JPH0410607B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a vibration wave motor that utilizes mechanical vibration waves produced by electro-mechanical energy conversion means such as electrostrictive elements and magnetostrictive elements to improve the performance of cameras, video cameras, 8 mm cameras, etc. The present invention relates to a device for driving a lens.

As already known from Japanese Patent Application Laid-Open No. 52-29192, a vibration wave motor brings a fixed body and a moving body into frictional contact, and at least one of them is connected to the electro-mechanical energy conversion element itself or is composed of an elastic vibrating body containing an electro-mechanical energy conversion element,
By applying high-frequency electrical energy above the audible frequency to an electro-mechanical energy conversion element, mechanical vibration energy is generated to frictionally drive a moving body in one direction.

Among such vibration wave motors, the present invention particularly uses a type of vibration wave motor that generates bending vibration on the frictional contact surface between a fixed body and a movable body, and uses the traveling vibration wave to frictionally drive the movable body. .

Conventionally, attempts have been made to apply vibration wave motors to lens drives, but the following problems have arisen. That is, the conventional method for starting a vibration wave motor is to generate a traveling vibration wave using a drive start signal, similar to a DC motor or an AC motor, but this method does not have good start-up characteristics. In a vibration wave motor, a fixed body and a movable body are in strong frictional contact, and driving force is transmitted through the frictional contact. Therefore, in order to move the movable body by the traveling vibration wave at the start of lens drive, a large force exceeding the static friction force in a stopped state is required, which is the cause of poor start-up characteristics of lens drive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lens drive device using a vibration wave motor that can solve the above-mentioned problems and improve the rise characteristics at the start of lens drive.

To achieve this objective, the present invention
Generate a standing vibration wave in the mechanical energy conversion means,
The present invention is characterized in that a control means for subsequently generating a traveling vibration wave is provided, and vibration energy is applied to the fixed body of the vibration wave motor before the lens driving by the traveling vibration wave starts.

Before describing embodiments of the present invention, the driving principle of a vibration wave motor (also called a piezoelectric motor or an ultrasonic motor) will be explained with reference to FIG.

In Fig. 1, 1 is a moving body pressurized by force F, 2 is a fixed body that vibrates elastically by an electrostrictive element, the x-axis is the direction on the surface of the fixed body 2, and the z-axis is its normal. direction. When the surface of the fixed body 2 is subjected to bending vibration by the electrostrictive element, a traveling vibration wave is generated and propagates on the surface of the fixed body 2. This traveling vibrational wave is a surface wave accompanied by longitudinal waves and transverse waves, and the motion of its mass point follows an elliptical orbit. Focusing on the mass point A, it is performing an elliptical motion with a longitudinal amplitude u and a lateral amplitude w, and if the traveling direction of the surface wave is the x-axis direction, the elliptical motion is counterclockwise. This surface wave has vertices A, A', etc. for each wavelength, and its apex velocity is only the x component, and v=2πu (frequency). Therefore, when the surface of the movable body 1 is brought into frictional contact with the surface of the fixed body 2, the surface of the movable body 1 contacts only the vertices A, A'...
is driven in the direction of

The speed of the moving body 1 is proportional to the vibration frequency. Also,
Due to the frictional drive due to pressure contact, it depends not only on the longitudinal amplitude u but also on the transverse amplitude w. That is, the speed of the moving body 1 is proportional to the magnitude of the elliptical motion. Therefore, the speed of the moving body 1 is proportional to the voltage applied to the electrostrictive element.

Since the movable body 1 and the fixed body 2 are in pressurized contact even when the electrostrictive element is not vibrating, a large force is required to move the movable body 1 manually. Also,
At startup, when a traveling vibration wave is generated to change from a resting state to an operating state, the elliptical motion increases little by little due to the vibrational energy of the electrostrictive element during the transition period when it reaches a steady state, and after a certain period of time it reaches a steady state. It takes a certain amount of time for the vibration energy of the electrostrictive element to be converted from a zero state into longitudinal vibration energy and transverse vibration energy of stable traveling vibration waves.

FIG. 2 is an exploded view showing the basic configuration of the vibration wave motor used in the present invention. Hard rubber 1 is attached to the annular moving body 1 to facilitate frictional contact.
a is glued. Electrostrictive elements 3 a and 3 b forming two groups are bonded to the annular fixed body 2 . When the electrostrictive elements 3a and 3b operate independently,
The fixed body 2 is placed in a state where it resonates, that is, in a position where a standing vibration wave exists, and the standing vibration wavelength of the electrostrictive element 3a and the standing vibration wavelength of the electrostrictive element 3b are equal. , are arranged so that the phase is shifted by 90° (physical position shifted by 1 wavelength/4). The felt 4 absorbs vibrations on the surface of the fixed body 2 opposite to the frictional contact surface. The support body 5 supports the fixed body 2, the electrostrictive elements 3a and 3b, and the felt 4.

