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Aug. so, ‘1938. M. BEREK 2,128,394 MICROSCOPE Filed Aug. 27, 1937 V INVENTOR BY A/ax Eerak A ORW Patented Aug. 30, 1938 2,128,394 UNITED STATES PATE NT OFFICE) 2128394 MICRO SCOPE Max Berek, Wetzlar, Germany, assignor to Ernst Leltz, G. m. b. H., W t ' Application August 27, This invention rel_ ates to croscopes for determinin w 3 Claims. improvements in mi- . e zlar, Germa 1937, Serial No. 161,207 (CI. 88-40) ‘ sired identi?cati analysis of 10 10 15 15 20 and devices for carrying on such analysis are known. 25 An entirely differe nt pect to the examination of 25 I'red of extinction ninety fierent angles. Re depending upon the ?eld of View cal analysis beca me impossible. the true line as character of after de?ection was maintained only in “the cent er of the this was true 021]‘1 so long a ?eld of’ View and. even tion of the incoming bundle5 the plane of polariza a 55 of light re nt, possibly 0211 31 one degree the polarized light 1"‘ character 0 ' $2,128,394 2 of the surface of the object a greater or lesser after re?ection was no longer maintained in the center but in some other spot within the field of view. Hence it happened very easily that a mi croscopist who had made certain observations one 5 day and used the same microscope for examining the same object the following day, by inadvert ently making only a very slight error in the ori . entation of the polarizer, would arrive at entirely portion of the rays which impinge uponthe sur face passes by re?ection or diffraction back to the observing eye' through the objective and eyepiece. different results. Such slighterrorswere almost They were also used with vertical illuminators 10 unavoidable because the mechanical means for for qualitative observations invpolarized reflected Referring now to the construction of the de ?ecting prism ii the following observations are to be noted. As stated above, prior ordinary total de?ecting prisms served their purpose satis factorily so long, as ordinary light was used. the correct orientation of the polarizer were never su?iciently accurate and the optical criteria for ascertaining whether the linear character of the polarized light was correctly maintained were 15 likewise not completely certain. be able to correctly de-, In order therefore, to termine and measure the anisotropic charac 10 light, it being believed that such qualitative ob servations were sufiiciently accurate. for identi ?cation purposes. It has been shown that this belief was erroneous. It has further been shown 15 that quantitative observations could not be made with such prior devices and until the present dis covery and invention weremade, nobody to my teristics of opaque anisotropic substances under _ polarized re?ected light it became necessary to devise some new instrumentality, researches hav '20 ing shown that the behaviors and characteristics of such substances heretofore attributed to the objects themselves, were incorrect and unreliable knowledge, knew how to construct a suitable 20 prism for this purpose. Researches showed that if a simple right angled isosceles prism with a .single total re fiection at forty-?ve degrees on the hypotenuse is compared with a trapezoid prism having three . because of the inadequacy of the equipment used. - total re?ections, as shown in Fig. 2, the direction 25 of the incident ray being'at 90° to the entrance ' The object of this invention is the construc 25 tion of a device, namely a prism to be used in surface of the prism, both being made of the a microscope, for de?ecting polarized light at same glass of the refractive index of m): .516 ninetydegrees having the distinguishing char then it will be found that (with half of the angle acteristic that the incoming polarized light after of view being four degrees and the aperture being 30 having been re?ected remains still completely - one degree) the deviation from the required 30 linearly polarized and has the same direction of homogeneous linear polarizationI amounts to five vibration over; the entire ?eld of view. In the point eight degrees (5.8") in the case of the sim accompanying drawing Fig. 1 is a side view of ple rightangled isosceles total re?ecting prism if a microscope embodying the invention with parts ' the polarization plane of the polarizer is exactly 35 in section and broken away and other parts being 35 shown diagrammatically. Fig. 2 is a sectional view of the reflecting prism. Fig. 3 is a diagram illustrating certain phases of the invention. perpendicular to the entrance face of the prism or trapezoid. It will also be found that the devia tion of the polarized light from being truly linear in character or in other words its elliptical Referring to Fig. 1, the numeral l indicates a ' polarized condition amounts to within one 40 source of light suchv as a ?lament lamp for in 40 stance. ‘2 and 3 are collecting lenses for converg ing the light rays before they enter the vertical illuminator. 