The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Increasing IR LED Output
References: <3D9F5B9E.70DB3C27@apt0.sao.arizona.edu> <3D9F8489.9FE65295@webaccess.net> <3D9FADEE.D3713FC5@apt0.sao.arizona.edu>
Date: Sun, 06 Oct 2002 12:37:26 GMT
NNTP-Posting-Date: Sun, 06 Oct 2002 05:37:26 PDT
Louis Boyd wrote:
> Chuck Simmons wrote:
> > Louis Boyd wrote:
> > >
> > > A better approach is to mathematically add adjacent frames to reduce
> > > noise. For example, display the sum of the last 20 fields. (1/3 sec).
> > > Some additional smearing will occur but isn't particularly annoying to
> > > watch. Cooling the CCD with thermoelectrics will reduce noise allowing
> > > higher gain. Some security cameras use these techniques.
> > Perhaps I am a bit off of the wavelength you are on but mathematically
> > adding frames is not as good for reducing noise as integrating on the
> > CCD itself. If the CCD is capable of slow scanning (most are), it would
> > be better to scan and grab one frame every 1/3 second than to grab the
> > sum of 20 frames (this assumes industrial sync with 60 frames per second
> > rather than TV which is 30). Moreover, this technique only reduces noise
> > in the stationary background. Moving objects are not as much improved.
> > Have I missed something?
> I agree that you usually get a better image by integrating on the chip,
> at least if thermal defects aren't dominant. However, for human viewing
> having the image change every 1/3 second or so is quite annoying. The
> method of adding new frames and dropping old one is still changing 30
> times a second so the eye tends to smooth the changes. Yes, it looks a
> bit "wormy" because the noise patterns have persistance. With memory
> (required for chip integration and adding multiple frames) it's also
> practical to remove any static defects, such as hot pixels and "clocking
> noise" which can help a lot.
> Moving objects, if viewed with a "strobed" LED will give a series of
> overlapping clear images rather than a smear. That can work with either
> on chip integration or memory integration and makes easier to see what
> the object was and estimate it's velocity and direction. None of these
> approaches beats having adequate lighting and continous frames faster
> than the eye's flicker response rate.
> Another way (perhaps obvious) to perk up the sensitivity of a CCD camera
> is to use a faster lens. The penalty is cost and reduction of depth of
> Lou Boyd
Thanks. I wasn't sure we were quite on the same page. We seem to be. I
am embarrassed that it took me half an hour to show that integrating on
a CCD is better than integrating off chip. Alzheimers I guess.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons email@example.com
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup