How to prolong the life of your beam profilers

Markus Schmiedt, Senior Manager Manufacturing/Operations

1. The sensors (CCD nor CMOS) in our beam profilers cannot be cleaned by customers. It is imperative that they remain free from impurities in the form of dust, aerosols, or other physical adulterants such as the oils from fingerprints or mishandling. When camera devices are not in use, they should be stored in a clean, dry area, preferably in an enclosed bag to prevent contamination.
2. CCD and CMOS cameras are sensitive and must not be dropped, otherwise the imager may crack or the wire bonds may become damaged.

1. Correct alignment and timing
   When aligning the BeamWatch, BeamWatch Integrated or BeamWatch AM measurement devices, make sure to use the alignment laser only. Otherwise, the alignment tool and the device itself can be damaged. Parts of the measurement chamber inside the product may be burned, making reliable measurement impossible. For the BeamWatch Integrated, additional care needs to be taken with the shutter. The timing between "laser-on" and "open/close shutter" needs to be correctly set by the SPS developer. If the shutter is showing a burn hole, the measurement chamber will be flooded with particles that can damage mirrors and optics.
2. Keep the chamber clean:
   In order to avoid comets or streaks in the images of the laser beam when measuring with a BeamWatch device, care has to be taken to supply only clean, dry, filtered air or nitrogen to the BeamWatch. It is important to keep the dust covers over the openings of the BeamWatch in place until the purge air is flowing in order to prevent dust contamination prior to operation. Also, the pressure of the purge gas is important: while too-low pressure allows dust to enter the measurement chamber, a too-high pressure can lead to turbulence. In either case, imprecise measurements are the result.
3. Ensure smooth processes by using pure water
   Sometimes when industrial measurement devices are used at production sites, the quality of the water is not sufficient. To avoid any issues, only deionized water should be used for water-cooled laser power sensors. In any case, the water must be clear, clean and sediment free. The size of any particles in the water must not exceed 150 microns, and the total number of particles must be less than 1000 ppm. To achieve this kind of water quality, a suitable filter should be installed upstream of the sensor, directly before its connection to the water. An overview of the recommended water quality is provided in the following table:

1. Keep an eye on the camera
   CCD or now CMOS cameras as used with the BeamSquared can be damaged by power in excess of 0.15 mW/cm2 or energy in excess of 1 μJ/cm2.. BeamSquared employs a focusing optic. While it may be that the laser input power or energy density measures well below this damage threshold, it can easily exceed these levels when focused onto the camera sensor. Do not align the laser through the BeamSquared until the beam has been properly attenuated. Applying an unattenuated beam to the BeamSquared may damage the optics. The camera imager is windowless and can be easily damaged if it comes in contact with any foreign objects. Clean the camera imager only by gently blowing clean dry air or nitrogen across it – and only if absolutely necessary.

In contrast to sensor calibrations, NIST and PTB do not offer a Gold or Silver Standard for a beam profiling camera system. Therefore, we refer to "recertification" processes when talking about beam profilers. To help you maintain camera performance, MKS recommends that customers return their Ophir camera-based beam profilers on a regular basis (every 12 months is recommended under normal use) for a verification and recertification process. A combination of recalibration and recertification is performed for some of our beam caustic measurement devices.

For the Ophir BeamSquared device we do both a recertification of the camera as well as a recalibration of the mechanical parts within the beam path. Recalibration and recertification of the Ophir BeamWatch Integrated devices include a thorough cleaning of the units in the Ophir R&R lab.