Contents:
CRT projector case
Test box 1
Lens shifting techniques
Elliptical reflector
Torn FCC
Pro triplet
Test box 2
Theater plan
HQI and pre-condenser mount
First lux measurements
First screen shots
Current parts
A couple of light source tests
More screen shots
Broken LCD
Design concept
New LCD and fresnel holder
Dipole speakers
LCD lux measurements
Test box 3
A/g removed and new lux measurements
Screen shots
Arc image pics
Speakers
Osram HCI 150W
Iris


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I wasn’t going to make a plog on this pj because I’ve changed my plans half way through. I actually started building it before I was a member here. It’s been sitting ideal on my bench now for about 8 months while I figure out what optics I’m going to use. Procrastination is my worst enemy. I do all my testing on a temporary set-up.

Samsung 172mp LCD
3M 342mm Triplet
Osram HQI-TS 400W/D
395*395mm 220mmFL and 330mmFL fresnels
180mm cross-flow fan
19” CRT monitor case
64mm optical quality spherical reflector
100mm 200mmFL pre-condenser
4/ 50*50mm IR hot mirrors


The design was built around the lightpath. This was to keep its total size to a minimum. Its design methodology was to keep everything in a logical order for cooling. Basically the front chamber is going to be lined with a black washable filter, like a big sock. This was to keep the air intake as resistance free as possible and to allow a much larger time period between changes.
The cool air will pass over the front and down the back of the LCD. Then up passed the isolating glass and into a chamber at the top which houses the ballast. The air then makes its way down and around the heat shield box, which holds the lamp. It then makes its way forward then up and around an isolating sleeve so that the air can enter at the front of the main rear chamber where it finally can make its way past the lamp and exit the back. It’s a long trip for the air to travel so I tried to keep all the paths at a constant area so it isn’t restricted too much.
It will all be housed in a 19” plastic CRT monitor shell and other CRT shells cut and modified to fit. So it’s a box in a box inside a box.

The following two pics show the LCD frame with support for the PCB and where it sits in the PJ.

Side shot showing the CRT case.

Another angle.

And another

More

Just the aluminium case.

This is where the ballast will sit.

The top shows the hole where the air enters into the isolating sleeve. The bottom shows two of the shields in place.

I probably wont do too much to this design until I’m satisfied I can achieve good lens shift.

DJ

Here’s some pics of my current testbox.All the lenses and LCD can be shifted.

Wow DAZZLA, definately cool. You weren't kidding about the similarities to mine. Fitting that into a CRT case is going to be really neat. The test box is impressive in it's own right.

I have got to give this lens shifting another look. The construction of a fresnel tilt keystone is challenging enough but shifting the lenses looks even more challenging. Does it sacrifice brightness for focus?

Looking foreward to seeing more... but I'll be patient. Perhaps you will be able to educate us with some of your experiments while you figure out your final design?

Here are some pics on various lens shift technics. The first is split optics with the front fresnel and triplet shifted up and the rear is standard.

Now with un-split optics.

The outer edges of a fresnel are not really that good at refracting light so we end up with dim corners. Lens shifting suffers from this problem as well except it is exaggerated at the top of the screen so you end up with a reasonably lit screen at the bottom and middle and dark corners at the top. This can be compensated by shifting the rear fresnel and lamp down. Now the collimated light leaving the rear fresnel will be more intense at the bottom than the top. When it passes through the front fresnel it will pass less of the more intense light entering at the bottom and more of the dimmer light entering at the top. This results in a more evenly lit screen overall. Maybe even more so than the standard set-up.

Now one that is a hybrid. It uses lens shift and fresnel tilt.

Unsplit is my ideal set-up as it keeps the fresnels behind the LCD. The problem is finding a suitable triplet or small lamp. I’d love to test out the pro to see how it preforms but it’s out of my price range at the moment.

Here’s some more of my babbleings on lens shift.
http://www.lumenlab.com/forums/index.php?showtopic=8305&hl=

DJ

Here’s a brief outline of what happened in that last link I posted.
I decided to limit my LCD to 16:9 and loose 40mm top and bottom from my LCD. I set it up using a 6mm-arc length test lamp and it worked extremely well. Then I tried my 400W 25mm-arc length made the corners go out of focus. So it seems that arc length or I should say light control, plays more of a role in the final quality than I thought. Back to the drawing boards.

