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United States Patent |
5,781,805
|
Shiomi
|
July 14, 1998
|
Image blur prevention apparatus
Abstract
An image blur prevention apparatus includes a movable member (e.g., a
correction optical system) which moves for image blur prevention, a
holding device (e.g., a locking member for holding the correction optical
system) which holds the movable member, the holding device being
changeable between a state in which a predetermined holding operation is
performed and a state in which the predetermined holding operation is not
performed, an operating device which operates the movable member for image
blur prevention (e.g., operates the correction optical system in
accordance with an image blur signal) at a predetermined position as a
control center position (e.g., a position at which the optical axis of the
correction optical system matches another optical axis), and a control
device which controls movement of the movable member between the position
at which it is held by the holding device and the predetermined position,
and which controls a process of the movement between the holding position
and the predetermined position.
Inventors:
|
Shiomi; Yasuhiko (c/o Canon Kabushiki Kaisha 30-2, Shimomaruko 3-chome, Ohta-ku, Tokyo, JP)
|
Appl. No.:
|
698147 |
Filed:
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August 15, 1996 |
Foreign Application Priority Data
Intern'l Class: |
G03B 005/00 |
Field of Search: |
396/55,53,52
348/208
359/554-559
|
References Cited
U.S. Patent Documents
4965619 | Oct., 1990 | Shikaumi et al. | 396/55.
|
5335032 | Aug., 1994 | Onuki et al. | 396/53.
|
Primary Examiner: Perkey; W. B.
Claims
What is claimed is:
1. An image blur prevention apparatus comprising:
a movable member which moves for image blur prevention;
a holding device which holds said movable members, said holding device
being changeable between a state in which a predetermined holding
operation is performed and a state in which the predetermined holding
operation is not performed;
an operating device which operates said movable member for image blur
prevention at a predetermined position as a control center position; and
a control device which controls movement of said movable member between a
holding position of said holding device and the predetermined position,
said control device controlling a process of the movement between the
holding position and the predetermined position.
2. An image blur prevention apparatus according to claim 1, wherein said
control device includes means for controlling a position of said movable
member during a process by which said movable member is moved between the
holding position and the predetermined position.
3. An image blur prevention apparatus according to claim 1, wherein said
control device includes means for controlling, step by step, the movement
of said movable member when said movable member is to be moved between the
holding position and the predetermined position.
4. An image blur prevention apparatus according to claim 1, wherein said
operation device includes means for operating said movable member in
accordance with an image blur state.
5. An image blur prevention apparatus according to claim 4, wherein said
operation device includes means for operating said movable member in
accordance with a signal that corresponds to the image blur state.
6. An image blur prevention apparatus according to claim 4, wherein said
operation device includes means for operating said movable member in
accordance with the image blur state so that said movable member is
positioned at the predetermined position when image blur does not occur.
7. An image blur prevention apparatus according to claim 1, wherein said
holding device includes means for holding said movable member by a
mechanical operation.
8. An image blur prevention apparatus according to claim 1, wherein said
operation device includes means for operating said movable member by using
a movable range center position of said movable member as the control
center position.
9. An image blur prevention apparatus according to claim 1, wherein said
movable member includes an optical member.
10. An image blur prevention apparatus according to claim 9, wherein said
operation device includes means for operating said movable member by
employing a position at which an optical axis of said optical member
substantially corresponds to an optical axis of another optical system as
the control center position.
11. An image blur prevention apparatus according to claim 1, wherein said
control device includes means for moving said movable member from the
holding position to the predetermined position when said holding device
releases the holding.
12. An image blur prevention apparatus according to claim 1, wherein said
control device includes means for moving said movable member from the
predetermined position to the holding position when said holding device
starts the holding.
13. An apparatus adapted for an image blur prevention device that includes
a movable member which moves for image blur prevention, a holding device
which holds the movable member, the holding device being changeable
between a state in which a predetermined holding operation is performed
and a state in which the predetermined holding operation is not performed
and an operation device which operates the movable member for image blur
prevention at a predetermined position as a control center position, said
apparatus comprising:
a control device which controls movement of the movable member between a
holding position of the holding device and the predetermined position,
said control device controlling a process of the movement between the
holding position and the predetermined position.
14. An optical apparatus comprising:
a movable member which moves for image blur prevention;
a holding device which holds said movable member, said holding device being
changeable between a state in which a predetermined holding operation is
performed and a state in which the predetermined holding operation is not
performed;
an operating device which operates said movable member for image blur
prevention at a predetermined position as a control center position; and
a control device which controls movement of said movable member between a
holding position of said holding device and the predetermined position,
said control device controlling a process of the movement between the
holding position and the predetermined position.
