Message from Peter Homer

[Yiing Lin <ylin@xxxxxxxxxxxxxx>]

>This is a little late but I thought I would add   something to this
>discussion . Sometime ago in the British stereoscopic society bulletin
>David Burder described fitting a black surround to a screen to produce an
>on screen window for some slides that lacked one buiot in. To his suprise
>though he found that instead a stereoscopic image was produced in the black
>surround albeit much dimmer than the rest of the screen.  He was at a loss
>to explain it but suggested that this meant that stereo images could be
>projected onto poople wearing black clothes.
>  Some time later I saw the same techniqe of a black surround to the screen
>used to produce a window at a British Midland group meeting . In order to
>project some 101X45 mm glass verascope slides. This worked as Burder had
>originaly intended and I could see no stereo image in the black surround.
>The only explanation I can think of was that Burders material was not
>completely matt .a gloss black would retain the polarisation of the small
>amount of light and not reflect any depolarised light as a gloss white
>surface would or even a coloured one. In fact a gloss black surface will
>more or less polarise the light it reflects if it is not already polarised.
>Depending on the angle of reflection being almost complete at the
>polarisation or Brewstwer angle ( I believe this is the same Brewster of
>stereo fame) which is about 55 degrees depending on the refractive index of
>the gloss layer and calculated from a formula known as Brewsters law. This
>actualy used to be a way to produce low intensity polarised light for
>scientific perposes in devices such as Biots polariscope.
>  Getting back to the subject at the ISU convention in Eastbourne UK three
>years ago Burder anounced that he had tried out projection onto
>                                                          people wearing black
>"T" shirts in a private session with a few other big names in stereo the
>only other one I remember being Susan Pinsky and apparently it worked well.
>Mind you
>as some one sitting next to me commented it may have just been a ruse to
>get Pinsky int a tight black "T" shirt.        P.J.Homer


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