Ok guys, my PJ has been finished for a while, although you wouldn't know it from my PLOG ... Anyway, I am having one HELL of a time getting the whole screen in focus. I can get both sides, and not the center.

(ALL PICTURES SIMULATED BTW)



Or.... I can get a single corner in focus, and everything else out...


Or... I can get the center in focus, and everything else WAY WAY out of focus...




So far, I have been compromising, and having everything equally out of focus, since thats as good as it gets for me. I have tilted/moved my triplet, moved/tilted my LCD 100 times, moved/tilted my front fresnel... Nothing lets me get perfect focus. I am using an unsplit config, with a Hyundia L72s LCD. Also, the center of the pic always looks like it has a double image, even when it is in near perfect focus. Any ideas?

Yoder

Very interesting as I am/was having the same problem. I ended up going back to a "straight shooting" design due to loss of focus and color "vibrance". I also found that the fold was loosing me 20% in lumens ! What mirror are you using ? I was using the LL mirror. Something I may try is to mount the mirror to a board to keep it flat and stiff... I noticed that the mirror will flex slightly and any flex produces variation in focus... not sure about the loss of lumens however... I was thinking about 6-8% loss, but 20% seems much too high.

cheers,
gs

I Assume your are using an FS mirror.. did you use the correct side of the mirror?

When i built my vertical projector i temporaraly put the mirror in backwards cause i didnt want to scratch the FS Side, i forgot i did this and wondered why my image was out of focus and double imaged.. then i remembered that it was in backwards and i flipped it. Pulled off the blue plastic protective sheet and everything was wonderfully clear.

Yeah, I think I might have to go to a straight path... Its a pain in the @$$ to redo everything, but this is gimped big time. My FS mirror is from LL, and mounted on a piece of 3/4" MDF, so I know its straight. Maybe my mirror angle is wrong.

Yeah, its the correct side. Do you get 100% corner to corner focus? Pro or standard lens's?

Yoder

No.. i dont get 100% focus.. but my problem is due to the 10deg. lens tilt i have.. i have to Correct the tilt with with field fresnel and its alot of keystone to correct.. so my bottom is never fully focused..

But everything else is pretty clear.

I have found that the incorrect fresnel focal length (as compared to your triplet) can do things like this (I think).

You might want to just DOUBLE and TRIPLE check your focal lengths on FRESNELS AND TRIPLET?

How do I do that? Do you mean make sure the correct triplet is in the correct location? That I am sure of, as well as the groove orientation. As for measuring the focal length, well, I don't know how, could you explain?


Thanks,
Yoder

Yoder, are you running split optics?

No, unsplit.

Have you got a pic of your projector? Something showing the triplet, mirror and fresnels.

DJ

Sorry guys, I was outta commission due to a random eye infection . Seriously... Anyway, here are some pics of my setup, hope this helps.

B.T.W. It goes, LCD->Fresnel->Fresnel->Tempered Glass->Lamp

The second picture tells the most to me. Offhand, the mirror doesn't look plumb (straight up-and-down) and the lens appears to be mounted askew (hard to tell with the blue masking tape used as a seal). The planes of your optics need to be very square and true. Besides being aligned in the light path, the fresnels, LCD, mirror, and triplet need to be on the same vertical plane (with the front fresnel adjustable for keystoning).

Yonder, any focus issues with your projector is a direct result of your objective lens not being lined up properly in relation to your lcd. I dont mean centered, i mean parallel on all sides, edges.

Contradictory to the way the pciture looks, the mirror is not angled like that . It sure looks like it though. I will double check and see how close it is to plumb. Also, yes, the triplet is angled, the focus is best like that.

Is it just the pic or is the triplet in the wrong way?

DJ

That triplet does look the wrong way round.The flange should be towards the mirror,(unless you have removed the flange??)
People are reporting that a rear surface mirror helps this problem,although I dont see how!
It would be relativeley cheap and easy to get one and place it over the fs mirror,just to see if it makes a difference.
There seems to be an intrinsic problem with bending with the pro optics.
This is bad news,as I am ordering my pro triplet this weekend.
On a good note.I have all the standard optics,so hopefully will be able to investigate this a bit more.
Having the centre focussed,but not any of the corners,makes me think of a heat distorted fresnel,with like a bump in the middle.I know that is not the case,hopefully we will figure out what the problem is here.
P

The triplet is Flange toward the LCD, as it is supposed to be. It just looks that way because it is mounted in a PVC barrel.

Yoder, Can you check these measurements. A should equal A and B should equal B. You said that you get the best picture with the triplet tilted. This suggests that the mirror may not be at 45° or the triplet is a bit lower than the reflected principal axis. I’m only guessing here; if the light didn’t enter the triplet and you adjusted the mirror by pivoting it at one side, this may have caused you focus issue.

DJ

Anyone else who is having focus problems with a mirror should check these measurements as well. And if the mirror does need to be adjusted it should be tilted along the centre not the ends. I’m not saying that this is definitely the problem but it would be a good place to start looking.

DJ

I’ve also got another thought as to what the problem could be. It’s very hard to judge by your mock up screen shots so I checked your plog. Is this the focus problem you are having? How far into the image does this blur extend? Does it only affect a band around the perimeter of the screen and then come good? Or is it a constant defocus from the edge to the centre? Are your fresnels cut to the same size or smaller than the LCD?
And this question has nothing to do with your focus problem just my curiosity . Have you flipped the LCD driver board over 270° so that it is in the front chamber?

DJ

Hi,
Looked at one of your pics of your mirror and noted something funky (perhaps).



If that line is straight, this means your mirror is bent???

Good idea, I will remeasure tommarow.

This was a VERY early screen shot(first actually), my screen doesn't look like that anymore. It was because my fresnel <-> LCD distance was too much, and the frame for my LCD's (about 1/4" bigger than LCD btw) was cutting off the light.

That was the first line I drew, I ended up using another line. I "thought" that red line was at like 89.5 deg, so after remeasuring, I made a new line, and put my mirror there.