RPS Imaging Science Group

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Kind of inevitable really. As soon as you start to talk about Image Permanence you get an unfortunate example. The hard drive on my laptop, now around 5 years old developed a rather complex problem. Complex enough that the only cure will be to reload the operating system and salvage what I can from the file structure. This file structure contains several gigabytes of imagery.
After taking part in the development of ISO Image Permanence standards, including one on hard drive longevity you would expect that I would have backed all that data up. Especially as I gave a talk on this very issue at one of the RPS Imaging Science Group annual events – Good Picture 2006. See http://www.rps-isg.org/GP2006/alan_hodgson/img0.html for details.
Good job I did back it all up. Do you keep an up to date backup of your images too?

Read with interest an article in the February edition of the Imaging Science Journal – see http://www.maney.co.uk/articles-ims. The article entitled “Diagnostic quality of X-ray films digitised using conventional digital cameras” shows just how good digital cameras can perform against much higher spec flatbed scanners in practical situations. The article also directed me to a web site that allows comparison of various digital cameras. Take a look under http://www.imaging-resource.com/IMCOMP/COMPS01.HTM.
And remember – megapixels is not the only index of performance!

In addition to ISO standards there is a great deal of conference resource available on Image permanence. Here is a selection.
The Society for Imaging Science & Technology (IS&T) have a number of conferences covering this issue – see http://www.imaging.org/conferences/ . I have been along to a number of these and you can find report of my visits to the International Congress of Imaging Science under http://www.rps-isg.org/docs/ICISreport_alan_hodgson.pdf and to the NIP 23 (Non Impact Printing) meeting under http://www.rps-isg.org/docs/NIP23andDF07summary.pdf . There is also the Archiving series of conferences – see http://www.iop.org/activity/groups/subject/pgs/News/file_31431.pdf for an example. The next one of these is due to be held in Washington DC in May – see http://www.imaging.org/conferences/archiving2009/ for details. Nice time of year to visit DC- hope to see you there!

Image Permanence is a big issue as we move into the digital domain. New printing technologies bring new issues and the rise in the number of people keeping images in digital formats raises new problems too.
I hope to extend this blog to cover some of these issues. There are also some really good external resources. One of them is the International Standards Organisation. Technical Committee 42 covers standards pertaining to Photography – see http://www.iso.org/iso/standards_development/technical_committees/list_of_iso_technical_committees/iso_technical_committee.htm?commid=48420 . Within TC42 Working Group 5 looks at Image Permanence and we have a whole series of standards to guide users on Image Permanence issues. My friends at the Image Permanence Institute have a list of these standards in their Archival Advisor – see http://www.archivaladvisor.org/shtml/ISO.shtml.
I am the UK representative to this Working Group and today I was reviewing the latest version of ISO standard 18920. With the title “Imaging materials — Reflection prints — Storage practices” this covers best practice for the storage of monochrome and colour prints from both traditional and new printing technologies. Fibre or resin coated (RC) base, silver halide, instant prints, inkjet, colour copier, dye sub they are all in here.
Take a look. You can buy a copy from ISO or BSI or consult it in many libraries. If you keep prints it is a great resource!

I have been taking a look at the agenda for the IDTechEx Printed Electronics Europe meeting – see http://www.idtechex.com/printedelectronicseurope09 . I gave a talk on the use of paper as a substrate for printed electronics at one of their previous meetings (see http://www.iop.org/activity/groups/subject/pgs/News/file_27116.pdf for my notes) and I was keen to see how things have moved on.
Here are a few presentations that caught my eye.
1. Menippos GmbH is based in Chemnitz, Germany and develops technology for printed electronics. They have modified traditional printing press systems to print low cost electronic devices onto paper and other flexible substrates. It will be good to see where their technology has moved to as they now claim to be printing memory elements.
2. Bundesdruckerei, the German printing house is making a presentation entitled “Prospects and Challenges for ID Documents with Integrated Displays”. It looks like they will be covering flexible electronics including e-paper and OLED displays for secure ID systems. It will be interesting to see their roadmap for this.
3. Agfa Materials will be discussing their PEDOT electrode technology for printable electronics. Those of us from the photo industry may get a flashback to those antistatic conductive coatings we used to use on photo products!
If anyone is going to this meeting feel free to leave me a comment.

On Thursday the committee of the Printing and Graphic Sciences Group of the Institute of Physics came together by telephone conference. One of the items up for discussion was our future conference programme.
We run meetings on a wide variety of topics pertaining to Printing and Graphic Sciences – see http://www.iop.org/activity/groups/subject/pgs/Events_archive/page_7754.html for some details. One current focus is the topic of Printed Electronics but some overlap with the RPS Imaging Science Group too and we have started running joint meetings. For more details of our recent Digital Futures event check out http://www.rps-isg.org/DF2008_presentations.php.
Come and join us sometime!

