US3521960A - Monochromator - Google Patents

Description

July 28, 1970 H. S. NEWCOMER MONOCHROMATOR 5 Sheets-Sheet 1 Filed Jan. 20. 1964 I N VEN TOR HARRY SIDNEY NEWCOMER ATTORNEYS y 3, 1970 H. s. NEWCOMER & 3,521,960

I MONOCHROMATOR Filed Jan. 20. 1964 3 Sheets-Sheet 2 FIG.4

July 28, 1970 H. s. NEWCOMER MONOCHROMATOR 5 Sheets-Sheet 5 Filed Jan. 20. 1964 ATTORN EYS United States Patent 3,521,960 MONOCHROMATOR Harry S. Newcomer, PA). Box 340, Cape May, NJ.

Filed Jan. 20, 1964, Ser. No. 338,761 Int. Cl. G013 3/14, 3/18 US. Cl. 356-101 Claims ABSTRACT OF THE DISCLOSURE These entrance and exit slit units are contained within casings of substantially the same size and configuration removably mounted in and having coupling portions projecting slightly outward from aligned recesses in their respective housing side walls so that removal of one of the slit units from its recess in one of the two side Walls to be abutted enables the remaining adjacent projecting slit unit casing to be seated as a pilot portion in the recess thus vacated, thereby positively and precisely securing the two housings to one another in exactly aligned condition by thus, in effect, keying the one to the other, to form a double monochromator, the slit unit which has not been removed then constituting the intermediate slit of said double monochromator.

The slit adjusting mechanisms of both slit units are simultaneously adjusted by an elongated adjusting member extending from one to the other across the intervening space within the housing at a location spaced vertically away from the paths of the light rays within the housing so as to avoid interference therewith, and wherein said adjusting member can be long enough to project through two such juxtaposed monochromators to simultaneously adjust three slits.

The slit adjusting mechanism includes gearing having aligned input gears, and the elongated adjusting member consists of a rotary shaft or pinion having an operative connection with the input gears of the slit adjusting mechanism in the two slit units, so that rotation of the shaft simultaneously rotates the gearing in these two slit units and simultaneously adjusts the widths of the two slit openings thereof.

The prism turntable is smoothly and precisely rotated to vary the Wave length of the rays emerging from the exit slit by a contact member mounted near the periphery of the turntable and carrying a contact element, such as a ball, engageable with the end of a micrometer screw shaft such as a conventional micrometer head mounted approximately tangentially of the turntable and carrying a spirally-grooved drum bearing the calibrated wave length scale corresponding to the wave length of the rays emerging from the exit slit.

The barrel or nut of the micrometer screw shaft is clamped in the end wall of the monochromator housing and held in an immovable position precisely aligned and positioned with respect to the contact element on the prism turntable.

Where two such monochromators abut one another to form the above-mentioned double monochromator, the arm of the second monochromator is linked by a rigid 3,521,960 Patented July 28, 1970 member with the arm of the first monochromator, so that no cam is needed in the second monochromator because said rigid member passes from one monochromator box to the other through an aperture and tubular coupling in the juxtaposed walls, thereby receiving rotation of the two dispersing units in unison.

In the accompanying drawings:

FIG. 1 is a top plan view, with the top wall or cover plate removed, of a monochromator according to one form of the invention, with the central portion broken away to enable illustartion, with the central portion broken away to enable illustration upon a larger scale, and with the left-hand end wall broken away to disclose the underlying micrometer adjusting screw or micrometer head locating and retaining construction;

FIG. 2 is a vertical section taken along the broken line 22 of FIG. 1, immediately inside the housing side wall containing the exit slit unit;

FIG. 3 is a vertical cross-section taken along the line 33 in FIG. 2, showing details of the prism mounting and turntable construction;

FIG. 4 is a left-hand end elevation of the monochromator shown in FIG. 1, illustrating the means for mounting the wave length micrometer adjusting screw;

FIG. 5 is a top plan view of two monochromators as shown in FIG. 1, placed side by side and coupled to form a double monochromator with a single linear wave length drive and slit width operating pinion;

FIG. 6 is a fragmentary top plan view of the upper left-hand corner portion of FIG. 5, as modified to employ a dispersing prism rather than a diffraction grating; and

FIG. 7 is a top plan view giving the outline of a cam having a contour such as give a linear readout of wave number position for a prism of the monochromator.

