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Description  |
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BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to cameras capable of correcting blurring
occurring due to camera movement or camera-shake (hereinafter referred to
as blurring), and particularly to cameras capable of blurring correction
which can perform automatic focusing control (hereinafter referred to as
AF).
Description of the Related Art
Cameras capable of correcting blurring have been proposed recently. As a
camera-shake sensor in a camera capable of blurring correction, one which
employs an angular velocity sensor is possible. The blurring correction is
performed by detecting camera-shake amount of a camera employing an
angular velocity sensor and driving a lens to correct it.
Recent cameras have an AF function. In a camera having an AF function, a
lens is automatically driven for focusing on an object. Then, acceleration
noise is produced in the camera-shake detecting sensor due to vibration of
the motor and vibration of the driving mechanism. It was then recognized
that the blur is not properly corrected because correct angular velocity
outputs cannot be obtained accordingly.
Furthermore, in a camera capable of blurring correction, the blurring
amount of image of an object to be photographed on film is corrected in
exposure of the film. In order to correct the blurring amount of the
object on the film, a blurring amount correcting lens provided in a group
of lenses is driven at a speed necessary for correction.
In a camera capable of hand-shake correction, the hand-shake is corrected
as described above. As compared to the performance of the blurring
correcting means, however, the speed required for correction of a
correcting lens for hand-shake correction is sometimes too fast for
correction, or sometimes the amount to be corrected is so large that the
correction is made insufficiently. In these cases, even with a camera
having correcting means, there is a problem that the hand-shake cannot be
sufficiently corrected, so that blurring exists in a picture.
In addition, cameras capable of flashlight emission and blurring correction
have been proposed recently. Only one power source place generally exists
in a camera, so that boosting for flash and driving of blurring detecting
sensors are generally performed using a single power source in a camera
capable of flashlight emission and blurring correction.
When a flash circuit is boosted by a power source, the voltage of a battery
is likely to fluctuate, so that a problem might occur that the data
provided by a shake detecting sensor such as an angular velocity sensor is
not correct due to the influence.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to perform blurring
correction correctly in a camera capable of detection of camera-shake.
It is another object of the present invention to perform blurring
correction as much as possible in a camera capable of detection of
camera-shake.
The above objects of the present invention are attained by a camera capable
of camera-shake detection including the following elements. That is, a
camera according to the present invention includes a camera-shake amount
detecting sensor for detecting a camera-shake amount of said camera, a
blurring corrector for correcting blurring of said camera on the basis of
said camera-shake amount, a focus adjusting optical system for focusing on
an object image, a driver for driving the optical system, and a controller
for controlling the driver and the blurring corrector so that the blurring
corrector does not use outputs of the camera-shake detecting sensor when
the optical system is being driven.
In the period in which vibration noises are produced because the optical
system is driven, the blurring correcting device does not use outputs of
the camera-shake detecting sensor. Accordingly, wrong detection of
blurring amounts is avoided. As a result, in a camera capable of
camera-shake detection, correct blurring correction is possible.
Preferably, a camera according to the present invention includes an
exposure amount controller for controlling exposure to film, a
camera-shake detecting sensor for detecting said camera-shake amount, a
blurring corrector for correcting image blurring caused by the
camera-shake in response to an output of the camera-shake detecting
sensor, a determining device for determining whether the camera-shake can
be properly corrected or not, an auxiliary light means for lighting the
object, and a controller for making the auxiliary lightening device emit
light when the determining device determines that the camera-shake cannot
be properly corrected in the exposure.
Generally, a blurring amount is expressed as a product of exposure time and
blurring velocity. When the above-identified exposure time or blurring
velocity exceeds a correctable amount, the determination device determines
that blurring correction is impossible. In this case, the blurring amount
can be reduced by reducing the exposure time. If the exposure time is
reduced at that time, however, the exposure amount decreases. Therefore,
in the present invention, flashlight is emitted to compensate for the
insufficient exposure amount due to the decrease in exposure time.
The foregoing and other objects, features, aspects and advantages of the
present invention will become more apparent from the following detailed
description of the present invention when taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a camera to which the present invention is
applied.
FIG. 2 is a block circuit diagram of the camera shown in FIG. 1.
FIGS. 3-6 and 10 are flow charts showing operation of the camera according
to the present invention.