15. A camera comprising:
a movable member which moves for image blur prevention;
a holding device which holds said movable member, said holding device being
changeable between a state in which a predetermined holding operation is
performed and a state in which the predetermined holding operation is not
performed;
an operating device which operates said movable member for image blur
prevention at a predetermined position as a control center position; and
a control device which controls movement of said movable member between a
holding position of said holding device and the predetermined position,
said control device controlling a process of the movement between the
holding position and the predetermined position.
16. An image blur prevention apparatus according to claim 1, wherein said
holding device includes means for regulating the movement of said movable
member so that said movable member is movable in a smaller range than the
movable range for the image blur prevention.
17. An image blur prevention apparatus according to claim 1, wherein said
holding device includes means for abutting a portion of said movable
member to hold the movable member.
18. An image blur prevention apparatus comprising:
a movable member which moves for image blur prevention;
a holding device which holds said movable member, said holding device being
changeable between a state in which a predetermined holding operation is
performed and a state in which the predetermined holding operation is not
performed;
an operating device which operates said movable member for image blur
prevention at a predetermined position as a control center position; and
a control device which controls movement of said movable member between a
holding position of said holding device and the predetermined position.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image blur prevention apparatus that
prevents the occurrence of blurred images when a camera or other optical
devices are used.
2. Related Background Art
The conventional structure of an image blur prevention apparatus that is
used for a camera, etc., is shown in FIG. 12. In accordance with the state
of a switch 52, through a lock driving means 61, a control circuit 51, for
controlling the entire apparatus, operates a lock mechanism 62 that
mechanically locks and, in order to begin an image blur prevention
operation, releases the lock of a correction system 59.
At the same time as this operation is being performed, the output,
transmitted through a high pass filter 55 and an integral means 56, of a
fluctuation sensor 54, which detects the movement of the hands of an
individual, such as a photographer, who operates an optical device; the
output of a correction system position detection means 60, which detects
the positional shifting of a correction system 59; and the output of a
driving center setting means 50, which sets a driving center by employing
data it receives from an adjusted data setting means 63, are added
together by an addition means 57 and the result is input to a correction
system driving means 58. Then, the output of the correction system driving
means 58 is employed to drive the correction system 59, which is provided
in one part, or in front, of an exposure system.
Therefore, under the previously described feedback control for the
correction system, as long as the phase of movement and the sensitivity of
the correction system are set (i.e., an output at a unit correction
angle), the positioning of the correction system, which is determined by
the output of the fluctuation sensor 54 and the output of the driving
center setting means 50, can be instantaneously adjusted, so that the
blurring of an image, which can accompany the movement of the hands of an
operator, can be expeditiously avoided.
In the prior art, however, the locking mechanism for the correction system
is so designed that for a projection that is formed on the locking
mechanism, which during the locking process rapidly engages a recessed
portion of the correction system, normally there is a certain amount of
play provided by sizing errors that occur during manufacture and because
of improvements made to increase the reliability of the locking operation.
Therefore, when the control of the correction system 59 is in the OFF
state and the correction system 59 is locked, the correction system 59 can
be freely shifted within a range of movement that is provided by the play.
FIG. 13 specifically shows the range of movement afforded by the play in
the mechanical locking when the correction system 59 is locked. As is
shown in FIG. 13, the range of movement for the correction system 59,
while it is in the locked state, defines a circle. In order for
mechanical/optical positioning to be performed, the correction system is
usually so designed that the center of the light axis is at the center of
the play in the mechanical locking. A driving center, with which
correction is to be performed based on the above-described sensor output,
is also intended to correspond with the center of the play in the
mechanical locking.
However, the position of the driving center of the correction system 59
differs, depending on the lenses employed, in accordance with the accuracy
of the attachment of the correction system position detection means 60 and
the offset for circuitry. The data for the individual lenses that are set
by the adjusting data setting means 63 are used to provide corrections for
correctly positioning the driving center so that its position corresponds
with the center of the range of play for the mechanical locking. As was
first described, when there is too little available play for the
mechanical locking (e.g., the surface area of a recessed portion that is
formed in the correction system is reduced), accordingly, the projection
that is formed on the locking mechanism may not engage the recessed
portion and it may not be possible to lock the correction system.
Therefore, a certain amount of play must be provided to insure reliable
locking.
