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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera having a blurring movement
correction mechanism, more precisely, it relates to a camera which is
equipped with a correction mechanism that detects unintentional movement
of hands holding the camera and that cancels the movement of the image
formed on the film surface corresponding to the unintentional motion of
hands in response to the detection results of the motion of the camera by
driving an optical correction unit which is disposed on an optical path of
a fixed focal length optical system or a variable focal length optical
system of the camera.
2. Description of the Related Art
In general, a camera having an unintentional blurring movement correction
or cancelling mechanism (which is called simply camera hereinafter) is
constructed in such a way that, in an example where the camera is provided
with a zoom lens as a photo-taking optical system, the photo-taking
optical system is detachably arranged in the camera as an integral unit of
the camera body or through a lens mount and that a film surface is
disposed behind the lens system on an optical axis of the lens system.
The photo-taking optical system comprises a focusing lens group constituted
from a plurality of lenses and a zooming lens group constituted from a
plurality of lenses. A blurring correction optical element is disposed on
an optical path of the lens groups.
The focusing lens group is driven to become an in-focus state by a focus
command signal Df. The zoom lens group is driven to achieve a zooming
function by a zoom command signal Dz. Also, the blurring correction lens
element is driven to correct or compensate for the blur of photo-image
caused by unintentional motion of hands by a blur correction command
signal Da.
Next, the functional motion of each lens group is described below. The
focusing lens group is driven to move forward according as the focal
length is shifted to the telescopic side and according as the length to
the subject to be taken is shortened.
The zoom lens group is driven to move forward according as the focal length
is shifted toward the telescopic side. Similarly, the blur correction
optical element is driven to move forward according as the zoom lens group
is driven to move toward the telescopic side.
Next, the blur correction command signal Da is more concretely described
below.
The example is the case where the oscillation motion of the camera body
caused by unintentional movement of hands has an oscillation
characteristic of approximately sine wave form curve (a) representing an
amplitude curve that moves to the positive and negative directions from
the boundary of zero level.
To correct blur of photograph, that is, to minimize or compensate for
influence to the subject image on the film caused by unintentional
movement of hands holding the camera body that blurs the photograph, the
blur correction mechanism of the camera is arranged as follows.
First, a hand movement detection unit arranged within the camera body
detects the velocity V of the hand movement within a very short period of
time. Then, a movement velocity changing amount data Bk is calculated on
the basis of the detected velocity data. The blur (hand movement)
correction command signal Da is obtained from the velocity changing amount
data Bk. The signal Da is used to drive the blur correction optical
element to move in the direction in which the motion of the camera caused
by the hand movement is canceled so as to prevent the image of the subject
on the film surface from moving on the film surface.
The correction motion is always delayed from the actual unintentional
motion of the camera.
More precisely, the movement velocity is detected at a plurality of times
(t-2It), (t-It), (t), (t+It) . . . , wherein (It) represents the
integration time period for each time to detect the velocity. The velocity
changing amount data B.sub.k, B.sub.k-1, . . . is calculated on the basis
of each velocity detection data. Then, on the basis of each velocity
changing amount data B.sub.k, B.sub.k-1, . . . is calculated a camera
motion velocity data V.sub.k, V.sub.k-1, . . . which is used to generate
the blur correction command signal Da.
Therefore, the image formed on the film surface moves in accordance with a
corrected characteristic (f) which is compensated with the use of
correction characteristic (d) with respect to the movement amount
characteristic (e).
However, in accordance with the above mentioned correction arrangement,
only about one fourth of the total movement amount of the camera body can
be corrected.
In order to improve this point of correction amount ratio, an arrangement
is proposed wherein the input amount to the drive circuit for the blur
correction optical element is controlled so as to converge the oscillation
of the movement of the camera body at the time of driving the optical
system for correcting the movement of the camera.
Such an arrangement is disclosed in Japanese Patent Application Laying Open
(KOKAI) No.1-300221, for instance. In accordance with the arrangement
disclosed in the patent document, the amplifying ratio of the drive
circuit for the blur correcting optical element is varied in response to
the output from the movement detection unit so that the oscillation
movement of the camera body caused by the unintentional movement of hands
is attenuated to converge.