FIG. 7 is a diagram showing an optical system of a camera according to the
present invention.
FIG. 8 is a flow chart showing main portions of the method of correcting
blurring according to the present invention.
FIGS. 9A-9C are diagrams showing relationship between a blurring velocity
of an image on a film surface and an exposure time.
FIGS. 11A-13 are flow charts showing operation of the camera in the case
where the blurring correction tracking according to the present invention
is impossible.
FIGS. 14A and 14B are diagrams for describing the effect in the case where
the blurring correcting is impossible.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a perspective view conceptually showing the structure of a camera
as one embodiment of the present invention. In a camera body 11, angular
velocity sensors Sx and Sy for detecting angular velocities in a
longitudinal shake direction and a lateral shake direction, respectively,
are provided in a plane (the x-y plane in the figure) vertical to an
optical axis (the z axis in the figure) of a taking lens 12.
FIG. 2 is a block circuit diagram showing portions related to control of
the camera shown in FIG. 1. Referring to FIG. 2, the camera according to
the present invention includes a microcomputer .mu.C administrating
sequence control of the entire camera, exposure calculation and exposure
control. To the microcomputer .mu.C, peripheral circuits CT.sub.1 and
CT.sub.2 which will be described in detail later, some switches for
controlling operation of the camera, and a power source for supplying
power to the microcomputer and the peripheral circuits CT.sub.1 and
CT.sub.2 are connected.
Peripheral circuit CT.sub.1 includes a light measuring circuit LM for
measuring brightness of an object, converting the same into a digital
signal and transmitting the same to the microcomputer .mu.C, a distance
measuring circuit MD for converting an analogue signal indicating the
distance supplied from a distance detecting circuit into a digital signal
and supplying the same to the microcomputer .mu.C, a lens driving circuit
LD for driving a lens for focus adjustment on the basis of the distance
obtained according to the data of the distance measuring circuit MD, an
exposure control circuit AE having a shutter also used for an aperture for
controlling the shutter on the basis of the shutter speed determined on
the basis of output of the light measuring circuit LM and also
automatically controlling the aperture, and a film sensitivity reading
circuit ISO for reading film sensitivity Sv recorded on a film chamber and
transmitting the same to the microcomputer .mu.C.
Peripheral circuit CT.sub.2 includes angular velocity sensors Sx and Sy for
detecting angular velocities in a longitudinal shake direction and a
lateral shake direction of the camera and transmitting the camera-shake
amount to the microcomputer .mu.C, and a blurring correcting lens control
circuit Cxy for driving a lens LC in a plane vertical to the optical axis
for correcting blurring which is caused by the camera shake. The shake of
the camera is corrected by the blurring correcting lens control circuit
Cxy supplying as an output a correction signal to the correcting lens
driving circuits Cx and Cy.
The microcomputer .mu.C further includes a display circuit DISP for warning
blurring, a zoom encoder ZEN for transmitting a focal length of taking
lens 12 which is a zoom lens to the micro computer .mu.C, a flash circuit
FL for emitting a flash light and an aperture encoder AVEN for
transmitting an aperture value to the microcomputer .mu.C.
Next, switches will be described. Switches connected to the microcomputer
.mu.C include a main switch SM which has an ON state for driving a camera
and an OFF state for keeping a camera standing still, a preparatory switch
S1 which is turned on upon a first stroke of a release button (not shown),
a release switch S2 which is turned on upon a second stroke of the release
button, and an exposure starting switch SST which is turned on when the
shutter starts operating to start exposure. When preparatory switch S1 is
turned on, preparatory operation such as the light measuring operation,
distance measuring are performed. When the release switch S2 is turned on,
exposure control is performed.
next, portions related to a power source will be described. A direct output
voltage Vo of power source battery E is supplied to peripheral circuits
CT.sub.1 and CT.sub.2 through a flash circuit FL and first and second
feeding transistors Tr1 and Tr2, respectively. A capacitor C1 for back-up
is charged by the power source battery E through a diode D1 for reverse
current prevention. A charging voltage V.sub.DD of capacitor C1 for
back-up is supplied to the microcomputer .mu.C, the display circuit DISP
and the zoom encoder ZEN, the aperture encoder AVEN. The above-described
peripheral circuits CT.sub.1, CT.sub.2 include circuits of large power
consumption, so that the voltage of power source battery E may temporarily
decrease when it is being driven. Even in the voltage decrease time, the
microcomputer .mu.C is supplied with power from capacitor C1 for back-up,
so that it operates properly.
