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US3748040A - High resolution or high bandwidth monochromator - Google Patents

High resolution or high bandwidth monochromator Download PDF

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Publication number
US3748040A
US3748040A US3748040DA US3748040A US 3748040 A US3748040 A US 3748040A US 3748040D A US3748040D A US 3748040DA US 3748040 A US3748040 A US 3748040A
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slit
intermediate
beam
means
monochromator
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R Hawes
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Cary Instruments
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Cary Instruments
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED, VISIBLE OR ULTRA-VIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02Details
    • G01J3/04Slit arrangements slit adjustment

Abstract

A high resolution or high maximum bandwidth monochromator is provided with certain control means for controlling one jaw of an intermediate slit pair, and other control means for independently controlling the jaws in each pair of entrance, exit and intermediate slits, the monochromator being useful for exploratory research work as well as routine analysis.

Description

United States Patent [1 1 Hawes July 24,1973

HIGHRESOLUTION'OR HIGH BANDWIDTH 2,940,355 6/1960 Cary 356/75 MONOCHROMATOR OTHER PUBLICATIONS [75] Inventor: Roland C. Hawes, Monrovia, Calif. Pierce: McMath Solar Telescope of Km Peak 73] Assignee: Cary Instruments, Monrovia, Calif. tional a ry, pp p VOL 3, 12, Filed: Nov. 1971 December 1964, pages 1,313 741,346 21] A l. No.: 194,7 Primary Examiner-Ronald L. Wibert Assistant Examiner-F. L. Evans v 52 vs. Cl. 356/101 f white Hzfefllger 51 Int. Cl G0lj 3/04, 601 3/18 [58] Field of Search 356/75, 88, 89, 93-101; [57] ABSTRACT 350/271 A high resolution or high maximum bandwidth mono R i d chromator is provided with certain control means for e fences controlling one jaw of an intermediate slit pair,.and UNITED STATES PATENTS other control means for independently controlling the 2,587,451 2/1952 Farrand 350/271 X jaws in each pair of entrance, exit and intermediate 2,698,410 12/1954 M e e a1 356/96 X slits, the monochromator being useful for exploratory v research work as we" as routine analysis 3,414,354 12/1968 Sregler 356/75 3,586,442 Tripp 356/101 10 Claims, 11 DrawingFigures HIGH RESOLUTION OR HIGH BANDWIDTH MONOCHROMATOR BACKGROUND OF THE INVENTION This invention relates generally to spectrophotometry, and more particularly concerns advancements in emission type monochromators used primarily in fluorescence spectrophotometric instrumentation.

In general, there are two characteristically different applications for fluorescence spectrophotometers, such applications imposing quite different demands on the instrumentation. Thus, for exploratory research work, the emission monochromator should be capable of fairly good resolution, say one nm or better, when used to obtain emission spectra; however, when used to obtain excitation spectra or for routine analytical purposes, the monochromator should have the maximum bandwidth consistent with effective exclusion of the exciting radiation, i.e., at least 100 nm. At the same time, the monochromator should haveonly moderate width entrance and exit slits to permit convenient focusing of the optical beams external to the monochromator and entering into and emerging from it.

SUMMARY OF THE INVENTION It is a major object of the invention to provide an emission type monochromator having good resolution for exploratory research work, and also having maxi- A to define successive sections of a double monochromatoroperable to isolate a band of wavelengths with high.

and low limits,

b. beam dispersing means in the beam path between the entrance and intermediate slits and between the inwhich is independently adjustable, as-by a first control,

to, increase and decrease theiwidth of said band by changing only one of the'limits.

In this .regard, only the longwavelength limit of the band is for example adjustable, as by varying the intermediate slit. The widthofthe latter in the case of a monochromator having collimator focal lengths of about 40 centimeters may be controllable between less than one-half and 25 millimeters. Further, the beam typically comprises scattered radiation produced by impingement of sourcemonochromatic radiation upon a sample, in addition-to fluorescent radiation, and the intermediate jaw adjustment is characterized in that ,excitation wavelength radiation scattered from the sample is excluded from passage through the intermediate slit throughout the adjustment. 1

Additional objects and advantages include the symmetrical location of the entrance and exit slit forming means, the beam dispersing means and the beam reflecting means with respect to the intermediate slit to slit; and the employment, as beam reflecting means, of a pair of diagonal mirrors between which the beam is reflected for passage through the intermediate slit, and an optionally usable beam chopper movable in the beam path between the diagonal mirrors.

