JPH11258652A - Optical device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] With an optical shake correction function, brightness fluctuation is large at the periphery of a screen, resulting in an extremely unsightly and inferior image. There is also a problem that the same development as described above occurs in the electronic shake correction function. SOLUTION: In a variable power optical system for camera shake correction, an opening diameter of an aperture for controlling an amount of light beam passing through the optical system is limited according to a focal length.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device having a function of correcting a camera shake caused by a change in a relative angle between a subject and an optical device.

[0002]

2. Description of the Related Art Conventionally, various optical devices for correcting camera shake or image shake have been proposed. For example, as shown in FIG.
An optical device has been proposed which is arranged in front of an optical system consisting of 01 to 104 and an aperture 105 and corrects image blur by a variable apex angle prism 100 before a light beam P from a subject enters this optical system. Reference numeral 106 denotes lens groups 101 to 104
And a fixed lens barrel supporting the diaphragm 105, and 107 is a fixed lens barrel 1
The CCD is an image sensor that converts an optical image provided on the focal plane at the rear end of the camera 06 into an electric signal.

However, in the above optical device, the variable apex angle prism 100 is located at the widest point of the light beam P passing through the optical system.
This is disadvantageous for downsizing the optical device.

Therefore, in order to reduce the size of the optical device, an optical device in which this variable apex angle prism is disposed between two lens groups inside an optical system including a plurality of lens groups, The lens group having the position is moved in the direction perpendicular to the optical axis to correct the shake. An optical device that performs an optical image blur correction function such as a so-called lens shift method, or a CCD that is larger than the area actually required as an image sensor (of course, a large optical system in which the image circle covers the entire CCD) Is necessary), and the readout position is made variable according to the camera shake information to correct the shake. An optical device having an electronic blur correction function called so-called electronic image stabilization has already been proposed.

[0005]

The conventional optical device having the image blur correction function is configured as described above.
For example, convex / concave / convex / convex lens groups 111 to 114 shown in FIG.
And the optical system of the stop 115, the off-axis light beam b with respect to the on-axis light beam a passing through the center of the optical system depends on the effective diameter of the lenses 111 and 114 as shown by arrows A or B. Since the light beam is blocked, the light beam incident from a larger angle (corresponding to the periphery of the screen) becomes thinner.
Therefore, on the imaging surface 116, the image becomes rapidly darker toward the periphery. A phenomenon of so-called vignetting causes a decrease in the amount of peripheral light.

[0006] In the above-mentioned optical shake correction function for correcting image shake by deflecting a light beam inside the optical system, when the relative angle between the subject and the optical device changes, the image of the subject on the image plane is changed. Is corrected so that the relative angle between the subject and the optical device changes, the degree of vignetting of the light flux at each point of the subject image on the imaging surface changes, and the light amount distribution of the subject image changes Changes.

FIG. 9 shows such a state, in which the horizontal axis represents the imaging position and the vertical axis represents the brightness. The dashed line indicates the light amount distribution in the initial state before the relative angle between the subject and the optical device changes, and the solid lines a and b indicate the light amount distribution when shake correction is performed when the relative angle changes alternately to the left and right, for example. Is shown. Thus, correcting the actual continuous camera shake,
Even if the subject is corrected and stopped on the screen, the difference between the light amount distributions indicated by the solid lines a and b causes a change in the brightness of the screen synchronized with the camera shake. In particular, brightness fluctuation was large in the peripheral portion of the screen, resulting in an extremely unsightly image of poor quality.

[0008] Also, in the electronic shake correction function,
As shown in FIG. 8, the lens groups 111 to 114 and the stop 1
Since the relationship between the optical system 15 and the imaging surface 116 does not change, the light amount distribution with respect to the imaging surface 116 does not change. However, when the relative angle between the subject and the optical device changes and the subject image moves, Change the cut-out position afterward (for example, cut-out position 1 and cut-out position 2 in FIG. 10).
Therefore, there is a problem that a phenomenon similar to that of the optical image blur correction function occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and it is intended to reduce the brightness fluctuation around the screen which occurs in synchronization with the camera shake correction. It is an object of the present invention to provide an optical device capable of reducing a difference in brightness between the center of the screen and the periphery of the screen near the conspicuous telephoto end and obtaining a high-quality, easy-to-view image.

[0010]

According to the present invention, there is provided an optical device having the following configuration. (1) An optical apparatus characterized in that the aperture diameter of an aperture for controlling the amount of light beam passing through a variable power optical system for camera shake correction is limited according to the focal length. (2) The optical device according to claim 1, wherein the on-axis light beam is restricted by a stop near the telephoto end of the variable power optical system that receives light beams on and off the optical axis. (3) The optical device according to (1), wherein the on-axis light flux is restricted by a sub-aperture provided close to a main aperture. (4) The shift amount of the lens group shifted vertically to the optical axis is corrected by the position information of the variable power optical system, and the movement of the image due to the inclination of the variable power optical system is canceled by shifting the lens group. The optical device according to claim 1. (5) The optical device according to (1), wherein when the camera shake correction is not performed, the restriction of on-axis light flux by the stop is stopped.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIGS. 1 and 2 show a variable power optical system for correcting camera shake having a configuration of convex, concave, convex and convex lens groups 1 to 4 to which the present invention is applied. FIG. 1 shows a Te1e end (telephoto end), and FIG. The state at the Wide end (wide-angle end) is shown. The lens group 1 is a fixed lens group, and the lens group 2 is a lens group for zooming that moves back and forth to perform zooming. The lens group 3 moves (shifts) in the direction perpendicular to the optical axis to shift the light beam, and the lens group 4 moves forward and backward to adjust the focus, and the focusing lens group 5 moves to the optical system. Reference numeral 6 denotes a focus surface on which an image of a subject is formed.

Further, a and b represent the luminous flux at the time of opening the aperture on the axis (the center part of the screen) and the outermost part (the peripheral part of the screen) off the axis, respectively. In FIG. 1 showing the aperture open state at the Te1e end, in the on-axis light beam a, the light beam that has passed through the lens group 1 is largely blocked by the stop 5 in the peripheral portion, but in the off-axis light beam b, the light beam is blocked by the stop 5. The focus surface 6 has been reached without being performed.

This will be further described with reference to FIG. 3, the horizontal axis represents the imaging position, the vertical axis represents the brightness, the solid line c represents the light amount distribution on the focus plane 6 in FIG.
Is a light amount distribution when the lens is opened to a position where the on-axis light flux a is not blocked. A broken line e has a size such that only the on-axis light flux that passes through the open diameter of the diaphragm 5 in FIG.
Is a light amount distribution when the diameter of the light-emitting element is reduced. That is,
The diameter of the lens group 1 is increased to allow a large amount of on-axis and off-axis light beams to enter, and at least the on-axis light beam is reduced
, The difference in brightness between the central part and the peripheral part of the screen is reduced. FIG. 4 shows the fluctuation of the light quantity distribution when the camera shake correction is actually performed. C ′ and c ″ and d ′ and d ″ are the fluctuations of the light quantity distribution in the state of the diaphragm 5 of FIGS. In particular, it can be seen that the brightness fluctuation around the screen is greatly improved by limiting the opening diameter of the diaphragm 5 as shown by the brightness fluctuation 1 and the brightness fluctuation 2.

FIG. 5 is a schematic diagram showing the configuration of an optical device having a function of correcting camera shake. In FIG. 1, reference numeral 7 denotes a fixed lens barrel that supports the lens group 1 and 8 denotes a moving frame that supports the lens group 2 with respect to the lens groups 1 to 4, the stop 5, and the focus surface 6, and a known bar sleeve structure. And is movable in the optical axis direction, and is driven by a stepping motor by a known rack and feed screw mechanism.

Reference numeral 9 denotes a shift frame for supporting the lens group 3, and the lens group 3 can be moved in a direction perpendicular to the optical axis 0 by a guide mechanism (not shown) formed between the shift frame and the holding frame 10. The position of the shift frame 9 is controlled in the pitch direction and the yaw direction by a drive unit and a position detection unit (not shown).

