My opinion -
John, you got it right - conjugation, whatever the original recording beam shape, is always best, on any plate that will be turned around.
A diverging beam in the master recording is simpler and cheaper, followed by it's converging replay illumination, for example.
If you have the optics, always conjugate. Fudging will still make holograms, but they will blur with off-axis viewing.
Playback with a different laser color requires a tilt and a slight shift of conjugate focus.
and for holographic image perfection - always listen to BobH.
Reference Beams used in H1 to H2 transfer
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John Sonley
Reference Beams used in H1 to H2 transfer
Thanks for your reply Jeffery - as soon as we have some nasty wet weather (that brings me out of my garden - which is a major pursuit of mine during the fair weather months) I'm going to test the principle by making 3 holograms of a pneumatic actuator, of which I made a good clear H1 master some years ago.
I'll set the image plane at the screws on it construction, the actuator rod will then be very 'real' in the H2 copies, about 3 inches.
The H1 master was made with a collimated reference beam and so I will reconstruct the image in making my H2 with a collimated beam but then the 3 holograms will be made using
(1) a diverging reference beam
(2) a collimated reference beam
(3) a converging reference beam
As I use a small quartz halogen 50 watt spotlight to view my holograms - a diverging beam, I would expect that (3) would give the least distorted image, if my theory is correct ............... but we'll have to wait and see!
You can view a photograph of the pneumatic actuator on my web site .... which now has a new URL as I've recently migrated to a new ISP. The address is: www.johnsonley.myzen.co.uk
Brgds
John
I'll set the image plane at the screws on it construction, the actuator rod will then be very 'real' in the H2 copies, about 3 inches.
The H1 master was made with a collimated reference beam and so I will reconstruct the image in making my H2 with a collimated beam but then the 3 holograms will be made using
(1) a diverging reference beam
(2) a collimated reference beam
(3) a converging reference beam
As I use a small quartz halogen 50 watt spotlight to view my holograms - a diverging beam, I would expect that (3) would give the least distorted image, if my theory is correct ............... but we'll have to wait and see!
You can view a photograph of the pneumatic actuator on my web site .... which now has a new URL as I've recently migrated to a new ISP. The address is: www.johnsonley.myzen.co.uk
Brgds
John
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John Sonley
Reference Beams used in H1 to H2 transfer
To All interested in this topic:
I have now completed the exercise I spoke of in my recent posting and this morning prepared two H2 copy holograms (from my original H1 master, made using a collimated reference beam) of my pneumatic actuator which I referred to in the past:
Hologram 1 was made using a collimated reconstruction beam and a converging reference beam
Hologram 2 was made using a collimated reconstruction beam and a diverging reference beam
Upon viewing both the H2 copies with a normal 50 watt quartz halogen spotlight (which of course, is a diverging light source), it is clear that there is significantly less distortion of the 'real' part of the image - the control rod - with hologram 1
Note that there is less of a difference between between the H2 made with a collimated reference beam and Hologram 1
This result is exactly as I predicted, namely that conjugate beams should be used - if you're getting 'picky'! When a converging reference beam is used to make an H2 copy, the film is then flipped for viewing and so a diverging white light source will result in the minimum amount of distortion of the 'real' components in the image
Film used : Hologram 1 was made on a 5" X 4" sheet of red sensitive Agfa film, kindly given to me by Dave Battin, Hologram 2 was made on a sheet of very old Agfa film I had saved from nearly 20 years ago.
They were both processed using ZIP1 and acid dichromate bleach following a 6 second exposure from a 33mW He Ne laser
It's interesting to note that my very old Agfa film was no 'slower' than Dave's probably more recent film
View my web site on: www.johnsonley.myzen.co.uk to see my holography set-up and in the Gallery you will find a picture of the pneumatic actuator that took part in this test
I will welcome the observations of my readers!
BRgds
John
I have now completed the exercise I spoke of in my recent posting and this morning prepared two H2 copy holograms (from my original H1 master, made using a collimated reference beam) of my pneumatic actuator which I referred to in the past:
Hologram 1 was made using a collimated reconstruction beam and a converging reference beam
Hologram 2 was made using a collimated reconstruction beam and a diverging reference beam
Upon viewing both the H2 copies with a normal 50 watt quartz halogen spotlight (which of course, is a diverging light source), it is clear that there is significantly less distortion of the 'real' part of the image - the control rod - with hologram 1
Note that there is less of a difference between between the H2 made with a collimated reference beam and Hologram 1
This result is exactly as I predicted, namely that conjugate beams should be used - if you're getting 'picky'! When a converging reference beam is used to make an H2 copy, the film is then flipped for viewing and so a diverging white light source will result in the minimum amount of distortion of the 'real' components in the image
Film used : Hologram 1 was made on a 5" X 4" sheet of red sensitive Agfa film, kindly given to me by Dave Battin, Hologram 2 was made on a sheet of very old Agfa film I had saved from nearly 20 years ago.
They were both processed using ZIP1 and acid dichromate bleach following a 6 second exposure from a 33mW He Ne laser
It's interesting to note that my very old Agfa film was no 'slower' than Dave's probably more recent film
View my web site on: www.johnsonley.myzen.co.uk to see my holography set-up and in the Gallery you will find a picture of the pneumatic actuator that took part in this test
I will welcome the observations of my readers!
BRgds
John
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BobH
Reference Beams used in H1 to H2 transfer
When you use a converging reference beam on the H2, you'll find that the hologram's much more sensitive to the distance between hologram and reconstruction source. The closer the source is to the hologram (matched with the reference beam used), the more critical it is to match the distances perfectly. If your source is going to be 50cm for example, the image will noticeably start to distort when moving the source only a few mm toward or away from the hologram. 
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John Sonley
Reference Beams used in H1 to H2 transfer
Yes Bob - I could see that and I tried to match the degree of convergence with the distance I use when assessing my H2s.
The exercise was not to try and establish new principles but to check a point that seemed correct in my way of thinking - having now confirmed what I thought was right I'll probably go back to using collimated beams for most H2s - unless I'm trying to prepare a really deep 'real' image
BRgds
John
The exercise was not to try and establish new principles but to check a point that seemed correct in my way of thinking - having now confirmed what I thought was right I'll probably go back to using collimated beams for most H2s - unless I'm trying to prepare a really deep 'real' image
BRgds
John