Metrologic Instruments IS4823 - Manual (Page 16)

12
Beam Clearance
• Keep the scan engine’s beam sweep free from obstructions. For detailed information on the exit beam
angle and location, please refer to Exit Beam Specifications on page 9.
• A dark matte-finish on the internal walls of the housing can be utilized to avoid internal beam
reflections.
Output Window Properties
Note: Contact a customer service representative to coordinate the best window material required to maintain
laser safety requirements for your application.
An improperly placed window has the serious potential to reduce the scan engine’s performance.
Careful consideration must be made when designing the output window’s distance and angle
placement relative to the scan engine’s exit beam and chassis.
Follow these guidelines when designing the output window.
• Acceptable window materials include; Acrylic (cast or molded), float glass, CR-39, and Polycarbonate.
Note: Molded polycarbonate is high in strength; however, it might exhibit a phenomenon called
birefringence. Birefringence refers to multiple indices of refraction within one material.
This condition will induce polarization effects that can be detrimental to scan performance of the
engine. Check with a representative before utilizing a transparent polycarbonate material for
the output window.
• The exit window material should have a spectral transmission of at least 85% from 640 nm to 690 nm
and should block shorter wavelengths.
• Red cell-cast acrylic is recommended.
• The exit window should exhibit a wavefront distortion (transmission) of no more than 0.2 wavelengths
peak-to-valley maximum over any 0.08" diameter within the clear aperture.
• The clear aperture of the output window should extend beyond the 54° beam sweep (see Exit Beam
Specifications on page 9).
• It should have a 60-40 surface quality and be optically flat, clear, and free of scratches, pits, or seeds.
If possible, recess the window into the housing for protection or apply a scratch resistance coating (see
Output Window Coatings on page 13).
• Apply an anti-reflective coating to the window surfaces to reduce the possibility of reflective light
interfering with the engine’s performance due to the window angle (see Output Window Coatings
on page 13).