JP2682665B2 - Anti-vibration device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration control device for preventing an optical device such as a camera from vibrating due to camera shake or the like and causing an image to be blurred on an image forming surface. .

(Prior Art) As a vibration isolation device as described above, for example, the present applicant has already
Examples include those filed as US ser No. 085,731. This apparatus displaces a correction optical system for correcting image blur in a direction that cancels image blur on an image forming surface in a plane substantially perpendicular to a photographing optical axis, that is, in a direction opposite to the direction of image blur. This is to prevent the image on the image forming plane from being blurred. Therefore, in the above apparatus, two parallelogram links each having one degree of freedom are connected in series so that the degrees of freedom are perpendicular to each other in a plane substantially perpendicular to the photographing optical axis. The correction optical system is held at the tip of the correction optical system so that the correction optical system can be displaced in the direction substantially opposite to the direction in which the image on the imaging plane is blurred in a plane substantially perpendicular to the photographing optical axis. At the same time, the parallelogram frames are elastically pressed against the respective cams, and the cams are driven by a motor so as to displace the correction optical system in the direction opposite to the direction of the blurring, whereby the image blurring on the image forming plane is suppressed. I try to prevent it.

In order to correct the image blur in this way, it is necessary to displace the correction optical system, but the amount that can be displaced is naturally limited. For example, in the case of the above device, the shape of the cam is spiral. Since it is a cam, if the cam moves to a position beyond the end position, the correction optical system will return to the start position of the cam, and the displacement direction of the correction optical system will also be the direction of blurring, so rather it will be rather large. There was a problem of causing image blur.

[Object of the invention]

The present invention has been made in view of the above circumstances, and it is possible to prevent the correction optical means for preventing image blur from causing a large blur even when trying to displace to a position beyond the displaceable zone. It is intended to provide a shaking device.

To this end, the present invention provides correction optical means for preventing image blur, drive means for driving the correction optical means, and response to the correction optical means approaching a displacement limit. It is an object of the present invention to provide an anti-vibration device provided with speed reducing means for reducing the driving speed of the driving means.

Further, for the above-mentioned object, the present invention responds to correction optical means for preventing image blurring, drive means for driving the correction optical means, and response of the correction optical means to a displacement limit. A control means for controlling the drive of the drive means so that the correction optical means is displaced to the center of the displaceable zone; and a prohibition means for prohibiting the operation of the control means in response to the start of exposure. It is intended to provide a vibration isolation device.

(Example) Hereinafter, the Example of this invention is described based on drawing.

The specifications of the anti-vibration device shown in the following examples are the focal length
Experiments were carried out on a camera equipped with a telephoto lens of 300 mm and an aperture of f2.8.
Also, an example is determined based on the measurement result of the angular velocity. Needless to say, the method of the present invention can be similarly applied to optical devices other than the above.

This experiment was conducted by selecting appropriate men and women. According to the experimental results, the frequency band of blurring acting on the camera was between 1 Hz and 10 to 12 Hz. The average amplitude of image displacement on the film surface, which is the image plane, during the exposure time 1/60 second is
It is 60 to 80 μm, and the maximum amplitude is 200 to 260 μm. This maximum amplitude is the time required to move the shutter curtain of the camera.
24ms total time, which is 7ms plus 1/60 second exposure time
In consideration of the time required to complete exposure of the entire screen, that is, 300 μm may be reached.

In order to effectively prevent the image blur with respect to the blur having the above characteristics, the residual amplitude during the exposure time of 1160 seconds needs to be suppressed within 20 μm.

The maximum linear velocity that the correction optical system should guarantee was 20 mm / s. As a result, the exposure time is 1/60 seconds, that is, the total exposure time of 24 ms, the maximum displacement of the correction optical system that can perform correction is about 0.5 mm
Can be determined.

FIG. 1 shows a configuration of an optical compensator which is a simplified view of the above-described vibration damping device by the applicant for the present embodiment. It is a one-dimensional element for optically compensating for angular displacement of shake. It is shown.

