Hopefully after a year of collecting, reading and waiting things are close enough to be able to open a PLOG.

Rearden's Projector:

(Current) General design:
17"
LL Pro lens
Single folded (LL FS mirror)
Daewoo L17711MN (8ms, 700:1, 720p, DVI/VGA, 1280x1024, $212+ship/tax)
remove AG
SD400 lamp
magnetic ballast (donation from ballast mfg)
norpro (or the new cold reflector)
1 PPAC paddlewheel fan

(Current) Implementation:
17"
LL Pro lens
Single folded (LL FS mirror)
Daewoo L17711MN (8ms, 700:1, 720p, DVI/VGA, 1280x1024, $212+ship/tax)
Mother's Mag method AG polish
SD400 lamp
magnetic ballast (donation from ballast mfg)
new cold pro reflector
2 PPAC paddlewheel fan

I am not quite sure on the type of wood and shape. It needs to match a maple/light pine wood pattern and color. So veneering is not out of the question. Pun15isher's cabinet design looks good but for a 17.

I will use the threadedrod design and will borrow any ideas shamelessly from whereever I come across them. All advice welcomed.

I am holding off until the pro lens ships (I have already waited over a year).

The project steps currently looks like this:
1. Find out frame dimensions
2. order LCD, and test
3. design air path
4. Make frames
5. buy lexan x2, high temp black paint
6. put threaded rod design together
7. order FS mirror, cold mirror reflector with pro
8. make mirror frame and install on rods.
9. make sure I have all the parts for the lamp ballast, mogul
10. make lamp holder and adjuster
11. add reflector
12. design focus mechanism
13. design box, wiring, connection and switch locations
14. build box
15. build focus mechanism
16. strip LCD
17. strip AG
18. paint inside of box
19. install innards
20. initial testing
20.1 tinker ad infinium
21. finish outside of box
22. design screen
23. build screen
24. test DVD player settings, ffdshow settings, color balance.
25. obtain HTPC
26. enjoy

While impatiently waiting for the pro lens, I am trying to estimate my future screen needs. I am planning a "17 pro lens single folded design. My viewing location is constrained and SWMBO provides significant additional constraints. I have 8ft ceilings. The fireplace will be behind the screen location, so it has to be quickly moveable and storable, and not against a wall. It (or it's hangers) also have to be quite unobtrusive when not in use.

I have approximately 12.75 feet from the front edge of the couch to the front edge of the hearth. Placing the projector behind the couch is not really an option. So it will be about a max of 11.5 ft throw to the screen. Using the focal calculator (if I did it right) this should give me a picture 63.25x84.27 with a diag of 105. I could probably adjust a few things around to get it to 110 or 120 with a little creativity.
Given that my viewing location will be around 14-14,5ft from the screen and about 4ft from the floor. (wall behind couch to screen is ~15.75 ft.)

1. How big is too big?

I want to milk all I can get from the projector, but I am also one who likes the next to last row in an IMAX and doesn't like to sit more that 2/3 of the way back from the front in a normal theater.

I don't know how much I can keystone horizontally, but it is possible to place the projector next too the couch that would give me about 14.5 screen to proj distance a 82.5x110 and a 137.5 diag. This would place my head at approximately the same distance from the screen as the projector with nearly a 9x7 foot picture (in 4:3) that would seem to be a lot to take in from 14 ft away.

But at 16:9 the image is closer to 9x5.

2. So in short what is the generally accepted optimum screen distance to screen dimention ratio?

My current thinking is to tack a 2x2 to the bottom of the screen material for weight. The top would be a 2x2 or a fir 1x3 with some extra material glued on to make an L shape for stiffness. The top support would stick out a few inches on each side with two eyelets on each side to connect into small hooks in the ceiling. To adjust the height of the screen I could spin the top support to take up excess material in about 3" increments. When finished I could roll the screen around the top support for storage.

rearden

I came across these yesterday:
Four corner frame clamp, $10
http://www.harborfreight.com/cpi/ctaf/Disp...temnumber=34233
34233-2VGA

and for those into the Light Fusion/MMud:
HVLP kit, $60
93305-1VGA
http://www.harborfreight.com/cpi/ctaf/Disp...temnumber=93305

I am working on the folded design. Since the fresnels are 650mm, does that mean that the distance between the back of the second fresnel to the center of the triplet should be 650mm? or should it be slightly shorter?

rearden

The distance that is most important is the triplet to LCD, so you want about that FL. The focal point of the frensel is 650mm but you really want to "fill" the lens with light so if you think of a picture of the light triange from the fresnel we want the point of the triangle to be past the rear lens of the triplet.

