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Thread: 1W 445nm projector system completed

  1. #1
    Join Date
    Mar 2008
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    Sydney, Australia
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    315

    Talking Single-colour projector system completed

    It's that time of year again! No, not Christmas holidays, but the time when commercial projects get set aside for a few days, and the projector and software get revamped. Since this system now includes components designed, built or sourced by several members here, I thought you might like to see the final result. Maybe it will give you some ideas for your own projectors, and I'm pleased to answer any questions you have.

    This system was developed for internal use as a reference projector for related software, also under development (watch out for that early next year). Of course, it also gets a little real-world testing at private parties! It includes a USB DAC based on a C-Media sound card, a 1W 445nm module based on a diode removed from a Casio XJ-A140 video projector, and a projector based on a MediaLas CatWeazle LCII galvanometer system. The projector has an ILDA-compatible input connector and features a sealed optical compartment with optional UV and ND filter attachment.

    The 1W 445nm module deserves special mention. This projector was originally designed around a 100mW 532nm DPSS module, but the poor modulation response of DPSS, and the recent low-cost availability of higher-power, nicer-colour direct injection 1W 445nm diodes prompted an upgrade. The 1W 445nm diode module is assembled in the existing housing, but simplicity and efficiency are greatly improved. It means that the large external diode and TEC driver is no longer required, because these functions are built in to the module which rungs from a small 5V power supply. The beam profile is approximately circularised by expanding the slow axis with an anamorphic prism pair, resulting in a beam diameter of ~4mm at the aperture, with less than 1mrad divergence.

    Special thanks to Andrew and James for the USB DAC idea, Dave for the diode/lens mount, Andrew for the diode driver, Simon for arranging the anamorphic prism pair group buy, and Zoof for the excellent free software we have used so far. Also, thanks to everybody who contributed to the discussion about 445nm diode mounting, collimation, and beam profile correction. Sharing the solutions to all of these problems, then having all the necessary parts available in individual quantities saves a huge amount of time. A project like this would not be feasible without it.

    Click image for larger version. 

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    Component side of the USB DAC showing the DC-DC converter, offset adjustment potentiometer, and differential line drivers which are suitable for driving long twisted-pair cables.

    Click image for larger version. 

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    Solder side of the USB DAC showing hand-wiring for this prototype. Production units would never be produced this way, but this is the fastest way to produce a single prototype.

    Click image for larger version. 

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    The USB DAC fits inside the original C-Media case, pictured here with USB cable and 5m CAT-5 twisted-pair cable with ILDA adapters. Up to 100m CAT-5 twisted-pair cable has been tested.

    Click image for larger version. 

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    A view inside the 1W 445nm module. You can see the anamorphic prism pair, diode and collimating lens in brass mount, diode driver board, and transistors for modulating the diode and TEC current.

    Click image for larger version. 

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    Testing the 1W 445nm module. You can see the beam profile is approximately circular, with 4mm diameter at the aperture and less than 1mrad divergence.

    Click image for larger version. 

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    A view of the projector internals. At the back, you can see the 5V power supply for the 1W 445nm module mounted on top of the galvanometer amplifier board.

    Click image for larger version. 

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    Another view of the projector internals. The components are mounted to a 6mm aluminium base plate, with 80mm spacers and another 6mm aluminium top plate for stability.

    Click image for larger version. 

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    The exterior of the projector is beige ABS with chamfered corners and molded fins, sharing the timeless elegance of computer cases and lab equipment of the last thirty years.

    Click image for larger version. 

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    The projector mounts on a pan/tilt adjustable tripod up to 2.5m high and is shown here projecting the ILDA test pattern in 445nm blue.

    Click image for larger version. 

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    The fan on the back panel has a filtered air intake and provides positive case pressure. The central slot visible here is the hot air exhaust.

    Click image for larger version. 

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    A foam-lined case for storage and transport of the projector, USB DAC, power and signal cables, ND filters and other accessories.
    Last edited by weartronics; 12-20-2010 at 23:21.

  2. #2
    Join Date
    Oct 2006
    Location
    Central Florida
    Posts
    7,067

    Question

    How come it project's green?
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  3. #3
    Join Date
    Mar 2008
    Location
    Sydney, Australia
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    315

    Default

    Quote Originally Posted by allthatwhichis View Post
    How come it project's green?
    Fair question The projector was originally based on a 532nm DPSS module, and the last few photos are from way back when. I tried to remove those pictures to avoid confusion, but it seems impossible to remove pictures from a post. You can see the new 445nm blue in a couple of the other pictures.

  4. #4
    Join Date
    Oct 2010
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    Athens, Greece
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    Default

    nice build!! i especially like the fitting inside the old dpss module

    is there some special kind of glue for the anamprphic pair or any general purpose glue would do?
    "its called character briggs..."

  5. #5
    Join Date
    Mar 2008
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    Sydney, Australia
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    315

    Default

    Quote Originally Posted by LaNeK779 View Post
    is there some special kind of glue for the anamprphic pair or any general purpose glue would do?
    Technically, you should use a special optical adhesive (e.g. Norland #61), which gives you indefinite working time with controlled shrinkage and is guaranteed not to outgas on anything. However, it's expensive and has a short shelf life.

    When the proper adhesive costs more than the optics it's mounting (such as this case), I use ordinary two part 5-minute epoxy . Never use cyanoacrylate glues (e.g. super glue, crazy glue), because it fumes a white film over everything (very popular in forensic labs for revealing fingerprints)!

  6. #6
    Join Date
    Oct 2010
    Location
    Athens, Greece
    Posts
    1,931

    Default

    i especially like your cost - benefit approach

    2 part epoxy it is then. thanks!!!
    "its called character briggs..."

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