JPH11136562A - Imaging device - Google Patents

Abstract

(57) [Problem] To provide a small-sized and high-magnification imaging device by maintaining a constant magnification of a captured image during a wobbling operation. SOLUTION: In order to adjust the focus of an optical image from a zoom lens 10, the position of a focus lens 20 is adjusted by a wobbling operation. At this time, the microcomputer 4 calculates the magnification of the focus lens 20 from the optical position of the zoom lens 10, and outputs a magnification control signal C3 for canceling the magnification. In accordance with the magnification control signal C3, the magnification of the imaging signal V4 is changed by the electronic zoom changing circuit 5.

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 having an automatic focus adjustment (auto focus) function, and more particularly, to an image pickup apparatus which does not change the magnification of a picked-up image during a wobbling operation.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an optical system of an image pickup apparatus of this kind. As shown in FIG. 4, the optical system 7 of the imaging device includes a zoom lens 10 and a focus lens 20, and the position of the focus lens 20 is focused on an image captured by the zoom lens 10. Autofocus was performed by moving to the position.

[0003]

However, the conventional image pickup apparatus has the following problems. When the optical system 7 of this imaging apparatus is small and can output a high-magnification image, the response of the optical system 7 itself is very good.
However, during autofocus, the focus lens 20 is guided to the in-focus position without wobbling. For this reason, the captured image changes during wobbling, and the image becomes difficult to see. In particular, at the time of wobbling at the in-focus position of the focus lens 20, since the magnification of the captured image changes in the focused state, it becomes somewhat difficult to see. As the size of the device becomes smaller and the magnification becomes higher, the change in magnification of the captured image at the time of wobbling becomes larger and may be somewhat noticeable.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide an image pickup apparatus which is small in size and can be increased in magnification by maintaining a constant magnification of a picked-up image during a wobbling operation. The purpose is.

[0005]

In order to solve the above-mentioned problems, an image pickup apparatus according to the present invention comprises a zooming unit for changing a magnification of an optical image by changing an optical position of a zoom lens, and a focus lens. A focus adjustment unit that performs auto-focusing of an optical image by changing the optical position of the imaging lens; an imaging signal generation unit that is formed by the focusing unit and outputs an optical image as an electrical imaging signal; and a wobbling operation of a focus lens Sometimes, a magnification control unit that obtains a magnification ratio of the focus adjustment unit from the optical position of the zoom lens and outputs a magnification control signal that cancels the magnification ratio, and an electronic unit that changes the magnification of the imaging signal according to the magnification control signal. It is configured to include a zoom changing unit. With such a configuration,
The optical image whose magnification is determined by the zoom lens is automatically focused by the focus lens. This autofocused optical image is output as an electrical imaging signal by the imaging signal generation unit. Here, during the wobbling operation of the focus lens, the magnification of the focus adjustment unit is obtained from the optical position of the zoom lens, and a magnification control signal that cancels out the magnification is output from the magnification control unit. In accordance with the magnification control signal, the magnification of the imaging signal is changed by the electronic zoom changing unit.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating an imaging apparatus according to an embodiment of the present invention. As shown in FIG. 1, the imaging apparatus includes a zoom unit 1 that changes the magnification of an optical image, a focus adjustment unit 2 that adjusts the focus of the optical image,
An imaging signal generation unit 3, a microcomputer 4 (magnification control unit), an electronic zoom change circuit 5 (electronic zoom change unit), and a monitor 6
Is provided.

The variable power unit 1 includes a variable power zoom lens 10.
And a stepping motor 11 for controlling the movement of the zoom lens 10 and a driver 12. The zoom lens 10 is mounted so as to be movable in the direction of the arrow, and is capable of wide-angle shooting and telephoto shooting. The stepping motor 11 is attached to a drive shaft (not shown) of the zoom lens 10, and rotates the rotation shaft to move the zoom lens 10. The driver 12 is a device for driving the stepping motor 11, and is controlled by a control signal C 1 from the microcomputer 4.
Is driven to position the zoom lens 10 at the optical position indicated by the control signal C1.

The focus adjustment section 2 is composed of a focus lens 20 for focus adjustment, a stepping motor 21 for controlling the movement of the focus lens 20, and a driver 22. The focus lens 20 is attached to the subsequent stage of the zoom lens 10, and focuses an optical image from the zoom lens 10 by moving the position (optical position) of the focus lens 20 in the direction of the arrow. The stepping motor 21 is connected to a rotation axis (not shown) of the focus lens 20, and moves the focus lens 20 to a predetermined optical position by rotating the rotation axis. The driver 22 is a device for driving the stepping motor 21, and includes a control signal C from the microcomputer 4.
In step 2, the stepping motor 21 is driven, and the focus lens 20 is positioned at the optical position indicated by the control signal C2.

