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#11
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One sided mirror
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#12
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One sided mirror
Thank you all. I am going to try both the Brewster's mirror and 5the
0/50 beam splitter. If anyone (mmm..Laser people:-) has any idea where I can get the Brewster's mirror, please let me know... I really like this thread to go on and discuss further, since I am interested in knowing any other solutions for this problems/or similar. It is really great to read all your valuable ideas...and Thanks YOU ALL againa and again. PV Chris L Peterson wrote: On Sat, 5 Jul 2003 07:06:29 +0000 (UTC), "Luke" wrote: This is true, but you can get an element which has the same transmission from both directions but also high reflectivity on one side and low reflectivity but high absorption on the other: Sure, the best example being a plate of matte black material that is aluminized on one side. [Approximately] 100% reflective on one side, 100% absorptive on the other. But it sure doesn't do what PV is looking for! I think the best he's going to get is 50% reflectivity, 50% transmissivity. So it is possible to have a sheet of glass that is say 50% transmissive in both directions and 50% reflective from one side but 0% reflective and 50% absorbative from the other side. This is what people try to achive when making one way mirrors. I think typical one-way mirrors are more like 75% reflective. And they don't have any preferred side- you can install them either way and they work just the same. _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
#13
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One sided mirror
In article ,
"Tony Spadaro" wrote: SO called one way mirrors are actually half silvered. THey are partially transparent on both sides (which if you think about it, is the only posible way). The side that is lit is visible from the side that is dark. Change the lighting so the dark chamber is light and the light one goes dark and the "transparancy" will shift. All those movies with one way mirrors are very inaccurate unless the viewing room is shown as being dark. Such a mirror plays a role in Arthur C. Clarke's novel "Childhood's End." The protagonists have interviews with an alien creature who will only talk to them from behind a pane of "one-way" glass. So they smuggle in very bright battery-powered light concealed in an attach case. The light has a hood arrangement; by jamming it against the one-way glass and turning it on, they light the room on the far side brightly enough to see what's in it. Another thing to be noted about "one-way" mirrors is that in real life they're usually easy to spot, for a couple of reasons. First, if you start paying attention to how _bright_ the reflection in a mirror is, you'll see that for a real mirror, the reflection is _almost_ a match for the scene being reflected, looking only _slightly_ dimmer. In a "one-way" mirror the reflectivity is usually low enough so that the reflection looks suspiciously dim, noticeably dimmer than the scene being reflected. Other giveaway, of course, is that such mirrors are often in locations that aren't very logical places for mirrors. And frequently are mounted in a frame that looks much more like a windowframe than a picture frame. I remember an airport in Venezuela that had a whole row of "mirrors" that were mounted on a wall about fifteen feet above the floor. Of course, it's quite possible that they didn't care at all whether people thought they were mirrors; the important thing was that you couldn't tell whether or not you were being watched. -- dpbsmith at world dot std dot com (replace "at" with at-sign and "dot" with period and remove spaces) |
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One sided mirror
On Tue, 08 Jul 2003 00:44:22 -0000, James Horn wrote:
By the way, non-reciprocal optical devices exist and are available. For instance, if you have a two polarizers in parallel with their axes rotated 45 degrees from each other and put a polarization rotating medium between them that rotates the light 45 degrees (a solution of sugar for home experimenters), light travelling one way will only have the ganged polarizer loss (about 50%) but the other way will see *crossed* polarizers (over 99%). Small units for directional control in fiber optics are available off the shelf. Unfortunately for the original poster, however, such devices won't do what he wants. I don't know of anything that can do this with white light that has scattered off a random object (like a person) of varying color and texture. There might be some exotic non-linear optical element like this, but certainly not something the size of a normal mirror! _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
#16
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One sided mirror
"Daniel P. B. Smith" wrote:
[snip] I remember an airport in Venezuela that had a whole row of "mirrors" that were mounted on a wall about fifteen feet above the floor. Of course, it's quite possible that they didn't care at all whether people thought they were mirrors; the important thing was that you couldn't tell whether or not you were being watched. Post offices use these quite often. They are used by postal inspectors looking for theft. The employees know what the mirrors are for but have no way of knowing when inspectors are watching them. -- Paul Hovnanian ------------------------------------------------------------------ Where am I going, and what am I doing in this handbasket? |
#17
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One sided mirror
? "Paul Hovnanian P.E." ?????? ??? ?????? ... "Daniel P. B. Smith" wrote: [snip] I remember an airport in Venezuela that had a whole row of "mirrors" that were mounted on a wall about fifteen feet above the floor. Of course, it's quite possible that they didn't care at all whether people thought they were mirrors; the important thing was that you couldn't tell whether or not you were being watched. Post offices use these quite often. They are used by postal inspectors looking for theft. The employees know what the mirrors are for but have no way of knowing when inspectors are watching them. -- Of course, George Orwell thought of that first:_)Big Brother is watching you! -- Tzortzakakis Dimitrios major in electrical engineering mechanized infantry reservist hordad AT otenet DOT gr |
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