There are various known methods for beam steering which are employed in projection devices. For example WOt99/41544 discloses a double-mirror system, mounted in front of a projector, which is able to direct a light beam to any chosen area of a screen or stage set. However, there are now requirements for wider-angle projection beams than can easily be provided by known systems, or at least, systems with a compact structure.

It is an object of the present invention to address these problems, and to provide an improved beam steering device, which is also more compact and more cost efficient.

Accordingly,'the invention provides, in one aspect, apparatus for steering a light beam, adapted to receive a light beam along a light'beam axis from a light beam source, and comprising: a first reflector for reflecting the light beam along an intermediate beam axis; a first bearing for allowing rotation of the first reflector about the axis of the light beam; a support arm being rotatable around the axis of the light beam in conjunction with the rotation of the first reflector ; and a second reflector, mounted on the support arm, for reflecting the light beam directed along the intermediate beam axis by the first reflector; and a second bearing for allowing rotation of the second reflector about the intermediate beam axis, wherein the first bearing is disposed on the opposite side of the first reflector to the light beam.

This apparatus therefore does not require the use of a bearing which has a bore large enough to permit the light beam to pass through it. The absence of a cumbersome bearing allows a cheaper and more compact device.

Advantageously, the first reflector is mounted on the support arm.

Preferably, the support arm extends in a plane which intersects the path of the beam from the light source to the first reflector. More preferably, the support arm comprises an aperture for permitting the light beam to pass through.

Suitably, the first reflector is fixed with respect to the support arm.

In one form of the invention, the first bearing comprises a motor for driving the rotation of the first reflector. This allows a still more compact device, and greater rigidity, as the bearing support for the rotation is providedbythe drive means.

In another form of the invention the rotation of the first reflector is driven by means of a pulley arrangement coupled to the bearing, which pulley arrangement driven by a motor. This arrangement allows the bearing for rotation of the first mirror to be smaller, which in turn allows a wider angle for, the beam from the second mirror.

In a further aspect, the invention consists in apparatus for steering a light beam which is adapted for association with a light beam source, the light beam source defining a light beam axis and a beam exit plane, orthogonal to said axis, the apparatus comprising an exit reflector which is rotatable bodily about the light beam axis; an intermediate reflector positioned on the beam axis and rotatable so as always to reflect the light beam towards the exit reflector along an intermediate beam axis, the exit reflector being rotatable about the intermediate beam axis; and a drive arrangement for the intermediate and exit reflectors to steer the light beam along a desired exit beam direction, wherein the bodily rotation of the exit reflector about the light beam axis is provided through a support which intersects the light beam axis, that region of the support which intersects the light beam axis lying substantially wholly in a plane parallel to said beam exit plane and between said beam exit plane and the intermediate reflector.

The support arm therefore does not occlude the light beam at any point on its path through the device, permitting a more compact apparatus.

Preferably, in extending from the light beam axis to the exit reflector the support extends substantially behind the beam exit plane. More preferably, at least a portion of the exit reflector extends substantially behind the beam exit plane, whereby at least a portion of the light beam directed along the intermediate beam axis traverses the beam exit plane.

Thus, the apparatus is advantageously compact, allowing a wider angle projection beam. The angle of divergence accommodated by the device of the present invention is preferably at least 20°, more preferably at least 30° and still more preferably at least 40°.

In another aspect, the invention consists m, apparatus for steering a light beam which'is adapted for association with a light beam, source, the light beam <BR> <BR> source defining a light beam axis and a beam exit plane, orthogonal to said axis,<BR> i, the apparatus comprising an exit reflector which is rotatable bodily about the light beam axis; an intermediate reflector positioned on the beam axis and rotatable so as always to reflect the light beam towards the exit reflector along an intermediate beam axis, the exit reflector being rotatable about the intermediate beam axis; and a drive arrangement for the intermediate and exit reflectors to ,,,, steer the light beam along a desired exit beam direction, wherein the exit reflector intersects the beam exit plane, whereby at least a portion of the light beam directed along the intermediate beam axis traverses the beam exit plane.

Advantageously, the bodily rotation of the exit reflector about the light beam axis is provided through a support lying between said beam exit plarie and the intermediate reflector, which support extending substantially behind the beam exit plane.

Suitably, the intermediate reflector is carried on the support.

In a yet further aspect, the invention provides apparatus for steering a light beam which is adapted for association with a light beam source, the light beam source defining a light beam axis and a beam exit plane, orthogonal to said axis, the apparatus comprising an exit reflector which is rotatable bodily about the light beam axis; an intermediate reflector positioned on the beam axis and rotatable so as always to reflect the light beam towards the exit reflector along an intermediate beam axis, the exit reflector being rotatable about the intermediate beam axis; and a drive arrangement for the intermediate and exit reflectors to steer the light beam along a desired exit beam direction, wherein the bodily rotation of the exit reflector about the light beam axis is provided through a support lying between said beam exit plane and the intermediate reflector, which

support being rotatable on a bearing disposed on the opposite side of the intermediate reflector to that side reflecting the light, beam The invention will now be described by way of example with, reference to the accompanying drawings, in which : Fig, ure 1 is a side view of a beam steering device according to one embodiment of the present invention : Figures 2 and 3 are end and top views respectively at the device of Figure 1, with certain parts shown in outline to improve visibility of interior components.

Figure 4 is a side view of a device according to another embodiment of the invention.

