Rice Lake Motorola DS457 Laser Scanner - Manual (Page 35)

Installation 2 - 11
Embedded Applications Requiring a Window
Use the following guidelines for applications that require a window in front of the DS457.
Window Material
Many window materials that look perfectly clear can contain stresses and distortions that can reduce imager
performance. For this reason, Motorola highly recommends optical glass or cell-cast acrylic. Following is a
description of acrylic and CR-39, another popular window material.
Table 2-1
outlines the suggested
window properties.
Acrylic (PMMA)
When fabricated by cell-casting, acrylic has very good optical quality and low initial cost. However, protect the
surface from the environment as acrylic is susceptible to attack by chemicals, mechanical stresses, and UV light.
Acrylic has reasonably good impact resistance and can be ultrasonically welded.
CR-39 (ADC)
CR-39 is a thermal-setting plastic produced by the cell-casting process, and is commonly used in plastic eye
glasses lenses. CR-39 has excellent chemical and environmental resistance, including good surface hardness.
Typically it does not require hard-coating, but can be hard coated for severe environments. CR-39 has
reasonably good impact resistance and cannot be ultrasonically welded.
Chemically Tempered Float Glass
Glass is a hard material which provides excellent scratch and abrasion resistance. However, unannealed glass
is brittle. Increasing flexibility strength with minimal optical distortion requires chemical tempering. Glass cannot
be ultrasonically welded and is difficult to cut into odd shapes.
NOTE
Motorola does not recommend placing an exit window in front of the DS457; however, the following
information is provided for applications that require such a window.
NOTE
Consider the following window placement and material recommendations if mounting the DS457 within a
product with its own window.
CAUTION
Consult an opto-mechanical engineer to recommend an appropriate window material and to
determine if coatings are appropriate for the specific application.
!
NOTE
Do not use polycarbonate material.