If there is too much play in the locked portion, however, when the
correction system, which gravity places in the outermost edge of the play
before the initial locking is released, is moved to the center of the
range of movement of the play at the same time as the locking is released,
an image that has passed through the exposure system (to include the
correction system) is greatly changed instantaneously, and an operator has
a strong sense of incongruity when observing an object through a TTL view
finder such as is used in a single-lens reflex camera.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, an image blur prevention
apparatus comprises; a movable member which moves for image blur
prevention, a holding device which holds the movable member, an operating
device which, for image blur prevention operates the movable member at a
predetermined position as a control center position, and a control device
which controls movement of the movable member between a holding position
by the holding device and the predetermined position, wherein the control
device controls a process for the movement between the holding position
and the predetermined position, whereat the movable member can be
appropriately operated when the movable member is to be held or is to be
released.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating the general structure of an image blur
prevention apparatus according to a first embodiment of the present
invention;
FIG. 2 is a diagram illustrating a circuit for detecting the output of a
fluctuation sensor shown in FIG. 1;
FIG. 3 is a diagram illustrating the essential portion of a correction
system shown in FIG. 1;
FIG. 4 is a specific circuit diagram illustrating a correction system
position detection means shown in FIG. 1;
FIG. 5 is a specific circuit diagram illustrating the image blur prevention
apparatus shown in FIG. 1;
FIG. 6 is a flowchart of the processing for the locking release that is
performed by the image blur prevention apparatus shown in FIG. 1;
FIG. 7 is a flowchart of the image blur prevention processing performed by
the image blur prevention apparatus shown in FIG. 1;
FIG. 8 is a flowchart of the processing for the image blur prevention
apparatus shown in FIG. 1 that is performed at the time of locking;
FIG. 9 is a flowchart of the processing, according to a second embodiment
of the present invention, for an image blur prevention apparatus before
the locking is released;
FIG. 10 is a flowchart of the processing, according to the second
embodiment of the present invention, for changing the setting of the
driving center data;
FIG. 11 is an explanatory diagram for time TA that is held by a timer shown
in FIG. 7;
FIG. 12 is a diagram illustrating the general structure of a conventional
image blur prevention apparatus; and
FIG. 13 is a specific diagram illustrating the range of movement of the
play for the mechanical locking of a correction system shown in FIG. 12.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(First Embodiment)
The preferred embodiments of the present invention will now be described
while referring to the accompanying drawings.
FIG. 1 is a diagram illustrating the general structure of an image blur
prevention apparatus according to a first embodiment of the present
invention. In FIG. 1, a control circuit 1 controls all the operations of
the apparatus; switch means 2 is used by a photographer, for example to
start and to end the operation performed for image blur prevention; and
adjusting data setting means 3 holds data inherent to an apparatus that
incorporates the image blur prevention apparatus.
A fluctuation sensor 4 detects vibrations of an entire apparatus, which are
caused by the movement of the hands of a photographer, relative to
absolute space-time. While the output of the fluctuation sensor 4 is
passed through a high pass filter 5 and an integral means 6, which are
located at the next stage, unwanted DC components, etc., are removed from
the output, and the result is converted into an appropriate fluctuation
displacement signal by integral processing. The output of a sensor signal
will be specifically explained while referring to FIG. 2.
FIG. 2 is a diagram illustrating a detection circuit for the output of the
fluctuation sensor 4 shown in FIG. 1. FIG. 2 shows a specific circuit for
detecting the output of the fluctuation sensor 4, for which a so-called
fluctuation gyro that detects an angular velocity is employed.
In FIG. 2, based on a drive signal from a driving circuit 102, an
oscillator 100 is driven in resonance with a predetermined frequency/a
predetermined amplitude. When, in this condition, rotation angular
velocity .omega. around the axis acts on the oscillator 100, the output of
the oscillator 100 is a result obtained by multiplying a drive frequency
signal of the oscillator by the rotation angular velocity .omega., i.e.,
an AM demodulated signal. The demodulated signal is modulated by a
synchronous phase detection circuit 101 using a frequency signal that has
the same driving/resonance frequency as the oscillator 100, and only a
signal that corresponds to the angular velocity .omega., which acts on the
oscillator 100, is output.
Normally, because of an imbalance, etc., in the oscillator 100, a
predetermined voltage output (called a DC offset) appears as the output of
the synchronous phase detection circuit 101, even when the angular
velocity .omega.=0. To remove the DC element, connected to the output side
is the high pass filter 5, which includes an operational amplifier 103, a
capacitor 104, and resistors 105, 106 and 107.
Therefore, the signal elements that have frequencies lower than a cutoff
frequency of the high pass filter 5, which is determined by constants for
the capacitor 104 and the resistor 105, are removed in the high pass
filter 5. An integral value for the output, after it has passed through
the high pass filter 5, is obtained by an integral circuit 6, which
includes an operational amplifier 108, resistors 109 and 111, and a
capacitor 110, and the angular velocity signal is converted into an angle
signal. An analog SW 112 is used to short-circuit both ends of the
capacitor 110 to alter a time constant of the integral circuit 6, and is
controlled by a control signal INTON.