Referring to the drawings in detail, FIGS. 1, 2 and 3 show a monochromator, generally designated 10, according to one form of the invention as including a box-like housing structure, generally designated 12, consisting of a bottom 'wall 14 from which rise opposite side walls 16 and 18, a single end wall 20 and a double end wall 22 consisting of outer and inner end walls 24 and 26 respectively separated from one another by spacers 28. Closing the housing structure 12 is a top wall or cover 30 (FIG. 2). The various side and end walls 16, 18 and 20 are bolted or otherwise secured to one another in any suitable way, as by the screws 31 (FIG. 4), the outer and inner end walls 24 and 26 being secured to the side walls 16 and 18 by screws 32 passing through spacers 28 into the ends of the side walls 16 and 18 ,(FIG. 1). A cross member or platform 34 extends between the opposite side walls 16 and 18 near the end of the housing structure 10 opposite the double end wall 22 at a level slightly above the bottom wall 14 (FIG. 3) and is secured to the opposite side walls 16 and 18 by screws 36 and to the end wall 20 by one or more screws 38 (FIG. 4). Alternatively, the box-like housing structure may be of unitary construction, such as a die casting.

The opposite side walls 16 and 18 are provided with small-diameter coupling bores 39 for a purpose to be described later, and with large diameter bores 40 of the same diameters extending inward from the external surface 42 and terminating in bottom surfaces 44 from which an eccentrically-located bore 46 extends inwardly through the remainder of the side walls 16 and 18, the center of the smaller bore 46 being located above the center of the larger bore 40 (FIG. 2). Snugly mounted in the bores 40 in the opposite side walls 16 and 18 are the correspondingly-shaped casings 48 of adjustable entrance and exit slit units, generally designated 58 and 52, respectively, having projecting coupling portions 54 snugly fitting the 3 bores 40. The details of these slit units are beyond the scope of the present invention and are described and claimed in my copending application Ser. No. 338,906 filed Jan. 20, 1964, now US. Pat. No. 3,365,262, issued Jan. 23, 1968 for Adjustable Slit Device for Spectrum- Producing Instruments. Here it is believed sufficient to state that each casing 48 contains a pair of sharp-edged slit jaws 56 movable toward and away from one another to widen or narrow the entrance slit 58 or exit slit 60, both of which are disposed in the planes of the outer surfaces 42 of their respective side walls 16 and 18 (FIG. 1), whichever the case may be. The slit jaws 56 are mounted in rectilinear guideways (not shown) and movable toward and away from one another by an externally-threaded screw, internally conical cam ring and driving gear arrangement (not shown) disclosed in my above-mentioned copending application and operated by a pinion rod 55 and knob 57. Means are provided, as set forth below, for precisely orienting and locating the slit unit with the jaws or slit opening 58, 6t) perpendicular to the axial plane I, R, that is parallel to the prism apex 95.

Mounted in hollow cylindrical blocks 62 secured to the slit mechanism casings 48 in line with the entrance and exit slits 58 and 60 are plane front-aluminized entrance and exit slit mirrors 64 and 66 respectively which because of their form are herein termed prism mirrors. These prism mirrors reflect the incident light rays I and I from the entrance slit 58 to a concave front-aluminized incident beam collimating mirror 68 and the refracted and dispersed rays R and R from a concave front-aluminized refracted beam collimating mirror 70 to the exit slit 60. The mirror 70 is somewhat wider than the mirror 68. The radii of curvatures of the reflecting front surfaces 72 and 74 of the collimating mirrors 68 and 70 are twice the optical lengths of path from their respective slits 58 and 60 by way of their respective mirrors 64 and 66 to their respective centers 76 and 78 in order that collimation of the incident rays shall occur in the collimating mirrro 68 and that the refracted and dispersed rays from the dispersing prism 80 shall be focussed by the collimating mirror 70 upon the exit slit 68.

Each of the collimating mirrors 68 and 70 is of rectangular outline and is mounted in a recess 81 in a channel-shaped cell or mount 82 .(FIG. 2) having threaded holes 84 in the back wall 86 receiving adjusting screws 88 passing through holes 90 in the inner end wall 26 so as to urge the rear wall 86 against the ends of an abutment screw 92 threaded through holes 94 in the inner end wall 26. As a consequence, by adjusting the adjusting screws 88 and abutment screw 92 (FIGS. 1 and 2), the collimating mirrors 68 and 70 may be tilted to their proper inclinations, and brought to a distance from the slit mirrors such that they focus in the slits. Such adjustment is made by first removing the outer end wall 24 by removing the screws 32 and then replacing the end wall 24 after the adjustments have been made, in order to prevent tampering with their adjustments, or other antitampering means, such as sealing, may be provided.

