Compact Optical System and Lenses for Producing Uniform Collimated Light

• US 20090067170A1
• Filed: 09/06/2007
• Published: 03/12/2009
• Est. Priority Date: 09/06/2007
• Status: Active Grant

• Current Assignee: Signify North America Corporation (Signify N.V.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Bloemen, Pascal J.H., Stassar, Emanuel N.H.J.
• Granted Patent: US 7,967,477 B2
• Time in Patent Office: Days
• US Class Current: 362/235
• CPC Class Codes: F21V 13/04 the elements being reflectors and refractors for vehicle rear lights F21S43/40
• CPC Class Codes: F21V 5/045 the lens having discontinuous faces, e.g. Fresnel lenses
• CPC Class Codes: F21Y 2103/10 comprising a linear array of point-like light-generating elements
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0066 in the form of an LED array
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

An optical system includes a cylindrical side emitter lens, a reflector and a cylindrical Fresnel lens to produce a substantially uniformly illuminated exit plane with well collimated light in the forward direction. The cylindrical side emitter lens redirects light from a light source, such as a number of light emitting diodes placed in a straight line, into side emitted light along an optical axis that is parallel with the exit plane. The reflector may be a stepped multi-focal length reflector that includes multiple reflector surfaces with different focal lengths based on the surfaces distance to the light source and height to redirect light from the cylindrical side emitter lens to illuminate the exit plane and collimate the light along one axis in the forward direction. The cylindrical Fresnel lens is used to collimate the light along an orthogonal axis in the forward direction.

Claims

1. An optical system for producing substantially collimated light in a forward direction, wherein the optical system has a long axis and a short axis that are orthogonal to each other and the forward direction is perpendicular to the long axis and the short axis, the optical system comprising:

at least one light source;

a cylindrical side emitter lens optically coupled to the at least one light source, the cylindrical side emitter lens is configured to redirect a portion of light emitted from the at least one light sources to be side emitted light that is perpendicular to the forward direction and parallel to the long axis;

at least one reflector positioned to receive the side emitted light from the cylindrical side emitter lens and redirect the light substantially in the forward direction, the reflector is configured so that substantially uniform illumination is produced over an exit plane of the optical system and the light is substantially collimated in the forward direction with respect to a plane defined by the forward direction and the short axis; and

a cylindrical Fresnel lens coupled to receive the forward directed light from the at least one reflector, the cylindrical Fresnel lens substantially collimating the forward directed light with respect to a plane defined by the forward direction and the long axis.

2. The optical system of claim 1, wherein there are two reflectors with the cylindrical side emitter lens disposed between the two reflectors.

3. The optical system of claim 1, wherein the at least one light source is a plurality of light sources arranged in a line parallel to the short axis.

4. The optical system of claim 3, wherein the light sources are light emitting diodes.

5. The optical system of claim 1, wherein the cylindrical side emitter lens has a cross sectional shape of a side emitter lens along a plane defined by the forward direction and the long axis and wherein the cylindrical side emitter lens has the same cross sectional shape at every point along the short axis.

6. The optical system of claim 1, wherein the cross sectional shape of the cylindrical side emitter lens comprises a top portion and a bottom portion, the top portion having a “

V”

shape with each arm of the “

V”

shape including a reflecting surface on the inside of the “

V”

shape and a refracting surface on the outside of the “

V”

shape, the bottom portion having a refracting surface that extends as a smooth curve from the refracting surface of the “

V”

shape to a bottom surface, the cross sectional shape of the cylindrical side emitter lens further comprising a cavity in which the light sources are disposed.

7. The optical system of claim 1, wherein the cylindrical Fresnel lens has a cross sectional shape of a Fresnel lens along a plane defined by the forward direction and the short axis and wherein the cylindrical Fresnel lens has the same cross sectional shape at every point along the long axis.

