Re: Do achromats shift an image?
- From: mpate@xxxxxxxxxxx
- Date: 30 Nov 2006 00:47:23 -0800
On Nov 29, 10:28 pm, "Doc" <docsavag...@xxxxxxxxxxxx> wrote:
Trying to project movie film through a couple of 60mm achromats, as per
other posts in here. I've been trying to find the optimum distance to have
them apart to get the entire image within the confines of the lens. Have
them mounted on either end of a PVC pipe and keep trimming it down a little
at a time.
However, I find that when I have them lined up as exactly parallel to and
centered with the projector lens as I can make it, the image I see is
shifted to one side. In other words, when I look at the image reflected in
the end lens or in the mirror (mounted at 45 deg), on side of the frame runs
off the boundary of the lens while there's quite a bit of space on the other
side.
The only way I'm able to get the whole frame within the lens is either push
the lenses off to the side to where the projeced inage is aimed quite a bit
off-center, not pointing directly at the center of the lens. Or, skew the
angle of the pipe they'r mounted to so it's very noticeably off parallel
from the line of the projector lens.
Why is this happening? If the image is centered going into the first lenss
and they're both in line with and parallel to each other and the projected
image, shouldn't the image coming out the other end be centered within the
lens?
Thanks for all input.
It sounds like your projector has offset.
Offset in digital projectors is where the DMD, LCOS, or LCD panel is
offset from the optical axis of the projection lens.
This is typically done so that if a projector is sitting on a
conference room table or mounted on the ceiling part of the image wont
be intercepted by the table top or ceiling respectively.
I havent seen a sketch or photo of your proposed system but it sound
like your condenser lenses are not big enough for the footprint of the
illumination.
If you tilt the optical axis of these lenses (pvc tube axis) off of the
optical axis of the projection lens, then you will get into what is
called the schiempfluge condition where you will have a tilted object
plane and a tilted image plane and your image will have keystone at a
minimum.
I think putting up a sketch of what your trying to do will enable the
fourm members to help you more efficiently.
Michael
www.oscintl.com
Check out my new ebook on Digital Projector Technology at
http://www.oscintl.com/dpt_ebook.htm
.
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