RPS Imaging Science Group

Just got my latest IS&T Reporter. It contains a review of the last Color Imaging Conference – see http://www.imaging.org/ist/publications/reporter/index.cfm . There are some really good papers here so give them a look.

Next year the meeting is in San Antonio. Nice city so I may make it next year!

I was very taken with the visualisation of Centaurus A (see “Sub-millimetre imaging science” yesterday). I now keep seeing the picture popping up everywhere! It was reproduced in the May 2009 edition of BBC Sky at Night magazine – see www.skyatnightmagazine.com , the printed offshoot of the well known BBC television programme. After all these years Patrick Moore is still involved in both enterprises and I was interested to compare the modern magazine with one of the older books from my collection on astronomy – see picture below.

The book, a series of transcripts from the 1959 – 1964 broadcasts was published in 1964. Not a scrap of colour in it and all the (monochrome) photos are in a separate section in the middle of the book. The binding and the pages are all in excellent state with only mild delamination of the cover sheet. The article on Centaurus A has no images and had to describe the then enigmatic object in words.

Sky at Night book and magazine ©Alan Hodgson

45 years on, the magazine is printed in full colour and contains some stunning imagery. Progress in print over the intervening years!

Mid Atlantic on my way to Washington DC. I am reading a paper from J. Imaging Science & Technology on Spectrum based colour imaging technology (JIST 52(1): 010201-010201-15,2008). It is now well established that the use of multispectral imaging (more than the 3 bands used in RGB) significantly improves colour accuracy. This paper purports to present concepts across the entire imaging chain, from capture through to printing and display. The paper is very readable and I would recommended it as a good review but the coverage of printing is a little thin. This is a shame because spectral printing would appear to have the capability of mitigating illuminant metamerism. However one issue that is well covered is the need for adequate profile connection space definition.
One of the attractions for me is the possibility of incorporating spectral data from infrared imaging. In order to make image acquisition work for this technique the spectral sensitivity of the input device must be known. This will include the camera lens, any filters and the image sensor.
One neat use was not truly multispectral as it only needed 3 channels. However these were not the traditional RGB but the reproduction of the faint green, dark red and light pink of the oxygen and nitrogen emission wavelengths in aurora.
Whiled away a couple of hours and distracted me from the rather acid in-flight Chardonnay!

Centaurus A Credit: X-ray: NASA/CXC/CfA/R.Kraft et al.; Submillimeter: MPIfR/ESO/APEX/A.Weiss et al.; Optical: ESO/WFI

As this blog is about Imaging Science (if only a pixel of it) it seemed logical to me that we need some pictures to illustrate this. We then run into the complicated issue of image copyright.
Most of the pictures on this site were taken by me so I gave myself permission to use them. Some of them were commissioned by me from Peter G Crosby of Right Eye Pictures (see http://www.myrighteyepictures.com/).
However, some of the really splendid ones come from hugely complicated and expensive imaging experiments, particularly those concerned with astronomy. Fortunately these are freely available from the various web sites with explicit permission for their use.
For example the European Space Agency makes images available and you can find the copyright issue covered under http://www.esa.int/esaCP/SEMK95VZJND_index_0.html . Likewise the composite Chandra image shown above, available from http://chandra.harvard.edu/photo/2009/cena has similar availability. You will also find statements about Spitzer image rights under http://www.spitzer.caltech.edu/Media/mediaimages/copyright.shtml
These images are made available for non-commercial purposes which fits well with the educational mission of the RPS and this blog. I do take great care to get the image credits right too.
Although these images have great educational purpose they have (for me at least) great artistic qualities. They are also a wonderful example of Visualisation where a difficult concept is demonstrated by an image. In the above case the X-ray image is illustrated in blue, the submillimeter in orange and the optical in “real” colour.
Now that is multispectral imaging!

M82 - NASA/JPL-Caltech/STScI/CXC/UofA/ESA/AURA/JHU

The Spitzer Space telescope is much less well known than the Hubble but is another one of the NASA Great Observatories. Spitzer operates in the infra red and produces some stunning imagery – see http://www.spitzer.caltech.edu/Media/mediaimages/index.shtml . The power of these Great Observatories is best appreciated when they are used in combination as in the image above. The Spitzer, Hubble, and Chandra Great Observatories teamed up to create this multi-wavelength, visualisation of the M82 galaxy from http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=sig06-010 .
X-ray data recorded by Chandra appears in blue; infrared light recorded by Spitzer appears in red; Hubble’s observations of hydrogen emission appear in orange, and the bluest visible light appears in yellow-green.
Unfortunately Spitzer runs out of coolant for the imaging system later this year but hopefully advances in ground based imaging science and technology will take on the task until James Webb gets off the ground. As a result this stunning infra red camera will probably not make it through to the Infra Red 100 celebrations planned for 2010 but the legacy will live on.
This false colour image is a great example of where art meets Imaging Science – the best application of photography!
Credit – NASA/JPL-Caltech/STScI/CXC/UofA/ESA/AURA/JHU

The Geoid - Credit ESA

I think our definition of Imaging Science may be out of date. If you look at our definition written under http://www.rps-isg.org/imaging_science.php it reads as follows.
“If radiation of any kind, emitted from, or affected by an object, causes a representation – the image – of the object or some aspect of the object to be generated, then the systematized body of knowledge relating to the generation, properties and processing of the representation may be defined as Imaging Science.”
It goes on to note that “The term ‘radiation’ also refers to other phenomena in addition to light. The rest of the electromagnetic spectrum can also be included in the definition.” So that lets in the infra red photography featured in this blog too.
We even stretch the definition to cover other forms of radiation. But what about this image? The Geoid is a gravity map of the Earth. This is the type of Imaging Science done by the new GOCE satellite (Gravity Field and Steady-State Ocean Circulation Explorer) just launched by the European Space Agency. GOCE contains a gravity gradiometer which consists of three pairs of identical ultra-sensitive accelerometers, mounted on three mutually orthogonal ‘arms’. So the images are not produced from any form of radiation at all!
You can find more on GOCE plus higher resolution imagery under http://www.esa.int/esaCP/SEMH3NITYRF_index_1.html#subhead2 . Similar imagery is produced by the Japanese SELENE probe around the Moon too. Maybe we should consider extending our definition of Imaging Science!

The Geoid comes under the topic of Visualisation, producing a visual impression of a concept. I hope to return to this topic in the future.