Патент USA US2068829код для вставки
Jan. 26, 1937. |_. E, w. VAN ALBADA 2,068,829 REDUCING TELESCOPIC‘ VIEW FINDER FOR PHOTOGRAPHI‘C vCAMERAS Filed April 26, 19.32 09 3 Sheets-Sheet 1 1 Fig. 7. Fig. 5 Inventor: 04.2444’; £~ 7714. ?x‘. Jim. 26, 1937.‘ ‘ L E, w_ VAN ALBADA 2,068,829 - REDUCING: TELESCOPIC VIEW‘ FINDER‘ FOR PHQTOGRAPHiC CAMERAS Filed April 26, 1932 ‘ '3 Sheets-Sheet 2 Inventor: Jan. 26, 1937. |__ E, w. VAN ALBADA 4 _ 2,068,829 REDUCING TELESCOPIC VIEW FIIIIbER FOR PHOTOGRAPHIC CAMERAS Filed April 26, 1932 - ‘ 5 Sheets-Sheet 3 vInwam‘om Patented Jan. 26, 1937 v V _;2,06s,3z'9 IUNl-TED "STATES PATENT OFFICE, 2,068,829 REDUCING TEIESCOPIC VIEW-FINDER. ‘FOR ‘ PHOTOGBAPHIC CAMERAS . ‘ Lieuwe E. W. Van Albada, Amsterdam, Nether ‘ lands, assignor to the firm ofCarlZclss, Jena, » Germany ‘Application April-26, 1932, Serial No.1 607,620 In Germany May 1, 1931 (cuss-1.5) Application has been ?led in Germany .1931. , - ' 5 of the entire system is determined and, owing to 1, ' the collective,- ‘which lies in or near the common 4 ' The object of the invention is the construction ‘focal plane, having to image in conjunction with ' of reducing telescopic view ?nders which are free the objective the‘ ocular lens as an entrance pupil of distortion and have a very wide ?eld of view, of the telescope at a suitable place‘ and, at the same time; in conjunction with the ocular the these ?nders being used in connexion with pho tographic cameras and made of most simple op objective approximately at the place of the‘turn cost on a large scale. By simple'optical means strument, also the power of the collective‘ is determined, the consequence being that there only remains to. give this collective the _‘ most tical means which can be manufactured at low _ ing point of the eye of the person using the in 10 is to be understood piano and bi-convex lenses of ' plate glass or any other commonly used 'glass'. . Either the telescopic view ?nders with simple - thin lenses are not distortion-free, producing as they do a strongly curved image ?eld which is due 15 to the arrangement of the lenses‘corresponding in no way to the most favourable general effect, or the absence of any distortion is obtained by applying costly optical meansprohibiting large scale manufacture. 20 . > The reducing telescopic view ?nder consists in its simplest form of threev single lenses, viz. ‘the objective, the collective, and the ocular. With favourable form and position possible. - ‘ In the accompanying drawings, Figure 1 is a . schematical reproduction of the theoretical prin-v ciples. ' . Figures 2 to 23 represent, each in a longitu 15 dinal section, constructional examples of the in vention. ' Figures 241an'd 25 illustrate details. The condition of non-distortion ‘of a telescope ' of this kind may be described as follows: Suppose that in Figure 1 017 represents the ob a view to obtain the slightest distortion possible, .~ jective which images in its focal plane B a re- . ticulated square (11 being disposed at an in?nitely the distance apart of the vertices of the objec tive and the collective facing each other» is made. , ‘ great distance, the ocular 0k having a focal equal to at least 82% of the system represented:~ length which is twice as great will image also in the common focal plane B (for instance a frosted ‘ by the focal length of the objective and the col glass screen) and in approximately‘thesame size With a view to obtain a ?eld of view‘ as wide > the reticulated square (12 which is half as big and also ‘lies at an in?nitely great distance. - ' If both 30 as possible,‘ it is convenient to depart'from the images are identical, that is to say, if they have bi-convex lenses usedso far and to apply as a, front lens a piano-convex lens, and this because‘ the same distortion, the ?nder image will be free plano-convex lenses produce an image field which of distortion. The image produced by the objec is only slightly curved and distorted when the tive is more strongly distorted to the shape of a barrel than that which is produced by the ocu-v 86 " 35 vplane surface ismade to face the object and lar, which is'due to the ?rst image angle being‘ when the entrance pupil is at vthe correct dis tance in front of the lens (this distance being twice the second one.