C&L Instruments has been awarded a US Patent for 
innovative filter wheel synchronization technology.

We have been awarded a US Patent (Patent No. US 6,429,936, SYNCHRONOUS MULTIWAVELENGTH FLUORESCENCE SYSTEM).  C&L offers the only fluorescence systems which are based on the use of dual synchronous filter wheels.  Our unique technology allows for two filter wheels (excitation and emission) to be precisely phase-synchronized at variable speeds, up to 7500 RPM, allowing continuous measurements at rates up to 1,000 data points per second at eight different wavelengths. Using this approach, our systems offer high light throughput, rapid multiwavelength measurements and the capability to measure the fluorescence from several fluorescent probes.  Thus, our systems are ideal for dual wavelength measurements (i.e., fura-2, indo-1, BCECF, etc.), multiprobe experiments (i.e., FRET, GFP, YFP, CFP, etc.)  and various dye combinations (e.g., simultaneous Ca²⁺ and pH with fura-2 and BCECF).  Please read below to see why our filter wheel approach is better than other existing techniques.  

Page Index
Introduction
Fluorometer Types
Disadvantages of Monochromator-Based Fluorometers
Advantages of Interference Filter-Based Fluorometers
C&L Perfects the Interference Filter Fluorometer

Introduction
The C&L Dye Fluorometer is an innovative multiwavelength fluorometer designed specifically for use with readily available multiwavelength fluorescent dyes. Its unique design offers many significant advantages over fluorometers available from other manufacturers.

Fluorometer Types
The C&L Dye Fluorometer is an interference filter-based fluorometer. Interference filter-based fluorometers use interference filters for excitation and/or emission wavelength selection. This feature distinguishes our fluorometer from others, which are based on the use of monochromators for wavelength selection.  Our filter wheel based systems for illumination can be used for sensitive high speed photometry applications as well as ratio imaging.

Optically, interference filter-based fluorometers are preferable to monochromator-based fluorometers.

Disadvantages of Monochromator-Based Fluorometers
Although monochromators can be tuned to pass any wavelength of light, their optical properties are inferior to that of interference filters. The three major drawbacks of monochromators are:

• "Tailing" - Tailing is the passing of wavelengths near, but outside, the desired bandpass of the monochromator. This dramatically increases the likelihood of excitation energy getting into the detection device. This is especially problematic when a monochromator is used in both the excitation and emission optical paths. This causes an increased signal strength as measured by the detector. This unwanted signal adds to the background fluorescence, which severely limits the sensitivity in detecting low levels of fluorescence.
• Passing of harmonics - Monochromators pass the desired wavelength in addition to the unwanted higher-order harmonics of that wavelength.
• Inefficient - Monochromators operate at narrow apertures and collect less light than interference filters.

Advantages of Interference Filter-Based Fluorometers
The recent advances in interference filter design has placed these optical devices in the forefront of wavelength selective elements. The main advantages of interference filter-based fluorometers are:

• High quality interference filters display transmissions outside the passband of interest of less than 10^-5 %T. This is especially advantageous when measuring the fluorescence of dyes that do not display a large Stoke's shift. As a result, low levels of fluorescence can be detected with a higher signal to noise ratio. For the user, this translates to less noise and the ability to discern smaller changes in the fluorescence of the sample with more accuracy.
• Interference filters have a large light aperture and light throughput, perfect for easy detection of the weakest of signals.
• Interference filters are inexpensive. The C&L Dye Fluorometer uses standard 0.5 inch and 1 inch diameter filters that are widely available. The cost of a filter, which should never need to be replaced, is often less than the cost of the fluorescent probes used in an experiment.

To learn more about the design of interference filters, visit our tutorial page.

C&L Perfects the Interference Filter Fluorometer

• High speed and multiwavelength capability.  The Dye Fluorometer can measure eight separate measurements at eight wavelengths in eight milliseconds and display the data in real time.
• Optical purity in the selection of excitation and emission wavelengths, resulting in very low background signals.
• The ability to use combinations of dual wavelength excitation and dual wavelength emission dyes. Two or more dual wavelength dyes can be monitored in the same experiment.
• Software control of illumination intensity.  Illumination intensity can be precisely varied over a 50-fold range for any wavelength pair.
• Simultaneous acquisition of 8 channels of analog data to collect signals from other instruments. This eliminates the need for collecting other data with secondary recording devices and the difficulty in equating secondary events to changes in fluorescence.
• Low cost of ownership.  Get into multiwavelength, high speed fluorometry for much less than you would pay for less versatile instruments from other manufacturers.