Photography – Attitude sensing
Reexamination Certificate
1999-08-30
2001-07-17
Perkey, W. B. (Department: 2851)
Photography
Attitude sensing
C396S052000
Reexamination Certificate
active
06263161
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image blur prevention apparatus which prevents image blur caused by hand fluctuation or the like in a camera, an optical apparatus, and the like.
2. Description of the Related Art
In current cameras, since exposure determining, focusing, and other operations important for photographing are all automated, even for persons unskilled in camera operation, a possibility of making a photographing failure is remarkably decreasing.
Moreover, in recent years, a system for preventing a hand fluctuation applied to a camera has been researched, and there are almost no factors for inducing photographers' photographing mistakes.
Here, the system for preventing the hand fluctuation will briefly be described.
The hand fluctuation of the camera during photographing is a vibration whose frequency is usually in the range of 1 Hz to 10 Hz. To allow photographs to be taken without any image blur even if such hand fluctuation is caused at the time of shutter release, as a fundamental concept, camera vibration by the hand fluctuation is detected, and a correction lens has to be displaced in accordance with a detected value. Therefore, to take photographs without causing any image blur even if camera fluctuation occurs, first, the camera vibration is exactly detected, and secondly, an optical axis change by the hand fluctuation needs to be corrected.
In principle, the detection of the vibration (camera fluctuation) can be performed by mounting onto the camera a blur detection device which is provided with a blur detection sensor for detecting acceleration, angular acceleration, angular speed, angular displacement, and the like and a calculation portion for appropriately calculating/processing an output of the sensor to correct the camera fluctuation. Then, based on detected information, correction means for decentering a photographing optical axis is driven to perform image blur suppression.
FIG. 31
is an appearance perspective view of a compact camera which has a blur prevention system, and the system has a function of performing blur correction for vertical and transverse camera fluctuations shown by arrows
42
p
and
42
y
relative to an optical axis
41
.
Additionally, a camera main body
43
has a release button
43
a
, a mode dial
43
b
(including a main switch), a retractable strobe
43
c
, and a finder window
43
d.
FIG. 32
is a perspective view showing an inner constitution of the camera shown in FIG.
31
. The constitution is provided with a camera main body
44
, correction means
51
, a correction lens
52
, and a support frame
53
for freely driving the correction lens
52
in directions shown by arrows
58
p
and
58
y
to correct the blurs of the directions shown by the arrows
42
p
and
42
y
of
FIG. 31
, and details will be described later. Blur detection devices
45
p
,
45
y
have an angular velocity sensor accelerometer or the like for detecting blur around axes as shown by arrows
46
p
and
46
y
, respectively, and the like.
Outputs of the blur detection devices
45
p
and
45
y
are converted via calculation devices
47
p
and
47
y
described later to driving target values of the correction means
51
, which are transmitted to coils of the correction means
51
to perform the blur correction. Additionally, numeral
54
denotes a base plate,
56
p
and
56
y
denote permanent magnets, and
510
p
and
510
y
denote coils.
FIG. 33
is a block diagram showing details of the calculation devices
47
p
and
47
y
. Since the devices have similar constitutions, in the drawing only the calculation device
47
p
is used for description.
The calculation device
47
p
is provided with, as surrounded by a dot-dashed line, a DC cut filter
48
p
, a low-pass filter
49
p
, an analog/digital converting circuit (hereinafter referred to as A/D converting circuit)
410
p
, and a driving apparatus
419
p
, and as shown by a broken line, a camera microcomputer
411
. Moreover, the camera microcomputer
411
is constituted of 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 converting circuit
418
p.
Here, the blur detection device
45
p
used is a blur gyro which detects a camera fluctuation angular speed. The blur gyro is driven synchronously when the camera main switch is turned on, and starts detecting the blur angular speed applied to the camera.
For an output signal of the blur detection device
45
p
, a DC bias component superimposed to the output signal is cut by the DC cut filter
48
p
constituted of an analog circuit. The DC cut filter
48
p
has a frequency property of cutting signals whose frequencies are 0.1 Hz or less, so that a hand fluctuation frequency range applied to the camera of 1 to 10 Hz is not influenced. However, with the property of cutting 0.1 Hz or less, there is a problem that it takes almost ten seconds from when a blur signal is transmitted from the blur detection device
45
p
until DC is completely cut. To solve the problem, by setting a time constant of the DC cut filter
48
p
to be small within, for example, 0.1 second from when the camera main switch is turned on (providing a property of cutting a signal with a frequency of, for example, 10 Hz or less), DC is cut for a short time of about 0.1 second. Thereafter, by setting the time constant to be large (providing a property of cutting only a frequency of 0.1 Hz or less), deterioration of a blur angular speed signal is prevented by the DC cut filter
48
p.
An output signal of the DC cut filter
48
p
is appropriately amplified by the low-pass filter
49
p
constituted of the analog circuit in accordance with a resolution of A/D converting circuit
410
p
, while a high-frequency noise superimposed to the blur angular speed signal is cut. This prevents a reading error from being caused by noise of the blur angular speed signal during sampling of the A/D converting circuit
410
p
when the blur angular speed signal is transmitted to the camera microcomputer
411
. Moreover, an output signal of the low-pass filter
49
p
is sampled by the A/D converting circuit
410
p
and transmitted into the camera microcomputer
411
.
The DC bias component is cut by the DC cut filter
48
p
, but by the subsequent amplification of the low-pass filter
49
p
the DC bias component is again superimposed to the blur angular speed signal. Therefore, in the camera microcomputer
411
DC cutting needs to be performed again.
In this case, for example, the blur angular speed signal sampled 0.2 second after the camera switch is turned on is stored in the memory circuit
412
p
, and a difference between the stored value and the blur angular speed signal is obtained by the differential circuit
413
p
to perform DC cutting. Additionally, since in the operation the DC cutting can only be roughly performed (because the blur angular speed signal, stored 0.2 second after the camera main switch is turned on, includes not only DC component but also actual hand fluctuation), in a later stage a sufficient DC cutting is performed by the DC cut filter
414
p
constituted of a digital filter. A time constant of the DC cut filter
414
p
can also be changed in the same manner as the analog DC cut filter
48
p
. For further 0.2 second after 0.2 second time periods elapsed after turning on of the camera main switch, the time constant is gradually increased. Specifically, when 0.2 second elapses from the turning-on of the main switch, the DC cut filter
414
p
has the filter property of cutting the frequency of 10 Hz or less. Thereafter, every time 50 msec elapse, the frequency to be cut by the filter is lowered to 5 Hz, 1 Hz, 0.5 Hz, and 0.2 Hz.
However, during the above-described operation, if the photographer depresses the release button
43
a
half way (turns on sw
1
) to perform photometry, or distance measurement, photographing may immediately be performed. In this case, it is unfavorable to consume time to chang
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Perkey W. B.
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