Photography – Camera shake sensing – Having stabilization system
Reexamination Certificate
2000-01-06
2001-08-21
Perkey, W. B. (Department: 2851)
Photography
Camera shake sensing
Having stabilization system
Reexamination Certificate
active
06278842
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image-shake correcting device for use in performing image-shake correction in a photographic camera, a video camera or the like and, more particularly, to an image-shake correcting device capable of preventing an abnormal motion of an image from occurring at the instant when the image-shake correcting device is turned on or off.
2. Description of the Related Art
In the field of photographic apparatuses such as still cameras or video cameras, various operations, such as exposure setting and focus adjustment, have heretofore been automated and an increased number of functions have been incorporated into one photographic apparatus. Accordingly, even beginners have become able to easily enjoy high-quality photography.
FIG. 1
is a block diagram showing one example of an image-shake correcting device.
The image-shake correcting device shown in
FIG. 1
is arranged to cancel an image shake by optically displacing an optical axis. Specifically, if a vibration occurs in a photographic apparatus such as a still camera or a video camera, the vibration is detected by an angular-velocity detector
1
which includes an angular-velocity sensor, such as a vibration gyro, mounted in the photographic apparatus, and the angular-velocity detector
1
outputs a signal corresponding to the detected vibration. The DC component of the angular-velocity signal outputted from the angular-velocity detector
1
is cut off by a DC cutoff filter
2
, and the obtained AC component, i.e., a vibration component, is passed through the DC cutoff filter
2
. The DC cutoff filter
2
may use a high-pass filter (hereinafter referred to as “HPF”) capable of cutting off an arbitrary band of a signal.
The angular-velocity signal outputted from the DC cutoff filter
2
is amplified to an appropriate sensitivity level by an amplifier
3
, and the phase and the gain of the angular-velocity signal are corrected by a correction circuit
4
made up of an HPF and a high-frequency compensation filter. The output of the correction circuit
4
is integrated by an integrator
5
, and an angular-displacement signal is inputted to an adder
6
, in which the angular-displacement signal and a detected-position output are added together. In accordance with the sum outputted from the adder
6
, a microcomputer (&mgr;COM)
7
outputs to a driving circuit
8
an instruction to drive image correcting means (hereinafter referred to as “VAP” (variable angle prism))
9
, thereby driving the VAP
9
.
In the meantime, a position of the VAP
9
is detected by a position detecting sensor
10
which monitors the position of the VAP
9
, and the detected-position output of the position detecting sensor
10
is amplified by an amplifier
11
. As described above, the amplified detected-position output is added to the output of the integrator
5
in the adder
6
, and the sum outputted from the adder
6
is sent to the microcomputer
7
and the microcomputer
7
executes control of the VAP
9
in accordance with the inputted sum. In addition, an image-shake correcting switch
12
is provided for turning on or off the operation of the VAP
9
. In accordance with the state of the image-shake correcting switch
12
, a switch
13
is turned on or off, so that the operation of the VAP
9
is started or stopped.
An image-shake correcting operation which is performed by the VAP
9
and the driving circuit
8
will be described below.
FIG. 2
is a schematic view showing the structure of the VAP
9
.
As shown in
FIG. 2
, the VAP
9
includes two transparent parallel plates
740
a
and
740
b
which are opposed to each other, a transparent elastic material or inactive liquid
742
which has a high refractive index (n) and is charged into the gap between the transparent parallel plates
740
a
and
740
b
, and a sealing material
741
, such as resin film, which surrounds and elastically seals the gap between the transparent parallel plates
740
a
and
740
b
so as to swingably hold the transparent parallel plates
740
a
and
740
b
. An image shake is corrected by swinging the transparent parallel plates
740
a
and
740
b
of the VAP
9
and displacing the optical axis thereof.
FIG. 3
is a schematic view showing the state of passage of an incident light flux through the VAP
9
shown in FIG.
2
.
FIG. 3
is a schematic view showing the state of passage of an incident light flux
744
through the VAP
9
when the transparent parallel plate
740
a
is rotated by an angle &sgr; about a swinging or rotating shaft
701
(
711
). The light flux
744
which is made incident on the VAP
9
along an optical axis
743
is made eccentric (deflected) by an angle &phgr; on the same principle as a prism.
FIG. 4
is a schematic view showing the construction of a VAP driving mechanism.
FIG. 4
shows one example of the arrangement of the VAP
9
and the driving circuit
8
. In this arrangement, a voice coil is used in a driving system, and feedback control is performed on the basis of an angular displacement detected by a position detecting sensor.
As shown in
FIG. 4
, the VAP
9
is secured to a lens barrel
702
via a holding frame
707
so that the VAP
9
can be turned about the axis of the rotating shafts
701
and
711
. A coil
712
, a yoke
713
and a magnet
715
constitute a voice-coil type actuator, which can vary the apex angle of the VAP
9
about the rotating shaft
711
by causing a current to flow in the coil
712
.
A slit
710
for detecting the displacement of the VAP
9
is arranged to displace its position while turning concentrically to the rotating shaft
711
together with the holding frame
707
, i.e., the VAP
9
. The slit
710
, a PSD (position detecting element)
709
and a light-emitting diode
708
constitute a position detecting sensor. In the position detecting sensor, light emitted from the light-emitting diode
708
is received by the PSD
709
to detect the displacement of the slit
710
, thereby detecting the angular displacement of the apex angle of the VAP
9
.
The light flux the incident angle of which has been varied by the VAP
9
in the above-described manner is focused on the image pickup surface of an image pickup element
704
by a photographic lens unit
703
. Incidentally, reference numeral
705
denotes another rotating axis which is at right angles to the axis of the rotating shafts
701
and
711
of the holding frame
707
.
FIG. 5
is a block diagram showing a control circuit for controlling the driving of the VAP
9
.
In the feedback system of the control circuit shown in
FIG. 5
, a control signal
720
for image-shake correction is supplied from the microcomputer
7
to a voice-coil type of actuator
724
through an amplifier
722
and an driver
723
for driving the actuator
724
. The driver
723
drives the actuator
724
in accordance with the control signal
720
, so that the actuator
724
controls the VAP
9
to vary the apex angle thereof by a predetermined amount.
The angular displacement of the apex angle of the VAP
9
is detected by the position detecting sensor
10
made up of the PSD
709
and the associated constituent elements, and the detected-position output of the position detecting sensor
10
is supplied to an adder
725
. In the adder
725
, the detected-position output is added to the control signal
720
which is supplied from the microcomputer
7
and of opposite polarity to that of the detected-position output. The control system operates so that the control signal
720
for image-shake correction which is outputted from the microcomputer
7
and the output signal of the position detecting sensor
10
can become equal to each other. Accordingly, the VAP
9
is driven so that the control signal
720
can coincide with the output of the position detecting sensor
10
, whereby the VAP
9
is controlled so as to take the position specified by the microcomputer
7
.
However, the above-described example involves a number of problems. A first problem is that the switch
13
for turning on or off the operation
Ohkawara Hiroto
Yamazaki Tatsuya
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Perkey W. B.
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