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Thread: mRad calculation

  1. #1
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    Default mRad calculation

    Please double check my math.

    My size at aperture is 3.175mm (well...about an inch away)

    My size on the wall is 41.275mm

    My distance from the aperture of the projector to the wall is 13.716 meters

    I'm coming up with an mRad of 2.77.

    Does this sound correct? This is for a 520nm diode in a new Pluto II projector from Lightspace. I think there is something internally out of alignment and am going to be swapping it out with Omar but, curiosity made me want to go through the motions of checking it.

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ID:	44544 Green is the top line, blue in the middle, red on bottom of course

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    Thanks!

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    Default

    I'll also mention the vertical lines are tight. It's just the horizontal that seems waayyy too big.

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    Yep.

    (Assuming the source is purely divergent and there is no waist between measurement points - which is highly likely there will not be.)
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    if you look closely, all the beams are asymmetrical. it's most pronounced in the green, but it's very apparent in the word "TOP".

    Quote Originally Posted by Bradfo69 View Post
    Please double check my math.

    My size at aperture is 3.175mm (well...about an inch away)

    My size on the wall is 41.275mm

    My distance from the aperture of the projector to the wall is 13.716 meters

    I'm coming up with an mRad of 2.77.

    Does this sound correct? This is for a 520nm diode in a new Pluto II projector from Lightspace. I think there is something internally out of alignment and am going to be swapping it out with Omar but, curiosity made me want to go through the motions of checking it.

    Click image for larger version. 

Name:	IMGP8279.JPG 
Views:	16 
Size:	249.4 KB 
ID:	44544 Green is the top line, blue in the middle, red on bottom of course

    Click image for larger version. 

Name:	IMGP8270.JPG 
Views:	22 
Size:	201.6 KB 
ID:	44545

    Click image for larger version. 

Name:	IMGP8271.JPG 
Views:	10 
Size:	355.2 KB 
ID:	44546

    Thanks!
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    Consider turning down the scanner amplitude and swapping the X and Y scanner cables. See if the problem is shifted to the verticals. It would be odd that only the horizontal lines would be broad and in all three colors if the problem was with the individual modules. And, misalignment of the colors with zero power, flat optics should redirect, but not broaden.

    Also, you might insert a mirror that intercepts the mixed beam before it hits the scanner mirrors and send it to the same wall. This will also help to isolate the cause.

    You're calculation is correct. I have a personal pet peeve with divergence as a measure of beam quality; not that this necessarily has anything to do with your projector. If you took a pair of lenses and increased the diameter of the beam that is currently coming out of your projector by a factor of 4 to 12.7mm then the beam on the wall @ 13.716M will be 10.3mm and so the divergence will actually be negative. The beam has not changed in quality just in size. I like the beam product of the divergence x the beam diameter. This is harder to spin.

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    Quote Originally Posted by planters View Post
    Consider turning down the scanner amplitude
    Eric.... I need my english/tech speak - teck speak/english dictionary... (we're all not as smart as you are. ) LOL Do you mean "turn down the scanner speed?"

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    He means project a smaller image.

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    Thanks.

    Ok... I swapped the cables on X and Y. Here are the resulting pics:

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    Here is the green hitting the dichro face:

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    Here is a side by side of a standard pluto (532, 445 and 637 on the left and, 520, 462 and 637 on the right)

    Click image for larger version. 

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    Finally, my standard Pluto on the left and the direct diode on the right - which was my immediate cause for alarm. I KNOW buffo's are razor sharp as I saw them last Saturday night doing huge 20' x 30' projections.

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ID:	44552 Click image for larger version. 

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  10. #10
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    Regardless of scanner configuration, your green is much taller than it is wide, but only the green. So, the scanner mirrors are not at fault, or all the colors would be affected similarly. Seems like something just got misaligned somewhere, but I don't know what a "reference" all-diode Pluto would look like if it were perfectly aligned... the 520 and the 532 are different optical systems, after all. I'm sure Omar will take care of it, though, so let us know how it goes!

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