Before allowing laser energy to enter the instrument, it is important to limit the beam intensity. Excessive laser energy may cause damage to the camera or the internal components of the BeamSquared optical train.
Typically, a CCD camera sensor can be damaged at energy levels in excess of 1 mJ/cm² or at power levels greater than .15 mW/cm². Adjust these input limits downward based on the likely focused spot size resulting from your M² lens focal length. Beam splitters and/or filters may be used to attenuate the beam, but care must be used to prevent the introduction of distortions.
During an M² measurement operation, the peak energy density that reaches the camera will change, potentially over several orders of magnitude. This is a result of the camera effectively moving from a larger unfocused spot near the lens, into and through the focus at the waist, and then out again to an unfocused spot (see the Adjusting Brightness section in the manual). The Linear attenuators in the optical train will automatically adjust to accommodate these changes in beam intensity, so long as the operator, has prudently selected the initial beam intensity. Thus, it is the operator's responsibility to attenuate the laser sufficiently to operate within the safe dynamic range of the BeamSquared system.