The rod microlenses have a circular cross-section, highly polished round walls, and their optical axis is perpendicular to their mechanical axis. Unlike glass rods with polished flat ends that act as optical windows along their mechanical axis, rod microlenses are used sideways like other cylindrical lenses.
The rod lens Effective Focal Length (EFL) and Working Distance (WD) at a selected wavelength depend on the glass refractive index (n) and its diameter (D) as:
Rod Diameter Tolerance
+/- 0.005 mm for D 0.1 to 0.9 mm
+/- 0.010 mm for D 1.0 to 5 mm
+/- 0.015 mm for D 5.1 to 10 mm
Height Tolerance + 0.000 / -0.040 mm Length Tolerance +/- 0.050 mm AR Coating R < 0.5%, AOI 0-30°