Re–reading over the many pages of this thread, I found a few questions that did not seem to get answered or were not followed up.
Having built two successful lenses, I thought I might try to answer a few of them.
Q – Can this lens be used as a Horizontal Expansion lens or is it just a Vertical Compression lens?
A – the original design was for a VC lens, but I had success building a HE lens than a VC lens as I wanted a larger image at a given throw. I can however reconfigure the prisms to form a VC lens.
Q – What size do the prisms need to be?
A – Large enough not to clip the image or light beam. The “paper test” was what I used to determine how large the prisms needed to be for my projector.
Q – What shape (from the end) do they need to be?
A – I built mine based on a rectangle of 1.78:1 given that is the shape of the light beam. However many commercial units and many of those that had success here built their prisms based on a square.
Q – What are the prisms filled with?
A – A clear, non flammable liquid. I have used water and even flat soft drink…The original thread starters used water in one prisms and oil in the second.
Q – Do different liquids correct chromatic abrasion?
A – It appears that different liquids correct different refractive indexes, but it is the second prism that corrects the CA. Water is said to exhibit a “blue hue” and using water in both prisms might actually produce slightly blue tinted images. I own two LCD projectors and they both seem to have a “red push” when their contrast is increased, and with my set-up, any “blue hue” from the water is cancelled out by the “red push”.
Q – Can this lens project be used for 2.35:1?
A – Yes, if you have a 16:9 projector. Regardless if the lens is a HE or VC, the amount of stretch is still around 33% and therefore only converts video displays to the next level – IE a 4 x 3(12:9) becomes 16:9 and a 16:9 can become a 21:9. attempting to stretch the image past 33% creates massive amounts of CA with HE lenses…
BTW CA is a by product of HE lenses, where it is not as problematic with VC lenses.
Q – What are the angles of the prisms?
A – It appears that a variety of angles less than 45 degree can work. Both my lenses are based on 30/60/90 triangle. It appears the angles between the prisms that dictate the exact amount of stretch. The angles in my 4 prism lens are just 15 degrees from the apex and work better than the conventional 2 prism lens of 30 degrees.
Q – Can multiple prisms be added together to form a 4 prism lens?
A – Yes, see above answer.
Q – Is glass better than Pespex?
A – I can’t really answer that as I never built glass prisms, but the Perspex works well. I used 6mm (1/4”) which did not suffer the flexing issues some had with thinner material.
Q – What is the correct way to align the prisms?
A – I found that by placing the 90 degree angle of both my prisms in to face each other worked better than when they faced out. Not only was I able to get better amounts of stretch, but I got less light reflection as well. The interesting thing is, I have already stated that the second prism corrects the CA. But this does not happen if both prisms face the same way…
Q – How do I set up my projector/player to work with this lens?
A – The video source is set to WIDE and the Video Display is set to a 4 x 3 mode, not the widescreen mode. Normally we electrically stretch the image in the display, but when using an anamorphic lens, we optically stretch the image. Setting the source to WIDE provides us with an image comprised of the most pixels. The display can therefore use this extra information, but the image will be tall and thin. A HE lens will restore the geometry by stretching the image and a VC lens with restore the geometry by compressing the image…
I’ll add to this as I think of more valid points…
Mark
Having built two successful lenses, I thought I might try to answer a few of them.
Q – Can this lens be used as a Horizontal Expansion lens or is it just a Vertical Compression lens?
A – the original design was for a VC lens, but I had success building a HE lens than a VC lens as I wanted a larger image at a given throw. I can however reconfigure the prisms to form a VC lens.
Q – What size do the prisms need to be?
A – Large enough not to clip the image or light beam. The “paper test” was what I used to determine how large the prisms needed to be for my projector.
Q – What shape (from the end) do they need to be?
A – I built mine based on a rectangle of 1.78:1 given that is the shape of the light beam. However many commercial units and many of those that had success here built their prisms based on a square.
Q – What are the prisms filled with?
A – A clear, non flammable liquid. I have used water and even flat soft drink…The original thread starters used water in one prisms and oil in the second.
Q – Do different liquids correct chromatic abrasion?
A – It appears that different liquids correct different refractive indexes, but it is the second prism that corrects the CA. Water is said to exhibit a “blue hue” and using water in both prisms might actually produce slightly blue tinted images. I own two LCD projectors and they both seem to have a “red push” when their contrast is increased, and with my set-up, any “blue hue” from the water is cancelled out by the “red push”.
