Lens barrel and optical equipment

Details Lens barrel and optical equipment Lens barrel and optical equipment

1996-12-31

2001-09-11

Mack, Ricky (Department: 2873)

Optical: systems and elements

Lens

With variable magnification

C359S824000, C359S696000, C310S323090

Reexamination Certificate

active

06288848

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens barrel and an optical equipment, and more particularly to a lens barrel and an optical equipment that allow an automatic focusing operation by a vibration motor such as an ultrasonic motor and a manual focusing operation without any particular switching operation.
2. Related Background Art
FIG. 1
is a cross-sectional view of a conventional lens barrel.
In
FIG. 1
, there are shown an outer tube
501
of the lens barrel; a fixed tube
503
having an outer tube portion
503
a
positioned in front of the outer tube
501
and a helicoid forming portion
503
b
provided inside the outer tube portion
503
a
; a manual operating ring
504
fitted on a circumferential groove
503
c
formed on the external periphery of the outer tube portion
503
a
of the fixed tube
503
and on a circumferential groove
501
a
formed on the external periphery of the outer tube
501
and rendered rotatable about the optical axis Z of the lens L; and a lens holder
505
supporting the lens L and provided on the external periphery with a helicoid
505
b
engaging with a helicoid
503
d
formed on the internal periphery of the helicoid forming portion
503
b
of the fixed tube
503
. The lens holder
505
is penetrated by a groove
505
a
extending parallel to the optical axis Z, and a lens holder driving arm
520
, to be explained later, having a portion parallel to the optical axis Z is inserted in the groove
505
a
so as to be slidable only in the radial direction of the lens L.
A tubular member
502
is provided at an end thereof with an outward flange
502
a
connected by screws
522
with the rear end of the fixed tube
503
and, at the other end, with an inward flange
502
b
connected by screws
523
with the outer tube
501
. On the external periphery of the tubular member
502
, there are mounted all the components of an ultrasonic motor
530
, an output member
531
in contact with a rotary ring
512
of the ultrasonic motor
530
and a manual operation force entering ring
516
for entering the operation torque of the above-mentioned manual operation ring
504
.
In the following, there will be explained the components of the ultrasonic motor
530
and the structure of the output member
531
.
The ultrasonic motor
530
is composed of an annular vibration member
506
(corresponding to a stator) having a trapezoidal cross section; an electrostriction element
507
physically adhered to an end face of the vibration member
506
; an annular vibration absorbing member
510
composed, for example, of felt and pressed to the surface of the electrostriction element
507
; a first annular spacer
509
positioned in contact with an end face of the vibration absorbing member
510
; a first annular Belleville spring
508
for pressing the spacer
509
toward the annular vibration member; a first annular nut
511
fitted on a screw portion
502
d
formed on the external periphery of the tubular member
502
; a rotary ring
512
constituting a part of the rotor of the ultrasonic motor
530
; a rubber ring
513
for avoiding the transmission of axial vibration to the rotary ring
512
; an annular circumferentially movable member
514
; and a vibration member rotation-blocking member
515
fitted on the external periphery of the tubular member
502
and having an external rim projection
515
a
inserted in a groove
506
a
of the vibration member
506
.
The rotary ring
512
, the rubber ring
513
and the circumferentially movable member
514
are integrated to constitute the rotor of the ultrasonic motor
530
, and a circumferentially traveling wave generated in the vibration member
506
causes the rotor, consisting of the rotary ring
512
, the rubber ring
513
and the circumferentially movable member
514
, to rotate about the optical axis Z.
The nut
511
is provided for adjusting the contact pressure between the vibration member
506
and the circumferentially movable member
514
, by the adjustment of the elastic force of the Belleville spring
508
.
An output ring
531
positioned adjacent to the end face of the rotary ring
512
(namely, the rotor) of the ultrasonic motor
530
is composed of a ring
519
, rotatably fitted on the external periphery of the tubular member
502
; roller support shafts
518
fixed in at least three positions on the periphery of the ring
519
so as to protrude from the external periphery thereof along radial axes perpendicular to the optical axis (axis of the ultrasonic motor); and hollow rollers
517
fitted on the roller support shafts
518
.
The ring
519
also serves as the output member of a drive force generating unit
532
(including the ultrasonic motor
530
and the output ring
531
), and an L-shaped lens holder driving arm
520
, for rotating the lens holder
505
, is fixed by a screw
521
to an end face of the ring
519
.
The rollers
517
are in contact, at the external periphery thereof, with an end face of the rotary ring
512
and an end face of the manual operation force entering ring
516
.
The manual operation force entering ring
516
is rotatably fitted on the tubular member
502
and is in contact, at an end face (at the right side in the drawing), with the external periphery of the rollers
517
.
The external peripheral rim of the manual operation force entering ring
516
engages with a recess in the internal periphery of the manual operation ring
504
, whereby the ring
516
is rotated by the manual operation ring
504
.
The above-mentioned lens holder driving arm
520
is inserted, through a hole
502
c
penetrating the periphery of the tubular member
502
, into the groove
505
a
of the lens holder
505
. The hole
502
c
penetrating the periphery of the tubular member
502
is an oblong hole extending in the circumferential direction.
The above-mentioned rollers
517
constitute a differential mechanism, positioned between the manual operation force entering ring
516
for the manual focusing operation and the rotary ring
512
of the ultrasonic motor for the auto focusing operation. The differential mechanism uses the output side thereof for driving a focusing lens, whereby the structural feature of the ultrasonic motor is fully exploited, particularly in the manual focusing operation.
The full exploitation of the structural feature of the ultrasonic motor means that, due to a fact that the rotor featuring the ultrasonic motor is maintained in pressure contact with the stator, the non-rotating state of the rotor is constantly maintained by the frictional force between the rotor and the stator except when the motor is driven so that the motor input ring connected to the rotor is also maintained in the non-rotating state without requiring any particular structure.
In the above-explained differential mechanism, the pressure of the Belleville spring
508
maintains the non-rotating state of the manual operation force entering ring
516
even when the rotary ring
512
is rotated, and, in the case of a manual focusing operation by the rotation of the manual operation force entering ring
516
, the non-rotating state of the rotor (
512
-
514
) of the ultrasonic motor is maintained, since the rotor is maintained in pressure contact with the stator, so that the auto focusing operation and the manual focusing operation can be switched without any switching mechanism.
In the conventional lens barrel explained above, rollers are employed in the planet mechanism in the differential mechanism for switching the manual focusing operation and the auto focusing operation without any converting operation, and the transmission of the driving force is achieved by maintaining these rollers in friction contact on both sides with the output end face constituted by the rotary ring of the ultrasonic motor and with the output end face constituted by the manual operation force entering ring. The pressure for such friction contact utilizes that of the pressurizing member of the stator of the ultrasonic motor and is so set as to balance the slip torques of the friction

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