The imaging signal generator 3 converts an optical image into an electrical imaging signal V4. The imaging device 3 is a CCD device 31 for performing photoelectric conversion, an automatic gain control (AGC) 32 for performing gain control, and an A / D converter. It includes a converter 33, a digital signal processing circuit 34 for outputting a digital image signal, and a contrast signal detection circuit 36. The CCD element 31 is arranged downstream of the focus lens 20, forms an optical image from the focus lens 20 on a light receiving surface, and outputs this as an electric signal V1. Also, A
The GC 32 is a device that controls the gain so that the electric signal V1 from the CCD element 31 has a predetermined gain and outputs the signal as a video signal V2. The A / D converter 33 converts the video signal V2 into a digital signal. , Digital video signal V3
Is a device that outputs as Digital signal processing circuit 34
Has a function of performing predetermined signal processing on the digital video signal V3, outputting an imaging signal V4, and outputting the luminance signal V5 to the contrast signal detection circuit 36. The contrast signal detection circuit 36 is a digital signal processing circuit 3
4 has a function of passing a high-frequency component of the luminance signal V5 from 4 and outputting a contrast signal V6 indicating sharpness based on the high-frequency component.

The microcomputer 4 is connected to the driver 12 of the magnification section 1, the driver 22 of the focus adjustment section 2, the contrast signal detection circuit 36, and the electronic zoom change circuit 5, and the magnification change of the optical image occurring at the time of wobbling operation. (Magnification)
Has a function as a magnification control unit that cancels out, and a function to control the zoom unit 1 and the focus adjustment unit 2. The control of the scaling unit 1 is performed by outputting a control signal C1. The control signal C1 is obtained from a zoom magnification signal from a control unit (not shown). Specifically, the optical position of the zoom lens 10 is calculated from the magnification information of the zoom lens 10 included in the zoom magnification signal, and the control signal C1 corresponding to this optical position is calculated.
Is obtained, and the control signal C1 is output to control the zoom lens 10 to move to a predetermined optical position.

The control of the focus adjustment unit 2 is performed by changing the optical position of the focus lens 20 so that the contrast signal V from the contrast signal detection circuit 36 is changed.
A so-called auto focus control for maximizing 6 is performed.
FIG. 2 is a diagram illustrating a relationship between the optical position of the focus lens 20 and the intensity of the contrast signal V6 when the focus adjustment unit 2 is controlled. As shown in FIG. 2, the intensity curve A of the contrast signal V6 has a maximum value T when the image is in focus, and becomes smaller than the maximum value T when the image is out of focus. The microcomputer 4 functions to find the optical position (focus position) of the focus lens 20 at which the contrast signal V6 becomes maximum while wobbling the focus lens 20.

For example, the focus lens 20 is initially shown in FIG.
If the optical position P1 is at the optical position P1, the wobbling is started from this position. That is, the focus lens 20 is vibrated right and left at the optical position P1, and a direction in which the contrast signal V6 from the contrast signal detection circuit 36 increases is found. Then, the focus lens 20
To the contrast signal V6 as shown by the arrow a in FIG.
Move in the increasing direction. When such wobbling and movement of the focus lens 20 are performed gradually, the focus lens 20 reaches a focus position P2 where the contrast signal V6 is maximized. At this time, this position makes the contrast signal V6 truly maximize. Cannot be determined. Therefore, the microcomputer 4 moves the focus lens 20 in the direction of the arrow b while wobbling. Then, since the contrast signal V6 decreases, the microcomputer 4 reversely moves the focus lens 20 in the direction of arrow c, and finally wobble at the focus position P2. Since the wobbling time at the in-focus position P2 is, for example, 3 seconds, the magnification of the imaging signal V4 changes for a long time.

FIG. 3 is a diagram showing a change (magnification) of the magnification of the optical image when the focus lens 20 is wobbled by a unit optical distance (for example, 20 μm). FIG.
, Curve B shows the magnification when the focus lens 20 wobbles by the unit optical distance. Here, the horizontal axis in FIG. 3 is the optical position of the zoom lens 10, and the left side indicates the wide-angle side and the right side indicates the telephoto side. That is, FIG. 3 means that, for example, when the focus lens 20 is wobbled by a unit optical distance when the zoom lens 10 is at the optical position P4, the optical image is enlarged to 1.02 times.

The microcomputer 4 generates a magnification control signal C3 for canceling the magnification change based on the magnification curve B. Specifically, it has a magnification scale curve B shown in FIG. 3 as a table, and based on this table, obtains a magnification Z0 at the time of unit optical distance wobbling from the current optical position of the zoom lens 10, By calculating the following equation (1),
Assume an actual scaling factor Z1.

