JP2841666B2 - Camera image stabilizer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image blur correction device for a camera, and is suitable for use, for example, for photographing a low-luminance subject at a low shutter speed without a tripod.

[Prior art] Conventionally, incorporating an angular velocity sensor into a video camera,
It has been proposed to detect camera vibration (Japanese Unexamined Patent Publication No.
No. 61-289769). As the angular velocity sensor, there is a sensor using a high-speed rotating body like an auto gyro, and a sensor using Coriolis force generated by a vibrating tuning fork. By incorporating the above-described angular angle sensor into the camera and driving a part of the camera's taking lens to cancel image blur based on the output of the angular velocity sensor, it becomes possible to correct camera shake. Conceivable.
It is considered that if a stepping motor is used to drive a part of the taking lens, the accuracy of camera shake correction can be improved.

However, the stepping motor has two operation regions, a self-starting region and a through region. When the stepping motor is started immediately after the shutter is opened, control cannot be performed in the through region. Is lower than the performance limit of the stepping motor. Therefore, before the shutter is opened, the stepping motor is started in the self-starting area, and immediately before the shutter is opened, the pulse speed (corresponding to the driving speed of the stepping motor) is adjusted so as to be a speed necessary for image blur correction. Can be considered. With this configuration, even when the image shake speed immediately after the opening of the shutter is large and the pulse speed required for image shake correction is in the through region, operation in the through region is possible, and the correctable image shake speed is increased. (See Japanese Patent Application No. 1-261052).

[Problems to be Solved by the Invention] However, in the above-mentioned prior application, in the following operation before the shutter opening, the pulse speed is linearly increased, so that it is necessary to correct image blur from the pulse speed for the following operation. At the time of switching to a proper pulse speed, the change in the acceleration may be too large to cause a tone.

The present invention has been made in view of such a point,
The purpose is to smoothly switch from following operation before shutter opening to image blur correction operation after shutter opening in an image blur correction device of a camera that drives an image blur correction lens with a stepping motor. It is in.

[Means for Solving the Problems] In the present invention, in order to solve the above-mentioned problems, as shown in FIG.
And a stepping motor 2 for driving an image blur correction lens included in a camera optical system, and controlling the stepping motor 2 to input a sensor output a predetermined time before a shutter opening and to correct the image blur of the camera. A control circuit 3 for outputting pulses; the control circuit 3 controls a pulse generation circuit 31 for generating an image blur correction pulse based on a sensor output, and controls a pulse speed of the image blur correction pulse when the stepping motor is started. a determination circuit 32 for determining whether there is a possible self-starting or some uncontrollable through area in the region, the pulse rate V _F of the image blur correction pulse is determined to be in the through-region by determining circuit 32 A tracking circuit 33 that outputs a tracking pulse whose pulse speed increases with time for shifting from the self-starting area to the through area when the Pulse rate V _P of the follow-up pulse is output from the tracking circuit 33 in place of the image blur correction pulse outputted from the pulse generating circuit 31 until reaching the pulse velocity V _F of the image blur correction pulse during operation A comparison circuit 34 that uses the following pulse as an output of the control circuit 3; the following circuit 33 sets the pulse speed of the image blur correction pulse at a certain time t to V _F (t) and the acceleration to α _F (t). ), and when the pulse rate of the follow-up pulse and V _P (t), the time the minute time Delta] t has elapsed (t + Delta] t) pulse rate of follow-up pulses in V _P (t + Δt), and V _F (t + Δt) α _F (t + Δ
t) and V _p (t).

The function of the remaining time t _S of the tracking operation in the predetermined time, the weighting coefficient is _{W 1, W 2, V P} (t + Δt) = V P (t) + (Δt / t S) × {W 1 V _F (t + Δt) + W ₂ α _F (t + Δt) × t _S好 ま し い

Further, as another means for solving the same problem, the speed difference between the pulse velocity V _P of the follow-up pulses and the pulse rate V _F of the image blur correction pulse (V _F -V _P) is, the predetermined time The tracking pulse may be output so as to linearly decrease with time and become zero.

[Operation] FIG. 3 shows image shake (displacement) due to camera vibration. The displacement f _F (mm) is displayed as a locus of an image point existing at the center of the screen at the time t _A. The exposure periods A and B are both cases where the image was taken at a shutter speed of 1/10 second, but the timing of the shutter opening is different. The temporal change of the image blur speed f 'F corresponding to time course of the illustrated displacement f _F in FIG. 3 _(mm / s) shown in Figure 4. As apparent from the figure, 'but _F slows progressively from high speed, the speed f image blur immediately after the shutter opening Conversely the exposure period B' exposure period A image shake speed f immediately after the shutter opening the _F from the low speed It gets faster. In such a case, the stepping motor can follow the image blur during the exposure period B, but cannot follow the image blur during the exposure period A. Hereinafter, the reason will be described.

