Optics basics: Inverse problems

Posted on October 31, 2008 by skullsinthestars

In previous posts, I’ve talked at some length about computed tomography (CT) and optical coherence tomography (OCT).  Each of these is a technique for determining information about the internal structure of an object, such as the human body, from exterior measurements of the scattering of electromagnetic waves from the object.  In the case of CT, x-rays are used to measure and image a cross-sectional ‘slice’ of the human body, while in OCT, broadband visible light is used to probe a few millimeters into the skin or an internal organ of the human body.

Plenty of other techniques exist for measuring the internal structure of objects, using a variety of different types of waves.  Magnetic resonance imaging (MRI) subjects a patient to an intense magnetic field, and makes an image by measuring the radio waves emitted when the field is suddenly switched.  Ultrasound imaging uses ultrasonic waves to probe the soft tissues of the human body, and is used in mammography.

Each of these techniques is quite different in its range of application, but all require nontrivial mathematical techniques to reconstruct an image from the raw scattered wave data.  These mathematical techniques are broadly grouped into a class of problems known as inverse problems, and I thought it would be worth an optics basics post to discuss inverse problems, their common features, and the challenges in solving them.

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Posted in Invisibility, Optics, Optics basics | 6 Comments

Aaaagh! Attack of the work-week!

Posted on October 30, 2008 by skullsinthestars

Just a brief apology about the lack of science posts this week.  Work has been crazy: on top of trying to catch up on all the class stuff I ignored while I was at the OSA meeting last week, I’ve got all sorts of other things that have come up, including trying to finish a few papers, paying attention to my role on a planning committee for an optics meeting, preparing a grant with colleagues, working on my book, refereeing papers, working on a new review article, supervising student research, and planning a local optics event.  It’s safe to say that I’ve been in ‘optics overload’ this week.

As a side note, it really is amazing how quickly this stuff piles up.  When I started as a faculty member, I just sat around all day planning my class and doing research by myself.  Nice little invitations to help out with projects and join committees started to pop up here and there, and now I’m looking around and realizing that everything needs to get done AT ONCE.  I’m not really complaining, ’cause I love to be busy, but it is quite stunning to me.

I’ll be back in the next couple of days with more detailed optics posts.  I’ve been ILL’ing a bunch of research papers to get background information, and got permission from APS to explicitly use a figure from one of their PRLs (it’s not too difficult to do, by the way).

Awright, back to working on an inverse scattering problem… hmm… inverse scattering… I feel an ‘optics basics’ post coming on…

Posted in Personal | 1 Comment

Bertram Mitford’s The Sign of the Spider

Posted on October 30, 2008 by skullsinthestars

It’s hard to find out information about author Bertram Mitford (1855-1914).  Even Wikipedia doesn’t have information about him, instead redirecting to another Bertram Mitford who wrote about Japan.  He was, like H. Rider Haggard, a writer of adventure stories set in the wilds of Africa, though certainly not as well known (Haggard wrote King Solomon’s Mines and She, the latter of which I’ve blogged about before).  Valancourt Books, which has not led me wrong yet, has been valiantly reprinting much of Mitford’s work.  I decided to give The Sign of the Spider (1896) a read:

signofthespider

I was, quite frankly, blown away.  According to the book notes, Mitford has been dismissed as an imitator of Haggard.  I found The Sign of the Spider to be a much more compelling, and even deep, read than any of the Haggard work I’ve read so far.  A summary and some observations follow.

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Posted in Adventure fiction, Horror | 7 Comments

I voted! Early!

Posted on October 29, 2008 by skullsinthestars

Well, it took 1 1/2 hours, but I got my early voting in!  And I didn’t get tricked by the abysmal design of the NC ballot.

For me, the occasion was chock full of symbolism and happy coincidences.  When I got in line, it was cold out and rather gloomy looking, but by the time I exited the polling place, the sun was shining and warm.  I celebrated my vote (and my car not getting towed where I parked it) by stopping by a nearby Vietnamese restaurant for lunch.  Sitting at the bar, I was just in time to catch CNN’s live coverage of Obama speaking to North Carolina voters.  He may as well have been speaking directly to me at that point (though I didn’t see any starbursts shooting through the screen, alas).

I’m feeling pretty good about this election.  The early voting numbers support my feeling.

