APPARATUS FOR PROVIDING EVEN, FOCUSED ILLUMINATION OF A TARGET SURFACE

• US 20100246206A1
• Filed: 03/31/2009
• Published: 09/30/2010
• Est. Priority Date: 03/31/2009
• Status: Active Grant

• Current Assignee: Raja Singh Tuli
• Original Assignee: Raja Singh Tuli
• Inventors: Tuli, Raja Singh
• Granted Patent: US 8,038,335 B2
• Time in Patent Office: Days
• US Class Current: 362/551
• CPC Class Codes: G02B 6/002 by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces
• CPC Class Codes: G02B 6/0043 provided on the surface of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]

Abstract

The present invention discloses improvements on an apparatus for reading a document by illuminating it with a beam of focused light, directing the reflected light to an array of optical sensors, digitalizing the resulting image and storing it for future use. It discloses several aspects of the light pipe element aimed at improving the illumination of the targeted area for the aforementioned purpose, including the shape of the light pipe ends, the use of a refracting coat on the back of the light pipe and the shaping of the light pipe front surface to focus the light rays on the target surface.

Claims

1. Apparatus for providing even, focused illumination of a target surface comprising a longitudinally straight, elongate light pipe made of a transparent material, with light sources disposed at least on one end;

a cross-section that is constant in a central region and tapers towards at least one end, wherein the rate of the cross-section reduction of the tapering portion is selectively adjusted to cause total internal reflection of a higher proportion of the plurality of light rays that originate from the light source than would be the case with a constant cross section.

2. Apparatus according to claim 1, wherein the light pipe has a substantially circular cross-section.

3. Apparatus for providing even, focused illumination of a target surface comprising a longitudinally straight, elongate light pipe made of a transparent material featuring a certain refraction index, with light sources disposed at least on one end, a first surface painted with a refractive coating and a second surface, opposite to the first surface and facing the target surface, wherein the proportion of light rays incident on the first surface from the inside of the light pipe that are either reflected or refracted back inside the light pipe towards the second surface for contributing to the illumination of the target surface is increased by making the first surface substantially concave instead of flat.

4. Apparatus according to claim 3, wherein the light reflective coating strip applied to the first substantially concave surface extends longitudinally from end to end of the light pipe.

5. Apparatus for providing even, focused illumination of a target surface comprising a longitudinally straight, elongate light pipe made of a transparent material featuring a certain refraction index, with light sources disposed at least on one end;

wherein the surface of the light pipe, specifically in the region from where the light rays are to emerge towards the target surface, has its shape selectively adjusted to act as a focusing lens for illuminating the target surface.

6. Apparatus according to claim 5, wherein the focusing lens is shaped to yield a cross-sectional pattern of light distribution with a plateau shape, yielding a band of evenly distributed light covering a strip between 0.5 and 4 mm wide on the target surface.