FIG. 5 shows the speed-torque characteristics of the stepping motor. Here, the speed of the stepping motor is represented by a pulse speed (the number of pulses [PPS] input to the stepping motor per second). In the self-starting region, the stepping motor can be started, stopped, and reversed instantaneously with any combination of pulse speed and torque. On the other hand, in the through area, the stepping motor cannot be started immediately, so it is necessary to start up in the self-start area, gradually increase the pulse speed, and then follow up to drive in the through area. Become.

Therefore, in the above-mentioned prior application (Japanese Patent Application No. 1-261052), in order to solve this problem, an output of a sensor for detecting camera vibration is input a predetermined time before a shutter opening, and a pulse for image blur correction is input. of when the pulse velocity V _F is in the through-region, as shown in FIG. 10, provided follow-up time t _SL in front of the exposure period a. In other words, when starting the stepping motor, give the pulse speed _VPS in the self-starting area,
Then, after a tracking time t _SL, so that the pulse rate V _PE through region, go directly increase the pulse rate V _P of the follow-up pulses. When the pulse speed V _F of the image blur correction pulse is reached at point P halfway, the following control is stopped, and thereafter, a pulse speed corresponding to the pulse speed V _F of the image blur correction pulse is given to the stepping motor. In this way, it is performed following operation of the pulse rate V _F of the image blur correction pulses in tracking time t _SL, the correction of image blur is performed from the shutter opening time. However, the moment when switched from pulse velocity V _P of the pulse for tracking a P-point pulse velocity V _F of the image blur correction pulse, the change in acceleration is large, there is a possibility that the stepping motor steps out.

Therefore, in the present invention, for example, and it determines the pulse rate V _P of the follow-up pulse by the principle shown in Figure 6. In the figure, the pulse speed of the image blur correction pulse at time tn, tn _{+ 1} is V _F (tn), V _F (tn _{+ 1} ), the exposure start time is t _ST , and the point (tn, V _F (tn )) from the point (tn _+1, a point in time t _ST of a line extended to V _F (tn ₊₁₎₎ and is Q, the speed at this point and V _Q. A point to point at _{(tn +1, V F (tn} +1)) from the straight line extending parallel to the time axis a time t _ST and R, the velocity at this point as V _R. Then, a straight line RQ M: a point that internally divides N and U, the velocity at this point as V _U. At this time,
The pulse speed V _P (tn ₊₁ ) to be obtained is determined by comparing the point U and the point (tn, Vp (t
n)) is the speed at time tn _{+ 1} on the straight line connecting If this is expressed by the formula, Becomes Actually, performs the calculation of the above equation from the read image blur correction pulse pulse rate V _F at time tn ₊₁ (tn _+1), pulse velocity V _P of the follow-up pulse (tn ₊ Since it takes some time to calculate ₁ ), it is preferable to correct this delay time. The combination of the coefficients M and N for obtaining the internal dividing point U is arbitrary, but in consideration of the easiness of calculation, a coefficient of a power of 2 such as 0, 1, 2, 4,. Is preferred. For example, if (M, N) is (0,1),
(1,1), the case is (1, 0), an example of calculating the pulse rate V _P of the tracking pulses to the pulse rate V _F of the image blur correction pulse in two ways Figure 7 (a), (B),
(C) and FIGS. 8 (a), (b) and (c) respectively. In the figure, the pulse rate were subjected to white circle V _P each time tn, tn _+1,
Are the calculation results in.

If this arrangement is adopted, the pulse rate V _P of the tracking pulses at time t _ST can catch up smoothly pulse velocity V _F of the image blur correction pulse, to stop the tracking control at this point, thereafter , controls the stepping motor at a pulse rate V _F of the image blur correction pulse. In this way, the image blur is corrected from the time when the shutter is opened.

Other configurations and operations of the present invention will be described in detail in the following description of embodiments.

Embodiment FIG. 1 is a block diagram of one embodiment of the present invention. In the figure, reference numeral 1 denotes a sensor for detecting camera vibration, which is composed of an angular velocity sensor. Reference numeral 2 denotes a stepping motor, which drives an image blur correction lens included in a photographing optical system of the camera. A control circuit 3 controls the stepping motor 2 based on the output of the sensor 1. Reference numeral 4 denotes a motor driver that drives the stepping motor 2 based on a control pulse output from the control circuit 3. 5
Is an interchangeable lens, and 6 is its built-in ROM.