In FIG. 1, reference numeral 2 is a correction optical system for correcting image blur, and 1 is a movable part for holding the correction optical system 2, which is one-dimensional in a plane perpendicular to the photographing optical axis by a guide device 3. Will be guided. Reference numeral 4 denotes a cam which is driven by the motor 5 to move the movable section 1 and is fixed to an output shaft of the motor 5. 6
Is a pressurizing spring that presses the movable part 1 along the direction guided by the guide device 3, and the roller 7 provided in the movable part 1 is always brought into contact with the cam 4 so that the movable part 1 passes through the roller 7. The cam 4 can be driven.

Although not shown in FIG. 1, the same elements as the illustrated mechanism for moving the correction optical system 2 in a direction orthogonal to the illustrated mechanism in a plane orthogonal to the photographing optical axis are actually used. A mechanism having a second degree of freedom is provided.
As a result, the correction optical system 2 moves in a plane perpendicular to the photographing optical axis,
It can move freely in a direction to prevent image blur.

With the above configuration, when the camera shakes, the direction and amount of the shake is detected by the control structure described later, and the cam 4 causes the motor 4 to shoot the correction optical system 2 according to the direction and the amount of the shake. The image blurring on the image plane is prevented by displacing the image plane in the direction perpendicular to the axis, that is, the direction opposite to the image blur direction on the image plane.

Hereinafter, a control configuration for controlling the operation of the above mechanism will be described, but for the sake of simplicity, in the following description, the first configuration shown in FIG.
Only the mechanism having the second degree of freedom will be described, and the mechanism having the second degree of freedom (not shown) is completely the same as that, and will not be described.

FIG. 2a shows the input / output relationship to the optical compensator S of FIG. 1, in which the input voltage Umot is input to the motor 5 of FIG. 1 and the speed signal Vlens of the correction optical system 2 is output as an output signal.
Is output.

FIG. 2b is a signal representation of all electrical and mechanical parameters of the device of FIG. From this symbolic representation, the transfer function of the device of FIG. 1 is analyzed. This FIG. 2b includes four parts relating to the applied pressure Fconst of the motor 5, the cam 4, the movable part 1 and the applied spring 6. The electric part of the DC motor 5 is the resistance R, the inductance L, and the electromotive force E of the motor, and the mechanical part is the inertia I and the friction ρ.
including. The cam 4 is symbolized as a torque-force conversion coefficient δ. The movable part 1 represents the mass m, the spring constant κ of the pressurizing spring, the dynamic friction λ of the spring, the pressurizing force of the pressurizing spring b, and the weight Fconst.
Is symbolized by.

By analyzing these various parameters, the transfer function S relating to the speed of the correction optical system 2 according to the voltage Umot applied to the DC motor 5 and the force Fcont can be obtained.

The transfer function of the symbolic model in FIG. 2 is: M = Ψ · i E = Ψ · ω Umot-E = Ri + sLi Umot = (R + sL) i + Ψω for the electric part of the motor 5, where M is the output torque and Ψ is Torque coefficient, i is current,
ω is the angular velocity reading of the output shaft of the motor 5, and S is the Laplace operator.

As for the mechanical part of the motor 5, M = Mi + Mρ + Mδ = sIw + ρ · ω + δF _δ where Mi and Mρ are inertia I, internal loss torque due to friction ρ, Mg is the output torque of the motor 5, and F _δ is the driving force acting on the correction optical system 2. Represents

Since the coupling of the cam 4 and the movable portion 1 is assumed to be rigid, the relationship between the rotating system (motor 5) and the translation system (correction optical system 2) is However, Ylens and α represent the position and acceleration of the movable part 1, respectively. Regarding the movable part 1, F _δ = F _m + F _κ + F _λ + F _const = (s ² m + sλ + κ) Y _lens + F _const, where F _m , F _κ , and F _λ are the mass m of the movable part 1, the rigidity κ,
It represents each force corresponding to the dynamic friction λ.

About the whole I _tot = I + mδ ² ρ _tot = ρ + λδ ² However, the subscript tot represents the total viewed from the motor output shaft.