Now, the description about a hardware configuration of the embodiment is
completed. Next, the soft wear configuration of the present embodiment
will be described.
FIG. 3 is a flow chart showing contents of an interruption SMINT carried
out when the main switch SM is operated to be switched from OFF to ON or
from ON to OFF. If this interruption SMINT is produced, it is determined
first as to whether the main switch SM is ON or not (#5). If the main
switch SM is OFF, it is determined that the main switch SM is operated
from ON to OFF. As a result, boosting of flash circuit FL is stopped, the
first feeding transistor Tr1 is turned off, and power supply to the first
peripheral circuit CT.sub.1 including light measuring circuit LM and so
forth is stopped. Next, the second feeding transistor Tr2 is turned off,
and power supplying to the second peripheral circuit CT.sub.2 including
angular velocity sensors Sx and Sy is stopped. The display is eliminated
and the microcomputer .mu.C attains a half state (#65-#75). If the main
switch SM is ON in step #5, all the flags are reset and boosting of the
flash circuit is started to start charging a capacitor (not shown) of
flash circuit FL. Next, the feeding transistor Tr2 is turned on to start
supplying power to the second peripheral circuit CT.sub.2 including
angular velocity sensors Sx and Sy, and a timer T.sub.1 is reset and
started (#10-#20). The timer T.sub.1 is a holding timer for holding power
supplying to peripheral circuits CT.sub.1 and CT.sub.2. Next, a
determination is made as to whether preparatory switch S1 is ON or not in
the step #25, and if it is ON, the subroutine of S1 ON is carried out in
step #30 and the program returns to step #25.
FIG. 4 is a flow chart showing the subroutine of the above-described S1 ON.
When the preparatory switch S1 is turned on, boosting of flash circuit FL
is stopped (#100). Switch S1 is turned off and a determination is made as
to whether a flag S1 OFF F indicating that a hold time (10s) has passed is
set or not (#105), and if it is set, it is reset, transistor Tr2 is turned
on, and power supply holding timer T.sub.1 is reset-started and the
program advances to step #125 (#110-#120).
If the flag S1 OFF F is not set in step #105, the program immediately
advances to step #125, transistor Tr1 is turned on to supply power to
peripheral circuit CT.sub.1 and light measuring data and distance
measuring data are inputted (#125-#135).
Next, referring to FIG. 5, a subroutine of the light measuring shown in
step #130 of FIG. 4 will be described. A brightness value Bv is read from
light measuring circuit LM, and the film sensitivity Sv is read from film
sensitivity reading circuit ISO. An exposure time T.sub.EV is found from
the exposure value Ev obtained as exposure value Ev=Bv+Sv, and the program
returns (#205-#220).
Referring to FIG. 4 again, next, a focal length F is read from zoom encoder
ZEN (#140), a flag FLF indicating flash light emission is reset (#150),
and it is detected whether a flash circuit FL has been charged or not
(#160). If charging of the flash circuit FL is not completed (when the
potential of a terminal CHC shown in FIG. 2 is H, "H" corresponds to high
level whereas "L" corresponds to low level hereinafter), the program
advances to step #165, and boosting of flash circuit FL is started.
Specifically, the potential of a terminal STA is made H (#165). Next, if
warning of blurring is made in step #170, a warning display of
camera-shake is eliminated and the program returns to step #160 (#170,
#175). Here, the warning display is eliminated when flash circuit FL is
boosted because the blurring amount is not calculated in boosting in which
the voltage of the battery is very likely to fluctuate and the data
indicating the blur amount is not precise. When charging of flash circuit
FL is completed in step #160 (when the potential of a terminal CHC is L),
boosting of flash circuit FL is stopped (the potential of the terminal FTA
is made L) and a determination is made as to whether release switch S2 is
turned on or not (#180, #185). If release switch S2 is ON, exposure is
controlled, and the program returns (#185, #190). If switch S2 is not ON
in step #185, a determination is made as to whether switch S1 is ON or
not, and if switch S1 is OFF, the program returns (# 195). When switch S1
is ON in step #195, the blurring amount is calculated and displayed, and
program returns to step #160 (#195-#205).