Q – Can this lens project be used for 2.35:1?
A – Yes, if you have a 16:9 projector. Regardless if the lens is a HE or VC, the amount of stretch is still around 33% and therefore only converts video displays to the next level – IE a 4 x 3(12:9) becomes 16:9 and a 16:9 can become a 21:9. attempting to stretch the image past 33% creates massive amounts of CA with HE lenses…
BTW CA is a by product of HE lenses, where it is not as problematic with VC lenses.
Q – What are the angles of the prisms?
A – It appears that a variety of angles less than 45 degree can work. Both my lenses are based on 30/60/90 triangle. It appears the angles between the prisms that dictate the exact amount of stretch. The angles in my 4 prism lens are just 15 degrees from the apex and work better than the conventional 2 prism lens of 30 degrees.
Q – Can multiple prisms be added together to form a 4 prism lens?
A – Yes, see above answer.
Q – Is glass better than Pespex?
A – I can’t really answer that as I never built glass prisms, but the Perspex works well. I used 6mm (1/4”) which did not suffer the flexing issues some had with thinner material.
Q – What is the correct way to align the prisms?
A – I found that by placing the 90 degree angle of both my prisms in to face each other worked better than when they faced out. Not only was I able to get better amounts of stretch, but I got less light reflection as well. The interesting thing is, I have already stated that the second prism corrects the CA. But this does not happen if both prisms face the same way…
Q – How do I set up my projector/player to work with this lens?
A – The video source is set to WIDE and the Video Display is set to a 4 x 3 mode, not the widescreen mode. Normally we electrically stretch the image in the display, but when using an anamorphic lens, we optically stretch the image. Setting the source to WIDE provides us with an image comprised of the most pixels. The display can therefore use this extra information, but the image will be tall and thin. A HE lens will restore the geometry by stretching the image and a VC lens with restore the geometry by compressing the image…
I’ll add to this as I think of more valid points…
Mark
Attachments
widescreen projector with anamorphic lens?
When you set your dvd player or source should be set to wide does this mean the image outputted to your projector is the full dvd rez 720x480?
What happens if you set it to normal? Does it output say 720x 306 for 2.35 movies?
Also in my case I am building a 16:9 diy projector with a 7 inch widescreen lcd. How do i maximize the resolution with anamorphic lens?
When you set your dvd player or source should be set to wide does this mean the image outputted to your projector is the full dvd rez 720x480?
What happens if you set it to normal? Does it output say 720x 306 for 2.35 movies?
Also in my case I am building a 16:9 diy projector with a 7 inch widescreen lcd. How do i maximize the resolution with anamorphic lens?
The DVD format is by defualt a 4 x 3 format. The rez is based around 720 x 540 (where PAL is 720 x 576 and NTSC is 720 x 480). The anamorphic enhancement allows storage of additional width through the horizontal squeeze mode to allow wider images to fit in the given space at the same vertical rez.
When set to wide then played back on a 4 x 3 device, the widescreen image will be "tall and thin" (actualy horizontally squeezed). It will use the full vertical rez of the display.
The anamorphic lens will optically stretch that image out to create a 16:9 image.
When you watch a 2.35:1 film, you notice that their are small black bars present on the 4 x 3 display. Additional squeezing of the image and an even greater optic stretch would be required to eliminate the black bars, but on a 16:9 display, there is a zoom mode that removes the black bars. This mode is different to the 16:9 mode as once again the image is tall and thin, but because the panel is wider than the 4 x 3, you do not lose any width. The lens then stretches this out, and you end up with an image like I poseted earlier...
So you player MUST be set to 16:9 for this to work...
Mark
When set to wide then played back on a 4 x 3 device, the widescreen image will be "tall and thin" (actualy horizontally squeezed). It will use the full vertical rez of the display.
The anamorphic lens will optically stretch that image out to create a 16:9 image.
When you watch a 2.35:1 film, you notice that their are small black bars present on the 4 x 3 display. Additional squeezing of the image and an even greater optic stretch would be required to eliminate the black bars, but on a 16:9 display, there is a zoom mode that removes the black bars. This mode is different to the 16:9 mode as once again the image is tall and thin, but because the panel is wider than the 4 x 3, you do not lose any width. The lens then stretches this out, and you end up with an image like I poseted earlier...
So you player MUST be set to 16:9 for this to work...