FIG. 3 is a diagram illustrating the generation of traveling vibration waves and standing vibration waves. For the sake of explanation, the electrostrictive elements 3a and 3b are not arranged as shown in FIG. 2 but are arranged alternately, but they satisfy the same conditions as above and are equivalent arrangements. The driving power source 6 supplies a voltage of V=Vo sinωt. A voltage Vo sinωt is directly applied to the electrostrictive element 3a from the driving power source 6 through a line 7, and a voltage Vo sin(ωt±π/2 ) is applied. ± of the voltage Vo sin (ωt±π/2) is switched depending on the direction in which the moving body 1 is moved. 3A to 3F show the state of vibration waves when the voltage Vo sin (ωt-π/2) is applied. A is the electrostrictive element 3a
Figure 3 shows a state in which the standing vibration wave 10 is generated only by the electrostrictive element 3b, and a state in which the standing vibration wave 11 with a phase delay of 90° is generated only by the electrostrictive element 3b. H~N are two electrostrictive elements 3a and 3b
This shows a state in which the traveling vibration waves 12 are generated by operating the two at the same time. C is time t=0+2nπ/ω,
D is time t=π/2ω+2nπ/ω, E is time t=
π/ω+2nπ/ω, F indicates the phase of the traveling vibration wave 12 of 3π/2ω+2nπ/ω, respectively. The traveling vibration wave 12 travels to the right in FIG. 3, but any mass point on the frictional contact surface of the fixed body 2 performs an elliptical motion in a counterclockwise direction. Therefore, the moving body 1 moves to the left.

When either of the standing vibration waves 10 and 11 of A and B are generated, the mass points other than the nodes on the frictional contact surface of the fixed body 2 exhibit only transverse vibration, that is, vertical movement in FIG. 3. Therefore, moving body 1 and fixed body 2
The frictional contact with the material is not a static friction state but a dynamic friction state, and the friction coefficient is small and the contact area is also small. Therefore, when moving the movable body 1 manually, it can be moved with a small force. Also,
Since vibration energy is stored in the fixed body 2, when the traveling vibration wave 14 is generated thereafter, its rise becomes faster.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 4 shows the structure of a zoom lens driving device according to an embodiment of the present invention. Components similar to those in FIG. 2 are designated by the same reference numerals.

At the rear end of the fixed barrel 13 of the lens barrel, a mounting member 14 such as a bayonet or screw mount for mounting on the camera is provided. Fixed body 13
A straight groove 13a is provided in the optical axis direction. The lens holding barrels 15 and 16 are fitted inside the fixed barrel 13, and hold a lens optical system 17 that performs a magnification change function and a correction function for aberrations accompanying the magnification change. Pins 15a, 16a are installed in each lens holding barrel 15, 16, and these pins 15a, 16a are inserted into the straight groove 13a.
It penetrates through and fits into cam grooves 18a and 18b of a cam cylinder 18 fitted on the outer periphery of the fixed cylinder 13. The lens holding cylinder 19 holds a focusing lens optical system 20,
A threaded portion 19a screwed onto the outer periphery of the lens holding barrel 15
has. The cylindrical flange 19b is connected to the distance adjustment ring 2.
It is fitted into a rectilinear groove 21a formed on the inner circumferential surface of the lens 1 parallel to the optical axis direction. A grip portion 21b is provided at the tip of the distance adjustment ring 21. The friction contact portion 21c of the distance adjustment ring 21 corresponds to the movable body 1 in FIG. 2, and is pressed against the fixed body 2 by a ring leaf spring 22. The base cylinder 23 is integrally fixed to the fixed body 13 with screws (not shown), and supports the fixed body 2, the electrostrictive elements 3a and 3b, and the felt 4.

An outer cylinder 24 is screwed to the base cylinder 23.
A first ring 25 and a second ring 26 for bearings are attached to the inside of the bearing. That is, the first ring 25 is pressed against the friction contact portion 21c of the distance adjustment ring 21 by the ring leaf spring 22 via the bearing ball 27.
The second ring 26 is attached by being screwed into the inner circumferential surface of the outer cylinder 24, and a V-shaped circumferential groove is formed at the joint between the first ring 25 and the second ring 26. A bearing ball 28 is held between the groove and a substantially U-shaped circumferential groove formed on the outer peripheral surface of the distance adjustment ring 21. As a result, the distance adjustment ring 21
is rotatably attached to the outer cylinder 24, and
Rotatable frictional contact of the frictional contact portion 21c with the fixed body 2 is ensured.

