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Air turbulence Effects On Lasers

Air turbulence is the main enemy of accurate alignments for both lasers and optics. It is not air turbulence, per se, that affects lasers and optics but different temperature gradients between the laser and target or the scale and optical instrument. Although dust and humidity my degrade the accuracy somewhat, it is extremely minor compared to temperature gradients. Wind also does not usally affect the laser accuracy unless that wind has a different temperature than the area around the laser, like when someone opens the door in the winter.

Temperature gradients affects the accuracy mainly by causing "noise" in the readings. In other words, the reading on the display will fluctuate by as much as +/- .010" (0.2 mm) in very poor conditions. The same phenomenon happens with optics where the operator sees the marks on the scale "jump" around in his scope. To give an example of this property, the "bubbling" affect seen when looking down a paved road on a hot summer day is caused by exactly the same optical property.

The fluctuations are caused by the laser beam passing through 2 or more different temperature gradients, which has the effect of slightly bending or refracting the laser beam before it hits the target. The good news is the beam tends to fluctuate in a circle and can be minimized by using 2 simply techniques.

The first technique is to average the readings in the readout, where an average of 10-20 readings will usually dampen out the fluctuations. This is easily done by simply choosing the number of data points to average on the R-1309 Readout. The only downside of this technique is it will tend to slow down the response time to adjustments of the surface being aligned. In other words, when adjusting a measurement point to bring it into alignment, the readout will take 2-3 times longer to update.

The second technique is to use fans to homogenize or mix the air around the laser beam. When using fans to minimize the air turbulence, it is important to point them along the same path as the laser beam. Pointing the fan perpendicular to the line between laser and target will result in the fluctuations increasing rather than decreasing.

Other tips to minimize air turbulence include: keeping building doors closed that are near the laser, pointing air conditioning vents away from the area, blocking or redirecting the air from exhaust vents from other machines, etc.

Following these simple steps can mean the difference between a successful alignment and long, long day "chasing your tail."

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