OK so should the 650 be within the focusing mechanisms focal range? e.g. focusing mechanism run between 620 and 660 (LCD to center or triplet)?

Why is the distance measured between the LCD and the triplet and not the second fresnel and the triplet?

rearden

Howdy:

Your setup is similar to what mine will ultimately be. I wish you all the best.

I "think" of it like this:

The fresnels expand and compress a cone of light (which started as a point of light - the arc in the lamps we use). The triplet projects the image (image = LCD) which must be in focus for a given set of conditions. So, you want the LCD at a certain "focal point" and not the fresnels.

In other words, you want to "focus" the triplet on the plane (in the geometric sense) in space which is occupied by the LCD.

You may have read about how some folks get concentric rings projected onto their screens. This is because the fresnels are at that critical focal plane where the LCD should be for their setup.

(All that said someone will almost surely come along and slap me down for the way I've worded this. But hey, I've got one more post on my way to being a "guru"! )

have you gotten your LCD? mine doesn't letterbox 720p

*edit scratch that, it doesn't even natively support 720p. arghhhh

**well after learning powerstrip i've managed to get it to accept 720p.. not letterboxed though. contrast seems pretty good.. maybe a little better than my ag neovo (500:1)

jrobot,
I have not. It is susposed to arrive today, but by looking at ups is doesn't seem it will.

Have you contacted ti51384? he said that he was able to get it into 720p.

What is powerstrip?


Durachko,

Thanks for your explaination. It makes more sense now and I will get back to drawing pictures and figuring out light paths!

rearden

The standard I have seen quoted for optimal viewing distance to screen width ratio is 1.75:1. Apparently some theaters are designed with the center seat at this distance from the screen. There is some difference of opinion about aspect ratio having an effect on the decision though.

With a 9' wide screen, 14.5' back is 1.61:1. If you generally prefer to sit closer than the middle of the theater, your dimensions sound perfect.

I find myself wanting a different distance to the screen depending on how much the picture is moving. Action movies (especially with dark fight scenes) are impossible to follow at less than 2:1, but I'm typing right now with the monitor at closer to 1.5:1. Because I'll be using the PJ mostly for movies and gaming, I'm planning on 2:1 at the couch, but using a throw that leaves room behind the pj just in case I want a bigger picture.

Here's a good article:
http://www.projectorcentral.com/screen_size.htm

i sent ti51384 an email.. he seems inactive.. power strip is a program that lets you tweak your display timings & resolutions

IronGecko,
Thanks for the info on screen size/distance ratio, that was exactly what I was looking for. So I need something between 2 and 1.5 but closer to 2.

jrobot,
my monitor did come in. Right now I have it hooked up to a laptop and it looks good in 1280x1024. How do I attempt to get things in to 720p. I don't plan on running off of anything other than a pc.

rearden

720p is a resolution 1280x720.. i think you will need to download powerstrip to set that (google)

Progress so far:

I have made 4 frames from 3/4 angle molding. 2 for the fresnels, 1 LCD and 1 for the refletor.
The reflector will sit inside a cheap cookie sheet with a hole cut into it and lay in the frame.
The frame is partialy cut out to provide room for the ballast and move it further away from the lamp.
I have a potted magnetic ballast which is pretty big (and heavy).
I built the frame to an inside (visible hole) dimension of 13.5 and 10.75 and glued an extra strip of
molding to the long side of the frame.
The $5 precut (11x14) lexan at homedepot will fit inside with some room to spare.

I tried to wait to strip the LCD until last, but I needed the exact dimentions, so I have it 90% stipped. I will
leave the back light on until the end and I can safely drop it into it's frame. It
took me about 1.5 hours following ti51384's excellent guide. It was pretty straight forward. They moved a few of the
screws around and it would be helpful to include a few pics of places to pry and snap.

Has anyone sucessfully tried removing the AG on this monitor? What has worked in the past if I were to go
the polish route?

