CA2197052A1 - High resolution and sensitivity imaging spectrograph - Google Patents

Abstract

A high-resolution, high-throughput imaging echelle spectrograph having a long slit yields high spectral resolution and large spectral coverage simultaneously. The user is able to make quick adjustments of the desired field of view. The overlapping of different spectral orders are separated using a mosaic of interference filters which transmit approximately 50 .ANG. around the selected spectral lines. The spectra recorded by the invention, therefore, are not like any other, where wavelength increases or decreases monotonically along a given direction on an imaging detector. Instead, only selected windows about user selectable spectral regions are recorded simultaneously on the detector.

Description

2~ 9~052 ~G:~ RESOLUTION AND S13:NSITIVITY IMAGIN(~ SPECTROGRAP~l BacL;groutld of the ~ven~on Field of 1he Illven~on The present inven~on ~ene~lly rel~te~ to l~e ~ield of specl~oscopy, and S more specifically relates to a high-rrc~ inn, bigh~ ul ~,~u~h.
Desc~tion ofthe Ba~L~uu.ld Tm~7n~ UovU~ ~s nn ~ol~l tool in s~dying the cn~ros;~ n and charact~ictirs of objects both near and f~ om mi~l~r~bl~ bin1n~cbl and ch~miraI co,,1~uullds7 to the ~'5 ~ ~h~re~ distant stars and g~'l9~i~S. Por 10 the more d~stant objects, a spe~;hOgla~ iS the ~,.ef~1~d meaDs for ~h ~
~eir ~ ~cilinn~ as well as ck7~ ics s7lch as tu~ n1~ , radi~l velocity and mq~n~tic field strellgth. The precision wi~ w~ioh these ll,ea~ ~e~l~ are made ~epP~ c~ to a large extent7 on ~e spectr~l re~olv~inn ~e;hieved by the n~h.
Im~ine speclluscol~y is also used to obtain spectr~ om r~l n~l~d objects, such as eY1.~ .~1 plumes, expanding fireballs, clouds and gpl~riP5 By no~ng c~n~es in 1he ~ecll~scûpic features a~ross an obje~t one can 1ean~ not only the overall ch~--,t~ s of the object, but also the way in which ~ese pJupel(ies change across it S~ecl~uscopes id~ the ç-ri-ct~n~e and/or the locatinnc of individu~l feal~s and a cQII~ct~nn oft-hese f~ . A large field of view is often needed to image l~rge ~ 9, while a smaller field of view is ".~f~l~d to ma~fy de~ils. ~t would be desirable to provide a spccllu~ayll ~at allows the field of view to change without c~pn, .icin~ the resrlll1ion of the ~t F~istin~ sl~e~,ll.J~lls typic~lly consist of a slit, which ~et~ r-s lhe amount of light ~at enters the spectro~raph; a collnn~t~ r lens or mirror, wh~chfocuses the lightrays into parallel be s; a prism or grating, which .l;.~ c and ~e ligb~; ~nd a tclescope or objec~ve lens, which ~lu.luc~s a ~cc~
for visual observation Oc;~ nn~ one or more of the op~c~l cu ~ e.l~ of a ~o~ph are c~...h..-P~l into one multi-purpose co.~ po~e ~1 A photographic cameIa or o~er device may be in~ ld~d to record the ou~t of ~e s~e~lro~r~ph.
When irnaging ~ d sources, the ~hrou~hput of a s~c~v~h sigrifican~ c on Ihe si~ of the slit used in ~e spec~ograph Wavelengll~
5 ~overa~e depends on a given slit's res.nllltion and s~ ilivily. Typically, ~roughput is illc~eased by ~ wider slits. Spe~tral resollltion ~ ., is culll~o~ised by ~e wider slits. Acco,~.gl~, there i-s a need for a system tll~t increases Ihluu~ l while re~ini~ hi~l re~olu~on.
Some s~echug~aphs use echelle ~ gs to ~ G and svyn~ al~ the light.