DJ

I tried the unsplit lens shift method, however, I got really nasty radial spokes in my projection when the fresnels were together and offset. I think that there needs to be some distance separating the lenses. Unfortunately, it's impossible for me to do so with the current box. I just don't have the room.

Ignoring the moire pattern, how did the image look?

Dazz,

Which 6mm lamp did you use? And what ballast did you use with it?

It’s a GE Arcstream, 6000hr, 10500 mean lumen, 4000K, 80 cri. I got the ballast and the lamp from a local junkyard for about $10 . I only use it for testing, hasn’t quite got the same power as the 400w. I’ve played around with it in an elliptical but getting the correct fresnel is crucial. I tried a few different pre-condensers, positive and negative but so far I haven’t had success. For a 17” LCD I need a rear fresnel FL of around 275mm. It just hasn’t got the same tweaking ability that a spherical has.


DJ
This is the elliptical I used it’s from an old profile spot stage lamp left over from when I use to be a lighting tech.

LOL - that is one sad looking reflector!!

Yes it has had a hard life. But it's still good enough to burn paper a the focal.

Fantastic.

I'm still using the lens shift, but the fresnels are no longer offset. This does result in some gradient in the lighting department, overall it's cost me the extra lumens that I capture by having more area, and the bottom of the screen is darker than the top, but only noticable in certain situations. (The lens shift is only 1" -- not much when you consider the the diameter of the pro lens.)

Any particular reason why you changed the fresnels back to standard?

JDJ

BTW: the “J” in “JDJ” stands for jealous

Yes. I changed them back to get rid of the moire patterns.

Even with the light not centered in the triplet, the image is awesome. If I were to undo the lens shift, I'd get back some brightness, but that's not a problem with the smaller image. As is, I'd rather keep the lens shift without the extra light.

With the fresnels shifted to keep the lens shift and center the light, the moire pattern becomes apparent on the projection. In fact, in the announcement, if you look closely, there's one slightly dark "spoke" in the projection towards the lower right. This is because of the fresnels not being aligned quite as well as they are now. That is a completely un-tweaked image, in fact the first one that I got after bolting in the lens the right way around.

With the fresnels shifted, there are dozens of spokes with fairly high contrasting levels radiating from the center area. I didn't like that at all.

Just a quick update that members might find interesting.
While I was installing my LCD into my test box I tore my FFC. :angry: These things definitely don’t like to be twisted. My gut instinct told me that this thing is going to tear while I was inserting it through the aluminium support, I should have listened to it. After my initial outburst and temper driven cupboard kicking I,m now walking with a limp, two mistakes in one day, I decided to see how bad the damage was. I plugged in the power and ….. I’m confused, the LCD still works! I can only guess that not all of the tracks are used. Phew..

DJ

naughty naughty,,


kitchen cubbies, are not for kicking,,

but then you know this heheheheheh

I feel an urge to build a new test box. My wife isn’t going to like it but I think it just has to be. One thing that is lacking in my last one is not being able to adjust lamp distances with out flooding the room with light. Another prob is that I can’t adjust the fresnels to operate in the normal way, (no lens shift). Hmm this might be tricky.

DJ

Hey Dazz,,,, Ima gonna go vert,, As soon as settled in new house,, cant wait,, and that glowies with the splitsies,, thanx to you sending those large fresnels,, will prove for sure what happens...

I hope you reinfornce that FFC so the tearing doesn't continue and take out some required traces!

Not yet but I will do before I touch it again. I’m thinking of coating it with epoxy or gluing some rigid plastic to the back to reinforce it.

DJ

Don't glue something rigid, or the edges of hte rigid material will just become a new stress point, and the cable will break there.

Epoxy is okay, so is strong tape, even hot glue would do a good job.

Good point. I think I’ll use some Gaffa tape it’s mildly flexible.

DJ

Being that the tear has already begun I would be concerned that if the area wasn't issolated from stress with something at least one what stiff the tear may be allowed to extend. I certainly understand your point about something rigid causing additional stress. possible sonething stiff but not rigid i.e. flexiable like a tine peice of plastic expoxied that would limit the bending at that point but still allow some gneral motion of the FFC.

Daz use 5 min epoxy,, done it before,, tape only gives grief long term

Is it possible to just cut the FFC back before the split and relocate the connector??

