This stuff rocks!! Getting very bright results now.
I owe a great debt of thanks to the members of this forum for all the great advice and wisdom.
Working Hard
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Larry
Working Hard
Great looking work Mark! You are using PFG-03C and JD-2. Does that JD-2 take 10 secs. to develop as with PFG-03M?
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Mark Cavin
Working Hard
Hi Larry,
I use JD-4. I spoke with Dr. Jeong about what was best to use for a developer. He has a very poisonous stringent regime designed to reduce the shrinkage and preserve color accuracy, but he suggested that JD-4 would be fine and would have a small bit of shrinkage. I have not noticed any and I develop for about 2 minutes after a 2 second exposure, still playing with the ratios(Never have made JD-4 work in 10 secs, even though it says you can). He also said that JD-2 would work, but that there would be a lot of shrinkage; I have some JD-2 but I have not tried it yet. Also it seems that 03C has greater sensitivities to batch variations than emulsions with only one dye sensitizer. The emulsion is very soft like 03M and I timed slow cool air dry as long as two and a half hours. Working with it in the dark is hard, but not that difficult, density can be checked against a very dim white light source. I have only fogged the corners of a couple of plates.
Thanks,
Mark
I use JD-4. I spoke with Dr. Jeong about what was best to use for a developer. He has a very poisonous stringent regime designed to reduce the shrinkage and preserve color accuracy, but he suggested that JD-4 would be fine and would have a small bit of shrinkage. I have not noticed any and I develop for about 2 minutes after a 2 second exposure, still playing with the ratios(Never have made JD-4 work in 10 secs, even though it says you can). He also said that JD-2 would work, but that there would be a lot of shrinkage; I have some JD-2 but I have not tried it yet. Also it seems that 03C has greater sensitivities to batch variations than emulsions with only one dye sensitizer. The emulsion is very soft like 03M and I timed slow cool air dry as long as two and a half hours. Working with it in the dark is hard, but not that difficult, density can be checked against a very dim white light source. I have only fogged the corners of a couple of plates.
Thanks,
Mark
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JohnFP
Working Hard
Sweet! Welcome to the addictive world of holography.
You must tell us what techniques and changes you made to get the good results. I am sure beginers of PFG would love to hear!!
Peace!
You must tell us what techniques and changes you made to get the good results. I am sure beginers of PFG would love to hear!!
Peace!
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Dinesh
Working Hard
"If you quit holography I am going to come to California personally and talk you back into it. My plan is to bring my wife and 3 kids and move into your house until you agree."
So let me get this right. If I quit holography, you're going to come visit? I'm almost tempted to state that I'm going to quit holography! We-e-e-ll, maybe not.
"...can you ellaborate on the the 3 orders in laymens term. It sound interesting."
Diffraction is a simple enough subject to describe, but difficult to calculate. There are very few exact solutions to most practical problems. Essentially, diffraction is nothing more than interference, except that if you have one slit, or a few slits it's called diffraction and if you have many slits it's called interference.