Next, the configuration of the control circuit 3 will be described. 31 is a pulse generator circuit, and the angular velocity information f 'F obtained from the sensor 1 _(t), the image-shake correcting pulse based on image conversion coefficient K _B of the interchangeable lens 5 read from the internal ROM6 interchangeable lens 5 Occur. 32 is a decision circuit determines whether the pulse rate V _F of the image blur correction pulse is in the through area in the self-start area. 33 is a follow-up circuit for starting an operation when it is judged by the judgment circuit 32 pulse rate V _F of the image blur correction pulse is in the through-region, and outputs a tracking pulse. The follow-up circuit 33 operates during the exposure period A described above, but does not operate during the exposure period B. 34 is a comparator circuit for comparing the pulse rate V _P of the follow-up pulses and the pulse rate V _F of the image blur correction pulse, when the follow-up circuit 33 is operating, for follow-up if V _F> V _P outputs a pulse, and outputs the image blur correction pulse if V _F ≦ V _P.
However, when the tracking circuit 33 is not operating, the image blur correction pulse is output as it is.

FIG. 2A shows a drive system of an image blur correction lens used in the present embodiment. A gear G ₁ is mounted on the rotation shaft of the stepping motor 2. The turning force of gear G ₁ is gear
Is transmitted to crack G ₄ through G _2, G _3, is converted into linear driving force. Reference numeral 21 denotes an image blur correction lens which is held by a lens holding frame 20. Lens holding frame 20 is linearly driven by the rack G _4. Thus, when the rotation axis of the stepping motor 2 rotates by Δθ, the optical axis of the image blur correction lens 21 is shifted by Δd. Such a drive system is provided in each of the horizontal direction and the vertical direction of the photographing screen.

FIG. 2B shows a schematic configuration of a photographing optical system including an image blur correction lens used in the present embodiment. Reference numeral 22 denotes a main lens group of the photographing lens, which constitutes a photographing lens together with the image blur correction lens 21. FP is a focal plane, and light from a subject is imaged on the focal plane FP via the taking lens. When the amount of displacement of the image point on the focal plane FP of the time obtained by parallel Δd displaced in the optical axis of the image-shake correcting lens 21 and [Delta] L, the correction sensitivity L _H is defined by the following equation.

L _H = Δd / ΔL At this time, the rotation angle of the rotation shaft of the stepping motor 2 is defined as Δθ (degree), and the transfer coefficient K _BM is defined by the following equation.

_{K BM = Δθ / (360 ·} Δd) [rotation / mm] also defines an image conversion coefficient K _B by the following equation.

K _B = Δθ / (360 · ΔL) = {Δθ / (360 · Δd)} × (Δd / ΔL) = K _BM · L _H [rotation / mm] Displacement due to image shake is given by a function f _F (t). When
To cancel image blur with the image blur correction lens, use -f
The rotation angle of the stepping motor 2 may be controlled so as to give the image movement of _F (t). If the rotation angle of the stepping motor theta and (t), θ (t) = - K B · f F (t) [rotation] by differentiating both equations θ '(t) = - K B · f' F (T) [Rotation / sec] If the step angle of the stepping motor 2, that is, the angle rotated by the input of one pulse is θ _S (degrees),
Pulse rate V _F applied to the stepping motor 2 is given by the following equation.

_{V F = 360 · θ '(} t) / θ S = -360 · K B · f' F (t) / θ S [PPS] above pulse generation circuit 31, preset theta _S, the interchangeable lens 5 K _B input from the built-ROM 6, and because the angular velocity information f 'F inputted from the sensor 1 _(t) and outputs to calculate the pulse rate V _F. The operation start time of the pulse generation circuit 31 is a predetermined time before the shutter opening, for example, the turn-on time of the release switch or the start time of the mirror up of the flex camera.

Next, the following circuit 33 will be described. This tracking circuit 33
So when the pulse rate V _F of the image-shake correcting pulse is determined by the determination circuit 32 is in the through area, calculates the pulse rate V _P of the follow-up pulses, and outputs. The pulse speed of the image blur correction pulse at a certain time t is V _F (t), the acceleration is α _F (t), and the pulse speed of the following pulse is V
_P (t), the time (t
+ Δt), the pulse speed V _P of the following pulse (t + Δt)
Is given by the following equation.

V _P (t + Δt) = V _P (t) + (Δt / t _S ) × {W ₁ V _F (t + Δt) + W ₂ α _F (t + Δt) × t _S } where t _S is the remaining remaining Time, W ₁ , W ₂
Is a weighting coefficient. Weighting factors W _1, W ₂ is the principle as described in FIG. 6 to FIG. 8 described above, so that the pulse rate V _P of the follow-up pulse catches up smoothly pulse velocity V _F of the image blur correction pulse Is set to

Note that the follow-up operation here is to smoothly catch up to the desired image blur correction pulse speed after approaching the desired image blur correction pulse speed at a predetermined speed, and FIG. 7 (b)
As shown in FIG. 8 (b), the pulse speed continues to increase with the passage of time, or the pulse speed once increases and then gradually decelerates to catch up smoothly.