Assuming that the weight of the movable part 1 and the pressurization force Fconst of the pressurization spring 6 are constant values, these can be canceled by applying a fixed voltage equal to the voltage Uconst shown in the following formula to the motor 5: In addition to the Fconst cancellation, the following transfer function S (s), which shows the dynamic characteristics of the optical compensator S, can be simplified in the vibration-effective frequency range as follows: FIG. 4a shows the dynamic properties of this simplified model, where the parameters P _s1 , P _s2 and Sconst are defined as follows: As can be seen from FIG. 4a, the voltage Umot applied to the motor 5 is basically proportional to the displacement of the movable part 1 in the low frequency range, and is proportional to the acceleration of the movable part 1 in the high frequency range. Between these two frequencies, the voltage Umot is
Proportional to the speed of.

By expanding the frequency range in which this voltage Umot is proportional to the speed of the movable part 1 to the frequency interval of 1 to 10 (Hz) required for image blur prevention, an automatic control system with speed as shown in Fig. 3 is realized. can do. Hereinafter, a more detailed description will be given with reference to the block diagram of FIG.

In FIG. 3, Acc is an accelerometer, which detects a blurring state such as a camera shake acting on a camera when determining a composition by looking through a viewfinder or when exposing a film, and this is proportional to the angular acceleration. Output as a signal γ. Next this signal γ
The acceleration - is integrated by the speed converter a / v, is input is converted into a signal U _V of the angular velocity characteristic to the signal attenuator V _F. In the signal attenuator V _F, the cam 4 as described later so as to weaken the signal U _V closer to the end position, the motor 5
Moves the cam to a position beyond the end position,
This prevents the correction optical system 2 from causing a large image blur.

The circuits after the signal attenuator V _F constitute a closed loop,
The output of the from the signal attenuator V _F is sent to an electronic compensation circuit C.
In the electronic compensating circuit C, a frequency band in which the speed Vlens of the movable part 1 driven by the motor 5 is proportional to the voltage Umot supplied to the motor 5 is necessary for image blur prevention as an ideal transfer function shown in FIG. 4b. It works by selecting and expanding the frequency band. That is, the electronic compensation circuit C is the sixth
The zeros of the transfer function correspond to the poles P _s1 and P _s2 of the optical compensator S as shown. The details of the electronic compensation circuit C are shown in FIG.

As shown in FIG. 3, the supply voltage Umot from the voltage compensating circuit C is sent to the motor 5 of the optical compensator S, and the motor 5
The cam 4 displaces the correction optical system 2 in a direction perpendicular to the imaging optical axis in a direction opposite to the direction of the image blur on the image plane, thereby preventing image blur on the image plane.

On the other hand, the displacement of the correction optical system 2 is detected as the position Ylens of the movable portion 1 by the block M that executes high-precision differential measurement. The block M differentiates this detection result and outputs a signal Umes proportional to the speed Vlens of the movable portion 1. This signal Umes is sent to the PID filter and amplifies the error signal Udiff between the shake velocity signal Uv acting on the camera and the fast feed signal Umes of the movable part 1 to obtain the signal Vcorr, which is in front of the electronic compensation circuit C. Re-injected into.

This closed loop control plays the role of optically stabilizing the vibration acting on the camera. In other words, the control minimizes the positional deviation caused by the error between the vibration velocity Ωcamera acting on the camera and the velocity Vlens of the correction optical system 2 fixed to the movable portion 1, that is, the residual image blur amount. The purpose is to control.

That is, the closed loop control functions based on speed and generates a speed correction signal until the speed error is as small as possible. Instead of the PID filter proposed here, digital control or automatic position control using a regulator for state variables or the like can be used.

FIG. 7 shows a circuit diagram of the PID filter. The voltage Udiff, which is the difference characteristic between the speed reading of the movable part 1 and the speed of blurring acting on the camera, is amplified by this filter and becomes the corrected voltage Ucorr. In FIG. 7, the switch IN is the cam 4
When the centering operation is performed to restore the initial position, which is the neutral position, the logic signal cent output for a fixed time controls the upward opening and closing. This centering operation will be described later. This switch IN is kept open until the centering operation is completed.

FIG. 8 shows the characteristics of the circuit of FIG. 7 with respect to the frequency f.