Update:  Just to round off this good feeling, I threw a little more money to progressive candidates online: some to Kay Hagan, who’s working to bump out Liddy Dole in NC, and some to Gary Trauner of Wyoming, who is trying to take Dick Cheney’s old seat for the Democrats.

Posted in Personal, Politics | 2 Comments

Halloween Treats, 2008

Posted on October 29, 2008 by skullsinthestars

It’s time for my yearly installment of classic horror stories for some good Halloween chills!  My 2007 edition can be found here.  Happy reading, and Happy Halloween!

The Dead Valley, Ralph Adams Cram.  A man recounts a tale from his childhood, of his stumbling upon a nightmarish valley which threatens both his life and his sanity.

The Valley of Spiders, H.G. Wells.  A valley of a different deadly type!  A pursuit of fugitives turns into a flight for survival against a foe which attacks in an unexpected manner.

The Great God Pan, Arthur Machen.  This one is a classic!  Dr. Raymond is convinced that there exists a world unseen to our ordinary senses.  He performs an operation on his adopted child, Mary, to make her see this hidden domain, but the results are unexpected and horrific.  The story builds tension slowly from multiple points of view.

The Man Who Went Too Far, E.F. Benson.  While we’re talking about Pan, we should take a gander at this E.F. Benson tale.  A man slowly, through isolation and meditation, feels he is on the verge of a breakthrough: complete exposure and harmony with Nature.  But what does ‘harmony’ really mean in the natural world?

The Derelict, William Hope Hodgson.  Hodgson is one of the relatively neglected grandmasters of horror fiction, with a massive œuvre of weird fiction.  Much of his tales match his joint loves of horror and the ocean, and The Derelict is a prime example.  A crew of sailors happen upon an abandoned ship that holds a monstrous and terrible secret.

The Treasure of Abbott Thomas, M.R. James.  A story by a master teller, it combines a treasure-hunt mystery with the horrors of its monstrous guardian.

The Gentleman From America, Michael Arlen.  This one is nearly unclassifiable.  A boisterous American is challenged by some acquaintences to spend the night in a haunted room.  The results are unpredictable and catastrophic.

Posted in Horror | Leave a comment

Letchworth State Park: The panoramas

Posted on October 27, 2008 by skullsinthestars

I mentioned in my post on Letchworth that I had a bunch of panorama photos to put together when I got home, and I’ve done so!  They’re posted below…

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Posted in Travel | Leave a comment

John Wyndham’s The Day of the Triffids (1951)

Posted on October 26, 2008 by skullsinthestars

This continues my brief foray into 1950s/1960s horror/science fiction, which I started with John W. Campbell’s Who Goes There?, which was the source for The Thing From Another World and John Carpenter’s The Thing.  Today let’s talk triffids!  A couple of weeks ago I finished reading John Wyndham’s classic apocalyptic novel, The Day of the Triffids (1951), and I thought I’d share some observations about it and how it relates to the science fiction film of the same name.

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Posted in Horror | 5 Comments

FiO: Day 4 and day 5

Posted on October 24, 2008 by skullsinthestars

Well, I’m home!  A hectic final few days at the FiO conference combined with a lack of hotel internet access prevented me from checking the blog very often (I would wander around the Hyatt, where I wasn’t staying, looking for a place where I could get a signal — and the optimal location always changed).

I attended fewer talks on the last couple of days, in large part because I switched into planning collaborative research projects.  I attended a few special sessions, however: one on the 200 year anniversary of polarization, and one which encompassed the ‘best of topicals’.  I briefly summarize these below.

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Posted in Optics, Science news | 4 Comments

FiO 2008: Day three

Posted on October 23, 2008 by skullsinthestars

All the ‘big ticket’ events took place on the first and second days, so by day 3 I settled into listening to some shorter talks on various subjects.  Also, day 3 is about the time I start trying to actually get some work done and start drifting away from sitting in sessions all day.  I did manage to sit in on a number of talks on plasmonics and metamaterials, and I briefly summarize some of the substance below.

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Posted in Optics, Science news | 4 Comments

FiO 2008: Day two

Posted on October 21, 2008 by skullsinthestars

My hotel’s wireless internet completely crapped out late Sunday night, and they still have not been able to get it fixed.   Fortunately, there’s wireless connectivity in some of the conference center, so I thought I’d post an update while I’m thinking of it.  Being the first ‘real’ day of the conference, there were a lot of distinguished speakers.

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Posted in Optics, Science news | 2 Comments