Ratio-recording spectroradiometer
H.K. Hammond, W. Holford, M.L. Kuder · Journal of Research of the National Bureau of Standards Section C Engineering and Instrumentation · 1960
A r a tio-r eco rdi ng sp ectro radio m et er has been const ru cted primarily for deter mining t he relat ive s pect ral irradiance fr om fluor es cen t la m ps in t he v isible spectrum.R a di ant flu x from a tes t sour ce and a com pa rison source is tra ns mitted o r reflected by sep ar ate diffu sers .Th e ir radi ance from each d iffu se r is sampled altern ately of t he o rd er of 100 times a secoJld by a double pris m monochromato r wi t h carn-lin ea ri zed wavelength driv e from 360 to 760 mIL.A 14-stage mu lt iplier phototub e wi t h S-20 r es pon se is u sed wi t h a n electroni c gate a nd integ rato r circui ts to compar e t he spectral irTa di a nces from t he two sources .vVh en t he ph ototube o utp u ts a re un eq ua l, a serv o uni t a dju sts ape r t ures in each beam to eq ua li ze t h em .The measur ed parameter is t he a moun t of ad ju s tm ent r eq uired for eq uali zation at eac h wa velength .The a pertures a re a djus ted by a cam coupl ed to a pen which r eeo rd s t he ratio o n a t hr ee-cycle logarithmic str ip cha r t .Th e instr um ent r equires abo u t 8 m inu t es to record t he s pectrum at 10 mIL p er in ch .An expa nd ed scale ot 1 mIL p er in ch is used for evaluating th e energy in th e sp ectral li nes.Th e speed of wa velengt h scan m ay be made in versely proportion al to t he unbalance sig na l, if d es ired , to provid e a mpl e ti m e to record s pectral lin es acc u rately.Symmet ry of beam t rea,t m ent is dem onstrated by inter ch a ngin g tes t a nd compa riso n so ur ces a nd reco rdi ng t he in verse ratio .