Referring back to the structure in FIG. 1, the final output of the thus
obtained sensor signal is input from the integral means 6 to addition
means 7. The addition means also receives an output of driving center
combination means 15, which transmits final driving center data that are
obtained by combining an output of first driving center setting means 13
and an output of second driving center setting means, both outputs being
determined based on set data from a control circuit 1, which will be
described later.
Further, the addition means 7 receives the output of a correction system
position detection means 10, for indicating the current position of a
correction system 9, that optically corrects the blurring of an image,
which should be in focus through an exposure optical system at a
predetermined position, that is caused by the movements of the hands of a
photographer.
The output of the addition means 7 is transmitted to correction system
driving means 8, and the output of the correction driving means 8 is used
for correction by the correction system 9. When the phase of the detected
output and the sensitivity (output for each unit of correction angles) of
the position of the correction system are properly specified, the feedback
control can be so accomplished that the correction system 9 is driven in
accordance with the sensor output and the driving center data. When the
correction operation is not performed, the correction system 9 is fixed
mechanically by a lock 12 that is driven by lock driving means 11.
FIG. 3 is a diagram illustrating the essential portion of the correction
system 9 shown in FIG. 1. The structure of a shift correction optical
system, wherein one part of a lens group can be freely moved across a
plane perpendicular to a light axis, will now be described as the
correction system according to this embodiment while referring to FIG. 3.
In FIG. 3, a correction lens system 154, which is one part of an exposure
lens system, can be moved to an arbitrary position on a plane
perpendicular to a light axis by using a method that will be described
later. For movement in the x axial direction, the correction lens system
154 is controlled as desired by a magnetic circuit, which includes a yoke
150 and a magnetic coil 152, in accordance with the strength and the
direction of the flow of a current that passes across the magnetic coil
152. Similarly, for movement in the y axial direction, the correction lens
system 154 is controlled by a magnetic circuit that includes a yoke 151
and a magnetic coil 153.
The actual movement of the correction lens 154 is optically/electrically
detected, without making contact, by a combination of IRED portions 156
and 157, which are moved together with the correction lens 154, and PSDs
(Position Sensitive Devices) 158 and 159, which are fitted into a lens
barrel 161 that holds the entire shift lens. A specific detection method
will be explained while referring to FIG. 4.
FIG. 4 is a specific electric circuit diagram illustrating the correction
system position detection means 10 shown in FIG. 1. A signal light that is
projected by an IRED 192 enters a PSD 170, and in accordance with the
incident position of the PSD 170, currents Ia and Ib that are output by
the PSD 170 are branched. The current Ia is converted into a predetermined
voltage Va by a current-voltage conversion circuit that consists of an
operation amplifier 171 and a resistor 172. In the same manner, the
current Ib is converted into a predetermined voltage Vb by a
current-voltage conversion circuit that consists of an operational
amplifier 173 and a resistor 174.
These two voltages are added together by an addition circuit, which
includes an operational amplifier 180 and registers 181, 182 and 183, to
obtain an output -(Va+Vb). This output is transmitted to an IRED driver
circuit that includes an operational amplifier 187 and resistors 188, 189
and 191. A reference voltage KVC is supplied to one of the input terminals
of the IRED driver circuit, and a feedback system for automatically
adjusting an IRED current is provided so that the output of the addition
circuit equals the voltage KVC.
The outputs Va and Vb are transmitted to a subtraction circuit, which is
composed of an operational amplifier 175 and resistors 176 through 179, to
obtain the output -(Va-Vb). This output is converted into a predetermined
voltage by an inverting amplification circuit, which has an operational
amplifier 184 and resistors 185 and 186, to provide a final correction
system position output. The processing circuit shown in FIG. 4 is provided
in both x and y axial directions in the same manner, and the outputs are
used to perform feedback control of the correction optical system.
Referring again to FIG. 3, reference numeral 155 denotes charge pins. A
lock mechanism 160 mechanically halts the movement of the correction
system 9. In accordance with a current that flows across the magnet and
the direction of its flow, a projection 163 of a mechanical lock member
moves in the Z direction to perform locking/unlocking, and rapidly
engages, or disengages, a recessed portion 164 that moves with the
correction lens 154. Support balls 162 are swing & tilt stoppers to
restrict the movement of a shifting system in a direction in which it may
fall.
FIG. 5 is an electric circuit diagram illustrating the image blur
prevention apparatus shown in FIG. 1. FIGS. 6 through 8 are flowcharts of
the processing that is performed by the image blur prevention apparatus
shown in FIG. 1.
The actual processing will now be described while referring to FIGS. 5, and
6 through 8. First, FIG. 5 shows a specific circuit structure of the
entire image blur prevention apparatus in the block diagram in FIG. 1,
with the exception of the fluctuation sensor signal processing circuit
shown in FIG. 2 and the correction system detection circuit shown in FIG.
4.
A CPU 200, for controlling the entire apparatus; an A/D converter 201, for
reading correction system position output to the CPU 200; and a D/A
converter 202, for outputting driving center correction data, correspond
to the block A indicted by broken lines in FIG. 1.
The CPU 200 internally includes a timer circuit 203, for setting a
mechanical locking time, which will be described later, and a time for
changing driving center data; a serial interface circuit 204, for
performing data communication with an E .sup.2 PROM 205 in which external
adjustment data are stored; and an internal register 239, for temporarily
storing results obtained by computation.
An ordinary addition circuit that is composed of an operational amplifier
206 and resistors 208 through 211 corresponds to the addition means 7
shown in FIG. 1. The addition circuit adds together the output of the
fluctuation sensor 4, the positioning output of the correction system (the
shifting system, etc.) and the driving center correction data output of
the D/A converter 202. On the input side of the apparatus, an analog SW
207 is provided between the sensor output and the resistor 208, and is
employed to selectively input/not input the sensor output to the addition
circuit in accordance with control signal ISON from the CPU 200.
The output of the operational amplifier 206 is transmitted to a phase
correction circuit that includes an operational amplifier 212, resistors
213 and 215 and a capacitor 214. This correction circuit improves the
stability of the system by advancing the phase of a feedback loop so as to
perform feedback control for the entire correction system.
Sequentially, the output of the operational amplifier 212 is transmitted to
a power amplification circuit that consists of an operational amplifier
216, resistors 217 and 218 and transistors 219 and 220. The power is
supplied to a driving coil 223 by the output of the power amplification
circuit, and as is explained in the processing of the correction lens
system, the shifting lens 225 is moved by driving power supplied by a
predetermined magnetic circuit. Switch means that has a transistor 221 and
a resistor 222 controls a driving circuit by using a ›SFTON! signal from
the CPU 200.
FIG. 5 shows the structure of the correction circuit relative to the
movement in one axial direction (y axial direction). Since the structure
of the correction circuit relative to the movement in the other direction,
i.e., the movement in the x axial direction, is the same, no explanation
for it will be given. The phase correction circuit and the power
amplification circuit correspond to the correction system driving means 8
shown in FIG. 1.
An H bridge for which transistors 234 through 237 are used is a circuit
that supplies to a driving coil 227, in a predetermined direction, a
current having a predetermined strength. A locking mechanism for
mechanically locking the shift lens 225 is operated by power that is
supplied to the driving coil 227.
FIG. 6 is a flowchart of the processing performed by the image blur
prevention apparatus shown in FIG. 1 before the locking is released. FIG.
7 is a flowchart of the image blur prevention processing for the image
blur prevention apparatus shown in FIG. 1. FIG. 8 is a flowchart of the
processing performed at the time of locking by the image blur prevention
apparatus shown in FIG. 1.
The program control of the CPU 200 will now be described while referring to
the flowcharts in FIGS. 6 through 8.
First, while referring to the flowcharts in FIGS. 6 and 7, an explanation
will be given of the control exercised for starting the image blur
prevention operation from the condition where the image blur prevention
operation is halted (the correction system is locked). A check is
performed to determine whether or not the SW 238, shown in FIG. 5, which a
photographer manipulates to start image blur prevention, is in the ON
state (S300). When the SW 238 is in the ON state, program control moves to
S301. When the SW 238 is in the OFF state, program control returns to
S300. Then, the fluctuation sensor and the fluctuation sensor processing
circuit shown in FIG. 2 are energized (S301). Following this, the
correction position detection circuit shown in FIG. 4 is energized (S302).
In synchronization with serial synchronization clock SCK, the reading of
adjustment data for individual lenses that are set in the E.sup.2 PROM 205
is begun by the CPU 200, via the serial interface 204 that is inside the
CPU 200, along a serial reception line SDI (S303).
Then, a check is performed to determine whether or not all data have been
read (S304). When the reading of all the data has been completed, as
inherent lens data that were read from the E.sup.2 PROM 205, the driving
center adjusting data are set for yaws and pitches in registers D2Y and
D2P of the CPU 200 (S305). The driving center data that are stored in the
E.sup.2 PROM 205 normally indicate values near the center of the optical
axis, as is explained in FIG. 13, and in the design, these values are
those that are positioned in the vicinity of the center of the play for
the mechanical locking. In this embodiment, the stored driving center
substantially corresponds to the center of the play for the mechanical
locking. However, the driving center may be set so that it differs from
the center of the play for the mechanical locking. The driving center
location is determined by a support mechanism for the correction system
shown in FIG. 3, and the driving center can be set so that the movable
range for the correction system is centrally positioned.
