Micro-encoder using image obtained by ball lens assembled inside wafer

An absolute micro-encoder based on the code imaging is developed. The ball lens (phi300 mum) is assembled inside the cavity between the pyrex glass lid and suspensions in the handling Si layer of the SOI wafer. The photodiode array is prepared in the device Si layer. The image of the scale is incident on the backside of the photodiodes. The electrical wiring to photodiodes does not disturb the optics. The current signal shows the sufficient contrast for resolving the maximum length code having the minimum line width of 13.6 mum