I have an LED with a beam angle of 120° and I need to illuminate an area in the shape of a circle with a radius of 3.5 mm.
My objectives are as follows:
- Achieve a uniform illumination of the circle (Is "perfect" uniform illumination even possible, and is there always some variation in brightness towards the center?).
- Ensure that the diffuser itself is uniformly illuminated for aesthetic reasons and to instill confidence in observers that the circle is also uniformly illuminated.
- Maximize the light intensity at the circle.
Initially, I considered not using a diffuser and instead placing the circle at a distance of 2.02 mm ($\frac{3.5 mm}{tan(60°)}$). However, this approach is visually unappealing as it exposes the LED to the observer.
During my experimentation, I encountered a multitude of adjustable parameters, including the material and thickness of the diffuser, the distance between the diffuser and the LED, and the distance between the diffuser and the illuminated circle.
My questions are as follows:
- Are there any general guidelines or rules of thumb for optimizing the parameters? For example, is it advisable to place the diffuser 2.02 mm away from the LED and then position the illuminated area directly on the diffuser?
- What are the key properties of a diffuser that should be considered, and how do they influence the optimal placement of the diffuser?
- Would there be any advantage in using two diffusers—one close to the LED to scatter the light and another close to the illuminated area for aesthetic purposes?
Regarding the diffuser material: It should also work with IR and UV light (or at least be transmissive to it) and in warm (30-40°C) and humid environments.
Thank you.