When the CPU 200 changes an ADSTR signal to H for the A/D converter 201,
the A/D converter 201 performs A/D conversion of the current correction
system position output (S306). The state of the ADCMP signal (H indicates
completion) output by the A/D converter 201 is examined to determine
whether or not the A/D conversion has been completed (S307). The result is
set in register A, inside the CPU 200, across data line ADDATA (S308).
Since the reading operation for the correction system position output data
is performed the same for both yaws and pitches, only the data reading for
one of the axes has been explained.
When the ADSTR output becomes level L, the operation relative to the A/D
converter 201 is halted (S309). Then, the current correction system
position output value that was read by the A/D converter 201, and set in
the register A inside the CPU 200, is subtracted from 0, i.e., the sign of
the value is inverted and the result is set for yaws and pitches in
registers D1Y and D1P of the CPU 200 (S310). The contents of the register
are output to the D/A converter across line DADATA (S311). Thereafter, the
output DASTR of the CPU 200 is changed to level H, and an analog output
that corresponds to the DADATA is generated by the D/A converter 202 and
transmitted to the previously described addition circuit (S312).
Program control then moves to the flowchart in FIG. 7.
The timer circuit 203 in the CPU 200 is reset (a timer count value is set
to 0) (S313). Then, when the ›SFTON! output of the CPU 200 is altered to
level L and the transistor 221 is rendered off, the shifting system coil
driving power amplification circuit, which includes the operational
amplifier 216, etc., is set to the operating state (S314). Therefore,
since at this time, the analog SW 207 is still in the OFF state, the
output from the fluctuation sensor 4 is not added for the driving of the
shifting system, and the correction system position output and the driving
center set data from the D/A converter 202 are added together. In
accordance with the result, it is determined to energize the shifting
system driving coil 223 (the coil 224 for the pitches). At this time, the
data having the inverted sign, the first shifting system position output,
are set as the initial driving center data, as is described above. Thus,
feedback control is performed so that the shifting driving circuit shown
in FIG. 5 can hold the shifting system at a position that substantially is
the initial position (the position in the locked state).
In this condition, when the UNLOCK output of the CPU 200 is changed to
level H, the output of the inverter 228 becomes level L, and as a result,
the transistor 234 is rendered on across the resistor 230 and the
transistor 237 is rendered on across the resistor 233. Therefore, a
current flows across the mechanical lock driving coil 227 in a direction
indicated by an arrow a (S315). Consequentially, the mechanical lock 226
is unlocked by the shifting lens 225 and provides the lock released
condition. At this time, feedback control has begun, so that the shifting
system is halted at the initial locked state. Even when the locking is
released, the shifting system is not greatly displaced, such as being
dropped.
The timer circuit 203 of the CPU 200 is activated and begins the count
(S316). A check is performed to determine whether or not a time TL, during
which a current is supplied to the coil 227 until the UNLOCK process is
completed, has elapsed (S317). When the time TL has elapsed, the UNLOCK
output becomes L and the supply of the current to the coil 227 is halted
(S318). Thereafter, the timer circuit 203 is reset (S319), and a check is
performed to determine whether or not a timer count value has reached a
predetermined time TA (S320).
When the timer count value has not reached the time TA, in order for the
driving center data of the shifting system to be changed as time elapses,
the result of either an expression, D1Y+t/TA.times.(D2Y-D1Y) or
DIP+t/TA.times.(D2P-DIP), is sequentially transmitted to the D/A converter
202, across the DADATA line, until the timer count value equals the
predetermined time TA (S321). It should be noted that in the expression
D1Y (or D1P) denotes the value in the resistor in which are set data
determined by the shifting system position in the initial locked state;
t/TA is a ratio of a timer count value t to the predetermined time TA; and
D2Y-D1Y (D2P-D1P) denotes the subtraction of D1Y (or D1P) from the
register D2Y (or D2P) in which are set the center position correction data
for the individual lenses.
Based on data from the CPU 200, the output of the D/A converter 202 is
changed in proportion to the time until the voltage value corresponding to
D1Y(P) equals the voltage value corresponding to D2Y(P), as is shown in
the explanatory diagram in FIG. 11. The shifting system is gradually moved
from the initial position before locking is released to the center of the
actual optical axis of the lens.
When, as a result of the process at S320, the timer count has reached the
time TA, the value of register D2Y (or D2P) is output across the DADATA
line, with the following driving center data being maintained as a
constant value. Thus, after the predetermined time TA has elapsed, the
correction system is driven mainly in the vicinity of the optical axis
(S322).
Then, since the ISON output of the CPU 200 becomes level H, the analog SW
207 is turned on and the sensor output is transmitted to the addition
circuit, and the correction optical system 225 is driven in accordance
with a fluctuation signal from the sensor (S323).