I have cut the top FS mirror supports and back out of MDF. I am using threaded rod clamped to MDF pivoting
on "T" shaped supports attached to the threaded rods. The pinching action of the threaded rod to the
supports will provide some structure to the upper portion.
The lamp is supported by a threaded rod, connected to "L" brackets and some long screws into the mogul.
Some washers and nuts will provide stability. I need to dig my camera up.

I should be able to start cutting the basic outside and fitting the skeleton together later this week.
I am planning a 5-8 deg tilt to the triplet.

blackout cloth, a second PCAC and hopefuly a temp monitor are on their way.
I need to buy the veneer.

I hope the triplet, reflector and FS mirror arrive soon!

rearden

sounds good! any tips for making the frames? i think i'm going to go with angle molding also.

Instead of building last night, I got sidetracked and found some Mothers Mag Polish at Ace for about $6.
After reading about a horrible AG removal experience with the L1711MN I decided to try the safe route and polish.

I started out using the dremel and a small felt disk with the switch at about 40%. Since the torque is so low on the dremel I had to put it that high to maintain much wheel speed. I went over it a few times and cleaned it. My dremel patterns were quite clear afterwards. I have a pic, but I need to dig up my usb cable, so pics are on the way.

before
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after dremel, hmm, it looks like I need to try to take it again because the reflection didn't come out. You can see a few of the dremel lines at the bottom.
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After that I decided to stick with elbow grease. I spent the next hour polishing out the dremel pattern.
I would cover the screen with the polish and then use various patterns until the polish basic was wiped off. I then would clean it with 70% alcohol to see the result. I used cotton and kleenex and usually didn't start to see much black on the applicator until the end.

I think it is more reflective than before, but it is definately not a mirror finish. I may try a few more passes and see if it improves. I have spent about 1.5 hours so far polishing it. I can read all the words off the reflection, but they are still a bit fuzzy. The over head lamp clearly shows both light bulbs and the fixture, but the light bulbs are still small blobs.

What should be the position of the LCD in a vertical single folded design?
My current thinking is:
With a straight box design I think it should be upside down with the user face toward the lamp.
With a vertical folded deisgn: right side up with the user face toward the lamp. Right side up meaning the top of the LCD would be toward the rear of the projector and the user face would be pointing down.
Please correct me if I am wrong.

rearden

Well I ordered the frame making gizmo from harbour freight, but I got tired to waiting for it (ok, 2 days:) and made them myself. I stripped the LCD so I could get the exact measurements. I cut the angle moulding to the inside of the inner edge (LCD visible). Placed four flat sided and heavy objects ( 7AH SLA batteries) on a sheet of newspaper, placed my cut pieces in place and adjusted things until the diagonals matched up. I let them sit overnight and then clamped two extra pieces to the outside on the long side of the frame and let them stand until evening. I then drilled the holes for the rods through these pieces. I then put sanding sealer on them to prep them for the black paint which I plan to do all at once.

So nothing special, just a good chop saw and some patience. So far things look good, but I have not assembled things yet to test them. So YMMV as my design has not passed through QC yet.

My next major challenge is to calc the light cone from the second fresnel so I can place the triplet and mirror in the right place and cut my box to the correct dimensions.

rearden

In a folded design (projector with a mirror) the LCD front (side you normally look at, AG side) faces the triplet and the LCD top (usually part with the FFC's and circuit board) faces the back of the projector.

So if you were to look into your projector through the triplet you would see the LCD as you would if it was still a monitor, not flipped or upside down.

Thanks, that is the info I am looking for! I wanted to make sure I would get my controller board all in position and then have it on the wrong side.

rearden

I want to use this same Daewoo monitor. Can you give me the actual measurements for the LCD. Thanks

Here is one dimension pic
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I found it easier to build them looking at the internal (display) dimension. I build that to 10.75 x 13.5 inches.

Click to view attachment

I got the skeleton put together last night. It took about 2 hours of spinning nuts.
Click to view attachment
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AND the optics arrived today!
now to figure out a focusing mechanism...

My current idea for a focusing mech is to make a piece of MDF, maybe a double thickness to go around the triplet. I have a 3/8 dowel which will then be countersunk and glued into the wall of the box. The triplet will ride on these dowels (2 or 3). With suitable amounts of wax it should not bind. I then plan to use a captive nut either manual or electric to move it back and forth.

