Light emitting diode array having uniform illuminance distribution

• US 4,814,667 A
• Filed: 04/06/1987
• Issued: 03/21/1989
• Est. Priority Date: 04/17/1986
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Tanaka, Toshiaki
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Powell, Mark R.
• Application Number:
  US07/034,932
• Time in Patent Office: 715 Days
• Field of Search: 313/110, 313/500, 313/512, 340/752, 340/782, 355/67-71, 355/3 R, 355/1, 362/11, 362/227, 362/252, 362/800, 362/223, 362/235, 362/236, 362/241
• US Class Current: 313/500
• CPC Class Codes: B41J 2/45 using light-emitting diode [LED] or laser arrays
• 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
• CPC Class Codes: H04N 1/02815 Means for illuminating the original, not specific to a particular type of pick-up head
• CPC Class Codes: H04N 1/02865 using an array of light sources or a combination of such arrays, e.g. an LED bar
• CPC Class Codes: H04N 1/02885 Means for compensating spatially uneven illumination, e.g. an aperture arrangement
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

This invention provides a light emitter for generating light having a predetermined effective level of illuminance distribution over a defined region of a given size. The light emitter comprises a light emitting diode having a specified overall length for generating the predetermined effective level of illuminance distribution, including a central array of LED chips equally spaced from each other at a first interval, an end array of LED chips equally spaced from each other at a second interval smaller than the first interval. The light emitter also comprises a gap where there are no chips, the gap being larger than the first interval between the central array and the end array for alternatively maintaining the predetermined effective level of illuminance distribution and increasing the size of the defined region, and maintaining the size of the defined region and decreasing the overall length of the diode. The light emitter comprises a circuit board for supporting the light emitting diode.

Claims

1. A light emitter for generating light having a predetermined effective level of illuminance distribution over a defined region of a given size, comprising:

light emitting diode means having a specified overall length for generating the predetermined effective level of illuminance distribution, including a central array of LED chips equally spaced from each other at a first interval, an end array of LED chips equally spaced from each other at a second interval smaller than the first interval, and means defining a gap larger than the first interval between the central array and the end array for alternatively maintaining the predetermined effective level of illuminance distribution and increasing the size of the defined region, and maintaining the size of the defined region and decreasing the overall length of the diode means; and

circuit board means for supporting the light emitting diode means.

2. The light emitter of claim 1 wherein the the second interval is at least twice the first interval.

3. The light emitter of claim 1 wherein the end array includes six LED chips, and the gap has a length between three and more times the second interval.

4. The light emitter of claim 1 wherein the end array includes six LED chips, and the gap has a length between three and seven times the second interval.

5. A method of reducing the length of a light emitter having an array of a plurality of LED chips, comprising the steps of:

(a) specifying an overall length for the array for generating a predetermined effective level of illuminance distribution;

(b) spacing a central array of LED chips equidistant from each other at a first interval;

(c) spacing an end array of LED chips equidistant from each other at a second interval smaller than the first interval; and

(d) defining a gap larger than the first interval between the central array and the end array, said gap being defined for maintaining the predetermined effective level of illuminance distribution over a defined region of a given size and reducing the length of the light emitter.