초록 ▼

Apparatus for detecting the presence of an object within an area under surveillance employs an electro-optical emitter for directing light into the area and an electro-optical receiver for sensing light reflected from the object which originates from the emitter. The emitter emits light energy of a

Apparatus for detecting the presence of an object within an area under surveillance employs an electro-optical emitter for directing light into the area and an electro-optical receiver for sensing light reflected from the object which originates from the emitter. The emitter emits light energy of a preselected wavelength and is modulated at a preselected frequency to provide the emanating light energy with a characteristic signature. Light reflected by an object within the area under surveillance is filtered and converted to an electrical signal which varies in accordance with the magnitude of the filtered light having the preselected wavelength and modulation frequency. A selected portion of the electrical signal is amplified by a band-pass amplifier and is synchronously sampled in accordance with the modulation frequency to determine the magnitude of the filtered light which originated from the emitter. The sampled signal is compared with a threshold value to determine whether an object is present within the area under surveillance. The emitter and receiver are covered by a transparent shield to protect them against foreign matter. An electro-optic detector monitors the accumulation of foreign particulates on the shield. The apparatus may be desirably used in vehicles to detect the presence of adjacent objects, particularly within the vehicle\s “blind spots”and thereby avoid collisions.

대표청구항 ▼

Apparatus for detecting the presence of an object in an area under surveillance comprising: emitter means for emitting light into said area; controller means coupled to said emitter means for generating an activating signal to control the intensity of said light such that said intensity has a keyed

Apparatus for detecting the presence of an object in an area under surveillance comprising: emitter means for emitting light into said area; controller means coupled to said emitter means for generating an activating signal to control the intensity of said light such that said intensity has a keyed modulation; detector means for receiving light from said area and generating an electrical signal proportional thereto, said electrical signal having said keyed modulation; synchronous means coupled to said detector means and to said controller means for deriving a first portion of said electrical signal having said keyed modulation; threshold means coupled to said synchronous means for generating an indicating signal when the magnitude of said first portion exceeds a threshold value; delay means coupled to said controller means for generating a quadrature signal phase shifted by substantially 90°from said activating signal; quadrature means coupled to said detector means and to said delay means for deriving a second portion of said electrical signal having a modulation corresponding to said quadrature signal; and circuit means coupled to said quadrature means and to said synchronous means for comparing said first portion and said second portion.