GB2198256A - Movable blinds to protect optical systems - Google Patents

Abstract

To protect an optical system which can be used out of doors or in a hostile environment wherein a lens or covering window of the system is exposed to the elements or other obscuring medium which can impair the efficiency of the optical system, a blind of optically transparent film (17) mounted on rollers (18, 19) so that a section thereof covers the said lens or window (12), and movable selectively and/or automatically when the said section has water, dirt or other medium thereon to bring a fresh section of blind into the lens or window covering portion. Specified systems are cameras, telescopes and car headlamps. The blind and rollers may be in a disposable cartridge which is clipped on the optical system. <IMAGE>

Description

Improvements Relating to Optical Systems This invention relates to optical systems forming part of apparatus to be used out of doors or in hostile environments, where -the apparatus will be subjected to the elements or other medium such as spray, dirt which can obscure a lens or window of the system thereby reducing the efficiency thereof.

Specifically, the invention has application in relation to motor vehicle headlamps and television cameras.

Thus, motor vehicle headlamps in wet or snowy weather, quickly become covered with dirt and grime thrown up by preceding vehicles, and the headlamps loose their illumination capability. The conventional method of overcoming this disadvantage is to provide headlamp wipers and/or washers.

In the case of television cameras used out of doors, vision often becomes obscured by drops of rain, and at present the only method of clearing such spots of rain is by hand, which means that the camera must be put out of use whilst this cleaning is taking place. It is probably not practical to fit wipers/washers to television cameras.

The present invention aims to provide a means which will serve as an alternative to the wi per/washer arrangement used on vehicles, and can be used on cameras to overcome the aforesaid disadvantages, and can also be used in other optical systems or apparatus such as television, video or other cameras which must work out of doors or in hostile environments.

According to the present invention there is provided an optical system forming part of apparatus to be used out of doors or in a hostile environment wherein a lens or covering window of the system is exposed to the elements or other obscuring medium which can impair the efficiency of the optical system, a blind of optically transparent meterial mounted so that a section thereof covers the said lens or window, and movable selectively and/or automatically when the said section has water, dirt or other medium thereon to bring a fresh section of blind into the lens or window covering portion.

Preferably, the blind is carried in a cassette or cartridge by two rollers, one being a supply roller carrying unused blind and the other being a take-up roller for taking up the used blind.

Preferably also, the cassette or cartridge is a disposable item, and is adapted to be clipped or snapped into position on or in the apparatus.

The cartridge or cassette may have drive means for moving the blind, or said apparatus may have a drive means which couples to said rollers when the cartridge or cassette is positioned on or in the apparatus.

The blind may be of transparent, plastics material, and may be tinted if required, the blind being in the form of a film.

Control of the movement of the film may be by any suitable means, for example under the direct control of a driver or operator involving simply the turning of a handle, the depression of a button or throwing of a switch, or the film may for example be moved automatically by optical sensing devices and associated control means, which operate in that when the film section is obscured to a predetermined degree, this is sensed by the sensing devices and the film is advanced by one section.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a somewhat diagrammatic longitudinal crosssection through one wing of a car; Fig. 2 is a view similar to Fig. 1 showing a modified version of the embodiment shown in Fig. 1; and Fig. 3 is an axial cross-section through a camera lens.

Fig. 1 shows part of a car 1, having a wing panel 2, an underbody panel 3 and incorporating an electrical headlamp 4. The wing panel 2 in conjunction with the underbody panel 2 defines an opening 5 containing a headlamp lens 4A through which light from the lamp 4 is allowed to pass.

At approximately the same height as the upper edge of the perimeter of the opening 5 and within the envelope of both wing and underbody panels 2, 3 respectively is located a horizontal cartridge 6 which contains a coiled unexposed section of a transparent film 7.

Parallel to the axis of the cartridge 6 and in this case, located directly below the same is a storage roller 8 which retains the used section of the film.

Two horizontal guide rollers 9, 10 are fixed at the respective upper and lower edges of the perimeter of the opening 5 and the transparent film 7 drawn out from the cartridge 6 and passes around the upper roller 9, vertically between the guide rollers 9 and 10, around the lower roller 10 and to the storage roller 8. The cartridge 6 is resiliently loaded to hold the film between the cartridge and the roller 8 taut. The light opening 5 and therefore lens 4A are covered by an exposed portion of the taut transparent film 7.

Initially the transparent film 7 is almost completely within the cartridge 6 with only a short strip projecting. The free end of the film 7 is pulled over the horizontal rollers 9, 10 and attached to the storage roller 8. In time that section of film which is held between the rollers 9, 10 becomes dirty and the proportion of light transmitted through the opening 5 falls. When the proportion of light transmitted falls below a certain level it is desirable to replace the dirty film with a clear section of film. This may be achieved by a manual or automatic magic eye rotation of the roller 8 to wind exposed and dirty film as smartly as possible onto that roller, bringing a fresh portion of unused film into the lens position.In a particular arrangement, a small electric motor (not shown) is coupled to the roller 8, and this enables the drawing out of the film to be controlled from the driving position in the car by means of a push-button switch controlling the small electric motor. Instead of an electric means of moving the film, hydraulic, mechanical, air pressure or vacuum may be used.

