For the past 'lot of years' I've been producing nice bright H2 Image Plane Holograms using the Unterseher method of tilting the plateholders away from the H2 reference beam to obtain a reasonable reconstruction angle for the finished H2 image plane white light viewable holograms .
With some slightly dimmer H1s, in recent times, I've noticed that in tipping the H1, the correct reconstruction angle for maximum brightness of the pseudoscopic reconstruction changes to an extent that to achieve maximum brightness, the H1 reconstruction beam overlaps the the H2 plate with the usual 12 cm spacing I use when making the original H1
I've therefore lifted the H1 and H2 plateholders to be vertical. The H1 reconstruction image is bright and to get the H2 reference beam at an angle on the H2 plateholder, I've buried deep into my sandbox and positioned my main H2 reference beam mirror so that the reference beam, once spatially filtered and collimated, strikes the H2 plate at an angle of 23 degrees
My question is simple: Is this angle adequate to make a good bright H2 white light viewable hologram
H2 Reference Beam Angle for Image Plane Holograms
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Dinesh
H2 Reference Beam Angle for Image Plane Holograms
Not sure of the geometry. Any chance of a diagram? Are you bottom-referencing?
At any rate, assuming that you're making reflection H2's, 23 degrees is too small. The recon light will reflect back into the viewer's eyes causing a dazzle and making it difficult to see the image. If your H2's are achromat 23 degrees may well cause dispersion at small distances away from the image plane. There's also still a chance that the recon light will hit the viewer's face directly, especially if there's any shrinkage. If you're shooting a rainbow with a HeNe, you may want to keep your slits very narrow. This will limit the size of the image and cause the colours to be saturated.
By the way, I assume you're talking 23 to the plate normal, not the plate itself.
At any rate, assuming that you're making reflection H2's, 23 degrees is too small. The recon light will reflect back into the viewer's eyes causing a dazzle and making it difficult to see the image. If your H2's are achromat 23 degrees may well cause dispersion at small distances away from the image plane. There's also still a chance that the recon light will hit the viewer's face directly, especially if there's any shrinkage. If you're shooting a rainbow with a HeNe, you may want to keep your slits very narrow. This will limit the size of the image and cause the colours to be saturated.
By the way, I assume you're talking 23 to the plate normal, not the plate itself.
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John Sonley
H2 Reference Beam Angle for Image Plane Holograms
Dinesh - thanks for your reply.
I could take a photo of the set-up but not sure how to display it on this forum.
My reference beam from my HeNe is coming up from below, spatially filtered and collimated and strikes the H2 plate at 23 deg to plate normal - and I suspect that you're right - that the illuminating light will dazzle.
Perhaps I can move the reference mirror closer to the H2 - that will increase the angle the ref. beam strikes the plate.
What do you think would be the minimum angle I should aim for?
Best Regards
John
I could take a photo of the set-up but not sure how to display it on this forum.
My reference beam from my HeNe is coming up from below, spatially filtered and collimated and strikes the H2 plate at 23 deg to plate normal - and I suspect that you're right - that the illuminating light will dazzle.
Perhaps I can move the reference mirror closer to the H2 - that will increase the angle the ref. beam strikes the plate.
What do you think would be the minimum angle I should aim for?
Best Regards
John
H2 Reference Beam Angle for Image Plane Holograms
John
If you email me a photo i'll upload it for you
Jem
If you email me a photo i'll upload it for you
Jem
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holorefugee
H2 Reference Beam Angle for Image Plane Holograms
If you look in the place where you type a reply there are two tabs right beneath the text box. One is "options" the other is "Upload Attachment". Write your post and click upload attachment. Hit browse and find the photo on your hard drive. If you make the picture smaller, like 70K it will be easier for Ahmet to maintain the forum. If you put a description in the file comment box, Google will search it and Ahmet will get better search engine placement.
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Dinesh
H2 Reference Beam Angle for Image Plane Holograms
Assuming you're talking about reflection, we use 55. Somewhere around 45 will just miss the plate but I like to give a little leeway so viewers do not get dazzled as they rock the plate to and fro. For transmission, we go down to 45.John Sonley wrote:What do you think would be the minimum angle I should aim for?
For rainbows, I shoot with 488 and calculate what angles I'll get assuming a viewer is looking at it around 60. That is, if I want the viewer to see red, say, at normal to the plate, I calculate the fringe frequency to diffract red in the normal direction and then shoot with 488 to get that frequency. Roughly, if you shoot with 457, a 25 degree reference shows the red slit at plate normal for about 45 degree viewing angle.
For achromats one factor is how much of the diffraction is Bragg. The more Bragg, the less dispersion. For standard, commercial silver halide (~8 micron thick emulsion) a reference angle of about 35 upwards pretty much is almost pure Bragg and so, for an achromat, I can get reasonable deep images shooting at 45.
H2 Reference Beam Angle for Image Plane Holograms
John's Setup
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holorefugee
H2 Reference Beam Angle for Image Plane Holograms
This is off topic but I had good luck with pipe after filling it with sand and making epoxy plugs for the ends. Much better dampning even in 80" long cross supports.
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Dinesh
H2 Reference Beam Angle for Image Plane Holograms
Thanks for the pic. I see what you mean now.