I am still unclear about the position of the triplet and mirror, so I hope to place a lamp in the right place and observe the size and location of the image where the triplet should be. I may cut the front panel long so I can adjust the location and still have the triplet in place before the final cut.

I plan to use small dabs of RTV lock the position of the reflector in the cookie sheet as well as the lexan and fresnels. That was the only stuff I could think which may be able to handle the temps 35mm from the arc.

I must have missed some discussion about fresnels and triplets. The guide focuses on the standard triplet and that masks some details.
The standard kit has fresnel with a focal length of 317 and a triplet of 320 with a difference of 3mm.
The pro has a fresnel of 650 and triplet of 500. This difference is 150mm.

The fresnel creates a light cone (well pymamid) 650mm long. The triplet will focus things which are 500mm away which is where the LCD should be. 500mm away the light cone should have a diagonal size of about 100.8mm hmm, which is suspiciously like the size of the lens....

So I need to place the triplet at the triplet's focal length away from the LCD, not the fresnel's. The focusing mechanism needs to be able to move 20mm on each side of that 500mm triplet focal length.

rearden

Last night's progress:
I cut the cookie sheet which I have designated as the reflector holder. I put an X with wire on the frame shone a light to get an approximate shadow center and marked the cookie sheet. I punched a hole and set the reflector in the hole, shadowed once again the get the approximate size of the reflector on the sheet, came in 5mm and started cutting with some tin snips. I hammered the rim down so it was slightly bowed down, coated the rim with red RTV and set the reflector in with a few extra daubs of RTV to hold it in place. It says "High Temp Silicone" we shall see if it really is. The heat and UV should take it's toll, but it really only needs to lay in the hole. The reflector is FS so there seems to be little danger of scraping the surface off.

I held the black cookie sheet up to a 500w halogen lamp to quickly dry the paint and it got quite hot amazingly quickly.

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Last night I took the dremel to the fresnels. It only took 3 cutting wheels.
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The fresnels and lexan are in place. I left some of the lexan protection on, to help reduce the chance of scratches.
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Here is the image of the light bulb at the approximate location of the triplet.
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I am now at a position where I need to decide the location of the triplet and then the mirror. I did not have a transparency to put in the location of the LCD for testing, but I did make a crosshair out of wire. I was not able to get the crosshairs to come into focus (or even see them) by moving the triplet around, which I thought was a bit odd.

I currently have the grooves of both fresnels on the side of the LCD, which I think is correct.

Does anyone have any recommendations on the best way to remove fresnel dust from a fresnel? I have used a shop vac, but there still is some left and in the grooves.

Is there an In and Out side for the triplet?

I am also having a little trouble getting the fresnels to lay flat.

rearden

My first thought is distilled water in a squirt bottle. Haven't tried it though. Good luck.

Here you go : http://www.lumenlab.com/forums/index.php?s...findpost&p=5918

You wrote:



On the ProLens, the flange for the triplet is on the inside of the projector (direct response from senor Brainchild). I too have noticed that the ProLens fresnels are larger (and maybe thinner) and tend to flex. My understanding is that this can't be good for uniform light treatment. I'm contemplating using acrylic or lexan "under" each fresnel to inhibit flexing. Hate to add more in the light path, but I feel it's essential to keep the fresnel lens rigid. Thoughts?

Here is my first cut focusing mechanism. It is constructed of 3/8 oak dowel and a 1/4 threaded rod. I use a t-nut and plan to add a thin nut with some locktight and a wing nut once I get things stabilized.


Inside view. Pencil is there to glue and epoxy and dry.
Click to view attachment

It is interesting to see how much light is reflected from the outside of the ring even though it has Ultra Flat Black Camo paint on it. I have used almost 3 cans of paint so far, even with putting sanding sealer of first.

inside view
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outside view
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I don't know how well it will work. It wants to bind. I put 1500 grit sandpaper on the dowel and got it quite smooth then put graphite on both surfaces. The dowel is slick but the MDF is hairy. I will try wax next. The threaded rod area may require a sleeve. The t-nut was pulling out so I dolloped some epoxy on it to convince it to stay. I may have to revert to some variant of pun15er's capitive nut if it still doesn't stay.

bev077 thanks for the infor on the pro lens orientation information.

rearden

Here are some shots as more things come into place.

