<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>In article <perplexed1.16a04v@physicsforums.com>, perplexed1\n<perplexed1@physicsforums.com> wrote:\n\n> I\'m attempting to do a project making an optical correlator with lenses\n> and film inputs and templates so that the system can detect whether a\n> picture is a match or not. When a filter is a match it produces a dot\n> at the other end of the stage, and when it doesn\'t, the light is\n> diffracted and disperses. I got this to work on matlab with a silly\n> program on jpegs, but I can\'t figure out how to do this with real\n> lenses for my experiment. My question is...what is a collimator, and\n> how should I go about doing this project if not in the set up given by\n> the picture below...?\n\n> http://www.eng.warwick.ac.uk/OEL/courses/undergrad/lec8/Fourier_lens.gif\n\nA collimator is something that gets all the light going in the same\ndirection in a parallel beam.\n\nIn this case, the collimator consists of the pinhole and the first\nlens. The pinhole should be at the focus of the lens so that light\nthat passes through the left side of the lens travels in exactly the\nsame direction as the light through the right side, etc.\n\nThis experiment is a bit tricky and requires accurate alignment.\n\nTo get the beam parallel, try setting up the collimator before the\nother lenses etc. so it can project onto a far wall. Put e.g., a\ncaliper set to 5 cm right next to the lens and make sure that its\nshadow on the wall is exactly 5 cm.\n\nTwists and changes in size of the input signal vs the spatial filter\ncan blur out the dot.\n\n--\nDavid M. Palmer dmpalmer@email.com (formerly @clark.net, @ematic.com)\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>In article <perplexed1.16a04v@physicsforums.com>, perplexed1
<perplexed1@physicsforums.com> wrote:
> I'm attempting to do a project making an optical correlator with lenses
> and film inputs and templates so that the system can detect whether a
> picture is a match or not. When a filter is a match it produces a dot
> at the other end of the stage, and when it doesn't, the light is
> diffracted and disperses. I got this to work on matlab with a silly
> program on jpegs, but I can't figure out how to do this with real
> lenses for my experiment. My question is...what is a collimator, and
> how should I go about doing this project if not in the set up given by
> the picture below...?
> http://www.eng.warwick.ac.uk/OEL/courses/undergrad/lec8/Fourier_lens.gif
A collimator is something that gets all the light going in the same
direction in a parallel beam.
In this case, the collimator consists of the pinhole and the first
lens. The pinhole should be at the focus of the lens so that light
that passes through the left side of the lens travels in exactly the
same direction as the light through the right side, etc.
This experiment is a bit tricky and requires accurate alignment.
To get the beam parallel, try setting up the collimator before the
other lenses etc. so it can project onto a far wall. Put e.g., a
caliper set to 5 cm right next to the lens and make sure that its
shadow on the wall is exactly 5 cm.
Twists and changes in size of the input signal vs the spatial filter
can blur out the dot.
--
David M. Palmer dmpalmer@email.com (formerly @clark.net, @ematic.com)