Patent ID: 7400260

Claim:
An optical system for detecting ice and water on the surface of an aircraft, said system comprising: an elongated transparent optical element having proximal and distal end portions; a light source for generating a beam of light disposed in said distal end portion; a light detector and means for generating a variable signal dependent on the amount of light received by said detector disposed in said distal end portion; said transparent optical element including a reflective surface and an optical channel for transmittal light from said light source to said reflective surface and light from said reflective surface to said light detector; said reflective surface defining a critical angle disposed on a surface of an aircraft so that light is reflected toward said light detector when said reflective surface is in contact with air and refracted toward the external environment when said reflective surface is in contact with ice or water; temperature sensing means disposed in said optical element adjacent to said reflective surface for sensing the temperature at the surface of the aircraft; means for pulsating the light source and means including a demodulator and filter for limiting the response from said light detector to light reflected from said light source; comparator means for comparing reflected light from said light detector to a light threshold and second comparator means for comparing the temperature from said temperature sensing means to a temperature threshold; and means for combining the output of said first and second comparator means to thereby indicate the presence of ice or water on the surface of the aircraft.