Mark
ok so on my 16:9 display if i set a 2:35 movie to wide on the dvd and the display to 4:3 sounds like i will get a 4:3 image with borders on the left and right. so i will use something like 600x480 pixels instead of 800x480.
if the movie is 16:9 i can set the same square 4:3 image will appear in the middle of my widescreen display again not using the entire 800 horizontal rez. I will be using 600x480 rez of the display once again. the only difference seems to be less streching or compression. But seems to me anamorphic lens has no use for widescreen displays.
if the movie is 16:9 i can set the same square 4:3 image will appear in the middle of my widescreen display again not using the entire 800 horizontal rez. I will be using 600x480 rez of the display once again. the only difference seems to be less streching or compression. But seems to me anamorphic lens has no use for widescreen displays.
ok edit doesn work so will just do this.
Sorry you said 720x480 dvd default so thats actually 1.5 ratio or almost my entire widescreen display in terms of res.
So I can set the dvd to widescreen and my display 4:3 ? So I should get the full height image with borders on the left and right correct?
The anamorphic lens will compress or stretch that resolution to my 2:35 proper image.
If I did not use the anamorphic lens a 2:35 image will show 800 x 340 =272k pixels vs 345k pixels with the anamorphic lens. not huge enough difference to warrant the anamorphic in my opinion
Anamorphic lens with 1:85 movies would be pointless with my display correct?
Sorry you said 720x480 dvd default so thats actually 1.5 ratio or almost my entire widescreen display in terms of res.
So I can set the dvd to widescreen and my display 4:3 ? So I should get the full height image with borders on the left and right correct?
The anamorphic lens will compress or stretch that resolution to my 2:35 proper image.
If I did not use the anamorphic lens a 2:35 image will show 800 x 340 =272k pixels vs 345k pixels with the anamorphic lens. not huge enough difference to warrant the anamorphic in my opinion
Anamorphic lens with 1:85 movies would be pointless with my display correct?
finally some more interest in 2.35:1
Not really, DVD is based on 720 x 540 which is 1.33:1. NTSC is a lower than 540 meaning the number of scan lines is less, but the aspect ratio does not change, it is still 1.33:1. PAL on the other hand has more scan lines than the numer 540, but it too remains at 1.33:1 in its native form. This is one key reason PAL is considered better than NTSC...
Try that with a 1.78:1 film and you will be correct. With a 2.35:1 you need to find the mode that allows you to see the image horizontally squeezed (like you've discribed) but also so that the image is from side to side of the 1.78:1 display. This mode should also cut off the black bars top and bottom...
Take another look at my image. If the lens were not in action, the image would still be top to bottom, but would be horizontally squeezed and would be 1.78:1. The lens simply provides the optical stretch to restore the geometry and as a result, the sapect ratio becomes 2.35:1...
I will try and image capture what I am talking about, but hopefully you on the right path...
So tell me more about your DIY projector and what how you will build (or have you already built) your anamorphic lens...
Mark
Not really, DVD is based on 720 x 540 which is 1.33:1. NTSC is a lower than 540 meaning the number of scan lines is less, but the aspect ratio does not change, it is still 1.33:1. PAL on the other hand has more scan lines than the numer 540, but it too remains at 1.33:1 in its native form. This is one key reason PAL is considered better than NTSC...
Try that with a 1.78:1 film and you will be correct. With a 2.35:1 you need to find the mode that allows you to see the image horizontally squeezed (like you've discribed) but also so that the image is from side to side of the 1.78:1 display. This mode should also cut off the black bars top and bottom...
Take another look at my image. If the lens were not in action, the image would still be top to bottom, but would be horizontally squeezed and would be 1.78:1. The lens simply provides the optical stretch to restore the geometry and as a result, the sapect ratio becomes 2.35:1...
I will try and image capture what I am talking about, but hopefully you on the right path...
So tell me more about your DIY projector and what how you will build (or have you already built) your anamorphic lens...
Mark
Projector Set Up 1
As I can only attach one image at a time, I will have to make several posts. The purpose of these shots is simply to show the set up, not image quality...
I have used the same still from "Terminator 2 Judgement Day" for all of the images. The geometry and size will vary from photo to photo to demonstrate the set up proceedure when using a 16:9 projector and an anamorphic lens.
