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sampling problem

Started by walala April 2, 2004
Dear all,

When I learned sampling theory I did not have any problem with it. But
recently some questions always haunted among my minds... I need your help...

I guess everything we sense is what have been sampled. I become suspect our
sensing organs. Our vision seems to have no problem, very clear in seeing
objects, but is it possible that our eyes only sampled an aliasing version
of the real-world and the actual object maybe is moving but we sensed it to
be stationary?

any thoughts?

-Walala


walala wrote:

> Dear all, > > When I learned sampling theory I did not have any problem with it. But > recently some questions always haunted among my minds... I need your help...
I like that! How many minds do you have? Do you use them all regularly? (Languages are peculiar in what is considered plural. Here, I get a hair cut. An Italian might ask, "Only one?" In my Kitchen, I drink water. In Vichy, one takes the waters.)
> I guess everything we sense is what have been sampled. I become suspect our > sensing organs. Our vision seems to have no problem, very clear in seeing > objects, but is it possible that our eyes only sampled an aliasing version > of the real-world and the actual object maybe is moving but we sensed it to > be stationary? > > any thoughts?
It is said that the most active and imaginative hypochondriacs are medical students. Do you have any reason to suppose that our sensory organs function by sampling? Nerve impulses act in bursts: is that what you mean? By the way, I'm still carrying blocky Lena on my web site. Do you still want access to the image? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
"Jerry Avins" <jya@ieee.org> wrote in message
news:406def24$0$3046$61fed72c@news.rcn.com...
> walala wrote: > > > Dear all, > > > > When I learned sampling theory I did not have any problem with it. But > > recently some questions always haunted among my minds... I need your
help...
> > I like that! How many minds do you have? Do you use them all regularly? > (Languages are peculiar in what is considered plural. Here, I get a > hair cut. An Italian might ask, "Only one?" In my Kitchen, I drink > water. In Vichy, one takes the waters.) > > > I guess everything we sense is what have been sampled. I become suspect
our
> > sensing organs. Our vision seems to have no problem, very clear in
seeing
> > objects, but is it possible that our eyes only sampled an aliasing
version
> > of the real-world and the actual object maybe is moving but we sensed it
to
> > be stationary? > > > > any thoughts? > > It is said that the most active and imaginative hypochondriacs are > medical students. Do you have any reason to suppose that our sensory > organs function by sampling? Nerve impulses act in bursts: is that what > you mean? > > By the way, I'm still carrying blocky Lena on my web site. Do you still > want access to the image? > > Jerry > -- > Engineering is the art of making what you want from things you can get. > &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095; >
Hi, Jerry, nice to see you again! I just feel curious about such things. Everything going on this world is a discrete sampling... For example, the teacher teaches a class wish to sample the study process and evaluate the effect of teaching and learning by homeworks and exams; the battlefield spy-monitor should send out as little as possibel information to avoid being detected but at the same time sending out enough information to let the receiver figure out what's going on there... Just want to say something to the group and see if somebody else can make some analysis by answering me... Talking about that Lena image... thanks you very much for hosting it. I no longer need it. Have a nice weekend! -Walala
On Fri, 02 Apr 2004 17:07:32 +0000, walala wrote:

> I guess everything we sense is what have been sampled. I become suspect > our sensing organs. Our vision seems to have no problem, very clear in > seeing objects, but is it possible that our eyes only sampled an > aliasing version of the real-world and the actual object maybe is moving > but we sensed it to be stationary? > > any thoughts?
Hmm, sounds to me like some this question is mostly covered by research in Cognitive Science. AFAIK Cognitive Science is somewhere in between Informatics, Philosophy and Biology. Maybe you can find something from google for that keyword. Till -- Please add "Salt and Peper" to the subject line to bypass my spam filter
On Sat, 03 Apr 2004 11:40:09 +0200, Till Crueger wrote:

> On Fri, 02 Apr 2004 17:07:32 +0000, walala wrote: > >> I guess everything we sense is what have been sampled. I become suspect >> our sensing organs. Our vision seems to have no problem, very clear in >> seeing objects, but is it possible that our eyes only sampled an >> aliasing version of the real-world and the actual object maybe is >> moving but we sensed it to be stationary? >> >> any thoughts? > > Hmm, sounds to me like some this question is mostly covered by research > in Cognitive Science. AFAIK Cognitive Science is somewhere in between > Informatics, Philosophy and Biology. Maybe you can find something from > google for that keyword.
I just remembered something else which you might have a look at, if you want to go deeper into the subject. There is a project at the Neuro-Informatics department of my University, trying to help blind people. They have done a lot of research towards discovering the way vision works in the Human eye. You could have a look at http://nero.uni-bonn.de and look under projects. Till -- Please add "Salt and Peper" to the subject line to bypass my spam filter
In article <c4ko7p$kvv$1@mozo.cc.purdue.edu>, walala <mizhael@yahoo.com> wrote:
>I guess everything we sense is what have been sampled. I become suspect our >sensing organs. Our vision seems to have no problem, very clear in seeing >objects, but is it possible that our eyes only sampled an aliasing version >of the real-world and the actual object maybe is moving but we sensed it to >be stationary?
Simple versions of sampling theory do not seem to apply to human vision. The retina cells are not arrayed on a regular grid or any sort of regular pattern. There are big holes right in the middle of the sampling array. And any "sampling intervals" are neither synchronous nor evenly spaced in time. Then afterwards the raw neural data is processed in a manner very susceptible to both optical and cognitive illusions (for instance, the normal imperceptability of those big holes). Is there a DSP theory which covers sampling at non-periodic randomized intervals or by a similarly randomized grid? IMHO. YMMV. -- Ron Nicholson rhn AT nicholson DOT com http://www.nicholson.com/rhn/ #include <canonical.disclaimer> // only my own opinions, etc.
rhn@mauve.rahul.net (Ronald H. Nicholson Jr.) wrote in message news:<c4m52l$ro$1@blue.rahul.net>...
> In article <c4ko7p$kvv$1@mozo.cc.purdue.edu>, walala <mizhael@yahoo.com> wrote: > >I guess everything we sense is what have been sampled. I become suspect our > >sensing organs. Our vision seems to have no problem, very clear in seeing > >objects, but is it possible that our eyes only sampled an aliasing version > >of the real-world and the actual object maybe is moving but we sensed it to > >be stationary? > > Simple versions of sampling theory do not seem to apply to human vision. > The retina cells are not arrayed on a regular grid or any sort of regular > pattern. There are big holes right in the middle of the sampling array. > And any "sampling intervals" are neither synchronous nor evenly spaced > in time. Then afterwards the raw neural data is processed in a manner > very susceptible to both optical and cognitive illusions (for instance, > the normal imperceptability of those big holes). > > Is there a DSP theory which covers sampling at non-periodic randomized > intervals or by a similarly randomized grid? > > > IMHO. YMMV.
I did some work on this topic. For 1-D, (Nyquist)sampling density is what it counts (necessary & sufficient) to restore signals from non-uniform samples. In 2-D, however, (Nyquist)sampling density is only a necessary condition. Seung
Ronald H. Nicholson Jr. wrote:

(snip)

> Simple versions of sampling theory do not seem to apply to human vision. > The retina cells are not arrayed on a regular grid or any sort of regular > pattern. There are big holes right in the middle of the sampling array. > And any "sampling intervals" are neither synchronous nor evenly spaced > in time. Then afterwards the raw neural data is processed in a manner > very susceptible to both optical and cognitive illusions (for instance, > the normal imperceptability of those big holes).
> Is there a DSP theory which covers sampling at non-periodic randomized > intervals or by a similarly randomized grid?
Theoretically Nyquist still works on the average sample spacing. Practically, you have to be careful when you do it. -- glen
walala wrote:
> but is it possible that our eyes only sampled an aliasing version > of the real-world and the actual object maybe is moving but we sensed it to > be stationary?
It's possible for your eyes to see a sampled image if it's lit using flourescent lights, but the sampling effect is from the lighting, not form the eyes. Users of table saws (and similar machinery) are warned to be careful when using them in flourescent light, because the strobe light (sampling) effect can make it appear that the blade is not moving when indeed, it is! -- Jim Thomas Principal Applications Engineer Bittware, Inc jthomas@bittware.com http://www.bittware.com (703) 779-7770 There's a fine line between clever and stupid