RPS Imaging Science Group

A monochrome camera board

Ever considered the technologies used in the image sensors in your cameras? I have been looking at image sensors for my next camera project and an article in the February edition of Photonics Spectra has a good technical summary – see www.photonics.com/spectraHome.aspx .
There are basically 2 fabrication technologies used to build these sensors. These are CMOS and CCD. Both have their benefits, it depends what you are trying to achieve.
CMOS (Complementary Metal Oxide Semiconductor) are the most common type and the one that is still showing volume growth as they are used in the big volume applications like phone cameras, webcams and security cameras. New applications like automotive cameras are also likely to go CMOS. They can also be found in some high end DSLR cameras, notably from Canon. The performance of CMOS sensors seems to be at least equal to CCD for many applications and the ability to make them on established IC fabrication plants, ease of integration with other functions such as image processing and low power requirements make them a great choice in many applications.
CCD (Charge Coupled Device) on the other hand appears to be declining in volume, partly due to substitution by CMOS. However, the technology still moves on and they are often used in high end applications such as medical and scientific imaging. Many models of DSLR have CCD chips such as my Fujifilm S1 Pro.
So what to choose? I have some old CMOS webcams waiting to be used but I hear great things about the Philips webcams. I also have some old CMOS monochrome surveillance cameras lying around. I can feel a head to head comparison coming on – watch this space!

Changes at the UKDL

Off to Cambridge earlier this week for the 2 day UKDL Transistors on Plastic meeting.

For those of you not familiar with the UKDL take a look at the attached picture because it is about to change for a number of reasons. UK Display and Lighting (UKDL – see <http://www.ukdisplay.net/> ) is one of the Knowledge Transfer Network programmes run by the Technology Strategy Board (don’t call them TSB; they get most upset). It has been in existence for a number of years and does a great job in providing meeting around the topics of emerging technologies in Display and Lighting such as printed electronics. I have found them a really customer focussed organisation catering for the needs of their membership (free – well worth it) and their meetings are great networking events. However, the unabbreviated Technology Strategy Board has decided to make some changes. First in the series due later this year is the merger of UKDL with the corresponding Photonics Knowledge Transfer Network. So the content of the illustrated pop-up display will certainly change.

The second change concerns Cathy and Chris Williams, also in the picture. They have chosen not to move with this merger and I wish them well in this.So is this good or bad for the Imaging Science community? Displays and Printed Electronics in general has a lot of congruence with Imaging Science. I would hope that the merger with Photonics will reinforce this. If the new as yet unnamed organisation continues to focus on the needs of our community this could yet be positive. As yet, case unproven.

The Printing and Graphics Science group of the Institute of Physics has had significant collaboration with the UKDL and I hope that this continues through this. I am hopeful as one of our committee members Ric Allottt will be taking over the helm at UKDL. I wish him well and look forward to working with him on this exciting area into the future

Part of the RPS presence at Focus on Imaging 2009

I spent an interesting afternoon at Focus on Imaging this week and once again there was plenty of things of interest.I started with the RPS stand where a talk hosted by PRS President Barry Senior was in full swing. Just up the isle was the usual stand run by the Disabled Photographers Society – see <http://www.disabledphotographers.co.uk/> . I usually find that they are a great place to stop by for second hand equipment. This year I was looking for another digital camera to take apart as I fancy another infrared unit. Unfortunately this year others had beaten me to it and the pickings were thin. Tomas Malloy, one of their trustees and webmaster told me they had a very good few days. Hope to see them back next time.

On the infrared front there were once again some interesting units on the Fuji stand. Maybe next year my budget will extend that far. Also of interest to me was the Lensbaby system as I fancy a play with tilt / shift systems after Andy Finney’s RPS Journal article. Maybe I will have to build my own…

A great show to renew old acquaintances and I look forward to a visit again next year

Lens and sensor in my IR modified Photosmart 215 compact

Off to the Focus on Imaging show tomorrow. My main aim is to look at inkjet technology but I need a new camera bag too.
As always I will be taking a look at the cameras on show. One concern I have is with the seemingly endless use of megapixels as a marketing message – the more the better. A lot of my photography is done at low light levels, either through infrared filters or telescopes at the night sky. In both these cases sharing the same amount of light over more pixels really does not make a lot of sense.
The picture above came from my work on infrared photography. I took apart my old Photosmart compact camera to insert an infrared filter into the optics. That way the camera works as an infrared unit directly out of my pocket without having a comparatively sensitive filter taped to the front.
You will see that the optics are rather small, as is necessary with a compact unit. My preference is for my Fuji Finepix S1 Pro DSLR as I can get some serious optics onto the front, such as a 1200mm f/6 telescope! All this light is only spread over 3.4 MPixels and it works just fine for my applications.
There are however instances where many megapixels are the business and one good example was in the news this weekend – see http://www.timesonline.co.uk/science . The Kepler space telescope is due for launch next month and will carry the biggest ever camera put into space. This has a 95 MPixel sensor but to be fair it does have a 1metre wide optical aperture. Earthbound telescopes can get even bigger. The Large Synoptic Survey Telescope has 3 Bio Pixels. Set that against my 1MPixel compact camera!
So let’s fight the marketing hype of megapixels as a sole metric of camera performance. It is after all what you intend to do with them that counts. And if you see me at Focus with my “lowly” 3.4 MPixels do say Hi.
PS. If you do take a camera apart take care of the voltages associated with the flash unit!

Credit : NASA/JPL/Space Science Institute

One interesting aspect of infrared photography is the ability to penetrate haze. This relies on the fact that light scattering is wavelength dependent with the longer (redder) wavelengths being scattered less.
This technique has long been used in aerial surveillance to get better image contrast. I have also seen wartime pictures taken across the English Channel with infrared sensitised film for the same reason.
This technique is being used to great effect in astronomy and there are some great examples in the February edition of Sky at Night magazine. The example illustrated is an image taken by the Cassini orbiter spacecraft of Saturn’s moon Titan. The image was taken with the Cassini spacecraft narrow-angle camera on Sept. 25, 2008 using a spectral filter sensitive to wavelengths of infrared light centered at 938 nanometers. The view was acquired at a distance of approximately 1.7 million kilometers (1 million miles) from Titan. It was taken in infrared to best penetrate the murky atmosphere of this moon. Equally impressive is the use of infrared to penetrate further into the depths of deep space by establishments such as the European Southern Observatory.
You can find more details of this Titan image under http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=3296 I have tried the same techniques in my infrared photography but with only limited success. Works well for light haze but it is no use in bad visibility and the slanting Northern rain!

A flexo press at Swansea University

There is currently a lot of interest in the use of existing printing techniques to manufacture electronic devices. Conventional impact techniques such as screen and litho printing are already finding applications in this field, as are the newer techniques such as inkjet.
I plan to look at these in a future blog as there is considerable image science needs and interest in this area. It is also a primary focus of the Printing and Graphics Science (PGS) Group of the Institute of Physics, of which I am secretary. We recently held our AGM at Swansea University and took a tour around the facilities at the Welsh Centre for Printing and Coating located there. The image above shows a flexo press with vision systems placed between printing stages to gain experience on printing registration with flexible substrates.
The focus of this article is not how we print but what we print to make electronic devices. There is considerable activity on materials to print conductors and in some fields such as screen printing the material development appears to be relatively mature. However, in order to make active devices the ability to fabricate semiconductors and in particular transistors is key to these products. In particular manufacture onto low cost flexible structures will be important to product development.
I plan to attend a meeting on this topic organised by one of the Knowledge Transfer Networks, the UKDL (United Kingdom Display and Lighting) – see http://www.ukdisplay.net/ . The meeting is entitled “Transistors on Plastics” and is being in Cambridge on the 24th – 25th February add URL. The Printing and Graphics Science Group enjoys close contact with the UKDL and we have organised joint meetings with them.
This is the latest in a series of meetings on this topic. I went along last year and these are great networking events. I hope to see you there but I will also be covering the event in this blog.

