heat resistant glass
You will be putting your pre-condensor lens within a few millimeters of the MH lamp, so it MUST be heat resistant glass. B270 glass is not! They will break. You need Pyrex or borosilicate.
Rolyn Optical has some in their paper catalog for $66 to $85. (Which I suspect Squeeky already found.) They don't appear on their website as a category, but you can type their part numbers into the search box to see specs & prices.
25.0100 114.3 mm D 165 mm fl $66.20
25.0105 114.3 mm D 190 mm fl $67.25
25.0110 114.3 mm D 229 mm fl $68.41
25.0120 114.3 mm D 305 mm fl $68.47
25.0140 152.4 mm D 305 mm fl $84.20
25.0150 152.4 mm D 406 mm fl $84.97
You will be putting your pre-condensor lens within a few millimeters of the MH lamp, so it MUST be heat resistant glass. B270 glass is not! They will break. You need Pyrex or borosilicate.
Rolyn Optical has some in their paper catalog for $66 to $85. (Which I suspect Squeeky already found.) They don't appear on their website as a category, but you can type their part numbers into the search box to see specs & prices.
25.0100 114.3 mm D 165 mm fl $66.20
25.0105 114.3 mm D 190 mm fl $67.25
25.0110 114.3 mm D 229 mm fl $68.41
25.0120 114.3 mm D 305 mm fl $68.47
25.0140 152.4 mm D 305 mm fl $84.20
25.0150 152.4 mm D 406 mm fl $84.97
Hi Guy,
I was aware I would need Pyrex, but had no idea how to tell if it was from the information they provided. Thanks for the heads up thou, I greatly appreciate all the help thus far. Do you think a 220mm fl condenser fresnel will work well with this LCD (392mm diag)? I noticed you have recommended a larger than 330mm field fresnel FL when using a 450mm projection triplet. What would you recommend?
Squeek,
I'd be happy to work together on our PJs, as I'll need all the help I can get 😉 . I've also been thinking of using the s400dd, I just can't find an electronic ballast for it anywhere. If you (or anyone else) has found a source please let me know.
I think that spherical reflector from Surplus Shed is damn near perfect for the s400dd bulb using a 220mm fresnel with no pre-condenser. See below. I will get a couple of those to play with
Good Find bro
(By the way all, of my sketches are 1px==1mm)
I was aware I would need Pyrex, but had no idea how to tell if it was from the information they provided. Thanks for the heads up thou, I greatly appreciate all the help thus far. Do you think a 220mm fl condenser fresnel will work well with this LCD (392mm diag)? I noticed you have recommended a larger than 330mm field fresnel FL when using a 450mm projection triplet. What would you recommend?
Squeek,
I'd be happy to work together on our PJs, as I'll need all the help I can get 😉 . I've also been thinking of using the s400dd, I just can't find an electronic ballast for it anywhere. If you (or anyone else) has found a source please let me know.
I think that spherical reflector from Surplus Shed is damn near perfect for the s400dd bulb using a 220mm fresnel with no pre-condenser. See below. I will get a couple of those to play with
Good Find bro(By the way all, of my sketches are 1px==1mm)
Attachments
here is the formulas you can use when calculate the light lost rate:
V = (4 Pi/3) r^3
V = (2 Pi/3) r^2 * h
V = (4 Pi/3) r^3
V = (2 Pi/3) r^2 * h
An externally hosted image should be here but it was not working when we last tested it.
Guy, B270 can handle upto 300c no probs, aslong as you cool the condenser there isnt a breakage issue.
Standard float glass will.
Trev🙂
Standard float glass will.
Trev🙂
heat resistant condensors
I don't think a MH lamp in close proximity will melt a standard glass condensor, but I think it could heat it unevenly enough to crack it. I have seen pictures of condensor lenses that cracked during normal use. None of those were Pyrex or borosilicate glass. I guess a design with the right amount of cooling air on both sides of the lens could prevent this. I just don't know how to determine that "right amount".
