Getting the most of cheap glass scales

I had an idea on my mind for a while: trying to get more resolution from basic 5um glass scales by interpolating the signals, like Heindenhain does. For most manual machines 5um resolution is enough, but for closing position the loop increased resolution is allways welcome, as the awesome MESA borads will be able to handle pulse rate. This will not increase the overal accuracy of the machine, but improve the movement on the very small steps and reduce the deadband and oscillations.

Recently I got a Ditron 0.1um scale, and idiot me crashed it while doing some testing to repair a servo encoder. Thanks to this I have dissasembled it and the reader itself is the same as other scales. The read singals are sent into a PCB on the reading head. On a 5um scale, the singals go through a comparator and you get the 5um resolution reading the quadrature 0.02mm marks on the glass. On a lower resolution unit, the signals are sento into an IC that does the interpolation. I will check the shape of the signals on the photodiodes wiht my oscilloscope, to check the shape. Hopefully is kinda sinusoidal, but could be triangular too. If anyone with a 5um unit does the same will great. I have found a couple of open hardware interpolators PCBs aimed to work with Heidenhain scales, using the IC-NV chip.

My 0.1um scale cost 4 times more than a 5um one from the same brand. For me that have very little free time and I'm not an expert on electronics makes more sense to just buy the high resolution ones, but I think many people who already has 5um scales or are in a budget will benefit. Let me know your thoughts on it.