Optical device for projecting a radiation beam onto a data carrier Patent #: 4139263
ApplicationNo. 06/830964 filed on 02/19/1986
US Classes:250/566, Including coded record359/499Using compensation techniques
ExaminersPrimary: LaRoche, Eugene R.
Assistant: Pascal, Robert
Attorney, Agent or Firm
International ClassesG01N 21/21 (20060101)
G02B 21/00 (20060101)
G02B 27/10 (20060101)
AbstractA confocal optical imaging system includes a laser for producing a linearly polarized beam which is transmitted through the optical elements of the system, focused on a small spot on the target, and reflected back through the optical elements to a photodetector where the reflectance from the spot is determined. The optical elements include a pinhole plate for restricting the size of the transmitted and reflected beams which plate, along with other of the optical elements, can produce unwanted reflections adding optical noise to the reflected beam from the target. A retardation plate between the pinhole plate and the target alters the polarization of the transmitted beam relative to the reflected beam so that a polarizer will discriminate between the true reflected beam signal and the unwanted reflections to thereby improve the signal-to-noise ratio at the photodetector.
Field of SearchIncluding coded record