Referring to FIG. 6, a subroutine of blurring amount calculation shown in
step #200 of FIG. 4 will be described. First, angular velocities (shake
data) .DELTA.Vx and .DELTA.Vy are supplied from angular velocity sensors
Sx and Sy, respectively (#250). Assuming that the preceding angular
velocity Bx is LBx, finding an angular velocity .DELTA.Bx in the x
direction on the image surface according to the focal length f, a flag BLx
flag indicating that the angular velocity (blurring amount) in the x
direction is large is reset (#255-#265).
The angular velocity (blurring data) is found according to the focal length
because the blurring amount changes with the focal length, which increases
as the focal length increases.
Next, details of the blur amount calculation will be described. An angular
velocity obtained from outputs from angular velocity sensors Sx and Sy
(wherein the electric charge amount is converted into a voltage) is
regarded as .theta.. Here, the camera-shake amount B detected by the
angular velocity sensors Sx and Sy can be expressed as follows,
B=.theta.
A blurring amount .DELTA.u in a surface equivalent to that of a film is a
function of focal length f of a taking lens 12 at that time and a function
of tangent of the blur angular .theta.. Accordingly,
.DELTA.u=f.multidot.tan.theta. (1)
Also, .DELTA.u=f.multidot.tan (f.theta.dt). (2)
Here, when an image velocity on film is FB, then
##EQU1##
The speed UB for moving a correcting lens for blurring correction has a
constant relationship with blurring velocity u, and then if a constant is
a, the following expression holds.
##EQU2##
This Du/dt has a limitation for movement, which is expressed as UB.sub.K.
Then, the speed UBx at which the correcting lens is to be moved calculated
from the obtained angular velocity can be expressed as follows,
##EQU3##
In the expression, an index x indicates a value about the x direction. In
step #285 of FIG. 6, determination is made as to whether the obtained
speed Ubx at which a correcting lens is to be moved for blurring
correction is within UB.sub.K which is a movable limitation speed or not,
in other words, whether the obtained speed to be corrected is within a
correctable range or not.
The speed UB at which a correcting lens is to be moved is, UB=a.multidot.FB
and the following relationships hold,
Ubx=a.multidot.FBx
UBy=a.multidot.FBy
UBK=a.multidot.FBK
That is, the determination in step #285 means the same as the determination
about whether .vertline.Fbx.vertline..gtoreq.FB.sub.K or not.
Since a blurring amount can be obtained by a product of blurring speed and
blurring. It is assumed that exposure time T.sub.EV is generally necessary
for photographing. In view of this, time usable for correction T.sub.K is
examined. The time usable for correction T.sub.K is found out on the basis
that the correcting lens is moved at the correctable maximum speed
UB.sub.K in one direction.
Returning to step #285 of FIG. 6, when it is determined that the speed Ubx
at which a correcting lens is to be moved in an x direction is a
correctable speed UB.sub.K or more, the program advances to step #290,
where it is determined whether the exposure time T.sub.EV is longer than
the time usable for correction T.sub.K or not.
Next, a description will be given to the uncorrectable blurring amount Blx.
For the correcting lens limitation speed UB.sub.K and the speed at which
it is to be moved Ubx, the blurring speed on the film surface is expressed
as FB.sub.K and Fbx. In this case, if exposure time T.sub.EV .gtoreq.time
usable for correction T.sub.K, uncorrectable blurring amount
Blx=(.vertline.Fbx.vertline.-FB.sub.K).multidot.T.sub.K
+.vertline.Ubx.vertline..multidot.(T.sub.EV -T.sub.K), and,
T.sub.EV <T.sub.K, then,
Blx=(.vertline.Fbx.vertline.-FB.sub.K).multidot.T.sub.EV
then, the program advances to step #330.
FIG. 7 is a diagram showing a lens optical system of a camera with blurring
correction according to the present invention. Referring to FIG. 7, the
optical system according to the present invention will be described. The
optical system of a camera with blurring correcting according to the
present invention includes an AF lens AFL driven by an AF motor for
focusing, and a group of lenses including a correcting lens LC moving
vertically to an optical axis for blurring correction. With an output B of
an angular velocity sensor Sx (only x direction is considered here), the
correcting lens LC is moved at a speed of UB in the direction designated
by the arrow in the figure. When the correcting lens LC is moved at a
speed UB in the direction designated by the arrow in the figure, the image
on the surface of the film FP moves at a speed of FB. The motor for AF is
located in the vicinity of the camera body 11 where an angular velocity
sensor Sx is located rather than in the vicinity of the lens optical
system.
