POINTER GAUGE ILLUMINATION

1 . An illuminated display assembly comprising:

a user display for providing information to a user, wherein the user display includes a display medium and a movable display device having an indicator pointer for providing to the user a position indication on the display medium; and

an illumination source emitting an optical radiation for illuminating the indicator pointer and the display medium, wherein the movable display device includes a light pipe arranged to receive and convey the optical radiation from the illumination source, the light pipe having a dispersing feature arranged to disperse from the light pipe a first portion of the optical radiation to provide back illumination of the display medium and a second portion of the optical radiation conveyed by the light pipe to provide illumination of the indicator pointer.

2 . The illuminated display assembly according to claim 1 , further comprising at least one light diffuser disposed adjacent the display medium, wherein the at least one light diffuser is positioned to receive and diffuse at least a part of the first portion of the optical radiation.

3 . The illuminated display assembly according to claim 2 , wherein the at least one light diffuser is arc-shaped and has a concave diffusing surface.

4 . The illuminated display assembly according to claim 1 , wherein the illumination source is a single light source.

5 . The illuminated display assembly according to claim 1 , wherein the illumination source is a solid state light source.

6 . The illuminated display assembly according to claim 1 , wherein the illumination source includes a single light emitting diode.

7 . The illuminated display assembly according to claim 1 , wherein the illumination source is substantially centrally positioned with respect to the display medium.

8 . The illuminated display assembly according to claim 1 , wherein the light pipe includes a substantially transparent solid material defining an external wall of the light pipe, the optical radiation conveyed by the light pipe constrained within the light pipe by total internal reflection by the external wall, and wherein the dispersing feature is a shape of the external wall of the light pipe which permits the first portion of the optical radiation to be transmitted through the external wall.

9 . The illuminated display assembly according to claim 8 , wherein the shaping of the external wall creates a constriction in cross-sectional area of said light pipe in a plane transverse to the direction in which the optical radiation is conveyed within the light pipe.

10 . The illuminated display assembly according to claim 8 , wherein the shape of the external wall includes at least one step.

11 . The illuminated display assembly according to claim 1 , wherein the light pipe includes a substantially transparent solid material defining an external wall of the light pipe, the optical radiation conveyed by the light pipe constrained by the light pipe by total internal reflection with the external wall, and wherein the dispersing feature is a texturing of the external wall of the light pipe which permits the first portion of the optical radiation to be transmitted through the external wall.

12 . The illuminated display assembly according to claim 1 , wherein the light pipe is formed as a unitary structure with the indicator pointer.

13 . An illuminated display assembly comprising:

a user display for displaying information to a user, wherein the user display includes a display medium and a movable display device having an indicator pointer for providing to the user a position indication on the display medium; and

an illumination source emitting an optical radiation for illuminating the indicator pointer and the display medium, wherein the movable display device includes a light pipe arranged to receive and convey the optical radiation from the illumination source, the light pipe having a dispersing feature arranged to disperse from the light pipe a first portion of the optical radiation to provide back illumination of the display medium and a second portion of the optical radiation conveyed by the light pipe to provide illumination of the indicator pointer; and

a motive means for rotationally moving the movable display device about a rotational axis, wherein the light pipe extends along the rotational axis.

14 . The illuminated display assembly according to claim 13 , further comprising at least one light diffuser disposed adjacent the display medium, wherein the at least one light diffuser is positioned to receive and diffuse at least a part of the first portion of the optical radiation.

15 . The illuminated display assembly according to claim 14 , wherein the at least one light diffuser is arc-shaped and has a concave diffusing surface.

16 . The illuminated display assembly according to claim 13 , wherein the motive means and the illumination source are mounted on a common circuit board.

17 . The illuminated display assembly according to claim 13 , wherein the light pipe is a rotational shaft of the movable display device, the shaft adapted to be rotated by the motive means.

18 . The illuminated display assembly according to claim 13 , wherein the first portion of the optical radiation is dispersed radially outwards around the rotational axis to provide the back illumination of the display medium.

19 . The illuminated display assembly according to claim 18 , wherein the display medium has display indicia arranged around the rotational axis, the display indicia being back illuminated by the first portion of the optical radiation.

20 . A method of providing diffuse backlit illumination to a display assembly, the display assembly including a user display having a display medium and a movable display device, wherein the moveable display device includes an indicator pointer, a source of optical radiation for backlighting the user display, and a light pipe having a dispersing feature, the method comprising the steps of:

using the source of optical radiation to generate the optical radiation;

projecting from behind the user display the optical radiation into the light pipe;

conveying the optical radiation within the light pipe;

using the dispersing feature of the light pipe to disperse a first portion of the optical radiation out of the light pipe;

using the dispersed first portion of the optical radiation to back illuminate the display medium; and

conveying within the light pipe a second portion of the optical radiation remaining after the dispersing of the first portion to illuminate the indicator pointer.