Newland EM20-85, Integration Manual

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9
Window Material and Color
Window material must be clear. Use only cell-cast plastics or optical glass. PMMA and chemically tempered glass are
recommended. Window material selected for the engine should meet or exceed the specifications specified in Table 2-2 .
When using a clear plastic window, it is recommended to apply anti-reflection (AR) coating on it.
•
PMMA (Cell-cast acrylic): When fabricated by cell-casting, has very good optical quality and low initial cost, but surface
must be protected from the environment due to its susceptibility to attack by chemcials, mechanical stresses, and UV
light. Reasonably good impact resistance.
•
Chemically tempered glass: Glass is a hard material which provides excellent scratch and abrasion resistance. But
unannealed glass is brittle. Increased flexibility strength with minimal optical distortion requires chemical tempering.
Glass is hard to be cut into odd shapes and can not be ultrasonically welded.
Table 2-2
Specification Description
Thickness 0.8-2.0mm
Wavefront Distortion
PV maximum: 0.2λ
RMS maximum: 0.04λ
Clear Aperture 1.0mm to edges
Surface Quality 60-20 scratch/dig
Pay extra attention to the light wavelength when using plastic materials. Colored windows are not recommended if the
engine is used to scan barcodes on moving objects.