Also, the above mentioned patent document discloses another arrangement for
attenuating the movement of the camera body with the use of the above
mentioned electric means for varying the amplifying ratio of the drive
circuit wherein the rigidity of the oscillation detecting sensor for
detecting the movement of hands holding the camera body is varied to
attenuate the oscillation so as to increase the correction amount ratio of
the unintentional oscillation.
On the other hand, the actual amount of the driving amount for correcting
the movement of the camera varies in accordance with the length to the
subject. This point is described more precisely below.
A photo-taking optical system R is constituted from a film 2 disposed at a
rear portion in the camera body P and a principal point Q positioned at a
front portion in the camera body. When the camera body P moves upward from
the optical axis O by the length y1, an image of a subject point A1 on the
optical axis O is formed at an intersection point A3 between the film 2
and a line passing through the point A1 and a point B2 which is a point at
a length y1 upward from a point B1 which is an intersection point between
the optical axis O and the vertical line of the principal point Q.
On the other hand, in the initial position of the camera (the position of
the camera before the camera is moved), the image forming point for the
subject point A1 is at a point A2 on the film which point A2 is an
intersecting point of the optical axis to the film. The point A2
corresponds to a point A4 on the film after the camera is moved which
point A4 is length y1 upward from the point A2. Therefore, by moving the
camera body upward by the length y1, the point A4 is moved to the point A3
on the film.
Accordingly, it becomes possible to prevent the image forming point on the
film from being shifted from the point A4 to A3 when the camera body is
moved upward by the length y1, by shifting the photo-taking optical system
on the principal point line Q from the point B1 to the point B3 which is
the intersection point of the line between the points A1 and A4 to the
vertical line Q.
Assuming that the length between the points B2 and B3 is represented by y2,
the length from the principal point Q to the film surface is represented
by x1 and that the length from the point A1 to the principal point Q is
represented by x2, the following equations are satisfied.
y1/(x1+x2)=(y1-y2)/x2
y2=(x1/(x1+x2)y2
There length y2 is influenced from the length x2 to the subject.
Accordingly, it becomes desirable to correct the blur correction command
signal Da with the use of the data of length from the camera to the
subject.
In accordance with the camera mentioned above, blur caused by unintentional
movement of hands is prevented in such a way that movement of camera due
to movement of hands is detected first, that on the basis of the detection
data is calculated a drive amount for driving the movement compensation
optical element and that in response to the calculation result is driven
the optical element.
However, in accordance with such an arrangement for correcting the blur due
to the hand motion, the following problems are involved.
First, the timing point of obtaining the calculation result is inevitably
retarded from the timing point of detecting the movement of the camera and
also the timing point of driving the optical system for correcting the
motion of the camera is inevitably retarded from the timing point of
obtaining the calculation result. Accordingly, there is always some
deficiency in correction amount due to the delay of each functional timing
point inevitably generated in the blur correction optical system so that
the movement of the camera is not satisfactorily corrected.
Such a problem may not be significant when the movement amount of hands is
relatively small, since the deficiency of correction amount is also small
in that case so that the practical correcting function of the optical
system according to the related art mentioned above is not critically
impaired. However, such a problem becomes significant when the movement
amount of hands becomes large since the deficiency of correction amount
becomes large as well.
Secondly, there has been no consideration to the point that the necessary
movement correction amount changes according to the focal length of the
photo-taking optical system, that is, the shift amount of the image
position on the film surface becomes large according as the focal length
becomes large even when the movement amount of the camera body itself is
the same. Therefore, the unintentional movement of the camera is not
satisfactorily controlled and can not be fully cancelled according to the
related art mentioned above.
For example, in the case where focal length of the photo-taking optical
system changes from about a wide angle of 35 mm to a telescope of 70 mm
and where the blur correction system is driven on the basis of the most
telescopic side in which the correction condition is most severe, when the
focal length of the photo-taking optical system is arranged on the wide
angle side, then the correcting function of the system becomes much more
than being necessitated so that an accurate and appropriate function for
correcting the unintentional motion of the camera is not achieved by the
blur correction system mentioned above.
