Finding: Canon S16 Lens
I acquired an intriguing lens from Canon, with very unusual amber AR coatings.
Full markings: CANON S16 LENS No. 200017 JAPAN
Empirical measurements
M26 thread, Mitutoyo form factor.
Identified as an 5x infinity-corrected objective designed for an f=200mm tube lens.
The image in broadband light is very poor (strong chromatic aberrations) but very sharp in monochromatic light.
Overall, after some testing side by side with a Mitutoyo M Plan Apo 5x/0.14 (Mit5), I can state the following:
- 5x magnification
- Shorter working distance than Mit5
- Around 27mm WD (VS 34mm for Mit5)
- Much sharper than Mit5 in monochromatic light
- N.A. > 0.14
- Strong lateral and longitudinal CA
- Suggests intended laser usage or UV illumination
- Flat field over a large image circle
- Poor IR performance
- Almost zero contrast at 1050nm (where the Mit5 remains usable)
- Lower transmission than Mit5 at same exposure in the Red to IR range
- Excellent UV/Green performance
- Very good contrast at 386nm, high contrast
- Higher transmission than Mit5 at same exposure in the UV to Green range
- Amber coatings suggest an UV/Green pass filter
Images
Unprocessed cropped images (RAW) from the sensor.
Only gamma correction was performed.
Comparison with Mit5 (above) in narrow band 545nm.
Excellent performances in the UV 386nm.
Very strong CA in wideband illumination.
Very low contrast in the IR 1050nm.
For comparison the Mit5 is totally usable in the IR 1050nm.
Potential origin
If we consider the lens as an UV objective, a possible origin could be from a photolithography stepper or related equipment.
In fact, Canon have a page about their Semiconductor Lithography Equipment.
Though photolithography lenses are usually much bigger, so it’s real use is still a mystery.