The first image from "T2" and is the full 2.35:1 image. This image is made possible by setting the DVD player to 16:9 (wide mode) and the projector is set to "zoom" where by it fills the entire panel with image. Because the source is anamorphically enhanced, the black bars that are normally seen at the top and the bottom are missing, allowing the projector to reproduce the image using every pixel on the panel. The image's geometry is optically corrected by the anamorphic lens...
Mark
As I can only attach one image at a time, I will have to make several posts. The purpose of these shots is simply to show the set up, not image quality...
I have used the same still from "Terminator 2 Judgement Day" for all of the images. The geometry and size will vary from photo to photo to demonstrate the set up proceedure when using a 16:9 projector and an anamorphic lens.
The first image from "T2" and is the full 2.35:1 image. This image is made possible by setting the DVD player to 16:9 (wide mode) and the projector is set to "zoom" where by it fills the entire panel with image. Because the source is anamorphically enhanced, the black bars that are normally seen at the top and the bottom are missing, allowing the projector to reproduce the image using every pixel on the panel. The image's geometry is optically corrected by the anamorphic lens...
Mark
Attachments
Projector Set Up 2
This next shot (same frame) is what the image looks like without the anamorphic lens optically stretching the image (this is my lens in pass-through mode). The image is horizontally squeezed. This is because the player is running in 16:9 mode, the disc is 16:9 enhanced, and the display is running a 4 x 3 mode.
Notice that the image still runs from the top of the screen to the bottom with no black bars (they have been removed by the projector) running in "zoom". The shape of the image now is actually 16:9 and the projector is able to use every panel for maximum image brightness...
This next shot (same frame) is what the image looks like without the anamorphic lens optically stretching the image (this is my lens in pass-through mode). The image is horizontally squeezed. This is because the player is running in 16:9 mode, the disc is 16:9 enhanced, and the display is running a 4 x 3 mode.
Notice that the image still runs from the top of the screen to the bottom with no black bars (they have been removed by the projector) running in "zoom". The shape of the image now is actually 16:9 and the projector is able to use every panel for maximum image brightness...
Attachments
Projector Set Up 3
Normally we use a 16:9 projector (16:9 mode) to electrically stretch the horizontally squeezed image to restore the geometry. When using an anamorphic lens, this is the last thing we want to do, as the projector will electrically stretch the image and so will the lens. The result is a short fat image much the same as when 4 x 3 material is played in this mode. It is incorrect and the image shows why...
Notice that the black bars are back too - NOT GOOD...
Mark
Normally we use a 16:9 projector (16:9 mode) to electrically stretch the horizontally squeezed image to restore the geometry. When using an anamorphic lens, this is the last thing we want to do, as the projector will electrically stretch the image and so will the lens. The result is a short fat image much the same as when 4 x 3 material is played in this mode. It is incorrect and the image shows why...
Notice that the black bars are back too - NOT GOOD...
Mark
Attachments
When you set the dvd player in wide mode i assume its still outputting 720x480 ntsc rez only in 16:9 ratio? Since 720x480 is less ratio then 16:9 I assume there is the electronic stretch you are referring to.
Now when you set the 16:9 projector to zoom does this place the image at the full height of the display? Without the zoom there would still be black bars on the top and bottom viewing a 2:35 movie with my 16:9 projector. Correct?
So sounds like there is actually an advantage using 16:9 projector over 4:3 displays for movies.
If I am watching a 1:78 movie there seems to be no use for the anamorphic lens.
If I am watching a 2:35 movie I set dvd player to 16:9, projector to zoom and anamorphic lens stretching the 1:78 squeezed image further to 2:35.
So I am only streching 33% to get a 2:35 image where all others using 4:3 displays have to stretch much more.
384,000 pixels for a 2:35 image. Not bad. Those with 4:3 and no anamorphic lens would have 272,340 pixels on a 2:35 image.
I have not build nor the projector nor the lens. Once I build the projector i will post results here. If the bugdet is reasonable i will build the anamorphic lens for those 2:35 movies.
QUOTE]When you set the dvd player in wide mode i assume its still outputting 720x480 ntsc rez only in 16:9 ratio? Since 720x480 is less ratio then 16:9 I assume there is the electronic stretch you are referring to.
