detection circuit 6 during this time. By this operation, the direction of the point B is discriminated, and then the lens 1 is moved to the point B and stopped at the position where the output of the detection circuit 6 becomes maximum.

However, assuming that the lens 1 is extended to a position indicated by a point C in FIG. 6, that is, a position where the focus state of the image pickup surface becomes a large blur state, there is almost no inclination of the point C even if wobbling is performed. Therefore, the direction of point B cannot be detected. Even if a slight inclination is detected by increasing the width of the wobbling, it is due to the noise component, and the reliability is low. When the moving direction of the lens 1 at the point C is determined based on this result, it is not moved in the correct direction, and the moving direction is reversed after the lens 1 once hits the near end or the like.
It may happen that the point moves again in the direction of the point.

Therefore, in contrast to the above method, when the lens 1 is extended to a position as shown by point C in FIG. 6 and the judgment result by the wobbling is not obtained or is very small, the existence of the subject is present. A method has been proposed in which the lens 1 is moved in the direction of high probability for the time being (Japanese Patent Application No. 4-361620).

According to this method, when the determination by the wobbling cannot be made at a position close to the closest end as shown by point C in FIG. 6, it is assumed that the existence probability of the subject is high on the infinity side and the lens is moved to the infinity side. 1 is moved, and when the determination by the wobbling cannot be made at a position near the infinity end as shown by point D in FIG. 6, it is estimated that the existence probability of the subject is high on the close side, and the lens 1 is moved to the close side. Is to do.

[0011]

However, in the method of moving the lens in the direction in which the probability of existence of the subject is high when the determination based on the wobbling cannot be performed, the subject is present at a position near infinity as shown in FIG. 7, for example. Assuming that the lens is located at the point E, which is slightly infinite near the center from the closest end to the infinity end, the focus value changes as shown in FIG. 7, and at this time the lens position E point is Since it is a position where it is difficult to determine the inclination based on the wobbling as in the case of point C in FIG. 6, the lens 1 is moved to the close side where the existence probability of the subject is estimated to be high. In that case, the lens is hit once at the nearest end, then the direction of movement is reversed, and the lens is moved again toward infinity. For this reason, the vehicle travels back and forth over an extremely long moving distance, and it takes a long time to focus, and there is a problem in that inconveniences such as loss of shooting timing occur during this time.

The present invention has been made to solve the above problems, and can reduce the probability of erroneous movement of the lens even if the change in the detected value of the high frequency component of the video signal due to wobbling is small. The aim is to obtain an automatic focusing device.

[0013]

According to a first aspect of the present invention, a detecting means for detecting a high frequency component of a video signal obtained from an image pickup device for photographing an object through a lens, and a change in the detected value of the detecting means are predetermined. Determination means for determining whether or not the value is greater than a value, lens driving means for moving the lens within a predetermined movement range, and a lens driving means for moving the lens within the predetermined movement range.
Lens position determining means for determining the position of the lens
The lens driving means is controlled so as to perform an auxiliary vibration that vibrates the lens back and forth, and the lens is moved.
And control means for controlling the lens driving means so as to change in the detection value our if: the predetermined value
The moving range of the lens is based on the detected value.
And the lens driving means for moving the lens.
The first area that controls the
Driving the lens to move the lens in the direction of
A second area for controlling the means.

According to a second aspect of the present invention, a detecting means for detecting a high frequency component of a video signal obtained from an image pickup device for photographing a subject through a lens, and whether or not a change in the detected value of the detecting means is larger than a predetermined value. Determining means, a lens driving means for moving the lens within a predetermined moving range, and a lens driving means for moving the lens within the predetermined moving range.
The lens position determining means for determining the position and the lens driving means for performing auxiliary vibration for vibrating the lens back and forth and moving the lens are controlled.
And control means for controlling the serial lens driving means, the test
If the change in the output value is less than the above specified value,
Within the movement range of the lens, the lens
For controlling the lens driving means so as to move
Area, and in the specified direction regardless of the detected value
The lens drive means to move the lens.
A second area, and the control means further comprises:
When the change in the value is equal to or more than the predetermined value, the first and second
Regardless of the area of the
The lens driving means is controlled so as to move.

[0015]

According to the invention of claim 1, when the lens is in the first region, even if the change in the detected value of the high-frequency component obtained by the auxiliary vibration is small, the value of the detected value depends on the inclination of the detected value. By determining the moving direction of the lens, the probability of mistaking the moving direction of the lens can be reduced.

