Television – Camera – system and detail – Camera image stabilization
Reexamination Certificate
1998-03-02
2004-04-13
Ho, Tuan (Department: 2612)
Television
Camera, system and detail
Camera image stabilization
C348S363000, C348S342000
Reexamination Certificate
active
06720995
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical apparatus such as a video camera, a still camera, a surveillance camera or the like.
2. Description of Related Art
Lens optical systems heretofore employed in the optical apparatuses of the above-stated kind are generally arranged, for example, as shown in FIG.
7
. The lens optical system shown in
FIG. 7
is a zoom lens composed of four lens groups with the fourth lens group which is in the rearmost position arranged to be movable for focusing in the direction of an optical axis. Referring to
FIG. 7
, the lens optical system includes a fixed front lens group
111
, a variator lens group
112
, a fixed lens group
113
and a focusing (compensator) lens group
114
.
The lens optical system further includes a guide bar
133
provided for antirotation, a feed bar
134
arranged for moving the variator lens group
112
, a fixed tube
135
, a diaphragm unit
136
(inserted, in this case, perpendicular to the paper surface of the drawing), a stepping motor
137
employed as a focus motor, and an output shaft
138
of the stepping motor
137
. The output shaft
138
is provided with a male screw
138
a
for moving the focusing lens group
114
. The male screw
138
a
is in mesh with a female screw forming part
139
formed integrally with a moving frame
140
for moving the focusing lens group
114
.
Guide bars
141
and
142
are arranged to guide the focusing lens group
114
. A back plate
143
is arranged to position and retain the guide bars
141
and
142
in their positions. The optical system further includes a relay holder
144
, a zoom motor
145
, a speed reducer unit
146
arranged to reduce the speed of the zoom motor
145
, and interlocking gears
147
and
148
. The interlocking gear
148
is secured to the feed bar
134
for zooming.
The lens optical system shown in
FIG. 7
operates as follows. When the stepping motor
137
is driven, the focusing lens group
114
is caused to move in the direction of the optical axis by screw feeding. When the zoom motor
145
is driven, the feed bar
134
is caused to rotate through the interlocking gears
147
and
148
. The rotation of the feed bar
134
moves a lens frame
112
a
which is in screwed engagement with the feed bar
134
, so that the variator lens group
112
held by the lens frame
112
a
is moved in the direction of the optical axis.
FIG. 8
shows by way of example the details of the diaphragm unit
136
used for the lens optical system. The diaphragm unit
136
is shown in
FIG. 8
as viewed in the direction of the optical axis. Referring to
FIG. 8
, the diaphragm unit
136
includes an aperture part
208
, a motor part
201
, an output shaft (rotating shaft)
202
, a diaphragm lever
203
, projections
204
and
205
provided at the fore ends of the diaphragm lever
203
, diaphragm blades
206
and
207
, a diaphragm body
209
, and guide parts
210
to
213
arranged to guide the diaphragm blades
206
and
207
. The fore end projections
204
and
205
are inserted respectively into slots provided in the diaphragm blades
206
and
207
. The diaphragm blades
206
and
207
are thus interlocked with the diaphragm lever
205
. The aperture part
208
is formed jointly by the diaphragm blades
206
and
207
. When the output shaft
202
rotates, the diaphragm blades
206
and
207
move upward and downward in opposite directions, as viewed in the drawing (the blade
207
moves downward while the blade
206
moves upward). The motions of the diaphragm blades
206
and
207
cause the size of the aperture of the aperture part
208
to vary accordingly. The motor part
201
serving as a drive source is mounted on the diaphragm body
209
. The diaphragm body
209
is provided with the guide parts
210
to
213
.
FIG. 9
shows in detail the structure of the motor part
201
of the diaphragm unit
136
. A turning force is obtained by an ordinary known motor structure composed of a rotor magnet
215
, coils
216
and
217
and a yoke (case)
214
. The motor part
201
is also provided with a Hall element
218
for detecting the rotation of the motor part
201
.
In addition to light quantity control by means of the diaphragm unit arranged as described above, a video camera or the like can perform light quantity control by the so-called shutter speed control means for controlling an electric charge storing time of an image sensor (CCD). FIG.
10
(
a
) shows the electric charge storing time in relation to the field period of a television signal. In the case of the NTSC system, one field period which corresponds to {fraction (1/60)} sec is set to the electric charge storing time in its entirety. The lowest shutter speed is normally {fraction (1/60)} sec. The electric charge storing time can be shortened for a higher shutter speed, as shown in FIG.
10
(
b
).
FIG. 11
shows in a block diagram a light quantity control arrangement conventionally adopted for a video camera. Referring to
FIG. 11
, a zoom lens is composed of lens groups
111
to
114
in the same manner as in the case of
FIG. 7. A
diaphragm unit
136
is arranged as shown in
FIGS. 8 and 9
. However, the diaphragm unit
136
is not limited to the arrangement having two diaphragm blades as in the case of
FIGS. 8 and 9
. An iris diaphragm which has more than two blades may be used for the diaphragm unit
136
. A CCD
151
is employed as an image sensor. F-number detecting means
501
is generally arranged to detect the absolute rotating position of a rotor of the diaphragm unit
136
by means of a Hall element as shown in
FIG. 9. A
CPU
502
is arranged to control a driving action of each light quantity adjusting means in accordance with each program diagram which will be described later herein. The video camera shown in
FIG. 11
further includes a CCD driving circuit
503
, a camera circuit
504
, a mode selecting means
505
, a mode dial
506
, a shutter speed designating means
507
and an aperture value designating means
508
.
The camera circuit
504
is arranged to perform signal processing actions of varied kinds, such as an amplifying process, a gamma correction process, etc. Among the signals processed, a luminance signal is taken into the CPU
502
. With the luminance signal taken in the CPU
502
, the level of the luminance signal is checked to find whether the light quantity is apposite (a correct-exposure light quantity), or excessive (an over-exposure light quantity) or insufficient (an under-exposure light quantity). The CPU
502
then adjusts the light quantity according to the result of the check. For the light quantity adjustment, it is conceivable to control and adjust the diaphragm aperture diameter at the diaphragm unit
136
and the electric charge storing time, i.e., a shutter speed, at the CCD
151
, as mentioned in the foregoing. Further, in a case where the light quantity is still insufficient, i.e., an under-exposure light quantity, with the diaphragm unit
136
fully opened to its maximum aperture position and the shutter speed set at its lowest speed, it is generally practiced to increase the gain of the video signal (a gain-up action) at the camera circuit
504
. At the time of such light quantity adjustment, when the mode dial
506
is operated by the operator to select one of shooting (image-taking) modes of various kinds called an automatic mode, a sport mode, a portrait mode, etc., the manner of the light quantity adjustment, i.e., a program line, is changed according to the shooting mode thus selected. Further, when the mode dial
506
is set at a position for a manual mode, a value designated by the shutter speed designating means
507
or the aperture value designating means
508
is transmitted through the mode selecting means
505
to the CPU
502
.
FIG. 12
shows combinations of aperture values and shutter speeds by which optimum light quantities can be obtained for different object luminances according to the shooting mode selected. Incidentally, the relation between the illuminance (luminance) and an exposure value
Kaneda Naoya
Sato Hidekage
Canon Kabushiki Kaisha
Ho Tuan
Robin Blecker & Daley
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