These and other objects and advantages of the invention, as-well as the details of an illustrative embodiment, will be more fully understood from the following description and drawings, in which:

DRAWING DESCRIPTION DETAILED DESCRIPTION Referring firstto FIGS. 1-3, jaw means includes jaws l0 and 11 defining an entrance'slit S jaws 12 and 13 defining intermediate slit S and jaws l4 and 15 defi'n' ing exit slit 85. Such structure may be considered as defining successive sections of a double monochromator. operable to isolate a bandof wavelengths with high and low limits, 7 i

The illlustrated a multiple slit monochromator further includes .beam reflecting means as for example may take the form of spherical collimating mirror 16, in the beam path between the entrance and exit slits. Also beam dispersing means, as for example single plane grating '17, extends in the beam path between the entrance and interrnediate slits, and'in the beam path between the'intermediate and exit slits. Further, that 'grating is characterized by opposed directions of dispersion in the 'successive' monochromator sections, the first-0f which is associated with'the beam path between S, and S and the second of which is associated with the beam path between S, and S The complete beam path isshown in principleray form as including ray 15a passing from define a double pass monochromator characterized by subtractive ,dispersion; the provision of the beam dis- S, tothe mirror for reflection at 18, ray 15b passing from the mirror to the grating for dispersion, ray',1 5c passing from the grating'to the mirror 16 for reflection at 19, ray, 15d extendingfro m the mirror, to the diagonal Newtonian'mirror N, for, reflection at 20', my 15c extending from mirror N, through "slit S, and'to' di'ag onal Newtonian mirror N, for reflection at 21, my 15f extending from mirror N, to the mirror 16 for'r'eflection as ray 15g returning to the grating 17 and ray 15h extending from the grating to the mirror for reflection as ray 151' passing through slitSg. In this regard, rays 15a 15d, and apart of ray 15 extending from mirror N, to the plane of the intermediate slit 8,, may be considered as first pass rays, while rays which include the 26 (which may be a laser) and passes through optical elements 27 which may include a quarter wave retarder and an electrooptic modulator, as described in copending application Ser. No. 192,815 by Ahmad Abu- Shumays and Jack J. Duffield and entitled Linear Polarization Apparatus For Use In Circular Dichroism Polarimetry. The radiation exiting from the monochromator and shown schematically as ray 15] passes to a photodetector and associated electronics and recording mechanism indicated at 28, and described in US. Pat. No. 3,013,194 to l-LI-I. Cary. A rotating beam chopper 70 proximate slit S, may be used to prevent detection of light scattered toward the exit slit on the first pass through the monochromator, by providing for A.C. detection, as described in US. Pat. No. 2,652,742 to A. Walsh.

In accordance with an important aspect of the invention, one jaw of the intermediate slit S, is made independently adjustable to increase and decrease the width of the transmitted radiation band; and, typically only the long wavelength limit of the band is so adjustable. Referring to FIG.4, control means 29 is operable to simultaneously adjust jaws of all the slits S,, S, and 8,, whereas control means 30 (graduated in nanometers bandwidth) is operable to independently adjust only one jaw of slit 8,. Thus, as seen in FIGS. a and 50, when control 29 is operated, all the slits may be simultaneously widened, with both jaws of each slit moving away from a center line defining a nominal wavelength. Such center lines are indicated at 31-33. In the other hand, when control 30 is operated, and as appears from comparison of FIGS. 5a and 5b, only jaw 13 is moved away from nominal center line 32, all other jaws remaining unmoved. Jaw 12 remains unomved by control 30 so as to exclude exciting radiation throughout the adjustment of jaw 13. The same functioning appears from comparison of FIGS.5c and 5d.

In FIG. 6, the FIG. 5a condition of equal slit widths S, S, S, is further represented by the narrow pass band 32 of scattered fluorescence radiation from a sample, the wavelength of the exciting radiation appearing at 33. When S, is increased in relation to S and S, as in FIG. 5b, the widened pass band for S, appears as at 34 in FIG. 6. Similarly, the FIG. 50 condition of equal and widened slit widths is represented by the band-35; whereas, when S, is increased as in FIG. 5d, the widened pass band for S, appears as at 36, in FIG. .7.

