GB2205673A - Light display generator for audio apparatus - Google Patents

Abstract

Audio reproduction apparatus is provided with a light display generator 18 and a ground glass screen 17 onto which a changing light display 35 is projected. The light display generator comprises a laser light source 20, first and second mirrors 29, 30 and motors 23, 24 for rotating them about axes at acute angles to their reflecting surfaces. The laser beam is directed at the first mirror 29 at positions offset from its axis of rotation. A cone of light 34 is thus reflected by the first mirror to the second mirror 30. Rotation of the second mirror results in a Lissajous-like pattern of light to be reflected by the second mirror and displayed on the screen. The pattern can be varied by controlling the speed of the two motors at random. A bounce mirror 27 projects the display on to the back of the screen 17 or on to a wall of a room when the screen is hinged open. <IMAGE>

Description

1IGHT DISPLAY GENERATOR FOR AUDIO APPARATUS This invention relates to audio apparatus, and more particularly to the provision of a light display generator in such apparatus, and to a light display generator per se.

Various display systems have been developed in the field knon as visual music. Many of these systems include mirrors mounted on speakers for reflecting light directed at the mirrors. However, these systems rely on vibration of the speakers to generate changes in the light displays.

It is an object of the invention to provide a light display generator for producing a light pattern which can be displayed on a screen.

According to a preferred aspect of the invention there is provided audio apparatus having a light display generator comprising: first means for providing a narrow beam of light; a first light reflector having a reflecting surface; second means for rotating the first light reflector about an axis which is at an acute angle to the reflecting surface of the first light reflector; the first light reflector being arranged so that the narrow beam of light is reflected from its reflecting surface at positions offset from said axis; a second light reflector having a reflecting surface arranged to receive and reflect the light reflected from the first light reflector; and third means for rotating the second light reflector about an axis which is at an acute angle to the reflecting surface of the second light reflector.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of one embodiment of audio apparatus according to the invention; and Figure 2 is an enlarged plan view of a light display generator contained within the audio apparatus of Figure 1.

Referring to the drawings, the audio apparatus shown in Figure 1 is a portable audio tape reproducing apparatus and radio receiver 10, having twin tape decks 11 and 12, a tuner 13, a graphic equalizer 14 and loudspeakers 15 and 16. The apparatus shown in Figure 1 also has a translucent viewing screen 17 which closes a compartment interposed between the two speakers 15 and 16. The screen 17 is of ground glass and is hinged at its lower end to the frame of the apparatus.

The compartment behind the screen 17 houses a light display generator 18, shown in Figure 2. The generator 18 comprises a mounting plate 19 supported vertically in the said compartment. The mounting plate 19 carries a laser light source 20, fixed to the plate 19 by plastics laser mounts 21, a high voltage laser supply 22, two fractional horsepower permanent magnet direct current electric motors 23 and 24 of a type commercially available, fixed to the plate 19 by plastic motor mounts 25 and 26, respectively, a final bounce mirror 27 and a control circuit 28 for the motors. All electrical connections between the various components are provided at the rear of the mounting plate 19.

First and second light reflectors in the form of planar mirrors 29 and 30 are mounted on shafts 31 of the two motors 23 and 24, respectively, for rotation thereby. The mirrors 29 and 30 are glued to mirror mounts, each in the form of a bush 32 which is press fitted on the end of a respective motor shaft 31 and which has a mirror mounting surface which is at an acute angle, typically 750, to the axis of the motor shaft.

The motors 23 and 24 are, as shown, arranged with their axes parallel and, typically, at an angle of 400 to the axis of the laser tube 20.

The motor 23 is positioned relative to the laser light source 20 so that a laser beam 33 emitted by the laser light source 20 strikes the mirror 29 at positions offset from the axis of the motor shaft 31. Thus as the motor 23 rotates the mirror 29 reflects the beam 33 and produces what resembles a cone of light 34 due to the changing angle of incidence of the beam 33 with the mirror 29.

The motor 24 is positioned relative to the motor 23 so that the cone 34 of light falls on the mirror 30.

The changing angle of incidence of the cone of light 34 with the mirror 30 has the result that a light pattern 35, resembling a Lissajous figure, is reflected by the mirror 30 onto the final bounce mirror 27 which in turn reflects this pattern onto the rear surface of the screen 17.

The control circuit 28 is of a type which is well known in the art and varies the speed and direction of the motors 23 and 24 in a random manner to continually change the display projected onto the rear surface of the screen 17.

As mentioned previously, the screen 17 is hinged at its lower end to the frame of the apparatus and can be opened to allow the display to be projected, for example, onto a wall of a room.

Typically, the distance from the laser tube 20 to the mirror 29 is 0.550 inches (1.4 cms), the distance from the mirror 29 to the mirror 30 is 0.750 inches (1.9 cms) and the distance from the mirror 30 to the bounce 27 is 0.600 inches (1.5 cms). However, these measurements are not at all critical.

The embodiment described above is given by way of example only and various modifications will be apparent to persons skilled in the art without departing from the scope of the invention defined by the appended claims. For example, one or more additional mirrors, together with associated drive motors, could be interposed in the light path between the mirror 30 and the bounce mirror 27. Moreover, the light display generator 18 could be provided in an appropriate home audio system rather than in a portable system and, indeed, could be provided quite independently of audio equipment.

Claims (10)

Claims

1. Audio apparatus having a light display generator comprising: first means for providing a narrow beam of light; a first light reflector having a reflecting surface; second means for rotating the first light reflector about an axis which is at an acute angle to the reflecting surface of the first light reflector; the first light reflector being arranged so that the narrow beam of light is reflected from its reflecting surface at positions offset from said axis; a second light reflector having a reflecting surface arranged to receive and reflect the light reflected from the first light reflector; and third means for rotating the second light reflector about an axis which is at an acute angle to the reflecting surface of the second light reflector.

2. Audio apparatus as claimed in claim 1, further comprising a screen for receiving a light pattern produced by the light display generator.

3. Audio apparatus as claimed in claim 2, wherein said screen is translucent and receives said light pattern by back projection.

4. Audio apparatus as claimed in any one of claims 1 to 3, wherein said first means is a laser.

5. Audio apparatus as claimed in any one of claims 1 to 4, wherein said second and third means are electric motors.

6. Audio apparatus as claimed in any one of claims 1 to 5, wherein the first and second light reflectors are rotatable about axes which are parallel to one another.

7. Audio apparatus as claimed in any one of claims 1 to 6, further comprising means for varying the speed of rotation of the first and second light reflectors.

8. Audio apparatus substantially as hereinbefore described with reference to the accompanying drawing.

9. A light display generator comprising: first means for providing a narrow beam of light; a first light reflector having a reflecting surface; second means for rotating the first light reflector about an axis which is at an acute angle to the reflecting surface of the first light reflector; the first light reflector being arranged so that the narrow beam of light is reflected from its reflecting surface at positions offset from said axis; a second light reflector having a reflecting surface arranged to receive and reflect the light reflected from the first light reflector; and third means for rotating the second light reflector about an axis which is at an acute angle to the reflecting surface of the second light reflector.

10. A light display generator substantially as hereinbefore described with reference to the accompanying drawing.