RPS Imaging Science Group

Just found an interesting journal on infrared physics & technology – see http://www.elsevier.com/wps/find/journaldescription.cws_home/525439/description#description . According to the description it convers “theory, experiment, devices and instrumentation”. Looks interesting!

October 7th & 8th 2010, The Royal Astronomical Society, Burlington House, Piccadilly, London W1J 0BQ

In October 1910 Professor Robert Wood presented his paper to the Royal Photographic Society in London  “Photography by Invisible Rays”, describing the use of an infrared plate to make a permanent image in the near infrared. Since that time significant advances have been made in infrared thermal imaging, with applications across a broad spectrum from medicine, industry and astronomy.

Two day seminars, the first on the development and general applications of infrared imaging, and the second on infrared imaging in astronomy will be held in London. The first will be organised under the auspices of The Royal Photographic Society, Imaging Science Group, and the second by the Royal Astronomical Society.

The identification of infrared rays is attributed to Sir William Herschel who presented his findings to the Royal Society in 1800. Sir William became the first president of the Royal Astronomical Society that was founded in 1820. In 2009, the Herschel Space telescope was launched carrying a multi-spectral infrared camera system. Some of the first observational images from this current mission will form part of the second day seminar.

As promised, the report and presentations are now on line – see http://www.rps-isg.org/DF2009_presentations.php .

So which one is it? Surprised me to find it is a European unit, situated on the island of La Palma in the Canaries. It is the Spanish Gran Telescopio Canarias (see http://www.gtc.iac.es/en/ ) and it has a 10.4m aperture made of 36 hexagonal units.
It was officially opened only recently and has a visible wavelength CCD camera at present called OSIRIS. This camera has two 8MPixel CCD units with 15 µm pixels.
A second detector is planned, this time in the mid IR operating from 7 to 20µm (see http://www.gtc.iac.es/en/pages/instrumentation/canaricam.php ). The sensitivity is limited at the low end by the absorption of water vapour in the atmosphere and at the high end by the characteristics of the detector, made of arsenic-doped silicon. It is a Raytheon 320 x 240 pixel array with a pixel size is 50 µm. Normally detectors of this type are cooled using expensive liquid helium. In this case a closed cycle cryogenic unit will cool the detector down to 8K.
So neither camera has what some photographers would call serious megapixels. But take a look at some of the images!

I just received my programme for the IS&T’s 17th Color Imaging Conference. As usual there are a number of papers that look to be of particular interest. In the Interactive paper section there is one from EPFL on materials classification using colour and NIR and on image dynamic range in surface gloss from RIT.

Check out http://www.imaging.org/conferences/cic17/ for more details. The short courses look good too!

Just read an interesting SPIE article on new materials for thermographic imaging in the mid IR. “Superlattices see in the dark” by Manijeh Razeghic DOI: 10.1117/2.1200907.1737 – see http://spie.org/x36271.xml?ArticleID=x36271.
Objects near room temperature emit infrared radiation. These can be picked up and imaged by cameras with suitable detectors. A common material for these detectors at present is mercury cadmium telluride (HgCdTe). These commonly need to be cooled,  lack the uniformity required for large cameras and are expensive.
This work describes the use of type-II indium arsenide (InAs)/gallium antimonide (GaSb) superlattices to replace HgCdTe. The work is illustrated with some human facial imagery taken at 3–5μm and 8–10μm using this type of camera sensor.
Early days but looks promising!

Webcam and driver disc © Right Eye Pictures

I have managed to make it work using the odd combination of an old dual Pentium II motherboard and Windows ME. I look forward to some interesting imaging experiments, perhaps some more IR imaging? The IR filter looks pretty easy to remove and I won’t loose much if I wreck these units!

Some infrared telescope systems are purposefully sited at high altitudes in dry climates. This is because asymmetric molecules such as carbon dioxide and water vapour absorb strongly at some infrared wavelengths. Placing them at these high dry sites maximises the atmospheric windows they can look through.
However, these atmospheric absorptions can be a benefit to other applications. Today I have been looking at MIRTHE (Mid-Infrared Technologies for Health and Environment). Their definition of “mid-infrared” is pretty wide (3 to 27µm) and encompasses the infrared absorptions of many asymmetric atmospheric gas molecules. Amongst other work they use quantum cascade lasers to measure the concentrations of these molecules for air quality monitoring.
Definitely a case of one groups problem being another groups opportunity!

I spent some time considering where to go next with my infrared photography. My plans fall into 3 strands.
1. Get some imaging done with my new Nikon 50mm f/1.4 lens. This should allow me to collect plenty of IR light even though my Fuji S1 Pro DSLR still has an IR filter fitted.
2. More work on the HP Photosmart compact camera. I have a vision of attaching some better optics.
3. I have a small collection of old camera and optics – see image. I plan to convert one of these old 35mm cameras to a DSLR with a basic sensor chip to make my own IR camera. Watch this space!

Most groups within the RPS are primarily concerned with the art of photography. The Imaging Science Group seeks to promote the science of photography too. There is the potential for a gulf between these 2 cultures as outlined 50 years ago by CP Snow in his Rede Lecture at Cambridge (see R P Crease, “Critical Point ‘Two Cultures’ turns 50”, Physics World may 2009 page 19, www.physicsworld.com). The benefit for the RPS of having groups both sides of the potential “cultural divide” is to ensure that we make best use of the contributions from both sides of the debate. Is photography an art or a science – it is both!
On the 50th anniversary of this influential lecture it is fitting to use another anniversary to celebrate this, Infrared 100, the centenary of infrared photography. This blog and the work of the infrared 100 group (http://infrared100.blogspot.com/ ) seeks to show that the art and science of infrared photography can be combined to give some interesting and educational imagery. Truly in the spirit of CP Snow!