Jerry Avins wrote: PLEASE fix your newsreader, your replies are not shown in the thread they belong in, but as single RE: messages and are cluttering this newsgroup The culprit is your reply-to header, which should contain a email-address, NOT, repeat NOT comp.dsp@googlegroups.com From your header: Reply-To: comp.dsp@googlegroups.com Thank you
hey, have you guys ever heard of this?
Started by ●April 6, 2011
Reply by ●April 10, 20112011-04-10
Reply by ●April 10, 20112011-04-10
Jerry Avins wrote: PLEASE fix your newsreader, your replies are not shown in the thread they belong in, but as single RE: messages and are cluttering this newsgroup The culprit is your reply-to header, which should contain a email-address, NOT, repeat NOT comp.dsp@googlegroups.com From your header: Reply-To: comp.dsp@googlegroups.com Thank you
Reply by ●April 10, 20112011-04-10
Jerry Avins wrote: PLEASE fix your newsreader, your replies are not shown in the thread they belong in, but as single RE: messages and are cluttering this newsgroup The culprit is your reply-to header, which should contain a email-address, NOT, repeat NOT comp.dsp@googlegroups.com From your header: Reply-To: comp.dsp@googlegroups.com Thank you
Reply by ●April 11, 20112011-04-11
On Apr 7, 12:01�pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote:> On Thu, 7 Apr 2011 06:58:03 -0700 (PDT), Clay <c...@claysturner.com> > wrote: > > > > > > >On Apr 6, 10:49=A0pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote: > >> Clay wrote: > >> > Most definitely optical processing has and is being done. > > >> Before the era of DSPs, the synthetic aperture radars used to do the > >> processing by optical means; that is recording the radar data to > >> photographic film and then exposing it like a hologram. > > >> Vladimir Vassilevsky > >> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com > > >In fact when Gabor invented holography in about 1947, his object and > >reference beams were coaxial. It wasn't until 1963 when Lieth and > >Upatnieks applied the idea of side looking radar to the holography > >problem and created off axis holography. This has a great advantage > >that the image is no longer corrupted by the reference illumination > >light. > > >Clay > > SAR is not the same thing as holography, though. � SAR can be (and has > been) processed optically, but a signal flow diagram of the optical > processor is essentially the same as it is for a digital processor > doing 2-D fast correlation. � FT -> multiply by mask -> IFT then > repeat in the other dimension. > > Eric Jacobsenhttp://www.ericjacobsen.orghttp://www.dsprelated.com/blogs-1//Eric_Jacobsen.php- Hide quoted text - > > - Show quoted text -True it is not the same, but it shares the fact that an interfernce between the reflected signal and source signal is recorded. It is this property that enables the depth recording that wows viewers of holograms. I've seen where SAR data is recorded on film and then viewed holographically so even this 2 step process of image recording and image reconstruction via diffraction is in common with holography. Plus there are even tricks for doing lens less fourier transform holography - here you match up image and reference distances to narrow the spatial frequency range required by the recording medium. I was just trying to point out there is more in common than most would initially think. A big difference in practice is the coherence lengths of the source illumination with radar's being miles and the optical being meters or less. Clay
Reply by ●April 11, 20112011-04-11
On Mon, 11 Apr 2011 08:03:24 -0700 (PDT), Clay <clay@claysturner.com> wrote:>On Apr 7, 12:01=A0pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote: >> On Thu, 7 Apr 2011 06:58:03 -0700 (PDT), Clay <c...@claysturner.com> >> wrote: >> >> >> >> >> >> >On Apr 6, 10:49=3DA0pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote: >> >> Clay wrote: >> >> > Most definitely optical processing has and is being done. >> >> >> Before the era of DSPs, the synthetic aperture radars used to do the >> >> processing by optical means; that is recording the radar data to >> >> photographic film and then exposing it like a hologram. >> >> >> Vladimir Vassilevsky >> >> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com >> >> >In fact when Gabor invented holography in about 1947, his object and >> >reference beams were coaxial. It wasn't until 1963 when Lieth and >> >Upatnieks applied the idea of side looking radar to the holography >> >problem and created off axis holography. This has a great advantage >> >that the image is no longer corrupted by the reference illumination >> >light. >> >> >Clay >> >> SAR is not the same thing as holography, though. =A0 SAR can be (and has >> been) processed optically, but a signal flow diagram of the optical >> processor is essentially the same as it is for a digital processor >> doing 2-D fast correlation. =A0 FT -> multiply by mask -> IFT then >> repeat in the other dimension. >> >> Eric Jacobsenhttp://www.ericjacobsen.orghttp://www.dsprelated.com/blogs-1= >//Eric_Jacobsen.php- Hide quoted text - >> >> - Show quoted text - > >True it is not the same, but it shares the fact that an interfernce >between the reflected signal and source signal is recorded. It is this >property that enables the depth recording that wows viewers of >holograms. I've seen where SAR data is recorded on film and then >viewed holographically so even this 2 step process of image recording >and image reconstruction via diffraction is in common with holography. >Plus there are even tricks for doing lens less fourier transform >holography - here you match up image and reference distances to narrow >the spatial frequency range required by the recording medium. I was >just trying to point out there is more in common than most would >initially think. A big difference in practice is the coherence lengths >of the source illumination with radar's being miles and the optical >being meters or less. > >ClaySAR is essentially a 2D correlator, with one dimension matched to the transmit pulse and the other to the quadratic phase response that a target makes as it passes through the beam. I'm not familiar with the details of holography. Does it include transmit pulse matching? Eric Jacobsen http://www.ericjacobsen.org http://www.dsprelated.com/blogs-1//Eric_Jacobsen.php
