Device and method for creating an areal light source

• US 5,136,479 A
• Filed: 06/19/1990
• Issued: 08/04/1992
• Est. Priority Date: 06/19/1990
• Status: Expired due to Fees

• Current Assignee: E-Systems LLC
• Original Assignee: E-Systems LLC
• Inventors: Ruffner, Bryan J.
• Primary Examiner(s): Lazarus, Ira S.
• Application Number:
  US07/541,828
• Time in Patent Office: 777 Days
• Field of Search: 350/338, 350/339 D, 350/345, 362/31, 362/800, 362/268, 362/329, 362/330, 362/331, 362/332
• US Class Current: 362/29
• CPC Class Codes: F21V 7/00 Reflectors for light sources characterised by cooling arrangements F21V29/505
• CPC Class Codes: G02F 1/133605 including specially adapted reflectors
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

A device and method to convert light from a point source into an areal source of displayed light. The reflective faces of dielectric mirrors enclose a point source of light. The mirrors repeatedly reflect the light from the point source inside the enclosure without significant absorption, thereby achieving a random distribution of position coordinates for the light rays departing the areal transmissive surface on the outside of the enclosure. The device and method may be used for backlighting a display or for other areal lighting systems.

Claims

1. A device for converting a point source of light into an areal source of light having uniform luminosity comprising:

(a) a point source of light for emitting light having a predominant wavelength;

(b) plural substrates substantially enclosing said point source of light in a cavity, one of said substrates being uniformly optically transmissive for providing said areal source of light, said cavity being substantially enclosed so that light is not emitted therefrom except from said optically transmissive substrate; and

(c) plural layers of optical coating materials carried by the cavity-forming interior surface of each of said substrates, said plural layers having alternating high and low indices of refraction for forming dielectric mirrors so that light from said light source is reflected from and refracted by said plural layers a plural number of times so as to be distributed uniformly on said optically transmissive substrate before being emitted therefrom, said optically transmissive substrate carrying uniformly thereon fewer of said plural layers than the other said substrates so as to be optically transmissive,

each of said plural layers having a thickness less than said predominant wavelength so as to reduce absorption,

whereby light from said point source emanates generally uniformly rom said optically transmissive substrate.

2. The device as defined in claim 1 wherein each of said plural layers has a thickness approximately equal to one-half of said predominant wavelength.

3. The device as defined in claim 1 wherein the ratio of indices of refraction of adjacent ones of said plural layers is at least 1.5.

4. The device as defined in claim 3 wherein at least one of said plural layers is metallic.

5. The device as defined in claim 1 wherein at least one of said plural substrates is folded over the edge of said optically transmissive substrate.

6. The device as defined in claim 1 wherein said substrates are adapted for forming a curved shape.

7. The device as defined in claim 1 wherein said substrates substantially enclose said point source of light in a gas-filled cavity.

8. The device as defined in claim 1 wherein said substrates substantially enclose said point source of light in an evacuated cavity.

9. The device as defined in claim 1 wherein said point source of light is a light emitting diode.

10. A device for providing uniform backlighting with light of a predetermined wavelength, comprising:

(a) a substantially transparent substrate;

(b) plural substantially non-light absorbing layers covering the surfaces of said substrate, said plural layers having alternating high and low indices of refraction so that said substrate is substantially enclosed by dielectric mirrors and so that light within said substrate is reflected and refracted by said layers so as to be uniformly distributed on an outermost one of said layers on a light transmissive exterior surface,

said substrate having a surface with sufficient of said plural layers arrayed uniformly thereon to form said light transmissive exterior surface; and

(c) a light source for emitting light of said wavelength disposed within said substrate,

whereby light from said light source emanates uniformly from said light transmissive surface to provide backlighting.

11. The device as defined in claim 10 wherein each of said plural layers has a thickness approximately one-half of said wavelength.

12. A backlighting device comprising plural dielectric mirrors, a first one of which comprises plural layers of uniformly arrayed optical coating materials, said mirrors substantially enclosing a point source of light so that light from said point source is reflected and refracted by said mirrors so as to be uniformly distributed on an external surface of said first one of said mirrors.

13. A method of converting a source of light into an areal source of light comprising the steps of:

(a) positioning a point source of light in a cavity substantially enclosed by plural substrates;

(b) applying plural layers of optical coating materials to the cavity-facing surfaces of said substrates to form dielectric mirrors so that light form said point source is reflected and refracted by said mirrors so as to provide a uniform distribution of light on an exterior areal surface of one of said substrates when said point source is emitting light, said one substrate having a uniform number of said layers applied thereto; and

(c) allowing light from said source to emanate from said exterior areal surface of said layered substrate so that an areal light source of uniform is provided.

