GB2099603A

GB2099603A - Viewing head

Info

Publication number: GB2099603A
Application number: GB8114836A
Authority: GB
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1981-05-14
Filing date: 1981-05-14
Publication date: 1982-12-08
Also published as: GB2099603B

Abstract

A viewing head for inspecting the internal surfaces of the walls of a cavity or conduit optically, including a block 1 of transparent material, one end of which may be adapted to connect to a camera (lens 13), and the other end of which is cylindrical and has a depression 2 in its plane end. The depression 2 is coated with a reflecting material 4 to produce a reflecting convex surface 5, and is preferably of paraboloidal shape. An annular flash tube 14 is provided. <IMAGE>

Description

SPECIFICATION Viewing head The invention relates to devices by which the internal surface of the walls of a cavity or conduit, particularly a liquid filled one, may be inspected optically.

Known devices employ curved mirrors which are either supported on an open framework or enclosed in a transparent tube; in the former case the device is mechanically vulnerable, and its optical performance may be degraded if there is any liquid in the cavity, and in the latter case there may be problems due to unwanted reflections if illumination is to be provided within the system.

According to the present invention there is provided a viewing head including a block of transparent material, one end portion of which is cylindrical and has a depression in its plane end, the shape of the depression being that produced by revolution of a conic section, and the surface of the depression being coated with a reflecting substance.

Preferably the shape of the depression is a paraboloid.

The other end of the block may be provided with means by which it may be attached to a camera, or to a light pipe.

There may also be provided means for illuminating the internal surfaces.

If the viewing head is to be used in a liquid, then it is preferable to choose a transparent material whose refractive index is as close as possible to that of the liquid.

The present invention provides a robust viewing head suitable for use in cavities or conduits containing liquids, whose mirror surface can readily be protected against damage, which can be sealed to a liquid-proof camera housing and which will resist external liquid pressure.

By way of example the invention will now be particularly described with reference to the accompanying drawing, which shows a longitudinal section of an embodiment of the device, attached to one end of a camera housing tube.

Referring to the drawing, which shows a viewing head for use in the inspection of the internal walls of a conduit, a cylindrical block 1 of a transparent material such as polymethylmethacrylate has a paraboloid shaped depression 2 in one end. The surface of the depression 2 is coated with a layer of aluminium 4 so as to form a reflecting surface 5 which will direct light entering the sides of the block 1 along the block 1 towards the camera lens. The layer of aluminium 4 is protected by means of a layer of paint 6, and a steel disc 7 and an O-ring seal 8 which are held in place by a two-piece end-cap 9 which engages in a circumferential groove 1 0.

The seal 8 renders the junction between the disc 7 and the block 1 liquid-proof.

The other end of the block 1 has a plane annular region 11 and a spherical central depression 12 the centre of curvature of which is the nodal point of a camera lens system 13 with which the viewing head is used. An annular flash tube 14 is arranged to project light through the plane region 11 of the end of the block 1, illuminating the internal surface of the conduit under inspection both directly through the block 1 and after reflection from the reflecting surface 5.

In order to prevent the back reflection of light directly into the camera lens 13, a central region of the depression 2 is rendered non-reflecting by means of a blackened hole 3.

The viewing head is attached to a camera housing tube 1 5 to which the camera, of which the lens system 1 3 forms a part, is fixed. The viewing head is attached by a bayonet fitting (not shown) locked in place by three grub screws, one of which 1 6 is shown, which pass through the housing tube 1 5 into a collar 17 which is retained in a circumferential depression 18 in the block 1.

The junction between the housing tube 1 5 and the viewing head is rendered liquid-proof by means of an O-ring seal 19.

Any transparent material can be used for the block 1 but preferably the material is chosen to be such that its surface is not easily damaged. If the viewing head is to be used in a liquid-filled conduit, then the transparent material should be chosen to have a refractive index as near as possible to that of the liquid, and to be inert to the liquid.

A viewing head of this design has been used in a region of high pressure liquid, for example under a depth of several hundred metres of water.

Claims

1. A viewing head for facilitating the inspection of internal surfaces of a structure, including a block of transparent material one end portion of which is cylindrical and has a depression in its plane end, the shape of the depression being that produced by revolution of a conic section, and the surface of the depression being coated with a reflecting substance.

2. A viewing head as claimed in claim 1 in which the shape of the depression is a paraboloid.

3. A viewing head as claimed in either of the preceding claims in which the other end of the block is provided with means by which it may be attached to a camera.

4. A viewing head as claimed in either claim 1 or claim 2 in which the other end of the block is provided with means by which it may be attached to a sealed, liquid-proof camera housing.

5. A viewing head as claimed in either claim 1 or claim 2 in which the other end of the block is

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Viewing head The invention relates to devices by which the internal surface of the walls of a cavity or conduit, particularly a liquid filled one, may be inspected optically. Known devices employ curved mirrors which are either supported on an open framework or enclosed in a transparent tube; in the former case the device is mechanically vulnerable, and its optical performance may be degraded if there is any liquid in the cavity, and in the latter case there may be problems due to unwanted reflections if illumination is to be provided within the system. According to the present invention there is provided a viewing head including a block of transparent material, one end portion of which is cylindrical and has a depression in its plane end, the shape of the depression being that produced by revolution of a conic section, and the surface of the depression being coated with a reflecting substance. Preferably the shape of the depression is a paraboloid. The other end of the block may be provided with means by which it may be attached to a camera, or to a light pipe. There may also be provided means for illuminating the internal surfaces. If the viewing head is to be used in a liquid, then it is preferable to choose a transparent material whose refractive index is as close as possible to that of the liquid. The present invention provides a robust viewing head suitable for use in cavities or conduits containing liquids, whose mirror surface can readily be protected against damage, which can be sealed to a liquid-proof camera housing and which will resist external liquid pressure. By way of example the invention will now be particularly described with reference to the accompanying drawing, which shows a longitudinal section of an embodiment of the device, attached to one end of a camera housing tube. Referring to the drawing, which shows a viewing head for use in the inspection of the internal walls of a conduit, a cylindrical block 1 of a transparent material such as polymethylmethacrylate has a paraboloid shaped depression 2 in one end. The surface of the depression 2 is coated with a layer of aluminium 4 so as to form a reflecting surface 5 which will direct light entering the sides of the block 1 along the block 1 towards the camera lens. The layer of aluminium 4 is protected by means of a layer of paint 6, and a steel disc 7 and an O-ring seal 8 which are held in place by a two-piece end-cap 9 which engages in a circumferential groove 1 0. The seal 8 renders the junction between the disc 7 and the block 1 liquid-proof. The other end of the block 1 has a plane annular region 11 and a spherical central depression 12 the centre of curvature of which is the nodal point of a camera lens system 13 with which the viewing head is used. An annular flash tube 14 is arranged to project light through the plane region 11 of the end of the block 1, illuminating the internal surface of the conduit under inspection both directly through the block 1 and after reflection from the reflecting surface 5. In order to prevent the back reflection of light directly into the camera lens 13, a central region of the depression 2 is rendered non-reflecting by means of a blackened hole 3. The viewing head is attached to a camera housing tube 1 5 to which the camera, of which the lens system 1 3 forms a part, is fixed. The viewing head is attached by a bayonet fitting (not shown) locked in place by three grub screws, one of which 1 6 is shown, which pass through the housing tube 1 5 into a collar 17 which is retained in a circumferential depression 18 in the block 1. The junction between the housing tube 1 5 and the viewing head is rendered liquid-proof by means of an O-ring seal 19. Any transparent material can be used for the block 1 but preferably the material is chosen to be such that its surface is not easily damaged. If the viewing head is to be used in a liquid-filled conduit, then the transparent material should be chosen to have a refractive index as near as possible to that of the liquid, and to be inert to the liquid. A viewing head of this design has been used in a region of high pressure liquid, for example under a depth of several hundred metres of water. Claims

5. A viewing head as claimed in either claim 1 or claim 2 in which the other end of the block is provided with means by which it may be attached to a light pipe.

6. A viewing head as claimed in any one of the preceding claims which is provided with means for illuminating the internal surfaces.

7. A viewing head substantially as hereinbefore described with reference to the drawing.