FIG. 8 is a flow chart schematically showing the method of blurring
correction according to the present invention. First, a blurring amount is
calculated (#900), and a moving velocity Ubx to be corrected by the
correcting lens shown in FIG. 7, exposure time T.sub.EV and time usable
for correction T.sub.K are calculated (#905). Next, on the basis of the
above-described calculated results, it is determined whether the
correcting lens LC is a lens movable at a speed necessary for correction
or not (#910). Specifically, a determination is made as to whether the
speed UB at which the correcting lens is to be moved is smaller than the
limitation speed UB.sub.K of the correcting lens. If a determination is
made in step #910 that the speed Ubx at which the correcting lens LC is to
be moved is smaller than the limitation speed UB.sub.K, the program goes
to step #915, and it is determined whether the exposure time T.sub.EV
exceeds the permittable exposure time T.sub.K or not (#915). If it is
determined that the exposure time T.sub.EV does not exceed the exposure
permittable time T.sub.K in step #915, tracking for blurring correction is
possible since there is no problem in connection to the moving speed for
correction of correcting lens LC and exposure time (#925). On the other
hand, if the exposure time T.sub.EV exceeds the permittable exposure time
T.sub.K in step #915, tracking for blurring correction is impossible
because of a problem concerning exposure time. The case corresponds to the
case III described later concerning FIG. 9C.
In the case where the speed Ubx at which the correcting lens LC moves
exceeds the limitation speed UB.sub.K of the correcting lens in step #910,
a determination is made as to whether the exposure time T.sub.EV exceeds
the permittable exposure time T.sub.K or not as well as in step #915
(#920). If it is determined that the exposure time T.sub.EV exceeds the
permittable exposure time T.sub.K in step #920, it corresponds to the case
II described concerning FIG. 9B, and if the exposure time T.sub.EV does
not exceed the permittable exposure time T.sub.K, it corresponds to the
case I described concerning FIG. 9A. Anyway, in these cases, blurring
correction tracking is impossible (#930).
Next, the cases where blurring correction tracking expressed in the case
I-case III described above is impossible will be described.
FIGS. 9A-9C are diagrams for showing blurring correction tracking
impossible regions in the case corresponding to the cases I-III in which
blurring correction tracking is impossible described in step #830 of FIG.
8, respectively. In each figure, an axis of abscissa indicates time and
the axis of ordinate indicates the image velocity on the film surface.
Accordingly, the area shown in the XY plane shows a distance, or blurring
amount and so fourth.
In FIG. 9A, as described in step #930 of FIG. 8, Ubx .gtoreq.UB.sub.K,
T.sub.EV <T.sub.K. In FIGS. 9A-9C, the blurring correction limitation
speed is expressed using the image speed Fbx on the film surface and so
forth but not using a moving speed Ubx of a correcting lens LC and so
forth as in FIG. 8. However, since a proportional relationship exists
between them as known from the relationship shown in FIG. 7, it is
described using the image speed FBx on the film surface in FIGS. 9A-9C.
In FIG. 9A, as described above, the image speed Fbx on the film surface
exceeds the correctable image speed .vertline.FBX.vertline. on the film
surface, so that .vertline.Fbx.vertline.-FB.sub.K corresponds to a
blurring amount for a unit time. By multiplying the same by the exposure
time T.sub.EV, that is, by the portion shown by the oblique lines in FIG.
9A, the blurring amount is expressed. Here, the camera-shake amount
detected by the angular velocity sensor .vertline.Bx.vertline. is assumed
to be constant.
FIG. 9B shows a case in which the image speed Fbx on the film surface
exceeds the correctable speed FB.sub.K of the image on the film surface,
and also the exposure time T.sub.EV exceeds the time usable for correction
T.sub.K. As in the case of FIG. 9A, the portion designated by oblique
lines indicates the blurring amount which cannot be corrected.
