It’s been a while since my last offering here, although our pre-Christmas newsletter did include some material that I might have put here otherwise. But now it’s April again already, which finds me at Plymouth once more – this time accompanied by Linda, with James and Jez due to arrive soon – and right now with some time on my hands as it’s currently a rather wet and miserable Sunday afternoon.
This for us is the “other” Plymouth course, which is still a relative youngster compared with the 30-year history of the autumn Cell Physiology Workshop, but now in its 12th year nonetheless.
But first, a little aside on how we usually get here. Traditionally we have a choice of car or train, and although neither are particularly fast, the train is certainly more relaxing. However, following the severe winter storms, the rail route was still out of action, so a large part of it had been replaced by a bus connection. We had therefore thought we’d end up driving, but a last-minute outbreak of laziness made us decide to try the rail/bus route anyway, and it turned out really not to be too bad after all. But why did we have this problem in the first place? Your blogger’s warped mentality makes him suspect that the trouble stemmed from someone giving his son a very silly name.
Imagine, please, a young lad in the first half of the nineteenth century, attempting to find some form of gainful employment. For many potential positions, things must have had a risk of going something like this:
‘Wotcher mate, nice ta have ya along wiv us! I’m Bill, this is Fred, an’ he be Joe.’
‘Ooo be yoo then?’
‘Ah yes, hello! My name’s Isambard!’
‘ISAMBARD??? Wat sort of prissy name iz that? Ain’t ya got anuvver one we can call ya by?’
‘Oh, of course! You can also call me Kingdom!’
One has the sneaking suspicion that this poor lad would have succumbed to an unexplained industrial accident on his very first day, so many opportunities of gainful employment would therefore have been denied to him. So the young Mr. Brunel, as it indeed was he, had to find alternative ways of making a living.
Before long, he duly managed to become Chief Engineer of the Great Western Railway, where on the whole one has to say that he did a pretty good job. However, his rail link from Exeter to Plymouth was arguably not one of his finest achievements. In the section near Dawlish, the line runs by the sea along the base of some rather attractive red sandstone cliffs, but the problem with this location is that the cliffs look nice and clean because they’re continually crumbling away and the seashore looks nice and clean because it’s regularly battered by periods of bad weather. Turn up the heat just a little bit, as happened over the winter, and suddenly the railway is nice and clean too, but that’s because the cleansing action has left it hanging in midair, making it just a touch difficult to carry trains for a while. This latest repair (it’s happened before!) has been finished while we’ve been down here, so we look forward to checking it out on our return journey.
Going back to the course itself, it’s actually even more relevant to Cairn than the autumn course, as this one is dedicated to advanced optical microscopy, and is organised by Brad Amos, of scanning confocal microscopy fame. On this course I give a lecture on light sources, on aspects of which Cairn was rapidly forced to become expert in order to ensure our personal safety. The issue here was arc lamps, specifically xenon arc lamps, which are a very handy source of intense broad-spectrum illumination, but it turns out that they are also the potential source of a rather less welcome form of radiation.
Since these things had already been around for many decades, there seemed no point in designing our own version, so we began by supplying a third-party product. All was well until our early customers actually got around to switching them on. The light sources worked perfectly, which, unfortunately, was more than now could be said about their patch clamp amplifiers and computers, which were henceforth relegated for use as doorstops, or possibly for being dropped on us from a suitably great height. What had happened?
The issue is this. Xenon is of course one of the noble gas elements, so in order to ionise it in the first place, you have to stick about 50,000 volts across the lamp’s electrodes, hence for a moment or two you’re dealing with a pretty intense electromagnetic field in there. Once the lamp is up and running, the high internal temperature sustains the ionisation, and for the lamps we use you need supply only about 15 volts to keep them going. However, that initial high voltage is a smallscale version of the electromagnetic pulse that accompanies thermonuclear detonations, and so beloved of Hollywood film directors of course. Unfortunately the systems we supplied turned out to be very badly shielded, and it was only by emergency use of cooking foil that we managed to reduce the risk to other nearby electronic equipment, and hence to ourselves, to a more acceptable level. Still, something had to be done for the longer term!
We therefore began by designing our own “igniter” system, as these things are called. Our version was less brutal, properly screened and also was of a “balanced” form to reduce its propagation through earth wiring. Problem solved! Having got that far we thought we might as well provide the rest of the power supply ourselves too, but at the time we weren’t entirely sure of the required characteristics, so we bought in a module from a company that knew about such things. It wasn’t cheap, but the main problem was that it turned out to be amazingly unreliable. There was inevitably some discussion as to whether we weren’t using it properly or they hadn’t designed it properly, but in Cairn we do try to remember that the customer is King, so on this occasion we used the concept to our advantage, by eventually telling them, albeit in an appropriately diplomatic way, where they could shove it.
Since reliability was a key issue that had previously discouraged us from designing our own electronics, we now felt we had nothing to lose, so we decided to have a go ourselves. At this point I’m going to divulge a little trade secret, but so what? Our design is based around a power supply of the mass-produced switchmode type, which is both cheap and reliable. We’ve used several different models over the years, to incorporate the steady design and power improvements made by the manufacturers. The main issue is that arc lamps need to be driven at a constant current (or in our opinion, preferably constant power), rather than at the constant voltage that power supplies traditionally provide, but if you can persuade the manufacturer to part company with a copy of the schematic, it’s actually none too difficult to make the appropriate changes to the regulation circuit. We can also achieve really great stability this way.
