Delta Lens

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Hello, I'm new to this forum, I wish I would have looked here before I started on this project but whatever. Also I've searched this forum, and I don not feel this has been mentioned before(this specifically). I'm currently building a projector out a sony ps1 lcd, and a compact delta I lens by us precision lens. This is out of an RCA (hitachi) big screen television.

Anyhow, I'm very pleased by the progress so far, but I have a problem with my lens. I seems to have a focusing problem (the lens is curved?) I found that the focus is not consistant horizontally. I feel this is a problem with the orignial CRT shape not being the same as the new 5" lcd screen.

I was wondering if anyone had information on Delta Lenses (I saw a post stating that the Delta IV(I think) is curved. I want to change to a new lens very soon, I was consitering(sp?) a overhead projector lens but I'll have to see. I currnetly have removed the refective backing on the back of the sony lcd back light, then I have the new light shining through the LCD to the delta lens. What I was wondering does one need the same fresnel lens when using a overhead projector head unit or can I use the one that is inside the orginal (sony) backlight?

Delta IV Lense


I am using pieces of a Delta IV lense in my projection project. What I found is that there are three lenses inside the assembly. The first is a 2" thick PlanoConcave lense (big and heavy enough to use as a boat anchor!) this is what warped the image slightly to match the CRT screen. The second is a condenser lense, and the final objective is a PlanoConvex. I took the first lense (PlanoConcave) out and it fixed the focusing problem. The problem that it left me was that the LCD has to be right up against the lense assembly to focus and then the picture was about 20 feet across. If the projector was only a couple of feet from the wall I guess you could get away with it, but then it would be in the way to watch the movie. They were originally designed to only throw the image about 12", onto a rear projection screen.

I have since begun using a fresnel as my focusing objective, and moved the condenser and planoconvex objective right in front of the MH light bulb. This has increased my brightness.

Optical sequence like this:

Lightbulb - condenser - planoconvex - fresnel up against LCD(ridges facing LCD) - LCD - fresnel (ridges facing wall)

the condenser and planoconvex have to be right up against and touching each other. Make sure the condenser doesn't touch the light bulb though. even though it's glass, it will boil the glass and cause bubbles in the surface of the lense and also in the glass bulb outer casing. Maybe leave about 1" spacing. with this setup I get about a 5' x 3' picture from about 10-12' away. I'm working on the brightness now with refelctor designs and such.

I should have pic's posted on the DIY Projector II project forum soon.

hope it helps,
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