Returning to FIG. 3, the block M further outputs a voltage signal Upos proportional to the position Ylens of the movable portion 1. Signal Upo
s shows a detailed electric circuit in FIG. It is sent to the centering module CE to form a second closed loop for the centering operation. As shown in FIG. 9, the signal Upos sent to the centering module CE is input to the differential amplifier A ₁ , and its output is the signal by the logic signal cent output in the same centering operation as described above.
Cent is sampled at a high level and is input to a sample hold circuit S + H that holds at the falling edge of the signal cent. Due to this logic signal cent, the module CE injects a voltage Uconst, which is a function of the signal Upos representing the position of the movable part 1 during the centering operation, in front of the electronic compensation circuit C, as shown in FIG. The correction optical system 2 is moved to the center of the displaceable zone by driving the motor 5 so as to return it to the neutral position. In this centering operation, when the correction optical system 2 is near the limit of the displaceable zone, the correction optical system 2 hits the limit of the displaceable zone during the image stabilization operation, and the image stabilization operation cannot be performed. The purpose of this centering operation is to initialize the correction optical system 2 to the center of the displaceable zone so that the correction optical system 2 does not hit the limit of the displaceable zone.

FIG. 10 shows the characteristics of the module CE. When the position of the correction optical system 2 is outside the range of the threshold values −Uthres to Uthres, the correction optical system 2 is moved in the center direction of the displaceable range at a constant speed. A constant voltage Umax or −Umax for moving the motor 5
Is applied. On the other hand, the correction optical system 2 uses the threshold value −Uthres
When it is within the range of Uthres, the voltage applied to the motor 5 is corrected. The position in the middle of the zone where the correction optical system 2 can be displaced (Upos = O)
Then, the voltage is changed from the constant voltage Umax or −Umax toward the balanced voltage Ubal so as to become the balanced voltage Ubal. This equilibrium voltage Ubal is applied to the moving part 1 of the motor 5 at the neutral position of the cam 4.
And the force Fcomst generated by the pressure of the spring 6 that urges the movable portion 1 to the cam 4 is in equilibrium with the force to generate a torque that stops at that position.

In FIG. 9, when the movable part 1 completes the centering operation, the logic signal cent becomes low level, and the sample hold circuit S + H fixes the output voltage Ucomst at a value near the equilibrium voltage Ubal, and the speed of the movable part 1 is automatically adjusted. Control becomes ready. That is, from this time point, the correction optical system 1 can be moved in the plane perpendicular to the photographing optical axis in the directions of the two axes that are perpendicular to each other for blur correction. Returning to FIG. 3, the signal Upos, which is output from the measurement block M and is proportional to the position Ylene of the movable portion 1, is transmitted to the movement range limiting block L as well as the centering block CE. The movement range limiting block L includes two different functional blocks, one of which reduces the drive speed of the motor 5 as the movable portion 1 approaches the limit of the displaceable zone, and the cam 4 exceeds the limit position. There is a signal attenuator V _F that prevents it from trying to move to position, and another is a filter P _F , which performs the same centering operation as above, but slowly and continuously until the shutter is in the open position. By moving the cam 4 toward the neutral position at all times, it is possible to prevent the cam 4 from stopping at the limit position due to the action of the attenuator V _F and no longer performing the anti-vibration operation, so that the amplitude at the time of aiming is large. Excludes the effect of slow swells and enables long-term anti-vibration. Also, the filter
P _F also acts a large shake the camera and the like change the direction of the camera when framing before shooting, when you start the actually captured as the correction optical system 2 has returned to the middle of the displaceable zone This prevents the correction optical system 2 from hitting the limit of the displaceable zone and becoming unable to perform the image stabilization operation, and also enables the image stabilization operation against shake of high frequency even during the slow panning period. ing.

The position of the movable portion 1 Ylene to these signal attenuator V _F
Signal Upos proportional to and the acceleration-speed converter a /
Input a signal U _V having a characteristic corresponding to the speed of blurring acting on the camera, which is output from v, and change the voltage supplied to drive the motor 5 as the movable portion 1 approaches the limit of the displaceable zone. Reduce.

FIG. 11 shows the configuration of the signal attenuator V _F. FIG. 12, corresponding to the signal Upos representing the position of the movable portion 1 which is output by block M, which shows the control signal Vcontrol of the attenuator V _F.

