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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Using QX3 microscope for SMT
References: <email@example.com> <3D9E2EBF.535EE22A@mfi.net>
Date: Sat, 05 Oct 2002 02:39:17 GMT
NNTP-Posting-Date: Fri, 04 Oct 2002 19:39:17 PDT
"Michael A. Terrell" wrote:
> Ivan wrote:
> > I was thinking about getting Intel's QX3 toy microscope to do some
> > fine pitch soldering instead of buying a magnifying lamp or a real
> > microscope. Has anyone tried this? Any opinions?
> > Ivan.
> The thing has too much magnification, and very poor lighting. (10X,
> 60X, 200X)
> I tried the same idea a couple years ago. Now it sits on the shelf
> next to the computer and all I use it to read part numbers. The frame
> rate is very slow, so any movement causes jumpy images. Also, since it
> isn't a stereo scope it has terrible depth of field. Only part of a part
> is in focus at a time. I have some images I can post if you want to see
> the image quality.
The depth of field problem exists with all microscopes. If a small NA is
used, the illumination is dismal but the depth of field large. A large
NA will do better for illumination but at the expense of depth of field.
It gets worse. Standard microscopes all have a 160mm tube length which
means that the NA of the objective is related to its power. The higher
the NA, the higher the power of the objective. For example, a 4X
standard objective has an NA of 0.1 typically. A 40X is has an NA of
maybe 0.65. A 100X objective may have an NA of 1.25 but an NA greater
than 1 requires immersion oil.
In general, you want a moderate NA not high) to get depth of field and
built in top illumination to get a bright field. Microscopes in this
class are non-standard but available new for about $200US and up.
Younger people and myopic people can get by with low powers like 2X or
3X for 0.5mm pin pitch. The reason myopia can help is that the myopic
has a very short working distance with the uncorrected eye. My
comfortable working distance without glasses is about 3 inches. I need a
lot of light to get good depth of field with my unaided eye.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org
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