Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-05-07
2001-05-01
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
30
Reexamination Certificate
active
06225621
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the laser sensor art.
Heretofore, laser sensors have included a laser diode or other laser source which was focused to a preselected focal length by a convergent focusing lens. Laser light reflected from a reflector was received by another convergent lens with a relatively long focal length and focused on a photodiode detector. The output of the photodiode was monitored and an electronic signal was generated indicative of the reception of the reflected laser beam or the absence of the reflected laser beam. In order to distinguish between the reflected laser beam and stray light of like color, some laser sensors included a feedback system, such as a continuous wave type feedback system, between the laser source and the detector.
Although successful, such prior laser sensors have drawbacks. First, the prior laser sensors are typically operative for a relatively short distance range, on the order of up to 30 meters. Even within that distance range, different lenses on the laser are required for different distances. Typically, the selected laser sensor must be matched to the application. Although less critical on the receiving side, the receiving lenses again must be compatible with the distance for which the sensor is calibrated. The longer focal length lenses at the receiving side tend to use only part of the photodetector as the length becomes longer, reducing sensitivity. If the length is too long, the lens may focus off the photodetector.
The present invention provides a new and improved laser sensor which overcomes the above-referenced problems and others.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a laser is provided. A laser diode is powered by a laser drive circuit to emit laser light. A collimating lens mounted adjacent the laser diode collimates the emitted laser light. A photoreceiver receives reflected laser light and produces an output signal indicative of the receipt
on-receipt of reflected laser light. An optical lens is disposed adjacent the photoreceiver for focusing the reflected laser light onto the photoreceiver. The optical lens has an f-number less than 1.0.
In accordance with another aspect of the present invention, a method of laser sensing is provided. Laser light is emitted and collimated into a collimated beam of parallel rays. The collimated beam is transmitted across a region of interest and is reflected back across the region of interest. The reflected laser beam is focused with a lens having an f-number less than 1.0. The focused, reflected laser light is detected. A presence/absence of reflected laser light is determined.
In accordance with a more limited aspect of the present invention, the optical lens is a ball lens.
One advantage of the present invention is that it senses over ranges of up to 50-70 meters.
Another advantage of the present invention is that no lens replacements are required to change between long and short distance ranges. The same sensor can be used for either long or short distances without lens changes.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.
REFERENCES:
patent: 3614449 (1971-10-01), Ward, III
patent: 3941483 (1976-03-01), Ferrin
patent: 4290043 (1981-09-01), Kaplan
patent: 4807166 (1989-02-01), Zalenski
patent: 0601847 (1994-06-01), None
patent: 0709798 (1996-05-01), None
Mersch Steven H.
Rogers John D.
Allen Stephone B.
Automatic Timing & Controls, Inc.
Faye Sharpe, Fagan, Minnich & McKee LLP
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