4 is a diaphragm to eliminate scat tered light from the course of‘ the light rays. 5 These parts are shown, diagrammatically; In the illuminator‘ there is mounted a_ polarizing twenty-eighth (1&3) measured by the proportions of the main axes of the polarization ellipses. These errors,_however small they may appear to be, make it impossible underv certain circum stances to use the observation forpurposes of 45 diagnosis." prism 5, an iris diaphragm 6 and a lens ‘I. The The trapezoid prism is more unfavorable un der the same. conditions than that of the simple latter not only renders the incoming light rays parallel but also, in conjunction with the objec right angled prism, at least with respect to the deviation from the true lineation of polarization, 50 microscope forms an image of the . because although the error in the azimuth is tive 8 of the iris diaphragm 6 in the planeofthe bbject 9 ' only one point seven degrees (13°), the error with respect to the lineation, i. e. the ellipticity "wwupon the microscope stage in. The numeral ii designates the trapezoid mul of the polarization is greate , namely one twen tiple re?ecting prism according to this inven tion which, having a refractive index as herein after set forth, will re?ect an incoming linear polarized light beam so that its linear character is retained throughout the ?eld and its direc tions of vibrations remain parallel to each other so within the field of view. The prism is suitably mounted upon a support 12. Within the micro scope ‘tube l3 is-mounted on analyzer prism it between two anastigmatic correction lenses l5, tieth (1750).. With errors ‘of such magnitude, the 55 polarization condition of the bundle of rays is insufficiently homogeneous and insufficiently lin ear for quantitative measurements and investiga tions,and a dependable analysis of the optical con stants of the polished surfaces becomes impossible. 60 The proportions become even materially more un polarizer deviates from the re ‘ favorable if the quired orientation with respect to the main plane of incidence of the prism, even if it is only a fractional degree, because even though the polar 65 65 porting the several parts and i1 is the usual izer is oriented most carefully such small errors are unavoidable. From this it will be seen that vmicroscope eyepiece. . ' ' The object, for instance an opaque anisotropic an ordinary trapezoid prism having an uneven the stage. The polar-_ number of total‘ re?ections cannot be used for substance, is placed upon 70 ‘ ‘ized light, after having passed through the il the purposes of this invention. Figure 2 illustrates a trapezoid glass prism for ' 70 luniinator, strikes the prism ii and is re?ected downward through the objective 8 and upon the de?ecting polarized light at an angle of ninety l5. l6 designates the microscope stand for sup 7 object which is then illuminated by a bundle of light rays circuiarin cross section, the size of the circle being‘governed by the size of the open 75 ing of the diaphragm 6; According to the nature degrees. This prism is di?erentjrom the ordi nary trapezoid prism in- that it is constructed in accordance with this invention and is char- 75 2,128,394 3. is truein the case 01' solutions in which'the number of re?ecting surfaces z=6q+3, where q represents a number from the uneven row of ‘ numbers 0, 1, 2, 3, etc. gill these cases lead to a refractive index of n=\/3 and for these the phase difference is greatest for an angle ‘ofincidence 10 10 .15 15 re?ections. Experience has demonstrated that the critical limits of plus or minus five percent ' must be maintained or'the desired results can not be obtained. 20 25 .3c E. to .5' degrees.v found that the errors in polarization after a 90 ' degree 30 ' de?ection of the bundle of rays,‘ if the polarizer has its plane multiple of 1r. The relative refractive indices .11 between the ' medium of incidence and. (a) Ina simple total re?ecting prism of glass having a refractive index of 12:1.5161 40 For the rays Azimuth errors 35 Ellipticity blow? moms H 50 ground on ‘the one glass body, then the value 12. obtained from the above equation. will be found to be :55 '_ I | l | (b) In a prism of trapezoid ‘cross section with ree total re?ecting surfaces in a glass body having a refractive index of n=1.74:-— ~ .n= For the rays Accordingly, 6mm Ellipticity _ re?ecting surfaces‘ (z=5), a useable value for the refractive index ' is obtained only if p='0, namely n=1.495. with seven re?ecting surfaces a useable value is ob~ tained only if 11:0, namely n=l.453. These values result, in the case oi.’ a parallel bundle of rayswith an angle of incidence of 45° on each surface, in a condition of polarization which is 55 v. ' . Di’é‘ét A _______________________________________ __ B. C_ ~ 0. 001 —0. 00 —0. 04 +0. 000 +0. 000 D- +0.00 —0. 002 E_ +0. 04 —0. 000 -0. 00 +0. 001 ~ F_ G; H.. .T _________ __ e - . +0. g; . 38(1) -—0. 000 .65 non-elliptical and azimuthally correct. These Experience has demonstrated that the quan titative measurements are a?ected if the azimuth 65. noticeably exceeds the proportion of 1: 1000. 