Gentec-EO Accessories for Beam Diagnostics - Manual (Page 15)

Accessories for Beam Diagnostics Revision 1.2 15
4. WAVELENGTH CONVERTERS
4.1. BEAMAGE-3.0-IR
The Beamage-3.0-IR allows you to image IR laser sources that have wavelengths contained between 1495 nm
and 1595 nm. A phosphor coating is applied on the sensor to take advantage of a multi-photon absorption
process that converts wavelengths contained between 1495 nm and 1595 nm to shorter wavelengths contained
between 950 nm and 1075 nm. Refer to Figure 11 for the excitation spectrum.
Table 8: Beamage-3.0-IR Specifications
IR Spectral Range 1495 nm – 1595 nm
Pixel Count 2.2 MPixel
H x V 2048 x 1088
Minimum Measurable Beam Size 70 µm
Sensor Size 11.3 mm x 6.0 mm
Peak IR Sensitivity 1510 nm and 1540 nm
Converted Wavelengths 950 nm – 1075 nm
Maximum Input Power (Damage Threshold)
with default ND4 filter
1 W
Pixel Multiplication Factor 1
Maximum Resolution 12 lp/mm over active area
40 lp/mm at sensor focal plane
Distortion -1.0% barrel distortion (inverted image)
Linearity Non-Linear, IR converted output
∝ IR
input intensity ^1.41
Spectral Transmission 360 nm – 2000 nm
Part Number 202360
Important Step to Follow When Using the Beamage-3.0-IR
Apply the Despeckle Filter
The phosphor coating on the sensor produces speckles that may alter the intensity profile of the beam and thus
affect the accuracy of the measurements.
Therefore, it is important to use the Despeckle Filter when viewing a beam with a Beamage-3.0-IR beam profiler
because it will remove speckles and noise related to transmission of light through the phosphor coating.
The Despeckle filter is an aggressive spatial filter that performs a 9x9 pixels simple averaging around each pixel,
with all of the pixels having the same relative weight (1/81).
Please note that using the Despeckle Filter can slightly reduce the resolution but will provide a significant
improvement in the beam profile measurement.
Warning
Please note that the minimum measurable beam diameter at a 50% clip level is
approximately 70 µm. Any smaller beam will be significantly broadened by the point spread
function of the phosphor.