System for detecting reflected laser beams

• US 4,154,529 A
• Filed: 03/21/1977
• Issued: 05/15/1979
• Est. Priority Date: 03/21/1977
• Status: Expired due to Term

• Current Assignee: Andrew Corporation (CommScope Holding Company, Inc.)
• Original Assignee: Andrew Corporation (CommScope Holding Company, Inc.)
• Inventors: Dyott, Richard B.
• Primary Examiner(s): Buczinski, S. C.
• Application Number:
  US05/779,361
• Time in Patent Office: 785 Days
• Field of Search: 356/28, 356/5, 356/103, 356/207, 356/208, 350/96 C, 250/199, 250/227
• US Class Current: 356/28
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: G01N 15/0205 by optical means

Abstract

A system for detecting a reflected light beam includes a source of coherent light such as a laser beam, an optical fiber spaced away from the source for receiving an incident beam of coherent light from the source at one end of the fiber, means for reflecting a portion of the incident beam back through at least a portion of the fiber to radiate a reflected beam which includes narrow angle signals having a beam width corresponding to that of the incident beam and wide angle signals having a beam width substantially wider than that of the incident beam, receiving means between the source and the optical fiber for receiving the reflected beam and having an optical aperture therein for transmitting the incident beam and the narrow angle signals in the reflected beam, and a projector lens between the receiving means and the optical fiber for directing the incident beam into the optical fiber and for directing the narrow angle signals in the reflected beam into the optical aperture of the receiving means. This system may be used as a velocimeter for determining the velocity of moving particles adjacent the opposite end of the optical fiber from the end that receives the incident light beam. The receiving means typically comprises a mirror for reflecting the wide angle portion of the reflected beam into a photoelectric transducer, or the receiving means may itself be a photoelectric transducer.

Claims

1. In a velocimeter, the improvement comprising

(a) a source of coherent light,

(b) an optical fiber spaced away from said source for receiving an incident beam of coherent light from said source at a first end of the fiber and directing said light onto moving objects located adjacent a second end of the fiber, whereby said moving objects reflect a portion of said light back into said fiber with a beamwidth substantially wider than that of the incident beam so that the light reflected from said objects emerges from said first end of said fiber with a larger angle than that of the incident light beam entering the fiber, said second end of said fiber also reflecting a portion of the incident beam to produce reflected light emerging from said first end of said fiber with a larger angle than that of the incident beam entering said fiber,

(c) a mirror between said source and said optical fiber for directing the wide angle reflected light emerging from the first end of said fiber transversely away from said incident beam, said mirror having an optical aperture therein for transmitting therethrough the incident beam,

(d) a lens for directing the incident beam into the optical fiber,

(e) and a photoelectric transducer for receiving the beam reflected by said mirror and converting said beam to analogous electrical signals.