Prev: Semaphores in DSP/BIOS
Next: Interpolator/Decimator Question
From: Steve Pope on 29 May 2010 20:06
dbd <dbd(a)ieee.org> wrote:

>On May 29, 1:51�pm, spop...(a)speedymail.org (Steve Pope) wrote:

>> Yes. �In the simplest case I believe the blur of defocusing is
>> like a 2-D sinc function.

>Sinc functions go negative in the first sidelobe. None of my blurred
>pictures have negative values.


Funny how negative audio sounds just the same as positive audio
too.


S.
From: robert bristow-johnson on 29 May 2010 21:19
On May 29, 7:54 pm, dbd <d...(a)ieee.org> wrote:
> On May 29, 1:51 pm, spop...(a)speedymail.org (Steve Pope) wrote:
>
>
>
> ...
>
> > Yes.  In the simplest case I believe the blur of defocusing is
> > like a 2-D sinc function.
>
> > Steve
>
> Sinc functions go negative in the first sidelobe. None of my blurred
> pictures have negative values.

i don't think it's the sinc() function in the spatial domain, is it?
i think it's a rect() function (which is always non-negative) in the
2D spatial domain which is convolved against the sharp image to get
the blurry image. the 2D sinc() function is in the "frequency" domain
(or the inverse-spatial domain), no?

r b-j
From: dbd on 30 May 2010 01:19
On May 29, 5:06 pm, spop...(a)speedymail.org (Steve Pope) wrote:
> dbd  <d...(a)ieee.org> wrote:
> >On May 29, 1:51 pm, spop...(a)speedymail.org (Steve Pope) wrote:
> >> Yes.  In the simplest case I believe the blur of defocusing is
> >> like a 2-D sinc function.
> >Sinc functions go negative in the first sidelobe. None of my blurred
> >pictures have negative values.
>
> Funny how negative audio sounds just the same as positive audio
> too.
>
> S.

Audio is sensed with microphones with sensors smaller than a
wavelength and capable of transducing positive and negative excursions
from the average pressure.

Photographic image sensors have individual sensors larger than optical
wavelengths and produce outputs proportional to photon counts. The
counts do not go negative.

Run your audio through an AM demodulator and see if the output from
the demodulator sounds like the input for your 'positive' and
'negative' audio sounds.

Dale B. Dalrymple
From: Rune Allnor on 30 May 2010 06:31
On 29 Mai, 05:52, "Nitram" <morris.vian(a)n_o_s_p_a_m.gmail.com> wrote:
> Hi,
>
> My question might be simplistic as neither optics nor image processing is
> my field.
>
> Firstly, I was wondering if it is possible to compensate for a picture
> taken by an out-of-focus digital camera by doing a 2D deconvolution on it
> (MMSE filtering or something like that), in order to recover  the in-focus
> picture
>
> Secondly, can the optical transfer function between a properly focused
> picture and an out of focus picture be parameterized in such a way that a
> user could recover the image by gradually varying that parameter until the
> image is in focus?  If this is indeed possible, what is that transfer
> function? (any references to existing literature would be welcome).

The book "Digital Image Processing" (2009) by Gonzalez & Woods
treat this problem. One of their approaches start out with a
Wiener filter that represents the essentials of the deblurring
process. They then continue to suggest an interactive approach
based on the Wiener filter where the user interactively plays
with certain parameters to produce a deblurred image.

Rune
From: JimAtQuarktet on 31 May 2010 16:42
On May 28, 11:52 pm, "Nitram" <morris.vian(a)n_o_s_p_a_m.gmail.com>
wrote:
> Hi,
>
> My question might be simplistic as neither optics nor image processing is
> my field.
>
> Firstly, I was wondering if it is possible to compensate for a picture
> taken by an out-of-focus digital camera by doing a 2D deconvolution on it
> (MMSE filtering or something like that), in order to recover  the in-focus
> picture
>
> Secondly, can the optical transfer function between a properly focused
> picture and an out of focus picture be parameterized in such a way that a
> user could recover the image by gradually varying that parameter until the
> image is in focus?  If this is indeed possible, what is that transfer
> function? (any references to existing literature would be welcome).
>
> Thank you for your help.

I am sorry I was late for this discussion. The answer to this is yes,
and the answer to the second is yes. With a technique designated
SeDDaRA, the blurred image is compared to a reference image after
application of an FFT and the transfer function is derived. The
function is converted into a point spread function via an Inverse
FFT. Any deconvolution technique can then be used to deblur the
image. The process is fast compared to iterative tecniques, and at
least as effective. Examples can be found on our website at
http://www.quarktet.com/Gallery1.html as well more info about
SeDDaRA. Our software program Tria (free-to-try) enables easy
application of the method.

Best Regards,
Jim C
First  |  Prev  |  Next  |  Last
Pages: 1 2 3
Prev: Semaphores in DSP/BIOS
Next: Interpolator/Decimator Question