70 A comparison of the two tables given shows to is the onein which the ‘value of n, proximate angle-oi’ incidence of 415°, shows the The prism has been shown as an element in a speci?c form of microscope. _ It will 75 least possible variation in the phase di?erence be understood of course that the construction of the prism and its use in examining opaque aniso when the angle of incidence is changed: 70 tropic substances in polarized re?ected light is 75 A; i 2,128,894 the main object of this invention and does not depend upon its use in a speci?c type of micro scope. 1. A microscope for determining the optical constants of opaque anisotropic substances in po larized re?ected light comprising an objective, an analyzing prism and an eye piece in optically op having a light entrance surface and a light emit ting surface at ninety degrees to each other, the light entrance surface being at ninety degrees to the incoming rays, said trapezoid ‘de?ecting prism having three total de?ecting surfaces for de?ect ing the incoming linear polarized light rays from the polarizing prism at ninety degrees to the ob jective, the refractive index of the said trapezoid de?ecting prism being n=\/3=1.'732 to within erative relation with a common optical axis; a ?ve per cent thereof, the polarized light emerging polarizing prism, means for supporting the same from the said trapezoid de?ecting prism without 10 in the path of the incoming light rays with the optical axis of said prism at a right angle to the optical axis aforesaid, a de?ecting prism inter posed between said polarizing' prism and the ob jective for de?ecting at ninety degrees the light 15 rays from the said polarizing prism to the said objective; said de?ecting prism having a light entrance surface and a light emitting surface at ninety degrees to each other, the light entrance surface being at ninety degrees to the incoming 20 rays, said de?ecting prism having an uneven num ber of total re?ecting surfaces, the relative re fractive indices between the medium of incidence and the medium externally surrounding said total re?ecting surfaces having a value of n7_—\/3=1.732 25 to within ?ve per cent thereof for the purpose of affecting a linear and azimuthal homogeneous correction of the polarization condition of the de?ected light from the polarizing prism to the so objective. '1 v 2. A microscope for determining the optical constants of opaque anisotropic substances in po larized re?ected light comprising an objective, an analyzing prism and an eye piece in optically operative relation with a common optical axis; a 35 polarizing prism, means for supporting the same in the pathof the incoming light rays, a trapezoid prism interposed between said polarizing prism and the objective for de?ecting at ninety degrees the light rays from said polarizing prism to the 40 changes in the linear polarization thereof. 3. A microscope for determining the optical constants of opaque anisotropic substances in po 15 larized re?ected light comprising a microscope tube, an eye piece at the upper end thereof and an analyzing prism in ‘the lower end thereof in optically operative relation with a common opti cal axis, a housing secured to the microscope tube below the analyzing prism therein and extending 20 to one side of the microscope tube, an objective in said housing in optical alinement with the analyzing prism and the eye piece, a lens system in said housing having its optical axis perpendic ular to the optical axis of the objective and con; sisting of a polarizing prism in the path of the incominglight rays and a trapezoid prism having three total re?ecting surfacesfor de?ecting said incoming linear polarized light rays from the po 30 larizing prism to the microscope objective, the said trapezoid de?ecting prism having a light en ninety degrees to the incoming ' trance surface at rays from the polarizing prism and a light emit ting surface at ninety degrees to the optical axis of the objective, the refractive index of the said trapezoid prism being n=\/3=l.'732 to within ?ve per cent thereof, the polarized light emerging from the said trapezoid de?ecting prism without changes in the linear polarization thereof. ’ Patent No. 2,128,394. ' 40 MAX BEREK. said objective; said trapezoid de?ecting prism - 10 Certi?cate of Correction 7 August 30, 1938. MAX BEREK. - ‘ ' It is hereby certi?ed that errors appear in the printed speci?cation ef the 15,above after Page 3, ?rst column, hne numbered patent requmng correction as follows: the word and period “directions.” insert the sentence In accordance with, this invention ' hereinafter set forth; andlines 31, 32, and 33, the_prism must comply with the data _ “, for all the rays of the bundle amount'to an un strike out the comma and words Patent should be-read with these even multlple of er”; and that the said Letters corrections therein that thelsame may conform to the record of the case in the Patent Signed and sealed this 15th day of November, A. D. 1938. Actznngltlgmiiasgkwrielrsga??ents.