Those Ushio retrofit SS400DD lamps are only designed to run on an S51 HPS ballast. (That's High Pressure Sodium) They are designed to retrofit an HPS fixture with a nicer lamp. Running them on an electronic ballast has not always worked well, according to other posters on this and other forums. You can find one locally (shipping is expensive) or get one form places like www.goodmart.com.
I don't think a MH lamp in close proximity will melt a standard glass condensor, but I think it could heat it unevenly enough to crack it. I have seen pictures of condensor lenses that cracked during normal use. None of those were Pyrex or borosilicate glass. I guess a design with the right amount of cooling air on both sides of the lens could prevent this. I just don't know how to determine that "right amount".
Those Ushio retrofit SS400DD lamps are only designed to run on an S51 HPS ballast. (That's High Pressure Sodium) They are designed to retrofit an HPS fixture with a nicer lamp. Running them on an electronic ballast has not always worked well, according to other posters on this and other forums. You can find one locally (shipping is expensive) or get one form places like www.goodmart.com.
It wont melt it, it will crack it, its from the expansion rate being too great on the center of the lens. They dont heat evenly either, the hottest part is right in the center (about the size of the arc).
What happends is the center gets so hot it has to expand more then the outer. The outer is cooler and therfore boom, it gives.
I used to think that they heated evenly aswell, it wasnt until i got a temp probe out (that melted btw) and tested it. I also saw the heat difference on a particular lens on the plano side as the coating in the center changed colour to the outer. The coating in the center was burnt.
Trev🙂
fresnels
Inkoq:
I think a 220 mm fl condensor fresnel would work fine without a pre-condensor lens. If you do want to use a pre-condensor lens, then you might have to go to a 330 mm condensor fresnel. The question is if you can get the lamp arc close enough to the pre-condensor lens to light the corners of your fresnels. Difficult with a T15 lamp (15/8" diameter). A 330 mm fl fresnel gives you more room for the cone of light to expand.
Lumenlab has some longer fresnels that are suitable for a 450 mm fl projector lens. I use one of their 790 mm fresnels by adding some space between the fresnels and the LCD. Their new 650 mm fl fresnel would probably be better.
Inkoq:
I think a 220 mm fl condensor fresnel would work fine without a pre-condensor lens. If you do want to use a pre-condensor lens, then you might have to go to a 330 mm condensor fresnel. The question is if you can get the lamp arc close enough to the pre-condensor lens to light the corners of your fresnels. Difficult with a T15 lamp (15/8" diameter). A 330 mm fl fresnel gives you more room for the cone of light to expand.
Lumenlab has some longer fresnels that are suitable for a 450 mm fl projector lens. I use one of their 790 mm fresnels by adding some space between the fresnels and the LCD. Their new 650 mm fl fresnel would probably be better.
Well, I can't speak for Inkog, but the pro lens at LL are a little too much for me. I love Brain and LL but I can't afford fresnels that expensive, I was going to go with Alans 15.5" at diylabs. I want to thank everyone for helping on this, hopefully we will get a nice HDTV 15" projo.
I agree, they are pricey 
I just put a call into Fresnel Technologies, Inc. to get prices and availability. I was told a engineer would contact me sometime today. They have UVF Acrylic that blocks almost all UV and all middle and far IR. I'm guessing these won't be cheap, but hopefully they have some stock items we could source on the cheap. I'll let you know how this goes.
Like most, I do not have an unlimited supply of resources for this project. I researched and figured I was going to spend at least 700USD to make this HD pj come to reality with acceptable results. I figure if I'm going to invest that much $$ on this thing, if I find slightly more expensive parts that will provide greatly enhanced performance, I'll probably bite the bullet.