The code plate 29 has comb-shaped electrodes,
The distance adjustment ring 2 is attached to the inner wall surface of the outer cylinder 24.
By sliding the slider 30 fixed to 1 on the comb-shaped electrode, the distance adjusting ring 21 is rotated, that is, the focusing lens optical system 20 is moved by a number of pulses corresponding to the amount of movement. A quantity monitor signal is generated.
An electric manual changeover switch 31 is provided on the outer cylinder 24, and its contact piece 32 is mounted on the base cylinder 23. The operating pin 33 is attached to the cam cylinder 18,
The cam cylinder 18 is rotated by turning it around the optical axis from the outside of the base cylinder 23. When the cam cylinder 18 rotates, the cam grooves 18a and 18b engage the pins 15a and 16a.
Since the lenses are moved along the rectilinear groove 13a, the lens holding cylinders 15 and 16 move in the optical axis direction and perform a magnification change action and an aberration correction action.

FIG. 5 shows a circuit of one embodiment of the present invention. The autofocus light receiver 34 is connected to the distance measuring circuit 35 using, for example, a charge-coupled device. Distance measurement circuit 35
Output terminal A outputs a high-level drive signal or a low-level stop signal to the vibration wave motor, and output terminal B outputs a high-level near-side drive direction signal or a low-level infinity-side drive direction signal. In addition, an electric manual switching circuit 36 is connected to the input terminal C in order to change the focusing range width of the distance measuring circuit 35 between electric operation and manual operation.
A switching signal is input from the monitor signal generation circuit 38 to the chattering absorption circuit 39 to the input terminal D.
A movement amount monitor signal is input through the . The switching signal of the electric manual switching circuit 36 is also sent to the OR gates 40 and 52. The electric manual switching circuit 36 consists of an electric manual switching switch 31 and a resistor 41, and is supplied with a power supply voltage Vs in conjunction with turning on a power switch (not shown), such as by the first stroke of a camera release button. Electric manual changeover switch 31
is turned on when powered and turned off when powered. The monitor signal generation circuit 38 includes a code plate 29,
A resistor 42 connected to the slider 30 and a constant voltage power supply
Consists of. The pulse generation circuit 43 includes an oscillator 44, frequency dividers 45 and 46 with a frequency division ratio of 1/2, and an inverter 4.
7, the pulses with a 90° phase difference are passed to the frequency divider 4.
Output from 5,46. The frequency divider 48 is connected to the oscillator 4
The output pulse of No. 4 is frequency-divided to have a period longer than the period of the pulses of the frequency dividers 45 and 46. The lens drive start signal generation circuit 49 includes a lens drive start switch 50 and a resistor 51 connected to a power source. The lens drive start switch 50 is a switch that is turned on after a predetermined time period after the first stroke of the release button, or a switch that is turned on in conjunction with the second stroke when the release button performs a three-step stroke, or is a separate switch configuration that has nothing to do with the release button. 40 and 52 are OR gates, 53 to 56 are AND gates, 57 is an inverter, and 58 is an exclusive OR gate. The exclusive OR gate 58 is connected to the output terminal B of the distance measuring circuit 35.
When the input from the frequency divider 46 is at a high level, the phase of the pulse from the frequency divider 46 is advanced by 90 degrees with respect to the pulse from the frequency divider 45, and when the input from the frequency divider 46 is at a low level, the phase is delayed by 90 degrees.

The drive control circuit 59 is a circuit that controls the drive of the electrostrictive elements 3a and 3b, and includes two push-pull circuits 60 and 6 consisting of transistors, resistors, and inverters.
1. It is composed of switching transistors 62 and 63 and a resistor 64. Similar to the electric manual switching circuit 36, the drive control circuit 59 is supplied with the power supply voltage Vs in conjunction with turning on of a power switch (not shown) by the first stroke of the release button or the like.

Next, the operation of the embodiment shown in FIGS. 4 and 5 will be explained. When the first stroke of the release button is pressed and a power switch (not shown) is turned on for photographing operation of the camera, the power supply voltage Vs is supplied to the electric manual switching circuit 36 and the drive control circuit 59. At the same time, power is supplied to all circuits including the light receiver 34 and the ranging circuit 35.
The pulse generating circuit 43 and the frequency divider 48 start operating.