10 For example, T,P~t~ LabS PS se~ies sp~hull~ete~s use an echelle grating, co...hil-r~ with a pnsm, to d~sper~e ~nd s~ "t; light over two ~1;m~nc;~ns PYicti~ echelle ~ typically have a n 1~ ly coarse line sp~cing (e.g, 3~
150 l/mm) and are blazed atlarge angles (e.g., 60 - 7~~). These ~;,~s are often used at large in~dent angles and ill hig~ diffiaction orders to achieve high 15 dispersion. At a given angle of dil~acLon many wav~ thc will be present c~ h-~lku~cl~ due to order overlap. For a given r~nge of ~ !inn an~es it is possible to have almost all the v~a~le~ om 3sooA to lOOOOA present simultaneously. Fig. I is a plot of dif~action order 100 versus wav- le~ 110.
Notice ~at for v~a~ h~ less than 450û A, ~ere is some overlap 120 (i.e., 20 ~o~e ..a~ ~C ~re ~ ed twice wi~in the dif~action angle). At longer Wtl~ h~ (e.~, greater than 6000 A) gaps 130 in wavc1~,lh CO~ appea~.
As will ~e l1iccuc~ed next, ~ese gaps can be filled in by ~ the ~ngle of ce (e.g.,.vt~ti..g~eg~ 1~.
Figs. 2 (a) and (b) display many specl~l lines of geoph~sical ~ ee 25 indlen~ elo~and~uronL TSel...;,~ 1 axis ofbotll~isthepixelsspace ~10, whe~e light having 10~ o~ h~s been i~aged o~to a 1024 x 1024 array.
Fig. 2(a) is ~e plot of ~a~. l ..UIh~ present an ~e deLe.,lol for the angle of int~ tt DCOI 12to4~2 i~ Fi~ 1. In Fig 2~b)~ ~e angle of ~c~ ~ ia 1~ less t~ ~at of Fig. 2(a). The vertical lines ~ v~ e ~ ;;a~ e of ~ wavele~ at a p~colar pixel of ~he ...) ~e f~rstnumber 220 ~ e~ is ....~ h in ~ngs~oms (A), ~nd tlle number in paren~h~s~s 230 inrli~ the difflac~on order.
S ~ rrine to Figs. 2(a) and (b), note that th~e is no discern~Y.e coITelation L.c;L~een wavelength ~o and the pixel 210 where the ~.a~vle~ h is present.
F~er ~te ~t seve~l wavel~h~ (e.g., 7320 A (24) and 7990 A (22)) ~hat fall into ffle ~s in ~ ~le~,ll, c~e 130 m ~i~. 1 are now ~le~ct~d following the 1 D rota~on ofthe gra~ing, as ev~len~ in Fi~. 2(b). A~ nn~lly~ note that some f~,alulba (e.g., 3371 A in Fig. 2(b)) are present twice but at di~ orders, inllic~ e lhe order overlap ~1;s~ sed earlier.
The spectral lines ~re sv~ c, locat;ed closely tQ~e~er, causmg .r~ an~e~ ,lorastowhichwa~ isbeingdct~ Thisis shown in ~ig. 2~D), where, at app,u,.i~atehy pixel 505, two ~ill~nt wav~ hc of light 15 arepresent Tobrulgthis~ hconfi~ nto~ lelevels,someorde}
sorting technlq~e is ordinalily elnploye~ unu~ typically use a cross disp~b~g rl....rl~ to sep~ PIP ~e vaIiolls orders. Oft~ ~e cross Jisl~e.billg rI~...F.I~t is anoth~ grating. This works ~ell for poin~ sources because ~e input slit is ve~y sho~t, usually ~e sizc of the image of a star (e.g., less th~ S nlm). The 20 rf~nlltunt spec~ogram, ~r cross dispersing, has ml-lt pl~ spec1ra st~cked vertically like n~s ~ a ladder. Similar ~ne~ ~e .~ are used in a~ n--lnir~l rlir ~-inn!c Tbis tPrhniq~e howe~er, does not wo~ he case of an imaei~
s~l.. gr~l~ w~h a long slit where ~e ~mage of the slit fills ~e vert~cl ext~nt of the ~l~it~,clor. Since Gon~ n~l echelle ~ ~uOJ..pbs employ a ~hort slit and 25 have a long focal len~ cnllin~ tl~r, the s1it h~s a s~ll anglllar height. I he ~e of ~e sl~ therefore, occ ~ri~s only a small portion of the ~tP~tor ~ P ~ ir~
to ~e di~l~c.~lo" direction, causing mul~ple images of the slit to be stacked DCn~