The gain G of the output signal of the amplifier A _{2 in} FIG. 11 with respect to the input signal U _V is a position function of the movable part 1 as shown in FIG. In the area of the maximum gain, there is an area where a stabilized image is obtained, and at the point of the minimum gain, the image is not stabilized. The middle of it corresponds to a region that, if too large, makes the photographer notice that the blur is acting on the camera. The characteristics of this attenuator V _F can be modified by changing the transition process between maximum gain and minimum gain.

On the other hand, the filter P _F enables the image stabilization during aiming by eliminating the effect of low-frequency shake for a long time when deciding the composition through the viewfinder as described above, and the camera's vibration control while continuing the image stabilization operation. Since it is for enabling direction change, a first-order low-pass filter that extracts low frequency HU acting during aiming and direction change of the camera is used,
Its output forms a closed loop which modifies the voltage supplied to the motor 5 so that the cam 4 is directed towards the neutral position.

On the other hand, since this re-centering operation impairs the anti-vibration action in the low frequency range, this re-centering operation is prohibited during photography so that the most accurate anti-vibration effect can be guaranteed. That is, as soon as the shutter opening signal SH output in response to the start of shooting starts shooting, the switch INT is opened, the output of the filter P _F is prohibited, and the re-centering operation is not performed.

The filter P _F may be a first order low pass filter, as described above, but its time constant must be selected to make the re-centering operation effective when the cam 4 approaches its limit. On the contrary, when the cam 4 is in the neutral position, the filter P _F should not deteriorate the image stabilizing performance. It should be noted that the one proposed here is only one of several directions for slowly re-centering the correction optics 2 as follows: -Different but always continuous filters. -A filter that operates only when the cam approaches the limit-A filter that operates periodically [Effect of the invention] As described above, according to the present invention, the correction optical means for preventing image blur exceeds the displaceable zone. It becomes possible to provide a vibration control device which does not cause a large image blur even if it is displaced to a desired position, and its effectiveness is extremely high.

[Brief description of the drawings]

FIG. 1 is a diagram showing a driving mechanism of an optical compensator according to the present invention in a very simplified one-dimensional manner, and FIGS. 2a and 2b are mechanical and electrical parameters that act on the first optical compensator. FIG. 3 is a block diagram showing a control system of the optical compensator shown in FIG. 1, FIG. 4a is a graph showing frequency characteristics of the optical compensator S, FIG.
FIG. 4b is a graph showing frequency characteristics of the electronic compensation module C of the circuit of FIG. 3, FIG. 5 is a specific circuit diagram of the electronic compensation module C of the circuit of FIG. 3, and FIG. FIG. 7 is a graph showing the frequency characteristics of the circuit shown in FIG. 7, FIG. 7 is a specific circuit diagram of the PID filter shown in FIG. 3, and FIG. 8 is a graph showing the frequency characteristics of the circuit shown in FIG. The figure shows the centering module CE of the circuit diagram in Fig. 3.
10 is a graph showing the input / output characteristics of the circuit shown in FIG. 9, and FIG. 11 is a circuit diagram showing the signal attenuator V _F of the circuit shown in FIG. Fig. 13 and Fig. 13 are graphs showing input / output characteristics of the circuit of Fig. 11, explanation of symbols of main parts 1 ... Movable part, 2 ... Complementary optical system, 4 ... Cam, 5 ... Motor, 6 ... … Pressurizing spring, Acc …… Accelerometer a / v …… Acceleration-speed converter, C …… Electronic compensation circuit, S …… Optical compensator, M …… Measuring block, PID …… PID filter, CE …… Centering Module, V _F …… Signal attenuator, P _F …… Filter

Claims (2)

(57) [Claims] 1. A correction optical means for preventing image blur, a drive means for driving the correction optical means, and a drive of the drive means in response to the correction optical means approaching a displacement limit. An anti-vibration device comprising: a speed reducing means for reducing the speed. 2. A correcting optical means for preventing image blur, a driving means for driving the correcting optical means, and the correcting optical means in response to the correcting optical means approaching a displacement limit. A control means for controlling the drive of the drive means so as to be displaced to the center of the displaceable zone; and a prohibition means for prohibiting the action of the control means in response to the start of exposure. Anti-vibration device.