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Thread: Scan Size Calculation Problem

  1. #1
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    Default Scan Size Calculation Problem

    Hi,

    I'm having some trouble calculating and adjusting scan size so would appreciate some help.

    I've had some tails on some displayed patterns and although the scanners aren't complaining I'm suspecting scan angle problems.

    So I decided to use the angle calculator off here to calculate the angle.

    The problem is I'm getting a ridiculous result and so wondering if I'm doing something wrong.

    The distance laser to wall is 274cm

    The Test Pattern displays at 60cm square - calculator says square units so = 3600 units squared (? (60x60) correct figure used or should it be 60)

    According to the scan angle calculator that gives a scan angle of 162.69 degrees

    Yet the pattern on the wall doesn't look very wide at all and the scanners aren't complaining and displaying a perfect ILDA test pattern. I reckon you wouldn't even see it at 7 degrees at that rate.

    I'm presuming I'm doing something wrong here therefore.

    Anyone help?
    Last edited by White-Light; 10-29-2011 at 04:16.

  2. #2
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    Default

    Hi Al

    Rob used to do a scanangle chart, may even have been available as a .pdf

    This takes all the hard work out fo calculating scan angles. You basically put it at a set distance from your projector and adjust your image to fit one of the pre-drawn squares on the chart. This then tells you the exact scan angle without the measurements.

    I've had a look for it on Rob's website but it doesn't appear to be there. I know he was giving these away at one of the early LEM's, perhaps you could drop him an email.

    Have you had a look at the software settings, things such as line anchors and visible line settings. Adjusting these may possibly help.

    I'm sure I have a chart here somewhere if you're unable to get one, just let me know and i'll have a hunt for it.

    Cheers

    Jem
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.... Douglas Adams 1952 - 2001

  3. #3
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    Default

    Rob posted this many moon Lumens ago....

    i hgave always found this helpfull

    make sure when you print it out that the line at the right is 10cm long this will make sure its the right scale
    them place the printout at 30cm from galvo mirrors

    and bobs ya uncle ... or better "Stans" ya uncle


    Click image for larger version. 

Name:	scananglechart[1].pdf 
Views:	29 
Size:	12.6 KB 
ID:	28271Click image for larger version. 

Name:	scananglechart[1].pdf 
Views:	29 
Size:	12.6 KB 
ID:	28271

    all the best ...

    Karl

  4. #4
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    Default

    bloody hell jem ... we must be typing in stereo

  5. #5
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    Default

    Hi Jem,

    I've got the pdf but unfortunately it requires A3 paper and my printer is A4.

    I'm also scared of setting it on fire from 30cms. I'm burning wood in under 1 sec from 10 metres, albeit with a pencil rather than modulated beam.

    I know everybody raved about this calculator so it should work but clearly something is going wrong. I can't see my LM's displaying a perfect ILDA test pattern at 162 degrees or any pattern at all. Problem is I'm not sure where I've gone wrong, probably something simple but...

  6. #6
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    Im guessing that you have doubled the scan angle +/- 81 degs

    im sure it wont be 162 deg as that would be near impossible for the scanners thats nearly half a semi circle

    Karl

  7. #7
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    BTW Karl thanks for putting the pdf up we cross posted.

  8. #8
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    They're rated for ILDA test pattern at 7 degrees and 30K.

    That's why I can't understand how ilda test pattern can display if its 162 degrees plus it doesn't look very wide on the wall. Confused.

  9. #9
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    No Probs ... seems like me you and Jem are getting our "saturday afternoon internet time"

    im guessing that the angle you are getting is half ... +/- 40.5 deg...... total 81 deg .....

    Be carefull as that is a high angle and will make the scanners work very hard

  10. #10
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    if you print off Robs scan angle with no scaling .... it should print the left hand side on an A4 sheet .... then you can print off a second copy turn it round and selloptape them together
    if you are using the test pattern which will be scanned .... ther is very little chance of it catching fire .... unless you are doing this on a Laserscope

    Karl

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