I think I counted no less than 10 holes need to be placed into the enclosure for all the various items and their location is dependant upon the final placement of things like the LCD. Unfortuately, the FFC thingys are on the top of the LCD and therefore back of the projector. I don't have much space for them there, but I will find a way to put it in without damaging it.

I still need to cut the holes for the fans (2x), temp monitor, monitor controls and switches (2x).

Has anyone used the old backlight for any purpose? It just be quite bright and it seems the backlight PS is seperate. It would make an interesting lamp for the garage.

Click to view attachment

I think I should have cut the mirror down. I am not going to receive much size reduction benefit unless I cut it down. I still don't understand the light cone thing entirely. Conceptually it makes sense, but when I start measureing the size of the light cone in various areas, it isn't the size I think it should be. So I decided to leave the mirror large. I used Contact Cement to bond it to 1/2 mdf, some left over pieces of cookie sheet, a threaded rod and some daubs of RTV to secure it. The screw was for a counter weight, but it was not necessary. I think I would use some version of a hinged design next time.

Click to view attachment

I still don't get the light cone size and the focal length of the various lenses. The triplet is 500mm and the fresnel is 650. There for the fresnel should come to a point at 650mm, the triplet should want to focus on things which are 500mm away. My rough measurements have about 40cm from LCD to mirror center and 18cm from mirror center to triplet. This adds up to 580mm, not 500 (or even 650). I had the mirror about 4" (~100mm) lower, I move it up with the intent of moving the triplet more into the projector. By holding things by hand I didnt' seem to get 4" of backward placement to the triplet.

I am wary of actually putting the box together because then I lose most of my adjustability. but I am just going to have to take the plunge. I cut the front panel about 1 too long so I would have some final adjustability.

When I place the panel at it's proposed location, I do not get a sharply defined light spot and the lighted area is larger than the triplet even though the brighest area is inside the triplet. I am just using a 100w lamp and so my arc is definately not a point source, so that could be part of the problem.

rearden

I wired up the lamp the other night and burned it for about 30 min. I have a lot of wire clean up to do and to wire the 12v lines. I was going to use the 12v monitor supply to run the fans and the temp monitor. I ahve not wired up the LCD yet.
The image was not as bright as I want it to be. I don't think it would be bright enough right now with the LCD in place. I need to make sure my lamp is at the correct position. I have fresnel rings in the image, even though the LCD to collector fresnel distance is 4cm.

I have not found the sweet spot yet for the triplet, I always seem to have at least one dark corner and the "best" spot seems to be off center. I may need to put the box together to keep the frame square.

and one very heart stopping moment when the triplet fell out of the front panel thankfully on to my lap where I caught it rather than the garage floor.

I have pictures but I need to download them.

rearden

I spent two long afternoons working on the projector and have made some progress and found some challenges. First off here is one of my first images.
This is with the 100w lamp
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This is with a sheet and the HID lamp. It is late afternoon and the sun is the bright spot in the middle.
Boy do I wish it was this bright through the LCD!
Click to view attachment

I am starting to match all the pieces together.

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This is the current state of "togetherness". I have the bottom, top and sides attached. I used L type brackets, one per side and then predrilled several 6x2" screws per side. without predrilling, the 1/2 MDF was splitting, even with #6 screws. All the cutouts, have been made. I need to patch an extra fan hole (somehow I cut them on the wrong side.
I picked up a 7805 at RS today. I think my temp monitor wants both 12v and 5v, hopefully not also -5v. It wants a drive hook up.
The front is not screwed on and my cooling involves a sizeable fan.
The bottom hole in the side is the temp monitor and the top is the screen control. I will put two PCAC fans in the front.
Click to view attachment

I ws holding off placing the LCD into place until the last to try to minimize the possibility of damage. It was then I realized that I was going to have some issues. The LCD fit the frame fine but the end controls are in the way of the upper fresnel frame. I also put the threaded rods a little inside the corners, so I wouldn't be cutting holes in weak corners. The electronics are the length of the LCD so I can't put them outside the frame. I had to bring the jigsaw back out and cut some of the frame lip off. I may still need to cut the fresnel down a bit because it is not laying flat. It may not be an issue, if it is in the correct keystone direction.
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Unfortunately, the jigsaw wiggles things quite a bit and rattled enough that the nuts moved around on the rods. So I will need to go back and remeasure everything. I think this may be some of my other dark problems.

