Device for detecting surface wetness

• US 6,369,378 B1
• Filed: 12/01/1999
• Issued: 04/09/2002
• Est. Priority Date: 06/06/1997
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Meier, Hans, Hermann, Wolfgang, Lamm, Hubert, Blitzke, Henry, Haderer, Guenter
• Primary Examiner(s): Le, Que T.
• Assistant Examiner(s): Luu, Thanh X
• Application Number:
  US09/445,045
• Time in Patent Office: 860 Days
• Field of Search: 250/227.25, 250/573-577, 250/559.4, 250/214.AL, 250/214.B, 356/436, 356/440, 356/448, 318/483, 340/602
• US Class Current: 250/227.25
• 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

Abstract

The device for the detection of a wetting of a pane of glass, has an optical rain sensor which detects extraneous light and evaluates it for purposes of day-night detection. The amount of light striking the receiver (14) is integrated in an integration stage (16) and supplied to a comparator stage (20). The total light quantity formed by the light of a transmitter (12) and extraneous light and the extraneous light quantity detected when the transmitter (12) is switched off are measured in separate time intervals (Tg, Tf, Tf′). The time interval (Tf, Tf′) utilized for measurement of the extraneous light quantity is to be extended after a predeterminable number of measurement cycles (M) or after a predeterminable time period and/or the threshold (S2) is to be lowered for day-night detection.

Claims

1. A device for detecting wetting of a pane of glass, or a windshield, said device comprising a rain sensor including

a measurement circuit comprising a light-radiating transmitter (12) for generating radiated light, a light receiver (14) arranged to receive a portion of the radiated light according to the wetting of the pane of glass or windshield as well as extraneous light and to generate a sensor signal depending on a light amount of the portion of the radiated light and the extraneous light reaching the receiver, an integration stage (16) for integrating the sensor signal from the light receiver and for generating an integrated sensor signal and a comparator (20) for generating a trigger signal (21) when the integrated sensor signal exceeds a predetermined threshold;

and

an evaluating circuit (22) including means for turning on said light-radiating transmitter (12) during a plurality of first predetermined time intervals (Tg) and for turning off said light-radiating transmitter (12) during another plurality of second predetermined time intervals (Tf;

Tf′

) for evaluating the extraneous light and for day-night detection;

means for determining an integrated light quantity reaching said light receiver (14) during each of said time intervals when a respective one of said trigger signals is received;

means for adjusting said predetermined threshold of said comparator to a first threshold value (S1) during each of said first predetermined time intervals during which the light-radiating transmitter is turned on and to a respective second threshold value (S2) during each of said second predetermined time intervals during which the light-radiating transmitter is turned off for evaluating the extraneous light and for day-night detection and means for adjusting each of said second predetermined time intervals to a first time interval value (Tf) for evaluating the extraneous light and to a second time interval value (Tf′

) for day-night detection after a predetermined number of extraneous light measurements, said second time interval value (Tf′

) being longer than said first time interval value (Tf).

2. The device as defined in claim 1, wherein said evaluating circuit (22) includes means for adjusting respective durations of each of said first predetermined time intervals and said second predetermined time intervals.

3. The device as defined in claim 2, wherein said predetermined time intervals are between one second and one minute.

4. The device as defined in claim 2, wherein said second predetermined time interval is between 10 milliseconds and ten seconds.

5. The device as defined in claim 1, wherein said predetermined threshold of said comparator (20) is continuously adjustable or is adjustable in discrete amounts.

6. The device as defined in claim 1, wherein said second threshold value is less than said first threshold value.

7. The device as defined in claim 6, wherein said second threshold value is a factor of 8 less than first threshold value.

8. The device as defined in claim 1, wherein said evaluating circuit (22) includes means for controlling at least one of a windshield wiper for said windshield, headlights, headlight wiping-cleaning systems, dashboard illumination, sliding roof and side windows of a motor vehicle in response to said integrated light quantity determined by said evaluating circuit.

9. The device as defined in claim 8, further comprising means for amplifying the sensor signal.

10. The device as defined in claim 8, wherein said evaluating circuit (22) has means for controlling a sensitivity or a switching threshold of the rain sensor depending on the extraneous light quantity.