If light, or any wave, goes through a slit whose dimensions are small compared to the wavelength of light (small, but not smaller than) and falls onto a screen at a "large" distance away (several times the size of the slit) you can concieve of this in the following manner. When light hits the slit, the electrons at the boundaries of the slit are set into oscillation and thus are the source of new circular waves. These new waves then travel toward the screen as expanding circles originating at the edges, or boundaries, of the slit. Consider two posts immersed in water and seperated by the distance (approx) of a water wave. Consider also that these posts have spheres on them that can slide up and down the posts. When a wave hits the posts, the water drives these spheres up and down the posts as the wave ebbs and flows. These spheres in turn disturb the water and create fresh new waves. However, if the original wave hits these posts at an angle, the two spheres are "out of phase", ie the sphere that first "feels" the water wave starts to move, but the sphere in the other post hasn't begun to move yet. When it does move, it lags the other sphere by the time it takes for the water to hit the other post. Now both spheres on both posts generate fresh new wave, out of phase, that propagate through the water, but one wave lags the other. Therefore at any point on a wall in front of the posts, the disturbance is the result of the waves caused by the spheres. Depending on where you are on this wall, you'll see the net effect of the two waves together. When both waves are going up or down, the disturbance is at its highest, when the waves fromm the spheres are in opposition, the net disturbance is zero. Basically, an interference effect but from sources at the edge of the slit. It can be shown (I love that phrase!) that the net effect along the wall is a curve that's very high at the centre, drops to zero, rises to about 4% of the max value and drops to zero, rises to about less than 1% of the max value etc - this is called a "sinc function". The "center" is a line from midway between the two spheres to the wall. If you have two slits, you have four edges and the pattern now is a "sinc" curve, as explained, but with a fine structure of lines interposed within the curve - an interference of an interference, if you like. If you have lots of slits you get a series of lines which are very bright at the center, then these lines repeat on either side of the central bright lines but are a lot dimmer. These lines are the "orders". However, I've been describing the slits as if they are hard rectangular slits - like miniature windows or those slits thay have in old castles that they used to fire arrows out of. If the slits are not hard rectangular slits, but are bright at the center and fade at the edges and their brightness follows a sin wave pattern (these are the slits I'm talking about, not the pattern seen), as if someone placed a sinwave greyscale transparency across the slit face, then the pattern seen is a bright central line and only two side lobes. There are only two "orders" - the bright central lobe (the zero order) and the two side lobes (the +1 and -1 orders). This is because the other lobes, or orders are created by the extreme edges of the slit, but since the edges of the slit are a lot dimmer than the center of the slit, their effect is not so pronounced and the higher (+2, +3, -2, -3 etc) orders are pretty much killed off. They're still there, but so dim that they're not really seen.
In holography, the interference pattern caused by the reference and object is a sinwave profile, ie the interference lines do not have hard edges but fall off in a sinwave patter. Because of this, there are only three order: 0, +/-1, or the "straight-through" beam (zero order), the pseudoscopic (-1) and the orthoscopic (+1). This is essentially surface diffraction described by those two people whose names begin with R and N (I promised not to repeat their names!). Bragg diffraction is a little different but the same principle kind of holds. If you overexpose or overdevelop a transmission hologram, the fringes are no longer sinusoidal. In this case you use the fact that any non-siusoidal but repeating pattern can be expressed as a sum of sinusoidal functions (Fourier series). Each of these sinusoidal components, or harmonics) then generate their own set of orthoscopic and pseudoscopic images. You may have seen this in your resist holograms if you over-etch. When you see your image, keep turning the plate and a dimmer (although sometimes it can be brighter) secondary image appears.
So let me get this right. If I quit holography, you're going to come visit? I'm almost tempted to state that I'm going to quit holography! We-e-e-ll, maybe not.
"...can you ellaborate on the the 3 orders in laymens term. It sound interesting."
Diffraction is a simple enough subject to describe, but difficult to calculate. There are very few exact solutions to most practical problems. Essentially, diffraction is nothing more than interference, except that if you have one slit, or a few slits it's called diffraction and if you have many slits it's called interference.
If light, or any wave, goes through a slit whose dimensions are small compared to the wavelength of light (small, but not smaller than) and falls onto a screen at a "large" distance away (several times the size of the slit) you can concieve of this in the following manner. When light hits the slit, the electrons at the boundaries of the slit are set into oscillation and thus are the source of new circular waves. These new waves then travel toward the screen as expanding circles originating at the edges, or boundaries, of the slit. Consider two posts immersed in water and seperated by the distance (approx) of a water wave. Consider also that these posts have spheres on them that can slide up and down the posts. When a wave hits the posts, the water drives these spheres up and down the posts as the wave ebbs and flows. These spheres in turn disturb the water and create fresh new waves. However, if the original wave hits these posts at an