GB2452150A

GB2452150A - Camera head having an elastic ring with a protrusion

Info

Publication number: GB2452150A
Application number: GB0815140A
Authority: GB
Inventors: Takeshi Yoshida
Original assignee: Elmo Co Ltd
Current assignee: Elmo Co Ltd
Priority date: 2007-08-20
Filing date: 2008-08-19
Publication date: 2009-02-25
Also published as: JP2009047872A; GB0815140D0

Abstract

A camera head includes a housing (11, 20) having an inner surface, a lens unit (12) mounted on the housing (20) by screws so as to be rotatable thereby to be movable forward or rearward, whereby the lens unit (12) is focused, the lens unit (12) having an outer periphery, and a ring (31) made of an elastic material and attached to the outer periphery of the lens unit (12), the ring (31) having a protrusion (31 a) which is pressed against the inner surface of the housing (20).

Description

CAMERA HEAD

The present invention generally relates to a camera head, and more particularly to such a camera head in which a lens unit mounted on a housing is rotated so as to be movable forward and rearward thereby to be focused.

A head-separated type camera has been put to practical use as a type of video camera. In the head-separated type camera, a camera head and a camera body are connected to each other by a cable. A lens unit and a charge-coupled device (CCD) are incorporated in the camera head side, whereas a power circuit, a video processing circuit, a COD drive circuit and the like are incorporated in the camera body side.

As one of uses of the head-separated type camera, an object spaced away from the camera head is sometimes taken continuously while the camera head is fixed. For example, a camera head is fixed near equipment or a processing machine in order to monitor the operation of the equipment on a production line or a processed state of work in the processing machine. The camera head is focused on the equipment or the work.

In the above-described use of the head-separated type camera, the lens unit is mounted on the housing by screws so as to be movable forward or rearward. The lens unit is rotated so as to be moved forward or rearward thereby to be focused. In this case, when oscillation transferred from the equipment or the processing machine to the camera head rotates the lens unit even slightly after the lens unit has been focused on the equipment or the processing machine, the lens unit is defocused. In view of this problem, it is preferable that the above-desciibed type camera head is provided with a lock which locks the lens unit at a focal position.

Therefore, an object of the present invention is to provide a camera head which has a simple structure, has improved operability and can lock the lens unit at the focal position.

The invention provides a camera head comprising a housing having an inner surface, a lens unit mounted on the housing by screws so as to be rotatable thereby to be movable forward or rearward, whereby the lens unit is focused, the lens unit having an outer periphery, and a ring made of an elastic material and attached to the outer periphery, the ring having a protrusion which is pressed against the inner surface of the housing.

According to the above-described construction, a free rotative movement of the lens unit is limited by friction between the protrusion of the ring and the inner surface of the housing. Consequently, the lens unit can be locked at the focal position. On the other hand, an entire periphery of the ring is not pressed against the inner surface of the housing but only the protrusion is pressed against the inner surface of the housing. Accordingly, the lens unit is forced to be rotated thereby to be focused although the free rotation of the lens unit is limited.

Thus, despite a simple structure that the protrusion is provided on the ring and pressed against the inner surface of the housing, the lens unit can be focused and locked at the focal position.

In another embodiment, the ring has the plural protrusions. When the number and arrangement of the protrusions are suitably selected, the frictional force between the protrusions and the inner surface of the housing can be set so that the lens unit can reliably be locked at the focal position and so that an operation feeling of forced rotation in the focusing of the lens unit can become better. In this case, when the protrusions are arranged so as to be symmetrical about a diameter of the ring, the reliability in the locking of the lens unit can further be improved by a simple structure, and the operation feeling can further be improved.

In further another embodiment, the lens unit has a ring groove formed in the outer periphery thereof, and the ring is attached to the ring groove.

Consequently, the ring can reliably be attached to the outer periphery of the lens unit.

The invention will be described, merely by way of example, with reference to the accompanying drawings: FIG. 1 is a perspective view of a head-separated type camera to which one embodiment of the camera head in accordance with the present invention is applied; FIG. 2 is a schematic block diagram showing an electrical arrangement of the head-separated type camera; FIG. 3 is a sectional view of the camera head; FIG. 4 is a sectional view of a front end of the camera head; FIG. 5 is a front view of a ring attached to the camera head; and FIG. 6 is a sectional view of the ring.

One embodiment of the present invention will be described with the accompanying drawings. Referring to FIG. 1, a head-separated type camera 1 is shown as incorporating a camera head 3 of the embodiment. The head-separated type camera 1 includes a control unit 2 and the camera head 3 which further includes an imaging device such as CCD 13. The camera head 3 is connected to the control unit 2 by an input/output cable 4 (hereinafter, "cable").

The control unit 2 includes an imaging device (hereinafter "CCD") drive circuit, first and second video processing circuits which processes a video signal from the CCD 13, a network processing circuit, a power supply circuit and the like.

Referring to FIG. 3, the camera head 3 comprises a rear housing 11, a front housing 20, a lens unit 12 housed in the front housing 20, and the CCD 13 housed in the rear housing 11. The rear housing 11 has a rear end to which a cable holder 15 is fixed. A cable 4 is inserted through the cable holder 15 thereby to be supported by the latter. A rubber sleeve 16 covers an outer periphery of rear end of the rear housing 11 and a part of the cable 4 inserted through the rear end of the rear housing 11. The CCD 13 includes a substrate holder 17 which is fixed to the front side of the cable holder 15 in the rear housing 11. A circuit board 18 of the CCD 13 and a CCD substrate 19 are mounted on the substrate holder 17.

