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This article describes a simple electrical circuit for monitoring the alignment of an expanded laser beam. One use of the device is in the manufacture of holographic optical elements.
English (United States)
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Laser Beam Intensity Tester
This article describes a simple electrical circuit for monitoring the alignment
of an expanded laser beam. One use of the device is in the manufacture of
holographic optical elements.
In making or copying holographic optical elements, a segment of holographic
recording material is exposed using an expanded laser beam. If the intensity of
the beam is not uniform over the area of the exposed segment, the resulting
holographic optical element will have non-uniform characteristics.
The uniformity of illumination provided by an expanded laser beam is
primarily a function of the physical alignment of the laser. A laser beam can be
aligned by visual observation of the expanded beam. There are drawbacks to
this approach. It is subjective and may be inaccurate since it depends entirely on
a given operator's perception of beam intensity at certain points. It may also be
time consuming and inefficient. The laser beam may have to be realigned
repeatedly during the manufacturing cycle since thermal expansion or contraction
may cause the beam to "wander".
The drawing shows a simple system for providing objective measurements of
the intensity of an expanded laser beam over a limited area. A plurality of solar
cells 10 are arranged in a cruciform configuration on a circular fixture 12. The
solar cells 10 are connected to the negative input of an operational amplifier 14
through individual switches in a switch bank 16. The positive input to the