Accordingly, the blurring amount in this case can be obtained by adding
(.vertline.Fbx.vertline.-FB.sub.K).multidot.T.sub.K and a value obtained
by multiplying time which become unusable for correction (T.sub.EV
-T.sub.K) and a blurring amount for a unit time Fbx, that is,
.vertline.Fbx.vertline..multidot.(T.sub.EV -T.sub.K).
FIG. 9C shows a case where the image speed Fbx on the film surface is
smaller than the correctable limit speed FB.sub.K, so that blurring
tracking is possible concerning the image speed on the film surface, but
the exposure time T.sub.EV exceeds the time usable for correction T.sub.K.
In this case, the margin amount in the image speed on the film surface, or
the margin amount for blurring expressed as (FB.sub.K
-.vertline.Fbx.vertline.).multidot.T.sub.K compensates for a part of the
blurring amount on the exposure time side.
As described above, a blurring amount impossible to be corrected is
calculated. The blurring amount is obtained as Blx in steps #295, #305,
#315 and #320 of FIG. 6. In FIG. 6, the steps #285 through #320 are the
same as the steps #910 through #930 of FIG. 8, so that the description
thereof is not repeated. After those values are found out, the program
advances to step #330, and a determination is made as to whether the above
obtained uncorrectable blurring amount Blx exceeds the permittable
blurring amount BL.sub.K (blurring, but of an amount permittable on a
picture) or not. If the uncorrectable blurring amount Blx exceeds the
permittable blurring amount BL.sub.K, a flag BLxF is set and the program
advances to step #345. On the other hand, if the value is the permittable
blurring amount PL.sub.K or less, the program directly advances to step
#345 (#330-#340).
In the following steps #345-#415, the blurring amount in the y direction
BLy is obtained in the same manner as that in the x directions Blx as
described above, so that the description thereof is not repeated.
Next, in step #420, absolute values of shake amount detected by angular
velocity sensors in the x direction and the y direction are compared in
magnitude. Such a comparison is made because it is sufficient to take
larger one in x or y direction as a blurring amount. Accordingly, in steps
#440-#450, determining that the blurring amount in the y direction is
larger than the blurring amount in the x direction, the blurring amount
BLy in the y direction is inserted as the blurring amount BL. On the other
hand, in steps #425-#435, determining that the blurring amount Bx in the x
direction is larger than the blurring amount By in the y direction, the
blurring amount Blx in the x direction is inserted as the blurring amount
BL, and the program returns.
FIG. 10 shows a subroutine of display shown in step #205 of FIG. 4.
Referring to FIG. 10, if either one of flags Blxf, BLyF showing that a
blurring amount in the x or y direction is larger, blurring warning is
made, and if non of them is set, without making blurring warning, the
program returns (#430-#445).
Next, referring to FIG. 8 again, process in the cases I-III shown in FIGS.
9A-9C where blurring correction tracking is impossible will be described.
Also, in such cases, some approach must be applied to reduce blurring
amounts. In this invention, exposure time is reduced in order to reduce
blurring amount in such cases (#945). That is to say, as shown in FIG. 9A,
for example, the area designated by the oblique line portion corresponds
to a blurring amount. In order to reduce the blurring amount, the area of
the oblique line portion must be reduced. The blurring amount cannot be
corrected, however, by reducing the magnitude of Fbx-FB.sub.K by
increasing the image speed FB.sub.K on the film surface. This is because
FB.sub.K is a limitation image speed on the film surface.
Accordingly, in order to reduce the area of the oblique line portion, the
exposure time T.sub.EV should be moved toward the left side. That is,
reducing an exposure time reduces a blurring amount.
Just reducing exposure time, however, cannot implement sufficient exposure
amount. Accordingly, in the present invention, flash light emission is
used to compensate for the reduced portion of exposure time when reducing
exposure time (#950). After that, photographing is performed according to
a normal routine (#935).
Next, a flow of exposure control according to the idea of reducing exposure
time in order to reduce blurring amount as described above will be
described referring to FIGS. 11A-11C. First, in exposure control, AF
control is applied (#500). After completion of the AF control, blurring
amount calculation is performed (#505, #510). Blurring amount calculation
(input of shake data .DELTA.Vx, .DELTA.Vy) is performed after completion
of AF because of the following reasons. That is, when a lens is being
driven, vibration of a motor and vibration by driving mechanism is
produced. It becomes camera-shake amount (angular velocity). If blurring
correction is performed based on data which is not caused by camera-shake
actually produced by operation of a photographer, wrong correction is
performed in exposure.