The rear housing 11 has an open front end to which the front housing 20 is attached and fixed to the substrate holder 17. The CCD 13 is held by the front housing 20, and an optical crystal filter 21 is disposed ahead of the CCD 13.

Furthermore, a cylindrical portion 22 protrudes out of the open front end of the rear housing 11. The cylindrical portion 22 has a female thread 23 formed in an inner circumference thereof. The lens unit 12 includes a rear end threadingly engaged with the female thread 23, whereby the lens unit 12 is rotatable thereby to be moved forward and rearward.

A cap 24 is threadingly engaged with an outer periphery of the front end of the front housing 20, thereby covering the front end of the lens unit 12. Four 0-rings 26 to 29 are fitted with a joint between the rear housing 11 and the cable holder 15, a joint between the rear housing 11 and the front housing 20, a joint between the front housing 20 and the cap 24, and a connection between the cap 24 and the front glass 25 respectively, as shown in FIG. 3. As a result, the entire camera head 3 is water-proofed.

The lens unit 12 has a ring groove 30 formed over a whole mid outer circumference thereof as shown in detail in FIG. 4. A ring 31 is attached to the ring groove 30. The ring 31 is made of an elastic material and includes an outer circumference formed with eight protrusions 31 a at predetermined equiangular intervals as shown in FIGS. 5 and 6. Furthermore, a protruding strip 31b is formed over an entire one end of an inner circumference of the ring 31. The protrusions 31 a are arranged so as to be symmetrical about a diameter of the ring 31. The ring 31 is attached to the lens unit 12 by fitting the protruding strip 31 b in the ring grove 30. The ring 31 has an end 31 c which is located Opposite the protruding strip 31 b and is in contact with an outer circumferential portion of the lens unit 12 outside the ring grove 30. The protrusion 31a is in contact with an inner surface of the front housing 20. Additionally, a space S is defined between the inner circumference of the ring 31 located at opposite the protrusions 31 a and the second groove 30b. Since the ring 31 is made of the elastic material, the protruding strip 31 b is pressed against the bottom of the ring groove 30, and the end 31c located opposite the protruding strip 31b is pressed against the outer circumference of the lens unit 12. Furthermore, the protrusions 31a are pressed against the inner surface of the front housing 20.

In use of the camera head 3 having the above-described structure, the cap 24 and the front glass 25 are detached, and the lens unit 12 exposed out of the front housing 20 is turned so as to be moved forward and rearward along the female screw 23 thereby to be focused. After the lens unit 12 has been focused, the cap 24 and front glass 25 are re-attached thereto for use. Since free rotation of the lens unit 12 is limited by the friction between the protrusions 31 a of the ring 31 and the inner surface of the front housing 20, the lens unit 12 can be locked at a focal position. On the other hand, the entire circumference of the ring 31 is not pressed against the inner surface of the housing 20 but only the protrusions 31a are pressed against the inner surface of the housing 20. As a result, the lens unit 12 can be forced to be turned for focusing although the free rotative movement of the lens unit 12 is limited. Thus, the lens unit 12 can be both locked at the focal position and focused although the camera head of the embodiment has such a simple structure that the protrusions 31 a provided on the ring 31 are only pressed against the inner surface of the housing 20.

Furthermore, the plural protrusions 31a are arranged so as to be symmetrical. Consequently, the lens unit 12 can reliably be locked at the focal position. Still furthermore, the camera head of the embodiment employs the construction of attaching the ring 31 to the ring groove 30. Consequently, the ring 31 can reliably be attached to the outer circumference of the lens unit 12. In particular, since the space S is defined between the bottom of the ring groove 30 and the ring 31 attached thereto, the ring 31 is allowed to flex to the side opposed to the front housing 20 during forced rotation of the lens unit 12.

Accordingly, an operational feeling during the rotation can be improved.

Although the camera head 3 is applied to the head separated camera 1 in the foregoing embodiment, the invention may be applied to any type camera including a camera head wherein a lens unit is mounted on the housing so as to be movable and the lens unit is moved back and forth so as to be focused.

Furthermore, the protrusions 31 a are formed as an example of the protrusion in the foregoing embodiment. However, the protrusion need not reduce the contact area with the inner circumferential surface of the front housing 20, as the protrusion 31 a. A protruding strip having a larger contact area than the protrusion 31a may partially be formed.

Furthermore, a cap to which a single men iscus conversion lens is mounted may be threadingly engaged with an outer circumference of front end of the front housing 20, instead of the cap 24 to which the front glass 25 is mounted. The conversion lens is a concave lens and accordingly increases a field angle. Thus, the camera head is of a wide-angle type in this case. Consequently, the camera head can easily be converted to a telephotographic camera when caps are prepared according to a plurality of types of conversion lens and changed form one to another.

The foregoing description and drawings are merely illustrative of the principles of the present invention and are not to be construed in a limiting sense.

Various changes and modifications will become apparent to those of ordinary skill in the art. All such changes and modifications are seen to fall within the scope of the invention as defined by the appended claims.

Claims

WHAT IS CLAIMED IS: 1. A camera head comprising: a housing having an inner surface; a lens unit mounted on the housing by screws so as to be rotatable thereby to be movable forward or rearward, whereby the lens unit is focused, the lens unit having an outer periphery; and a ring made of an elastic material and attached to the outer periphery, the ring having a protrusion which is pressed against the inner surface of the housing.
2. The camera head according to claim 1, wherein the ring has the plural protrusions.
3. The camera head according to claim 2, wherein the protrusions are arranged so as to be symmetrical about a diameter of the ring.
4. The camera head according to claim 1, wherein the lens unit has a ring groove formed in the outer periphery thereof, and the ring is attached to the ring groove.
5. The camera head substantially as herein described with reference to the accompanying drawings.