EP 0200186 A3 19870121 - LIGHT BARRIER
Title (en)
LIGHT BARRIER
Publication
Application
Priority
CH 182585 A 19850430
Abstract (en)
[origin: US4734575A] 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.
IPC 1-7
IPC 8 full level
G08B 13/18 (2006.01); G08B 13/183 (2006.01)
CPC (source: EP US)
G08B 13/183 (2013.01 - EP US)
Citation (search report)
- [X] GB 1214981 A 19701209 - HORROCKS JOHN
- [Y] DE 1946993 A1 19710325 - SICK ERWIN FA
- [Y] US 4342987 A 19820803 - ROSSIN JOHN A
- [A] US 3440427 A 19690422 - KAMMER FRANZ
- [A] US 2457502 A 19481228 - O'D SHEPHERD JUDSON
Designated contracting state (EPC)
AT BE CH DE FR GB IT LI NL SE
DOCDB simple family (publication)
EP 0200186 A2 19861105; EP 0200186 A3 19870121; EP 0200186 B1 19910529; AT E64023 T1 19910615; CH 667340 A5 19880930; DE 3679443 D1 19910704; US 4734575 A 19880329
DOCDB simple family (application)
EP 86105818 A 19860426; AT 86105818 T 19860426; CH 182585 A 19850430; DE 3679443 T 19860426; US 85683486 A 19860428