Attenuation Optics for Cameras
BCUBE, UV-BCUBE, VARM, C-VARM, UV C-VARM and all other Coherent cameras have female C-Mount threading, making them easy to connect with the male C-Mount connection flange provided with each attenuator. Also, all attenuators have 1/4-20 tapped holes for independent post or plate mounting.
The C-Mount flanges (threaded rings) also have a female RMS microscope thread. This allows a microscope objective to be coupled to the attenuators and extension barrels in order to create a flexible close-up imaging system for analysis of small/focused beams, fiber optics, laser diodes or LEDs.
Avoiding Multi-Filter Beam Distortion
The wavefront distortion through a number of optical filters can be calculated by taking the square root of the sum of the squares of the wavefront distortion of the individual components. In general, a camera cannot sense less than ~λ/4 total distortion in the beam, so if a series of filters is used, they must be made to very exacting laser-grade specifications. Attenuating optics from Coherent are manufactured to better than a λ/10 surface specification, so at least six optics in series can be used. Calculate the Low-Distortion Face Plate (LDFP) and each BCUBE as one optic, and the VARM or C-VARM as three optics each.
Attenuation is selected on the basis of power density in W/cm2 or energy density in J/cm2. The attenuation from the camera’s Low-Distortion Face Plate (LDFP) will allow an average power density of up to 1.2 mW/cm2. There are then only two more steps to attenuation selection:
1) Choose either the VARM or the C-VARM for up to 1W/cm2.
2) In addition or alternatively, use a BCUBE beamsplitter module to pick off between 2% and 10% of the beam (depending on polarization and wavelength).
|(Barrels, 3 C- Mount Flanges)|
|Max. Power Density (W/cm2)||1*||1*||1*||2.0x109||2.0x109||–|
|Max. Energy Density (J/cm2)||0.1*||0.1*||0.008||50||50||–|
|Beam Offset (mm)||–||–||–||4.0||4.0||–|
* The maximum power and energy density listed are the levels at which thermal lensing occurs.
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