14. A method for converting light of a predetermined wavelength emitting form a point source into light uniformly emanating from an area comprising the steps of:

(a) forming a cavity with the facing mirrored surfaces of plural spaced-apart dielectric mirrors, said dielectric mirrors having plural layers of coatings, each of said layers being one-half said wavelength thick;

(b) positioning a low-power point source of light at said wavelength within said cavity; and

(c) reflecting light from said light source from a first one of said dielectric mirrors having a uniform number of said layers and partially from a second one of said dielectric mirrors, and radiating light from an area formed with the external surface of said second one of said dielectric mirrors.

15. A method of backlighting a display comprising the steps of:

(a) substantially enclosing a point source of light with one or more dielectric mirrors so that light from said point source reflects from the reflective faces of said dielectric mirrors, said dielectric mirrors having uniformly applied plural layers of optical coating materials; and

(b) emanating the light from said point source from a surface of said dielectric mirrors not facing said point source whereby the display is backlift by the emanated light.

16. A device for converting a point source of light into an areal source of light comprising:

(a) a point source of light;

(b) plural substrates substantially enclosing said point source of light, one of said substrates being optically transmissive for providing said areal source of light; and

(c) plural layers of uniformly applied optical coating materials carried by the surfaces of said substrates, said plural layers having alternating high and low indices of refraction for forming dielectric mirrors so that light from said point source of light is reflected and refracted by said plural layers so as to be uniformly distributed on said optically transmissive substrate,

wherein the number of said plural layers on said one optically transmissive substrate enables transmission of light therethrough, and

wherein the number of said plural layers on the other of said substrates is sufficient to enable reflection of substantially all light impinging thereon,

whereby light from said point source emanates generally uniformly from said light transmissive surface.

17. The device as defined in claim 16 wherein said point source of light is adapted to emit light of a predetermined wavelength and wherein each of said plural layers has a thickness approximately equal to one-half of said predetermined wavelength.

18. The device as defined in claim 16 wherein the ratio of indices of refraction of adjacent ones of said plural layers is at least 1.5.

19. A device for backlighting with light of a predetermined wavelength comprising:

(a) plural dielectric mirrors forming a substantially enclosed cavity, one of said mirrors having a light transmissive external surface, each of said mirrors having a reflective surface facing said cavity, and each of said mirrors comprising plural uniformly applied layers of optical coating materials with each of the layers having a thickness approximately equal to one-half said predetermined wavelength and wherein the ratio of indices of refraction of adjacent ones of said layers is at least 1.5; and

(b) a point source of light disposed within said cavity,

wherein said one mirror having a light transmissive external surface comprises fewer of said plural layers than the other said mirrors so as to enable transmission of light therethrough,

whereby light form said source of light emanates uniformly from said external surface.

20. A device for providing uniform backlighting with light of a predetermined wavelength, comprising:

(a) a substantially transparent substrate;

(b) plural layers covering the surfaces of said substrate, said plural layers having alternating high and low indices of refraction so that said substrate is substantially enclosed by dielectric mirrors,

said substrate having plural surfaces with sufficient of said plural layers to reflect substantially all light impinging thereon and at least one light transmissive surface with sufficient of said plural layers uniformly applied to enable transmission of light therethrough; and

(c) a light source for emitting light of said wavelength disposed within said substrate,

whereby light from said light source emanates uniformly from said light transmissive surface to provide backlighting.

21. The device as defined in claim 20 wherein each of said plural layers has a thickness approximately equal to one-half of said predetermined wavelength.

22. The device as defined in claim 20 wherein the ratio of indices of refraction of adjacent ones of said plural layers is at least 1.5.

23. A method of converting a source of light into an areal source of light comprising the steps of:

(a) positioning a point source of light in a cavity substantially enclosed by plural substrates;

(b) uniformly applying plural layers of optical coating materials to the cavity-facing surfaces of said substrates to form dielectric mirrors, wherein the number of said plural layers is sufficient to enable light to be transmitted through one of said substrates and is sufficient to reflect substantially all light impinging on the other said substrates; and

(c) allowing light from said source to emanate from an exterior areal surface of said one light transmissive substrate so that an areal light source of uniform intensity is provided.

24. The method as defined in claim 23 wherein said point source of light is adapted to emit light of a predetermined wavelength and wherein each of said plural layers has a thickness approximately equal to one-half of said predetermined wavelength.

25. The device as defined in claim 23 wherein the ratio of indices of refraction of adjacent ones of said plural layers is at least 1.5.