I thought about doing just that. I used some fine sand paper on an old FFC I had laying around and I was able to expose the tracks. My only concern is long term oxidisation of the bear copper. The question is, do I risk it and cut the FFC or just reinforce the tear? The perfectionist in me says cut it but the logical part says don't fix it unless it's broken.

Here’s the last screen shot I took from the old textbox. It is only an OHP sheet and the quality is dismal, I was in a hurry. The triplet was shifted 80mm, the LCD is a 17” the throw was 4000mm the screen size was 3000mm (cryptic clue ). This is about 75% shift. The entire screen was in focus but there was some pincushion distortion evident at the top not to bad though.

Started the new test box today so the old one had to go.

Look what I did to old faithful .
Took to it with a saw.

Ok here’s the new test box taking shape. I wanted this not to be as heavy so it will be made with an aluminium frame and clad with 1/8 mdf or cardboard whichever is on hand. It is 1100mm * 480 * 390mm. Yep it’s a big sucker but there is nothing like having a bit of room to work. I haven’t worked out the small details yet I’m just building it then make things fit. I want to still allow the fresnels to be shifted so I intend to make some frames that can be slid in or out from both top and bottom. The problem I had with the last box was that I couldn’t adjust the fresnels to the standard position so hopefully this one will be a bit better I’m not sure how I’m going to mount the lamp and reflector at the moment but it has to be adjustable from the outside and have enough vertical travel to match up with the rear shifting fresnel.

DJ

heheheheheheh hey daz,,the frame i understand,,, but the bags of cement,,, geeeezzzz bit drastic hehehehehhe,, and also the stud adhesive,,, heheheh bulk qauntities too !!!!!

Yep next one is going to be cast out of concrete and glued to the wall A clean desk is a sign of insanity.

DJ

how many customers cought it ?

None so far.

I didn't think that the clue was so "cryptic" but then I already know what the clue is.

Tablesaw. What a terrible fate for a faithful servant.

Oh well. I have my light box ready, now. I'm happy.

So Dazzla, what's the overall objective? I realise it's a testbed but what are you aiming for? Coffee table?ceiling mount? Other?

I used the 3dlens 220 & 330 fesnels, 17" LCD and orig LL triplet. My original design was for about 50mm shift and about 10° keystone. I'm not sure what the exact figures are now, there's been a lot of adjusting (and still more to come).

I'm projecting a 2m 4:3 diagonal with the triplet 1.5m from the projection wall. The centre of the projection is 1.1m from the floor, the triplet is 0.5m from the floor. Focus is a bit erratic and there's a slight inward bowing at the top, but it's extremely watchable for TV/DVD. Trying to see some windows icons and text is a bit hard at the extremities, but it's not mainly used as a PC anyway.

Light distibution top to bottom isn't too bad, but the triplet is killing it a bit. I'd love to get a 'short throw' pro lens, unfortunately the current pro won't throw a big enough pic at the pj's current (ideal) location.

I built a new house about 4 years ago and I included a purpose built theatre that has a step down in the floor so that the people in the second row can see over the top of the front row. It’s a great idea but it has made adding a diy projector a battle. I want to ceiling mount it but because of the step down the projector has to be higher so that you don’t bang your head in the second row. This makes it a double whammy. With the new text box I can take it into the theatre and do some more evaluation, everything I’ve done so far has been in the garage. Now that I’ve seen the old test box positioned back 4 meters from the screen I might fold it like Supra and place it between the two back seats. Have a look at the plans, it might make it easier to understand what I’m saying.
It’s been a very long journey and once the projector is finished, and we all know that never happens, I will have DIYed everything, the house, theatre, ventilation system, amplifiers, speakers, seating, screen, projector, HTPC and probably a few other things that I can’t think of right now . I know, I’m a gluten for punishment but it’s all great fun . Oh and my wife just informs me a couple of weeks ago that she want to build another one in about a year or so, what the? So I’ll have to do it all over.

DJ

edit: Guess which seat is mine.

I just had a really stupid thought. In the next house, if I can find the correct house lot, I could build the first ever DIY folded theatre. Hmmm maybe it's not so stupid.

DJ

This is just the idea I was discussing today with my brother. He has a commercial PJ now and seen my setup and he now is seriously contemplating a rear projection 120" with a DIY projector.