Now when you set the 16:9 projector to zoom does this place the image at the full height of the display? Without the zoom there would still be black bars on the top and bottom viewing a 2:35 movie with my 16:9 projector. Correct?[/QUOTE]
Correct. The disc is anamorphically enhanced, so the player can out put the disc with the max rez of the format. Photo 2 (of the 3) shows the image tall and thin but top to bottom of the display…
From the disc’s perspective we have just clipped off the top and bottom, but from the projector’s perspective (and ours too as we watch the projected image not data off the disc) we have gained more pixels by using the full panel…
It depends. Yes this one way to look at it as 1.78:1 fills the panel anyway, but as soon as you watch something wider you are going to want a lens to CIH. I actually use the 4 x 3 mode and then stretch that with the lens for 16:9. But I also built a pass through mode for the times that I want to watch the entire panel without over stretching the image…
My point exactly…
Cool, I don’t frequent the DIY projector threads, but has there been any further development to the “reflective” design over the normal “transmissive” design for those using a 7” LCD panel as the source?
Mark
Now when you set the 16:9 projector to zoom does this place the image at the full height of the display? Without the zoom there would still be black bars on the top and bottom viewing a 2:35 movie with my 16:9 projector. Correct?[/QUOTE]
Correct. The disc is anamorphically enhanced, so the player can out put the disc with the max rez of the format. Photo 2 (of the 3) shows the image tall and thin but top to bottom of the display…
From the disc’s perspective we have just clipped off the top and bottom, but from the projector’s perspective (and ours too as we watch the projected image not data off the disc) we have gained more pixels by using the full panel…
It depends. Yes this one way to look at it as 1.78:1 fills the panel anyway, but as soon as you watch something wider you are going to want a lens to CIH. I actually use the 4 x 3 mode and then stretch that with the lens for 16:9. But I also built a pass through mode for the times that I want to watch the entire panel without over stretching the image…
My point exactly…
Cool, I don’t frequent the DIY projector threads, but has there been any further development to the “reflective” design over the normal “transmissive” design for those using a 7” LCD panel as the source?
Mark
You lost me. So the dvd player outputs the full 720x480 in what mode? And all other modes are less rez output from dvd player?
What mode on the dvd player gives you a 4:3 output and 720x480 to a 4:3 display?
4:3 mode for a 4:3 display right. Because if you go 4:3 mode with a 16:9 display you loose pixels from your display on the sides.
As I stated a few posts back, the DVD format is based on 720 x 540 (you'll have to try and forget NTSC's 480 for just a moment). Therefore the AR is 1.33:1. Through the anamorphic enhancement, additional width can be horizontally squeezed into that 1.33:1 frame giving the DVD rez of 960 x 540 (16:9).
The easiest thing is to simply connect a DVD player (set to 16:9) to a 4 x 3 TV. For a 1.78:1 film or TV program, you will see the full screen being being used, but the image is tall and thin.
If you play a 2.35:1 film, the image is still tall and thin but you also see a some black bars top and bottom. On a widescreen set, you can select a zoom mode that removes the black bars. The image now fills the entire screen but is still tall and thin. On the widescreen set you also have the option to electrically stretch the image, but in CIH projection we want to optically stretch the image not electrically stretch the image...
However some data is lost. The DVD format is 720 x 540 (or 960 x 540 in 16:9), but 540 is the number of vertical pixels. If we choose to remove the black bars, we by default loose some vertical rez on the disc about 33%. The display however gives it the edge by now using it's full vertical rez for the image, and does not waste pixels reproducing black bars...
As I said, we watch projected images, not the data off the disc, so if it gets more light on the screen, it is way better than projecting black bars... In fact it is some 22% better (brighter) than the same letterboxed image...
Mark
The easiest thing is to simply connect a DVD player (set to 16:9) to a 4 x 3 TV. For a 1.78:1 film or TV program, you will see the full screen being being used, but the image is tall and thin.
If you play a 2.35:1 film, the image is still tall and thin but you also see a some black bars top and bottom. On a widescreen set, you can select a zoom mode that removes the black bars. The image now fills the entire screen but is still tall and thin. On the widescreen set you also have the option to electrically stretch the image, but in CIH projection we want to optically stretch the image not electrically stretch the image...
However some data is lost. The DVD format is 720 x 540 (or 960 x 540 in 16:9), but 540 is the number of vertical pixels. If we choose to remove the black bars, we by default loose some vertical rez on the disc about 33%. The display however gives it the edge by now using it's full vertical rez for the image, and does not waste pixels reproducing black bars...