~1 ~7052 v~call~. ~e is a need, &er~fcr~, for an i~ that uses the en~e angular field of the ~ r.
One attanpt to address ~is problem has been to limit tlle WaVC~ bl~lldS
the slit. This _ay be done by placing an ~ f~ ce filter wit~ m~lltiple S tr~ncrni~cion ban~c in front of the slit or by havin~ ;yl~ slits, ea;ch with a di~erent filter. The latt~r ~ ;v~ provides ml.ltip~ .es of in~r.r thereb~y providin~ fl~xibility in ~Ju~ g ~e des~ed wave1r~h~ Under ei~er alt~n~tive~ ~the filters must have fa~rly broad (e.g., so-looA) ~ndp3cc , r~ rs becallse of ~e angles encountered The effect of ~ese filters at ~e 10 ima~e plane is to block the u~ d orders and ~llow ~rpically only four or fiveorde~s to be ~ .05e~d Each line, however, has i~s c~u.~ ... plus &e c.~ surr~n~ 11oftheotherlines. In~,u~.~ledpartsofthe l~is is confilsin~ and, in the least, reduces the signal to noise ratio.
Another shul~;v~ of convention~l spect~ogr~phs is that the ~t~ctecl 15 ima{~es are 1~picslly noisy because of the small ~b~ of l~h~ q.~lled. The detected unages may be illL~ d over a long period of ~me to reduce or elimin~te the noise. Yet, for ~pplic~lions that reql~ire high l~ o.~l resolu~on (i.e., high ~$~ inn m a short ~mount of t r le) ~ere is a need for a system that~llows the mtegr~lion ~ be L..v r". ~ed quickly. To have good ~ ~r~ ~snl~ltinh 20 (i.e., ~ tillteg ~iantime)the ~u~hD~sthave high Ih~u~ to be able to record a large llu~b~ of ~holu~ dmillg the ~~ o~ period. ~.Yict1n~
devices fail to provide such ffinr.tif~nolity Addition~lhy, culrent SIJ~G~aphS IJsed f~ a~u..~ -;e~l applications ~ave not been able to achieve a h~h R~-cnl~ r ~ninCSity (~L) product, lC '~31tine 2s instead iII ei~r a ~,~u~aph ~Ivith high l~ hsiL~r, or a s~Lc1~ograph with hi~olv~ power, but not both. For a given ~ng, resolution and h..~.;..r.R:~y are inversely plupo~1ional to ea~ er and are ffinctions of dle slit width and length, D~OI .I~IOU~

as well as ~e charaot~i~i~s of the collimator used. C~ al ~e~usc~pes ~pically ~ade l~l~ninosity for r~cn~ inn or vice versa by c~ pi~ the slit w~d~
andlor bi~ning pL~els on the ~et~ctnr. There is a need for a system that provides both high luminosi~ and high ~solving power, i.e., an ~ t w~th a higb RL
5 product.
Furth~ re, c~ .e.,llu~a~,hs, due to their monotonic wavelength cu~e and limited n~ber of a~ilable pixels, fi~r~ n ei~her as survey in~ ls that cover a large por~on of the wavcl~l~glll (e.g., the en~e visible range) at low resul~t;vn or as i~strumeIIts ~IF~ to a single srec?~l 10 feahlre (e.g., a few A wide) at high cpectrPl resoltltinn (e.g, less li~n 1 A).
However, many applications reql~ire the ~ lr~lus .lleasulclll~t o~ several spec~l ~eab~es ~ ~l wa~l&l~g1L regions at moderate to high resolution.

Su-.. -.y ofthe Inven~on It is therefore an object of the present invention to o~r~o~ ~ese and o~er ~awl~dC]CS of the prior a~t and to provide a s~,e~".apl~ that provides hi~hspectral resolll~ir.n and la~e ~pec~l cove~e ~im~ sl~4!~1y.
lt is another object of the i~;o~ to i~ hlU!~ of a spec~ograph while ~ ~Q~ n It is allother object of the invell~ùn to permit a suffici~t amount of li~ht to enter a s~)e~ osco~ sys~ thereb~ p~oviding fa~t i~ l;on t~me ~nd high signal-to-noise ra~o.
It ~s a fur~er object of the mven~on to simplifi,r ~e co~huction of a spec~ograph.
Tt is a fi~er object of ~e invention to allow the user to easily change ~e field of v~ew of t~e spectrograph.

