Measuring Laser Position & Pointing Stability

One of the laser’s most useful properties is that while a laser beam propagates it defines a straight line. Many optical systems designed to exploit this property include: range finders, optical scanners, laser printers, laser marking machines and many more. For these systems it is extremely important that the laser beam is directed toward its designed location. Beam profilers have the capacity to indicate where the beam is located on the detector of the beam profiler, and different types of profilers can indicate position with varying degrees of accuracy. Therefore, beam profilers are often used while operating laser systems to ensure they are functioning properly. Beam profilers are also used to streamline the manufacturing process of a laser system, efficiently ensuring the laser spot is on the right location.

Related to beam spot location, in many systems it may be important to measure laser angular pointing stability as well. Pointing stability is a measure of how much the beam angle drifts from the ideal target over time. Stability can be affected by a number of factors, including: temperature variation, physical motion, cavity instability, air currents and more.  Ophir-Photon offers many beam profilers that can measure and monitor pointing stability.

Generally, laser position or beam pointing stability measurements are made simply by placing the beam profiler at a given distance from the laser source and aligning the beam until it points to the ideal target. However, in order to achieve very high accuracy of the beam pointing position it may be important to minimize the distance through which the laser beam propagates before reaching the detector. Air currents and heat waves change the refractive index of the air through which the laser propagates, thus causing a false position or pointing stability reading on the profiler. This presents a problem especially when measuring a laser spot position over a long distance, such as for laser range finders or laser sighting products. The longer the distance is the more the change of the refractive index of the air affects beam position.

Photon’s NanoScan provides an optimal solution for achieving very high accuracy measurements of beam position. The unsurpassed pointing accuracy of the NanoScan allows the entire measurement to be reduced to the bench top. Using scan averaging, the NanoScan is capable of measuring angular deviations of 1 micro radian on a 10 cm test bench. Obviously a 10cm test range is far easier to manage and control than one spanning 100 or even 1000 meters in length. Manufacturers of range finding and laser sighting products have found that the NanoScan reduces their test time dramatically, leading to high throughput and rapid time to market for their products.

NanoScan software could provide a picture of the amount of excursion from the ideal target and in which axes the movement takes place. In addition, the software provides temporal graphs of the beam excursion. The graph enables the user to understand what events may have caused the misplacement of the beam.

Ophir-Photon offers many solutions for position and stability measurements. For more details about how laser position measurements are done, and what device is appropriate for different laser systems feel free to read the full article

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