angle, the two spheres are "out of phase", ie the sphere that first "feels" the water wave starts to move, but the sphere in the other post hasn't begun to move yet. When it does move, it lags the other sphere by the time it takes for the water to hit the other post. Now both spheres on both posts generate fresh new wave, out of phase, that propagate through the water, but one wave lags the other. Therefore at any point on a wall in front of the posts, the disturbance is the result of the waves caused by the spheres. Depending on where you are on this wall, you'll see the net effect of the two waves together. When both waves are going up or down, the disturbance is at its highest, when the waves fromm the spheres are in opposition, the net disturbance is zero. Basically, an interference effect but from sources at the edge of the slit. It can be shown (I love that phrase!) that the net effect along the wall is a curve that's very high at the centre, drops to zero, rises to about 4% of the max value and drops to zero, rises to about less than 1% of the max value etc - this is called a "sinc function". The "center" is a line from midway between the two spheres to the wall. If you have two slits, you have four edges and the pattern now is a "sinc" curve, as explained, but with a fine structure of lines interposed within the curve - an interference of an interference, if you like. If you have lots of slits you get a series of lines which are very bright at the center, then these lines repeat on either side of the central bright lines but are a lot dimmer. These lines are the "orders". However, I've been describing the slits as if they are hard rectangular slits - like miniature windows or those slits thay have in old castles that they used to fire arrows out of. If the slits are not hard rectangular slits, but are bright at the center and fade at the edges and their brightness follows a sin wave pattern (these are the slits I'm talking about, not the pattern seen), as if someone placed a sinwave greyscale transparency across the slit face, then the pattern seen is a bright central line and only two side lobes. There are only two "orders" - the bright central lobe (the zero order) and the two side lobes (the +1 and -1 orders). This is because the other lobes, or orders are created by the extreme edges of the slit, but since the edges of the slit are a lot dimmer than the center of the slit, their effect is not so pronounced and the higher (+2, +3, -2, -3 etc) orders are pretty much killed off. They're still there, but so dim that they're not really seen.
In holography, the interference pattern caused by the reference and object is a sinwave profile, ie the interference lines do not have hard edges but fall off in a sinwave patter. Because of this, there are only three order: 0, +/-1, or the "straight-through" beam (zero order), the pseudoscopic (-1) and the orthoscopic (+1). This is essentially surface diffraction described by those two people whose names begin with R and N (I promised not to repeat their names!). Bragg diffraction is a little different but the same principle kind of holds. If you overexpose or overdevelop a transmission hologram, the fringes are no longer sinusoidal. In this case you use the fact that any non-siusoidal but repeating pattern can be expressed as a sum of sinusoidal functions (Fourier series). Each of these sinusoidal components, or harmonics) then generate their own set of orthoscopic and pseudoscopic images. You may have seen this in your resist holograms if you over-etch. When you see your image, keep turning the plate and a dimmer (although sometimes it can be brighter) secondary image appears.
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Mark Cavin
Working Hard
I don’t know if you can see this http://65.29.139.115/Orders.html , in this example the Dark bands are the orders and where they curl back as loops are the side lobes you are talking about? Each lobe is a single order even if it is made of several dark lines? Or is each dark line an order? I get confused.
Mark
Mark
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Dinesh
Working Hard
Sorry, couldn't see it. All I got was a black screen.
I wish I could draw figures. John sems to be able to put up all these diagrams at the drop of a hat!
Anyway, let me try and make things a little clearer. I might have to go down to a fairly simple level in order to build up the picture.
When they say, "light is a wave motion" or "light is photons" these are huge oversimplifications. "Light" is a disturbance and distribution of energy whose causes are not fully understood. What actually happens is that there is a variation of an electric field that propagates forwards. Imagine a parallel plate capacitor connected to a battery. Between the plates, there is an electric field "pointing" from the plate connected to the positive terminal to the plate connected to the negative one. This is not the direction of the electrons, the direction of an electric field is the direction a free positive charge will travel if released into the field - from positive to negative. Any material ('dielectric') between the parallel plates will have their atomic structure distorted. That is, the center of the ring of electrons will shift away from the positive nucleus thus creating a charge seperation between center of negative charge and center of posititve charge. OK, now imagine there is a variable resistor, a pot, connected in series and vary the pot. The electric field between the parallel plates decreases or increases, depending on which way you take the pot. Now replace the (DC) battery with an AC source - say 10V peak-to-peak. Now the electric field will increase to a value of 10V, decrease down to zero volts, switch polarity as the AC source goes negative, increase negatively down to -10V, rise up to zero volts and finally up to 10V and then repeat. You now have an oscillatory electric field standing still, ie time variation in that any instance in time the voltage, ie value of the electric field, has a specific value but no space variation - the voltage just rises and falls in the same place.