Bollington, Cheshire in the Infrared

In Dorset for a few days but the photo opportunities are minimal due to the weather. When I was here over the summer I was playing with infrared photography.
The RPS together with a number of other organisations is involved in the planning for the celebrations of the centenary of infrared photography, aptly named Infrared 100. You can find more details of this on Andy Finney’s web site http://www.atsf.co.uk/ilight/ .
This centenary aroused my interest for a number of reasons. Firstly I had been involved in far red sensitisation for holography and aerial films back in silver halide days. Then I worked on astronomical telescopes for a while where these wavelengths are important for deep sky photography. And finally I like to build things. My PhD is in instrumentation and infrared is a great vehicle to continue with this.
The image above was taken through my unmodified Fujifilm S1 Pro DSLR and comes from a set used in my infrared photography article published in the February 2009 RPS Journal. This article also contains some details of a modified camera. This work continues and I hope to show more here in the future.

Last week I was at a meeting of the committee of the RPS Imaging Science group. In amongst all the hardship within our industry one thing that struck me at this meeting is the value of networking in Imaging Science.
We are a disparate discipline and the varied background of the people around this table was testament to this. We looked into various topics this time but one item on the agenda each time are the meetings we run throughout the year. These are both from within our group but also in collaboration with others, throwing the networking potential wider.
One of the external organisations we discuss is the Society for Imaging Science & Technology, (IS&T). They run a variety of meetings too and you will find reports on a number of these meetings on this web site – see http://www.rps-isg.org/travel_grant_reports.php and http://www.rps-isg.org/events_past.php.
I have just booked my place at the IS&T’s “Technologies for Digital Photo Fulfillment” conference in Las Vegas – see http://www.imaging.org/conferences/tdpf2009/ .Just a 2 day meeting but it also gives the opportunity to visit the Photo Marketing Association convention and trade show, reputed to be the biggest event of its type in the world.
So what’s the interest for Imaging Science? The meeting examines all stages of the workflow from image capture to printed output. I am interested in the real time image processing software being used to enhance images placed online for printing and some of the inkjet printing technology that is being integrated into photo kiosks. Because these are photo applications they need to run at least 6 inks and large, fixed inkjet heads are starting to appear in these units. This sort of technology looks to become a building block for new applications such as printed electronics.
Without meeting like this we will lose the expertise that different disciplines bring to developing topics. So even through these difficult times we hope that you can come and join us for one of our meetings and share your experiences with us. And if not, read all about them on our web site!

The other imaging interest to this story is the amount of image science present in the wide variety of telescopes presently in orbit. Setting aside the high profile (and expense) units like the Hubble Space Telescope there are a large number of earth observing units in use. Because resolution is a function of aperture and launch weight (and therefore cost) is a function of the mass of the primary optic there is a lot of emphasis on the use of sparse apertures in these units. The image science of these is fascinating and it was my pleasure to catch up with progress in this field at the 2006 International Congress of Imaging Science meeting where Robert Fiete of ITT Space Systems presented a paper on this – see http://www.imaging.org/store/epub.cfm?abstrid=33811. They use mirrors with the centres removed or arrays of smaller optics to get resolution without weight but at the expense of some rather odd looking MTF curves. When I get the time I want to build a test unit as it would be fun for my interest in using telescopes for terrestrial imaging. See http://www.rps-isg.org/GP2007/hodgson/telescopes.pdf for some results I presented at a past Imaging Science Group Good Picture event.

Lots in the news this weekend about the implications of the collision between the US Iridium 33 and the Russian Kosmos 2251 satellites. The (remaining) Iridium group of satellites are a fascinating group to watch. They catch the light for a short time as they orbit and when the alignment is right they produce a brilliant flash of light in the night sky. You can find more details on these satellites and an image of an “Iridium flash” under http://www.assa.org.au/observing/iridium/ . As you will see, you don’t need a telescope for this sort of imaging!
I have watched a flash from a dark sky astronomical event in Dalby Forest. I went to see a pre-production version of Iridium in the Smithsonian Aerospace gallery in Washington some years ago and they are surprisingly small objects for their brilliance. I have tried taking an image of an Iridium Flash, so far with no success due to ever present cloud. If you want to find local timings for this event check out http://www.heavens-above.com/ . When I get a picture I will post it here.
The other interesting aspect to this story is that it illustrates the need for monitoring of the increasing levels of space debris. The most likely method of doing this seems to be a network of earth based optical telescopes. This is undoubtedly an opportunity for imaging science both in the acquisition and processing of the imagery. There is still a lot going on in the field of telescope design, an area that I continue to find fascinating – see http://adsabs.harvard.edu/abs/2006SPIE.6267E.133W.