Besides, there has been no consideration to the point, either, that the
necessary movement correction amount changes according to the length to
the subject, that is, the shift amount of the image position on the film
surface becomes large according as the length to the subject becomes small
(subject comes close to the camera), even when the movement amount of the
camera body itself is the same. Therefore, the unintentional movement of
the camera is not satisfactorily controlled and can not be fully cancelled
according to the related art mentioned above.
More precisely, in accordance with the camera of the related art mentioned
above, the blur correcting optical element is driven on the basis of the
movement correcting amount data which is obtained using the most
frequently arranged or most common or usual length of the subject as the
reference of the calculation of the correcting amount data, which impairs
the accurate and reliable movement correcting operation in the wide range
of subject length from a close distance to an infinite point.
SUMMARY OF THE INVENTION
The present invention was made considering the above mentioned points. It
is therefore a primary object of the present invention to provide a camera
which is able to obviate blurring of the photograph by reliably and
appropriately correcting unintentional movement of hands irrespective of
the magnitude of the movement not only in the case where the movement
amount is small but the movement amount is very large as well.
Also, it is a second object of the present invention to provide a camera
which is able to obviate blurring of the photograph by reliably and
appropriately correcting unintentional movement of hands irrespective of
the magnitude of the movement not only in the case where the movement
amount is small but the movement amount is very large as well and also
irrespective of the focal length set in the arrangement of the variable
focal length photo-taking optical system.
A third object of the present invention is to provide a camera which is
able to obviate blurring of the photograph by reliably and appropriately
correcting unintentional movement of hands irrespective of the magnitude
of the movement not only in the case there the movement amount is small
but the movement amount is very large as well and also irrespective of the
length to the subject.
The above mentioned objects of the present invention can be achieved by
a camera having blurring movement correction mechanism comprising:
a blurring movement correction optical element disposed in an optical path
of a photo-taking optical system so as to correct shift of an image formed
on a film surface caused by movement of hands holding a camera body;
a blurring movement correction actuator for moving the optical element in a
necessary direction for correcting the shift of the image on the film
surface;
a blurring movement detection unit for obtaining a blurring movement
detection data by converting the blurring movement of the camera body to
an electric signal;
a first memory unit for temporarily registering the detection data output
from the detection unit;
a calculation unit for calculating blurring movement correction data for
correcting the shift of the image formed on the film surface caused by
movement of hands holding the camera body by actuating the optical element
by the actuator; and
a second memory unit for temporarily registering an output data of
calculation from the calculation unit,
the calculation unit being so constructed that the blurring movement
correction data is predictively calculated on the basis of the detection
data of this time obtained from the detection unit, the detection data of
the preceding time registered in the first memory unit and the correction
data of the preceding time registered in the second memory unit so as to
correct said shift of the image formed on the film surface by actuating
said optical element by said actuator.
In accordance with the above mentioned structure of the camera according to
the present invention, a movement correcting actuator is driven to move or
incline the movement correcting optical element in the directed direction
which element is disposed in an optical path of the photo-taking optical
system for correcting the shift motion of the image on the film surface
caused by unintentional movement of hands holding the camera body. The
actuator is driven in such a way that the movement of the camera body is
detected by a movement detection unit which outputs an electric detection
signal of movement detection data which is then temporarily registered in
a first memory means, that movement correction amount data is calculated
by a calculation means on the basis of the movement detection data
registered in the first memory means and that the calculation data output
from the calculation means is registered in a second memory means.
In that function of the present invention structure mentioned above, on
either the basis of the movement detection data detected by the movement
detection unit, the movement detection data registered in the first memory
means and the movement correction amount data registered in the second
memory means or on the basis of the subject distance data measured by a
distance measuring means, the calculation means predictively calculates
the movement correction amount data of first or second degree of
approximation for predicting the correcting amount of the image position
on the film surface which is to be corrected by driving the optical
element. Also, in the case where the photo-taking optical system comprises
a variable focal length system, the calculation means predictively
calculates the image shifting motion on the film surface by adding
correction in response to the focal length to the correction amount data.
The unintentional movement of camera body is corrected on the basis of the
predictively calculated data output from the calculation means.
