edge shape instead of slots #11
Description
Instead of passing a slot between the light source and sensor, blocking and passing light with an edge that passes through the gap side to side, we can interrupt the light by changing how far the edge of the disk passes into the slot; blocking and passing light with an edge that extends into the gap, more or less. Imagine a disk with no slots, but an edge with a "ruffle" on it, or a very thin gear.
There would be several advantages:
- Slots are more likely to hold gunk or fuzz causing a change in the light levels at that "eye"
- The shape can probably be adjusted to produce the desired sine wave without a special mask ( see Rectangular slits make square eyes, not round. #3 )
- Not needing the outside rim, means the disk can be a little smaller
The disadvantage is that the correct shape is difficult to calculate since it interacts in two dimensions instead of one. This is less of a problem when the number of "non-slots" on the disk are lower and the mask on the sensor is very narrow. However, fewer "non-slots" means lower resolution, and a narrow mask reduces light levels, lowering bandwidth, which again reduces resolution. So doing the work to calculate the correct shape is probably worth it.
It's also less structurally sound. Probably. Maybe not.