According to the second aspect of the present invention, when the lens is in the first region, even if the change in the detected value of the high frequency component obtained by the auxiliary vibration is small, By determining the moving direction of the lens according to the inclination, it is possible to reduce the probability of mistaking the moving direction of the lens. When the lens is in the second area and the change in the detection value is small, the lens is moved in the predetermined direction regardless of the inclination of the detection value. Furthermore, even if the lens is out of the predetermined area,
If the change in the detected value is large, the moving direction is determined according to the inclination.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram for conceptually explaining the present invention. First, an embodiment of the present invention will be described with reference to FIGS.
, And FIG. 1 will be described later.

FIG. 5 is a block diagram showing the configuration of the conventional example, but the configuration of the embodiment of the present invention is completely the same as that of FIG.

In FIG. 5, the process of converting the subject image projected by the lens 1 into an electric signal and obtaining a focus value is the same as in the conventional example.

The output of the detection circuit 6 changes as shown in FIG. 2 as in the conventional example of FIG. The microcomputer 7 A / D-converts and captures such a change in the focus value, and the calculation shown in the flowchart of FIG. 4 is performed based on this data. First, wobbling is performed in step S1, and then step S2
In step S3, the detection result (change in detection value) due to the wobbling is checked, and if the detection result is larger than a predetermined value, step S3
Then, the moving direction of the lens 1 is determined based on the detection result, and the motor 9 is driven in that direction. If the detection result is smaller than the predetermined value, it is determined in step S4 whether or not the position of the lens 1 at that time is in the non-estimation region shown in FIG. If the position of the lens 1 is not in the non-estimation region, the lens is moved to the one with a higher subject existence probability in step S5 as in the conventional example.

When the position of the lens 1 is in the non-estimation area,
For example, as shown in FIG. 3, when the subject is present at a position near infinity and the lens 1 is present at the position indicated by point E, the moving direction of the lens is reduced depending on the detection result of the wobbling in step S3. To decide.

By performing the above calculation, the position of the lens 1 is controlled and the in-focus state is automatically obtained. As shown in Fig. 3, the subject is near infinity and the lens is E
Even if the point E is slightly infinitely closer to the center of the moving range of the lens, if the point E is in the non-estimation region, the moving direction of the lens 1 is determined by the slight detection result obtained by the wobbling. The probability of making a mistake in the moving direction is relatively low.

As described above, the automatic focusing apparatus according to the present embodiment extracts the high frequency component from the video signal obtained by converting the subject image projected by the lens 1 into the electric signal by the image pickup device 2, and The amount of extension of the lens 1 is adjusted in the direction in which the high-frequency component becomes large, and the in-focus state of the lens 1 is automatically obtained, and auxiliary vibration (wow ring) is performed to determine the moving direction of the lens 1. When the detection result obtained by the auxiliary vibration is smaller than a predetermined value, when the lens 1 is moved in the direction in which the existence probability of the subject is high regardless of the detection result of the auxiliary vibration, the lens 1
From the closest end to the infinite end of, if a non-estimation area is defined in the moving range, for example, near the center, and the detection result of the inclination of the wobbling is slight when the lens position is in this area, The lens is not moved in the direction in which the existence probability of the subject is high, but the moving direction of the lens is determined based on the detection result of the wobbling, although the number is small. As a result, the probability of making a mistake in determining the moving direction of the lens can be made relatively small, and a relatively good focusing operation can be performed.

Next, the present invention will be described conceptually with reference to FIG. In FIG. 1, reference numeral 11 is a detecting means for detecting a high frequency component of a video signal obtained from an image pickup device 2 for photographing a subject through a lens 1, and 12 is a judgment as to whether a change in a detection value of the detecting means 11 is larger or smaller than a predetermined value. Determination means to
Reference numeral 13 is a lens driving means for moving the lens 1 in the optical axis direction within a predetermined movement range, and 14 is lens position detection for determining whether or not the lens 1 is within a predetermined area defined within the predetermined movement range. Means, 15 is a control means for controlling the lens driving means 13 to move the lens 1 based on the detection value of the detection means 11, the determination result of the determination means 12 and the determination result of the lens position determination means 14.

The detection means 11 is composed of the BPF 5 and the detection circuit 6 of FIG. 5, and the judgment means 12, the lens position judgment means 14 and the control means 15 are composed of the microcomputer 7.
The lens driving means 13 is composed of a motor driving circuit 8 and a motor 9.

