Results 1 to 7 of 7

Thread: Need help with power measurement issue

  1. #1
    Join Date
    Jul 2008
    Posts
    108

    Default Need help with power measurement issue

    I have this Chinese 473nm laser. It's supposed to be rated at 100mw (roughly). I have a new Coherent lasercheck as well with it's NIST documentation. When I measure the output at 473nm it says 66mw. When I change the line to 445nm it says 116mw.

    My questions are:
    Is the line coming out of the LBO crystal REALLY 445nm?
    Or is the laser just a dud because it's not outputting 100mw @ 473nm? OR, is my lasercheck out of calibration?

    What do you think?

  2. #2
    Join Date
    Feb 2007
    Location
    Herts, UK
    Posts
    1,254

    Default

    Given those 3 possible options, I'm leaning towards the below spec output laser one.
    Have you given it enough warm-up time? Some take ages to settle...

  3. #3
    Join Date
    Jul 2008
    Posts
    108

    Default

    Quote Originally Posted by p1t8ull View Post
    Given those 3 possible options, I'm leaning towards the below spec output laser one.
    Have you given it enough warm-up time? Some take ages to settle...

    I'll leave it on for a few hours. See what happens.

  4. #4
    Join Date
    Jan 2007
    Location
    Sheepsville, Wales, UK
    Posts
    3,406

    Default

    The blue will most certainly be 473nm, and as P1t8ull says its likley to be a low power output - let it warm up and see if it settles or improves.
    The reason you see higher readings when you change the wavelength is due to the lasercheck. The problem being that the lasercheck reads way off the mark if the wavelength is not correct. As an example if I measure a 532nm Laser that has some ir content in the output beam I can get readings of over double what the laser is rated at. If I then use a dichro to filter the green out and let the ir through, measuring this ir with the LC set to 1064 gives me a reading of only a few 10's of mW at most.
    Some less than honest sellers use this 'feature' to make crazy claims about the output of lasers they are selling, mainly on everyones favorite online auction site.

    Rob
    If you need to ask the question 'whats so good about a laser' - you won't understand the answer.
    -----------------------------------------------------------------------------------------------
    Laserists do it by the nanometre.

    Stanwax Laser is a Corporate Member of Ilda

    Stanwax Laser main distributor of First Contact in UK - like us on Facebook http://www.facebook.com/FirstContactPolymerCleaner
    www.photoniccleaning.co.uk

  5. #5
    Join Date
    Jul 2008
    Posts
    108

    Default

    After heating up, it got to around 73mw at 473nm. Considering the money I paid for the thing...I'm still the winner.

    Thanks Stan. Your experimental example using the dichro and the LC cleared up a lot of questions for me. The LC is really a computer that relies on the manual wavelength setting to make it's assesment based on the heat from the sensor. Any deviation throws off it's internal tables.

    Makes me wonder what the people who CLAIM to measure the power output of these cheap Chinese lasers are using to test the milliwattage?

  6. #6
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,489,446

    Cool

    Quote Originally Posted by FrankenPC View Post
    The LC is really a computer that relies on the manual wavelength setting to make it's assesment based on the heat from the sensor. Any deviation throws off it's internal tables.
    Yep. You got it!
    Makes me wonder what the people who CLAIM to measure the power output of these cheap Chinese lasers are using to test the milliwattage?
    What makes you think that some of them even bother to check?

    Seriously though, what Rob was talking about is the nasty habit that a lot of E-bay sellers have of removing the IR filter on a DPSS green laser and then posting a picture of the beam hitting the laser check. Of course, with the IR filter removed, the lasercheck is going to read crazy high, because of all the extra IR hitting the sensor. (especially when the computer is set for 532 nm!) So you get a reading that is 4 to 10 times higher than actual.

    Makes for a great looking E-bay ad, but when you actually receive the laser, it's painfully obvious that the laser isn't making anywhere near it's rated optical output. But by that time it's usually too late.

    Bastards...

    Adam

  7. #7
    Join Date
    Jul 2008
    Posts
    108

    Default

    At least this guy has the courtesy to install a IR filter.

Posting Permissions

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