The Cairn Spectrophotometer System is by far the most versatile
fluorescent measurement equipment available. The design is
modular, allowing a system to
be configured to
the user's
individual needs, or to be changed or extended according to future
requirements. The system is particularly suitable for
dual (or multiple) excitation
measurements, but dual
emission measurements can also be made, using either single-wavelength or
multiple-wavelength excitation. It can be connected to all popular microscopes,
including those made by Nikon, Olympus, Leica and Zeiss, or it can also be used
with our own cuvette holder for cell
suspension measurements. A particularly important feature is the ease with
which it can be interconnected with other equipment. Not only can our system
accept realtime external inputs, but it also provides a full range of
continuously available analogue outputs and synchronisation signals. This means
that you can get started by adding Cairn components to an existing experimental
set-up, whilst retaining the option of extending it to a full Cairn system at
any time in the future.
A key part of our strategy has been to design and manufacture most system components ourselves. We now have our own versions of many items that we used to obtain from other manufacturers, such as light sources and a variety of microscope accessories, and this has enabled us to provide substantially improved performance at lower prices. A particular advantage of this strategy is that we know the equipment inside out, so we can repair it very quickly if it ever does go wrong. We know your experimental time is valuable and we therefore endeavour to provide the very highest levels of service and support, whether you are just an hour or two away or are on the other side of the world.
We are a fully independent Company, and we plough back a significant proportion of our turnover into the design of new products. Not only is our fluorescence system still being extended, but we are also moving into other product areas as the Company grows. Since many customers prefer to obtain as many items as possible from one supplier, in order to ensure that everything works properly together, we have been introducing our own versions of those other items of equipment that are most commonly used in conjunction with our existing range. We are finding that we can generally provide significantly improved versions of such equipment. In 1994 we introduced our flash photolysis system, which is much more compact and generates far less electrical interference than competing equipment, while providing much more versatile control over flash intensity by allowing the reservoir capacitance as well as its charge voltage to be varied. Our patch clamp amplifier includes not one but several novel features. We can also now offer full image analysis systems, as described below.
In spite of our diversification, fluorescence measurement will always form a major part of our activities. Although other options are available (e.g. monochromators) our standard method of fluorescence excitation wavelength selection is made by a rotating wheel which carries a number of optical interference filters. The usual number of filter positions is six, but the system architecture allows wheels with up to eight positions. In 1994 we introduced a second-generation filter wheel with greatly enhanced performance. This wheel can spin continuously at speeds from 3 to over 300 revolutions per second, but can also be driven in a discontinuous mode, switching between filter positions in 30 msec (adjacent filters) to 60msec (opposite filters). For some applications it may be possible to use a plastic rather than a metal wheel, which is almost twice as fast (35msec between opposite filters). You may wish to compare this specification with that of other products.
For photometric applications, continuous spin is the preferred method of operation. The higher sampling rate achieved by this method gives both better time resolution and improved rejection of common-mode interference signals (e.g. light source flicker) when ratiometric measurements are being made. Continuous spinning at low speeds is also suitable for some imaging applications - for example, when the filter-changing rate is synchronised to the video frame rate - but in other imaging applications a longer period at each filter position is required. The discontinuous mode of operation has been provided to support this requirement. The drive electronics includes an interface to allow full control of the filter wheel by other equipment, and for many applications a computer's parallel printer port will provide all the interconnections that are required. A growing number of other manufacturers are supporting the control of the filter wheel via this interface, allowing you to use it in conjunction with their image analysis programs. For a full commercial set-up we can provide a complete system based around our hardware with Axon's Imaging Workbench and proprietary frame grabber.