The dispersing prism 80 is of the so-called Littrow type and is of right-angled configuration with an angle at the apex 95 of 30 or thereabouts, having a slant face 96 which performs the refraction, a reflecting altitude face 98 provided with an aluminized or other suitable internal reflecting coating 100, and a base or blind face 102 disposed at right angles to the reflecting face 98. The prism 80, for purposes of simplicity of showing, is illustrated as a single solid prism. It will be understood, however, that an array of multiple prisms may likewise be used, if desired, as disclosed and claimed in my copending application Ser. No. 338,744 filed Jan. 20, 1964, for Multiple Prism Monochromator, now US. Pat. No. 3,428,391, issued Feb. 18, 1969. It will likewise be understood that a plane diffraction grating may be used as an alternative dispersing unit, with its ruled surface in the plane of the Surface 96.

The dispersing prism or grating 81) is mounted upon a plane parallel mounting plate or support 104 (FIGS. 1 and 2). The upper surface 106 of the plate 184 is machined to be precisely flat in order to receive the flat ground lower face 108 of the refracting and dispersing prism (FIG. 2). The face 108 is surfaced to give a prism angle at its apex free from pyramidal error. The upper surface of the plate 104 is recessed in the area 165 beneath the prism to receive bonding material 107 (FIG. 3). The lower surface 110 of the plate 104 is also machined precisely flat to rest upon the similarly precisely-machined flat upper surface 112 of a prism turntable 114 having a vertical bore 116 perpendicular 'to the top surface 112. The bore 116 (FIG. 3) snugly receives a pivot shaft 118, the upper portion 128 of which snugly fits a correspondingly-shaped bore 122 in the prism support or mount 104. The pivot shaft 118 of the turntable 114 is precisely and rotatably mounted in a pair of ball bearing units 117 mounted in annular recesses or counterbores 119 in a vertical bore 121 in the platform 34. This arrangement partially locates and fixes the position of the prism mount or support 104 upon the turntable 114 and its orientation is fixed by screws 124 passing through the plate 104 (FIG. 1) into threaded holes (not shown) in the turntable 114. This arrangement enables the prism 80, which is bonded at 105, 187 to its mounting plate 104, to be removed from, the turntable 114 and replaced by another prism of different material or by a multiple prism array or by other dispersing means, depending upon the task to be performed by the monochromator 10 and the region of the spectrum to be investigated. It will be understood that the prism 80 or prism array may be of any suitable material, such as quartz or glass, according to its suitability for the particular region of the spectrum under study. It will likewise be understood that a plane diffraction grating may be used as an alternative dispersing unit with its ruled face in the plane of the surface 96.

Projecting from the rearward edge of the turntable 114 is an arm 126 (FIG. 1) drilled to receive the hooked inner end of a tension spring 128, the hooked outer end of which is secured to an anchor fastener 130. Mounted on the periphery of the turntable 114 and secured thereto by screws 132 is a contact element 134 having a hardened ball contact tip 136 which may be of hard steel, tungsten carbide or the like to resist wear. Engaging the ball contact tip 136 is the flat inner end 138 of a micrometer screw shaft 140 of a micrometer 142 rotatably mounted in a stationary barrel 141 which is fixedly secured against rotation in a bore 144 in the end wall 20 of the housing structure 12. The micrometer barrel 141 has a flange or seat 143 which precisely locates the end position of the end 138 for any position of the micrometer drum 162.

Clamping of the barrel 141 in the bore 144 is accomplished by means of a clamping screw 146 (FIG. 4) having a smooth shank portion 148 passing through a smooth hole 150 in a corner portion 152 of the end wall 20 separated from the remainder thereof by a radial slot 154 extending downwardly from the bore 144 to the bottom of the end wall 20'. The reduced diameter inner threaded end portion 156 of the clamping screw 146 crosses the slot 154 and enters a threaded hole 158 in the adjacent main portion 160 of the end wall 20. As a consequence, when the clamping screw 146 is tightened by rotating it in a clockwise direction, the end wall portion 152 is pulled toward the main portion 160 of the end wall 21 narrowing the gap or slot 154 and constricting the bore 144 so as to tightly clamp the barrel 141 therein.

Mounted on the outer end of the micrometer screw shaft 140 is a graduated thimble or drum 162 (FIGS. 1 and 2) of the conventional micrometer head 142 rotated by a kneurled integral knob 164 and carrying a graduated circumferential scale 166 registering with an index line and graduated linear scale 168 engraved as is Customary on the micrometer barrel or sleeve 141. The graduated scale 166 may suffice as a wavelength indication by reference to a conversion table or graph to be provided for the dispersion unit in use. The micrometer thimble or drum 162 preferably bears, in addition, a helical groove 167 carrying a wavelength scale 169. The micrometer 142 including the screw shaft 140, barrel 141, thimble or drum 162 and index line and wavelength scale 169 collectively constitute a micrometric adjusting screw device, generally designated 170. A sharp-edged groove follower 172 slidably mounted on a shaft 174 anchored at 176 to the box end 20 serves to index the scale 1 69.

