Home Return to Main Page
PULSE COLOR HOLOGRAPHY
Red-Green-Blue Full color pulse holography.
A RGB laser was created using a Nd:phosphate laser http://www.spie.org/web/techgroups/holography/pdfs/Holography1-11.pdf. This system generated RGB wavelengths of 670/531/411 nm claimed by the authors. The paper seems to have some documentation issues for example 411nm is the first stokes line not the quoted anti-stokes line of 351nm based on H2. Additionally the KTP would double the 1054 oscillator laser output to 527 not the 531 as indicated in the text and yes the THG of 1054 is 351 which suggests 1054 is the oscillator as indicated by the authors. The output of the first stokes of 527 and 351 and along with the SHG would yield a RGB of 675/527/411. Overall the output power and the system was impressive.
A ruby laser could also be made RB as follows: Ruby output would be SHG to 347nm then a Stimulated Raman Scattering technique using Hydrogen srs.xls for the first stokes line could be used to generate the violet/blue of 406nm and when combined with a SHG Nd:YAG laser would allow RGB holography of 694/532/406 nm wavelengths. The above spreadsheet estimated about 260mj output with 80 to 90mj per primary color when using a 1.5joule ruby and 80mj Nd:YAG laser. After experienced gain with the below RG system, then a RGB system can be attempted as described. SHG of the ruby will be done with a 15mm x 30mm KD*P crystal in a Fluid Cell with AR windows cut to provide SHG for 694.3nm to 347.15nm. At 25 to 30% conversion a 1.5joule pulse should output 375 to 400mj of UV for the Hydrogen Raman laser. When converted to the Raman laser with at least similar efficiency then 90 to 100mj of 406nm should be produced. A LBO or BBO OPO Optical parametric oscillator is capable of achieving a more blue color of 450nm using the SHG of the Ruby laser but undesirable for holography due to the line width broadening of the OPO, unless additional steps are taken like etalons etc to control it.
Red-green pseudo color pulse holography.
The setup will use a Ruby and a Nd:YAG laser system where the two lasers are fired from a master console that times the firing of each to bring the q switch output of each laser as close as possible for the current design of the lasers. Since these lasers are passive q switched details will be provided of their timings and possible active q switches added later to reduce the timing window of the arrival of the output pulse from each laser.
Setup and color intensities.
Setup will be a split beam reflection setup. RG Setup design: color.gif This will minimize the cross talk and allow white light playback since the reflection volume hologram has a limited playback bandwidth for each of the primary color images of the hologram. Since two colors are used it would have had 4 primary and 4 conjugate images displayed if the bandwidth was large as in a thin transmission hologram and illuminated with the same two colors again. Additionally, since the number of images recorded are two then the shared dynamic range of the film will cause the diffraction efficiency to drop by 2 squared or each image will be 1/4 as bright.
Fujifilm silver halide holographic film F HL has about equal sensitivity to Ruby and SHG Nd:YAG laser output. So this panchromatic film should color balance with equal settings of the two laser's output energy. Since Blue is not used at this point, it is not anticipated that white can be seen but instead the object will appear yellow where equal object reflections are. Later when the Ruby system is modified to RB then the film's full panchromatic ability can be used. In fact it also appears that at 406nm also has about the same efficiency as the 532nm and 694nm so a RGB system should also have similar color balance. RGB Setup design: fullcolor.gif 100 to 200 uj/cm2 is the recommended exposure. This setup will target for a 100 uj/cm2 illumination energy density.
Use a Kodak #13 560-590nm safelight on Fujifilm F HL.
Emulsion shrinkage will be kept slight so that playback is shifted no more than 30nm and this would cause the 532nm to still look green at 502nm otherwise it would appear cyan if shifted more than this. This also would shift the 694nm to 664nm, which will appear brighter to the human eye. Yet on a RGB system the shift of 406nm any lower would cause the color to move into deeper violet. One method would be to keep exposure level somewhat low and use of re-halogenated/tanning bleach. Fujifilm recommended Ferric-EDTA. SM-6 will be used for the developer since it provides fast development of the low latent image to to HIRF.