Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2001-11-28
2003-11-25
Sugarman, Scott J. (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S694000, C359S703000, C359S823000, C359S826000
Reexamination Certificate
active
06654182
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens barrel used for a zoom lens and the like, and to an optical apparatus with a lens barrel such as a video camera.
2. Description of the Prior Art
An example of a prior art zoom lens for a video camera comprises the following four lens components: a fixed positive lens component, a movable negative lens component, a fixed positive lens component, and a movable positive lens component, which are disposed in this order starting from the object side. However, zoom lenses of other various configurations are also known.
FIG.
12
(A) and FIG.
12
(B) are diagrams showing the configuration of a zoom lens barrel according to the prior art. The zoom lens comprises the following four lens components
201
a
-
201
d
: a fixed front lens compornent
201
a
; a variator lens component
201
b
for moving along the optical axis and thereby varying power; a fixed afocal lens component
201
c
; and a focusing lens component
201
d
for moving along the optical axis and thereby performing focal plane maintenance and focusing at power variation.
The front lens
201
a
is held in a front lens barrel
202
. The variator lens component
201
b
is held in a variator moving ring
211
. The afocal lens component
201
c
is held in a middle frame
215
. The focusing lens component
201
d
is held in a focus moving ring
214
.
The focus moving ring
214
is supported by guide shafts
204
a
and
204
b
which are engaged in the holes of a rear barrel
216
and in the holes of the middle frame
215
positioned by the rear barrel
216
, whereby the focus moving ring
214
can move forward and backward in the direction of the optical axis.
The front lens barrel
202
is fixed on the rear barrel
216
. A guide shaft
203
and a guide screw shaft
208
are supported between the front lens barrel
202
and the rear barrel
216
, whereby the variator moving ring
211
is supported such as to be movable forward and backward in the direction of the optical axis. Further, the front lens barrel
202
, the middle frame
215
, and the rear barrel
216
constitute the outer shape of a substantially sealed lens barrel.
More detailed configurations are as follows. The guide bar
203
,
204
a
, and
204
b
are disposed parallel to the optical axis
205
, and thereby guides the movable lens components and prevents the rotation thereof. A DC motor
206
is a driver for driving the variator lens component
201
b
. In the figure, the DC motor is used as the driver for the variator lens component. However, a step motor may be used instead, similar to the driver for driving the focusing lens component as described later.
The variator lens component
201
b
is held in the variator moving ring
211
. The variator moving ring
211
has: a press spring
209
; and a ball
210
engaged in a screw groove
208
a
formed in a screwed shaft
208
, by a force from the press spring
209
. When the motor drives and revolves the screwed shaft
208
via an output shaft
206
a
and a gear series
207
, the variator moving ring
211
moves along the guide shaft
203
in the direction of the optical axis.
The focusing lens component
201
d
is held in the focus moving ring
214
. A sleeve portion (a portion engaged in the guide shaft and thereby forming a guiding portion) in the focus moving ring
214
is provided with a screw member
213
in the form of a single piece. When a step motor
212
is energized and an output shaft
212
a
thereof revolves, the screw portion formed in the output shaft
212
a
and the screw portion formed in the screw member
213
work together in linkage with the revolution, whereby the focus moving ring
214
moves along the guide shafts
204
a
and
204
b
in the direction of the optical axis.
As described above, such a linkage mechanism with the step motor may be used also in the variator driving mechanism.
In a case where the lens component is moved by such a step motor, when a photo-interrupter (not shown) is provided in order to detect the absolute position of the movable lens component in the direction of the optical axis, and when light blocking wall are provided in the moving ring in the form of a single piece, a reference position of the moving frame in the direction of the optical axis can be detected. After the holding frame is positioned at the reference position, the number of driving steps supplied to the step motor is counted continuously. As such, a position detecting means is obtained for detecting the absolute position of the holding frame.
FIG. 13
is a block diagram showing the electrical configuration of the camera body of an imaging apparatus according to the prior art. In the figure, identical numerals to
FIG. 12
indicate identical components having the same function.
Numeral
221
indicates a solid state image device such as a CCD. Numeral
222
indicates a driver for a variator lens component
201
b
. This includes: a motor
206
; a gear series
207
and a screwed shaft
208
in linkage with the motor
206
; and the like as shown in FIG.
12
. This driver is composed of a step motor or the like similar to the driver for the focusing lens component as shown in FIG.
12
. Numeral
223
indicates a driver for a focusing lens component
201
d
. This includes: a step motor
212
; a male-screwed output shaft
212
a
thereof; a screw member
213
formed in a focus moving ring
214
; and the like.
Numeral
224
indicates an iris driver. Numeral
225
indicates a zoom encoder, while numeral
227
indicates a focus encoder. These encoders detect the absolute positions of the variator lens and the focusing lens component, respectively, in the direction of the optical axis. In a case where a DC motor (not shown in
FIG. 13
) is used in the driver for the variator lens similar to the case of
FIG. 12
, an absolute position encoder such as a variable resistor may be used. Alternatively, a magnetic absolute position encoder may be used.
In a case where a step motor Is used in the driver, generally used is the above-mentioned method wherein the holding frame is positioned at a reference position at first, and that the number of pulses inputted into the step motor is counted continuously.
Numeral
226
indicates an iris encoder. In an example of this encoder, a Hall device is provided inside a meter serving as an iris driver, whereby the relative rotational position is detected between the rotor and the stator.
Numeral
228
indicates a camera signal processing circuit for performing predetermined amplification and gamma correction for the CCD output. The contrast signal of the video signal that undergoes these predetermined processes is provided to an AE gate
229
and an AF gate
230
. In these gates, the regions of signal extraction for exposure determination and focusing are set at an optimum within the field of view. The size of each gated region may be variable. Alternatively, a plurality of regions may be used in each gate. However, a detailed description is omitted for simplicity.
Numeral
231
indicates an AF signal processing circuit for automatic focusing (AF), which generates output signal(s) with respect to high frequency components of the video signal. Numeral
233
indicates a zoom switch. Numeral
234
indicates a zoom tracking memory for storing the information on the focusing lens position to be adopted depending on the object distance and the variator lens position at power variation. The zoom tracking memory may be implemented by a memory in a CPU. Numeral
232
indicates a CPU.
In the above-mentioned configuration, for example, when the zoom switch
233
is operated by a user, in order to maintain a predetermined positional relation between the variator lens and the focusing lens calculated on the basis of the information stored in the zoom tracking memory
234
, the CPU
232
controls the driving of the zoom driver
222
and the focusing driver
223
so that the present absolute position of the variator lens in the direction of the optical axis detected by the zoom encoder
225
coincides with t
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Raizen Deborah A.
Sugarman Scott J.
LandOfFree
Lens barrel and optical apparatus with lens barrel does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lens barrel and optical apparatus with lens barrel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lens barrel and optical apparatus with lens barrel will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3114985