Referring to the embodiment shown in Fig. 2, which is a modification of the arrangement shown in Fig. 1, similar reference numerals have been used where appropriate. In this embodiment, the bodywork 2, 3 of the vehicle wing is arranged to receive the headlamp 4 as shown with the lens 4A again positioned in the opening 5. However, there is an annular gap between the headlamp body and the bodywork 2, 3 which receives a removal cartridge 6 having supply roller 6A and the take-up roller 8. The cartridge also contains the guide rollers 9 and 10. Again, the film 7 extends over the front of the lens 4A to protect same from dirt and grime. The cartridge 6 including the film, rollers 9, 10, 6A and 8 is removable as a unit, and a replacement cartridge can be clipped or snapped into position.

The film may be advanced when dirty according to any of the methods herein described, and typically, the cartridge may include a small motor for driving the roller 8 in order to advance the film. Alternatively, when the cartridge is clipped into position, the roller 8 may engage drive means which serves for the advancing of the film, in much the same way as a cartridge is used in a conventional camera.

It will be appreciated that the cartridge 6 must be open at the front to allow the light from the headlamp LI to pass through the lens 4A and the section of film covering the lens.

The embodiment of Fig. 2 differs from the embodiment of Fig. 1 only in that the cartridge contains the film and the rollers, and is insertable and removable as a whole, whereas in the arrangement of Fig. 1, the rollers 9 and 10 could remain fixed in position.

The film 7 may cover a single headlamp or double headlamps or in the case of double headlamps two separate films may be used and they may be independently movable. The headlamp/headlamps at each side of the vehicle may be similarly equipped with film 7.

Referring now to Fig. 3, certain parts of a camera which may be a television camera, a video camera or the like are shown and comprise a pair of coaxial lenses 11, 12 fixed within a lens barrel 13 of a camera. In the present case they are fixed by their respective perimeters being located within respective tightly fitting recesses Irl, 15. The light receiving end of the barrel constitutes an aperture 16 which has a taut transparent film 17 retained across it by means of a storage roller 18 and a supply roller 19 contained in a removable and replaceable disposable cartridge 20.

Initially the transparent film is carried by the roller 19 with only a short strip outstanding and the free end of the film attached to the roller 18 so that a section of film covers aperture 16.

Once the exposed portion of film 17 is covered by dust and any other defect to a predetermined degree the roller 18 is rotated so as to expose a fresh piece of film 17 and retain the dirty piece of film on the roller 18. This procedure is followed until the film 17 is almost completely used up where upon a fresh cartridge 20 may be positioned on the lens barrel, the used cartridge being discarded.

Instead of the cartridge 20 being clipped to the outside of the lens barrel as shown, it may be dimensioned to clip inside the barrel to protect the lens 12.

The film in the embodiment described moves down, but it could be arranged to move up, or in fact across the lens or window.

The invention thus provides an effective means for protecting lenses of optical apparatus, and it is to be mentioned that within the expression "optical apparatus" is intended to be covered lighting systems such as a vehicle headlight systems, or any light transmitting window or screen, there is provided an effective means for preventing dirt, grit and grime from obscuring the light path permanently, as when the film is obscured to a predetermined degree, it is simply advanced to bring a fresh portion of film to the optical path. This invention will therefore be of considerable value in motor vehicle headlamp systems, telescopes, cameras, especially video and television cameras and any other optical apparatus which is required to work out of doors on the one hand, and to work in a hostile environment on the other hand.

Claims (8)

1. In or for an optical system forming part of apparatus to be used out of doors or in a hostile environment wherein a lens or covering window of the system is exposed to the elements or other obscuring medium which can impair the efficiency of the optical system, a blind of optically transparent material mounted so that a section thereof covers the said lens or window, and movable selectively and/or automatically when the said section has water, dirt or other medium thereon to bring a fresh section of blind into the lens or window covering portion.

2. A blind according to claim 1, when carried in a cassette or cartridge by two rollers, one being a supply roller carrying unused blind and the other being a take-up roller for taking up the used blind.

3. A blind according to claim 2, wherein the cassette or cartridge is a disposable item, and is adapted to be clipped or snapped into position on or in the apparatus.

4 A blind according to claim 2 or 3, wherein either the cassette or cartridge has drive means for moving the blind, said apparatus has a drive means which couples to said rollers when the cartridge or cassette is positioned on or in the apparatus.

5. A blind according to any preceding claim wherein the blind is a web of transparent plastics material film.

6. A blind according to any preceding claim, wherein the apparatus is a motor vehicle, and the blind section covers one of the front headlamp lenses of the motor vehicle, and there is a similar blind covering the other motor headlamp lens.

7. A blind according to any of claims 1 to LI, wherein the apparatus is a television camera, and the blind section covers the camera window.

8. In or for an optical system forming part of apparatus to be used out of doors or in a hostile environment substantially as hereinbefore described with reference to the accompanying drawings.