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From: rstevew@armory.com (Richard Steven Walz)
Subject: Re: DRAM's & CCD's, idea
Organization: The Armory
Date: Thu, 25 Aug 1994 09:21:01 GMT
Message-ID: <Cv33B6.Fpv@armory.com>
References: <R.F.Pointon.23.000F85D5@massey.ac.nz> <weathersd.6.000FD44A@metro.or.gov> <BILLW.94Aug24174006@glare.cisco.com>
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In article <BILLW.94Aug24174006@glare.cisco.com>,
William  <billw@glare.cisco.com> wrote:
>    I think that pinhole cameras require a relatively long focal length, which 
>    won't be available if your pinhole is poked into the top of your chip.  
>
>    The focal length of the perforated DRAM pinhole camera will mean that it
>    will only be able to focus on things VERY close to the chip, and the image
>    will only cover a few pixels.
>
>Uh, I think that with a pinhole camera, the effective focal length IS the
>distance from the pinhole to the image.  This will mean that poking a hole
>in the lid of an IC will result in a "lense" with a very short focal length.
>This has little to do with focusing, since pinhole cameras have essentially
>infinite "depth of field", but very short lenth "lenses" tend to be much more
>subject to various forms of distortion, not to mention the fisheye effect
>(a very wide angle-of-view, implying that that part you WANT to see might
>be a very small piece of the image...)
>
>BillW
-----------------------------
No. Pinholes have all focal lengths and infinite depth of field. They are
in focus for all distances at once! But their light gathering is horrible,
and if you have the wrong sized one for your application, it's Airy disk
and fringes will mess up your images. That's pinhole interference to none
physicists out there. That looks like a sinc function.
-Steve Walz   rstevew@armory.com

