Method for monitoring an entrance to a hazardous area
First Claim
Patent Images
1. A method for monitoring an entrance of a hazardous area with the aid of a light grid arrangement comprising light barriers, said method comprising the following steps:
- a) recording actual received brightness values H of an individual light beam associated with a respective light barrier;
b) deriving a signal pattern from the received brightness values H by comparing the actual received brightness values with an upper threshold value SO and a lower threshold value SU, wherein the received brightness values H are assigned to the following signal states;
“
free”
H>
SO “
blanked”
H<
SU “
partially blanked”
SU<
H<
SO and wherein the individual signal states of the light beams form the derived signal pattern;
c) comparing the derived actual signal pattern to a predetermined signal pattern of an object that is considered permissible to enter the hazardous area; and
d) determining the object as a permissible object if one of the derived signal pattern coincides with the predetermined signal pattern, and an actual signal state “
partially blanked”
or “
blanked”
is obtained in place of a predetermined signal state “
free”
or “
partially blanked”
for a light beam in the region of a first edge of the object, an actual signal state “
blanked”
or “
free”
is obtained for a light beam in a region of a second edge of the object in place of the predetermined signal state “
blanked”
or “
partially blanked” and
the remaining signal states of the derived signal pattern coincide with the signal states of the predetermined signal pattern.
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Abstract
A method for monitoring an entrance to a hazardous area comprising sensing a signal pattern generated by light barriers when an object passes the entrance and comparing the sensed signed pattern with at least one predetermined signal pattern. The object is admissible if the signal patterns are identical and under certain other conditions.
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Citations
11 Claims
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1. A method for monitoring an entrance of a hazardous area with the aid of a light grid arrangement comprising light barriers, said method comprising the following steps:
-
a) recording actual received brightness values H of an individual light beam associated with a respective light barrier;
b) deriving a signal pattern from the received brightness values H by comparing the actual received brightness values with an upper threshold value SO and a lower threshold value SU, wherein the received brightness values H are assigned to the following signal states;
“
free”
H>
SO“
blanked”
H<
SU“
partially blanked”
SU<
H<
SOand wherein the individual signal states of the light beams form the derived signal pattern;
c) comparing the derived actual signal pattern to a predetermined signal pattern of an object that is considered permissible to enter the hazardous area; and
d) determining the object as a permissible object if one of the derived signal pattern coincides with the predetermined signal pattern, and an actual signal state “
partially blanked”
or “
blanked”
is obtained in place of a predetermined signal state “
free”
or “
partially blanked”
for a light beam in the region of a first edge of the object, an actual signal state “
blanked”
or “
free”
is obtained for a light beam in a region of a second edge of the object in place of the predetermined signal state “
blanked”
or “
partially blanked” and
the remaining signal states of the derived signal pattern coincide with the signal states of the predetermined signal pattern.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification