Photography – Camera shake sensing – Having stabilization system
Reexamination Certificate
2000-02-08
2002-06-18
Perkey, W. B. (Department: 2851)
Photography
Camera shake sensing
Having stabilization system
C396S419000
Reexamination Certificate
active
06408135
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control device for image blur correction which is applied to an image blur correction device for correcting image blur occurring in an optical equipment, such as a camera.
2. Related Background Art
In existing cameras, because all important photographing operations, such as exposure or focusing operations, are automatically executed, the possibility that failure to perform a desired photographing operation will occur, even by a person not skilled in camera operation, is significantly reduced.
Also, in recent years, a system for preventing hand vibration which is applied to the camera has been studied, and factors that induce photographing error caused by the photographer now have almost been eliminated.
Now, an image blur correction device which prevents hand vibration will be described in brief.
Hand vibration of the camera at the time of photographing normally has a vibration frequency in the range of 1 to 12 Hz. A basic idea for taking a picture without image blur even if such hand vibration occurs at the time of a shutter release is that the vibration of the camera due to hand vibration is detected, and a correction lens is displaced in response to the detected value. Accordingly, in order that a photograph having no image blur can be taken even if the vibration of the camera occurs, it is necessary to first detect vibration of the camera with accuracy and then to correct for image displacement in an optically axial direction due to the hand vibration.
The detection of the vibration (camera vibration) can be theoretically performed by installing in the camera a vibration detection device comprised of a vibration sensor that detects an angular acceleration, an angular velocity, an angular displacement and the like, and a camera vibration detecting circuit that electrically or mechanically integrates the output signals of the vibration sensor so as to output a signal indicating the angular displacement. Then, image blur is corrected by driving a correction optical device that decanters the photographic optical axis on the basis of the above detection information.
Now, an outline of an image blur prevention system having a vibration sensor will be given with reference to FIG.
8
.
FIG. 8
is a schematic diagram showing an image blur correction device that suppresses image blur caused by a camera vertical vibration
81
p
and a camera horizontal vibration
81
y
in a direction indicated by an arrow
81
, in the case where the image blur correction device is mounted on an interchangeable lens of a single-lens reflex camera.
In
FIG. 8
, reference numeral
82
denotes a lens barrel, and
83
p
and
83
y
are vibration detection devices which detect the camera vertical vibration and the camera horizontal vibration, respectively, where the respective vibration detection directions are indicated by reference symbols
84
p
and
84
y
. Reference numeral
85
denotes a correction optical device (reference symbols
86
p
and
86
y
denote coils which give thrust in two directions to the correction optical system
85
in the two directions, respectively, and
87
p
and
87
y
are position detecting elements that detect the position of the correction optical device
85
in the two directions, respectively), and the correction optical device
85
is formed with a position control loop and driven with outputs from the vibration detection devices
83
p
and
83
y
as desired values so as to ensure stability at an image surface
88
.
FIG. 9
is an exploded perspective view showing an example of the structure of the above-described correction optical device
85
, which will be described below.
A back surface projected ear
71
a
of a base plate
71
is inserted into a lens barrel (not shown), and a known lens barrel roller or the like is screwed into a hole
71
b
so as to be fixed to the lens barrel. A second yoke
72
made of magnetic substance is screwed into a hole
71
c
of the base plate
71
by a screw that threads through the hole
72
a
of the second yoke
72
, and permanent magnets (shift magnets)
73
such as neodymium magnets are magnetically adsorbed to the second yoke
72
. Coils
76
p
and
76
y
(shift coils) are inserted into a support frame
75
to which a correction lens
74
is fitted by a C-ring or the like. A first yoke
712
is inserted into positioning holes
712
a
by respective pins of the base plate
71
, and the first yoke
712
is magnetically coupled at its backing surface to the base plate
71
by a magnetic force of the permanent magnets
73
.
One end of an L-shaped shaft
711
is inserted into a bearing portion
75
d
of the support frame
75
, and the other end of the L-shaped shaft
711
is inserted into a bearing portion
71
d
formed in the base plate
71
. Also, the shaft
711
is slidably supported only in directions indicated by arrows
713
p
and
713
y
with respect to the base plate
71
, to thereby regulate the relative rotation (rolling) about the optical axis with respect to the base plate
71
of the support frame
75
.
The coils
76
p
and
76
y
are located within respective closed magnetic circuits formed of the permanent magnets
73
, the first yoke
712
and the second yoke
72
. In this arrangement, when a current is permitted to flow in the coil
76
p
, the support frame
75
is driven in the direction indicated by the arrow
713
p
, whereas when a current is permitted to flow in the coil
76
y
, the support frame
75
is driven in the direction indicated by the arrow
713
y.
When the support frame
75
moves on a plane perpendicular to the optical axis, an incident position of a light emitted from light projecting elements
77
p
and
77
y
and passing through slits
75
ap
and
75
ay
is changed on the position detecting elements
78
p
and
78
y
. In general, when the outputs of the position detecting element
78
p
and
78
y
are amplified by ICs
731
p
and
731
y
and the coils
76
p
and
76
y
are driven by the amplified outputs, the support frame
75
is driven so that the outputs of the position detecting elements
78
p
and
78
y
are changed. In this example, the-drive directions (polarities) of the coils
76
p
and
76
y
are set so that the outputs of the position detecting elements
78
p
and
78
y
become small (negative feedback), the support frame
75
is stabilized by the drive forces of the coils
76
p
and
76
y
at a position where the outputs of the position detecting elements
78
p
and
78
y
become substantially zero.
The above-mentioned method of driving the support frame
75
by negatively feeding back the position detection output is called “position control manner”, and for example, when a desired value (for example, a hand vibration angle signal) is mixed with the ICs
731
p
and
731
y
from an external source, the support frame
75
is extremely faithfully driven in accordance with the desired value.
Actually, the outputs of differential amplifiers
731
cp
and
731
cy
are supplied to a main substrate (not shown) through a flexible substrate
716
, subjected to A/D conversion and then taken in a microcomputer (not shown).
The A/D converted outputs are appropriately compared with the desired value (hand vibration angle signal) and amplified within the microcomputer, and then subjected to leading phase compensation (for more stabilizing position control) through a known digital filter manner. Thereafter, the signals subjected to the leading phase compensation again pass through the flexible substrate
716
, and are then input to an IC
732
(for driving the coils
76
p
and
76
y
). The IC
732
conducts known PWM (pulse width modulation) drive on the coils
76
p
and
76
y
on the basis of the input signals to drive the support frame
75
.
Also, when the correction optical device is not operated, it is necessary to lock the support frame
75
. Three projections (not shown) are disposed on a back surface of the support frame
75
. The leading edges of those projections are inserted into the inner peripheral surface o
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Perkey W. B.
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