The necessary data for predicting the image motion may be obtained either
from two operations of the camera, that is, this time operation and the
preceding operation or from three operations, that is, this time
operation, the preceding operation and the preceding operation before the
preceding operation.
Further, the movement detection unit detects, for example, acceleration
generated in the camera body which is then integrated in the predetermined
integration period to generate the movement correction amount data.
In accordance with the present invention, at the time when the movement
correction optical element disposed on the optical path of the
photo-taking optical system is to be driven to move in the direction
cancelling the influence from the unintentional movement of hands holding
the camera body, a movement correction amount data for correcting the
unintentional movement at the time of driving the optical element is
predictively calculated on the basis of velocity data of camera motion and
movement changing amount data obtained at a plurality of timings at
predetermined regular intervals. And the calculated data is used for
correcting the unintentional movement of the camera body.
Therefore, it is an advantage of the present invention that it becomes
possible to effectively correct and cancel the unintentional movement of
hands irrespective of the degree of the movement of user's hands and even
when the camera is unintentionally moved continuously.
It is another advantage of the present invention that the unintentional
movement of hands can be accurately corrected in the whole range of
variable focal length by the arrangement wherein the focal length of the
photo-taking optical system now on being operated is detected so that the
correction amount data is corrected on the basis of the zoom position data
obtained in the operation at this time.
Further, it is still another advantage of the present invention that it
becomes possible to accurately correct the unintentional movement of hands
in the whole range of subject distance from a close position to an
infinite point since the movement correction amount data is corrected on
the basis of the subject distance data obtained by detecting the length to
the subject.
As mentioned above, in accordance with the present invention, it becomes
possible to provide a camera which enables to take a high quality
photograph without blurring of the photo.
Further objects and advantages of the present invention will be apparent
from the following description of the preferred embodiments of the
invention as illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an explanatory view for explaining the construction of the camera
having a blur correction mechanism according to the related art;
FIG. 2 is an explanatory view for graphically explaining the function of
the blur correction mechanism of FIG. 1;
FIG. 3 is a graphical view of wave-forms representing the movement
correcting function of the camera according to the related art;
FIG. 4 is a partial enlarged view of the graph of FIG. 3;
FIG. 5 is a graphical view of wave-forms representing changing amount of
movement of hands in relation to time after the correctional function of
the camera according to the related art;
FIG. 6 is an explanatory view for explaining the shift of the image of the
subject at any distance formed on the film in relation to the movement of
the camera;
FIG. 7 is a block diagram of the electrical circuit of the camera in
accordance with a first embodiment of the present invention;
FIG. 8 is an explanatory view for explaining the function of the AF circuit
included in the circuit of the first embodiment of FIG. 7;
FIG. 9 is a flow chart representing the function of the first embodiment of
FIG. 1;
FIG. 10 is a flow chart of the function of the first embodiment continued
from the flow chart of FIG. 9;
FIG. 11 is a graphical view for explaining the sampling function of the
first embodiment of FIG. 7;
FIG. 12 is a graphical view for explaining the state of movement correcting
operation according to the first embodiment of FIG. 7;
FIG. 13 is a partial enlarged view of the graph of FIG. 12;
FIG. 14 is an explanatory view representing the movement amount of camera
after the movement of hands is corrected according to the first embodiment
of FIG. 7;
FIG. 15 is a block diagram of the electric circuit structure in accordance
with a second embodiment of the present invention;
FIG. 16 is a flow chart of the function of the second embodiment of the
present invention;
FIG. 17 is a flow chart of the second embodiment of the present invention
continued from the flow chart of FIG. 16; and
FIG. 18 is an explanatory view for explaining the state of operating the
movement correcting means according to the second embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention are described hereinafter in detail
with reference to the drawings and in comparison to the related art which
is also described referring to the drawings.
In general, a camera having a blur correction mechanism (which is called
simply camera hereinafter) is constructed in such a way that, in an
example where the camera is provided with a zoom lens as a photo-taking
optical system, as illustrated in FIGS. 1 and 2, the photo-taking optical
system 1 is detachably arranged in the camera as an integral unit of the
camera body or through a lens mount and that a film surface 2 is disposed
behind the lens system 1 on an optical axis (O) of the lens system 1.