I just put a call into Fresnel Technologies, Inc. to get prices and availability. I was told a engineer would contact me sometime today. They have UVF Acrylic that blocks almost all UV and all middle and far IR. I'm guessing these won't be cheap, but hopefully they have some stock items we could source on the cheap. I'll let you know how this goes.
Like most, I do not have an unlimited supply of resources for this project. I researched and figured I was going to spend at least 700USD to make this HD pj come to reality with acceptable results. I figure if I'm going to invest that much $$ on this thing, if I find slightly more expensive parts that will provide greatly enhanced performance, I'll probably bite the bullet.
Did some thinking on reflectors and pre-condensers
Ok there is condenser that list 114mm dia and 165mm fl
If I understand optics correctly finding a matching spherical mirror would be ideal, just sandwhich the bulb between the two at equal distances.
It's not exact but close, surplusshed has a spherical mirror 76mm in dia w 152mm FL.
I have also found several other mirrors with close optics directly from optics stores.
Would these two items work together in harmony? Inkog SS also has hot mirrors but they are very small, 50mmx55mm.
I think it might be time to do some trial and error. Any chance you wanna come to Ohio Inkog 🙂
Ok there is condenser that list 114mm dia and 165mm fl
If I understand optics correctly finding a matching spherical mirror would be ideal, just sandwhich the bulb between the two at equal distances.
It's not exact but close, surplusshed has a spherical mirror 76mm in dia w 152mm FL.
I have also found several other mirrors with close optics directly from optics stores.
Would these two items work together in harmony? Inkog SS also has hot mirrors but they are very small, 50mmx55mm.
I think it might be time to do some trial and error. Any chance you wanna come to Ohio Inkog 🙂
spherical reflector shape
The reflector does not have to be the same diameter as the pre-condensor lens, because you can have it at a different distance from the lamp arc. It just has to have the same or slightly greater of an arc of intersection, when the lamp is placed at the center of curvature. That way, all parts of the pre-condensor lens "see" a reflection through the lamp arc.
In the drawing, I have a small reflector near the lamp and a larger reflector farther away. Their shape is the same.
BTW: Beware, reflectors are spec'ed by their focal length which is 1/2 of their radius. You will not try to use them as bad parabolic reflectors, so all you care about is their radius.
The reflector does not have to be the same diameter as the pre-condensor lens, because you can have it at a different distance from the lamp arc. It just has to have the same or slightly greater of an arc of intersection, when the lamp is placed at the center of curvature. That way, all parts of the pre-condensor lens "see" a reflection through the lamp arc.
In the drawing, I have a small reflector near the lamp and a larger reflector farther away. Their shape is the same.
BTW: Beware, reflectors are spec'ed by their focal length which is 1/2 of their radius. You will not try to use them as bad parabolic reflectors, so all you care about is their radius.
Attachments
Basicly my train of thought has been this...
As far as I can tell, fresnels are harder to find (and even harder to find cheaply) than lenses and mirrors. With this, I'm trying so find the best fresnels first then matching the light engine to them.
I'm about 99% I'm going with the 450 mm fl projector lens and Guy states a 650mm fl field fresnel is near what I would want. But I need more information...
I need a formula to figure out the optimal field fresnel fl for the 450mm projection triplet and my LCD.
If I understand correctly, the fresnel Fl decreases when the fresnel is cut to size. Anyone know how to calculate this?
As far as I can tell, fresnels are harder to find (and even harder to find cheaply) than lenses and mirrors. With this, I'm trying so find the best fresnels first then matching the light engine to them.
I'm about 99% I'm going with the 450 mm fl projector lens and Guy states a 650mm fl field fresnel is near what I would want. But I need more information...
I need a formula to figure out the optimal field fresnel fl for the 450mm projection triplet and my LCD.
If I understand correctly, the fresnel Fl decreases when the fresnel is cut to size. Anyone know how to calculate this?