In the news this week was the National Ignition Facility at Lawrence Livermore laboratory in California. They will shortly be completing the beam line to poke 1.8MJ laser pulses into a 2mm diameter sphere with a view to demonstrating nuclear fusion – see https://lasers.llnl.gov/ . This brought back a few memories from my involvement with photographic emulsions.
The development all this high technology ($4bio if you are a US tax payer) had a curious imaging twist. Putting this much energy in a small space generated a huge flux of radiation and energetic particles such as protons and electrons. The scientists wanted to analyse the energy spectrum of these particles and built a series of electron spectrometers.
In these units an incoming beam of charged particles is bent with electric or magnetic fields. As higher energy ones will be bent less by the beam, this produces a spatially distributed range of energies on a detector.
Because they do this sort of thing, they tried all sorts of electronic detectors which were pretty instantly fried by the local flux. Needing a detector that was much less sensitive to neutron flux and magnetic field gradients they ended up with good old fashioned photographic emulsion, which is where I came in. Some of this work is now available on the web – see https://lasers.llnl.gov/publications/icf_reports/icf_v1no2_00/2_hatchett_135029.pdf
Goes to show that traditional photographic products can still go where digital imaging fears to tread!

The Kepler focal plane array - picture from NASA

In a previous piece “Megapixel mania” I berate the continued quest for increasing megapixels in cameras. Here is an example where a huge number of pixels is justified when combined with some interesting optics. And it doesn’t even take pictures!
The newly launched Kepler Space telescope is an interesting imaging platform and it has a number of claims to fame in the imaging field. It is the widest aperture space telescope containing a 0.95-meter aperture, wide field-of-view Schmidt telescope, with a 1.4-meter primary mirror. For more on the Schmidt design I wrote an article on telescope designs for the 2006 International Congress of Imaging Science, reprinted as http://www.imaging.org/pubs/reporter/issues/Reporter21_4.pdf .
Although it leads to a compact unit a key issue with the Schmidt design is a curved image plane. This did not stop the Kepler team. The image plane contains a Focal Plane Array (FPA) consisting of a 14” x 14” substrate onto which 25 CCD modules (21 science and 4 fine guidance) are mounted. The curvature of the substrate is designed to match the optimal focal surface of the Schmidt telescope, which is closely described by a 1.4 meter spherical surface. You can see the curvature in the attached picture, found on http://science.nasa.gov/headlines/y2009/20feb_kepler.htm.
With more than 95 megapixels, the FPA of 42 backside illuminated CCDs forms the largest array of CCDs ever launched into space by NASA. Each e2v CCD imaging sensor used has 2,200 by 1,044 active pixels; 27-micron size; and 28-by-55-millimeter image area. The devices are back thinned to yield high quantum efficiency over the 400 to 900 nm wavelength range of interest and to minimize intra-pixel variability
The interesting point with this array is that it is not a camera but a photometer array covering an area of sky around 100 square degrees (about the size of your hand at arms length). The aim is to measure changes as small as 10 ppm in the brightness of stars, indicative of a planet in transit. This is a planet detector, not a camera! As such the image science is different. The CCDs are not used to take sharp pictures; the images are intentionally defocused to about 10 arc seconds to improve the photometric precision. The total system PSF (i.e. optics plus CCD) ranges from 4 to 7 pixels in diameter. This broad PSF is highly desired in photometric applications such as Kepler because it significantly reduces the sensitivity to intra-pixel variations and minimizes the number of stars that will saturate on the CCDs. For more on the optical design check out http://kepler.nasa.gov/pdf_files/95_Million_Pixel_FPA.pdf .
Best of luck to the Kepler team – image science in action!

Off today to present at a joint meeting between the Chester and North Wales branch of the British Computer Society (http://www.bcsmanchester.org.uk/ ) and the North West branch of the RPS. The day’s presentations were a joint effort too between myself and fellow Imaging Science Group member Tony Kaye.
Tony started off the day with a presentation on how digital cameras work. He covered the relative attributes of CCD and CMOS sensors, a previous subject of this blog. There was a large block on demosaicing and then on to colour management. I then took over to cover printing technology, image permanence and printed electronics. We hope to have the presentations live on www.rps-isg.org soon.
There is real value in these joint meetings as they bring together people and ideas from different backgrounds and disciplines. The RPS Imaging Science group already does joint events with the Institute of Physics Printing and Graphic Sciences Group – see http://www.iop.org/activity/groups/subject/pgs/index.html . The British Computer Society is a good fit with imaging science and we should do this sort of thing more often.