Method and apparatus for producing a uniform irradiance distribution from an array of light emitting diodes

• US 8,430,526 B2
• Filed: 08/29/2008
• Issued: 04/30/2013
• Est. Priority Date: 08/29/2008
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Inventors: Gigioli, George William Jr.
• Primary Examiner(s): CARIASO, ALAN B
• Application Number:
  US12/201,358
• Publication Number:
  US 20100053979A1
• Time in Patent Office: 1,705 Days
• Field of Search: 362/27, 362 61-613, 359385-390
• US Class Current: 362/244
• CPC Class Codes: G02B 19/0014 at least one surface having optical power
• CPC Class Codes: G02B 19/0066 in the form of an LED array
• CPC Class Codes: G02B 19/0095 for use with ultraviolet radiation
• CPC Class Codes: G02B 27/0961 Lens arrays lens arrays per se G02B3/0006

Abstract

An apparatus and method for producing a spatially uniform irradiance in an image plane are provided. The apparatus includes an array of light emitting diodes (LEDs) which generate light (i.e., an image). The apparatus combines the outputs of an array of the LEDs in such a way as to produce a spatially uniform irradiance in an image plane some distance away. The apparatus includes an array of lenslets to form images of the emitting areas of the individual LEDs. The lenslets have a magnification, size and spacing such that the images produced by the respective LEDs are adjacent to one another and not overlapping. The irradiance distribution in the image plane is equivalent to an image of an LED whose emitting area is equal to the total area of the LED array, and whose total power is equal to the total power of the LEDs in the LED array.

Claims

1. An apparatus comprising:

one or more light emitting diodes (LEDs) arranged in one or more rows and columns of an LED array, each LED being configured to emit one or more rays of light;

one or more lenslets arranged in one or more rows and columns of a lenslet array, each lenslet is configured to receive the one or more rays of light emitted from only one respective LED of the one or more LEDs, each of the one or more lenslets is configured to distribute the one or more rays of light and emit the distributed one or more rays of light; and

an illumination plane comprising a biological agent or a chemical agent for receiving the distributed one or more rays of light in one or more areas arranged in one or more rows and columns of an array such that each area is entirely and uniformly illuminated by the distributed one or more rays of light that form one or more images that abut each other.

2. The apparatus according to claim 1, wherein each of the lenslets distribute the one or more rays of light with a magnification factor given by m=s_i/s₀, where s₀ is a distance from the LED array to the lenslet array and s_i is a distance from each of the one or more lenslets to the illumination plane.

3. The apparatus according to claim 2, wherein the distance from each of the one or more lenslets to the respective area is defined by s_i=s₀×

f/(s₀−

f), where f is a focal length of a respective one of each of the one or more lenslets.

4. The apparatus according to claim 3, wherein each of the focal lengths of the one or more lenslets is substantially the same.

5. The apparatus according to claim 3, wherein each of the one or more areas correspond to a respective lenslet and a respective LED.

6. The apparatus according to claim 1, wherein the one or more images comprises a composite image, the composite image has a power equal to an aggregate total power of the one or more LEDs in the LED array times the optical throughput of the lenslet array.

7. The apparatus according to claim 1, wherein the one or more LEDs comprise an emitting area and an aggregate emitting area of all of the one or more LEDs is equal to a total area of the LED array.

8. The apparatus according to claim 1, wherein the one or more images that abut each other have no unilluminated gaps therebetween.

9. The apparatus according to claim 1, wherein each of the lenslets uniformly illuminate each area of the illumination plane by illuminating a respective area of the one or more areas forming a first image among the one or more images which does not substantially illuminate another area of the one or more areas forming a second image among the one or more images.

10. The apparatus of claim 1, wherein each of the light emitting diodes correspond to respective ones of the lenslets.

11. The apparatus of claim 1, wherein each of the one or more lenslets is configured to distribute the one or more rays of light by at least one of reflecting, refracting or diffracting the light.

12. The apparatus of claim 1, wherein in response to the biological agent or chemical agent being illuminated by the light, the biological agent or the chemical agent is configured to fluoresce at a wavelength that is different from a wavelength of the light.

13. A method comprising:

emitting one or more rays of light from respective ones of one or more light emitting diodes (LEDs) arranged in one or more rows and columns of an LED array;

receiving the one or more rays of light, emitted from the respective ones of the LEDs, at one or more lenslets arranged in one or more rows and columns of a lenslet array, wherein each of the lenslets receive the light emitted from only one respective LED of the LEDs;

distributing the one or more rays of light, at each of the one or more lenslets;

transmitting, at each of the one or more lenslets, the distributed one or more rays of light; and

receiving the one or more distributed rays of light at a respective area of an illumination plane comprising a biological agent or a chemical agent and one or more areas arranged in one or more rows and columns of an array, each of the one or more areas receives the distributed one or more rays of light from a respective lenslet and illuminates each area of the one or more areas entirely and uniformly, with the distributed one or more rays of light, forming one or more images that abut each other.

14. The method according to claim 13, wherein distributing comprises distributing the one or more rays of light at each of the one or more lenslets by magnifying the distributed one or more rays of light with a magnification factor given by m=s_i/s₀, where s₀ is a distance from the LED array to the lenslet array and s_i is a distance from a light emitting surface of each of the one or more lenslets to the illumination plane.

15. The method according to claim 14, further comprising defining the distance from the light emitting surface of each of the one or more lenslets to the respective area is defined by s_i=s₀×

f/(s₀−

f), where f is a focal length of a respective one of each of the one or more lenslets.

16. The method according to claim 15, wherein each of the focal lengths of the one or more lenslets is substantially the same.

17. The method according to claim 16, wherein each of the one or more areas correspond to a respective lenslet and a respective LED.

18. The method according to claim 13, wherein each of the one or more images comprises a composite image, the composite image has a power equal to an aggregate total power of the one or more LEDs in the LED array times the optical throughput of the lenslet array.

19. The method according to claim 13, wherein each of the one or more LEDs comprises an emitting area and an aggregate emitting area of all of the one or more LEDs is equal to a total area of the LED array.

20. The method according to claim 13, wherein illuminating further comprises the one or more images that abut each other having no unilluminated gaps therebetween.

21. The method according to claim 13, wherein illuminating further comprises illumination of a respective area of the one or more areas forming a first image among the one or more images which does not substantially illuminate another area of the one or more areas forming a second image among the one or more images.

22. The method of claim 13, wherein each of the light emitting diodes corresponds to respective ones of the lenslets.

23. The method of claim 13, wherein each of the one or more lenslets is configured to distribute the one or more rays of light by at least one of reflecting, refracting or diffracting the light.

24. The method of claim 13, further comprising:

causing the biological agent or the chemical agent to fluoresce at a wavelength that is different from a wavelength of the light, in response to the biological agent or chemical agent being illuminated by the light.