Light emitting diode array and optical image forming apparatus with light emitting diode array

• US 5,838,024 A
• Filed: 11/07/1996
• Issued: 11/17/1998
• Est. Priority Date: 11/10/1995
• Status: Expired due to Term

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Masuda, Kouji, Suzuki, Seizo
• Primary Examiner(s): Saadat, Mahshid D.
• Assistant Examiner(s): Wilson, Allan R.
• Application Number:
  US08/744,311
• Time in Patent Office: 740 Days
• Field of Search: 257/88, 257/91, 257/95, 257/98, 257/99, 257/257, 257/294, 257/432, 257/436, 359/738, 438/29
• US Class Current: 257/98
• CPC Class Codes: B41J 2/451 Special optical means therefor, e.g. lenses, mirrors, focusing means
• CPC Class Codes: G02B 3/005 arranged along a single direction only, e.g. lenticular sheets G02B3/0043 takes precedence
• CPC Class Codes: G02B 3/0062 Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between
• CPC Class Codes: G02B 3/0068 arranged in a single integral body or plate, e.g. laminates or hybrid structures with other optical elements G02B5/1885, G02B17/002, G02B30/27 take precedence
• CPC Class Codes: G02B 3/0081 having one or more elements with analytic function to create variable power variable magnification in general G02B15/00
• CPC Class Codes: G02B 3/04 with continuous faces that are rotationally symmetrical but deviate from a true sphere , e.g. so called "aspheric" lenses
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

An image forming system utilizing a light emitting diode (LED array) having LEDs arranged along a curved line. The LEDs are either edge emitting type LEDs or surface emitting type LEDs. The LEDs of the LED array emit light towards a center or optical axis of the lens. A plurality of lenses are connected together to form a lens array. Alternatively, two lens arrays can be utilized. If two lens arrays are utilized, each of the lenses in the lens array includes an aspherical surface. The curved LED array prevents the flaring of light and produces an even pattern of light emission on a light receiving surface such as a photoconductive drum.

Claims

1. An image forming system, comprising:

an LED, Light Emitting Diode, array having LEDs disposed thereon along a curved line, each of the LEDs forming the curved line, and a direction of emission of the LEDs and the curved line being generally planar;

a lens which focuses light emitted from the LEDs; and

a light receiving surface which receives the light from the LEDs which was focused by the lens.

2. An image forming system according to claim 1, wherein:

the LED array includes edge emitting type LEDs.

3. An image forming system according to claim 1, wherein:

the LED array includes surface emitting type LEDs.

4. An image forming system according to claim 1, wherein:

the LEDs of the LED array emit light towards an optical axis of the lens.

5. An image forming system according to claim 1, wherein:

the lens includes two aspherical surfaces.

6. An image forming system according to claim 1, further comprising:

a second lens which receives light from the first lens and focuses light from the first lens onto the light receiving surface.

7. An image forming system according to claim 6, wherein:

each of the lenses includes an aspherical surface.

8. An image forming system according to claim 1, wherein the light receiving surface is a photoconductive drum.

9. An image forming system according to claim 1, wherein:

the curved line is an aspherical line.

10. An image forming system according to claim 9, wherein:

the lens has at least one curved surface which is an aspherical surface.

11. An image forming system according to claim 10, wherein:

the curved line which is an aspherical line is arranged to reduce an astigmatism of the system and the curved surface which is an aspherical surface is arranged to reduce aberrations.

12. An image forming system according to claim 1, wherein:

the curved line has LEDs at ends thereof aimed at angles towards a center of the lens.

13. An image forming system according to claim 1, wherein:

an LED at a center of the LED array is aimed towards a center of the lens.

14. An image forming system according to claim 13, wherein:

the curved line has LEDs at ends thereof aimed at angles towards a center of the lens.

15. An image forming system according to claim 1, wherein:

the array is parallel to an axis of rotation of the light receiving surface.

16. An image forming system according to claim 1, wherein:

the curved line has two inflection points.

17. An image forming system according to claim 16, further comprising:

a first axis parallel to a rotating axis of the light receiving body; and

a second axis perpendicular to the first axis,

wherein the curved line has at least a total of five local minima and maxima relative to the second axis.

18. An image forming system according to claim 1, wherein:

the curved line comprises three points at which a first derivative of the line is zero.

19. An image forming system, comprising:

an LED, Light Emitting Diode, array means having LEDs disposed thereon along a curved line, each of the LEDs forming the curved line, the LED array means for emitting light, and a direction of emission of the LEDs and the curved line being generally planar;

a lens means for focusing light emitted from the LEDs; and

a photosensitive means for receiving the light from the LEDs which was focused by the lens.

20. An image forming system according to claim 19, wherein:

the curved line is an aspherical line.

21. An image forming system according to claim 20, wherein:

the lens means has at least one curved surface which is an aspherical surface.

22. An image forming system according to claim 21, wherein:

the curved line which is an aspherical line is arranged to reduce an astigmatism of the system and the curved surface which is an aspherical surface is arranged to reduce aberrations.

23. An image forming system according to claim 19, wherein:

the array means is parallel to an axis of rotation of the photosensitive means.

24. An image forming system according to claim 19, wherein:

the curved line has two inflection points.

25. An image forming system according to claim 24, further comprising:

a first axis parallel to a rotating axis of the photosensitive means; and

a second axis perpendicular to the first axis,

wherein the curved line has at least a total of five local minima and maxima relative to the second axis.

26. An image forming system according to claim 19, wherein:

the curved line comprises three points at which a first derivative of the line is zero.