Flange back focus adjustment mechanism for a video camera

Television – Camera – system and detail – Support or housing

Reexamination Certificate

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Details

C348S335000, C348S345000, C359S699000, C359S701000, C359S696000

Reexamination Certificate

active

06683654

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a video camera most suitable for use of such as a CCD camera, and more particularly to a video camera having a front panel, on which a lens mount is formed, and an imaging device such as a CCD is spaced at an adjustable distance from the lens mount along an optical axis.
A CCD camera as an example of the video camera has already been proposed by the present applicant as disclosed in Japanese Patent Application No. Hei5-258848, for example.
FIGS. 51
to
53
show such a CCD camera
1
in the related art. The exterior of the CCD camera
1
is composed of three separate parts, i.e., a front panel
2
, a camera case
3
, and a rear panel
4
. The front panel
2
is formed by die casting such as aluminum die casting, or it is composed of a front panel chassis
2
A formed by die casting and a front panel cover
2
B formed by molding of a synthetic resin or the like for covering the front panel chassis
2
A. The camera case
3
is composed of an upper case and a lower case each formed from a sheet metal or the like. The rear panel
4
is composed of a rear panel chassis formed from a sheet metal or the like and a rear panel cover formed as a molded part for covering the rear panel chassis. The front panel
2
has a front wall
2
a
formed with an annular lens mount
5
perpendicular to an optical axis P as surrounding the optical axis P. The annular lens mount
5
is formed over its inner circumference with a lens mounting portion
6
such as a tapped hole. Although not shown, a lens such as a C-mount lens and a CS-mount lens is removably mounted to the lens mount
5
.
Installed inside the front panel
2
of the CCD camera
1
is a flange back focus adjusting mechanism
11
for adjusting a flange back focus of a CCD
12
as an imaging device with respect to the lens mount
5
according to the kind of the lenses (e.g., a C-mount lens and a CS-mount lens) removably mounted to the lens mount
5
. The flange back focus adjusting mechanism
11
includes the CCD
12
, a substantially circular CCD holder
13
formed of a synthetic resin as an imaging device holder, a circular adjuster ring
14
formed of a synthetic resin, a pair of cam followers
15
formed on the outer circumference of the CCD holder
13
so as to be circumferentially equally spaced at 180° from each other, a pair of arcuate cams
16
formed on the inner circumference of the adjuster ring
14
so as to be circumferentially equally spaced at 180° from each other and to face the cam followers
15
in the direction shown by an arrow a, a pair of compression springs
17
as means for pressing the cam followers
15
onto the cams
16
in the direction shown by an arrow b opposite to the arrow a, a ring holder plate
18
as a ring holding member formed from a sheet metal or the like for holding the adjuster ring
14
from its rear side in the direction of the arrow a, and a lock member
19
for locking the adjuster ring
14
. The CCD
12
is preliminarily mounted in the CCD holder
13
together with a filter bracket
20
, a filter
21
, a rubber seal
22
, a CCD bracket
23
, and a CCD board
24
in perpendicular relationship with the optical axis P.
The front panel
2
has a rear wall
2
b
from which a cylindrical portion
25
projects parallel to the optical axis P in the direction of the arrow b. The flange back focus adjusting mechanism
11
is assembled by first mounting the springs
17
, the CCD holder
13
, the adjuster ring
14
, the ring holder plate
18
, and the lock member
19
in this order in the direction of the arrow a into the front panel
2
at inner and outer circumferential portions of the cylindrical portion
25
, and then fastening the ring holder plate
18
at its four corners to the rear wall
2
b
of the front panel
2
by means of four screws
26
against the biasing forces of a pair of springs
17
. The lock member
19
is mounted between the adjuster ring
14
and a side wall
2
c
of the front panel
2
, and is releasably pressed on the adjuster ring
14
by a set screw
27
laterally screwed through the side wall
2
c
in a direction perpendicular to the optical axis P.
The front panel
2
has upper and lower walls
2
d
formed with a pair of upper and lower slits
28
in cooperation with upper and lower recesses of the camera case
3
, and the adjuster ring
14
is exposed at its upper and lower portions through the upper and lower slits
28
. Accordingly, by rotating the adjuster ring
14
at these exposed portions, a pair cams
16
operate to axially move the cam followers
15
in the directions of the arrows a and b along the optical axis P in cooperation with the springs
17
, thereby adjusting the flange back focus of the CCD
12
with respect to the lens mount
5
. As shown in
FIG. 52
, connectors
31
, terminal strips
32
, switches
33
, and a volume controller
34
are mounted on the rear panel
4
.
As shown in
FIGS. 49A and 49B
and
FIGS. 50A and 50B
showing the cam mechanism of the CCD camera
1
in the related art, each of the pair of cam followers
15
of the CCD holder
13
is integrally formed with two radially extending ribs
15
c
having different height H
1
and H
2
in the direction of the optical axis P. The two ribs
15
c
of each cam follower
15
are kept in pressure contact with three tilted cam surfaces
16
a
,
16
b
, and
16
c
of the corresponding cam
16
by the corresponding spring
17
in the direction of the optical axis P. The three tilted cam surfaces
16
a
,
16
b
, and
16
c
are different in angle of tilt and height in the direction of the optical axis P.
Accordingly, the flange back focus adjusting mechanism
11
in the related art CCD camera
1
is designed so as to maintain the balance of the CCD holder
13
in a four-point contact fashion such that the total four ribs
15
c
of the pair of cam followers
15
equally spaced at 180° from each other in the circumferential direction of the CCD holder
13
are in contact with the cam surfaces
16
a
,
16
b
, and
16
c
of the pair of cams
16
spaced at 180° from each other in the circumferential direction of the adjuster ring
14
. However, in actual, the four ribs
15
c
are not always in contact with the cam surfaces
16
a
to
16
c
, but three of the four ribs
15
c
variably come into contact with the cam surfaces
16
a
to
16
c
. In other words, any one of the four ribs
15
c
is always separate from the cam surfaces
16
a
to
16
c
. Accordingly, the CCD holder
13
is minutely vibrated depending on what ribs
15
c
are used to keep the balance of the CCD holder
13
.
The cam surfaces
16
a
and
16
b
are formed in gentler slopes for fine adjustment, and the cam surface
16
c
is a steep slope for coarse adjustment, therefore, the angle of tilt thereof differs from each other. Further, the heights H
1
and H
2
of the two ribs
15
c
of each cam follower
15
are set so as to correspond to the angle of tilt of the gentle cam surfaces
16
a
and
16
b
. Accordingly, the two ribs
15
c
are stable on the gentle cam surfaces
16
a
and
16
b
, but are not stable on the steep cam surface
16
c
. Furthermore, when a point
16
d
between the cam surfaces
16
a
and
16
c
or another point
16
d
between the cam surfaces
16
c
and
16
b
comes between the two ribs
15
c
as shown in
FIG. 50B
, undue tilt forces are applied to the two cam followers
15
, causing an unstable holding condition of the CCD holder
13
. The instability of the CCD holder
13
causing vibrations is a serious problem because it immediately causes face vibrations of the CCD
12
, which lead to a deterioration in image quality.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a video camera which can always stably perform adjustment of the flange back focus of the imaging device.
According to an aspect of the present invention, there is provided in a video camera having a front panel, on which a lens mount is formed and an imaging device thereof is spaced at an adjustable distance from the lens mount along an optical axis, the im

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