Tuesday, December 17, 2013

UV DLP Pico Projector Experiments Part 2

I know I left many of you hanging with my part 1 of the pico-projector experiments. To recap from part 1, I had successfully dis-assembled my pico-projector & examined the optic path, trying to determine how to insert a 10W UV LED into it all.

First, I'd like to offer a few words of caution. UV light can and will hurt your eyes. This is the exact reason why welders wear goggles. Sunburn on your eyes is no joke. I highly recommend wearing a good pair of sunglasses, or welding goggles if you have them.
Safety First...
 Last I posted, I was pointing out various bits of the optic path, and what they do. Shown below is a top-down view of the optic path of the axaa p2jr projector.

The L-Bracket with the LEDs has been removed.

 Initially, my efforts focused on attempting to collimate the light from a 10W LED into the existing port from one of the removed LEDs. The 10W UV LED I had purchased from Ebay had a 3x3 grid of individual LEDs. The actual emitter portion measured approximately 1cm across. I needed to channel this light somehow into an area approximately 4mm in diameter.

I tried several methods for building a suitable reflector/collimator, including dis-assembling and removing elements from various LED flashlights, and even building a simple light-pipe from acyclic rod.

In the end, I decided I was over-thinking it and decided to do something drastic.

Something drastic
I decided to remove almost the entire optic path. No mirrors, 1 lens. If you compare the above picture with the second picture I posted, you can see the portions of the optic path (and plastic)  that I removed. All that I left was a simple lens in front of the splitter/reflector portion of the DLP. Coincidentally, the lens in front was approximately 1cm across, which meant the LED was a good fit.

I taped over the lens while removing plastic

Most of the optic path removed.

 What I ended up doing was (temporarily) taping the 10W UV LED directly to the face of the lens prior to the DLP's splitter/reflector. This acted as a last-stage collimator to focus the LED's light onto the DLP chip and through the optics.

Projected onto a sheet of white paper.

A little light leakage around the edges can be fixed...
 Overall, I'm fairly happy with the way this turned out. The light emitted through the DLP was strong enough to cure resin (more timed tests are required) and it has even light across the image. The LED is was using was completely un-heatsinked, so it became very hot very quickly.

The next order of business is as follows:
1) Heatsink the LED (probably with a fan)
2) Build a mount for the DLP assembly / heatsinked LED

I'm currently designing a FDM 3d-printed 'carrier' right now.
Stay tuned for part 3, which will include some curing times and the initial design of a pico-SLA machine.