As I said, we watch projected images, not the data off the disc, so if it gets more light on the screen, it is way better than projecting black bars... In fact it is some 22% better (brighter) than the same letterboxed image...
Mark
I have mounted my prisms on a plate so that the rear prism is fixed and the front prism swings to allow both a stretch mode as well as the much needed pass through mode.
I took measurements of the angles as well and it appears that two 30/60/90 right angle based triangle (in plan) prisms need 40 degrees separation to give the desired 33%...
Mark
I took measurements of the angles as well and it appears that two 30/60/90 right angle based triangle (in plan) prisms need 40 degrees separation to give the desired 33%...
Mark
I see someone at avsforum used anti-reflex glass and glicerine to get results as good as a panamorph. Has anyone used these materials?
Lots of successful DIY lens have been made with those materials. The results however have been varing from really good (I'm yet to see a screen shot) to not so good due to the fact that some gylcerine re-acts to bright light...
And for the cost, I'm too sure that I want to chance it, that's why I have stuck with water, costs nothing and if need be, can be changed out with no prolems...
Mark
And for the cost, I'm too sure that I want to chance it, that's why I have stuck with water, costs nothing and if need be, can be changed out with no prolems...
Mark
Vertical Compression Mode
Mark,
First let me say that you have done some very nice work here.
I have an XGA projector and I would like to be able to use the full resolution for 16:9 HDTV and DVD sources. Currently, having the projector set at it's widest output for my throw gives a picture of the width that I want. I think this means I want a vertical compression anamorphic lens setup. Would your lens setup work as such if it were rotated 90 degrees? Also, have you run across any internet sources of tutorials on the optics of prisms in regard to anamorphic projection?
Thanks for any advice you can provide,
Michael
Mark,
First let me say that you have done some very nice work here.
I have an XGA projector and I would like to be able to use the full resolution for 16:9 HDTV and DVD sources. Currently, having the projector set at it's widest output for my throw gives a picture of the width that I want. I think this means I want a vertical compression anamorphic lens setup. Would your lens setup work as such if it were rotated 90 degrees? Also, have you run across any internet sources of tutorials on the optics of prisms in regard to anamorphic projection?
Thanks for any advice you can provide,
Michael
Only if the stretch exceeds the desired 33%. All of the screen shots I have posted are real including the Jango Fett image which is comprised of 2 digital photo layered to allow you to see both the screen and the speakers. If my lens produced light reflections, they too would be seen in the digital screen image captures.
My lens has a pass through mode, and when restretching the image, I simply work off the light on the screen for the width. If you move the prisms too far, you will see the light reflections form in the centre of the image.
I used to have a lot past 25% stretch, then through experintation, I learned that the best results came from reversing the prisms so that their 90degree angle now faced in. From reading the results of a few others that got light reflections, I would say they too have set their prisms as I initially had them. Reversing doesn't seem like such a big deal, but it works way better. Some down tilt (projector is ceilling mounted) seems to be required as well...
Thank you Michaell for the positive feedback. It sounds like a VC lens would suit yuor set up. I can turn my lens on its side and reverse it to become a VC as well. I have not conducted any light tests in this mode yet as I intended only to build HE lenses, but I have recieved a few emails about making VC lenses and am looking into the construction of a VC lens. The prisms I have right now a too big (too tall) to be used in a VC, but a shorter version would work well. I still want to keep the pass through mode as well with the VC as it appears Prismasonic have discontinued theirs.
So far a infomation goes, there seem to be a number of sites including a few that are pay per use for the infomation, but nothing has been as useful as the (now 44) pages of this thread, as most of what I have read is technical (I don't full grasp it) and aimed more at complex cylindrical lenses, not the simplier prismatic lens...
Mark
VC size
Mark,
Thanks for the info. Could you suggest a size for the VC application? Also, what is the exact material you are using for your lens? I think I have seen you refer to it as Perspex and Lexan.
I found this kind of cool java app that shows the transmittance and reflectance of a prism of variable angle and Ri. Watching where the reflections exit the prism is particularly interesting.
Prism app
Thanks,
Michael
Mark,
Thanks for the info. Could you suggest a size for the VC application? Also, what is the exact material you are using for your lens? I think I have seen you refer to it as Perspex and Lexan.
I found this kind of cool java app that shows the transmittance and reflectance of a prism of variable angle and Ri. Watching where the reflections exit the prism is particularly interesting.
Prism app
Thanks,
Michael