L~ 7 21 q1052 A ~ d . .ho~ of ~e inven~on is a hi~h-resolulio~, bigh-~oughput i...aei~lg echelle ~yc~u~layll having a long slit. This embo-lim~t yields high spec~al reso!~l~ion and large spectral c..~_...ge s~mult~o~ y. The user is able to ma~e quick adj~ fn~C of the desired field of view. The 5 overlapping of di~erellt spec~al orders are sepal~led using a mosaic of int~f. .~,..ce filters which ~n~ JAi~ 50 A ~rolmd the ~lf cl~ spectr~
lines. The spec~ corded by ~is ~nho~ e not lilce any other ~ec.L~oglaph where wa~elength increases or decreases mnnotQnieally along a given di.~c1io~ ng d~ t~ ctul. lnstEad, only .~. lPCt. .~1 w~ndows about user 10 SPl~rtY~ pec~l re~ions a~e recorded ~ ml~ ~usly on ~e det~ctnr.
~ n another embodiment of tbe in~ention, ~e width of tbe slit is increased,~ereby ~lcl. as,.lg the i~ wll'S lhlv~l~ by ~u~l~dtely a factor of th~ee.
In another Pml-oAi".~,l of me in~ention, a mosaic filter ~it~ a limited number of panels is provided. In ~is Pmho~;...e..l the ~ er of wavP1~.n~hc 15 observed ~ ously is limited, theleby achieving a larger wa~le~
coverage. ~ . .. ; v~ly, a mosaic f;lter havi~g a checkerboard pa~tem of ~tJcrs is used, ~he~eby dividing the ve~tical dim~o.n~inn~ of the sli:t In ano~er embo~ ..f-nl, a comb filter is used to p~ss nl~re l~an one ba~d of ligh~
rn another embo~lim~nt of the inven~on, filters are ...~ ..,t. A on a f~r 20 wheel or slide, enabling user~lefined modes of s~d~.
In another c~ o~iln~ ~-1 of the ~~ ul., a c~plPY ~lescope n~lo~. 5 the field of view, ~us i~ ,&sing the spatial resnlnti. n without d~e-~h~g the u~l~lyu~
In ano~er e -~l~o~ . e ~ of ~e invelltion, a plu~lity of det~ c~ are used 25 for in~n~ine ~e spcctral output Another f .. I.o l;.. ~1 of ~e invention allows the u~ ;lv. e~iccinn fe~..les from any part of ~e visible and near~ d sl,c~ cim~ o~.~ly.

DC01:1210U ~

~1 97052 In an ~lh ~ ;v~ e.lll o~ , the user can m-~nitor ~iccion features from ~y part of the ultraviolet b~ cimlll~n~ollcly. All.,.~ ,ly, ~e user can ~nic~i~m feab res ~om any part of ~he i~an~d spe~ n~o11c1y~
O~er o~ject, adva~tages ~nd embo~ Pntc of the invention are set fort~
S ~n part in the desG~ ;on which follows, and in part will be a~pare~t ~om ~is ~sc~lion o~ ~om pl~lice of the ~nvcn~on.
Brief Des lion of the Dln~s Fig. 1 ill~tes fhe order overlap result~ ~om a pnor alt echelle gra~ng, Fig. 2(a) illu~ ,s lines of geo~hysical ~ n~e in the nieht~ w and 10 aurora ~letect~l bry a prior ut ~cc~ ph prior to order sorting.
Fig. 2(b) illu~l~ ~e lines of geophysical signi~cance in Fig. 2(a) af~er dle incid~nt angle is ch~nE~I1 by 1~.
Fig. 3 is the layout of a pl~f~ d Mnbod; - e,ll of ~e invention.
Fi~. 4(a) illus~tes the S~ WU of Fig. 2(b) as ~l~t~ ry a ~lcL~
15 embo~limpnt of ~e inven~on.
~ ig. 4~b) illus~l~s 1~ ap~c~lu..l of Fig, ~(b) as d~tecte~ by a ~ler~ ,d embo-lim~nt of ~he invention.
De~ tion of the I~,f~,l. d ~ b~
A ~l..f~ Ld embo~imerlt 400 of the present in~rention is ill~h~d in Fig.