A first embodiment of the invention provides a motorized double-mirror beam steering device, as shown in Figures 1,2 and 3. An objective lens (105) of a light beam source is housed in a frame (103). The frame extends in a C-shape, having a lower limb housing the lens, and an upper limb housing a motor (101) having a drive shaft (126). A contoured support arm (104) is mounted on the upper limb of the frame by means of the motor drive shaft 126, which lies in the light beam axis, such that the arm may be rotated bodily about the axis (124) of the light beam. The arm extends along the upper limb of the frame, around the C- shape, along the lower limb, and includes an aperture (128) so as not to occlude the light beam. The arm then extends a distance away from the frame and lens arrangement, intersecting the plane of the front surface of the lens, or beam exit plane, so that a portion of the arm is behind this plane.

A first mirror (106) is fixed on the arm, with its reflecting face opposing the lens, such that it rotates with the arm around the axis of the light beam. The mirror is mounted at an angle of around 45° to the axis of the light beam, so as to reflect the light beam towards a second mirror (107).

A second motor (102) is attached to that end of the support arm extended away from the frame. A drive shaft 130 extends from the second motor aiong an axis (132) orthogonal to the axis of the original light beam, and carries the second mirror (107).

A rotation of both mirrors around their respective axes permits projection of the light beam in almost any direction around the device; the path of the light beam through the device is indicated by the lines 120.

The principal advantage of this device is that it permits a very wide angle projection beam. The beam diverges significantly from the lens (105), and <BR> <BR> diverges further on reflection from the first mirror (the second mirror being in this<BR> example at least twice the diameter of the first mirror), and, still further on reflection from the second. Thus, in a relatively short distance from the projector, the beam may cover a substantial area of a screen, stage set, or other projection surface. This divergence is accommodated by several factors.

The first mirror is located close to the lens ; if the mirror were further away, as in prior devices, it would have to be very large in order to reflect the full width of the beam. The second mirror is, in this embodiment mounted as close to the first mirror as the beam geometry will allow, overcoming previous problems of an intermediate bearing aperture or structure. Even so it is significantly larger than the first, due to the divergence, but would be required to be far larger, were the first mirror at a significant distance from the lens. The proximity of the first mirror to the lens is permitted by the orientation of the support arm (104), which is situated in the beam exit plane and extends behind that plane so as not to occlude the light reflected between the mirrors, and by the fact that no large bearing is required to rotate the second mirror. The rotation is simply performed by means of the shaft (130) (and motor) to which the mirror (104) is attached.

Furthermore, the bearing is removed from the path of the light beam, and situated behind the first mirror, so that the mirror can be positioned even closer tc the lens.

The cranked orientation of the support arm also allows part of the second mirror to occupy the space behind the plane of the front surface of the lens. This

in turn allows the first mirror to be positioned closer to the lens, as the light reflected from it may occupy a wider angle. If the support arm were simply directed horizontally from the frame, the angle of the beam from the first mirror would be restricted to the space defined by the support arm. If the second mirror were not positioned with part of it behind the lens, the first mirror would have to' be further from the lens, in order for the second mirror to reflect the full width of the beam.

There is also a further advantage in the motor providing the bearing support for the support arm and first mirror fixed to, the support arm; as no separate bearing is required, the device may be manufactured more cheaply, and also, the integration of the motor and bearing lends greater rigidity to the device.

In the embodiment shown in Figures 1-3, the arm may not actually perform a full 360° rotation, as it will be impeded by the frame. In an alternative embodiment, the U-shape of the frame extends far enough away from the axis of the light beam (and thus the axis of rotation of the support arm) that the arm is permitted to rotate through the full 360°. The second mirror may be impeded in its rotation by the arm in rotating, and thus, similarly, the arm may take different shapes to allow the second mirror to perform a full rotation.

In an alternative embodiment, illustrated in Figure 4, the motors 201 and 202 are both enclosed within the shape formed by the C-shape of the frame (203). Here, the motors do not provide the bearing support, as separate bearings are provided for the first and second mirrors. The first mirror (206) is rotated by means of the first motor (201) and a first belt and pulley set (208) which rotates the shaft (226) on the first bearing (210), which is situated in place of the motor in the above embodiment. The second mirror (207) is rotated by means of the second motor (202) and the second belt and pulley set (209) rotating the shaft (230) on the second bearing (240). Other drive linkages could of course be used in place of belt and pulley arrangements.

in this embodiment, the motors act to counterbalance the weight of the second on the support arm, allowing the freer rotation of the first mirror and attached arm arrangement.

Another advantage of this type of arrangement is that the first motor cannot now interfere with the beam exiting the apparatus; the first bearing is typically much smaller than a motor.

' In alternative embodiment, the different positions of the motors, bearings and drive systems may be substituted for one another. For example, the rotation of the second mirror may be performed by a motor and bearing behind the mirror, as in Figure 1, with the rotation of the support arm and first mirror performed by the motor, and drive system of Figure 2. Of course, the opposite alternative is also possible.

Both of the main embodiments described have a further advantage over prior implementations in that, as the first bearing (or motor providing the bearing support) is located on the opposite side of the first mirror to that reflecting the light beam, there, is no requirement-for a-bearing large enough to permit the light beam through its bore. This entails that the device is cheaper, as no large bearing is required, and that the device is more compact, allowing a wider angle of projection beam.

In one arrangement of the embodiments described, the device is a wholly separate piece of apparatus, which may be mounted on any projector or light source. In another arrangement, the device is manufactured to be integral to a projector or light source. The projector may include a video or graphics projector.

It will be appreciated by those skilled in the art that the invention has been described by way of example only, and a wide variety of alternative approaches may be adopted.