Next, a determination is made as to whether flags showing that the
respective blurring amounts are large in the x and y directions are set or
not, and when none of them is set, the program proceeds to step #570
(#515, #520). If either one of flags Blxf and Blyf is set, the program
proceeds to step #525, to calculate exposure time TA. The exposure time TA
corresponds to the exposure time reduced to reduce a blurring amount as
described above, which is obtained by dividing the blurring amount
exceeding the permittable amount PL.sub.K by the angular velocity at that
time (a blurring amount for a unit time).
Next, a flow chart for calculating exposure time TA for reducing the
blurring amount will be described referring to FIG. 12. First, it is
determined whether the image speed .vertline.FB.vertline. on the film
surface is not less than the predetermined limit speed FB.sub.K on the
film surface or not (#526). If .vertline.FB.vertline.<FB.sub.K in step
#526, the exposure time TA is found by subtracting permittable value
BL.sub.K from an absolute value of the blurring amount (at this time
exposure time T.sub.EV >time usable for correction T.sub.K, and
.vertline.FB.vertline..multidot.(T.sub.EV -T.sub.K) is blurring amount BL)
and dividing the same by an image blurring amount .vertline.FB.vertline.
(#535).
When the image speed .vertline.FB.vertline. on the film surface is not less
than the limit speed FB.sub.K on the film surface in step #526, a
determination is made about T.sub.EV .gtoreq.T.sub.K. If, T.sub.EV
<T.sub.K, an exposure time TA for reducing a blurring amount is found out
by dividing (.vertline.BL.vertline.-BL.sub.K) obtained by subtracting a
permittable value BL.sub.K from a blurring amount .vertline.BL.vertline.,
by a value (.vertline.FB.vertline.-FB.sub.K) obtained by subtracting a
correctable speed FB.sub.K from an image blurring amount
.vertline.FB.vertline. (#527, #537). If T.sub.EV .gtoreq.T.sub.K in step
#527, a determination is made as to whether the blurring amount on the
image surface
{.vertline.BL.vertline.-.vertline.FB.vertline..multidot.(T.sub.EV
-T.sub.K)} has already exceeded the permittable value BL.sub.K or not
until exposure time T.sub.K (#530). If it is determined that it exceeds
the permittable value BL.sub.K in step #530, the exposure should be
finished before the exposure time T.sub.K, and the exposure time TA is
obtained by adding the time at which the blurring time until the exposure
time T.sub.K {.vertline.BL.vertline.-BL.sub.K
-.vertline.FB.vertline..multidot.(T.sub.EV -T.sub.K)} attains the
permittable value and the time T.sub.K -T.sub.EV together. On the other
hand, if {.vertline.BL.vertline.-.vertline.FB.vertline..multidot.(T.sub.EV
-T.sub.K)}.ltoreq.BL.sub.K in step #530, a part of the blur amount between
T.sub.K -T.sub.EV should be cut, the exposure time TA is obtained by
TA=(.vertline.BL.vertline.-BL.sub.K)/.vertline.FB.vertline. from
.vertline.BL.vertline.-.vertline.FB.vertline..multidot.TA=BL.sub.K, and
the program returns after processing of step #538 or #532.
Returning to FIG. 11A, after calculating TA in step #525, as stated above,
in order to reduce a blurring amount as much as possible, the exposure is
set rather under and flash light is emitted to compensate for the
insufficient exposure amount. Flag FLF showing this is set in step #540.
An exposure correction amount .DELTA.Ev is obtained from exposure time
T.sub.EV and TA. this is because if an exposure time T.sub.EV (Ev is
obtained) is obtained, if the exposure time TA is found out from the
relative relationship between the values, an exposure correction amount
.DELTA.E.sub.V is automatically found (#540, #545). A determination is
made as to if the exposure correction amount .DELTA.E.sub.V is 2E.sub.V or
more or not in step #550. If .DELTA.E.sub.V is 2E.sub.V or more, in
consideration of a latitude of film, .DELTA.E.sub.V is equal to 2, and if
.DELTA.E.sub.V is less than 2E.sub.V in step #550, it advances to step
#560. The exposure value E.sub.V is determined to be E.sub.V =E.sub.V
+.DELTA.E.sub.V, and an aperture value A.sub.VD when emitting flash light
for obtaining a corrected exposure amount is calculated on the basis of
the correction value and the program advances to step #570 (#560-#565).
