Results 1 to 4 of 4

Thread: CDRH ? on rear projection

  1. #1
    Join Date
    Mar 2005

    Default CDRH ? on rear projection

    Hello All,

    Am not new to the laser hobby...just now starting to explore possibillity of small side-line business.

    I have one of the original Gamma-XL projector systems( with blanking ). Up to this point I have only used as in-home unit...NO public displays. Projector is coupled to a 120mw DPSS@ 532.

    I have read and re-read the CDRH documment on Laser Display...Wow...
    Very detailed !!! But I cannot understand the rulings.

    My question is this : If a local retailler wanted to lease my equiptment for use as a rear projector of scrolling text ( Reverse image ) message in his front store glass a variance needed ???? The beam path would be terminated at the glass window pane by a translucent sheet of 1/8 lexan plastic placed INSIDE the window. The unit would only be energized AFTER the store was NO possibillity of the public comming in contact with the beam/display. The unit would be turned off prior to the store opening up in the morning.

    Is this considered "public display" ??? The translucent boundry plane breaks up the beam a " fuzzy " output on the side opposite
    the beam strike area...therefore, no coherent optical output.

    Anyone try this B4 ??? The one area of the CDRH document that I surly
    understand is the 30K fine for violation !!!!! I know this project is " small potatoes "...but...its a start...and when the Blue DI diode gets to a reasonable $...I'd like to be able to fund a RGB project with profit from previous purchases !!! It would also be a great thing to make a small profit while attempting to satisfy the complusive need for coherent light !!

    Thanks in advance !!!
    The Quantum well is deep, Photons for All !!!

  2. #2
    Join Date
    Jan 2006
    Charleston, SC


    Hi RDS;

    Interesting question you've got there. My gut reaction is to say that, so long as you can prove that the light exiting the window is under 5 mw, you'd be OK.

    In practice, however, I'd go a couple steps further. First, I'd set up the laser and the translucent plastic and use a power meter to determine how much light is actually getting through the window. If it is, in fact, less than 5 mw, then I'd call the CDRH and explain exactly what you are planning to do, and ask them if they have jurisdiction. My guess is they'll say no, on the grounds that you have less than 5 mw of power getting through the window. In that case, you're golden.

    On the other hand, if you're getting more than 5 mw through the window, I think you'll need a variance even though you've disrupted the spatial coherence of the beam. It's still a laser, and it's still over 5 mw, so the CDRH would have jurisdiction in my book.

    Either way, be sure to post back here and let us know what you find out. (Assuming that you actually talk to someone at the CDRH, that is.)

    BTW, the two times I've called the CDRH they were *very* helpful and quite friendly. They're not the big bad wolf at all. So don't feel bad about calling with a question or two. Just make sure you have all your questions ready, and try to anticipate the types of information they may ask of you so you're prepared...


  3. #3
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
    Join Date
    May 2007
    A lab with some dripping water on the floor.

    Red face

    I think the main question would be asked, how much exposure does someone get if the scanners fail and you get a dot. test the setup one night with 5 mils and see if it gets the job done then make a call.


  4. #4
    Join Date
    Mar 2005

    Default Dancing with the devil, by the pale coherent light !!

    I have some time to do some testing because the store owner has stated that it would be logical to use this type of display when we start to lose the long daylight hours of summer...say around September or October...when nightfall occurs around 7:00PM.
    The storefront window is approx 22' from a very busy 4 lane main road( I-24) in Monroe, the accidental projection of a 120mw beam could have very serious consequences !!! I would require the store owner to actually bolt down the system to limit the possibillity of misalignment and loss of beam termination.
    I have a Coherent 404 power I can check the mw output of the stationary beam as it exits the projector and propagates thru the translucent
    plane. I agree that it would just be professional to have all the operating conditions at hand prior to discussion with the CDRH.
    I am exceedingly concerned with liabillity, as you can well understand ! Firstly, I would NEVER want to cause anyone harm in anyway. Secondly,
    I am certian that if something bad were to occur, the resultant lawsuit would bankrupt me...or worse !!! These are sobering thoughts to consider....against the backdrop of likely small profit !!!...BUT....I think that this could possibly be a market that is currently untapped !!! I will continue to completely explore
    all the possible failure mechanisms.
    I WILL be checking with the CDRH and may request a written response from them...if they do such a thing. Possibly a variance would be the most legally
    prudent thing to go for ???? There IS commerce involved...but is the output>5mw????? Unknown at this time.
    It is good to hear that the CDRH is reasonable to work with !!! As previously noted: I'd just like this " hobby" to give a little I can justify likely
    thousands more !!!!!
    I will post on this forum as the process unfolds....under the current title !!

    RDS ...Bob ( AKA...CDBEAM )
    The Quantum well is deep, Photons for All !!!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts