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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.

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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.

Attenuator Selection

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).

Specifications VARM C-VARM UV C-VARM BCUBE UV-BCUBE BARREL-SET
(Barrels, 3 C- Mount Flanges)
Wavelength
Min. (nm)
 380 380 190 380 190 –
Max. (nm)
 2200 2200 1100 2200 2200 –
Attenuation
From
 4x105:1 107:1 105:1 50:1 50:1 –
To
 1:1 3000:1 300:1 10:1 10:1 –
Aperture (mm) 19 15 15 19 19 –
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 –
Part Number 33-3328-000 33-3336-000 33-6859-000 1098403 1098466 1098426


* The maximum power and energy density listed are the levels at which thermal lensing occurs.



Drawing Packages
Click the links below to download a complete drawing package for these products.

Related Materials

Drawings

Drawings

C-VARM and UV C-VARM Drawings

C-VARM and UV C-VARM Drawings (pdf)

VARM Drawing

VARM Drawing (pdf)

BCUBE and UV-BCUBE Drawings

BCUBE and UV-BCUBE Drawings (pdf)