Light barrier utilizing two radiation branches each having differently polarized filters
First Claim
1. A light barrier system, comprising:
- a source of radiation;
means for producing, from said radiation source, two radiation branches spatially offset from each other in a spatial region to define a light barrier, and including a first polarizer for producing different independent radiation polarization in the two branches;
means for receiving the two radiation branches, comprising a sensor for each radiation branch, and including a second polarizer for filtering the radiation, so that only radiation having the same polarization as the radiation in its associated branch is received by the associated sensor, each of said sensors producing an output signal indicative of the intensity of polarized radiation received; and
a gating circuit connected to receive the sensor outputs, and for producing an alarm signal in response to different radiation intensities being received by the two sensors.
1 Assignment
0 Petitions
Accused Products
Abstract
In a light barrier, especially for outside application and long distances monitored, insensitivity to interfering light and scattering through fumes or fog and an increased range and sensitivity to objects passing through the light barrier are achieved by subdividing radiation from a source into two radiation branches which are offset relative to each other and differently polarized, e.g., by means of a polarization filter divided into two parts, with different linear or oppositely circular polarization of the filter part surfaces. By means of an analogously subdivided polarization filter, the radiation of each of the two radiation branches is focused on a different individual sensor element. The two sensor elements are connected in a differential circuit which triggers an alarm signal in response to signals arriving from both radiation branches in short succession but does not trigger an alarm signal if both sensor elements are equally irradiated.
-
Citations
10 Claims
-
1. A light barrier system, comprising:
-
a source of radiation; means for producing, from said radiation source, two radiation branches spatially offset from each other in a spatial region to define a light barrier, and including a first polarizer for producing different independent radiation polarization in the two branches; means for receiving the two radiation branches, comprising a sensor for each radiation branch, and including a second polarizer for filtering the radiation, so that only radiation having the same polarization as the radiation in its associated branch is received by the associated sensor, each of said sensors producing an output signal indicative of the intensity of polarized radiation received; and a gating circuit connected to receive the sensor outputs, and for producing an alarm signal in response to different radiation intensities being received by the two sensors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
Specification