Optical encoder system
Optical encoding systems include a generalized cylindrical code scale having one or more regions with different light reflective properties. In an example process, a code scale can be created by coating an elongated generalized cylinder with one or more different layers of materials having different light reflective properties. Portions of these layers can be removed selectively in order to expose a particular overlying material and create a particular pattern of features having different optical characteristics (e.g., absorbing, specularly reflecting, diffusely reflecting).
1. A code scale for an optical encoder system, comprising:
a cylinder having a first circumferential surface, the first circumferential surface having a first light reflective characteristic;
a first layer at least partially coating the first circumferential surface, the first layer having a second circumferential surface;
a second layer at least partially coating the second circumferential surface, the second layer having a third circumferential surface;
one or more first gaps extending through the second layer to the second circumferential surface; and
one or more second gaps extending through the second layer and the first layer to the first circumferential surface,
wherein the second circumferential surface has a second light reflective characteristic different from a first light reflective characteristic, and
wherein the third circumferential surface has a third light reflective characteristic different from the first light reflective characteristic and the second light reflective characteristic.
2. The code scale of claim 1 , wherein the first and second reflective characteristics each correspond to different specularly reflective characteristics.
3. The code scale of claim 1 , wherein one of the first and second reflective characteristics corresponds to a predominantly anisotropic reflective characteristic.
4. The code scale of claim 1 , wherein one of the first and second reflective characteristics corresponds to a predominantly diffusely reflective characteristic.
5. The code scale of claim 1 , wherein each of at least two of the first, second, and third reflective characteristics corresponds to a different respective specularly reflective characteristic.
6. The code scale of claim 1 , wherein the at least two of the first, second, and third reflective characteristics corresponds to a predominantly anisotropic reflective characteristic.
7. The code scale of claim of claim 1 , wherein at least one of the first, second, and third reflective characteristics corresponds to a predominantly diffusely reflective characteristic.
8. The code scale of claim 1 , where at least one of the first, second, and third reflective characteristics corresponds to a predominantly light absorbing characteristic.
9. The code scale of claim 1 , wherein at least one of the first and second reflective characteristic corresponds to a predominantly light absorbing characteristic.
10. The code scale of claim 1 , wherein the first circumferential surface is a polished surface.
11. The code scale of claim 10 , wherein the first circumferential surface defines one or more grooves.
12. The code scale of claim 10 , wherein the second circumferential surface comprises a first material, the first material being diffusely reflective with respect to incident light of a wavelength or a range of wavelengths.
13. The code scale of claim 12 , wherein the first material comprises at least one of a white polyurethane paint or a white photo-resistive material.
14. The code scale of claim 12 , wherein the third circumferential surface comprises a second material, the second material being light absorptive with respect to incident light of the wavelength or the range of wavelengths.
15. The code scale of claim 14 , wherein the second material comprises at least one of a black polyurethane paint or a black photo-resistive material.