OBJECT / / / / / V CAMERA PV wrote in article <3F04E711.2050407@hotmail.com>...[quote] > I am looking for a mirror that should be transparent from one side and > reflective from other side. Could anyone please help me where I can find > it? My application is to illuminate the object from the transparent side > and reflected image will be used from the other side for image[/quote] collection.[quote] > Thanks in advance > PV > >[/quote] [allowsmilie] => 1 [showsignature] => 0 [ipaddress] => [iconid] => 0 [visible] => 1 [attach] => 0 [infraction] => 0 [reportthreadid] => 0 [isusenetpost] => 1 [msgid] => <01c34216$0e827410$7551b80a@DAVID_LEE> [ref] => <3F04E711.2050407@hotmail.com> [htmlstate] => on_nl2br [postusername] => David Lee [ip] => davidlee_malver [isdeleted] => 0 [usergroupid] => [membergroupids] => [displaygroupid] => [password] => [passworddate] => [email] => [styleid] => [parentemail] => [homepage] => [icq] => [aim] => [yahoo] => [msn] => [skype] => [showvbcode] => [showbirthday] => [usertitle] => [customtitle] => [joindate] => [daysprune] => [lastvisit] => [lastactivity] => [lastpost] => [lastpostid] => [posts] => [reputation] => [reputationlevelid] => [timezoneoffset] => [pmpopup] => [avatarid] => [avatarrevision] => [profilepicrevision] => [sigpicrevision] => [options] => [akvbghsfs_optionsfield] => [birthday] => [birthday_search] => [maxposts] => [startofweek] => [referrerid] => [languageid] => [emailstamp] => [threadedmode] => [autosubscribe] => [pmtotal] => [pmunread] => [salt] => [ipoints] => [infractions] => [warnings] => [infractiongroupids] => [infractiongroupid] => [adminoptions] => [profilevisits] => [friendcount] => [friendreqcount] => [vmunreadcount] => [vmmoderatedcount] => [socgroupinvitecount] => [socgroupreqcount] => [pcunreadcount] => [pcmoderatedcount] => [gmmoderatedcount] => [assetposthash] => [fbuserid] => [fbjoindate] => [fbname] => [logintype] => [fbaccesstoken] => [newrepcount] => [vbseo_likes_in] => [vbseo_likes_out] => [vbseo_likes_unread] => [temp] => [field1] => [field2] => [field3] => [field4] => [field5] => [subfolders] => [pmfolders] => [buddylist] => [ignorelist] => [signature] => [searchprefs] => [rank] => [icontitle] => [iconpath] => [avatarpath] => [hascustomavatar] => 0 [avatardateline] => [avwidth] => [avheight] => [edit_userid] => [edit_username] => [edit_dateline] => [edit_reason] => [hashistory] => [pagetext_html] => [hasimages] => [signatureparsed] => [sighasimages] => [sigpic] => [sigpicdateline] => [sigpicwidth] => [sigpicheight] => [postcount] => 4 [islastshown] => [isfirstshown] => [attachments] => [allattachments] => ) --> One sided mirror - Photography

One sided mirror - Photography

I am looking for a mirror that should be transparent from one side and reflective from other side. Could anyone please help me where I can find it? My application is to illuminate the object from the transparent side and reflected image will be used from the other side for image collection. Thanks in advance PV...

  1. #1

    Default One sided mirror

    I am looking for a mirror that should be transparent from one side and
    reflective from other side. Could anyone please help me where I can find
    it? My application is to illuminate the object from the transparent side
    and reflected image will be used from the other side for image collection.
    Thanks in advance
    PV

    PV Guest

  2. #2

    Default Re: One sided mirror

    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.

