by Din » Sun Sep 13, 2020 5:45 pm
lobaz wrote: ↑Sun Sep 13, 2020 2:29 am
Is it sensitive to angle of ilumination?
A common AgX volume hologram (Denisyuk type) illuminated by white light changes its color as the illumination angle changes. It is thus very sensitive to illumination angle for laser illumination - it either reconstructs well, or does not reconstruct at all.
But I have no experience with laser illuminated photopolymer Denisyuks.
Depending on the bandwidth, if a Denisyuk is laser illuminated, then the image will vanish over a range of about 5 - 10 degrees. This is because when you twist the Bragg planes, the illumination is off-Bragg. With no other wavelengths in the reconstruction, no other wavelengths will become on Bragg for a narrow band set of planes. According to Kogelinik, you can still reconstruct over a range of about δθ = 5 deg and about δλ = 5 nm. The dephasing parameter, ξ, can allow a small range with lower efficiency.
Photopolymers are necessarily narrow band because they don't need wet processing. That's the advantage of polymer for technical holograms, but a bit of a disadvantage for display holographers.
[quote=lobaz post_id=71930 time=1599982151 user_id=2217]
Is it sensitive to angle of ilumination?
A common AgX volume hologram (Denisyuk type) illuminated by white light changes its color as the illumination angle changes. It is thus very sensitive to illumination angle for laser illumination - it either reconstructs well, or does not reconstruct at all.
But I have no experience with laser illuminated photopolymer Denisyuks.
[/quote]
Depending on the bandwidth, if a Denisyuk is laser illuminated, then the image will vanish over a range of about 5 - 10 degrees. This is because when you twist the Bragg planes, the illumination is off-Bragg. With no other wavelengths in the reconstruction, no other wavelengths will become on Bragg for a narrow band set of planes. According to Kogelinik, you can still reconstruct over a range of about δθ = 5 deg and about δλ = 5 nm. The dephasing parameter, ξ, can allow a small range with lower efficiency.
Photopolymers are necessarily narrow band because they don't need wet processing. That's the advantage of polymer for technical holograms, but a bit of a disadvantage for display holographers.