Non-imaging laser particle counter

Details Non-imaging laser particle counter Non-imaging laser particle counter

1989-11-28

1992-02-04

Rosenberger, Richard A.

Optics: measuring and testing

By particle light scattering

With photocell detection

356340, 356343, 250574, G01N 2100, G01N 1506

Patent

active

050855000

ABSTRACT:
A non-imaging particle counter 10 utilizing one or more detectors 25 which directly collect light scattered by particles in a fluid traversing a sensing volume 63. The detectors 25, are non-imaging, non-focusing, optic-less light collection devices, such as large area photodiodes. The detectors 25 are arranged and configured proximate the sensing volume 63, but such that the beam of light 60 is not operatively incident thereon. The beam of light 60 is provided by a laser 50 and is shaped by a focusing/collimating lens 54. The beam of light 60 passes through several apertures 51-53 to reduce stray/background light in the system. The detectors 25 are oriented at an angle with respect to the plane formed by the longitudinal axis of the beam and the flow of fluid, wherein stray light 61 strikes the detectors 25 at an angle greater than the acceptance angle of the detectors 25, while scattered light strikes the detectors 25 at an angle less than the detectors' 25 acceptance angle. A light stop 31 having a Brewster angle for the wavelength of the beam of light 60 is utilized as a beam stop. Further, a coincidence detection circuit 100 provides for reducing spurious counts caused by ionizing emissions and/or other noise.

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