Following this, the INTON output of the CPU 200 becomes level L (this
output is level H in the initial state), and the analog SW 112, which has
short-circuited both ends of the capacitor of the integral circuit shown
in FIG. 2, is turned off. The integral device goes into the operating
state, and its output is changed to a signal that corresponds to the
amount of movement of the hands of a photographer. When the time that is
determined by the time constant of the integral device has elapsed, the
correction system is driven to correct for image blurring, and the
apparatus is set to the normal image blur prevention condition (S324).
The program control then moves to the flowchart in FIG. 8. The processing
from the beginning of an image blur prevention condition to the halting of
the image blur prevention will now be described.
A check is performed to determine whether or not the switch 238 shown in
FIG. 5 is in the OFF state (S325). When the switch 238 is OFF, the INTON
output of the CPU 200 becomes level H and the integral circuit shown in
FIG. 2 is reset. Therefore, since at this moment the sensor output becomes
independent of the fluctuation signal, the correction system is set and
becomes stationary in the vicinity of the optical axis, based on the
driving center data D2Y (or D2P) (by the 0-closed control that is
unrelated to the sensor output) (S326).
The timer circuit 203 of the CPU 200 is then reset (S327), and a check is
performed that uses the timer circuit 203 to determine whether or not a
predetermined time TR has elapsed (S328). In other words, program control
waits, since at S326 the integral device was reset until the correction
system completes the correction for fluctuation. When the predetermined
time TR has elapsed, the ISON output of the CPU 200 becomes level L, the
SW 207 in FIG. 5 is turned off, and transmission of the sensor output to
the correction system driving circuit is completely inhibited (S329).
After the timer circuit 203 is reset again (S330), a check is performed to
determine whether or not a timer count value has equaled a predetermined
time value TB (S331). When the timer count value has not yet reached the
target value, in order for the driving center data of the shifting system
to be changed as time elapses, in the period up until the timer count
value has reached the predetermined value TB, the value held by the
register D2Y (or D2P), in which data inherent to the individual lenses are
set, is added to a value that is obtained by multiplying D1Y (or D1P)-D2Y
(or D2P) by t/TB, which is the ratio of the timer count value t to the
predetermined time value TB, and the resultant value is sequentially
transmitted to the D/A converter 202 across the DADATA line (S332).
As is shown in FIG. 11, based on the data from the CPU 200, the output of
the D/A converter 202 is changed in proportion to the time that has
elapsed until the voltage value corresponding to D2Y (or D2P) equals the
voltage value corresponding to D1Y (or D1P). The shifting system is
therefore gradually moved from the substantially center optical axis
position to the initial position before the locking was released, as is
shown by TB in FIG. 11.
When, as the result of the determination at S331, it is found that the
timer count value has reached the predetermined time value TB, finally,
the value of the driving center data D1Y (or D1P), which corresponds to
the initial position data before the locking was released, is transmitted
across the DADATA line and via the D/A converter 202 to the shifting
system control circuit in FIG. 5 (S333). The shifting system is then
placed in the initial position before the locking was released.
When, under these conditions, the LOCK output of the CPU 200 becomes level
H, the transistor 235 is rendered ON via the inverter 229 and the resistor
231, and at the same time, the transistor 236 is rendered ON across the
resistor 232. A current therefore flows across the mechanical locking
driving coil 227, in a direction indicated by an arrow b, and the locking
member 226 begins to move toward the locked position (S334).
After the timer circuit 203 of the CPU 200 has been reset (S335), a check
is performed to determine whether or not a timing TL, which is required
for activation of the locking member 226, has elapsed (S336). When the
timing TL has elapsed, the supply of the current for the locking process
is halted (S337).
Sequentially, the ›SFTON! output of the CPU 200 becomes level H and the
transistor 221 is rendered on via the resistor 222, the shifting system
driving circuit, which includes the operational amplifier 216, is rendered
off, and the driving of the shift correction system is halted (S338).
Further, the energizing of the correction position detection system is
halted (S339), and the energizing of the sensor system is also halted
(S340). When all the processing has been completed, program control
returns to the start.
As is described above, in this embodiment, simultaneous driving of the
correction optical system and the mechanical locking release is avoided.
The initial position data D1Y (D1P) for the correction system, and the
driving center set data D2Y (D2P) are set to inhibit the sensor output.
The driving center is so controlled that it is changed gradually. As is
shown for the time TA in FIG. 11, when the locking of the correction
system is released, the driving center is gradually moved from the initial
position, before the locking has been released, toward the actual optical
axial center of the lens, while as is shown for the time TB in FIG. 11,
when the correction system is locked, the driving center is gradually
moved from the optical axial center position to the initial position,
before the locking has been released. As a result, the problem of
instability of the mechanical locking is resolved.
