光學(xué)測(cè)量基本參數(shù)

　　問(wèn)幾乎任何電氣工程師，甚至適度的模擬和電源的專業(yè)知識(shí)，以評(píng)估電源的效率，他或她會(huì)知道如何做到這一點(diǎn)，或至少如何開(kāi)始的過(guò)程。你得到一個(gè)虛擬負(fù)載或（甚至更好）的有源負(fù)載，測(cè)量電壓和電流到電源，測(cè)量相同的參數(shù)在電源的輸出，做一些基本的計(jì)算，你有初步的答案。如果需要，在一個(gè)輸入值和負(fù)載范圍內(nèi)運(yùn)行測(cè)試，以及在靜態(tài)和動(dòng)態(tài)情況下。它可能會(huì)有點(diǎn)復(fù)雜，但基本的設(shè)置和過(guò)程有這樣做。

　　現(xiàn)在要求同一個(gè)工程師測(cè)量光源的效率，如LED或CFL，有很多混亂。為什么？因?yàn)闇y(cè)量光學(xué)參數(shù)帶來(lái)了一系列新的問(wèn)題，其中許多問(wèn)題比基本的電學(xué)測(cè)量更為復(fù)雜和微妙。例如，你想在所有波長(zhǎng)的光輸出功率，只有可見(jiàn)光譜，或選定的頻帶（如IR，或在可見(jiàn)光片）？你想要的力量，在所有方向，或只是一個(gè)特定的方向和立體角度？

　　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.