(Equation 1) For example, the zoom lens 10 is located at the optical position P4, the unit optical distance of wobbling is 20 μm, and the actual wobbling amplitude of the focus lens 20 is 40 μm.
If m, the above equation (1) is represented by the following equation (2), and it is assumed that the actual scaling factor Z1 is 1.0404.

(Equation 2) In other words, it is assumed that there is a possibility that an image repeatedly increasing and decreasing by about 4% due to wobbling may be visually recognized on the monitor 6. Therefore, the microcomputer 4 obtains a magnification control signal C3 for canceling the change in magnification from the following equation (3), and outputs it to the electronic zoom changing circuit 5. Magnification control signal C3 = 1 / variable magnification Z1 (3)

The electronic zoom changing circuit 5 is a circuit for changing the magnification of the image indicated by the image pickup signal V4 according to the magnification control signal C3. That is, as shown in the following equation (4), the imaging signal V of the magnification Z1 input to the electronic zoom changing circuit 5
By multiplying the value indicated by the magnification control signal C3 with respect to 4, a change in magnification due to wobbling is suppressed. Z1 × (1 / Z1) = 1 (4)

Next, the operation of the image pickup apparatus according to this embodiment will be described. When the control signal C1 from the microcomputer 4 is input to the driver 12, the zoom lens 10 is positioned at a predetermined optical position so that the zoom magnification indicated by the control signal C1 is obtained. Concurrently, when the control signal C2 from the microcomputer 4 is input to the driver 22, the focus lens 20 is positioned at the focal point indicated by the control signal C2. As a result, the optical image focused at a predetermined magnification is input to the CCD element 31, output as an image pickup signal V4 through the AGC 32, the A / D converter 33, and the digital signal processing circuit 34, and from the contrast signal detection circuit 36. The contrast signal V of the maximum intensity is supplied to the microcomputer 4.
6 is input. By the way, during the autofocus operation, the wobbling operation is performed as described above, so that the magnification of the imaging signal V4 changes, and the size of the image displayed on the monitor 6 changes. However, in the imaging device of this embodiment, since the microcomputer 4 cancels such a change in magnification of the video,
The image at the time of wobbling is kept at a fixed size. That is, in the microcomputer 4, the magnification ratio curve B
Of the zoom lens 10 at the time of wobbling of the unit optical distance of the focus lens 20 based on the current optical position of the zoom lens 10 shown in the table, the actual zoom ratio Z1 was calculated from the zoom ratio Z0. Thereafter, a magnification control signal C3 indicating the reciprocal of the magnification Z1 is output to the electronic zoom changing circuit 5. As a result, in the electronic zoom change circuit 5, the change in magnification of the image of the image pickup signal V4 is canceled, and the image displayed on the monitor 6 is always kept at a constant size even during wobbling.

[0017]

As described above in detail, according to the imaging apparatus of the present invention, even if the magnification of the optical image is changed by the focus adjustment unit during the wobbling operation, a magnification control signal for canceling the magnification is generated. Since the optical image output to the zoom changing unit and scaled is returned to the original magnification again by the electronic zoom changing unit, an image of a fixed size can be always output, and as a result, a small and high magnification is obtained. There is an excellent effect that it is possible to provide the above-mentioned device.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an imaging apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the optical position of a focus lens and the intensity of a contrast signal.

FIG. 3 is a diagram showing a magnification.

FIG. 4 is a block diagram showing a conventional imaging device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnification part, 2 ... Focus adjustment part, 3 ... Image signal generation part, 4 ... Magnification control part, 5 ... Electronic zoom change circuit, 6
…monitor.

Claims (2)

[Claims] 1. A magnification changing section for changing a magnification of an optical image by changing an optical position of a zoom lens, and a focus adjusting section for performing auto-focusing of the optical image by changing an optical position of a focus lens. An imaging signal generation unit that forms an optical image as an electrical imaging signal formed by the focus adjustment unit; and a wobbling operation of the focus lens, which changes a magnification of the focus adjustment unit from an optical position of the zoom lens. An image pickup apparatus comprising: a magnification control unit that outputs a magnification control signal that cancels out the magnification ratio; and an electronic zoom change unit that changes the magnification of the imaging signal in accordance with the magnification control signal. 2. The imaging apparatus according to claim 1, wherein the magnification control unit has a table indicating a magnification corresponding to an optical position of the zoom lens and an amount of movement of the focus lens. A magnification control signal at the time of the wobbling operation, and a magnification control signal indicating a reciprocal of the magnification.