In one representative monochromator embodying the concepts of FIGS. 1-3, the width of the intermediate slit S, is variable from less than one-half mm to about 25mm. The Newtonianmirrors are large enough to accept the 25mm wide beam. To avoid vignetting, it

may be desirable to provide a field lens shown as 65 in FIG. 8 at the intermediate slit, and large enough to accept the full beam when the slit is 25 mm wide. The field lens renders the aperture stops in the successive sections of the monchromator optically conjugate. In the example chosen, the monochromator has 4 nm/mm reciprocal dispersion when the intermediate slit matches the entrance and exit slits in width, or is narrower. Widening the intermediate slit S, increases the bandwidth of the monochromator unsymmetrically with respect to the nominal wavelength, without changing the proportion of stray to accepted light. This assumes a narrow band fluorescence excitation source,

and that the fluorescence is white, or of constant energy, over the bandwidth.

In the modified form of the instrument seen in FIG.

8, separate gratings 40 and 41 are employed in two entirely separate sections of a double monochromator, and at opposite sides of a plane 42 defined by the intermediate slit S,, and usually provided with a mask at or near this plane to prevent radiation from passing from one monochromator section unto the other by any means other than through the slit 8,. Jaw 43 of the intermediate slit forming means is movable relative to jaw 44, by the control as seen at 30 in FIG. 4. Jaws of all slits 3,, S, and S, are simultaneously movable as by the control means 29 of FIG. 4. Note that a beam entering S, is defined by a principle ray 46 between S, and mirror 47, ray 48 between mirror 47 and grating 41, ray 49 between grating 41 and mirror 50, ray 51 reflected from mirror 50 to Newtonian mirror 52, ray 53 reflected from mirror 52 to Newtonian mirror 54 via slit 8,, ray 55 reflected from mirror 54 to mirror 56, ray 57 reflected to grating 40, ray 58 transmitted from the grating to mirror 59, and ray 60 reflected to and through exit slit 8,.

In FIGS. 1-3 and 8, the gratings may be rotated about an axis located approximately in the face" of the grating, and normal to the planes of each of FIGS. 2 and 8, as by the schematically illustrated actuators 61, and 61a and 61b, to control the wavelength of radiation transmitted via the exit slits. The gratings 40 and 41 may, for example, have 600 lines per millimeter, be'oriented to the substractive dispersion configuration, and be mounted on separate, counter-rotatingtables.

A field lens 65 proximate slit S, accepts the full beam when slit 8, has maximum width, as described previously.

In this double monochromator configuration it is'ordinarily not necessary to locate abeam chopper at the intermediate slit, the mask at or near center line 42 being effective to prevent light scattered toward slit S,

on passage through the first monochromator section from reaching S, except such small proportion as may unavoidably accompany beam 53 through slit 8,.

I claim:

1. In a monochromator, the combination comprising a. means forming entrance, intermediate and exit slits to define successive sections of a double monochromator operable to isolate a band of wavelengths with high and low limits, and

b. beam dispersing means in the beam path between the entrance and intermediate slits and between the intennediate and exit slits, and characterized by opposed directions of dispersion in the successive sections, r said intermediate slit forming means including first and second jaws, the first jaw carried to be independently adjustable relative to the second jaw to increase and decrease the width of said band by changing only one of said limits, the entrance and exit slit forming means also including pairs of jaws,

d. first control means connected with said first jaw to control said independent adjustment thereof, and

e. other control means connected with said entrance,

intermediate and exit slit forming means to simultaneously vary the widths of the entrance, intermediate and exit slits independently of the first control means by movement of both jaws of each slit forming means, the connection of the first control means with the first jaw characterized in that said independent adjustment thereof may be made separate from the variation in intermediate slit width effected by said other control means.

2. The combination of claim 1 in which only the long wavelength limit of the band is adjustable by varying the intermediate slit.

3. The combination of claim 1 wherein said intermediate slit width is controllable within a range of from less than one-half millimeter to about 25 millimeters.

4. The combination of claim 1 including a source of exciting monochromatic radiation impinging upon a sample so as to produce scattered radiation, including radiation shifted in wavelength from the wavelength of excitation, said scattered radiation producing said beam.