The result has been that we have sold literally hundreds of these over the years, and in spite of the increasing popularity of LEDs and affordable lasers, we feel there is always going to be a solid demand for the stable and broad-spectrum output that xenon arc lamps can provide. Our design can drive most mercury arc lamps too, but both their peaky spectral output and generally shorter operating life (not to mention the safety hazards associated with mercury if you manage to break one) mean that in our opinion they are best avoided.
So, it was primarily on this basis that I was invited to give a talk on light sources for this course. However, at the time of my first such talk in 2003, Cairn was already making its first foray into LED-based light sources, and our OptoLED design actually dates from that time. Naturally we’ve made a lot of design enhancements since then, but the main features of optical feedback to stabilise the output, fast analogue level control and even faster digital switching control, were all in there at the start. In fact our main “development” of this product line has been to introduce rather simpler versions for those users who don’t need all those facilities. We were therefore well placed for me to cover LED technology in the talk as well, as well as to take advantage of the increasing commercial use of such sources as the technology continued to improve. The philosophy here has always been that if people were going to prefer LEDs over our arc lamps, they’d better well be our LEDs. Right now we’re selling healthy quantities of both! We’re getting increasingly into lasers too now, with our MultiLine laserbank and its imminently arriving TriLine sibling, but they had to stay at home as we’d got enough other kit here already!
This Plymouth course has also given us the opportunity to demonstrate another LED-based product, namely our new Aura phase contrast illuminator, developed in collaboration with Dr. Kevin Webb at Nottingham, from an idea he had one lunchtime (by which I mean that it’s one of those nice straighforward ideas that make you wonder why it hadn’t been done before). This is a series of concentric rings of LEDs that take the place of the condenser, but which can be mounted much further away, giving you phase illumination but with much better access to the preparation. You just position it at the correct distance and illuminate the appropriate LED ring for that objective. The LEDs can be infrared as well as visible, and although phase contrast isn’t quite as good as DIC, it’s a whole lot simpler and easier to use not to mention much cheaper as you save the cost of the condenser as well as all those funny polarising thingies (I only hope Brad doesn’t read that bit, but I do really know how DIC works, honest!).
Other Cairn goodies on show here include our new Multisplit four-way image splitter, now finally ready for official release. It’s working every bit as well as we had hoped, with nice straightforward user controls for symmetrically varying the horizontal separation, the vertical separation, and the size of the diaphragm aperture that defines the sizes of the individual images. It’s therefore very easily adjustable to match the size of whatever camera sensor you are using, including the larger ones that are now becoming increasingly popular, which can give you megapixel resolution on each of the four images! It also takes the same standard “mirror cubes” used on many of our other products. It’s been a very interesting challenge in three-dimensional design (albeit not quite as interesting as for another product that we aren’t ready to tell everyone about just yet, but that, as they say, will be another story!), but we’re very pleased with the result, and it already looks like this product will have a great future.
The Optoscan monochromator is also putting in its now traditional appearance, coupled, as usual, to the Optosource version of our xenon arc lamp. The Optoscan design dates back from the dim mists of the late 1990s, and although it too has been enhanced over the years, the basics have barely changed. The main improvements have actually been on the lamphouse side of things, to get a better focus of the xenon arc at the monochromator’s input slit in order to optimise the optical throughput. However, there has been another recent development, albeit not a technical one. The main alternative product has been from TILL Photonics, whose Polychrome V monochromator and its predecessors have always provided worthy competition, but TILL has had a number of different owners over the years, and under their latest ownership the decision has been made to concentrate on other areas, so it looks as if this area will be all ours in future! But much as we welcome the increased opportunity, we can’t help but feel a little bit sad to see them go.
- OptoSpin
On the product side of things, I guess we can round things up with our Optospin filter wheel. Unlike just about everything else mentioned so far, our filter wheels have gone through a number of different versions over the years, this one being our fourth, hence its official designation as the Optospin IV, although that is also to indicate that there is a possibility of controlling four wheels at once if you want to. This product can both spin continuously and step rapidly, but its control software (technically firmware as it’s programmed into a processor chip) turned out to be a complete nightmare to develop. We (and in this case it means yours truly) had to play all sorts of tricks to get the performance level that we sought, both to allow multiple wheels to spin in perfect synchrony, and then to step rapidly and smoothly between filter positions. It all took far more time than we’d expected, leaving us with no Cairn product to sell for some years. However, we finally got it into production at the beginning of the year, and sales have taken off much more rapidly than I’d expected. I’m told we’ve got orders for eight on the books at the moment, and that’s for the second batch! We already have support for it in Micromanager, and Molecular Devices are currently writing drivers for their Meta software, with support for Nikon Elements coming along soon, so it looks as if the future sales prospects are going to be very good. And it really does work rather well…. That’s probably more than enough for now, and in any case I now have an urgent business appointment with Kevin Webb in one of the local hostelries (the one that keeps changing its name – see my previous Plymouth blog for that story; sadly the place I recommended there has now closed!!!). The next blog should follow quite soon, and will primarily deal with an upcoming celebration, as well as giving an update on goings-on at the farm, so stay tuned if you dare!
Dr Martin V Thomas – April 5 2014