3. This t'l~ O~ t 1~ iS generally ~ ""l" ;r A of f~w~tics 500, an op~cics and ~ilte~
mbly 600, a grating box 70n and a ~ clor 800.
I~e ~o~eo~ic~ 500 is eu...U. ;.~ of a ~ lens 510, a slit 520 ~nd a field erLs 530, The optics and filter assembly 600 has a cotli~t~r 610, a f~rst i~ g lens 6~0, a first follling mi~ror 630, a filter 640, a field lens 650, a second foldin~
mirror 660, a second ima~ng lens 670, and a canlera lens ~80. The ~ting box 700 inclu~es an echelle gra~g 710.

DCOI~1210~11 2 21 91~2 T~ ,..t lig~t e~te~s ~rou~h the primaIy le~s 510 l~he pnmary lens 510 focuses ~is light onto the slit 520. The field lens 530 l~di~ec~s the light Lo..d~ds co~or 610. Collimator 610 causes the lightrays to become Fo~ d the rays strike grating 710 wi~ ~n ~ngle of i~ n~e a and are dif3iacted at angle of S dif~action ~. The di~.~ nce b~h ~ the angle of in~ nt a a~d t~e an~le of dif~action ~ is a ~ le, ~. The light rays then travel to first im~in~ lens 620, wbich is preferably placed close t~ t:he gra~g. The first im~ne lens 620 focuses ~e r~ys on t~e fil~r 640.
Folding mirrors 630 ;~d 660 allow the size of ~e dence to be l~d~lced.
10 First foldin~ irror 630 reflects the light onto ~ r~no~rable or .I-t~h.. ~,Able mosaic filter 640. Once the lightrays are filtered by filter 640, they travel Ihrou~
field lens ~50, ~e~ect off,0~second foldin~ mirror 660, and travel to ~cond jm~~ lens 670. The second ;~n~ein~ lellS 670 and camera lens 680 refocus the li~ht rays onto d~,t~,~,tur 8~0. The ~t~ tur 800 may be a CC~ detector or a s~r 15 d~te~ve device.
To get high ~ ugll~ul~ the ~rea~ le product (i.e., Inminocity) is m~ i7r~1. A y~cr~lGd ell.bod; . e ~1 of the inven~on inr.hldes the longest slit possible, 1~e widest sl~t that gives ac~ t~le resolu~on, and the fastest collimato~
d~ can be fillly i~ n~ted ~ the fo~oplics ~at a~e used to select l~e field of 20 view. Preferably, the lenses lhat change ~e field of view of the ~Ln~c,lt ~re al~l 35 mm c~leIa lenses. ~hese lenses can ill~inate ~n a~ u,~ t .ly 40 or ~0 mm long slit with liffle ~ttin~ Odler lenaes tha~ similarly ill.. il~ a long slit with little Vi~ may be used.
1~ one embo~imeTIt, primaIy lens 510 is a 16 mm F/2.~ fisheye lens. The 25 i~ at~d circle is 40 ~ Pt~ with a 30% vi~ , at a field angle of 75~. CollimabDr 610 is ~ to match ~e F-number of the fi~;heye lens. Pecal~ce CK'OI: -, 7 a mirror collim~tnr with this small F-number would not have ~*~ll~te field correction to image the 40 mm long (7.6~) slit, a ~efractiv~ et~,...~ .1 is used.
The u~lla~ of ~Lfr~c,ll spec~l orders are s~ 1 using a mosaic of ~ r~lcnce filt~rs 640. ~ a ~l~rel~ed embo~ nt a mosaic of i~ .r~ ce S filt~s is placed at~e image plane of detector 800. The filter i~ made up of strips of individual filters made for specific wavel~n~hc In Figs. 4 (a) and (b), the result of two mosaic filters are shown in relation to ~e lines that were d~...n~ dted in Fig. 2 (b). The verlic~l dasSed lirles ~ '~l ~e bolm~ s of the filters. The width of each b~J~a~s (e.g ylv~ ~ ly soA Full Wid~h at 10 Half Pow~ WHP)) is wide enough to admit preferably all of the ~
f3~t~ by~e physical width ofthe le~on on ~e ~ tcl~.f ~nd na~ow enough to ~isrrimin~e y~ainst a~jace[lt orders. Pref~ably, the il~Le~l~ce ~ilters Ll~iLonly appro~;..,~t~ly soA around the seleet~d spectral lines.
~f a straight input slit is employed by ~e presellt inventia~ the ability to 15 co-add pLlcels of the CCD plior to readout in t~e vertical direc~on to select t~e spati~l rrsnl hn nlay be co~lolllised. This iS bec~use the image of a straight inpllt slit is curved on th~ CCD due to ~t;em~tism. The amount of c~atu~e is a filn~tinn of the in~j~lPnt ~nd dif~action ~gles ~s well as the angular height ôf ~e slit ~ om the collimat~. To cu y~ .- t~, for this ~ m the im~ge ~0 of ~he slit is cuIved such that a chord u~nn~e!ine the ends of a creeh~l line would be appr~ -c'~ly 1.5 nlm from a l~ne t~mgent to the center of ~e line, This amount of curva~re would m~ke it difficult to use he mosaic filters d~~
above. Acco~J~ly, a preferred e~ af the invcntion uses a curved input slit to null the curva~e of the image. A curved input slit mean~ that thc image 2s projected onto ~e scene by the foreoptics will also be cuIved. The m~
departure is ~ ;,Iably app1o~ ly 5~ for a l 80~ field of ~iew. Such a low IZ1048,2 2 ~ 9~05~

