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光学测量基本参数
问几乎任何电气工程师，甚至适度的模拟和电源的专业知识，以评估电源的效率，他或她会知道如何做到这一点，或至少如何开始的过程。你得到一个虚拟负载或（甚至更好）的有源负载，测量电压和电流到电源，测量相同的参数在电源的输出，做一些基本的计算，你有初步的答案。如果需要，在一个输入值和负载范围内运行测试，以及在静态和动态情况下。它可能会有点复杂，但基本的设置和过程有这样做。
现在要求同一个工程师测量光源的效率，如LED或CFL，有很多混乱。为什么？因为测量光学参数带来了一系列新的问题，其中许多问题比基本的电学测量更为复杂和微妙。例如，你想在所有波长的光输出功率，只有可见光谱，或选定的频带（如IR，或在可见光片）？你想要的力量，在所有方向，或只是一个特定的方向和立体角度？
OpTIcal measurements have a very long history， going back hundreds of years. Some of the terms and concepts are unchanged over the years， while some have been updated to SI-based units （InternaTIonal System of Units）， so there is occasional confusion as old and new terms are used， or old terms have been formally redefined （what is a “candlepower” unit， anyway？）。
Before you can get the right instrumentaTIon and set-up， you have to be familiar with basic opTIcal parameters and terminology of photometry （measurement of visible light） and colorimetry （measurement of colors）， so you can be sure you are measuring what you really need to know. Also keep in mind this critical and basic difference between electrical measurements and optical ones： in most cases （but not all， RF is an exception） when you measure electrical power， you measure voltage and current， and then calculate power via analog circuitry or digital processing. However， when you measure optical power， you really are measuring the power itself via a transducer with output voltage or current which has a well-defined correlation to the impinging optical power.
