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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. http://www.aaxatech.com/products/p2jr_pico_projector.html

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.
-Steve

7 comments:

  1. Clever. I am excited to see how it works.

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  2. One thing I thought of doing before, but haven't tried it yet, is designing a heatsink and having it printed in a fairly cheap metal like stainless infused bronze. Being completely custom, it could serve also as a bracket for holding the assembly together.

    Another thing that comes to mind is converting an ordinary FDM to print metal clay like this one: http://3dprinterplans.info/tag/metal-clay-3d-printer/

    I'm happy to hear that you're getting an even dispersion of light.

    Yes I'd be interested in the cure times for whatever resin you're using, since the SLA I'm building currently has a 5 watt LED installed. I'll mainly be using it to make microscopic items, so I think I'll have enough radiance for that, but it'd be something good to think about until I can get back to working on it in a couple of months.

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  3. Can't wait for your next blog, how do you plan turn on that uv led automatically via projector, will you use a micro controller to receive voltage signals from the previous R/B and G led connection pins, or plain transistors or optocouplers? I know you would have to use an another voltage source to power the uv led.

    also interested about the focusing of the projector's image at the minimum resolution @100 Micron, if the lenses would have to be place outwards from the projector to achieve focus.

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    Replies
    1. I believe the native resolution is 800x600, although I saw contrary specs that put it at 1024x768, which is the same resolution as my current InFocus 2104. As far as turing the LED on and off, it could be as simple as wiring it up to a switch. I may use the fan out put (M106/M107) turn turn it on/off at each layer as others have done. There's no need to wire it up to the original RGB signals since the output is monochrome UV and the DLP chip essentially acts as a mask, the fan output connected to a power transistor could also act as a brightness control since it's a PWM output.

      I'm currently in the process of designing a carrier for the heatsink, DLP & electronics portions. Now that I've gotten it working well enough to cure resin, the rest is all mechanical fabrication and a little wiring.

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    2. I'm in the process of building something similar to this but with a larger bed and more powerful LED's. In terms of switching the LED power I'm using this: http://www.powerswitchtail.com/Pages/PSTKKit.aspx

      Simply send a small signal from your RAMPs and the LED element of the projector will turn on and off.

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  4. cool, that sounds good. I will be waiting for an update on your progress. I hope all goes well!

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  5. Hi,
    UV DLP Pico Projector Experiments Part 2 is a nice blog. Inserting a 10W UV LED into pico projector is a good idea.Thanks for posting all the helpful information. Keep up the good work.


    Portable Projector

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