Newsgroups: sci.image.processing
From: paul@pcserv.demon.co.uk (Paul Carpenter)
Path: cantaloupe.srv.cs.cmu.edu!das-news2.harvard.edu!news2.near.net!news.mathworks.com!news.duke.edu!news-feed-1.peachnet.edu!gatech!howland.reston.ans.net!news.sprintlink.net!peernews.demon.co.uk!pcserv.demon.co.uk!paul
Subject: Re: Motion blur-free frame capture ?
References: <3k3m32$k0h@holodeck.iss.nus.sg> <3k4dsj$1m2@newsbf02.news.aol.com>
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Date: Thu, 16 Mar 1995 14:52:24 +0000
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In article <3k4dsj$1m2@newsbf02.news.aol.com> hayworth@aol.com "Hayworth" writes:
->Message-ID: <3k3m32$k0h@holodeck.iss.nus.sg>
->I have a question on how to obtain motion blur-free frames for moving
->objects.

The one thing you fail to mention is the velocity of the objects and if they
are all moving in the same direction.

Other things that would be useful would be type of objects, where they are
captured from as other ideas could become possible.

->As most CCD has analog video that is interlaced, i.e., odd field and
->even field, how is it possible to get a motion blur free full frame 
->resolution image ?  Is it achievable by just using a normal CCD high
->shutter speed CCD camera to grab a frame or must I get a non-interlaced 
->camera ?
....
->Jit Leng

Mark Hayworth replied -
-Jit:
-I believe that if your subject is moving, and your sensor (CCD camera)
-does not track your subject, and has a non-zero integration time, you will
-get blur -- no way around it.  How much blur is tolerable for you is
-something that only you can answer.  However, following are some things
-you can try to reduce the blur, roughly in order of decreasing
-effectiveness.

The main point to also remember is that the problem of blur is related to ANY 
image capture of moving objects, including photographic cameras. Hence this is
NOT related to the type of camera output but how the image is captured.

-1) If you know the velocity of your object and can accurately follow it,
-that will make your blur almost negligible.  (Observatories use this
-method to track stars.)  Obviously very expensive.

Also used in a lot of airborne, camera work, commercial and military with TDI 
cameras.

-2) Another option that you may have available is to use a strobe lamp with
-a very short burst of light (and using your regular camera) to illuminate
-your subject.

Or use constant light and acynchronous reset camera that integrates a frame at
a time, this can give interlaced video outputs Hitachi KPM1 and others. Watch
the specs and how integration is done related to your needs.

-3) You can reduce the blur by using a short integration time (high shutter
-speed as you say) but not all cameras will let you control their shutter
-speed.

See aynch reset above as often this can often be externally controlled. Amount
of integration possible is related to how much light can be made available
and velocity of object that determines min and max integration times.

This method is often used in factory inspection of production lines, because
light is controllable and object speed is known. Sometimes for print inspection.

-4)...

If velocity or range of velocities for the objects is known, light is 
controllable it is also possible depending on what you are looking at to use 
TDI type cameras (Time Displaced Integration), which take successive 
integrations of the object in different positions. However this is a line scan 
not area scan approach, that has to be tied in to the object and/or subjects 
relative velocity but often requires less in lighting.

Line scan is not an alien concept as this is the way in which photocopiers, 
scanners and fax machines work, which we all use every day!

-- 
Paul - "Any people you should meet are the products of a deranged imagination"