When the electric manual changeover switch 31 is turned off and manual drive is selected, the OR gate 40 outputs a high level signal regardless of whether the lens drive start switch 50 is turned on or off, so the AND gates 53 and 54 are turned off. Open. Moreover, regardless of the signal level of the output terminal A of the distance measuring circuit 35,
Since the OR gate 52 outputs a high level signal, the AND gates 55 and 56 are opened.

At the same time, the photometry calculation operation is started, and the distance measurement circuit 3
5 starts autofocus operation. The light receiver 34 receives the reflected light from the subject, and the distance measuring circuit 35 uses the subject information from the light receiver 34 to detect a focusing error based on a known contrast detection method, shift detection method, etc., and calculates the amount of lens drive and Calculate the driving direction. The lens driving amount is preset in a counter (not shown) in the distance measuring circuit 35. A high level drive signal is output from the output terminal A, and if it is assumed that the subject is on the close side, a high level close side drive direction signal is output from the output terminal B.

While the output of the frequency divider 48 is at a high level, the output of the AND gate 53 is at a low level, and the output of the AND gate 55 is at a high level.
Switching transistor 62 is turned on.
On the other hand, the output of the AND gate 54 is at high level,
Since the output of AND gate 56 becomes low level, switching transistor 63 remains off. Therefore, the electrostrictive element 3b is in a state of being disconnected from the power supply, and the push-pull circuit 6 controlled by the pulses of the frequency divider 46 is applied only to the electrostrictive element 3a.
0 supplies high frequency power. Therefore, a standing vibration wave 10 is generated in the fixed body 2. Conversely, while the output of the frequency divider 48 is at a low level, the output of the AND gate 56 is at a high level, so that only the switching transistor 63 is turned on, and high frequency power is supplied only to the electrostrictive element 3b. As a result, a standing vibration wave 11 is generated in the fixed body 2. Standing vibration wave 1
By 0 or 11, the friction torque between the fixed body 2 and the distance adjustment ring 21 becomes small. Therefore, by holding the grip portion 21b slightly exposed from the tip of the outer cylinder 24 and turning the distance adjustment ring 21, it will turn lightly with a small manual torque, and the lens holding cylinder 19 will be moved in the optical axis direction.

The reason why the electrostrictive elements 3a and 3b are switched to alternately generate the standing vibration waves 10 and 11 is to disperse partial wear and fatigue of the friction contact portion 21c of the distance adjustment ring 21. . If only the electrostrictive element 3a is used, the antinode of the standing vibration wave 10 will be determined by the physical position of the electrostrictive element 3a. Fatigue occurs.

When the electric manual selector switch 31 is turned on and electric drive is selected, when the first stroke of the release button is pressed and the power switch (not shown) is turned on, when the camera is not in focus,
Since a high level signal is output from the output terminal A of the distance measuring circuit 35, the output of the OR gate 52 becomes high level. In addition, the lens drive start switch 5
The output of the OR gate 40 remains at a high level until 0 turns on. Therefore, the electrostrictive elements 3a and 3b alternately generate standing vibration waves 10 and 11 by the same operation as during manual driving, and the fixed body 2 stores vibration energy and prepares for lens driving. . After a predetermined time period has elapsed since the first stroke of the release button, or in conjunction with the second stroke (in the case of a three-step stroke), or by another operation unrelated to the release button, the lens drive start switch 50 is activated. is turned on and a low-level lens drive start signal is output from the lens drive start signal generation circuit 49, the output of the OR gate 40 becomes low level, so the outputs of AND gates 53 and 54 both become low level, The outputs of AND gates 55 and 56 both go high, turning on switching transistors 62 and 63. Therefore, the power supply voltage Vs is applied to the push-pull circuits 60 and 61.
is applied. The pulse generating circuit 43 is in operation, and the pulses from the frequency divider 45 directly control the push-pull circuit 61, so that high frequency power is applied to the electrostrictive element 3b. If the subject is close,
Output terminal B of the distance measuring circuit 35 outputs a high-level nearby drive direction signal. Therefore, the frequency divider 46
The pulse is inverted by the exclusive OR gate 58 and has a phase lead of 90° with respect to the pulse of the frequency divider 45, and controls the push-pull circuit 60, so that the electrostrictive element 3a is given a 90° phase lead to the pulse of the frequency divider 45. Advanced high frequency power is provided. As a result, a traveling vibration wave 12 is generated in the fixed body 2, and a steady state is immediately reached, and the distance adjustment ring 21 is rotated in the focusing direction. The lens holding cylinder 19 is integrated with the distance adjustment ring 21.
rotates while being screwed together with the lens holding cylinder 15, so it moves in the drawing direction and reaches the in-focus area.

As the distance adjustment ring 21 rotates, the slider 30 slides on the code plate 29 and generates a movement amount monitor signal with a pulse number corresponding to the movement amount of the lens. This movement amount monitor signal is input to the input terminal D of the distance measuring circuit 35.
and subtract the lens drive amount registered in the counter. When the value of the counter reaches zero, a low level stop signal is output from output terminal A, and the outputs of the OR gate 40 and AND gates 55 and 56 are inverted to low level, so the switching transistors 62 and 63 are turned off and the current is turned off. Strain element 3a,
3b is then disconnected from the power source, and the driving of the distance adjustment ring 21 is stopped. Here again, distance measurement is performed by the light receiver 34 and the distance measuring circuit 5, and if the focusing error is within the in-focus range, an in-focus display is performed. When the focus area is not reached, the lens is driven again in the same manner as described above.

When the subject is at infinity, the distance measuring circuit 3
Since the output terminal B of 5 outputs a low-level infinity side drive direction signal, the exclusive OR gate 58 passes the pulse from the frequency divider 46 as it is, and assumes that the pulse is delayed by 90 degrees in phase from the pulse from the frequency divider 45. do. Therefore, the electrostrictive elements 3a and 3b generate traveling vibration waves that travel in opposite directions, the distance adjustment ring 21 rotates in the opposite direction, and the lens holding cylinder 19 is moved in the retracting direction.

When the focus state is reached as described above, the release button is further depressed to start a series of photographing sequences and perform exposure.

According to this embodiment, the distance adjustment ring 21 can be moved lightly during manual focus adjustment, so manual operability can be improved. Furthermore, the distance adjustment ring 21 can be moved with good responsiveness during automatic focus adjustment.

In the illustrated embodiment, the electrostrictive elements 3a and 3b correspond to the electro-mechanical energy conversion means of the present invention, and OR gates 40 and 52, AND gates 53 to 56,
Switching transistors 62 and 63 correspond to control means.

In the illustrated embodiment, a plurality of electrostrictive elements 3a and 3b are used, but one electrostrictive element may be polarized into a plurality of elements. Further, the electrostrictive element may be provided on the friction contact portion 21c of the distance adjustment ring 21, or may be provided on both the fixed body 2 and the friction contact portion 21c. Furthermore, the fixed body 2 itself may be composed of an electrostrictive element. The optimal frequency of the vibration waves produced by the electrostrictive element is in the ultrasonic range.

Focus error detection is not limited to an optical method, but may also be an ultrasonic method.

The present invention is suitable not only for use in lens focusing drive but also for zooming drive.

As explained above, according to the present invention, electricity
Generate a standing vibration wave in the mechanical energy conversion means,
After that, a control means for generating a traveling vibration wave was provided, and vibration energy was applied to the fixed body of the vibration wave motor before the lens drive by the traveling vibration wave started, so that the rise characteristics at the start of lens drive could be controlled. You can make it better.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the driving principle of the vibration wave motor, Figure 2 is an exploded view showing the basic configuration of the vibration wave motor used in the present invention, and Figure 3 is the progression in the vibration wave motor shown in Figure 2. FIG. 4 is a cross-sectional view showing an embodiment of the present invention, and FIG. 5 is a circuit diagram for explaining the generation of vibration waves and standing vibration waves. 1...Moving body, 2...Fixed body, 3a, 3b...
Electrostrictive element, 10, 11... Standing vibration wave, 12...
Traveling vibration wave, 13... Fixed cylinder, 15, 16... Lens holding cylinder, 19... Lens holding cylinder, 20... Focusing lens optical system, 21... Distance adjustment ring, 23...
... Base tube, 24 ... Outer cylinder, 31 ... Electric manual changeover switch, 34 ... Light receiver, 35 ... Distance measuring circuit, 3
6...Electric manual switching circuit, 40...OR gate,
43... Pulse generation circuit, 45, 46... Frequency divider, 48... Frequency divider, 49... Lens drive start signal generation circuit, 50... Lens drive start switch,
52...OR gate, 53-56...AND gate, 58...Exclusive OR gate, 59...Drive control circuit, 60, 61...Push-pull circuit, 6
2,63...Switching transistor.

Claims (1)

[Claims] 1. A fixed body, a moving body that makes frictional contact with the fixed body,
A vibration wave motor comprising an electro-mechanical energy conversion means that is included in at least one of a fixed body and a moving body, or forms the fixed body itself, and generates a traveling vibration wave that drives the moving body. The lens driving device for driving a lens by the movable body is a vibration wave motor, characterized in that the vibration wave motor is provided with a control means for causing the electro-mechanical energy conversion means to generate a standing vibration wave and then generating the traveling vibration wave. A lens drive device using