The photo-taking optical system 1 comprises a focusing lens group 3
constituted from a plurality of lenses and a zooming lens group 4
constituted from a plurality of lenses. A blurring correction optical
element 5 is disposed on an optical path of the lens groups.
The focusing lens group 3 is driven to become an in-focus state by a focus
command signal Df. The zoom lens group 4 is driven to achieve a zooming
function by a zoom command signal Dz. Also, the blurring correction lens
element 5 is driven to correct or compensate for the blur of photo-image
caused by unintentional motion of hands by a blur correction command
signal Da.
Next, the functional motion of each lens group 3, 4, 5 is described below.
The focusing lens group 3, in this particular example, is driven to move
forward according as the focal length is shifted to the telescopic side
and according as the length to the subject to be taken is shortened.
The zoom lens group 4 is driven to move forward according as the focal
length is shifted toward the telescopic side. Similarly, the blur
correction optical element 5 is driven to move forward according as the
zoom lens group 4 is driven to move toward the telescopic side.
Next, the blurring movement correction command signal Da is more concretely
described below.
The example is the case where the oscillation motion of the camera body
caused by unintentional movement of hands has an oscillation
characteristic of approximately sine wave form curve (a), as illustrated
in FIG. 3, representing an amplitude curve that moves to the positive and
negative directions from the boundary of zero level.
To correct blur of photograph, that is, to minimize or compensate for
influence to the subject image formed on the film caused by unintentional
movement of hands holding the camera body that blurs the photograph, the
blurring movement correction mechanism of the camera is arranged as
follows.
First, a hand movement detection unit arranged within the camera body
detects the velocity V of the hand movement within a very short period of
time. Then, a movement velocity changing amount data Bk is calculated on
the basis of the detected velocity data. The blur (hand movement)
correction command signal Da is obtained from the velocity changing amount
data B.sub.k. The signal Da is used to drive the blur correction optical
element to move in the direction in which the motion of the camera caused
by the hand movement is canceled so as to prevent the image of the subject
on the film surface 2 from moving on the film surface.
However, the correction motion is always delayed from the actual
unintentional motion of the camera, as illustrated by curve (b) in FIG. 3.
More precisely, as illustrated by enlarged graphs in FIG. 4, the movement
velocity is detected at a plurality of times (t-2It), (t-It), (t), (t+It)
. . . , wherein (It) represents the integration time period for each time
to detect the velocity. The velocity changing amount data B.sub.k,
B.sub.k-1, . . . is calculated on the basis of each velocity detection
data. Then, on the basis of each velocity changing amount data B.sub.k,
B.sub.k-1, . . . is calculated a camera motion velocity data V.sub.k,
V.sub.k-1, . . . which is used to generate the blurring movement
correction command signal Da.
Therefore, the image formed on the film surface 2 moves in accordance with
a corrected characteristic (f) which is compensated with the use of
correction characteristic (d) with respect to the movement amount
characteristic (e), as represented in FIG. 5.
However, in accordance with the above mentioned correction arrangement,
only about one fourth of the total movement amount of the camera body can
be corrected.
In order to improve this point of correction amount ratio, an arrangement
is proposed wherein the input amount to the drive circuit for the blur
correction optical element is controlled so as to converge the oscillation
of the movement of the camera body at the time of driving the optical
system for correcting the movement of the camera.
Such an arrangement is disclosed in Japanese Patent Application Laying Open
(KOKAI) No.1-300221, for instance. In accordance with the arrangement
disclosed in the patent document, the amplifying ratio of the drive
circuit for the blur correcting optical element is varied in response to
the output from the movement detection unit so that the oscillation
movement of the camera body caused by the unintentional movement of hands
is attenuated to converge.
Also, the above mentioned patent document discloses another arrangement for
attenuating the movement of the camera body with the use of the above
mentioned electric means for varying the amplifying ratio of the drive
circuit wherein the rigidity of the oscillation detecting sensor for
detecting the movement of hands holding the camera body is varied to
attenuate the oscillation so as to increase the correction amount ratio of
the unintentional oscillation.
On the other hand, the actual amount of the driving amount for correcting
the movement of the camera varies in accordance with the length to the
subject. This point is described more precisely below referring to FIG. 6.