The only way I think I could have avoided this, would be to have placed the rods in a different location. But the afterthought mods are destructive.

Here are two pics of the image. They are 1024x768 instead of 1280x1024 because the video card on the current laptop couldn't handle it.

I think I need to tweak quite a bit. I find the image quite dark. or at least darker than I want. The back of the projector was open but all other lights were off. I also was projecting onto a cream sheet, so there were several things working against it, but even so I think fundamentally something must be off.
I may have to break down and do teh AG removal, not just polishing. I am a bit scared because the only other AG removal I have heard about on my LCD also took the polarizer off

I could clean the lexan and fresnels even more, but a few dust bits shouldn't cause that darkness.

I need to recheck my measurements. I have the ushido SD400 (old) lamp. the lamp itself it sitting upon the pro reflector. As nearly as I can tell, that should put the focus somewhere inside the arc tube. I have having a bit of trouble keeping the lamp in position because the reflector seems to be ressessed too much and the lamp supports have a hard time going that low. The bottom of the arc tube should be at the 220mm mark. at 1cm the light cone should be almost 1cm. I guess I could reduce that distance another 10mm so the light cone at the top of the arc tube should be around 20mm.

it seems like the purpose of the upper lexan is to get the fresnel to lay flat, not to support it. So I may work on getting the fresnel to lay flat and then remove the 2nd lexan from the system. But that shouldn't recover too much.

The focus is off, but that should be just a few more hours of tweaking.

Anyone have any other tips on tweaking and getting more light to a dark screen?
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Here is an oddity I saw on my ceiling. I know I have some light leaks, but this was a pretty good image of what looked like the the GE symbol.

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I went to Hobby Lobby today and they didn't have any velvet ribbon, but they did have some black velcro on clearance for $1.30/yd. They also didn't have any BO cloth. Those places are just plain different. Time moves at a different pace and so does the clientel and then the fast moving young male comes waltzing in asking for odd things like velvet ribbon, black out cloth and self adhesive felt tabs. They were nice, but they definately do not consider my demographic as their target audience or even really know what to do with me. There is a lot of cool stuff in there, but evidently I use it for purposes other than what they think it is intended and they have a hard time getting out of that box. Anyway...

So the next steps are to:
put in the lamp switch,
wire up +5v to the temp monitor
put the fans in place
recheck (again x5) the relative placement of all the parts.
try to figure out the dark image problem.
put final bits on the focusing mechanism
Button things up.
put on veneer
beg for high SAF (Spouse Approval Factor) ratings.
Start on screen.

I am using the SD400 (old) lamp and a potted magnetic ballast. If I were to change any of that out, what kind of improvement could I see?

What the standard dark image problems? I don't really seem to have dark corners, at least not horribly. The center is brighter though.

rearden

Take a look at the backside of htat sheet that you're projecting onto. I'll bet that the image is brighter from behind than it is from in front.

Try putting something opague back there, like a piece of white posterboard or something and see if that helps out. Even better, try a mirror.

You should be able to get a fairly bright image from this setup.

OK, Screen design was on the list after projector design. I have some BO cloth, but I wanted to wait and not use it in the garage and get it all dirty.

I want to paint some kind of Light Fusion on the BO cloth or thick mylar and be able to roll it up. I probably am asking for too much, but I will add something behind it and see what happens.

rearden

I had a little time to wire up the 7805 last night and take some measurements. the +5v didn't work, so I need to backup and determine the pinout of a computer drive power connector.

Here are some of the measurements I took:

outside bottom of pro reflector to fresnel 26.8cm
bottom of fresnel to LCD 2.9cm
LCD to upper fresnel 4.8 cm

Bottom fresnel to to top lamp 19.5cm
Bottom fresnel to middle of lamp 22.0
Bottom frensel to top of reflector 24.5

Top fresnel to mid of mirror 36cm
Mid of mirror to wall of projector 20cm

Looking at these measurements, it looks like I could show some improvement by decreasing the bottom fresnel to lamp distance by about 1cm. This should put the light cone the at the top of the arc tube to be a bit over 1cm. The angle is about a 45deg, so it about a 1:1 relationship. If the reflector focus is 44mm, then the current relationship should put it somewhere inside the arc tube.

I could adjust some of the fresnel to LCD relationships to be a little bit closer together.

