Optical ranging by phase shift measurement with return signal level compensation
First Claim
1. An optical ranging system of the type employingmeans for radiating optical energy bearing continuous amplitude modulation,means for gathering a portion of the optical energy returned from an object, andmeans for measuring distance to the object by detecting the phase difference between the modulation of the radiated optical energy and the modulation of the returned optical energy, including means for compensating for variations in the level of the returned optical energy,said system being characterize in that the compensating means includes an optical portion based upon the partial optical blocking of the gathering means by the radiating means and an electronic portion based upon an automatic gain control arrangement in which phase shift occuring in such electronic portion varies negligibly with signal level, and the gathering means includes means for focusing the non-blocked portion of the returned optical energy arriving at the gathering means.
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Accused Products
Abstract
There is disclosed an optical ranging system adapted for use with widely varying return signal levels. Automatic signal level control is achieved in two parts, a passive optical part and an active electronic AGC part. The optical part is based on the coaxial arrangement of transmitting and receiving elements in which the shielded transmitting element is mounted in front of the receiving element, which includes Fresnel lens which comprises a plastic casting. The electronic AGC portion of the system includes means for providing a voltage drive (with low internal impedance) for the final AGC transistor when it would tend to be slow, so little phase shift in the control results from changes in the signal levels. Thereby, the determination of distance (the ranging) by phase shift measurement is kept reliable as signal level changes. This optical ranging system is especially adapted for mounting on autonomously guided vehicles (robot carts), which are important for material handling and inventory control in manufacturing systems in factory environments.
24 Citations
10 Claims
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1. An optical ranging system of the type employing
means for radiating optical energy bearing continuous amplitude modulation, means for gathering a portion of the optical energy returned from an object, and means for measuring distance to the object by detecting the phase difference between the modulation of the radiated optical energy and the modulation of the returned optical energy, including means for compensating for variations in the level of the returned optical energy, said system being characterize in that the compensating means includes an optical portion based upon the partial optical blocking of the gathering means by the radiating means and an electronic portion based upon an automatic gain control arrangement in which phase shift occuring in such electronic portion varies negligibly with signal level, and the gathering means includes means for focusing the non-blocked portion of the returned optical energy arriving at the gathering means.
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4. An optical ranging system of the type employing
means for radiating optical energy bearing continuous modulation means for gathering a portion of the scattered optical energy returned form an object and means for measuring distance to the object by detecting the phase difference between the modulation of the radiated optical energy and the modulation of the returned optical energy, including means for compensating for variations in the level of the returned optical energy said system being characterized in that the raditing means is positioned in front of the gathering means and adapted to minimize propagation of optical energy from the radiating means to the gathering means other than via the object, and in addition the gathering means includes means for focusing the nonblocked portions of the returned optical energy arriving at the gathering means in such a way as to reduce the effect of the inverse square law dependence of the received scattered light-intensity upon distance of the scattering object.
Specification