CAIRN RESEARCH LTD

United Kingdom

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Our six position rotary filter changer is designed for use in both photometric and imaging systems. Continuous drive is the best solution for photometric measurements, and rotor speeds from less than 4 to over 200 revolutions per second are possible with our system. The low end of this speed range also allows use with a video camera at normal frame rate. For data acquisition at still lower speeds, two or more consecutive samples can be combined together. This incurs no penalty for photometric measurements (in fact it can be very desirable when differential or ratiometric

measurements are being made), but for camera measurements a longer acquisition time for each frame may be desirable. This is because the frame readout process introduces additional noise in the image, so it may be preferable to acquire single frames over a longer period instead of averaging several individual frames at normal rate. The C104 filter changer combines the benefits of precise continuous operation, with the ability to make rapid discontinuous movements from any filter position to any other. This is of particular benefit in imaging applications where rapid, stepwise filter changes are required but, the time needed for data acquisition may be variable and prolonged. The new assembly is controllable for photometric purposes, directly from switches on the front panel or by computer through our standard interface. Additional interfacing has been catered for, allowing the rotor to be programmed externally for imaging applications, or for use with other third party products. This link can be made via a 16 or 32 bit control bus using a standard 37 way D connector (details on request). A suitable control card and Windows driver DLL's are also available. The benefits of our rotary filter changer are as follows:- Continuous spinning operation at speeds from 3 up to over 200 revs/sec. Rotor speeds selectable via the on board frequency generator, or by direct synchronisation to an external source. The internal frequency generator can operate from 0 - 99.9 Hz or from 0 - 999 Hz, as required. Worst case transition times in discontinuous mode of <80 msec, with transitions between adjacent filters taking under 40 msec. Full control using hardware or software as part of a spectrophotometry system or as a standalone product. Standard 6 position wheel allows simultaneous recording with different dual excitation dyes (e.g. fura-2 and BCECF). Control electronics will support a range of derivatives with different numbers of filters (upto 8) and specifications. The quoted filter changing times are for a combined photometry / imaging assembly; dedicated imaging filter changers can be optimised to attain even more rapid response.
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