When there is incorporated with the micrometer head device 170 the grooved drum extension 167 bearing the wavelength scale 169, which for a conventional one-inch micrometer head may involve employing as much as or inch movement, or 16 to 20 turns of the drum, there will be a corresponding number of spiral turns on the drum 167, which if it has a 3-inch circumference, will then constitute a wavelength scale 169 as much as 60 inches long.

By my invention for rotating the dispersing unit and indicating its wavelength position, I have provided a camactuated mechanism (FIGS. 1 and 2) direct linear wavelength readout. This includes a flat cam follower arm 178 (FIGS. 2 and 3) rigidly fastened in a groove or channel 180 on the under surface of the plate 104 and centered on the shaft 118 at such a level as to pass forward under the pinion shaft 55 to the right-hand rearward corner of the box 12 a ball contact 182 on the arm 178 bears on a cam 184 there located, so that when the cam is at the position for maximum thrust throw of the arm 178, the dispersing prism or grating 80 is at its maximum wavelength setting. The cam 184 is mounted on a worm gear 186, itself on a shaft 188 journalled in ball bearings 190 and driven by a worm 192 on a shaft 194 which is an extension of a driving micrometer head 196 located and secured by its nut 198 in a bore 200 in the box end 20 just as is the micrometric adjusting screw device 170 at the other corner of the end 20.

The prism driving arm 178 is held against the cam 184 by a spring 202 and is held in plane by a slotted block 204. Prism dispersive units of any material can be used, the correctly-shaped cams 184 and properly oriented arms 178 being supplied therewith. In this possible embodiment, the shaft 194 can be recessed into the end of a micrometer head screw and be small enough and flexible enough to be held by the spring 202, forcing it and the worm 192 into close mesh with the gear 186, thus reducing backlash. Vertical alignment, groove alignment in the gear, can be secured by passing the shaft 194 through another slotted block 206.

If, by way of example, the driving micrometer 196 is a conventional l" micrometer graduated zero to one inch, then in FIG. 1 the cam 184 is so drawn as to be suitable for use in conjunction with the flint prism 80 composed of Schott glass SF12 shown positioned at .410 micron wave length orientation, and the worm gear 186 is a 100-tooth 48 pitch diameter gear driven by a double left-hand thread worm 192. In the design of the cam, allowance has been made for the advance of the micrometer, and the design is such that the micrometer graduation in thousandths of an inch indicate a direct linear readout of the prism wavelength position in fractional microns, the range being from 1.0 micron to 0.4 micron, with the drawing showing a setting equal to .41 micron, the micrometer being at .410 inch, indicated on the linear graduated scale 208 of the barrel 210 and the circumferential graduated scale 212 on the micrometer thimble or drum 214.

As is well known, the wave number settings for a prism approach linearity and consequently the difficulty of constructing a cam for wavelength determination where the dispersion of the prism is increasing rapidly and the attack angle is steep can be avoided if recourse is had to a readout in terms of wave number determination. FIG. 7

shows the outline 221 of a cam 220 with center 188 such as could be substituted for the cam 184 in FIG. 1 to give a correct orientation of a prism of fused silica, the cam being positioned by a micrometer 196 as shown in FIG. 1, a shaft 194, a worm 192 and worm gear 186 which in this case is a quadruple thread right-hand 48 pitch tooth gear, the wave numbers being read directly on the micrometer for a range of 1650 angstrorn units to 25,000 angstrorn units, that is, from a setting of .606" to .040" on the readout device 224, wave numbers 60.6 to 4. 10 cm.

The arm 178, the cam 184 and the worm and gear 192 and 186 and the driving micrometer 196- generally constitute a direct linear wave length readout device, designated 224. It is apparent that when using the direct linear wave length readout device 224, the turntable contact readout device 170 would be withdrawn or otherwise retracted out of the way, and vice versa. Micrometer barrel positions on either side are obviously available to make either one of the other readout device inoperable.

In the operation of the monochromator 10 of the present invention, let it be assumed that the refracting and dispersing prism or prism array 80 or other dispersing unit has been mounted on its mounting plate 104, a cam arm 178 correctly oriented and attached thereto, the bore 122 of the plate 104 superimposed upon the projecting top portion of the turntable pivot shaft 118 and that the screws 124 have properly oriented and secured the mounting plate 104 to the turntable 114 in the manner described above. Let it also be assumed that the collimating mirrors 68 and 70 have been tilted to their proper positions by adjusting the adjusting screws 88 and abutment screws 92 as described above, and that the slit jaws 56 have been adjusted to provide the proper and desired widths of the entrance and exit slits 58 and 60.

