This course provides a framework to evaluate each step in the optical and electronic signal chain of a fluorescent instrument so that you, as system designer, will have the tools to estimate total system improvement or cost optimization. Using a hand-held 'electronic nose' gas detector as an example instrument, this class will show how each stage of the signal chain contributes to noise and signal, and how to evaluate improvements you can make.
Starting at the illumination source, we calculate and measure the noise of the LED and its electronic current source; we estimate the light loss and signal gain through multi-layer optical filters; we estimate the optical performance of the fluorescent sensor polymer and its substrate. We demonstrate the benefits of using non-imaging optics for illumination and light collection, using immersion lenses, and compare Fresnel lenses to simple reflective cones.
Finally, we explain how to estimate the noise of silicon photodiodes when used with transimpedance amplifiers, and how to measure and improve the noise floor of the system's A/D converter.
Anyone who wants answers to these questions will benefit from taking this course:
o Is it worth making a custom lens, or are there other light collection options?
o Is a 16 bit A/D good enough?
o Why do I want more photocurrent - won't that give me more shot noise?
o When is a larger photodiode area a liability?
Since the analysis is based upon a working instrument, we will be able to show you what level of performance can actually be achieved (or expected, during the design phase) - not just what the data sheets might imply.
- identify tradeoffs in fluorescent system design
- summarize how each stage of the signal chain contributes to noise and signal, and how to evaluate improvements you can make
- estimate how transimpedance (current to voltage converter) amplifiers work with photodiodes
- provide a checklist of options for system improvements - optical, mechanical, and electronic - and estimate the performance improvement that is possible
- predict op-amp 'noise gain' and estimate SNR improvements with various photodiodes
- design an optimized fluorescent detection system for your own application