Next, the operation of the above configuration will be described. In order to perform the focusing operation, first, the control means 15 controls the lens driving means 13 so as to perform auxiliary vibration that vibrates the lens back and forth. Next, the control means 15 controls the lens driving means 13 on the basis of the respective judgment results of the judging means 12 and the lens position judging means 14 obtained by this auxiliary vibration. If it is determined that the detected value changes and the change in the detected value is equal to or less than the predetermined value and the lens 1 is in the predetermined area, the lens is moved to a position where the detected value becomes maximum. To control. When it is determined that the change in the detected value is less than or equal to the predetermined value and the lens 1 is not within the predetermined area, the lens 1 is controlled to move in the predetermined direction.

[0027]

As described above, according to the first aspect of the present invention, the predetermined area is provided within the moving range of the lens, whether the lens is within the predetermined area, and the detected value of the high frequency component of the video signal. Is determined to be greater than a predetermined value and the lens movement is controlled based on the result of the determination, so that if the lens is in the first area, the change in the detected value is small. Also, by controlling the movement in accordance with the detected value, it is possible to reduce the probability of erroneous movement direction, shorten the time until the focused state is obtained, and perform good focusing operation. There is an effect that can be.

According to the second aspect of the present invention, a predetermined area is provided within the moving range of the lens, and whether or not the lens is within the predetermined area and the change in the detected value of the high frequency component of the video signal are larger than the predetermined value. If the lens is in the first area and the change in the above detection value is small, a focusing operation is performed using the detection value, and the lens is in the second area and the above detection value is detected. When the change in the value is small, the lens is moved in a predetermined direction regardless of the detected value, and when the lens is in the second area and the change in the detected value is large, the lens is moved according to the detected value. With such a configuration, it is possible to reduce the probability of erroneous movement directions and to obtain a focused state reliably and in a short time, and it is possible to perform a good focusing operation.

[0029]

[Brief description of drawings]

FIG. 1 is a block diagram conceptually showing an embodiment of the present invention.

FIG. 2 is a graph for explaining the operation of the embodiment.

FIG. 3 is a graph for explaining the operation of the example.

FIG. 4 is a flowchart illustrating the operation of the embodiment.

FIG. 5 is a configuration diagram showing an imaging device to which the present invention can be applied.

FIG. 6 is a graph for explaining the conventional operation of FIG.

FIG. 7 is a graph for explaining the conventional operation of FIG.

[Explanation of symbols]

1 lens 2 image sensor 5 bandpass filter 6 Detection circuit 7 Microcomputer 8 Motor drive circuit 9 motors 11 Detection means 12 Judgment means 13 Lens drive means 14 Lens position determination means 15 Control means

Claims (2)

(57) [Claims] 1. A detecting means for detecting a high frequency component of a video signal obtained from an image pickup device for photographing an object through a lens, and a judging means for judging whether or not a change in a detected value of the detecting means is larger than a predetermined value. , A lens driving means for moving the lens within a predetermined moving range, and determining the position of the lens within the predetermined moving range
The lens position determining means and the lens driving means are controlled so as to perform auxiliary vibration that vibrates the lens back and forth, and the lens is moved.
And control means for controlling the lens driving means so as to, when the change of the detection value is less than the predetermined value, the upper
Within the movement range of the lens, the
Control the lens driving means to move the lens.
In the first direction, regardless of the detected value
The lens driving means is controlled to move the lens.
An automatic focusing device having a second region for controlling . 2. A detecting means for detecting a high frequency component of a video signal obtained from an image pickup device for photographing an object through a lens, and a judging means for judging whether or not a change in the detected value of the detecting means is larger than a predetermined value. , A lens driving means for moving the lens within a predetermined moving range, and determining the position of the lens within the predetermined moving range
The lens position determining means and the lens driving means are controlled so as to perform auxiliary vibration that vibrates the lens back and forth, and the lens is moved.
And a control means for controlling the lens driving means so that the change in the detected value is equal to or less than the predetermined value.
Within the movement range of the lens, the
Control the lens driving means to move the lens.
In the first direction, regardless of the detected value
Control said lens driving means so as to move the lens
And a second area for controlling the change in the detected value,
In the above case, regardless of the first and second areas above
It is necessary to move the lens based on the detected value.
Automatic focusing device characterized by controlling lens driving means
Place