# Optics for projecting OLED screen DLP style

I just bought a small OLED screen and was wondering is it possible to make a screen surface a little bit bigger ( 2x ) by projecting it through some optics on translucent surface. It reminds me of viewfinders in some old cameras or SLR lens adapters or DIY LCD projectors.

Does it even make any sense?

I'm positive that some fresnel lenses will be needed but can't get a grasp on their configuration for this to work.

I've found pretty simple lens simulator and it makes it look like it can be done with only 2 lenses. But it don't seem right.

I know that with LCD projectors you need a fresnel lens and a triplet. Can it be simplified at the expense of image distortion?

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## 1 Answer

I'll compare the projector to the more appealing magnifying screen. A simplified approach would put a lens with low distortion within its FOV at a specific distance to the screen. Luckily these screen magnifiers are commercially available for a 12" display, about 40 US$\$\$.

Fresnel Lens basics

The principle of a magnifying glass with just one lens is applied. Remember the the thick and heavy lenses of a magnifying glass. Since its radius of curvature is defined by its focal length, a standard lens must have a certain thickness. Why does it show rings? That is the sections, where the lens is going over to the next lens segment. The following graphics depicts the mental process to create a Fresnel structure. Original lens function is maintained in a diminished effectiveness. Image taken from the website with further refraction basics. A Frensel lens may be used to get a thinner lens. Imagine slicing the thick lens in concentrical rings. Assemble their surface together in order to geht a thinner lens. This is the basic idea of a Fresnel lens. A very thin lens can be engineered on one surface of sheet of plastics.

The OLED screen can be magnified by the use of a Fresnel lens. Optics principle is just like a magnifying glas. However a needed focal length relates to a certain radius of curvature of the lens. A second criterion is to see the full OLED screen (field of view). This requires the lens to be of a certain dimension. To satisfy both criterion

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