    --
    [url]http://www.chapelhillnoir.com[/url]
    home of The Camera-ist's Manifesto
    The Improved Links Pages are at
    [url]http://www.chapelhillnoir.com/links/mlinks00.html[/url]
    New email - Contact on the Menyou page.
    "PV" <psivasamyhotmail.com> wrote in message
    news:3F04E711.2050407hotmail.com...
    > I am looking for a mirror that should be transparent from one side and
    > reflective from other side. Could anyone please help me where I can find
    > it? My application is to illuminate the object from the transparent side
    > and reflected image will be used from the other side for image collection.
    > Thanks in advance
    > PV
    >

    Tony Spadaro Guest

  3. #3

    Default Re: One sided mirror

    This is true, but you could get around the problem by shining a very
    directed, parrallel, beam of light through the glass and then taking the
    shot at an angle to the half silvered side.

    I think you would find it easier to just shoot the subject in a normal
    mirror, at an angle. If you possition the lights carefully you will be albe
    to light the subject with light reflected off the mirror without the light
    source appearing in the image. You can start with a light just next to your
    cammera, a standard flash for example.

    Luke

    "Tony Spadaro" <tspadaroncmaps.rr.com> wrote in message
    news:CJ5Na.230401$jp.6018994twister.southeast.rr. com...
    > 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.
    >
    > --
    > [url]http://www.chapelhillnoir.com[/url]
    > home of The Camera-ist's Manifesto
    > The Improved Links Pages are at
    > [url]http://www.chapelhillnoir.com/links/mlinks00.html[/url]
    > New email - Contact on the Menyou page.
    > "PV" <psivasamyhotmail.com> wrote in message
    > news:3F04E711.2050407hotmail.com...
    > > I am looking for a mirror that should be transparent from one side and
    > > reflective from other side. Could anyone please help me where I can find
    > > it? My application is to illuminate the object from the transparent side
    > > and reflected image will be used from the other side for image
    collection.
    > > Thanks in advance
    > > PV
    > >
    >
    >

    Luke Guest

  4. #4

    Default Re: One sided mirror

    Use a thin sheet of glass between the light source and the object at 45
    degrees to the line between them. A fraction of the light will pass
    through the glass and illuminate the object whilst the rest will be
    reflected at 90 degrees. Likewise with light returning from the object -
    part will be transmitted and will return along the same path to the light
    source whilst the rest will again be reflected a 90 degrees but in the
    opposite direction to that directly from the light source. Thus you divide
    the light into two at each pass through the mirror and separate the light
    from the object from the 'waste' light from the lamp. It's easier to
    imagine than to describe. I'm not good at ASCII art but the sketch below
    may help. This is the closest you will get to an "optical check valve".

    The mirror can either be a piece of plain glass, in which case you will
    maximize the illumination of the object, or else a partially silvered
    mirror in which case you will get less illumination but maximize the
    collection of light from the object. Plain glass is usually fine.

    This is a standard way of illuminating objects for microscopy or macro
    photography and also the principle of operation of the autocue and Pepper's
    Ghost.

    HTH

    David


    mirror (at 45 degrees)
    ^ /
    | /
    | /
    | /
    |/
    LIGHT - - - - - - - >/<-------> OBJECT
    /
    /
    /
    /
    /

    V
    CAMERA

    PV <psivasamyhotmail.com> wrote in article
    <3F04E711.2050407hotmail.com>...
    > I am looking for a mirror that should be transparent from one side and
    > reflective from other side. Could anyone please help me where I can find
    > it? My application is to illuminate the object from the transparent side
    > and reflected image will be used from the other side for image
    collection.
    > Thanks in advance
    > PV
    >
    >
    David Lee Guest

  5. #5

    Default Re: One sided mirror

    Right. If it were possible to truly do this, one could make Maxwell's
    demon, and end up with a really need solar power system.

    Joseph Meehan wrote:
    >
    > As the others have said, I don't think you can do exactly what you are
    > suggesting.
    --
    Don Stauffer in Minnesota
    [email]staufferusfamily.net[/email]
    webpage- [url]http://www.usfamily.net/web/stauffer[/url]
    Don Stauffer Guest

  6. #6

    Default Re: One sided mirror

    Using polarised light you could get quite close to using all the light. But
    probably the reflected light from the object of not completely polarised
    anymore....

