Basically there are 3 different options to illuminate the SLM:
Option A – Using a polarizing beam splitter:
This is the preferred setup for optimal usage of the SLM. Our calibration files are created using normal incidence on the SLM. They have been tested also to maintain a linear phase response for the given phase shift up to an incident angle of 10º.
Drawback: You will loose some light due to the beam splitter.
Option B – Near perpendicular incidence:
If you need high light efficiency we recommend option (B). The incident angle should not exceed +/-10
Option C – Higher incident angles / 45°
For larger incident angles the SLM performance changes:
- the AR coating will not work as intended => strong front reflection and undesired interference effects between front and back reflection can occur.
- the optical path length within the LCOS display is larger => different phase response
- the birefringence of the LC molecules change => different phase response
- geometric distortions will happen, even though this could be compensated on addressed image level.
Some of the effects can in principle be compensated on SLM calibration level. If greater angles of incidence are required for your application, please contact us at slm@holoeye.com with the serial number of your SLM to support you in the process and inform you about the expected maximum phase response at your required angle.