Optical level measurement system
AssigneeCourser, Incorporated
InventorCharles King
Life of this patent
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Abstract
To provide rapid level measurements with improved reliability, the present invention provides an apparatus and method for optically determining the level of a material through a technique for measuring the ratio of digital signals acumulated during an index interval and for modifying those signals to compensate for variations that can be caused by the shape of the beam detector signal. More particularly, the present invention provides a level detector system which includes a laser beam source which directs light to be reflected from a surface to be measured, the reflected light being directed to a stationary parabolic mirror.
Claims8
An optical measuring system for measuring the surface level of a light-reflective material, comprising:
- a detector unit including a fixed, parabolic mirror, and a rotatably mounted plane mirror having its axis of rotation at the focal point of said parabolic mirror, whereby a beam of light directed to the plane mirror from said parabolic mirror will be reflected in a circular path about said axis of rotation;
- a source of light directing a beam of light along a predetermined path which includes the reflective surface of said light reflective material, said parabolic mirror, and said plane mirror;
- index means responsive to the rotation of said plane mirror to produce an index signal for each revolution of said plane mirror;
- a light-responsive detector lying in said circular path and responsive to said beam of light on said predetermined path for generating a beam signal during said index signal, said parabolic and plane mirrors being so related that variations in the surface level of said light-reflective material produces a corresponding variation in the time of occurrence of said beam signal with respect to said index signal;
- clock means having a fixed clock rate;
- logic circuit means driven by said clock means and responsive to said index signal to produce a train of index count pulses having a count corresponding to the duration of said index signal and responsive to said beam signal to produce a train of beam count pulses having a count corresponding to the time of occurrence of said beam pulse signal with respect to said index signal;
- means determining the ratio of said beam count pulses to said index count pulses;
- and
- means responsive to said ratio for providing an indication of the level of the surface of said light-reflective material.
Dependencies are inferred from the claim text.