Rotary Scales

Precision Glass Rotary scales (Codewheels)

Maximize performance of any optical encoder with precision glass scales by VC America. Linear and Rotaryscales are manufactured using soda-lime glass with chrome reflective and absorptive layers optimized for 630-640nm (Red LED), with dimensional precision and low defect density.

Standard scales provide opportunity for fast evaluation and support production and we manufacture to customer specifications for unique patterns and dimensional requirements.

Track periods of 20µm, 40µm, 100µm are common. We'll manufacture scales to 2µm period (1µm reflective +1µm clear or anti-reflective) when needed.

Code	Precision Rotary	Mounting Adhesives
CG	Reflective chrome on clear glass	Epoxy, UV
AR	Reflective chrome topside with Anti-reflective layer bottom side	Epoxy
AC	Reflective chrome and Anti-reflective layer top side (in track area) and clear center zone	Epoxy, UV

Rotary scales OD and ID are sawed and edges may be straight cut or beveled with chamfer or rounded edges.

Symbol	Material	Specification	Tolerance	Units
OD Maximum	Soda-Lime Glass	Up to 700	±0.1	mm
OD		Outside Diameter	±0.1	mm
ID		Inside Diameter	±0.1	mm
T		Thickness	±0.05	mm
TTV		Total Thickness Variation	10	µm
LTV		Local Thickness Variation	5	µm
CTE		Temperature coefficient of expansion	8.5	10^-6mm/mm°C

Parameter	Reference	Minimum	Typical	Maximum	Units
Pitch/Period Accuracy	Local			±1	µm
Pitch/Period Accuracy	Total			±2	µm
Metal pattern alignment to Axis				±20	µm
Chrome reflective layer	Standard	50	54	60	%
	Augmented	60	65	70	%
	Enhanced	88	93	98	%
Chrome absorptive(anti-reflective)@ 630nm	AR		<2	5	%