Does the fresnel need to be nearly perfectly centered along the centerline? So the circular centers need to be lined up? If I cut a fresnel does it need to be cut on both sides not just one? I did that when I cut them the first time, but I think I will need to cut a second time to correct for the LCD issue. Currently the top fresnel is slightly (<1cm) off center because of the LCD parts in the way.

rearden

Hi,rearden.
Yes it is important to have the fresnels lined up correctly,any off-centre fresnels will be detrimental to getting the optimun light throughput.if one fresnel is off centre,the light will not focus at the correct point.
If you need to recut your fresnel,you are right to say cut equal amounts from either side.
Hope this helps.
Cheers P

wow, a reply from both The Great SupraGuy and The Great Pun15her within a day of each other. (so unworthy, so unworthy)

Thanks for the confirmation. I will see if I can avoid cutting the fresnels, it is such a messy and potentially destructive operation, but if I have to, then I will try to balance the cut.

Punisher, thanks for your plog, I used it heavily in my design, it is kind of hard to match your workmanship though.

rearden

I moved my lamp and reflector assembly ~1cm closer to the fresnel and fired everything back up. I need to install the real fans and get the back on. There is quite a bit of light spillage. There is so much wasted light, there must be some way to harvest it! Anyway, here is the standard lumenlab test image projected onto the bedsheet, but it seems that my camera didn't focus right. The word "LAB" and leeloo's forehead have a sheet of paper taped up behind the sheet to provide some idea of what a better screen would do.
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Here is another picture of my Ceiling Aberation. I think it is due to light leakage around the fresnels and hitting the triplet at a strong angle. These are taken of a piece of paper right in front of the triplet.
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Evidently I need to master the art of dark photography with my camera, because practically none of my pictures came out. I spent another good portion of Saturday and Sunday afternoon/evening tweaking and fiddling. I have several minor issues and one major issue which I will show later.

I still have not gotten the power requirements for my temp monitor sorted out.

I put an allelectronics temp switch (70C) in the circuit and it kept cutting out after 15 min, so I removed it, but that caused other things to break and a while to repair.

It seems like this projector is quite fragile. As in things like the LCD is just laying in the frame. A simple josle could shift the LCD out of location. The same would happen with the lamp. I welcome any ideas on how to make the LCD more stable but yet also still be able to remove it easily.

I had some heat trouble. The colors started to turn brown, then a halo around everything and then a dark center spot. So I spend some time filling air leaks and tightening up the air path. I think I am going to have to route out another hole for the second fan.

My fresnels are bowed and will not lay flat except with external help. For the top fresnel, the second lexan lays on top of it to force it flat rather than under it to support it.

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Here is a shot of the screen with text on it. My major problem is that I cannot get a continious focus. The center is focused but the top and bottom will not. I also seem to have some dark corners.
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These shots attempt to show the focus issue.
What I wanted to show in both of them was how parts of the image were in focus and others were not.

I could make the center of the image focus sharply but then the top and the bottom would be totally un readable and painful to observe. If I brought the top or the bottom into focus then the center would be out. I find it odd that it is the top AND the bottom out of focus. I could understand it better if it was one corner or the top or the bottom, but just the center is disconcerting.

I don't know what to tweak from here. I thought it was because the fresnels weren't laying flat. Now they appear to be quite flat. The FS mirror is bonded to 1/2 MDF so it would be pretty hard for it to bow.
The LCD is laying flat in the frame. Please help!
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Do the top and bottom come into focus at the same time,and the middle separately?
If so,then that would indicate bowing somewhere along the optics.
If you can get the top to focus,then the middle,and then the bottom,all at different focus lengths,that would indicate something not being perpendicular to the light path.maybe a fresnel,maybe the lcd.
Get that ruler out and measure those gaps!!
I hope my crappy explanation makes sense?
Cheers P

I spent about 4 hours last night in a cold garage with a fan blowing on me attempting to get the @#$%# focus right
and was not sucessful.

I started off by measuring and getting all the fresnels and LCD at a pretty even relative position to each other.
It seems (orginally) that the focus banding was because the top to too far, the center correct and the bottom too short. I eventually tilted the screen and things came into reasonable focus and keystone. I still haven't mastered dark room screen shots, so I don't ahve pics. (I tried the "night shot" setting last night and all I got was a white sheet...)

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