5. The combination of claim 1 including a field lens proximate said intermediate slit to accept the full beam when the intermediate slit has maximum width.

6. The combination of claim 1 including beam reflecting means in'the beam path between the entrance and exit slits and wherein said entrance and exit slit forming means, said beam-dispersing means and said beam reflecting means are symmetrically located with respect to said intermediate slit to define a double pass 9. The combination of claim 8 wherein said beam refleeting means includes apair of diagonal mirrors between which the beam is reflected for passage through the intermediate slit, and a beam chopper movable in the beam path between said diagonal mirrors.

10. The combination of claim 4 wherein said intermediate jaw adjustment is characterized in that excitation wavelength radiation scattered from said sample isexcluded from passage through the intermediate slit throughout said adjustment.

Claims (10)

1. In a monochromator, the combination comprising a. means forming entrance, intermediate and exit slits to define successive sections of a double monochromator operable to isolate a band of wavelengths with high and low limits, and b. beam dispersing means in the beam path between the entrance and intermediate slits and between the intermediate and exit slits, and characterized by opposed directions of dispersion in the successive sections, c. said intermediate slit forming means including first and second jaws, the first jaw carried to be independently adjustable relative to the second jaw to increase and decrease the width of said band by changing only one of said limits, the entrance and exit slit forming means also including pairs of jaws, d. first control means connected with said first jaw to control said independent adjustment thereof, and e. other control means connected with said entrance, intermediate and exit slit forming means to simultaneously vary the widths of the entrance, intermediate and exit slits independently of the first control means by movement of both jaws of each slit forming means, the connection of the first control means with the first jaw characterized in that said independent adjustment thereof may be made separate from the variation in intermediate slit width effected by said other control means.
2. The combination of claim 1 in which only the long wavelength limit of the band is adjustable by varying the intermediate slit.
3. The combination of claim 1 wherein said intermediate slit width is controllable within a range of from less than one-half millimeter to about 25 millimeters.
4. The combination of claim 1 including a source of exciting monochromatic radiation impinging upon a sample so as to produce scattered radiation, including radiation shifted in wavelength from the wavelength of excitation, said scattered radiation producing said beam.
5. The combination of claim 1 including a field lens proximate said intermediate slit to accept the full beam when the intermediate slit has maximum width.
6. The combination of claim 1 including beam reflecting means in the beam path between the entrance and exit slits and wherein said entrance and exit slit forming means, said beam dispersing means and said beam reflecting means are symmetrically located with respect to said intermediate slit to define a double pass monochromator having subtractive dispersion.
7. The combination of claim 6 wherein said beam dispersing means is defined by separate gratings at opposite sides of a plane dfined by said intermediate slit.
8. The combination of claim 6 wherein said beam dispersing means is defined by a single grating for dispersing the beam before and after beam passage through the intermediate slit.
9. The combination of claim 8 wherein said beam reflecting means includes a pair of diagonal mirrors between which the beam is reflected for passage through the intermediate slit, and a beam chopper movable in the beam path between said diagonal mirrors.
10. The combination of claim 4 wherein said intermediate jaw adjustment is characterized in that excitation wavelength radiation scattered from said sample is excluded from passage through the intermediate slit throughout said adjustment.
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4017185A (en) * 1974-03-22 1977-04-12 Varian Associates Optical arrangements for coupling monochromators with external systems
WO1980000189A1 (en) * 1978-06-23 1980-02-07 Hitachi Ltd Calibratiob system for spectroscopes
US4325634A (en) * 1978-11-02 1982-04-20 Hitachi, Ltd. Slit width calibrator for monochromator
USRE32598E (en) * 1975-12-11 1988-02-09 Feature extraction system for extracting a predetermined feature from a signal
DE19532611A1 (en) * 1994-12-26 1996-07-18 Advantest Corp Difference scattering type double passage monochromator
EP1236981A1 (en) * 2000-10-11 2002-09-04 Acterna Eningen GmbH Optical spectrometer with variable bandwidth
DE10205142A1 (en) * 2002-02-07 2003-08-28 Ges Zur Foerderung Angewandter Optik Optoelektronik Quantenelektronik & Spektroskopie Ev Apparatus and method for wavelength at an echelle spectrometer
US6654119B1 (en) 1999-04-21 2003-11-25 Chromagen, Inc. Scanning spectrophotometer for high throughput fluroescence detection
EP1378734A1 (en) * 2002-07-06 2004-01-07 Acterna Germany GmbH Optical spectrometer with multiple spectral bandwidths