- The consequence is that ‘approximately equal to the length of theradius) . there remains a difference .in the distortion, this difference having to be corrected by the coIIec-I ' This favourable~ e?ect isv due to the nearly sym tive. This is possible indeed, since the collective metrical path of the rays through the lens, the 40 symmetrical path causing the slightest possible deviates the divergent marginal rays coming from ' ‘deviations. The image is distorted to the shape the objective towards the axis in a comparatively offa barrel, since the deviation of the principal stronger convergent manner than the rays near lective. ' ' rays towards the axis is the stronger the farther I er thea'xis; The image produced by the objec tive is thus given by theco'llective thehopposite 45 away these rays are from this axis when they distortion the value of which is to'be equal to the traverse the lens, This distortion is to be neu . above mentioned difference. traliz'ed by thecollective and the ocular. A telescopic view ?nder for vphotographic ' The distortion of a bi-convex lens is smallest, > cameras conveniently produces a reduced image. that is to say practically equal to‘ zero, when this of-the object,'slnce the ocular lens, which is 159 ‘small in itself and which is to beused also by persons v.vvsaring spectacles, only can afford a viewing angle inferior to that of the ?eld of view I of the‘ photographic camerawhich embraces~ in. .55 most cases more, than 50°.- ‘Inorde'rjto produce lens istraversed by the principal rays as symq metrically} as possible. If the collective is now removed from the objective, the desired-correc tion obtains-very soon because thedivergent prin cipal rays traverse the collective in proximity to the margin. Continuously increasing the dis tance would cause"; super-correction and de a de?nite diminution, for instance, ‘a two-fold ~ diminution, the focal length of the ocular is to be creasing the distance on under-correction. ' There approximately twicethat of the objective since ' consequentlyexists a position iniwhich the collec ’ va common focal plane lies between both lenses. tive exactly neutralizes theabove-mentioned dif when theobjective is of a given size, the length ‘ference; this difference’ not being great, most 2,068,829 a ' 2i ._ the lens 0 could be indentical with the lenses a favourable position is near that inwhich the prin cipal rays have as symmetric a passage as possible. and b',- in which case,.however, the diminution would be too slight to ‘furnish a clear image. With, aviewto provide this correction in the objec tive image, the ray pencils are to strike the col- " This ?nder is‘ characterized by a specially plane lective previous vto producing an image. For ,this reason it would not be correct; to place the image ?eld. - . 1 . , ‘The rear member of the objective-may be re-‘ placed by two plano-convex lenses whose vertices collective behind the objective image, as has been done sometimes, because in ‘this case it would touch each other, because an approximately sym leave the image on the object side unaltered and . metrical ray path is attained also in this case. 10 detriinentally in?uence the image which in Fig- , In Figure 4, the collective or second member 10 ure 1 is assumed to be on the ocular side, as well consists of two plane-convex lenses'b1 and b2. . Telescopic view iindersaccording to the form as greatly increase the curvature of the virtual represented invFlgures 2 and 3, however, are not image?eld. What requires being corrected is readily adapted to be used in practice, since they ‘ the more strongly ‘distorted image on the object 15 side ‘and not the ‘slightly distorted image on the ocular side; _ furnish inverted images. For this reason the said 16 series of lenses require image reversion devices, V the manner'of the image reversion, which con The lens ‘termed “collective” in the preceding sists at least in a simple inversion of the ob jects (that is to say, an inversion not neutralizing the mirror effect), depending upon the type of 20 _ text therefore is in reality the rear member of an objective consisting of two lensesw'hich in itself 20 furnishes a distortion-free image or, at option, an image slightly distorted to barrel form. - Ow- . the photographic camera. ' Figures 5 to 22 represent examples for simple ing to the convergence of the leaving principal rays, the latter image may be viewed by means Y image inversion and complete image reversion in telescopes according to Figure 2 or 3, the simple oia magni?er visually slightly distorting to cush ion iorin, in which manner a ?nder image free of distortion is obtained. ' ' Slight alterations in shape of the lenses bear only a slight in?uence upon the image, provided that they do not