    Rob.

    "PV" <psivasamyhotmail.com> wrote in message
    news:3F04E711.2050407hotmail.com...
    > I am looking for a mirror that should be transparent from one side and
    > reflective from other side. Could anyone please help me where I can find
    > it? My application is to illuminate the object from the transparent side
    > and reflected image will be used from the other side for image collection.
    > Thanks in advance
    > PV
    >

    H.J.P. Vink Guest

  7. #7

    Default Re: One sided mirror

    In <cdilks-B5C62F.05131304072003news.fu-berlin.de>, Charlie D wrote:
    >Here's one.
    ><[url]http://www.scientificsonline.com/ec/Products/Display.cfm?CategoryID=1928[/url]
    >41>
    This is a beam splitter. It does not work even to a partial extent as a
    check valve. The "loss" (diversion) along/from any given path would be
    the same in both directions.

    Optical check valves appear impossible to me because:

    Suppose you have a closed system which consists of a blackbody chamber -
    say, some isolated completely closed room. This room is at some
    certain temperature and blackbody radiation exists in it.
    Now, suppose you had an "optical check valve" wall and divided this room
    with it. There would be a net flow of energy from one side of the wall to
    the other. The temperature would rise on one side and fall on the other
    side. You would be able to string a pair of thermocouples in this room,
    one on each side, and have that turn en electric motor to do work. Or you
    could set up some other heat engine in this divided room to do work. Have
    the heat coming from friction in whatever work you are doing go into the
    hot side. Maybe the motor could just turn a fan or something decorative
    to demonstrate the principle.
    Obviously, this would have the entropy in the closed system decrease
    from where it was before the optical check valve started doing its thing.
    And it would be a perpetual motion machine. As far as I understand it,
    the assumption that such things cannot work has been used to prove
    Einstein's photoelectric loss, and a similar (bandwidth and intensity
    dependent) loss in photovoltaic semiconductors.

    This brings me to directional couplers (a radio frequency device) which
    I have heard of but I don't know exactly what they do nor how they work.
    But if you had a divided blackbody chamber with blackbody radiation
    including some radio frequency, I doubt you can make a perpetual motion
    machine by putting an antenna in each side and putting a directional
    coupler between them.

    - Don Klipstein (donmisty.com)
    Don Klipstein Guest

  8. #8

    Default Re: One sided mirror

    I really like to try this Brewster's Mirror. Could you or someone please
    help me get one.
    Thanks you all the others for your valuable discussion and ideas.
    I wonder, whether I can find a beamslitter which should has one side
    with higher transparency and other side with higher reflection.

    Where can I find such a beamsplitter? Any help.
    Thanks in advance.
    PV

    David wrote:
    > I believe the mirror in question would be a Brewster's mirror. These are
    > used in LASER applications and are very common. I have several 2 inch square
    > ones now. They came from old grocery store check stand scanners. You should
    > be able to find them at a LASER hobbyist store. :)
    >
    >
    PV Guest

  9. #9

    Default Re: One sided mirror

    >
    > Sorry, this won't work. The simple fact is that there is no such thing as
    an
    > optical element that is transparent in one direction and reflective in the
    > other.
    >

    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:

    (usual physical terminology would be 'emissivity' rather than 'absorption',
    but the two are aways equal)

    Conservation of energy says that transmission through the entire optical
    system must be the same from both directions (as someone suggested look up
    'Maxwell's demon' if you want convincing).

    Conservation of energy (COE) does not imply that the other optical
    properties of the surfaces must be the same. What it does say is:

    transmission + reflection + absoption = 1

    (it is worth noting the reflection may be diffuse or specular, that doesn't
    effect COE but does effect the optical properties.)

    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.

    Yes there is no such thing as a perfect one way mirror, but they do only
    function as a mirror from one direction.

