Holographic Patterning of Diffractive Optical Elements for Beam Shaping in Lighting Applications—A Dual-Hologram Approach

The widespread use of Light Emitting Diodes (LEDs) in contemporary applications is a result of their many advantages such as cost-effectiveness, mass manufacturability, long lifespan, versatility, and lightweight construction, it has made them the preferred light source in many imaging lighting and projection systems. Holographic Optical Elements (HOEs) are optical elements fabricated using holographic techniques to pattern relatively large areas in low-cost optical films. They have potential in applications where lighting or displays would benefit from a shaped output that targets a specific audience location or illuminated zone. Bespoke elements can be mass produced with whole-field optical patterning using laser exposure energies of just a few milijoules (mJ), with the potential to reduce light pollution and increase energy efficiency. As such, HOEs present a promising approach to providing low-cost optical films for shaping LED sources. In this paper, holographic recording is used to separately fabricate two HOEs which are then stacked to shape LED light. We report (1) a HOE combination that produces an on-axis collimated output from a divergent LED input beam and (2) a HOE combination that converts a diverging input beam into a structured beam determined by a Spatial Light Modulator (SLM). Output beams showing images and text highlight the flexibility that can be achieved to pattern and eventually shape the output from an LED source for bespoke lighting and display solutions. The dual-hologram approach could also simplify mass-production with the first hologram tailored to the LED source and the second to the desired output beam.