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No. 99MBC032A
3.2.15 Recording the amount of light
• The gap measurement may be unstable if not enough laser beam passes through the gaps.
In the case shown in diagram (a) below, an adequate amount of light can be obtained as
the laser passes through gap (g) above the workpiece, even if the gap (t) is small. How-
ever, in diagram (b) where gap (t) is small, measurement will be affected. In this case,
therefore, it is necessary to have the system record the full amount of light when there is
no obstruction (workpiece or fixture) in the optical path.
Workpiece
Workpiece
t
g: Gap for the
reference beam
t
Gap
Gap
(a) Light amount can be detected normally = Auto-detecting
(b) Recording the amount of light is required
Laser beam
passes through
this gap.
Light amount
cannot be detected
(insufficient duration)
Photo-electric signal
Light amount
can be detected
Peak of the
photo-electric
signal
• Normally the amount of incident light is continuously checked so that the counting
operation can follow the change in the amount of incident light. The minimum size of gap
“g” or “t” is 2 mm. Have the system record the light amount following 4.4, “How to read-
in the amount of light”. It is also necessary to carry out this operation twice or three times
each year since the light amount of the system may vary.
