Driving apparatus

Details Driving apparatus Driving apparatus

1999-09-10

2001-02-13

Epps, Georgia (Department: 2873)

Optical: systems and elements

Lens

With support

C359S814000, C359S823000

Reexamination Certificate

active

06188530

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based on Patent Application No. HEI 10-258161 filed in Japan, the content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for driving a member in a predetermined direction, and specifically relates to an apparatus for driving an optical member such as a lens element and the like along an optical axis.
2. Description of the Related Art
In conventional lens devices, a rotation motor is used as a lens drive actuator. For example, as shown in
FIG. 1
, a widely used method provides a cam pin
2
a
that protrudes from a lens frame
2
which holds a lens
1
, and is inserted in a channel
4
a
provided on a cam ring
4
and is inserted in a rectilinear channel (not illustrated) provided on the stationary barrel
3
, such that the rotation of the rotation motor
5
is transmitted to the cam ring
4
via, a gear train
6
or the like, and rectilinearly drives the lens
1
by means of the rotation of the cam ring
4
relative to the stationary barrel
3
.
A lens device has been proposed which uses a piezoelectric actuator
8
as a lens driving actuator, as shown in
FIGS. 2A and 2B
. The piezoelectric actuator
8
comprises a stationary member
8
a
and a drive rod
8
b
respectively connected to each end in the expansion/contraction direction of a piezoelectric element
8
c
which expands/contracts when a voltage of a predetermined waveform is applied thereto, and a slider
8
x
having a friction member
8
t
friction bonded to the drive rod
8
b
via the force exerted by a flat spring
8
s
, such that the slider
8
x
is driven along the drive rod
8
b
which reciprocates in conjunction with the expansion/contraction of the piezoelectric element
8
c
induced by the application of, for example, a sawtooth-like pulse. The lens frame
2
is connected to the slider
8
x.
Lens devices using such lens driving actuators are complex in construction. Furthermore, it is structurally impossible to individually drive a plurality of lenses, and even if such were possible, the construction would be of excessively greater complexity, and the cost would increase.
SUMMARY OF THE INVENTION
The present invention provides a driving apparatus of simple construction capable of driving an optical member such as a lens element and the like and eliminates the previously described disadvantages.
The present invention providing an actuator using an elastic surface wave generated in the surface layer in the interior of a lens barrel formed of piezoelectric material as a lens drive source, and basically characterized by the integration of the actuator and the lens barrel.
The lens driving actuator of the present invention has a simple construction for individually driving a plurality of lens elements comprising a lens system, and is therefore inexpensive from a cost perspective. Specifically, the lens driving actuator has the following construction.
The lens driving actuator comprises a lens barrel formed of piezoelectric material, an electrode pair comprising a pair of venetian blind-like electrodes opposed to the interior surface of the lens barrel in the axial direction, and a high frequency wave power source for exciting the electrodes of the electrode pair which are arranged so as to form a waveguide between the electrode pair on the interior surface of the lens barrel such that elastic surface waves travel this waveguide in the axial direction via the excitation of the electrodes of the electrode pair. The lens is constructed so as to be movable by pressing against the waveguide.
In then aforesaid construction, when the power source excites via a high frequency wave, an elastic surface wave is generated in the interior surface of the lens barrel and advances along the axial direction forming a waveguide between the pair of electrodes in the interior surface of the lens barrel. The lens pressing against this waveguide is driven along the waveguide in the direction of propagation of the elastic surface wave by the friction force via a drive principle similar to that of an ultrasonic wave motor using a flexible wave as a traveling wave.
According to this construction, the lens is driven simply via the construction of pressing against the a movable lens barrel, thereby rendering unnecessary the components of complex shape such as the stationary barrel and cam ring, and the piezoelectric actuator having a friction member and the like.
It is desirable that the lens is constructed so as to be pressed against the waveguide using engagement, spring force, or elasticity.
According to the aforesaid construction, the lens can be held using a constant pressure force pressing against the waveguide. Accordingly, the lens can be driven with stability.
It is desirable that electrode pairs of two or more electrodes are provided to form a plurality of waveguides. A single lens may press against a plurality of waveguides.
According to the aforesaid construction, the lens is driven via a plurality of parts pressing against the waveguide. Accordingly, the lens can be driven with excellent balance so as to not cause tilting of the lens.
It is desirable that electrodes pairs of two or more electrodes are provided. When only one lens is pressed against one waveguide between electrode pairs, the high frequency wave power source may simultaneously or selectively excite the electrodes of two or more electrode pairs so as to individually drive two or more lenses.
According to the aforesaid construction, since only one lens presses against the waveguide between one electrode pair and the other lens does not press against the waveguide, it is possible to drive only one lens if an electrode of one electrode pair is excited.
It is desirable that the piezoelectric material have a polycrystalline structure.
According to the aforesaid construction, the lens barrel is easily manufactured using a material having a polycrystalline structure, e.g., lead-zirconate-titanate, as the piezoelectric material.
The electrode pairs may be arranged staggered in the circumferential direction rather than arranging the electrode pairs opposite the axial direction, such that the elastic surface wave propagated in the axial direction from one electrode does not reach the other electrode. In this instance, if a lens is pressed against the waveguide formed by the respective electrodes, it is possible to reciprocatingly drive the lens. Furthermore, if the lens is pressed against the waveguide of at least one electrode, the lens can be driven in at least one direction. As an alternative to constructing the entirety of the lens barrel of piezoelectric material, if at least the waveguide part of the lens barrel is formed of piezoelectric material, it is possible to drive the lens pressed against the waveguide. The part comprising the waveguide is not limited to the interior surface of the lens barrel, and also may include the exterior surface of the lens barrel, or may be a lateral surface or channel surface extending in the diameter direction and axial direction.
The lens driving actuator comprises a lens barrel having piezoelectric material extending at least in an axial direction, and the piezoelectric material is arranged so as to form a waveguide for propagating an elastic surface wave in the axial direction via excitation of the piezoelectric material. At least one venetian blind-like electrode and a high frequency wave power source for exciting the electrode are provided. The lens is pressed against the waveguide so as to be movable.
If the electrode is excited via a high frequency wave power source in the aforesaid construction, a lens pressed against the waveguide can be driven in the direction of propagation of the elastic surface wave, i.e., at least in one axial direction.
These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings which illustrate specific embodiments of the inve

Affiliated with

Also associated with

Rating

Driving apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Driving apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Driving apparatus will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2565073