I am looking for a somewhat cheap way of measurin small distances ( >0.1 inch) between an object and a sensor, are there any good ways to do this? I am considering the component from a flatbed scanner, but I am not sure how I would make use of this. It would be preferred to use some kind of mechanism that uses absolute positioning, so it doesn't get thrown off, but a very accurate absolute positioning method would work too. Suggestions would be appreciated.
If contact is okay, you can use a digital dial indicator. They use an incremental measuring method internally so they need to be zero'd. Accuracy is about 0.001" for the cheap ones and range is typically at least an inch.
Price ranges from about $25 to $500 depending on brand and performance.
You can interface to the internal battery-powered electronics- they usually have a proprietary serial interface with 1.5V levels. There are a few standards for the interface- Mitutoyo is one- and the Chinese ones are generally similar to each other (and different from Mitutoyo).