The Ophir® BeamSquared system measures the propagation characteristics of CW and pulsed laser completely automated. It’s compact design and its flexibility in terms of wavelength – it is suited for measuring UV to NIR to Telecom wavelength – makes it a powerful measurement tool in many laser applications. As with every highly precise laser measurement device its biggest enemy is Optics contamination due to dust and debris. Also, to ensure optimal measurement conditions an accurate offset correction is essential. Here are three tipps how to ensure precise measurement with your Ophir BeamSquared system over years.
1. Keep an eye on any changes
Before starting the measurements with the Ophir BeamSquared device, it is recommended to perform an “Ultracal™” offset calibration. After the offset calibration, the noise level on the screen shows blueish and greyish signals in balance.
Fig. 1: Standard noise level after Ultracal offset calibration
Just lately, the following picture has been taken with an Ophir BeamSquared:
Fig. 2: Contamination on an optical component can lead to the greyish blur as seen here.
The greyish blur to be seen in the upper two quadrants in figure 2 indicates an Ultracal offset noise. It occurred at auto-stepping and ISO-Auto mode when preparing a training session held with the BeamSquared. This is the first indicator that dust - probably on the variable filters – causes stray light within the BeamSquared measurement system. At that stage it will most likely not influence the measurement itself as the negative pixels shown in light grey are located outside the aperture and will not be used by the UltraCal algorithm anyways. Only with very small beam diameters and a beam position in the upper quadrants the offset noise can lead to differing measurements. Nevertheless, this is one early indicator that there is a contamination in the optical path. Any “noise” to be seen on the picture of the beam, should be considered relevant.
A more prominent hint leading to the conclusion that there is dust on a lens, or a mirror can be seen in figure 3. Small particles lead to these Newton’s rings or bull’s eye interference patterns, they are not to be seen permanently on the screen but only in certain points.
Fig. 3: A so-called bull’s eye pattern can occur if there is an optical component in the laser path with a contamination
2. Be careful when cleaning optical components
If you suspect a contamination of your optics and want to clean them from dust: Do not use duster spray to clean any optics otherwise condensed gas will contaminate the optics. Externally attached optics should be cleaned as instructed by the respective manufacturer. Generally, the best way is to use optical paper and isopropyl alcohol.
3. Regular re-certification of the BeamSquared
The re-certification procedure of the BeamSquared device includes the cleaning of all optics and mirrors inside the product. Based on a regular use of the BeamSquared, Ophir suggests a re-certification once a year. A re-certification of the BeamSquared system not only reassures you on the performance of your camera, it prevents any issues such as outlined above. The re-certification process will correct bad pixels when possible, clean the imager, and certify that the device is still performing to factory specifications. Any necessary changes, repairs or replacements will be detected upfront and action will be taken after coordination with the customer
Fig. 4: BeamSquared Offset after cleaning the variable filter