I do believe that the angle is too shallow. After talking with Joy, I now learn that she designs the angle with the end result in mind. Is it intended to be displayed on a desk with a standard photoframe? Is it intended for a wall? etc etc.( You can tell she designs the geometries. as far as I'm concerned, an obtuse angle is an angle that's just being bloody minded and difficult!). At any rate, the H2 ref is usually anything from 50 - 55, depending on the application. As I mentioned, I think you may be able to get away with 45, but if the viewer rocks the hologram, it'll dazzle. With your present table, that'd mean taking the spatial filter assembly closer to the plate. Can you tilt both the H1 and the H2? This means, however, tilting the original object also. In other words, everything is parallel, but tilted to the vertical, by about 30 degrees to get the 50 odd degrees you may want. I can see that this may be difficult.
However, (her thoughts) the H1 to H2 distance is too small. At 12cm, assuming the plate is also about 12cm wide, the H2 ref has to come in at minimum 45deg in order for the H1 recon beam to clear the H2 plate. With this in mind, if your plate is a different size, choose angles and distances accordingly.
She also suggests a sideways table, which gives you a lot more flexibility with angles at the expense of placing your object sideways. Placing an object sideways does also have the advantage of being able to light it better since all the lighting mirrors are on the same level. The main light and the fill light usually come in from different directions and with a vertical setup the mirrors have to be set in a sort of vertical half circle around the object. My thinking is that if you do want a vertical geometry, you might try and put posts on the corners of the table and place a mirror on top. This will also allow steeper angles.
I do believe that the angle is too shallow. After talking with Joy, I now learn that she designs the angle with the end result in mind. Is it intended to be displayed on a desk with a standard photoframe? Is it intended for a wall? etc etc.( You can tell she designs the geometries. as far as I'm concerned, an obtuse angle is an angle that's just being bloody minded and difficult!). At any rate, the H2 ref is usually anything from 50 - 55, depending on the application. As I mentioned, I think you may be able to get away with 45, but if the viewer rocks the hologram, it'll dazzle. With your present table, that'd mean taking the spatial filter assembly closer to the plate. Can you tilt both the H1 and the H2? This means, however, tilting the original object also. In other words, everything is parallel, but tilted to the vertical, by about 30 degrees to get the 50 odd degrees you may want. I can see that this may be difficult.
However, (her thoughts) the H1 to H2 distance is too small. At 12cm, assuming the plate is also about 12cm wide, the H2 ref has to come in at minimum 45deg in order for the H1 recon beam to clear the H2 plate. With this in mind, if your plate is a different size, choose angles and distances accordingly.
She also suggests a sideways table, which gives you a lot more flexibility with angles at the expense of placing your object sideways. Placing an object sideways does also have the advantage of being able to light it better since all the lighting mirrors are on the same level. The main light and the fill light usually come in from different directions and with a vertical setup the mirrors have to be set in a sort of vertical half circle around the object. My thinking is that if you do want a vertical geometry, you might try and put posts on the corners of the table and place a mirror on top. This will also allow steeper angles.
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John Sonley
H2 Reference Beam Angle for Image Plane Holograms
Dinesh and Joy - that's very helpful and I will try to attach another photo which shows the H1 and H2 plateholders, when I've made it small enough for this site( H1 nearest camera - then H2 - then collimating lens - SF - finally ref beam steering mirror)
In the past, using the Unterseher method alone of tilting both the H1 and H2 plateholders away from the reference beam to achieve is difficult when they are at about 40 deg as the pseudoscopic H1 image gets dim the more you tilt the plateholders and you have to readjust the H1 reconstruction beam from the 60 deg to plate normal that it was created with to <50 deg plate normal to get maximum brightness of the pseudo image - and at that angle the reconstruction beam hits the H2 copy plate holder badly.
I design my H1s with a minimum distance between the object and the H1 plate (actually it's film temporarily laminated on to glass) of 12 cms and a side reference beam angle of 60 Deg to plate normal. With those dimensions when using an H1 master sized 5" X 8" and an H2 sized 5" X 4", the H1 reconstruction beam just misses the smaller H2 plate
But I will try two ideas:
1. Making my H1s with the objects horizontal - I'll need to work out which way to turn them or I'll have upside down holograms!
2. Moving the H2 Ref beam steering mirror closer to the H2 plateholder to increase my 23 deg to plate holder normal H2 impact angle to say 30 or 35 deg and then tilt the two plate holders say 15 to 20 deg to make a total of 45 - 55 deg
What do you think of that as a plan?
Best Regards
John
In the past, using the Unterseher method alone of tilting both the H1 and H2 plateholders away from the reference beam to achieve is difficult when they are at about 40 deg as the pseudoscopic H1 image gets dim the more you tilt the plateholders and you have to readjust the H1 reconstruction beam from the 60 deg to plate normal that it was created with to <50 deg plate normal to get maximum brightness of the pseudo image - and at that angle the reconstruction beam hits the H2 copy plate holder badly.
I design my H1s with a minimum distance between the object and the H1 plate (actually it's film temporarily laminated on to glass) of 12 cms and a side reference beam angle of 60 Deg to plate normal. With those dimensions when using an H1 master sized 5" X 8" and an H2 sized 5" X 4", the H1 reconstruction beam just misses the smaller H2 plate
But I will try two ideas:
1. Making my H1s with the objects horizontal - I'll need to work out which way to turn them or I'll have upside down holograms!
2. Moving the H2 Ref beam steering mirror closer to the H2 plateholder to increase my 23 deg to plate holder normal H2 impact angle to say 30 or 35 deg and then tilt the two plate holders say 15 to 20 deg to make a total of 45 - 55 deg
What do you think of that as a plan?
Best Regards
John