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Intensity, Homogeneity and Stability
Users of fluorescence microscopy have historically sought as much intensity from their light source as possible in order to overcome the limitations of available Fluorophores and cameras. Much has changed in recent years. More efficient fluorophores have been developed and digital cameras offer increasingly greater sensitivity.
Many demanding investigations now require high levels of accuracy and there are other issues to consider in addition to intensity. Excessive excitation risks photo-bleaching and irrecoverable damage to the sample. Much work now includes comparative and time-course measurements where control over the period of excitation and the stability of that level of excitation become crucial to achieving consistent and meaningful results.
In addition, control, automation, pulsed excitation and lower operating costs make consideration of LED technology and precisExcite® an attractive option. For further information, Fast-switching & Communications
Intensity
Conventional Mercury/Halide lamps provide a broadband of excitation from the UV to the IR. The precisExcite® unit provides discrete excitation at specific wavelength bands. It is not possible to make a direct comparison between the two technologies. Although Mercury/Halide lamps are more intense overall, much of that intensity is at undesired wavelengths and needs to be filtered to protect the sample.
LEDs have their peaks across the spectrum and can be more intense than conventional lamps. Relative intensity is shown below. precisExcite LEDs are actively-cooled for stability and high-intensity.
For example, our standard 465nm array produces approx. 20mW/cm2 output as a collimated 40mm diameter beam entering the microscope.
Homogeneity
The ability to illuminate evenly across the full sample area without constant re-alignment and adjustment means that precisExcite offers consistent quality without regular user intervention. With precisExcite®, it is also possible to adjust the Field of View concentrically - achieving even better homogeneity.
The curves shown below were provided by Olympus who independently assessed the homogeneity by optical microscopy over FOV from digital camera. Results are from bottom left to top right hand corner and from bottom right to top left hand corner and were compared to a "well-aligned" Hg bulb.
precisExcite® homogeneity will never change with time, heating or arc-wander etc.
precisExcite® results show a maximum variation of 7% under a 4x objective.
precisExcite® results show a maximum variation of 9% under a 40x objective.
Stability
To achieve consistent and meaningful results, it is essential that the level of excitation be the same when making measurements and drawing conclusions from the emissions of a fluorescing sample.
CoolLED uses active-cooling of the LEDs to maintain stability of excitation. Intensity is incredibly stable. LED technology is solid-state which results in very little variation over the lifetime of the LED array.
CoolLED guarantees the life of a LAM for a period of three years.
During this time, intensity will remain within 7% of original output. For further information, LAMs and Cost of Ownership
precisExcite® offers true confidence that excitation of your fluorescent sample is stable, consistent and repeatable.
This graph clearly shows the inherent short-term stability and longer life of precisExcite®
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