c.u~,al~uG can be used ad~ ageo~y, such as when vie~ away from zeni~ in nosrhf~rir studies.
Wavele~ does not increase or decrease ~ t~!~ically along a g~ven direc~on on ~he ~g detect~r oft~e inven~on. Instead, on~y selectc(l windows S ~bout u~r select~ble spec~al regions are ~corded .~ ;""~ o.~sly on dle det~ct~r.
The loca~on of each ~ he ~lPt~ct~nr has no di~-c~ tle patteln due to the use of .L~e~ ec~1 orde~s for ~ t wav~1~n~th~
~ on ~e number of spec1ral lines and band passes around ~e liIIes selected~ a p..,f~ ,d ~A.,bod~c.lt of ~he invention can record about 10-lS lineswith a~ uA;-~ ly 15-20~ ~reG~l region a~o~nd each at app.~ h l~ 0.4A
recnlnt;nn Peak efficiencies can be as high as 0.8 for some gJ ~ s with a ~WHP of ~ ,ln,~ 10~ cel~tel.,d about ~e blaze direction when ~~aa.u~d in Lit~ow mode. Groove shadowing may occur when the grating is u~ t large 15 incid~nt and dif~n ~les a~ well as when ~ere is a~plO~ ly a 20~ angle beh.-ee~ ~he in~ nt and dif~acted beams. Such shadow~ng may cause about a 15% loss of ~ y when compared to Littrow mode. This loss can be rd by .~Ju~g ~e 20~ angle bct~ ~e input and the ~f~act~,d beams.
Anodler embod~ment of the inver~on resol~es ~is problem by using a gnsm, 20 which is a b~Ctni~c~nn gra~ng on the sur~e of a la~e prism. This allows the grating to bc used in Lit~ow mode and makes it easier to get ~he light from the ends of ~e slitto ill~,...;l.4,~ ~e camera lens with ~ vi~
The m~~ y of the inve~on ~llows for parts to be quiclcly rep~ced or "1~,..1r -.~;. d The ~u,c~tics camera lens may be affllched to tbe device using a ~5 standard 35mm camera ~:u~ ccliu4 thereby p~ ,.,uing the use of a vane~ of lenses, ;...~ ; hl~u~es. The gra~ng box m~y be 1., .u~,d and replaced wi~h a di~erent gra~ng box having ~ cl~ h~ ti~s The filter bo~ may be exch~nged for a ~ l type of fil~r. Finally, the detc tor n-o~lntin~ flange can mm~ tçA one or several det~c~ devices.
The .1il~Pl-cio~c of ~e slit are adjustable. This allows the invention to be operated in at least two modes. When ~he slit is narrow~ ~he de~nce oper~t~
5 high re~ollltinn mode, pro~idi~ a spectral resolu~on on the order of ~ fl~ 0.4 A and a spectral co~elage ranging froTn a~.u~ tely 4,000 to 10,000 A. When the slit width is mcreased, the device ~1)~ s in degl~ded specl:ral rP~ m mode and the throu~hput is pl~r~l~ly increased by appro~L;..,~tely a factor of three ~O~al~d ~vith the i~ment ~e~Li.lg in high 10 resolu~on mode.
Several types of filters ~4~ may be used. In one ~nbo~i~ent of the invention, a mosaic filter with a chec~w~oard pattem is used. This di~ides ~e c~ e of the sli~ and is usefi~l in cases where ~e scene has lit~le or no spatial structure and ~ large number of spectral f~a~ s are being mnnitnred.
In another embodiment of the invention, a non-mosaic Slter having one broad bo~ 7cs is u e~ This emho~;...P I allows a use~ to look at one order.
~ n ~nother em~o~ of the ilIven~on, a comb filter is used. The comb filter is an il~t~r~l~ce filter wi~ m~ ip1e p~s b~nds. I'his ~llows a user to look ~t more ~an one band of li~h~
Other filters directed to a user's ~.. ,f~ cs or needs may also be used.
Moreover, a col~;,.~ion of the above ~Iters may b~e used.
In ano~her ~Tnho~ e ~t of the in~ention, a larger ~ covelage is achieved by ~ ~ the ~u~r of ~. a~ C ob.~ d s~mlll~neously. The fil~s ~re ~ .. t. -l on a filter wbeel or slide, therehy ~Iqhl in~ usels to choose the 25 c~hin~lion of spectral lines for a specific shldy. Since it is physically ~iffi~ t to change fro~ one mosa~c filter to another if ~e filters were actually in closeuxi~ y to the det~ct )r, ~e spec~n is first ima~ed at a conve~ient size (e.g., 2l0~a~