    Luke




    Luke Guest

  10. #10

    Default Re: One sided mirror

    On Sat, 5 Jul 2003 07:06:29 +0000 (UTC), "Luke" <luke_a_photmail.com> 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
    [url]http://www.cloudbait.com[/url]
    Chris L Peterson Guest

  11. #11

    Default Re: One sided mirror

    [email]donmanx.misty.com[/email] (Don Klipstein) writes:
    > This brings me to directional couplers (a radio frequency device) which
    >I have heard of but I don't know exactly what they do nor how they work.
    There are a number of different ways to build directional couplers, but
    (as you surmised) they don't provide a perpetual motion machine, nor are
    they a one-way valve. They just control where a signal goes to.

    One type of directional coupler is the splitter/tap used in cable TV
    systems. A signal that arrives at the "input" is distributed to each
    of the "outputs" in a specified power ratio. If the splitter is on
    the pole in front of your house, there's one output that receives
    almost all the signal, which is the main cable feed continuing down the
    street, and one or more house-feed taps that may get a signal that's 20
    or 30 dB down from what's on the main cable. But it's a passive device,
    so the sum of the signal power in all of the outputs is always less than
    the input power.

    Its use as a splitter is pretty mundane, but any passive splitter also
    works as a combiner when the signals arrive from the other direction. A
    signal coming in one of the "outputs" is passed through to the "input",
    without also being fed to the other "outputs". In other words, a signal
    headed "upstream" continues upstream, without the other "downstream"
    outputs seeing it. That's why it's called a directional coupler:
    direction of the signal matters.

    Dave
    Dave Martindale Guest

  12. #12

    Default Re: 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" <luke_a_photmail.com> 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
    > [url]http://www.cloudbait.com[/url]
    PV Guest

  13. #13

    Default Re: One sided mirror

    In article <CJ5Na.230401$jp.6018994twister.southeast.rr.com> ,
    "Tony Spadaro" <tspadaroncmaps.rr.com> 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)
    Daniel P. B. Smith Guest

  14. #14

    Default Re: One sided mirror

    On Sat, 5 Jul 2003 19:37:31 +0000 (UTC), [email]davemcs.ubc.ca[/email] (Dave Martindale)
    wrote:
    >Chris L Peterson <clpalumni.caltech.edu> writes:
    >
    >>A Brewster window is very useful when
    >>working with lasers, as it provides a mechanism for getting the beam out of a
    >>sealed tube without losses.
    >
    >Isn't it also what's used to force a beam to be polarized in the first
    >place? The idea that a piece of glass at Brewster's angle allows one
    >polarization to pass back and forth without loss, while the orthogonal
    >polarization suffers some loss in each pass and is attenuated to
    >extinction. This works with external-mirror lasers, where the Brewster
    >window is part of the tube envelope, and with integral-mirror lasers
    >where there's just a piece of glass at the right angle inside the tube.
    Exactly. And since the stimulated emission (the SE in LASER) maintains the
    polarization of the stimulating photon, the polarization selected by the
    Brewster window ends up being the only one the cavity will support.

    _________________________________________________

    Chris L Peterson
    Cloudbait Observatory
    [url]http://www.cloudbait.com[/url]
    Chris L Peterson Guest

  15. #15

    Default Re: One sided mirror

    On Tue, 08 Jul 2003 00:44:22 -0000, James Horn <jimhornsvn.net> 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
    [url]http://www.cloudbait.com[/url]
    Chris L Peterson Guest

  16. #16

    Default Re: One sided mirror


    "James Horn" <jimhornsvn.net> wrote in message
    news:vgk4v64fp0ah23corp.supernews.com...
    > 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.
    >
    > For radio frequencies, look up "circulators" - a staple in microwave
    > systems.
    It will *not* work with the sugar solution or any other optically active
    material.
    It has to be a material exhibiting the Faraday efffect, in a magnetic field,
    often a high Verdet constant glass (often Tb doped) or crystal (a garnet as
    I recall.)
    Microwave circulators & isolators use the same effects in ferrites, & also
    need a magnetic field.

    Harvey



    Harvey Guest

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