Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2001-05-22
2002-11-05
Lester, Evelyn A (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S694000, C359S819000, C359S822000, C359S825000, C359S827000, C359S828000
Reexamination Certificate
active
06476978
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear-motion helicoid mechanism applied to focusing system of a CCTV camera.
2. Description of the Related Art
Conventionally, a linear-motion helicoid mechanism is, for example, used for a focusing mechanism of a CCTV (closed circuit television) camera which may be utilized as a surveillance camera etc. A conventional linear-motion helicoid mechanism will be explained referring to FIG.
9
. In a linear-motion helicoid mechanism, a lens group B can be made-to move back and forth in the direction of an optical axis PP without causing rotation of the lens frame
13
holding the lens group B. The outer peripheral surface of the cylindrically shaped lens holder
13
B of the lens frame
13
is provided with a male helicoid
13
A and female keyways
13
b
.
The female keyways
13
b
are for controlling the lens frame
13
movement translationally in the axial direction. The lens frame
13
is supported with a camera body (not shown), in a manner which enables it to move translationally in the direction of the optical axis PP, through a key member
15
. The key member
15
is provided with keys
15
a
, each of which engages with each of the keyways
13
b
. Note that the key member
15
is fixed to a mount
16
by a mount spring (an annular spring plate)
17
and screws
18
, so that the key member
15
is threadably supported by the camera body through the mount
16
. The key member
15
is sandwiched between a helicoid female member
50
, provided with a female helicoid
50
a
for engagement with the male helicoid
13
a
provided in the lens frame
13
, and a focus ring
51
. That is, the relative arrangement of the key member
15
and the helicoid female member
50
in the direction of the optical axis PP is fixed, and the distance of the helicoid female member
50
from the camera body is fixed. On the other hand, the helicoid female member
50
is able to rotate about the key member
15
concentric with the optical axis PP. The helicoid member
50
is fixed to the focus ring
51
by three screws
52
(only one shown). Namely, the helicoid member
50
can be rotated about the optical axis PP by the rotational operation of the focus ring
51
. If the helicoid female member
50
is made to rotate by making the focus ring
51
rotate, the lens frame
13
is pushed out from the front to the rear or the rear to the front, by the helicoid mechanism. At this time, the lens frame
13
cannot rotate and can only move translationally along the optical axis PP as the key member
15
is fixed to the camera body.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a simple and miniaturized linear-motion helicoid mechanism that may be used for a CCTV camera, at a low price.
According to the present invention, a linear-motion helicoid mechanism for a CCTV camera is provided with a lens frame, a key member, a helicoid female member, and a rotating frame that is formed integrally with the helicoid female member.
The lens frame is for holding lenses and it comprises a cylindrical lens holder having a first multicrest helicoid and at least one keyway on an outer periphery of the cylindrical lens holder. The key member comprises a cylindrical part having at least one key for engagement with the keyway at an inner periphery of the cylindrical part of the key member. The helicoid female member comprises a cylindrical part having a second multicrest helicoid that screws together with the first multicrest helicoid, at an inner periphery of the cylindrical part of the helicoid female member. The rotating frame fixes the position of the helicoid female member to the key member in an optical axis direction of the lenses and rotatably supports the helicoid female member about the optical axis;
Preferably, the rotating frame and the key member are engaged by a bayonet mechanism, whereby the position of the helicoid female member is fixed to the key member in the optical axis direction and rotatably supported about the optical axis. Due to this, assembly of the rotating frame and key member is simplified and the efficiency of the assembly process is improved.
Preferably, the bayonet mechanism is comprised of a plurality of first pawls provided at the key member and projecting out radially about the optical axis and a plurality of second pawls provided at the rotating frame and projecting in toward said optical axis to engage with each of the first pawls.
The rotating frame and the helicoid female member may be connected by an annular part perpendicular to the optical axis, and openings of the same shape as the second pawls are provided at positions of the annular part facing the second pawls. This simplifies integral molding of the rotating frame and the helicoid female member.
REFERENCES:
patent: 4676605 (1987-06-01), Toda et al.
patent: 5198932 (1993-03-01), Takamura
patent: 5589987 (1996-12-01), Tanaka
patent: 5765048 (1998-06-01), Nomura et al.
patent: 5809348 (1998-09-01), Nomura et al.
patent: 5987262 (1999-11-01), Higuchi et al.
patent: 6055116 (2000-04-01), Nomura et al.
patent: 39 39 399 (1990-08-01), None
patent: 197 02 486 (1997-07-01), None
patent: 10-68859 (1998-03-01), None
patent: 10-68859 (1998-03-01), None
patent: 11-160605 (1999-06-01), None
Japanese Abstract No., 09-211297, dated Aug. 15, 1997.
Asahi Seimitsu Kabushiki Kaisha
Lester Evelyn A
Sughrue & Mion, PLLC
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