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Thread: No idea what this is good for but looks interesting!

  1. #1
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    Default No idea what this is good for but looks interesting!


  2. #2
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    funny though that the title says: " with IR filter" and later in the text it says: " ideal for IR transmitter and receiver".

    The thing is used to bounce a beam straight back to where it came regardless where it came from as long at it hits the retro reflector in the front. Like a mirror without having to adjust is.

  3. #3
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    "Output is strongest directly on axis, with output falling off as the angle of incidence is increased."

    That's not the whole story, and will be false if the source is a point source. If not false then useless anyway because the detector orientation alone will account for the efficiency because anything not shooting through the middle will be reflected back out parallel to input.

    Where the 'lensing' makes effect is where light from a large source is collected and the angles result in a lot of light being sent through the filter which I presume is IR pass, not block.

    A post I made in that 'Axicons' thread will help show this: http://www.photonlexicon.com/forums/...5993#post25993. A wide spread of incoming light increases its power at the centre. That example isn't a retroreflector, it's flattened and gathers light from a deliberately wide field, but it's the same idea.

  4. #4
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    Cool

    Most common use for one of these (at least in a laser projector) would be for scanner blanking using the optical lever technique discussed in this thread.

    The price sure seems cheap...

    Adam

  5. #5
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    my only sugestion is that if used in a projector be carefull about back reflections if using red diodes ...

    cos as we know they "dont like it up em Mr Manwaring"

    all the best .... Karl

  6. #6
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    Quote Originally Posted by Banthai View Post
    my only sugestion is that if used in a projector be carefull about back reflections if using red diodes ...

    cos as we know they "dont like it up em Mr Manwaring"

    all the best .... Karl
    That they don't, a touch of the old cold light gives them what for, don't you know.

    Actually that retroreflector might be ok, one of the things about a hole instead of a fine apex is it limits how close the returning beam can run beside the source beam. Still risky in casual use though because divergence might make enough light get back in.

    That laser blanker is a neat idea. I think it's maybe better as it is though, a retroreflector adds a third surface to bounce off (lossy) and makes it slightly harder to predict where the beam emerges. That awkwardness might be worse than having to carefully align the two-mirror reflector in that projector as it then needs precise positional and rotational adjustment.

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