Reference numeral 11 denotes a moving frame for supporting the lens group 4, which has a known bar sleeve structure and is movable in the optical axis direction, and is driven by a known rack and feed screw mechanism by a stepping motor. Reference numeral 12 denotes a known diaphragm device that supports and drives the diaphragm 5, and includes a plurality of sickle-shaped diaphragm blades arranged in the circumferential direction, and simultaneously rotates the respective diaphragm blades to form a substantially circular diaphragm opening shape. The so-called iris diaphragm that forms the iris is preferable.

Reference numeral 13 denotes a CCD which is an image pickup device for converting an optical image arranged on the focusing surface 6 into an electric signal, and reference numeral 14 denotes a fixed frame which holds the CCD 13 and other moving mechanisms. The electric signal a read from the CCD 13 becomes a video signal by the camera signal processing circuit 15.

Reference numeral 16 denotes a microcomputer for controlling lens driving. When the power is turned on, the microcomputer 16 monitors the outputs of the focus reset circuit 17 and the zoom reset circuit 18 and rotates the respective stepping motors by the focus motor drive circuit 19 and the zoom motor drive circuit 20 to move the moving frame 11 and the moving frame. The frame 8 is moved in the optical axis direction. The outputs of the focus reset circuit 17 and the zoom reset circuit 18 reach their respective movable frames to a preset position (a light shielding member provided on the movable frame shields a light emitting portion of a photo interrupter provided on a fixed portion, or The microcomputer can know the absolute position of each lens group by counting the number of drive steps of the subsequent stepping motor in the microcomputer based on the position of the lens group. As a result, accurate focal length information can be obtained. Reference numeral 21 denotes an aperture drive circuit for opening and closing the aperture 5, and the aperture diameter of the aperture is controlled based on brightness information b of a video signal taken into the microcomputer 16. The aperture diameter at that time is detected by the aperture value detection circuit 22 and taken into the microcomputer 16.

In this aperture control, the horizontal axis is the focal length,
As shown in FIG. 6, the vertical axis represents the aperture diameter of the aperture, and the aperture diameter of the aperture is limited according to the focal length (the area indicated by hatching is the area where the aperture is not opened). The difference in brightness is kept small. Due to the configuration of the optical system, Wide
Although the difference in brightness between the center of the screen and the periphery of the screen is smaller at the Te1e end than at the end, the amount of motion of the image on the imaging surface for the same camera shake amount is larger at the Te1e end in proportion to the focal length. The brightness fluctuation amount on the screen with respect to the actual camera shake becomes more problematic at the Te1e end, and it is necessary to further improve the light amount distribution near the Te1e end.

Reference numerals 23 and 24 denote a pitch (vertical tilt angle) and yaw (horizontal tilt angle) angle detection circuits of the optical device. The angle is detected by an angular velocity sensor such as a vibrating gyroscope fixed to the optical device. This is done by integrating the output of The outputs of the two angle detection circuits 23 and 24, that is, information on the tilt angle of the optical device are taken into the microcomputer 16.

Reference numerals 25 and 26 denote pitch (vertical) and yaw (horizontal) coil drive circuits for moving the lens group 3 perpendicular to the optical axis in order to perform camera shake correction. A coil is arranged in the gap of the circuit, and a driving force for shifting the lens group 3 is generated by a so-called moving coil configuration.

Reference numerals 27 and 28 denote pitch (longitudinal) and yaw (horizontal) position detecting circuits for detecting the amount of shift of the lens group 3 with respect to the optical axis. For example, a light emitting element and a light receiving element are fixed facing each other. In the meantime, a slit provided integrally with the shift frame 9 is arranged to obtain the shift amount of the lens group 3 as an electric signal. The shift amount information is also taken into the microcomputer 16.

Next, the operation will be described.

When the lens group 3 moves perpendicularly to the optical axis, the passing light beam is bent, and the position of the image of the subject formed on the CCD 13 moves. The amount of movement of the image at this time is controlled by the microcomputer 16 so as to move by the same size in the direction opposite to the direction in which the image moves due to the actual tilt of the optical device. (Even though), the so-called camera shake correction in which the formed image does not move can be realized.

