Photography – Camera shake sensing – Having stabilization system
Reexamination Certificate
1999-08-20
2001-07-17
Perkey, W. B. (Department: 2851)
Photography
Camera shake sensing
Having stabilization system
Reexamination Certificate
active
06263162
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus such as an image-shake preventing apparatus for preventing the shake of an image, and to a control method therefor.
2. Description of Related Art
It is known that, in an image pickup apparatus such as a small-sized video camera, a picked-up object image shakes due to the vibration of the image pickup apparatus, so that a video image intolerable to view might be outputted or recorded.
In particular, in such a kind of image pickup apparatus, it has become general these days that a zoom lens capable of continuously varying the focal length without changing the image point position is mounted in the image pickup apparatus, and, in recent years, an image pickup apparatus having a high zoom magnification ratio of ten or more times has widely come into the market. However, such an image pickup apparatus has a drawback that, when an object image is picked up with the setting of the telephoto side, which is set for the larger zoom magnification, a conspicuous shaking of the object image would occur.
Therefore, as measures to solve the above drawback, an image pickup apparatus having mounted therein an image pickup optical system having image-shake correcting means has been developed so far and has already been put on the market.
FIG. 18
is a conceptual diagram schematically showing the above-mentioned image pickup optical system, which is denoted by reference numeral
200
. In the image pickup optical system
200
, there are disposed, in order, a fixed lens
201
securely fixed to a lens barrel (not shown), a variator lens
202
arranged to move in the horizontal direction on an optical axis “c” as indicated by an arrow “a”, a shift lens
203
arranged to move two-dimensionally within a plane perpendicular to the optical axis “c” (in the direction indicated by an arrow “b”, a focusing lens
204
having the focus adjusting function and the function of correcting the movement of a focal plane resulting from the movement of the variator lens
202
, and an image sensor
205
on which to form an object image. Further, in the respective predetermined positions adjacent to the shift lens
203
, there are disposed an actuator
206
arranged to drive the shift lens
203
and a position detecting sensor
207
arranged to detect the position of the shift lens
203
.
In the image pickup apparatus
200
, even if, as shown in FIG.
19
(
a
), the optical axis “c” deviates from a central axis “c′” of the image pickup optical system
200
due to the vibration thereof as much as a deviation angle e, it is possible to make the optical axis “c” and the central axis “c′” of the image pickup optical system
200
geometrically coincident with each other on the downstream side of the shift lens
203
, by driving the actuator
206
to move the shift lens
203
as indicated by an imaginary line in FIG.
19
(
b
). Accordingly, the above-mentioned deviation angle &thgr; is corrected by an optical processing, so that the object image is formed on the image sensor
205
as a light flux having no shaking.
FIG. 20
is a block diagram showing the arrangement of a conventional image pickup apparatus which corrects an image shake by means of the image pickup optical system
200
.
In the image pickup optical system shown in
FIG. 20
, when a power supply switch
208
is turned on, a mode microcomputer
209
notifies a main microcomputer
210
of the turning-on of the power supply switch
208
. Then, having determined that the power supply has been turned on, the main microcomputer
210
starts its control operation.
Subsequently, a vibration signal forming circuit
211
, which has detected the vibration of the body of the image pickup apparatus, forms a vibration signal and supplies the vibration signal to a vibration correcting circuit
212
. In the vibration correcting circuit
212
, the analog vibration signal is converted into a digital vibration signal by an A/D converter
213
, and, then, a predetermined low-frequency component is removed from the digital vibration signal by a high-pass filter (HPF)
214
. After that, the phase and gain of an output signal of the HPF
214
are corrected by a phase/gain correcting circuit and an output signal of the phase/gain correcting circuit
215
is integrated by an integration circuit
216
to calculate and output a correction target value.
The correction target value outputted from the vibration correcting circuit
212
is converted into an analog value by a D/A converter
217
and is then supplied to an adder
218
. At the adder
218
, the analog correction target value is added to a feedback signal supplied from the position detecting sensor
207
through an amplifier
219
. Then, an output signal of the adder
218
is supplied to a driving circuit
220
. The driving circuit
220
issues a driving signal to the actuator
206
to drive the shift lens
203
.
When the shift lens
203
is driven by the actuator
206
, as described above, the deviation angle e is optically corrected, so that the object image is formed on the image sensor
205
as a light flux having no shaking.
Further, an electric signal obtained through the photo-electric conversion by the image sensor
205
is supplied to a video signal processing circuit
222
via a camera signal processing circuit
221
. Then, a video signal produced by the video signal processing circuit
222
is outputted to an output terminal
223
so as to be converted into a visible video image on the display screen, and, at the same time, is recorded, as video information in the form of an RF signal, on a recording medium such as a magnetic tape by a recorder
224
.
Incidentally in the above-mentioned image pickup apparatus, the actuator
206
for driving the shift lens
203
is composed of a voice coil motor.
More specifically, the voice coil motor is disposed in a predetermined position adjacent to the shift lens
203
. By causing current to flow to the voice coil motor to generate an electromagnetic force, the shift lens
203
is made to float, and by varying the electromagnetic force according to an output of the adder
218
, the shift lens
203
is made to two-dimensionally move within a plane perpendicular to the optical axis “c” in the vertical direction (in the pitching direction) and in the horizontal direction (in the yawing direction).
However, since, in the conventional image pickup apparatus, as described above, the actuator
206
is composed of a voice coil motor, the shift lens
203
is held in a floating state by the voice coil motor when the voice coil motor is a conductive state with the power supply switch
208
turned on, but, when the power supply is turned off, the holding force for the shift lens
203
by the voice coil motor is canceled, so that the shift lens
203
drops due to its own weight. As a result, a lens holding frame which holds the shift lens
203
collides with an inner wall of the lens barrel to generate a collision sound, which is offensive to the ear.
Further, since the optical axis “c” decenters due to the movement of the shift lens
203
, for example, if the power supply is turned off during the process of an image pickup operation of the image pickup apparatus, there is a possibility that a video image having an unnatural motion is outputted or recorded on the recording medium.
BRIEF SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, there are provided an apparatus such as an image-shake preventing apparatus and a control method therefor, in which an image-shake preventing unit is caused to gradually come into contact with a movable-range end when an image-shake preventing operation is ended, so that it is possible to prevent the image-shake preventing unit from colliding with the movable-range end to generate a collision sound when the image-shake preventing operation is ended.
In accordance with another aspect of the invention, there are provided an apparatus such as an image-shake preventing apparatus and a control method therefor, in which an image-shake
Ishikawa Yoshikazu
Yamazaki Tatsuya
Canon Kabushiki Kaisha
Perkey W. B.
Robin Blecker & Daley
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