Re: Lens design questions

On Aug 15, 5:40 pm, Anonymous <x...@xxxxxxxxxxxx> wrote:
I am designing a device that will project a 35mm wide object onto a 7mm camera sensor (3MP). One of the objectives is to keep the distance between the object and the sensor small (less than 20cm or 8").
I understand that if I just use a single double concave lens, in theory, it should work. However, I don't know much about other effects (aberrations, etc) that should be accounted for to maximize the image quality.
My question is: how does one go about designing a lens system that will make a 'good' image?
Thanks in advance for any advice, pointers, information...

- Ivan

Richard is absolutely correct when he suggests you will be much better
off (financially and in terms of image quality) buying a commercial
lens for this purpose. My one minor quibble with his response is the
suggestion of a 28mm fl. wide angle SLR lens. 35mm object onto a 7mm
detector, with up to 200mm object to image distance doesn't require a
wide angle lens, nor an SLR lens.

Stick with a 12.5mm or 16mm fl. c-mount lens made for CCD cameras.
Even if you stay with a cheap brand (Ultrak, Rainbow, Cosmicar),
you'll get much better image quality than what you would be able to
"roll" yourself for the same money.

Quick example: Ultrak 16mm fl. F/1.6 lens. This lens is 26mm long
(from c-mount surface to front flange). The front focus is 14mm
inside the front flange.
For your mag. of 7/35 = 0.2X, the Newtonian object distance (measured
from the front focus) is 80mm. Thus, the distance from the front
flange of the lens to the object is only 66mm.

Now, you'll also want a couple mm worth of spacer between the lens and
the (presumed) c-mount surface of your camera, then focus the lens for
near objects to account for the other 1.2mm worth of spacer (total
3.2mm) .

If indeed you are using a c-mount camera, then the total image to
object distance is: 17.53mm (c-mount distance) + 3.2mm (spacer, focus
adjust) + 26mm (lens body) + 66mm (object flange distance) ~ 113mm.

What kind of camera *do* you have? If this is just a chip on a board,
then you'll have to do a little mechanical work to provide a female c-
mount (1" diameter, 32 TPI). But this is only a small amount of
mechanical effort compared to what you would have to do if you were
rolling your own imaging lens and housing, etc.

Spencer
======================
LIGHT WORKS, LLC
http://www.LW4U.com

.

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