Photography – Camera shake sensing – Having stabilization system
Reexamination Certificate
1999-09-10
2001-08-07
Perkey, W. B. (Department: 2851)
Photography
Camera shake sensing
Having stabilization system
C396S061000, C396S063000, C396S067000, C396S165000, C396S169000
Reexamination Certificate
active
06272289
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera which uses an image blur prevention apparatus such as an image blur correction apparatus.
2. Related Background Art
Cameras are currently automated in all important photographing operations such an exposure determining operation and a focusing operation, thereby allowing even unskilled persons to make photographing errors at remarkably low possibilities.
In the recent years where researches have been made for systems which prevent hand vibrations from being applied to cameras, there remains few causes to induce photographers to erroneous photographing.
Brief description will be made of the system which prevents the hand vibration from being applied to a camera.
The hand vibration which is caused at a photographing time usually has a frequency of 1 Hz to 10 Hz, and a basic concept for enabling to obtain a photograph free from image blur regardless of the hand vibration lies in detecting a camera vibration caused by the hand vibration and displacing a correction lens in accordance with a detected value of the camera vibration. In order to obtain the photograph free from the image blur regardless of the hand vibration, it is therefore necessary first to accurately detect the camera vibration and secondly to correct a variation of an optical axis caused by the hand vibration.
The vibration (camera vibration) can be detected in principle with a camera equipped with a vibration detection apparatus comprising a vibration sensor which detects an acceleration, an angular acceleration, an angular velocity and an angular displacement, and a calculation device which adequately calculates outputs of the vibration sensor in order to correct the camera vibration. The image blur is suppressed by driving correction means which makes a photographing optical axis eccentric on the basis of detection data.
FIG. 28
is a perspective view showing an appearance of a compact camera having a vibration prevention system which has functions to correct a vertical vibration indicated by an arrow
42
p
and a horizontal vibration indicated by an arrow
42
y
relative to an optical axis
41
.
A camera body
43
comprises a release button
43
a
, a mode dial (including a main switch)
43
b
, a retractable strobe
43
c
and a finder window
43
d.
An internal configuration of the camera shown in
FIG. 28
is illustrated in
FIG. 29
, wherein a reference numeral
44
denotes a camera body, a reference numeral
51
denotes correction means, a reference numeral
52
denotes a correction lens, a reference numeral
53
denotes a support frame which corrects the vibrations in directions indicated by the arrows
42
p
and
42
y
shown in
FIG. 28
by freely driving the correction lens
52
in directions indicated by arrows
58
p
and
58
y
in FIG.
29
and will be described later in detail. Reference numerals
45
p
and
45
y
denote vibration detection devices such as an accelerometer and an angular velocity sensor which detect vibrations around arrows
46
p
and
46
y
respectively.
Outputs from the vibration detection devices
45
p
and
45
y
are converted by calculation devices
47
p
and
47
y
described later into driving target values for the correction means
51
and input into a coil of the correction means
51
for correcting the vibrations. In addition, a reference numeral
54
denotes a base plate, reference numeral
56
p
and
56
y
denote permanent magnets, and reference numeral
510
p
and
510
y
denote coils.
FIG. 30
is a block diagram illustrating in detail a configuration of the above described calculation device
47
p
and
47
y
, which are similarly configurated, therefore explanation will be made by using only the calculation device
47
p.
The calculation device
47
p
comprises a DC cut filter
48
p
, a low pass filter
49
p
, and analog/digital converter circuit (hereinafter referred to as an A/D converter)
410
p
and a driving device
419
p
which are enclosed by a chain line, and a camera microcomputer
411
which is enclosed by a dashed line. The camera microcomputer
411
comprises a memory circuit
412
p
, a differential circuit
413
p
, a DC cut filter
414
p
, an integral circuit
415
p
, a memory circuit
416
p
, a differential circuit
417
p
and a PWM duty changing circuit
418
p.
A vibrating gyroscope which detects a vibration angular velocity of the camera is used as the vibration detection device
45
p
, and the vibrating gyroscope is driven when a camera main switch is turned on and starts detecting the vibration angular velocity applied to the camera.
The DC cut off filter
48
p
configured by an analog circuit cuts off DC bias components which are overlapped with an output signal from the vibration detection device
45
p
. The DC cut filter
48
p
is configured by having a characteristic to cut off signal components having frequencies not higher than 0.1 Hz so that these components do not influence on the hand vibration having the frequencies from 1 to 10 Hz applied to the camera. However, the characteristic which cuts off the signal components having frequencies not higher than 0.1 Hz poses a problem that it requires about 10 seconds to cut off the DC components completely after a vibration signal is inputted from the vibration detection device
45
p
. Accordingly, a time constant of the DC cut filter
48
p
is shortened (to obtain a characteristic to cut off signal components having frequencies, for example, not higher than 10 Hz) for 0.1 second, for example, after the camera main switch is turned on so that the DC components are cut off in a short time of about 0.1 second and then the time constant is prolonged (to obtain a characteristic to cut off signal components having frequencies not higher than 0.1 Hz) so that a vibration angular velocity signal is not degraded by the DC cut filter
48
p.
The low pass filter
49
p
which is configured by an analog circuit amplifies an output signal from the DC cut filter
48
p
adequately in accordance with resolution of the A/D converter circuit
410
p
and cuts off high-frequency noise overlapped with the vibration angle velocity signal from the output signal from the DC cut filter
48
p
. The noise is cut off from the vibration angular velocity signal so that it will not cause the A/D converter circuit
410
p
to erroneously sample or read at a step to input the vibration angular velocity signal into the camera microcomputer
411
. Furthermore, an output signal from the low pass filter
49
p
is sampled by the A/D converter circuit
410
p
and input into the camera microcomputer
411
.
Though the DC bias components have been cut off by the DC cut filter
48
p
, subsequent amplification with the low pass filter
49
p
allows DC bias components to be overlapped with the vibration angular velocity signal and the DC components must be cut off once again in the camera microcomputer
411
.
The memory circuit
412
p
stores a vibration angular velocity signal which is sampled after 0.2 second, for example, elapses from turning on the camera main switch, and the differential circuit
413
p
calculates a difference between a stored value and the vibration angular velocity signal so that the DC components are cut off. The DC components can be cut off only roughly by these operations (since not only the DC components but also actual hand vibrations are contained in the vibration angular velocity signal stored after 0.2 second elapses from turning on the camera main switch) and the DC components are cut off sufficiently at a later step with the DC cut filter
414
p
which is configured by a digital filter. A time constant of this DC cut filter
414
p
can also be changed in like manner of the analog DC cut filter
48
p
and gradually prolonged for 0.2 second as measured after 0.2 second elapses from the camera main switch is turned on. Speaking concretely, the DC cut filter
414
p
has a characteristic as to cut off DC signal components having frequencies not higher than 10 Hz after 0.2 second elapses from turning on the main switch, and the
Canon Kabushiki Kaisha
Fitzpatrick, Cella, Harper and Scinto
Perkey W. B.
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