Author:
Chuck Reagan, Southeast Sales Manager, Ophir-Spiricon, LLC
Not all customers want to use an image converter or attenuation as it is possible to introduce aberrations or defects in the beam. Those defects may slightly change the beam measurements and displayed profile, which could introduce some uncertainty in the displayed results.
Ophir-Spiricon offers a number of tools and we work very hard to try to avoid introducing error into the measurements. We choose very good optical materials and we reject materials that do not pass our inspections. Several of those tools are shown below, but the first let’s discuss direct UV beam imaging, including attenuation.
Direct Imaging
When imaging direct UV light, the first priority is to protect the sensor from powerful, short-term UV light, which can immediately damage the sensor (just as Visible and IR lasers do). If users are unable to reduce the energy or power of the UV laser with the operator power controls, they may still have to use UV grade, Fused Silica beam splitters and UV grade attenuators, or other acceptable attenuation, which will reduce the energy or power of damaging beams.
After attenuation, the operator should ensure that enough usable UV signal is available to the camera for profiling needs. Many UV attenuators are reflective so users must plan to avoid or contain those reflective beams. Avoid using any beam near the saturation level of the camera. Ophir-Spiricon recommends using image converters for wavelengths below 350nm. Most camera manufacturers place a cover glass over the sensor that blocks UV light below 400nm, which helps protect cameras.
Ophir-Spiricon removes that glass from most of their cameras to allow customers the option to use that area of the response curve if they need it. Having no cover glass on the camera CCD sensor opens the possibility for mechanical damage to the sensor. The normal sources of mechanical damage include a blast of shop or canned air, fingers, or a cotton swab, which will guarantee damage to the sensor.
Damage Limits
Many people ask, “How long will it take and what power/energy settings will damage my sensor by slow ablation if I use it daily or weekly with direct, even attenuated, UV light?” Due to the lack of published directives or limits, the answer to that question is unknown. Manufacturers do not provide CCD ablation charts, maximum allowed energy/power charts, duration-of-exposure-to-damage-charts, or any other named limits charts or tables. Even if using maximum allowable attenuation, the UV light will still eventually ablate the sensor if used for long periods of time.
Indirect Imaging
As stated above, Ophir-Spiricon recommends using image converters for wavelengths below 350nm.