in?uence too strongly the sym to metrical ray path. ‘ The above is arithmetically explained in two examples, namely, in Figure 2, in which the front member a. is a plane-convex lens and in which the collective or second member b is a loi~convex lens, and in Figure 3, in which the collective or second member b’ is planoeccnvex. I From the telescopic view ?nder according to are obtained the following data: ' } inversion being attained by one re?exion on plane 25 mirrors or re?ecting prisms and the complete re version by an even number of re?exions which in most cases take place on roof prisms: - In the example according to Figure 5 the ?rst lens a, and in the example accordingto Figure 9 30 the ocular lens 0, may be ground .or cemented to the roof of the re?ecting prism f. The ocular lenses which touch with their ver tices a plane prism surface may, when reversed, be cemented to the said prism. ‘In this case 35 much of the ocular lenses is to be stopped down, which is not practical. — In Figure 5 a roof prism j'in the ray path of I the ?nder is disposed before the lens a, and in Figure 9 behind the lens 0. In Figure 7 a re- 40 ?eeting prism e lies between the lenses a and b, ‘ _ and in Figure-8 a plane mirror at is placed be- > tween the lenses h and c. _ 4:0, As a rule, image view ?nders. are disposed lat erally above the objective, which causes parallax 46 between ?nder image and objective image when With an lens-es, ‘no is equal t0 recs. The positionof the collective h, which ‘is ap . proximately at equal distances from the ocular c and the image 0’ ofv this ocular, shows that the 50 ray path through'the collective b is practically symmetrical. This slight deviation from the symmetrical ray path is just sufficient to com .55 pensate for the ‘distortion difference. The en trance pupil E.p. is ata distance in front of the front lens a which is equal to the radius; the im age or the objective is behind the ocular c; the ' , the objective image, which‘embraces an angle of photographs are to be taken at a short range. This parallax can be avoided according to Fig ure 6 by applying a telescopic view ?nder ac cording to Figure 2° or 3 with vertical axis and 50 by disposing in front of the objective 9 of the photographic camera a plano-parallel plate h in clined atv45° towards the objective axis. The telescopic view ?nder is so adjusted that the cen tre oi the objective diaphragm ‘is the re?ected 55 image of the centre of the entrance pupil of the ?nder.' Below the plane-parallel plate is'pro ' approximately 80°, lies near the rear side of the vided a deep-black layer.‘ In Figures 10 to 15 a prism body .eilecting a lens 11, where the image vfield diaphragm B’ is to ' complete image reversion is disposed between the so be positioned. '- _ ' . From-the telescopic view ?nder according to Figure 3 are obtained the following data: , ‘ ' ' ' l ’ d1=a ' 11:10.9 lenses 2: and c in the ray path of the linden The v roof prism is in Figure 10 a straight-vision prism T1, in Figure 11a so-called Porro secondaryre version prism 3?, in Figure 12 an Abbe prism‘ i3, in Figure 13 a Leman rooi prism f‘, in which’ 65 ' the axial ray is displaced in parallel, in Figure 14 apentagonal Hensoldt prism f5 e?ecting an iden tical parallel displacement and which has a root 70 with all lenses, no is equal to .1525. .rrne practical advantage of the telescopic view ?nder according to Figure 3, which comprises anaimage held of 54”, consists in the two ?rst members being identical ‘in themselves, which-simpli?es, 75 and reduces the cost of, the construction. Even edge at one side and is at the contiguous‘ side con nected to av totally re?ecting rectangular prism 70 e, and in Figure 15 two Dove prisms e'lylng be-. hind each otherand whose re?ecting surfaces are displaced relatively to each other at 90°._ ._ l . In Figure 17 is illustrated (‘for the sake of dis tinctness on somewhat too large a scale) a sys- 75 ' 3; 2,008,829 tem of four small roof prisms I" disposed before the front lens a. Figure 17a illustrates the four roof prisms f‘ as seen in the direction of the ar rows in Figure 17. This system is a wide-angled and completely reversing system which may be very small. , - In Figure 16 only a simple inversion takes place, the. entrance pupil, as also in Figure 17, being brought approximately into the centre of the re 10 versing system, which consists of two rectangular prisms e2 whose’re?ecti'ng surfaces touch each other. , ' ' In Figure 18, two re?ecting prisms e3 are‘ placed in front of