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Table 2-3
Specification
Description
≥90%
Spectral Transmittance
Thickness
0.8-2.0mm
PV maximum: 0.2λ
Wavefront Distortion
RMS maximum: 0.04λ
Clear Aperture
1.0mm to edges
Surface Quality
60-20 scratch/dig
Pay extra attention to the wavefront distortion when using plastic materials. Plastic materials are not recommended for
tilted windows; colored windows are not recommended if the engine is used to scan barcodes on moving objects.
Coatings and Scratch Resistance
Scratch on the window can greatly reduce the performance of the EM3296 V4. It is suggested to use abrasion resistant
window material or coating.
The following introduces two commonly-used types of coatings:
• Anti-reflection coatings: Anti-reflection (AR) coatings can be applied to window surfaces to reduce reflected light from
the window back into the engine. But they are expensive and have poor abrasion/scratch resistance.
• Polysiloxane coatings: Polysiloxane coatings can be applied to plastic surfaces to increase the surfaces' abrasion and
scratch resistance.
Both tempered glass and plastic windows can be AR coated. However, it is easier and more cost-effective to put an AR
coating on the glass than on the plastic.
The AR coating specifications below should be met when using an AR coated window.
Single side AR coating: 92% minimum transmittance within spectrum range from 420 nm to 730 nm.
Double side AR coating: 97% minimum transmittance within spectrum range from 420 nm to 730 nm.
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