Now move the plates in a direction parallel to the plates. You now have an oscillating electric field travelling forward, ie time and space variation. You can now ask two questions: What is the voltage 1 inch away from where the plates started moving? What is the voltage 10 seconds after it started moving. The answers are obviously connected by how fast the voltage is changing, ie the frequency of the AC source, and the speed at which the parallel plates are moving. So lets say the AC source is osclling at 60Hz, then when standing still, it reaches 10V in one quarter of 1/60th of a second, it then gets down to zero volts in half of 1/60th seconds, goes down to -10V in three quarters of 1/60th seconds and back to zero in 1/60th seconds. Now move it forward at 120 feet/second. It's speed is 120 ft/sec, its frequency is 60 cycles/second and in 1/60th of a second (one complete oscle), it's moved 2 feet so it's 'wavelength' is 2 feet. It should (hopefully!) be obvious that speed = frequency*wavelength. For HeNe light, speed is 300,000 m/sec, frequency is 474 thousand million cycles/sec (THz) and wavelength is 633 nm
If you now look at this travelling wave (forget about the plates - they've served their purpose!) it goes about with it's E-field going 'up' and 'down', realising that'up' and 'down' are not a physical 'up' and 'down' but voltage levels, as it goes forward. If now a second wave comes in from somewhere, it's voltage levels are also going 'up' and 'down'. So what happens in any local area of space, call it P, where one wave has a voltage at a particular value and another wave has a voltage of another value? What then is the actual voltage level at that point in space? Well, we have this remarkable thing called 'The Superposition Principle' which is a whell of a fancy way of saying they simply (algebraically) add! If one wave is at, say 5V and another is at, say -3 volts, the voltage at that point in space is 2V. Of course, if you look at a different point in space, the voltages of each wave will be different and so will their sum. Can you look at a particular point in space and say, "I know that wave A has a frequency of so-and-so and a wavelength of so-and-so and I also know wave B's characteristics (speed cannot change according to relativity). I now see 3 volts at this point so I can predict the voltage at any point?" Well, only if the characteristics maintain throughout space. if the characteristics abruptly change, you can only predict up to the point at which they don't change. This ability to abruptly change the characteristics is known as coherence and the distance over which the characteristics don't change is the coherence length. If two waves are coherent, then the sum of the two voltages at any point will remain the same at that point. In our case, the point P will always have a voltage of 3V (So long as your laser doesn't mode hop and abruptly change coherence!)
Ok, close now to interference, The physical affects of light on matter are caused by the voltage level. Let's say you had a material that was, say blue, and if, by applying a voltage it went red with the added condition that the greater the voltage the deeper the red and this material does not differentiate between + and -. Then, then by scattering this material all over a limited region of space and allowing two beams of light to hit it you'll see some places where the two voltages will add to 20V or -20Vand the material will be very, very red. In some places, you'll have a voltage due to beam A being 3.6V and that due to beam B being -5.3V and the resultant will be -1,7 - not so red. In some places beam A will be 10V and beam B -10V. Now the result is zero and the substance doesn't go red at all. In fact if this material were sprayed onto a plate and two collimated beams were to hit the plate, you'd see (as you went up the plate) a total voltage due to A and B alternatively going higher, as the individual voltages were both positive, then falling , then going to zero (that is, the sum of the two voltages) goes to zero - fringes!
I wish I could draw figures. John sems to be able to put up all these diagrams at the drop of a hat!
Anyway, let me try and make things a little clearer. I might have to go down to a fairly simple level in order to build up the picture.
When they say, "light is a wave motion" or "light is photons" these are huge oversimplifications. "Light" is a disturbance and distribution of energy whose causes are not fully understood. What actually happens is that there is a variation of an electric field that propagates forwards. Imagine a parallel plate capacitor connected to a battery. Between the plates, there is an electric field "pointing" from the plate connected to the positive terminal to the plate connected to the negative one. This is not the direction of the electrons, the direction of an electric field is the direction a free positive charge will travel if released into the field - from positive to negative. Any material ('dielectric') between the parallel plates will have their atomic structure distorted. That is, the center of the ring of electrons will shift away from the positive nucleus thus creating a charge seperation between center of negative charge and center of posititve charge. OK, now imagine there is a variable resistor, a pot, connected in series and vary the pot. The electric field between the parallel plates decreases or increases, depending on which way you take the pot. Now replace the (DC) battery with an AC source - say 10V peak-to-peak. Now the electric field will increase to a value of 10V, decrease down to zero volts, switch polarity as the AC source goes negative, increase negatively down to -10V, rise up to zero volts and finally up to 10V and then repeat. You now have an oscillatory electric field standing still, ie time variation in that any instance in time the voltage, ie value of the electric field, has a specific value but no space variation - the voltage just rises and falls in the same place.
