How to Measure a Laser Spatial Profile Spot Size
One of the very useful properties of laser light is its directionality. A typical laser beam spot has very small spread, that is it spreads minimally as the light beam moves forward. Even though this spread is very small, depending on the application, it may be desirable to measure or calculate the spot size as well as its spread with distance. For example, in cancer therapy it is very important to keep the laser beam focused on the tumor to minimize the damage to healthy tissues. Measuring the spot size of a laser at different distances is an effective method of determining the beam spread profile.
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Things You'll Need
- Laser light source
- Laser mount
- Masking tape
- Tape measure
- Small cardboard piece on a stand -- preferably white with smooth surface
- Ruler with mm rulings
- Calculator
Instructions
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1
Mount the laser source such that the laser beam is as parallel to the surface as possible.
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2
Place markings on the floor in line with the laser source at different distances from the front of the laser source, for example at distances of 3 meters, 6 meters and 9 meters. You can stick a piece of masking tape on the floor with a cross on it as the marker.
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3
Turn the laser on.
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4
Place the cardboard stand facing the laser beam at the first mark and adjust its length such that the laser beam spot can be clearly seen without any distortion.
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5
Use the ruler to measure the diameter of the spot three times by using the ruler at different angles. Note these numbers on a piece of paper.
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6
Take the average of the measurements by summing the three numbers and dividing the result by 3. You can use a calculator for this purpose.
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7
Move the cardboard stand farther away from the laser source to the next two markers one by one and take diameter measurements as well as calculate the respective averages. You now have the spatial profile of the laser's spot size.
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Tips & Warnings
Never look directly into the laser source as the laser light may damage your eyes.
References
- Photo Credit Laser Entfernungsmesser image by Otmar Smit from Fotolia.com
