GB2345449A - A method and apparatus for forming an image - Google Patents

Abstract

A method for forming an image involves projecting a beam of coherent light 11 through a plurality of refractive surfaces. The surfaces may take the form of plastic sheets 12 which have been crumpled e.g. by hand folding or vacuum. The sheets 12 are supported in the carrier 15, which surrounds the light beam and may be rotated to produce a dynamic effect. They need not be securely fixed in the carrier 15, so that as it is rotated they can move position. The pattern produced is projected onto a target surface 14 which may be a suitable screen, or alternatively photosensitive paper. Preferably, the coherent light source 11 is a laser.

Description

TITLE: VISUAL ENTERTAINMENT DISPLAY PROCESS AND APPARATUS The present invention relates to a process and apparatus for visual entertainment display. In particular it relates to shining coherent light upon a target, in such a way as to provide an interesting and attractive display.

Since the laser was invented in the 1960's, it has found many uses, including a number of uses in the entertainment industry. It provides a source of coherent light, capable of travelling over great distances without attenuation. It is frequently used for its spectacular effects to give light shows', often as part of a multi-media entertainment, featuring music, live performers and the like. Such entertainments may be on various scales, e. g. indoors (for example as an accompaniment to dancing in clubs or discos) or outdoors, (for example as part of a "son et lumiere"show).

The nature of laser light is such that it does not usually show to best advantage on a screen, giving a single point, or (if oscillated) harsh lines. Laser beams are therefore typically visualised by being projected into a fog or vapour, to produce 3-dimensional images. However, it is often not convenient to provide such a fog or vapour, particularly in locations which are not specially adapted for giving laser performances. It is much easier to project onto a flat surface, for example a screen (if indoors) or the existing wall or ceiling of a building (for larger displays, whether inside or outside).

The present invention seeks to overcome this disadvantage by providing a method of projecting a laser onto a target surface in such a way as to produce an entertaining and aesthetically satisfying light display.

The invention accordingly comprises a method for producing a light display which comprises projecting a beam of coherent light to form an image on a target surface through a plurality of refracting surfaces at least some of which are oriented acutely to the axis of the beam. Preferably the refracting surfaces are in motion during the passage of the beam, so as to provide moving images on the target surface. The motion of the refracting surfaces is preferably periodic, particularly a rotation: e. g. about the axis along which the beam of coherent light passes immediately prior to contacting the refractive surfaces, or an axis roughly parallel thereto. In a preferred form of the invention, the target surface is a display surface, such as a projector screen.

The invention further provides apparatus for use in the method of the invention which comprises a carrier provided with transparent refractive elements, the carrier being disposable around the path of a coherent light beam with at least some surfaces of the elements forming acute angles with the axis of the light beam, means being provided to rotate the carrier about the incident light beam.

The number of elements used in the invention is not critical. If found convenient, a single element of irregular shape may provide a number of refractive surfaces. We prefer to use laminar elements which have been slightly distorted, in particular stiff plastic sheets : a convenient number of plastic sheets is from 2 to 10.

The angles between the incident beam and at least some of the refractive surfaces should be acute, preferably not greater than 45 : most preferably it will be between about 5 and about 20 .

The invention will be further described with reference to the drawings, in which: Figure 1 is a plan view of apparatus according to the invention; Figure 2 is a sectional view along the line A-A of Figure 1.

The apparatus shown is for small-scale display, as in a disco. It comprises a laser 10 (for example a home entertainment Crab laser as sold by Soundlab, code G01 18AA, laser diode wavelength 635-650 nanometers, maximum output 5 watts) adapted-to project a coherent light beam11 through refractive surfaces 12 mounted in a carrier 13 and onto a white screen 14. The refractive surfaces 12 comprise four stiff resilient sheets of clear plastic about 0.02mm thick, which have been deformed by hand folding, so as to contain several permanent creases. They are fixed in position with adhesive in the carrier 13, which is a sleeve of transparent plastic. The carrier 13 is supported as a push-fit by longitudinal ribs 19 within a cylindrical holder 15 open at both ends and mounted co-axially with the path of the beam 11. The holder 15 is mounted on bearings (not shown) allowing it to be rotated about its longitudinal axis by means of a pulley and belt drive 16 powered by a small electric motor 17.

In operation, ambient lighting is dimmed or extinguished, and the laser 10 and the motor 17 are switched on. The beam 11 passes into the carrier 13, and undergoes multiple refractions in passing through the transparent plastic surfaces 12. The beam 11 is thus split up into numerous different rays 18: these emerge from carrier 13 and make pleasing patterns on the display screen 14. The rotation of the holder 15 by the motor 17, preferably rather slowly, at a rate of say 4 revolutions per minute, ensures that the display changes in a cyclic fashion.