A photo-taking optical system R is constituted from a film 2 disposed at a
rear portion in the camera body P and a principal point Q positioned at a
front portion in the camera body. When the camera body P moves upward from
the optical axis O by the length y1, an image of a subject point A1 on the
optical axis O is formed at an intersection point A3 between the film 2
and a line passing through the point A1 and a point B2 which is a point at
a length y1 upward from a point B1 which is an intersection point between
the optical axis O and the vertical line of the principal point Q.
On the other hand, in the initial position of the camera (the position of
the camera before the camera is moved), the image forming point for the
subject point A1 is at a point A2 on the film 2 which point A2 is an
intersecting point of the optical axis to the film 2. The point A2
corresponds to a point A4 on the film 2 after the camera is moved which
point A4 is length y1 upward from the point A2. Therefore, by moving the
camera body upward by the length y1, the point A4 is moved to the point A3
on the film.
Accordingly, it becomes possible to prevent the image forming point on the
film from being shifted from the point A4 to A3 when the camera body is
moved upward by the length y1, by shifting the photo-taking optical system
on the principal point line Q from the point B1 to the point B3 which is
the intersection point of the line between the points A1 and A4 to the
vertical line Q.
Assuming that the length between the points B2 and B3 is represented by y2,
the length from the principal point Q to the film surface is represented
by x1 and that the length from the point A1 to the principal point Q is
represented by x2, the following equations are satisfied.
y1/(x1+x2)=(y1-y2)/x2
y2=(x1/(x1+x2))y1
Therefore, the length y2 is influenced from the length x2 to the subject.
Accordingly, it becomes desirable to correct the blurring movement
correction command signal Da which is mentioned above with reference to
FIG. 6 with the use of the data of length from the camera to the subject.
In accordance with the camera mentioned above, blur caused by unintentional
movement of hands is prevented in such a way that movement of camera due
to movement of hands is detected first, that on the basis of the detection
data is calculated a drive amount for driving the movement compensation
optical element and that in response to the calculation result is driven
the optical element.
However, in accordance with such an arrangement for correcting the blur due
to the hand motion, the following problems are involved.
First, as illustrated in FIG. 3 represented by letter (c), the timing point
of obtaining the calculation result is inevitably retarded from the timing
point of detecting the movement of the camera and also the timing point of
driving the optical system for correcting the motion of the camera is
inevitably retarded from the timing point of obtaining the calculation
result. Accordingly, there is always some deficiency in correction amount
due to the delay of each functional timing point inevitably generated in
the blur correction optical system so that the movement of the camera is
not satisfactorily corrected.
Such a problem may not be significant when the movement amount of hands is
relatively small, since the deficiency of correction amount is also small
in that case so that the practical correcting function of the optical
system according to the related art mentioned above is not critically
impaired. However, such a problem becomes significant when the movement
amount of hands becomes large since the deficiency of correction amount
becomes large as well.
Secondly, there has been no consideration to the point that the necessary
movement correction amount changes according to the focal length of the
photo-taking optical system, that is, the shift amount of the image
position on the film surface becomes large according as the focal length
becomes large even when the movement amount of the camera body itself is
the same. Therefore, the unintentional movement of the camera is not
satisfactorily controlled and can not be fully cancelled according to the
related art mentioned above.
For example, in the case where focal length of the photo-taking optical
system changes from about a wide angle of 35 mm to a telescope of 70 mm
and where the blur correction system is driven on the basis of the most
telescopic side in which the correction condition is most severe, when the
focal length of the photo-taking optical system is arranged on the wide
angle side, then the correcting function of the system becomes much more
than being necessitated so that an accurate and appropriate function for
correcting the unintentional motion of the camera is not achieved by the
blur correction system mentioned above.
Besides, there has been no consideration to the point, either, that the
necessary movement correction amount changes according to the length to
the subject, that is, the shift amount of the image position on the film
surface becomes large according as the length to the subject becomes small
(subject comes close to the camera), even when the movement amount of the
camera body itself is the same. Therefore, the unintentional movement of
the camera is not satisfactorily controlled and can not be fully cancelled
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