A suitable conventional light source and optical condensing system (not shown) is arranged to project light upon the entrance slit 58 of the entrance slit device 50 (FIG. 1). Rays passing through the entrance slit 58 are reflected at the entrance slit prism mirror 64 and pass in the general direction of their principal incident ray I to the incident collimating mirror '68, whence they are re flected at the reflecting surface 72 in the direction of the incident collimated principal ray I to the refracting face 96 of the prism 80. There the rays are refracted, dispersed, reflected and refracted and dispersed again. The dispersed rays travel along the path of the principal refracted ray R, are reflected at the reflecting surface 74 of the refracted ray collimating mirror 70 and thence proceed along the refracted principal ray path R to reflection at the exit slit prism mirror 66 and focussing at the exit slit 60, whence they pass into the subsequent apparatus served by the monochromator 10.

By rotating the drum 162 of the micrometric screw device 170, the optrator consequently rotates the micrometric screw shaft so as to move its inner end 138 inward or outward so as to push against and move the ball contact tip 136 tangentially of and with the turntable 114. This action rotates the turntable 114 around its pivot shaft 118, thereby turning the refracting and dispersing prism 80 or other such unit so as to bring rays of dilferent wave lengths to and through the exit slit 60'. If the grad uated scale 169' is graduated in terms of wavelengths, the operator can set the desired wavelength for the emergent light from the exit slit 60 on the scale 169 in registry with the index follower 172, whereupon the light of the desired wavelength will pass through the exit slit 60 if the foregoing adjustments have been properly made.

Simultaneously, the slit widths 58 and 60 can be moved or changed in unison by means of the pinion shaft 55, at least one end of which projects through and beyond the face of the slit units 50 or 52 to make it accessible at the knob 57. The mechanism by which this slit jaw movement is secured through rotation of the pinion is described in my copending application, Ser. No. 338,906,

7 now US. Pat. No. 3,365,262, issued Jan. 23, 1968, mentioned above.

If, instead of the micrometer screw device 170, use is made of the linear wavelength readout device 224, then the prism or other dispersive unit 80 on the turntable 114 is turned by virtue of the cam profile 184 to translate wavelength orientation to direct readout on the linearly spaced divisions 208, 212 of the driving micrometer 196. Moreover, each dispersive unit 80 alternatively supplied for the instrument can be provided with a prepositioned arm 178 and cam 184 with profile such that such direct readout always occurs. Also, it is now possible to assemble two monochromators 10, as above described, side by side, with one intermediate slit mechanism 50 or 52 removed and the projecting coupling portion 54 of the other piloting in the opposite bore 40 in the adjacent side wall 16 or 18 at such assembly. The readout device 224, except for the arm 178, can be omitted from the second unit and instead one can couple the two cam arms 178 by a rigid bar as described below.

In particular, the modified double monochromator, generally designated 280 shown in FIG. includes a first monochromator 300 similar in principle to the monochromator of FIG. 1 and coupled in the above manner to a second monochromator 408 mounted beside it. To avoid needless repetition, parts of the double monochromator 280 similar or corresponding to those of the monochromator 10 employ the same last two digits in their reference numerals. Thus, 352 is the exit slit device of the unit 300 pilotly engaging the bore 440 of the second monochloromator unit 400. 380 is a dispersing unit, by way of example a diffraction grating for which may be substituted a quartz prism 377 (FIG. 6). The grating 380 is mounted on a plate 304 which itself is secured by locating screws 324 to a turntable 314. The turntable 314 is loosely and rotatably mounted upon a vertical shaft 318 supported in bearings similar to those supporting the shaft 118 in FIG. 1. Keyed or otherwise drivingly secured to the shaft 318 is a worm Wheel 385 which in turn meshes with a worm 383 drivingly secured to a shaft 394 operatively connected to a micrometer head 396 including a stationary barrel 410 carrying linear graduations 408 and a thimble 414 carrying circumferential graduations 412. The turntable 314 and worm wheel 385 are drilled and threaded peripherally to receive a coupling screw 387 by which the two may be coupled in driving relationship with one another or, when the screw 387 is unscrewed, released from such driving relationship to permit the turntable 314 to pivot freely upon the shaft 318.

Also loosely and rotatably mounted upon the shaft 318 below the turntable 314 and above the worm wheel 385 is a cam follower arm or driving arm 378. The turntable 314 and arm 378 are also drilled and threaded to receive a coupling screw 381 by which the two may be drivingly interconnected or, when the screw 381 is unscrewed, made movable independently of one another. The outer or free end of the cam follower arm 378 carries a contact ball 382 which engages the peripheral edge 379 of a cam 384. The cam 384 is keyed or otherwise drivingly secured to a vertical shaft 388 which is also journaled in antifriction bearings (not shown) similar to the antifriction bearings 117 of FIG. 1.

