8/5/2023 0 Comments Laser point measure![]() The above-described apparatus performs a fairly specialized test. ![]() Angular changes, on the other hand, will be detected by the laser beam profiler.įigure 1: Pointing measurement system to discern angular and linear pointing accuracy With this system any linear motion of the laser will be detected by the near field profiler, but will not appear in the far field due to the f-theta properties of the lens. The other detector in the far field is set up with a lens of a known focal length (e.g., 1 meter) with the detector positioned at the geometric focus. The first is set up as a near field profiler imaging the front aperture of the laser via a beam splitter. In order to measure the linear and angular pointing, the measurement system will comprise two detectors. It is good to know whether instability is coming from linear motion of the laser or from angular perturbations. This can be very useful if the measurement’s purpose is to determine the stability of pointing in an optical system. It is possible to design a fairly simple measurement system to separate these two components of pointing. The angular component is the tip or tilt of the laser beam altering the path from the parallel. This motion is normally 1:1, that is, if the laser is raised 1mm, the spot moves 1mm unless there is a magnification lens in the optical path¹. This is the motion that one sees when the laser is raised or lowered, translated right or left, or is subjected to some type of vibration. The linear component comes from the horizontal and vertical motion of the laser, perpendicular to the axis of propagation. ![]() There are actually two components to laser pointing and laser pointing stability, linear and angular, which combine to affect the beam’s position. Stability can be affected by a number of factors, internal and external to the laser itself, including physical motion, heat buildup, cavity instability, air currents, and many more. Pointing stability is a measure of how much the beam position drifts from the ideal target over time. Pointing accuracy is simply whether the laser points where it is supposed to. Laser pointing accuracy and pointing stability are defined as an angular value, usually in milli- or microradians (mr or μr). But there is more to this measurement and more that can be learned about the laser’s performance. For laser scanning applications the measurement may be made in different locations across the scan plane to ensure proper linearity of the scan. Most of the time the measurement is made by placing the beam profiler at some distance from the laser source and aligning the beam until it points to the ideal target. Beam profilers have the capacity to tell where the beam is located on the detector, and different types of profilers can do this with varying degrees of accuracy and precision. This is often a simple measurement of where in space a laser spot is focused or aimed, which is relevant to a number of laser applications from laser range finding to optical scanning, laser marking to building laser printers. ![]() Therefore, beam profilers are often used to verify the performance of lasers and optical systems to avoid problems caused by bad alignment or to streamline the manufacturing processes of these devices. One of the laser’s most useful properties is that it can propagate over great distances defining a straight line, and many optical systems are designed to exploit this property. By Allen Cary, Director of Marketing, Ophir-Spiricon
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