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US2587451A (en) * 1949-03-01 1952-02-26 Farrand Optical Co Inc Slit control for spectroscopic apparatus
US2698410A (en) * 1950-06-15 1954-12-28 Beckman Instruments Inc Information recording and reproducing system
US2940355A (en) * 1956-03-02 1960-06-14 Applied Physics Corp Raman spectrophotometer
US3098408A (en) * 1959-02-11 1963-07-23 Applied Physics Corp Double folded-zeta-configuration monochromator
US3414354A (en) * 1964-10-28 1968-12-03 Perkin Elmer Corp Raman spectrometers
US3586442A (en) * 1968-11-29 1971-06-22 Farrand Optical Co Inc Zero dispersion double monochromator

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2587451A (en) * 1949-03-01 1952-02-26 Farrand Optical Co Inc Slit control for spectroscopic apparatus
US2698410A (en) * 1950-06-15 1954-12-28 Beckman Instruments Inc Information recording and reproducing system
US2940355A (en) * 1956-03-02 1960-06-14 Applied Physics Corp Raman spectrophotometer
US3098408A (en) * 1959-02-11 1963-07-23 Applied Physics Corp Double folded-zeta-configuration monochromator
US3414354A (en) * 1964-10-28 1968-12-03 Perkin Elmer Corp Raman spectrometers
US3586442A (en) * 1968-11-29 1971-06-22 Farrand Optical Co Inc Zero dispersion double monochromator

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Pierce: The McMath Solar Telescope of Kitt Peak National Observatory, Applied Optics, Vol. 3, No. 12, December 1964, pages 1,337 1,346 *

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4017185A (en) * 1974-03-22 1977-04-12 Varian Associates Optical arrangements for coupling monochromators with external systems
USRE32598E (en) * 1975-12-11 1988-02-09 Feature extraction system for extracting a predetermined feature from a signal
WO1980000189A1 (en) * 1978-06-23 1980-02-07 Hitachi Ltd Calibratiob system for spectroscopes
US4325634A (en) * 1978-11-02 1982-04-20 Hitachi, Ltd. Slit width calibrator for monochromator
DE19532611A1 (en) * 1994-12-26 1996-07-18 Advantest Corp Difference scattering type double passage monochromator
DE19532611C2 (en) * 1994-12-26 2001-12-06 Advantest Corp Doppelwegmonochromator in differential dispersion arrangement
US6654119B1 (en) 1999-04-21 2003-11-25 Chromagen, Inc. Scanning spectrophotometer for high throughput fluroescence detection
US20080309933A1 (en) * 1999-04-21 2008-12-18 Aries Associates, Inc. Scanning spectrophotometer for high throughput fluorescence detection
US20080309934A1 (en) * 1999-04-21 2008-12-18 Aries Associates, Inc. Scanning spectrophotometer for high throughput fluorescence detection
EP1236981A1 (en) * 2000-10-11 2002-09-04 Acterna Eningen GmbH Optical spectrometer with variable bandwidth
DE10205142B4 (en) * 2002-02-07 2004-01-15 Gesellschaft zur Förderung angewandter Optik, Optoelektronik, Quantenelektronik und Spektroskopie e.V. Apparatus and method for wavelength at an echelle spectrometer
US20050157293A1 (en) * 2002-02-07 2005-07-21 Stefan Florek Assembly and method for wavelength calibration in an echelle spectrometer
US7215422B2 (en) 2002-02-07 2007-05-08 Gesellschaft zur Förderung der Analytischen Wissenschaften e.V. Assembly and method for wavelength calibration in an echelle spectrometer
DE10205142A1 (en) * 2002-02-07 2003-08-28 Ges Zur Foerderung Angewandter Optik Optoelektronik Quantenelektronik & Spektroskopie Ev Apparatus and method for wavelength at an echelle spectrometer
EP1378734A1 (en) * 2002-07-06 2004-01-07 Acterna Germany GmbH Optical spectrometer with multiple spectral bandwidths

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