Also keyed or other wise drivingly secured to the shaft 388 is a quadrant worm wheel 386 which meshes with a worm 392 also keyed or otherwise drivingly secured to the shaft 394. The worms 383 and 392 are maintained in constant mesh with their respective worm wheels 385 and 386 by a tension spring 389 in a manner similar to the spring 202 of FIG. 1 and similarly guided and supported by a slotted block 304 secured to the side wall 416. In this manner, the wavelength setting of the grating 380, which. may be one of 30,000 lines to the inch, is linearly controlled by the micrometer head 396 through the driving connection of the shaft 394, worm 383, worm wheel 385 and coupling screws 387, the arm 378 being disconnected from the turntable 314 at this time by unscrewing the coupling screw 381.

If, on the other hand, the grating 380 is replaced by a dispersing prism 377 as shown in FIG. 6, the coupling screw 387 is unscrewed to release the turntable 314 from the worm wheel 385 and the coupling screw 381 is engaged with the arm 378 to cause turning of the turntable 314 by the earn 384 and arm 378, as described below. This is also linearly controlled by the micrometer head 396 through its driving connection by way of the shaft 394, worm 392 and quadrant worm wheel 386. If the prism 377, for example, is a fused silica prism, then the cam 384 will drive it through the wavelength range of to 500 millimicrons. Instead of the solid prism 377 of FIG. 6, a prism array of fused silica prisms may be usefully employed in this same wavelength range, such a prism array being disclosed and claimed in my copending application Ser. No. 338,744, filed Jan. 20, 1964, now US. Pat. No. 3,428,291, issued Feb. 18, 1969.

In FIG. 5, a similar prism or prism array 480 is similarly positioned upon a supporting plate 404 which in turn is secured by locating screws 424 to a turntable 414 similarly loosely and pivotally mounted on a verticallyjournaled shaft 418 in a second monochromator 400. A driving arm 478 is also pivotally mounted on the shaft 418 and coupled to the turntable 414 by a coupling screw 481. Alternatively, the turntable 414 and driving arm 478 may be keyed or otherwise drivingly secured to the vertical shaft 418 where the turntable 414 is not to be driven by a worm and worm wheel, as in the case of the turntable 314 of the monochromator 300. The outer or free ends of the driving arms 378 and 478 are pivotally interconnected by a rigid connecting rod 500 so that the driving arm 478 is, in effect, a slave arm operated by the master arm 378 in accordance with the motion transmitted to the master arm 378 by the periphery 379 of the cam 384. In this manner, the two monochromators 300 and 400 are operable in unison by the micrometer head 396 and no other drive is needed in the monochromator 400. In FIG. 5, the positions of the grating 380 and prism 480 correspond to their l70-millimicron wavelength positions, which are also those of the solid line positions of the arms 378 and 478 and connecting rod 500. The dotted line positions thereof correspond to the 500 millimicron wavelength setting of this double monochromator. In this example of the wave length drive for the double monochromator, the gear 386 is a 48 pitch quadrauple left-hand thread worm wheel of 200 teeth whereas the gear 385 is a left-hand doublethread worm wheel of 300 teeth.

With the diffraction grating 380 in the monochromator 300, the direction of light path has been so chosen and indicated by arrows as to make the entrance slit the slit 460 in the outer side wall 518 of the second monochromator 400 (FIG. 5) and the exit slit at 358 in the outer side wall 416 of the first monochromator 300', the light exiting there after final dispersion by the diffraction grating 380. This simple conjuctive arrangement of the two monochromators 300 and 400 provides a double monochromator 280 with several possible choices of pairs of dispersive units chosen from diffraction gratings, solid prisms or prism arrays will be obvious to those skilled in this art, as imparting a flexibility to the instrument.

Where the two monochromators 300 and 400 are ioined to one another to constitute a double monochromator 280 as described above, the slit mechanisms 358, 352 and 452 are operated simultaneously and in unison by a single elongated pinion shaft 355 which spans the interiors of both monochromators 300 and 400, and which is substituted for the shorter individual pinion shaft 55 shown in FIG. 1. Alternatively, for some purposes, a narrow fixed slit 360 can be substituted for the adjustable intermediate slit device 352.

In the double monochromator 280, accurate alignment of the first and second monochromators 300 and 400 is accomplished by an end-threaded coupling sleeve 502 extending through and snugly fitting aligned counterbored holes 506 and 508 (FIG. with nuts 504 threaded onto the opposite ends of the sleeve 502. The sleeve 502 and holes 506 and 508 are so located as to provide a free passageway for the connecting rod 500, the nuts 504 being contained in the counterbores of the holes 506 and 508. In addition, as previously stated, the two monochromators 300 and 400 are precisely aligned by the engagement of the housing 348 of the intermediate adjustable slit device 352 in the bore 440 of the inner side wall 516 of the second monochromator 400, the threaded sleeve 502 and nut 504 locking this assembly together in piloted aligned relationship.

