Lasers versus LEDs for Bioinstrumentation Laser Advantage No.1 - Spatial Brightness
A laser is a true point source that can be focused to a much brighter spot than a LED. This minimizes the real cost per watt of using a laser source, reduces optical complexity, maximizes the signal to noise, and increases instrument speed.
1. Light Sources for Bioinstrumentation - In any instrument based on the detection of fluorescence and/or light scatter, the key to a successful operation is the ability to maximize the signal-to-noise ratio. This, in turn, is accomplished by delivering the necessary amount of useable excitation light (that is, light that actually excites the fluorescent probe) into the required illumination sample region, while minimizing the amount of wasted light that is of the wrong wavelength or in the wrong spatial location. There are several inherent characteristics of the laser that make it a much more efficient source for accomplishing this task than the LED, resulting in lower instrument costs and superior performance (speed and sensitivity). Here we examine the role of source brightness and its impact on optical etendue and, hence, focused spot intensity, optical efficiency, and optical complexity (i.e., system cost).
2. Laser – a True Point Source - In Bioinstrumentation, the requisite spot size for the optimum operation depends on the type of instrument and then the specifics of the particular model. It can range from tens of microns in diameter to several millimeters in size.