the objective in such a manner that 15" their re?ecting surfaces act. inwardly. In Fig ure 20,'the prisms e4 are placed in the same man ?nder image, owing'to the ?xed image ?eld dia phragm, always corresponds vto‘the image pro jected on the plate also when the image is only simply inverted by means of a plane mirror. If in a telescopic straight-vision finder the image is-only simply inverted, the image ?eld diaphragm must be either-stationary, according to Figure 24, or revoluble through 90° about the ?nder axis, according to Figure 25, because the ?nder itself, or ‘at any rate its inverting system, must be turned through 90° about the ?nder axis when changing from a horizontally elongated to a vertically elongated image. When the image ?eld‘of the ?nder is hori zontal, use must be made either of a stationary 15 cross-shaped diaphragm according to Figure 24 or of a diaphragm rotatable through 90° about ford an image reversion for a very wide ?eld (up ‘ the ?nder-axis according to Figure 25, in which , to approximately 90") also when the respective case also the telescopic ?nder is to be rotatable about an axis parallel to that of the photographic 20 20 pupil is just outside the system. In Figure 19, the roof edges of four roof prisms objective. For this reason the arrangement ac ner, but behind the ocular. Thesesystems af f7 are turned towards outside in order to [effect ‘a complete image reversion over a wide ?eld and within a narrow space. Figure 19a illustrates the four roof prisms f’ as seen in the direction of the arrows in Figure 19. v - cording to Figures 8 and 9 with rotatable rear ' part is very suitable and advantageous. I claim: . v 1. A reducing telescopic view ?nder for photo 25 graphic cameras, comprising an Objective which consists of two thin converging, lenses, a dia- ' respectively, are so placed between the lenses 1; -' phragm disposed behind the objective, and an and c that the axis of exit is inclinedrelatively ocular, the distance apart of the vertices of those In Figures 21 and 22 roofprisms f‘ and I’. surfaces of the said two lenses _which face each 30 other being approximately 83% of the focal D version may as well take place by means of a. length of the objective, and those principal rays series. of lenses according to Figure 23, in which which traverse the said two lenses approximately symmetrically providing‘ an image without dis case all of the middle lens, except a small aper 35 ture, is stopped down. The objective consists of 'to'rtion and converging approximately at: the the lenses 0 and b. The image produced by-the locus of the ocular.“ 2. A reducing telescopic view finder for pho objective is reversed by the lens i. The‘ ocular is 39 to the axis'of entrance. Instead by re?exion, a complete image re composed of the lenses 01 and c’. The data for this lens series are as follows; 40 tographic cameras, comprising an objective which consists of two converging lens systems, a dia phragm disposed behind the objective, and an 510 ocular, the distance apart of the vertices of those surfaces of the said two lens systems which face ' each other being approximately 83% of the focal length of the objective, and those principal rays which traverse the said two lenses approximately 45 symmetrically providing an image without dis tortion and converging approximately at the 45 locus ofthe ocular. _ - 3. A reducing telescopic view ?nder for photo 50 graphic cameras, comprising an objective which 50 consists of two thin converging lenses, a dia phragm disposed behind the objective, an ocular, and re?ecting means which de?ect the axis of tically elongated pictures may be equipped with the-?nder, the distance apart of the vertices of a fixed/rectangular image ?eld diaphragm, pro- . those surfaces of the said two lenses which face 55 Diaphragm behind lens To, 11:35 With all lenses, up is equal to 1.5.25. Photographic cameras for horizontally and_ver each other being approximately 83% of the focal completely reversed image is The same] length of the objective, and those principal rays holds good in the case of Figures 8 and '9,'where, which traversethe said two lenses approximately“ however, the image ‘reversing re?ector _(or the symmetrically providingan image without dis-‘ prism) and the ocular lens are to be rotatable tortion and converging. approximately at the locus 60 vided that a telescopic straight-vision ?nder with about the entrance axis of the ?nder. -_Independ= ently of the position ofthis revoluble part,_the ' of the ocular. ' " '