2~ 9~1052 50mm x 50rmn). The fi~ter w~eel is placed at ~e l~ inn w~ere the 5~C~ u iS
jma~d The filtered im~ge is then re imaged down to apJ)l~in~ately 15mm x l~mm square CCD. T~is reduces dle r~nge of aD~es seen by the filter and keeps the cross-over regions ~eh.~,.,n filters as naIrow as p~il,lc.
ThE invention may be used in ~i~glow and auror~l les~h ~om ~e l~ation~l Science Foundation sponsored Polar Cap Obser~ato~y, and ma~ be ~sed for low ~ ~e~ u5copic studies. The invention also ~r be used in a num~erofmedical,en~ PntA1~and in~ applications.
Although the present invention ha~ be~n .1..~.i. ;l.ert in det~il, it should be 10 understood that v~nous r~ gpe~ s~lb~ ul;~ne~ d ~ItP~tione call be made without d~ om the inbended scope as defined by ~e following claims.

210~.2

Claims (21)

1. A high throughput spectroscopy system comprising:
foreoptics for receiving light;
a long slit operatively positioned to receive light from the foreoptics;
a collimator operatively positioned to receive light from the long slit;
a diffractor operatively positioned to receive light from the collimator;
a filter operatively positioned to receive light from the diffractor; and a detector operatively positioned to receive light from the filter.

2. The system of claim 1 wherein the foreoptics includes a field of view selecting device.

3. The system of claim 1 wherein the foreoptics includes a camera lens; and a field lens, wherein the field lens is operatively positioned to receive light from the camera lens.

4. The system of claim 1 wherein the long slit is at least approximately 40 mm in length.

5. The system of claim 1 wherein the long slit is at least approximately 0.040 mm in width.

6. The system of claim 1 wherein the dimensions of the long slit are adjustable.

7. The system of claim 1 wherein the long slit is curved.

8. The system of claim 1 wherein the collimator includes a lens.

9. The system of claim 1 wherein the collimator comprises a mirror.

10. The system of claim 1 wherein the diffractor includes a grating.

11. The system of claim 10 wherein the grating provides high dispersion.

12. The system of claim 10 wherein the grating is an echelle grating.

13. The system of claim 10 wherein the grating is easily replaceable.

14 14. The system of claim 1 wherein the filter includes a mosaic filters.

15. The system of claim 14 wherein the mosaic filter includes a plurality of interference filters.

16. The system of claim 1 wherein the filter includes a bandpass filter.

17. The system of claim 1 wherein the filter includes an interference filter.

18. The system of claim 17 wherein the interference filter includes multiple transmission bands.

19. The system of claim 17 wherein the interference filter is a comb filter.

20. The system of claim 17 wherein the interference filter includes a multiple bandpass filter, wherein the multiple bandpass filter is located in front of thedetector.

21. The system of claim 1 wherein the detector is a CCD detector.