As another example, the speed difference between the pulse velocity V _P of the follow-up pulses and the pulse rate V _F of the image-shake correcting pulses,
The follow-up pulse may be output so that it decreases linearly and becomes zero with the elapse of a certain time before the shutter is opened.
This embodiment will be described with reference to FIG. The pulse speed of the image blur correction pulse at the start of the tracking control is V _F (t ₀ ),
Let the pulse speed of the tracking pulse be V _P (t ₀ ). Assuming that the following time is t _ST , the calculation of the pulse speed V _P (tn) is j
It can be executed multiple times. In this case, the speed difference between the pulse rate of the follow-up pulses and the pulse rate of the image blur correction pulse is initially a _{{V F (t 0) -V} P (t 0)}. When this speed difference for each one operation _{{V F (t 0) -V} P (t 0)} / j by gradually decreasing the speed differential between the j th arithmetic operations becomes 0. Based on this concept, the pulse speed V _P (tn) of the following pulse at the time of the n-th calculation is determined by the following equation.

V _P (tn) = V _F (tn) − (j−n) × {V _F (t ₀ ) −V _P (t ₀ )} / j With the above, the follow-up pulse at the end of the follow-up control pulse rate V _F of the pulse velocity V _P image-shake correcting pulse
You can catch up smoothly.

According to the present invention, in an image blur correction device for a camera in which an image blur correction lens is moved in a direction to cancel image blur by a driving force of a stepping motor, the stepping motor is moved in a self-start area before a shutter is opened. The shutter is activated immediately before the shutter opening, and the pulse speed is adjusted so as to be the speed required for image shake correction.Therefore, the image shake speed immediately after the shutter opening is large, and the pulse speed required for image shake correction is Even in the through area, the following operation enables the operation in the through area, and has the effect of increasing the speed of the image blur that can be corrected. Since the pulse speed of the tracking pulse can be determined so that switching to the image blur correction operation can be performed smoothly,
There is an effect that step-out of the stepping motor can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
FIG. 2B is a front view of a drive system of the image blur correction lens used in the above embodiment, FIG. 2B is a schematic configuration diagram of a photographing optical system including the image blur correction lens used in the above embodiment, and FIG. FIG. 4 is a diagram showing a temporal change in image displacement in the embodiment, FIG. 4 is a diagram showing a temporal change in image shake speed in the above embodiment, and FIG. 5 is a speed-torque characteristic of a stepping motor used in the embodiment. FIG. 6, FIG. 6 is an explanatory view of the principle of the above embodiment, FIGS. 7 and 8 are diagrams showing an example of calculating the pulse speed according to the above embodiment, and FIG. 9 is an explanatory view of the principle of another embodiment of the present invention. FIG. 10 is a diagram for explaining the operation of the conventional example. 1 is a sensor, 2 is a stepping motor, 3 is a control circuit, 31 is a pulse generation circuit, 32 is a judgment circuit, 33 is a conventional circuit, and 34 is a comparison circuit.

Claims (2)

(57) [Claims] 1. A sensor for detecting vibration of a camera, a stepping motor for driving an image blur correction lens included in an image taking optical system of the camera, and a sensor output inputting a predetermined time before a shutter opening, the image of the camera. A control circuit that outputs a control pulse to the stepping motor so as to correct the shake is provided.The control circuit includes a pulse generation circuit that generates an image shake correction pulse based on the sensor output, and a control circuit that generates the image shake correction when the stepping motor is started. A judgment circuit for judging whether the pulse speed of the pulse is in a controllable self-starting region or in a non-controllable through region, and the pulse speed of the image blur correction pulse is in the through region by the judgment circuit When it is determined that the pulse speed gradually changes from time to time to gradually shift from the self-starting area to the through area during the fixed time period. A tracking circuit that outputs a tracking pulse that approaches the image blur correction pulse speed, and a pulse generation circuit until the pulse speed of the tracking pulse reaches the pulse speed of the image blur correction pulse during operation of the tracking circuit. A comparison circuit that uses a tracking pulse output from the tracking circuit in place of the output image blur correction pulse as an output of the control circuit, wherein the tracking circuit includes a pulse of the image blur correction pulse at a certain time t. When the speed is V _F (t), the acceleration is α _F (t), and the pulse speed of the following pulse is V _P (t),
A circuit that determines the pulse speed V _P (t + Δt) of the following pulse at the time (t + Δt) at which the minute time Δt has elapsed as a function of V _F (t + Δt), α _F (t + Δt), and V _P (t). An image blur correction device for a camera. 2. Assuming that the remaining time of the following operation in the fixed time is t _S and the weighting coefficients are W ₁ and W ₂ , the function is V _P (t + Δt) = V _P (t) + (Δt / t _S ) _2. The image blur correction device for a camera according to claim 1, wherein the expression is expressed by: {{W ₁ V _F (t + Δt) + W ₂ α _F (t + Δt) × t _S }.