MMS â Monolithic M i n i a t u re - S p e c t ro m e t e r - Photon Lines

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ControlDiode arrayDiode arr a yThe spectrometer modules of the <strong>MMS</strong>/MCS family a<strong>re</strong> equipped with silicon diodea rrays of the type S3904-256Q or S3904-512Qor even S3904-1024Q from the company Hamamatsu,with 256 – 1024 pixels. Only the <strong>MMS</strong> 1NIR enhanced uses the Hamamatsu Type S 4874-256 Q, which exhibits a higher deg<strong>re</strong>e of sensitivityfor longer wavelengthes (up to 1100 nm). Aspecial housing which is shorter than the standa rd housing permits the detector to be positionedvery closely to the optical input. The smalls p l i t - o ff angle thus obtained <strong>re</strong>sults in optimisedgrating eff i c i e n c y. For this <strong>re</strong>ason, only detectorswith a similarly small housing can be used.Indium-Gallium-Arsenide (InGaAs) diodea rr a y s of diff e <strong>re</strong>nt manufactu<strong>re</strong>rs a<strong>re</strong> used for all<strong>MMS</strong> NIR. However, they a<strong>re</strong> all equipped with aPeltier cooling. Zeiss supplies a matching contro lb o a rd for the control of the Peltier elements.incident light. The information on the amount oflight is gained in the subsequent charging process.The time integral over the charging cur<strong>re</strong> n tis pro p o rtional to the light intensity. Thus, thediode array operates as a so-called – „self-scanning“multiplexer. The individual pixels a<strong>re</strong> <strong>re</strong> a d -out one after the other. The external clock f<strong>re</strong>quencyf determines the f<strong>re</strong>quency for switchingf rom pixel to pixel or, in other words, the timeper pixel t P i x e l . This way, the minimum possibleintegration time t int, min is determined – even in thecase of the Hamamatsu diode arr a y. This alsod e t e rmines the minimum possible integrationtime t int, min .t P i x e l = 1/ft int, min= (N+1) x t P i x e lf m a x = 2 MHz → t i n t ≥ 127 µ s(256 silicon diode arr a y s )f m a x = 2 MHz → t i n t ≥ 64 µ s(128 InGaAs diode arr a y s )The individual N pixels of a diode arr a ywhich <strong>re</strong> p <strong>re</strong>sent capacitors a<strong>re</strong> discharged byThe integration time itself is selected via thetemporal distance of the sequential start pulses.The start pulse triggers the charging process. Theintegration time is <strong>re</strong>alised technically over thetime up to the following start pulse (the timeuntil the following process of selection).16
In the case of InGaAs diode arrays, the situationis slightly mo<strong>re</strong> complex. He<strong>re</strong> the process ofe x p o s u <strong>re</strong> is separated from the process of selection.If the exposu<strong>re</strong> time, i.e. the time duringwhich the diode array is sensitive, can be as shortas <strong>re</strong> q u i <strong>re</strong>d, this <strong>re</strong>sults in a connection for theselection time comparable to the silicon arr a ycell. It is <strong>re</strong>levant for spectroscopy that the detectoris insensitive during the process of selection.Blind periods of up to 3.5 ms need to be takeninto account. (See also Operating Instructions ofthe <strong>MMS</strong> NIR).P <strong>re</strong> a m p l i f i e rThe electronic control of the Hamamatsudiode array is described in the cor<strong>re</strong> s p o n d i n gdata sheet. The installed Zeiss p<strong>re</strong>-amplifier guaranteesa low-noise amplification of the videosignal to 3 V S S . In addition, it converts extern a lTTL levels for the array management to the levels<strong>re</strong> q u i <strong>re</strong>d by the diode arr a y. All InGaAs arrays a<strong>re</strong><strong>re</strong>ad-out with p<strong>re</strong>-amplifiers which supply a voltageof 4 V S S on the diff e <strong>re</strong>ntial amplifier output.C o n t rol electronics for<strong>MMS</strong> family and MCSAll <strong>MMS</strong>/ MCS modules a<strong>re</strong> equipped withp <strong>re</strong>-amplifier electronics. An operating electro n i cis <strong>re</strong> q u i <strong>re</strong>d to control and <strong>re</strong>ad-out of the diodea rr a y, which also executes the transform a t i o nf rom analogue to digital.The deciding factor in this electronic systemis the <strong>re</strong>solution in the intensity axis. Cur<strong>re</strong> n t l y,Zeiss offers operating electronics with a <strong>re</strong> s o l u t i-on of 12, 14 and 16 bit. If the measu<strong>re</strong>ment isc a rried out with the highest <strong>re</strong>solution of 16 bit,this <strong>re</strong>sults in a separation into 65 536 (2 16 ) individualsteps (counts) with a driving ratio of 100 %.It is possible to detect changes of intensity withthis of less than 10 - 4 .17
Page 4 and 5: The quasi-monolithic principleC o n
Page 8 and 9: Back to the basics: The specificati
Page 10 and 11: lf the maximum of a line is imaged
Page 12 and 13: It should be noted here</st
Page 14 and 15: i n s t ructions. Scattere<
Page 18 and 19: ApplicationsThe flexible design of
Page 20 and 21: I n t e rf e rence
Page 22: SpecificationsPast ModulesM o d u l

MMS â Monolithic M i n i a t u re - S p e c t ro m e t e r - Photon Lines

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MMS â Monolithic M i n i a t u re - S p e c t ro m e t e r - Photon Lines