Optical: systems and elements – Lens – With support
Reexamination Certificate
2000-02-15
2002-09-17
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With support
C359S822000, C359S814000, C396S342000, C351S107000
Reexamination Certificate
active
06452732
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving device for selectively moving a plurality of driven members from the position on one and the same axis to a predetermined position by switching the use of the driven members from one over to another, or a filter change-over device for change-over of ND (neutral density) filters or the like to be used by being inserted into and retracted out of an optical path for adjustment of light quantity in an image pickup device of an optical apparatus, such as a video camera or the like, and more particularly to a filter change-over device arranged to selectively insert a plurality of filters of different densities into the optical path by changing use of them from one over to another.
2. Description of Related Art
Zoom lenses for video cameras have been most popularly composed of four lens units, i.e., in order from the object side, a positive fixed lens unit, a negative movable lens unit, a positive fixed lens unit and a positive movable lens unit. The known zoom lenses adapted for video cameras of course include other zoom lenses arranged differently from the lens arrangement mentioned above.
FIGS.
12
(A) and
12
(B) show the construction of a zoom lens barrel of the most popular four-lens-unit arrangement. As shown in FIGS.
12
(A) and
12
(B), the zoom lens is composed of four lens units
201
a
to
201
d
, i.e., a front lens unit
201
a
which is fixed, a variator lens unit
201
b
which is arranged to perform a magnification varying action by moving along an optical axis
205
, an a focal lens unit
201
c
which is fixed, and a focusing lens unit
201
d
which is arranged to move along the optical axis
205
to keep a focal plane constant when the magnification varying action is performed as well as to adjust focus.
Referring to FIGS.
12
(A) and
12
(B), guide bars
203
,
204
a
and
204
b
are arranged in parallel with the optical axis
205
to guide the moving lens units and also to prevent the moving lens units from rotating. A DC motor
206
is a drive source arranged to move the variator lens unit
201
b
. While the DC motor
206
is used as the drive source for the variator lens unit
201
b
, a stepping motor may be used in place of the DC motor
206
, in the same manner as a stepping motor which is used as a drive source for the focusing lens unit
201
d.
The variator lens unit
201
b
is held by a holding frame
211
. The holding frame
211
is provided with a pressing spring
209
and a ball
210
which is pushed by the force of the pressing spring
209
to engage a screw groove
208
a
formed in a screw bar
208
. Therefore, when the screw bar
208
is driven to rotate by the DC motor
206
through an output shaft
206
a
and a gear train
207
, the holding frame
211
moves in the direction of the optical axis along the guide bar
203
.
The focusing lens unit
201
d
is held by a holding frame
214
. The holding frame
214
has a sleeve part fitted on the guide bar
204
b
to act as a guide. A screw member
213
is arranged in the neighborhood of the sleeve part to be in one body with the holding frame
214
in the direction of the optical axis. When a stepping motor
212
is caused to rotate, its output shaft
212
a
rotates. Then, a male screw part formed on the output shaft
212
a
and a female screw part or a rack part formed in the screw member
213
move in association with the rotation of the stepping motor
212
. This causes the holding frame
214
to move in the direction of the optical axis along the guide bars
204
a
and
204
b
. The details of a part where the holding member
214
and the screw member
213
are coupled with each other are disclosed, for example, in Japanese Laid-Open Patent Application No. HEI 4-136806.
As mentioned above, the interlocking mechanism of the stepping motor
212
is applicable also for driving the variator lens unit
201
b.
In a case where a lens unit is arranged to be moved by a stepping motor together with a moving frame, as described above, the absolute position in the direction of an optical axis of the lens unit can be detected by arranging a photo-interrupter (not shown) and a light-blocking wall which is formed integrally with the moving frame and by arranging one reference position of the moving frame in the direction of the optical axis to be detectable with the photo-interrupter and the light-blocking wall. Position detecting means can be thus arranged to be capable of detecting the absolute position of a lens holding frame, i.e., the moving frame, by setting the lens holding frame at the reference position and, after that, by continuously counting the number of driving pulses applied to the stepping motor.
FIG. 13
is a block diagram showing the electrical arrangement of a camera body included in a conventional image pickup apparatus. In
FIG. 13
, all parts that are indicated by the same reference numerals as in FIGS.
12
(A) and
12
(B) are arranged in the same manner as those shown in FIGS.
12
(A) and
12
(B).
Referring to
FIG. 13
, a solid-state image sensor
221
is composed of a CCD, etc. A zoom drive source
222
is arranged to drive the variator lens unit
201
b
. The zoom drive source
222
includes the motor
206
, the gear train
207
which is interlocked with the motor
206
, the screw bar
208
, etc. The zoom drive source
222
may be also arranged to include a stepping motor, etc., in the same manner as the focusing lens unit driving arrangement shown in FIG.
12
(B). A focusing drive source
223
is arranged to drive the focusing lens unit
201
d
and includes the stepping motor
212
, the output shaft
212
a
which has a male screw formed thereon and the screw member
213
which is arranged integrally with the holding frame
214
in the direction of the optical axis.
The camera body further includes a diaphragm drive source
224
, a zoom encoder
225
and a focus encoder
227
. The zoom and focus encoders
225
and
227
are arranged to respectively detect the absolute positions of the variator lens unit
201
b
and the focusing lens unit
201
d
in the direction of the optical axis. In a case where a DC motor is employed as the drive source for driving the variator lens unit
201
b
as in the case of FIG.
12
(A), an absolute position encoder such as a potentiometer or the like is employed as the zoom encoder
225
. A magnetic encoder may be used instead of using a potentiometer.
In a case where a stepping motor is employed as a drive source, the absolute position of a lens unit is generally detected by setting a lens holding frame at a reference position and by continuously counting the number of operating (driving) pulses applied to the stepping motor, as mentioned above.
A diaphragm encoder
226
is arranged by having a Hall element inside of a meter which is a drive source for a diaphragm
235
and by detecting a relation between the rotating position of a rotor and that of a stator.
A camera signal processing circuit
228
is arranged to perform an amplifying process, a gamma correction process, etc., on a video signal outputted from a CCD
221
in a predetermined manner. A contrast signal of the video signal thus processed passes through an AE gate
229
and an AF gate
230
. These gates
229
and
230
are arranged to set and determine an optimum signal fetching range within the whole image plane for determining an exposure and for focus adjustment. Such a gate either may be arranged to have a variable size or may be plurally arranged. However, for the sake of simplification of description, the details of the gate arrangement are omitted from the description.
An AF signal processing circuit
231
is provided for automatic focusing (AF) and is arranged to form one or a plurality of outputs relative to high-frequency components of a video signal. A zoom switch
233
is connected to a CPU
232
. A zoom tracking memory
234
is arranged to store information on focusing lens positions to be taken according to object distances and variator lens positions obtained when a magnification varying act
Kaneda Naoya
Okada Tadanori
Epps Georgia
Robin Blecker & Daley
Thompson Tim
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