Re: spherical reflector shape
Oh! Thanks for that tid bit, that helps alot. I was worng in my thinking
Guy Grotke said:
Oh! Thanks for that tid bit, that helps alot. I was worng in my thinking
The cut fresnel equation
>fresnel Fl decreases when the fresnel is cut to size. Anyone know how to calculate this?
Simple:
fl before cutting = fl after cutting * 1.00 😀
>fresnel Fl decreases when the fresnel is cut to size. Anyone know how to calculate this?
Simple:
fl before cutting = fl after cutting * 1.00 😀
Inkog,
Guy's post should be pretty obvious. Cutting the fresnel down in size doesn't change it's focul length. It's focul length is determined by the groove geometry and nothing else so long as it is laying flat as intended.
The only purpose of the field fresnel is to collapse and guide the light flux into a cone that will hopefully enter the aperture of the objective lens. The LCD will dissipate some of the light in other directions but much or most of the light will be guided in a way that will make the photons being imaged by the objective lens the most dense.
The field fresnel can be adjusted in it's distance behind the LCD so that a certain range of reasonable focul lengths will work. But as Guy has said for a 15 inch LCD a 650 FL fresnel is about ideal for the 450 triplet lens.
Furthermore, the distance of the LCD to the projection screen will change the lens to LCD distance. So what you need to do is set up your LCD at about the place were you think it will be placed and turn off all of the lights and hold up the lens until you get a focused image. Then measure the rear lens to LCD distance. From this you can estimate rather closely what the FL of the field fresnel needs to be.
Hezz
Guy's post should be pretty obvious. Cutting the fresnel down in size doesn't change it's focul length. It's focul length is determined by the groove geometry and nothing else so long as it is laying flat as intended.
The only purpose of the field fresnel is to collapse and guide the light flux into a cone that will hopefully enter the aperture of the objective lens. The LCD will dissipate some of the light in other directions but much or most of the light will be guided in a way that will make the photons being imaged by the objective lens the most dense.
The field fresnel can be adjusted in it's distance behind the LCD so that a certain range of reasonable focul lengths will work. But as Guy has said for a 15 inch LCD a 650 FL fresnel is about ideal for the 450 triplet lens.
Furthermore, the distance of the LCD to the projection screen will change the lens to LCD distance. So what you need to do is set up your LCD at about the place were you think it will be placed and turn off all of the lights and hold up the lens until you get a focused image. Then measure the rear lens to LCD distance. From this you can estimate rather closely what the FL of the field fresnel needs to be.
Hezz
Thanks Hezz & Guy,
I read in several places about fresnel focal lengths changing, but it was contrary to how I though they worked. I got it now for sure. Guy, I like your style, subtle but to-the-point 😉
I have the funds for my optics burning a hole in my pocket, I wish I could find the fresnels I need so I can get this show on the road.
Anyone have a good source for fresnels I can try??
I'm going to order my 450mm Triplet tomorrow from DIYLabs. Unless someone can tell me the Pro triplet from LL is worth the extra money. Anyone?
I read in several places about fresnel focal lengths changing, but it was contrary to how I though they worked. I got it now for sure. Guy, I like your style, subtle but to-the-point 😉
I have the funds for my optics burning a hole in my pocket, I wish I could find the fresnels I need so I can get this show on the road.
Anyone have a good source for fresnels I can try??
I'm going to order my 450mm Triplet tomorrow from DIYLabs.
Unless someone can tell me the Pro triplet from LL is worth the extra money. Anyone?I'm watching the Daytona 500 in HD on this Proview and it looks awsome! Talking about inspiration to get the projector finished...
Enjoy the race everyone! I'll be rooting for my Viagra team
Enjoy the race everyone! I'll be rooting for my Viagra team
Inkog you're tempting me to run down to the local Staples and buy this lcd, before they discontinue or raise the price that is.
I'd love to buy one just to compare it with my FP591 and 522A 🙂
I'd love to buy one just to compare it with my FP591 and 522A 🙂
- Status
- Not open for further replies.