Programmable freeform optics with extended white light sources: possibilities and limitations

Area of Science:

• Optics and Photonics
• Illumination Engineering
• Computational Optics

Background:

• Freeform optics offer precise illumination pattern generation from compact sources like LEDs.
• Dynamic illumination requires time-variable optical functionality, a challenge for traditional optics.
• Existing spatial light modulators (SLMs) are limited to monochromatic, low-étendue, paraxial conditions.

Purpose of the Study:

• To develop a novel algorithm for calculating smooth phase patterns for arbitrary illumination.
• To enable dynamic, non-paraxial beam shaping using SLMs as programmable freeform optics.
• To experimentally validate the algorithm's performance with laser beams and LEDs.

Main Methods:

• A new algorithm for calculating smooth phase shift patterns for arbitrary target illumination.
• Implementation of calculated phase patterns on a phase-only spatial light modulator (SLM).
• Experimental analysis of generated patterns using collimated laser beams and white LEDs.

Main Results:

• Demonstrated generation of arbitrary illumination patterns under non-paraxial conditions.
• Validated performance of the algorithm on a real SLM with a maximal phase shift of 6π.
• Identified limitations related to target angular extent, light source spectrum, and incident beam étendue.

Conclusions:

• The developed algorithm allows SLMs to function as programmable freeform optics for dynamic lighting.
• The method overcomes limitations of previous SLM applications, enabling non-paraxial and broader spectral use.
• Critical analysis provides insights into the practical possibilities and constraints for accurate pattern generation.