The displays produced by the apparatus shown are often unexpectedly dramatic, and some of the effects obtained have been compared to views on a journey through distant galaxies.

Numerous changes in this relatively simple arrangement may be made. The laser beam 11 may be split or'reflected (wholly or partially) before or after passing through the carrier 13; or other beams, from lasers of different colours, may be projected through the carrier, simultaneously or sequentially. To add variety to the display, carrier 13 can readily be changed for other carriers, containing more or fewer refractive surfaces, differently disposed, shaped or folded. Such surfaces 12 can be fixed within the carrier 13, or loose, so that they change position slightly during rotation, giving rise to non-repeating patterns. The beam 11 can be displaced from, or at an angle to, the axis of the carrier 13. While other motions than, or as well as, rotation may be imposed on the carrier 13, for example oscillation or vibration, it is generally found that smooth slow movements give a superior aesthetic effect.

Many different types of laser projector can be used in the invention. The laser described produces a single red beam, but other lasers (e. g, gas lasers) are available which give other colours, as blue, green, etc.; some projectors using more than one laser diode can project different types of beam at the same time.

The surfaces 12 are preferably irregular. For large-scale manufacture, it may not be convenient to form such surfaces by hand folding or crumpling. Instead, plastic sheets could be vacuum-formed to give wavy or indented surfaces, and optionally further irregular creasing could be added by cold rolling.

For larger-scale, or outdoor, displays, it is only necessary to use more powerful lasers (for example up to 40 watts, or more) and a suitable reflecting surface, for example the wall or ceiling of a building. The invention contemplates one possible surface on which displays might be made as the ceiling of the Millennium Dome.

The displays produced by the process and apparatus of the invention can be fascinating to watch, even for extended periods. Accordingly their use for such purposes as aids to meditation, in calming agitated or distressed patients, or soothing babies, forms part of the invention.

The novel character of the displays may, if desired, be partially captured in still pictures. In a further aspect, the target surface used in the process of the invention is photosensitive. This allows still images to be captured.

The photosensitive target surface may be an array of electronic light-sensitive elements, allowing the image to be captured in digital form. Or it may be a light-sensitive film or paper, for example bromide photographic paper, or cyanotype paper, treated with ferric ammonium citrate/potassium ferricyanide, such as is used in making blueprints. Exposure times depend on the nature, particularly sensitivity, of the light-sensitive target (e. g., film speed) and the image desired. For a sharp image, a short exposure time must be used, or alternatively the refracting surfaces can be held stationary. Interesting images can also be obtained by exposures lasting for part of, or a complete, rotation of the refracting surfaces.

After exposure, the images can be fixed in permanent form in well-known ways: for example, where photographic film is used as the target surface, by developing and printing.

The invention accordingly further comprises fixed images produced by means of the process and apparatus of the invention.

Claims (11)

1. I claim: 1. A method for producing a light display which comprises projecting a beam of coherent light to form an image on a target surface through a plurality of refracting surfaces at least some of which are oriented acutely to the axis of the beam.
2. 2. A method as claimed in claim 1 wherein the refracting surfaces are in motion during the passage of the beam, so as to provide moving images on the target surface.
3. 3. A method as claimed in either of claims 1 or 2 in which the target surface is a display surface.
4. 4. A method as claimed in either of claims 1 or 2 in which the target surface is photosensitive, enabling the capture of images projected thereon.
5. 5. A method as claimed in claim 2 in which the motion is periodic.
6. 6. A method as claimed in claim 5 in which the motion is rotation about the axis of the incident light beam.
7. 7. Apparatus for carrying out the method claimed in any of claims 1-6 which comprises a carrier provided with transparent refractive elements, the carrier being disposable around the path of a coherent light beam with at least some surfaces of the elements forming acute angles with the axis of the light beam, means being provided to rotate the carrier about the incident light beam.
8. 8. Apparatus as claimed in claim 7 in which the transparent reflective elements have irregular surfaces.
9. 9'.'App'aratus"'a's"cla'imed"in'either of claims 7 or 8 in" which the transparent reflective elements are plastics sheets.
10. 10. Apparatus as claimed in any of claims 7-9 which further comprises a laser for projecting the coherent light beam.
11. 11. Fixed images (e. g. carried on paper) produced by the process of claim 4.