LED array and partitive driving method therefor using overlapping activation periods

• US 5,063,462 A
• Filed: 12/05/1989
• Issued: 11/05/1991
• Est. Priority Date: 03/21/1984
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kuroda, Yasuo, Nakagawa, Katsumi, Kawai, Tatsundo
• Primary Examiner(s): COLES, EDWARD L
• Application Number:
  US07/445,929
• Time in Patent Office: 700 Days
• Field of Search: 358/475, 340/713, 340/762, 250/573
• US Class Current: 358/475
• 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 1/03 with photodetectors arranged in a substantially linear array
• CPC Class Codes: H04N 1/40056 Circuits for driving or energising particular reading heads or original illumination means H04N1/401, H04N1/407 take precedence

Abstract

An LED array has a plurality of LED blocks each of which can independently be illuminated or extinguished. The LED array includes an illumination control unit for illuminating, after the lapse of a time period T1 after a block is illuminated, a succeeding block; an extinguishment control unit for extinguishing, after the lapse of a time period T2 after a block is illuminated, another block which has been illuminated since before the former block was illuminated; and a time control unit for determining the time period T2. The time control unit is adapted to automatically control the time period T2 in accordance with the outputs from a line sensor which reads out an original image illuminated by the LED array.

Claims

1. A partitive driving method for an LED array having a plurality of LED blocks each of which can independently be turned on, said method comprising the steps of:

turning on, after the lapse of a time period T1 after a block b is turned on, a succeeding block c;

extinguishing, after the lapse of a time period T2 after the block b is turned on, another block a which has been in a turned on state since the time before said block b was illuminated; and

variably setting the time period T2 in accordance with the output of a line sensor which receives light from the LED array.

2. A light source array for an image read-out apparatus including a plurality of blocks having a plurality of light sources, each of said blocks being independently turned on or extinguished, said array comprising:

illumination control means for turning on, after the lapse of a time period T1 after a first block is turned on, a succeeding block;

extinguishment control means for extinguishing, after the lapse of a time period T2 after the succeeding block is turned on, the first block which has been turned on since the time before said succeeding block was turned on; and

time control means for variably setting the time period T2 in accordance with the output signal of a signal source.

3. A light source array according to claim 2, wherein said time control means sets the time period T2 in accordance with the environmental temperature.

4. A light source array according to claim 3, further comprising means for measuring the environmental temperature, comprising a thermistor or a thermocouple.

5. A light source array according to claim 2, further comprising a line sensor for detecting the light output by said blocks, and wherein said time control means sets the time period T2 in accordance with outputs from said line sensor.

6. A light source array according to claim 2, wherein said signal source comprises a line sensor.

7. A light source array according to claim 2, wherein said signal source comprises a device for measuring temperature.

8. A light source array according to claim 2, wherein said light source comprises LEDs.

9. An image reading apparatus comprising:

a light source array including a plurality of blocks having a plurality of light sources, each of said blocks being independently turned on or extinguished, said array further including illumination control means for turning on, after the lapse of a time period T1 after a first block is turned on, a succeeding block,

extinguishment control means for extinguishing, after the lapse of a time period T2 after the succeeding block is turned on, the first block which has been turned on since the time before said succeeding block was turned on, and

time control means for variably setting the time period T2 in accordance with the output signal of a signal source; and

a line sensor for reading reflected light from an original illuminated by said light source array.

10. An image reading apparatus according to claim 9, further comprising a light transmitter for imaging the reflected light on said line sensor.

11. An image reading apparatus according to claim 9, wherein said apparatus comprises a facsimile machine.

12. An image reading apparatus according to claim 9, wherein said apparatus comprises a contact type image sensor.

13. A partitive driving method for a light source array of an image read-out apparatus having a plurality of light source blocks each of which being independently turned on, said method comprising the steps of:

turning on, after the lapse of a time period T1 after a block b is turned on, a succeeding block;

extinguishing, after the lapse of a time period T2 after the block b is turned on, another block a which has been turned on before block b was turned on; and

variably setting the time period T2 in accordance with the output of a signal source.