In the operation of the double monochromator 280, light entering the entrance slit opening 460 of the slit device 452 is reflected off the front-aluminized prism mirror 466 to the collimating mirror 470 where it is reflected to the dispersing prism 480. There it is dispersed and emerges in a light path leading to the collimating mirror 468, whence it is reflected off the front-aluminized mirror prism 464 through the intermediate slit opening 360 off the front-aluminized prism mirror 366 to the collimating mirror 370. There it is reflected in a path leading to the diffraction grating 380 (or prism 377 of FIG. 6 or prism array, if used) and after dispersion proceeds to the collimating mirror 368 where it is reflected to a light path leading to the front-aluminized prism mirror 364 and thence out to the exit slit opening 358 of the exit slit device 350. The operation of the micrometer head 396 as a linear readout device for either the diffraction grating 380 of FIG. 5 or the solid prism 377 of FIG. 6 is believed self-evident from the description of their construction above, and hence requires no repetition.

Where, in the double monochromator 280 there is an advantage in employing a difiraction grating 380 in the first monochromator 300 to accomplish the final dispersion, then the slit opening 358 of the slit device 350 is the final or exit slit, and the illustrative example of FIG. 5 has been so contrived. Where, on the other hand, the prism 377 is substituted for the ditfraction grating 380, as described above, the light may proceed in either direction, so that the slit opening 358 may be either the entrance or exit slit while the slit 460 at the same time is the exit or entrance slit respectively. This latter statement is subject to the reservation that the aperture is greater in the reverse direction, as indicated by the arrows.

In FIG. 7, there is shown a cam 220 which may be substituted for the cam 184 on the shaft 188 in the monochromator 10 of FIG. 1 and of which the peripheral edge 221 is configured to cause readout for a fused silica prism to be in terms of wave numbers 60.6 to 40x10 cmr which are the reciprocals of wave lengths 1650 to 25,000 angstrom units.

The double monochromator 280 with two quartz prisms 377 and 480 may also be provided with a like wide-range number readout. In fact, such a readout or any of the readouts abovedescribed may advantageously be digital in character as in FIG. 5, Where there is shown a four-digit counter 524 connected by a bead chain 525 with a sprocket 527 to a drive sprocket 528 on the shaft 394 and so sprocket-ratioed, as is well known in the art, as to give a correct digital translation of the micromether head setting, in this instance 1700 angstrom units, as described above.

Further, according to my invention, where two stock monochromators 10 of FIG. 1 of identical construction are to be assembled into a double monochromator 280 of FIG. 5, the individual readouts 170 for this purpose may be sprocketed and coupled directly by head chains to thus accomplish in a simple manner the synchronization of the dispersive units 380 and 480, or 377 and 480. If the readout spindle is a fine pitch, such as 200 threads per inch, the accuracy of this coupling can be assured and correspondingly an accurate digital readout coupling facilitated, if desired. Naturally electronic means of digital readout coupling can be used, as are known to those skilled in the electronic computer art.

It will be evident to those skilled in the art that the single monochromator 10 of FIG. 1 or the double monochromator 280 of FIG. 5 as abovedescribed can also serve as a spectrometer or spectrophotometer. For the latter purpose, in place of the exit slit device '52 or 350, there is substituted an aperture plate (not shown) carrying either photographic film or preferably a camera housing including a lens for imaging the aperture plate on the surface of the film of the photographic camera.

It will also be evident that the foregoing mechanisms including the wavelength indicating and slit adjusting devices may obviously be readily automated and programmed for complete automation of either the single or double monochromator 10 or 280 as the case may be.

What is claimed is:

1. A monochromator construction comprising a first monochromator having a box-shaped housing structure having a bottom wall and opposite side and end walls secured thereto,

said opposite side walls being disposed parallel to one another and having recesses therein aligned with one another on an axis transverse to said side walls,

a turntable rotatably mounted in said housing structure for rotation upon a substantially vertical axis of rotation,

a light-dispersing unit mounted upon said turntable,

entrance and exit slit units removably and interchangeably mounted one in each of said recesses and having coupling portions projecting outwardly from their respective recesses beyond the outer surfaces of their respective walls,

the projecting coupling portion of each slit unit snugly and interchangeably fitting each of said recesses,

said entrance and exit slit units having slit openings disposed substantially in the planes of the outer surfaces of their respective side walls and aligned with one another on an axis transverse to said outer surfaces,

and an optical system for directing and collimating light rays from the slit of said entrance slit unit to said dispersing unit and thence to the slit of said exit slit unit,

whereby to enable precise juxtaposition and coupling of two such monochromators to form a double monochromator.

