Electro-optical windshield moisture sensing

US4798956A · kind A · utility

Inventor

• Peter A. Hochstein · Troy, US

Key dates

• Filing date: Jul 15, 1987
• Grant date: Jan 17, 1989
• Expiry date: Jul 15, 2007

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S15/15
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

The invention is a moisture sensor which includes an emitter (18) to emit pulses of radiant energy toward the inside surface (14) of a window (12) at an incident angle (.theta.). The radiant energy is refracted into the window (12) at the air-inside window surface (14) and reflected off the air-outside window surface (16) back through the window (12). The radiant energy is then detected by a detector (20) at a reflection angle (.theta.') equal to the incident angle (.theta.). A support (22) spaces the emitter (18) and detector (20) a distance D between the intersection (I) of the axis (A) of the emitter (18) with the inside window surface (14) and the intersection (E) of the axis (B) of the detector (20) with the inside window surface (14) which is determined by the formula: EQU D=2T cos .theta.(n.sup.2 - cos.sup.2 .theta.).sup.-1/2 The detector (20) includes a collimator (36) to prevent non-parallel radiant energy from entering the detector (20) and an optical filter (40) to filter out radiant energy wavelengths below a predetermined wavelength in order to detect the emitted radiant energy.