8. The optical system of claim 1, wherein the at least one reflector is at least one stepped multi-focal reflector having multiple reflector surfaces positioned at different distances from the cylindrical side emitter lens and at different heights with respect to the forward direction, the multiple reflector surfaces have different focal lengths that vary based on the distance and height of each reflector surface, wherein the configuration of the focal length, the distance from the cylindrical side emitter lens, and height of each reflector surface produces the substantially uniform illumination over the exit plane of the optical system and substantially collimates the light in the forward direction.

9. The optical system of claim 8, wherein the multiple reflector surfaces are coupled together.

10. The optical system of claim 1, wherein light substantially collimated by the reflector has an angular spread of ±

15 degrees or less and wherein the cylindrical Fresnel lens substantially collimating light produces light with an angular spread of ±

15 degrees or less.

11. The optical system of claim 1, further comprising multiple light sources, cylindrical side emitter lenses, reflectors, and cylindrical Fresnel lenses coupled together.

12. A cylindrical side emitter lens having an optical axis, a horizontal axis that is orthogonal to the optical axis and a central axis that is orthogonal to the optical axis and the horizontal axis, the cylindrical side emitter lens comprising:

a bottom surface, the optical axis being parallel with the bottom surface;

a cavity in which one or more light sources may be positioned; and

a reflecting surface that is a plane;

a first refracting surface that is a plane and is obliquely angled with respect to the central axis of the lens; and

a second refracting surface extending from the bottom surface to the first refracting surface;

wherein light entering the lens from the cavity and directly incident on the reflecting surface is reflected from the reflecting surface to the first refracting surface and refracted by the first refracting surface to exit the lens in a direction substantially parallel with the optical axis; and

wherein light entering the lens from the cavity and directly incident on the second refracting surface is refracted by the second refracting surface to exit the lens in a direction substantially parallel to the optical axis;

wherein the cylindrical side emitter lens has a cross sectional shape along a plane defined by the central axis and the optical axis and has the same cross sectional shape at every point along the horizontal axis.

13. The cylindrical side emitter lens of claim 12;

wherein the second refracting surface extends as a smooth curve from the bottom surface to the first refracting surface.

14. The cylindrical side emitter lens of claim 12;

wherein the cavity is configured to have light emitting diodes positioned inside.

15. The cylindrical side emitter lens of claim 12;

wherein the reflecting surface reflects by total internal reflection.

16. The cylindrical side emitter lens of claim 12;

wherein the reflecting surface is a first reflecting surface, the cylindrical side emitter lens further comprising;

a second reflecting surface that is a plane and that forms a “

V”

shape with the first reflecting surface;

a third refracting surface that is a plane and is obliquely angled with respect to the central axis of the lens; and

a fourth refracting surface extending from the bottom surface to the third refracting surface;

wherein light entering the lens from the cavity and directly incident on the second reflecting surface is reflected from the second reflecting surface to the third refracting surface and refracted by the third refracting surface to exit the lens in a direction substantially anti-parallel with the optical axis; and

wherein light entering the lens from the cavity and directly incident on the fourth refracting surface is refracted by the fourth refracting surface to exit the lens in a direction substantially anti-parallel to the optical axis.

17. A stepped multi-focal length reflector having a first axis and a second axis that is orthogonal to the first axis, the first axis and second axis are parallel with an exit plane, and an optical axis that is orthogonal to the exit plane, the stepped multi-focal length reflector comprising:

multiple reflector surfaces, each reflector surface positioned at a different distance from a light source and positioned at a different height with respect to the optical axis, wherein the reflector surfaces that is closest to the light source has the lowest height on the optical axis and the reflector surface that is farthest from the light source has the greatest height on the optical axis, each reflector surface has a different focal length that is based on the distance of the reflector surface to the light source and on the height of the reflector surface on the optical axis, wherein the configuration of the focal length, distance to the light source and height of each reflector surface receives light from a light source along the first axis and redirects the light along the optical axis to produce substantially uniform illumination over the exit plane and substantially collimate the light along the optical axis.

18. The optical system of claim 17, wherein the multiple reflector surfaces are coupled together.

19. The optical system of claim 17, wherein the substantially collimated light has an angular spread of ±

15 degrees or less.