2. A monochromator construction, according to claim 1, wherein a second monochromator of like construction to said first monochromator is placed adjacent a side wall of said first monochromator, wherein one of said monochromators is without a slit unit in its adjacent wall, and wherein the coupling portion of the slit unit of the adjacent wall of the other monochromator projects into the recesses vacated by the removal slit unit in snugly interfitting aligned coupling engagement therewith.

3. A monochromator construction, according to claim 1, wherein said slit units have paired slit jaws adjustably movable toward and away from one another for varying the slit openings therebetween and also have mechanism for so moving said slit jaws, and wherein an elongated slit jaw-adjusting member is movably mounted in said housing structure and extends across the intervening space within said housing structure at a location spaced vertically away from the paths of the light rays within said housing structure into operative engagement with the jawmoving mechanism of each of said slit units for simultaneous adjustment of the jaws thereof.

4. A monochromator, according to claim 3, wherein said slit jaw adjusting member is a rotatable member rotatably engaging said slit jaw-moving mechanisms.

5. A monochromator construction comprising a first monochromator having a box-shaped housing structure having a bottom wall and opposite side and end walls secured thereto,

said opposite side walls being disposed parallel to one another and having recesses therein aligned with one another on an axis transverse to said side walls,

a turntable rotatably mounted in said housing structure for rotation upon a substantially vertical axis of rotation,

a light-dispersing unit mounted upon said turntable,

entrance and exit slit units removably mounted in said recesses in said opposite side walls and having coupling portions projecting outwardly from their respective recesses beyond the outer surfaces of their respective walls,

the projecting coupling portion of each slit unit snugly and interchangeably fitting each of said recesses,

a cam pivotally mounted in said housing structure and having a cam edge,

a micrometric wavelength readout device rotatably mounted in one of said structure Walls and carrying direct linear wavelength graduations, said readout device being drivingly and rotatably connected to said cam,

a first operating arm engaging said cam edge and operatively connected to said turntable for rotating said turntable,

said cam edge being configured to swing said arm and light dispersing unit to project radiation of a wavelength corresponding to the indicated wavelength reading of said graduations in response to the rotation of said micrometric direct linear Wavelength readout device to said corresponding direct linear wavelength indication on the graduations of said readout device,

an optical system for directing and collimating light rays from the slit of said entrance slit unit to said dispersing unit and thence to the slit of said exit slit unit;

a second monochromator of like construction to said first monochromator placed adjacent said first monochromator with the outer side walls of said monochromators placed in juxtaposed contact but with the slit unit of the adjacent side Wall of one of said monochromators removed and with the slit unit of the adjacent side wall of the other monochromator projecting snugly into the recess vacated by the removed slit unit in interfitting aligning coupling engagement therewith,

said second monochromator having a light dispersing unit turntable with a second operating arm operatively connected thereto, and a link pivotally interconnecting said first and second operating arms,

the adjacent side walls of the first and second monochromator housing structures having aligned communicating apertures therethrough and said link passing through said apertures,

said slit units having slit openings all of which are aligned with one another on an axis transverse to said juxtaposed outer walls, whereby the second turntable swings correspondingly to the first turntable in response to rotation of the readout device of the first monochromator.

References Cited UNITED STATES PATENTS 2,206,521 7/1940 Van den Akker et al. 8814 2,595,706 5/1952 Rosin 8814 2,670,652 3/1954 Sherman 8814 2,741,941 4/1956 Madsen et al. 88--14 2,948,185 8/1960 Ward et al. 8814 3,011,391 12/1961 Fastie 88-14 3,098,408 7/1963 Cary 88-14 3,211,056 10/1965 Goldstein et al 8814 2,339,053 1/ 1944 Coleman. 2,613,572 10/1952 Mathieu. 3,079,834 3/1963 Martin. 3,131,482 5/1964 Watelet et al. 33164 FOREIGN PATENTS 166,028 7/1921 Great Britain. 356,402 7/ 1922 Germany.

OTHER REFERENCES Bausch et al.: Bausch & Lomb Grating Monochromators with Certified Precision Gratings, Bausch & Lomb Scientific Instruments, November 1953.

Cristensen et 211.: Double Monochromator Systems, Applied Optics, vol. 2, No. 10, October 1963, p. 1049.

Engis Catalog on the D285 High Output Monochromator, printed March 1963.

Engis Equipment Company Advertisment: Applied Spectroscopy, vol. 15, No. 3, 1961, p. 16A.

C. Harvey Palmer: Optics Experiments and Demonstrations, The Johns Hopkins Press, Baltimore, Md. 1962, pp. 295-297.

RONALD L. WIBERT, Primary Examiner F. L. EVANS, Assistant Examiner.

US. Cl. X.R. 356

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