Although there is provided a limit of 2 in a value of .DELTA.E.sub.V, it
is desired to make a determination in step #550 with a latitude instead of
2 if the latitude can be read from a film container.
Next, the program advances to an aperture value calculating subroutine
(#565), which contents will be described referring to FIG. 13. In the
aperture value calculating subroutine, an aperture value A.sub.VD is first
obtained with I.sub.V (emission amount)+SV (film sensitivity)-D.sub.V
(distance)-.DELTA.E.sub.V (#805). Then, from the obtained exposure amount
E.sub.V, an aperture value at that time (since a camera to which the
present invention is applied is of a shutter and aperture in one system,
an aperture value can be obtained in a one-to-one manner from an exposure
value as well as a shutter speed) is obtained. The aperture value AV and
the aperture value A.sub.VD at flash light emission obtained as described
are compared in magnitude (#810, #815). If AV>A.sub.VD in step #815, the
control aperture value A.sub.VC is AV, and if AV.ltoreq.A.sub.VD, the
control aperture value A.sub.VC is A.sub.VD. Thus, the aperture values are
made small respectively and the program returns (#815-#825). Referring to
FIG. 11B, the flow after step #570 will be described. Correction data Bx
and By are supplied to a correction circuit Cxy, and an exposure time
T.sub.EV is obtained again from the obtained exposure value E.sub.V (#570,
#575). In the repeated flow from exposure starting, a variable LTE showing
an exposure elapsed time until the previous time is reset, a variable
.DELTA.BL.sub.1 of the blurring amount in the previous time is made 0, an
exposure time T.sub.EV is supplied as an output to an exposure control
circuit AE, and next an exposure starting signal is supplied as an output
to the exposure control circuit AE (#570-#590). Thus, the exposure control
mechanism operates and a shutter is driven. next, a blurring amount is
calculated again, correction data Bx and By are supplied as outputs, and
blurring amount correction is performed even in a release time lag period.
(#595, #600). Then, starting of exposure on a film surface is detected by
switching on of a switch SST, when it attains ON, timer T.sub.E showing
exposure elapsed time is started, blurring amount is calculated for
blurring correction again, and the correction data Bx and By are supplied
as outputs (#615, #620). From step #615, depending on the exposure time
T.sub.EV, when the T.sub.EV is long, blurring amount is calculated a
plurality of times. To obtain time .DELTA.T.sub.E for performing the flow
once from the previous time to this time, .DELTA.T.sub.E is found by
T.sub.E -LT.sub.E. An exposure time T.sub.E at this time is regarded as
LT.sub.E (#625, #630). The uncorrected blur amount .DELTA.BL produced in
the time .DELTA.T.sub.E due to change in the blurring speed is obtained as
.DELTA.T.sub.E .times.(FB-FLB).multidot.1/2. Adding the blurring amount
until the previous time and the blurring amount .DELTA.BL at the present
time together, a new value .DELTA.BL.sub.1 is obtained (#650, #655). It is
multiplied by 1/2 as .DELTA.BL=.DELTA.T.sub.E .times.(FB-FLB).multidot.1/2
because, assuming that the change in speed gradually occurs, the blurring
amount produced at that time is calculated. Next, obtaining a remaining
time until completion of exposure T.sub.2 by T.sub.EV -T.sub.E, a blurring
amount produced in the time (uncorrectable amount) is predicted (#660).
First, a determination is made as to whether the blurring speed FB on the
film surface is the correctable maximum speed FB.sub.K or more or not, and
if FB.gtoreq.FB.sub.K, a determination is made as to whether the exposure
time T.sub.EV is the time usable for correction T.sub.K or more or not
(#665, #670). If it is not T.sub.EV .gtoreq.T.sub.K in step #670, it is
determined that a blurring prediction amount .DELTA.BL.sub.2
=(FB-FB.sub.K).times.T.sub.2 (#675). If T.sub.EV .gtoreq.T.sub.K in step
#670, a blurring prediction amount .DELTA.BL.sub.2
=(FB-FB.sub.K).multidot.T.sub.2 +FB.multidot.(T.sub. | | |
