Z Axis Optical Fine Adjustment

After making my own version of a compact Z axis adjustment, I upgraded Marlin and started using Mesh Bed Leveling. As MBL allows for height adjustment both above or below Z MIN, I was concerned about depressing the end stop limit switch beyond its limit. Using an optical sensor allows depth below 0 without harm.

The knob was created using the same knurled geometry from the MakerBot Knurled Surface Finishing Library Nut and Bolts. https://www.thingiverse.com/thing:9095 The first photo shows