Now move the plates in a direction parallel to the plates. You now have an oscillating electric field travelling forward, ie time and space variation. You can now ask two questions: What is the voltage 1 inch away from where the plates started moving? What is the voltage 10 seconds after it started moving. The answers are obviously connected by how fast the voltage is changing, ie the frequency of the AC source, and the speed at which the parallel plates are moving. So lets say the AC source is osclling at 60Hz, then when standing still, it reaches 10V in one quarter of 1/60th of a second, it then gets down to zero volts in half of 1/60th seconds, goes down to -10V in three quarters of 1/60th seconds and back to zero in 1/60th seconds. Now move it forward at 120 feet/second. It's speed is 120 ft/sec, its frequency is 60 cycles/second and in 1/60th of a second (one complete oscle), it's moved 2 feet so it's 'wavelength' is 2 feet. It should (hopefully!) be obvious that speed = frequency*wavelength. For HeNe light, speed is 300,000 m/sec, frequency is 474 thousand million cycles/sec (THz) and wavelength is 633 nm
If you now look at this travelling wave (forget about the plates - they've served their purpose!) it goes about with it's E-field going 'up' and 'down', realising that'up' and 'down' are not a physical 'up' and 'down' but voltage levels, as it goes forward. If now a second wave comes in from somewhere, it's voltage levels are also going 'up' and 'down'. So what happens in any local area of space, call it P, where one wave has a voltage at a particular value and another wave has a voltage of another value? What then is the actual voltage level at that point in space? Well, we have this remarkable thing called 'The Superposition Principle' which is a whell of a fancy way of saying they simply (algebraically) add! If one wave is at, say 5V and another is at, say -3 volts, the voltage at that point in space is 2V. Of course, if you look at a different point in space, the voltages of each wave will be different and so will their sum. Can you look at a particular point in space and say, "I know that wave A has a frequency of so-and-so and a wavelength of so-and-so and I also know wave B's characteristics (speed cannot change according to relativity). I now see 3 volts at this point so I can predict the voltage at any point?" Well, only if the characteristics maintain throughout space. if the characteristics abruptly change, you can only predict up to the point at which they don't change. This ability to abruptly change the characteristics is known as coherence and the distance over which the characteristics don't change is the coherence length. If two waves are coherent, then the sum of the two voltages at any point will remain the same at that point. In our case, the point P will always have a voltage of 3V (So long as your laser doesn't mode hop and abruptly change coherence!)
Ok, close now to interference, The physical affects of light on matter are caused by the voltage level. Let's say you had a material that was, say blue, and if, by applying a voltage it went red with the added condition that the greater the voltage the deeper the red and this material does not differentiate between + and -. Then, then by scattering this material all over a limited region of space and allowing two beams of light to hit it you'll see some places where the two voltages will add to 20V or -20Vand the material will be very, very red. In some places, you'll have a voltage due to beam A being 3.6V and that due to beam B being -5.3V and the resultant will be -1,7 - not so red. In some places beam A will be 10V and beam B -10V. Now the result is zero and the substance doesn't go red at all. In fact if this material were sprayed onto a plate and two collimated beams were to hit the plate, you'd see (as you went up the plate) a total voltage due to A and B alternatively going higher, as the individual voltages were both positive, then falling , then going to zero (that is, the sum of the two voltages) goes to zero - fringes!
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Mark Cavin
Working Hard
Excellent essay!! I think I understood almost all of it. Very nice about how you explain on coherency, coherently. Thank you with exponents.
“"As the island of our knowledge grows, so does the shore
of our ignorance.".” –John Wheeler
“"As the island of our knowledge grows, so does the shore
of our ignorance.".” –John Wheeler