(Second Embodiment)
A second embodiment of the present invention will now be described while
referring to the accompanying drawings.
FIG. 9 is a flowchart of the processing for an image blur prevention
apparatus according to the second embodiment of the present invention.
FIG. 10 is a flowchart of the processing for changing the setting of
driving center data according to the second embodiment of the present
invention.
The general structure shown in FIG. 1 and the circuits shown in FIG. 5 are
also applied for the second embodiment.
First, in FIG. 9, the process at S400, for determining whether or not the
switch 238 in FIG. 5 is turned ON, through the process at S410, for
temporarily setting to D1Y (or D1P) a reference value of the driving
center data of the shift correction system, which moves from its initial
position when the locking is released, are the same as those at S300
through S310 in the first embodiment. An explanation for them will not
therefore be given, and only the processes in FIG. 10 that are different
will be described.
A check is performed to determine whether or not a difference between
initial driving center data D1Y (or D1P), which is determined by the
position of the shifting system before the locking is released, and
adjusting data D2Y (D2P), which are required for positioning the shifting
system substantially near the optical axis, including the variance in the
power of individual lenses, falls within the range reaching from
predetermined value -.alpha. to predetermined value +.alpha. (S411). More
specifically, when a value of the first driving center data, which is
determined by the position of the initial correction system (the position
in the locked state), is very near a value of the second driving center
data, which is original image blur prevention center data used to position
the shifting system near the optical axis (i.e., value .alpha. is very
small), no special correction is made for the first driving center data
that are determined by the first position of the shifting system, and the
value of the D1Y (or D1P) obtained at S410 is transmitted across a DADATA
line to a D/A converter 202. The driving center data for the shifting
system when the release of mechanical locking is begun are set (S415).
When, at S411, a difference between D1Y (or D1P) and D2Y (or D2P) does not
fall within the range extending from the predetermined value -.alpha. to
the predetermined value +.alpha., i.e., when the value of the first
driving center data that is determined from the first position of the
correction system differs greatly from the value of the second driving
center data for positioning the shifting system near the optical axis, a
check is performed to determine which is greater, D1Y (or D1P) or D2Y (or
D2P) (S412). When the value of D1Y (or D1P) is equal to or greater than
the value of D2Y (or D2P), the result obtained by subtracting
predetermined data .beta. from the value of D1Y (or D1P) is set again as
D1Y (or D1P) (S413). When the value of D1Y (or D1P) is smaller than the
value of D2Y (or D2P), the result obtained by adding predetermined data
.beta. to the value of D1Y (or D1P) is set again as the D1Y (or D1P)
(S414).
Since the image blur prevention and locking processes performed at S416 and
the following steps are the same as those performed at S313 through S340
in the first embodiment, no explanation for them will be given.
If the driving center data for the correction system are set only by
referring to the position of the shifting system before the release of the
mechanical locking, the shifting system is actually positioned outside of
the range of the mechanical play, as is shown in FIG. 13, due to steady a
deviation of the shifting system position, which is caused by a current
being supplied by which the shifting system is automatically maintained
when the feedback control is actually performed. If the driving center is
determined only by the shifting system position before it is energized,
when the feedback control for the shifting system is actually begun, the
driving force of the shifting system will act in the direction in which
mechanical play is extended, and as a result, the release of the
mechanical locking will be prevented. As is described above, therefore,
according to this embodiment, in the processes at S413 and S414, the
driving center data of the shifting system when the mechanical locking is
released is set in advance to a value that, by a predetermined value
.beta., is near the final driving center data for the image blur
prevention. When the shifting system is gradually moved from the set value
to the final driving center, stability upon the release of the mechanical
locking is improved more.
While the present invention has been described with respect to what is
presently considered to be the preferred embodiments, it is to be
understood that the invention is not limited to the disclosed embodiments.
On the contrary, the invention is intended to cover various modifications
and equivalent arrangements included within the spirit and scope of the
appended claims. The scope of the following claims is to be accorded the
broadest interpretation so as to encompass all such modifications and
equivalent structures and functions.
In addition, the individual components shown in schematic or block form in
the Drawings are all well-known in the camera arts, and their specific
construction and operation are not critical to the operation, or the best
mode for carrying out the invention.
The present invention may be carried out by combining the above embodiments
or technical elements, as needed.
The present invention may be realized by all, or a part, of the structure
recited in claims or the embodiments forming one apparatus, or being
coupled with another apparatus, or serving as components of an apparatus.
The present invention can be applied to various types of cameras, such as
single-lens reflex cameras, lens-shutter cameras and video cameras, other
optical devices and devices that are applied for these cameras, other
optical devices and other types of devices, or components that constitute
these devices.
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