Water drop detector on transparent substrate and initiating method and output stabilizing method therefor

• US 6,239,444 B1
• Filed: 05/05/2000
• Issued: 05/29/2001
• Est. Priority Date: 07/22/1997
• Status: Expired due to Fees

• Current Assignee: Niles Company Limited (Valeo SE)
• Original Assignee: Nippon Sheet Glass Company Limited (Nippon Telegraph and Telephone Corporation)
• Inventors: Koyama, Tadashi, Tsunetomo, Keiji, Tanaka, Shuhei
• Primary Examiner(s): Lee, John R.
• Assistant Examiner(s): PYO, KEVIN K
• Application Number:
  US09/564,799
• Time in Patent Office: 389 Days
• Field of Search: 250/573, 250/574, 250/575, 250/214 R, 250/227.25, 250/205, 318/483, 318/480, 318/443, 318/444, 318/DIG. 2, 340/601, 340/602
• US Class Current: 250/573
• CPC Class Codes: B60S 1/0818 including control systems responsive to external conditions, e.g. by detection of moisture, dirt or the like
• CPC Class Codes: B60S 1/0833 Optical rain sensor
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

A water drop detection device for detecting an amount of water drops present upon a surface of a transparent substrate in which a light source with a driver circuit guides light into the substrate so as to cause the light to under go internal reflection within the substrate. The light source has a light emitting element and a receiving light sensing element for detecting the light output from the emitting element. The light output from the light emitting element is modulated by a predetermined frequency. A signal corresponding to the modulated component is separated from the output signal of the receiving light sensing element. The output light emission of the light emitting element is maintained at a desired value by feeding the separated signal back to the driver circuit of the light emitting element.

Claims

1. A water drop detection device for a transparent substrate, for detecting an amount of water drops adhering to or present upon a surface of said transparent substrate, comprising:

a light emitting means for guiding light into said transparent substrate so as to cause internal reflection to occur upon interior surfaces of said transparent substrate, and including a driver circuit therein; and

a light receiving means for receiving the light reflected within said transparent substrate, wherein said light emitting means comprises;

a light emitting element; and

a receiving light sensing element, located in close proximity to the light emitting element, detects light output from said light emitting element, and further comprising;

means for modulating the light output from said light emitting element with a predetermined frequency, wherein only the modulated component is detected by said light receiving means;

means for separating a signal corresponding to the modulated component from the output signal of said receiving light sensing element; and

means for controlling an output of light emission of said light emitting element at a desired value by feeding the separated signal back to the driver circuit of said light emitting element.