Improvements in or relating to transparency sensors

An improved transparency sensor (10) uses Brewster's Law to detect the presence of sheets of transparency material (20). The sensor (10) includes a light emitting diode (LED) (12) and two photodiodes (14, 16) arranged to receive light reflected from the material (20). The LED (12) supplies inci...

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Bibliographische Detailangaben
1. Verfasser:	RICHARD ANDREW MULLENS
Format:	Patent
Sprache:	eng
Schlagworte:	ANALOGOUS ARRANGEMENTS USING OTHER WAVES DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION ORRERADIATION OF RADIO WAVES MEASURING PHYSICS RADIO DIRECTION-FINDING RADIO NAVIGATION TESTING
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Beschreibung
Zusammenfassung:	An improved transparency sensor (10) uses Brewster's Law to detect the presence of sheets of transparency material (20). The sensor (10) includes a light emitting diode (LED) (12) and two photodiodes (14, 16) arranged to receive light reflected from the material (20). The LED (12) supplies incident light at an angle ( theta ) which is related to the refractive index of the transparency material (20) to be detected. A polarizing filter (18) is associated with one of the photodetectors (16) and is oriented to cut out substantially reflected polarized light entering that photodiode (16). Output signals from the photodetectors (14, 16) are processed in a comparator (40) which provides an output signal (42) indicating the presence or not of a transparency material (20).