In the microcomputer 16, the tilt signal of the optical device obtained by the pitch angle detection circuit 23 and the yaw angle detection circuit 24 and the shift amount of the lens group 3 obtained by the pitch position detection circuit 27 and the yaw position detection circuit 28 The signals are subtracted, and the shift frame 9 is driven by the pitch coil drive circuit 25 and the yaw coil drive circuit 26 with the respective difference signals. By this control, the lens group 3 is driven such that the difference signal becomes smaller, and is maintained at the target position.

In the first embodiment, since the lens group 3 for shifting vertically to the optical axis is closer to the image pickup surface than the lens group 2 for zooming, the moving amount of the image with respect to the shift amount of the lens group 3 is for zooming. It changes depending on the position of the lens group 2, that is, the focal length. Therefore, the shift amount of the lens group 3 is not directly determined based on the tilt signal of the optical device obtained by the pitch angle detection circuit 23 and the yaw angle detection circuit 24, but correction is performed based on the position information of the variable power lens group 2 to perform the correction. In this embodiment, the movement of the image caused by the inclination of the lens group is canceled by shifting the lens group 3. In this embodiment, the stop for changing the amount of light passing through the optical system is electrically limited to limit the stop opening diameter. If camera shake correction is not performed, stop the restriction on the aperture opening diameter.
It can be used as a brighter optical system with the e-end open. In addition, the aperture stop diameter can be limited mechanically by interlocking the movement of the variable power lens group with the sub-aperture provided close to the main aperture.

In the present embodiment, the third lens unit of the variable power optical system having a four-unit configuration including convex, concave, convex, and convex lens units is
Although an optical device that performs camera shake correction by shifting with respect to the optical axis has been described, the optical type and the position of the lens group to be shifted are not limited. The application of the present invention is also effective in an optical shake correction function in which a variable apex angle prism is arranged inside a variable power optical system or an electronic shake correction function called so-called electronic image stabilization. Needless to say, any configuration may be used as long as the function can be achieved.

[0029]

As described above, according to the present invention,
In the variable power optical system for camera shake correction, the aperture diameter for controlling the amount of light flux passing through the optical system is configured to be limited according to the focal length. This has the effect of reducing the difference in brightness between the center of the screen and the periphery of the screen in the vicinity of the telephoto end, which is conspicuous, and achieving an optical device capable of obtaining a high-quality, easy-to-view image.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a state of a Te1e end of a variable power optical system of an optical device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a state of a wide end of a variable power optical system of the optical device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a light amount distribution of the optical device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a change in a light amount distribution of the optical device according to the first embodiment of the present invention.

FIG. 5 is a schematic diagram showing a configuration of an optical device of the present invention having a function of correcting camera shake.

FIG. 6 is a diagram illustrating a restriction on an aperture opening diameter depending on a focal length of the optical device of FIG. 5;

FIG. 7 is a longitudinal sectional view of a conventional optical device having a camera shake correction function.

FIG. 8 is a diagram for explaining a peripheral light amount drop due to vignetting.

FIG. 9 is a diagram showing a change in a light amount distribution.

FIG. 10 is a diagram illustrating a change in brightness of a screen in electronic image stabilization.

[Explanation of symbols]

 1-4 Lens group 5 Aperture 6 Focus surface

Claims (5)

[Claims] 1. An optical apparatus in a variable power optical system for camera shake correction, wherein an opening diameter of an aperture for controlling the amount of light passing through the optical system is limited according to a focal length. 2. The optical device according to claim 1, wherein the on-axis light beam is restricted by a stop near a telephoto end of a variable power optical system that receives light beams on and off the optical axis. 3. The optical device according to claim 1, wherein the on-axis light flux is restricted by a sub-aperture provided close to a main aperture. 4. A shift amount of a lens group shifted vertically to an optical axis is corrected by position information of a variable power optical system,
2. The optical device according to claim 1, wherein the movement of the image due to the inclination of the variable power optical system is canceled by shifting the lens group. 5. The method according to claim 1, wherein when the camera shake correction is not performed, the on-axis light beam restriction by the stop is stopped.
The optical device of claim