US1178476A - Combined focus and field finder. - Google Patents

Description

1. BECKER. y COMBINED Focs AND HELDJHNDER. APPLICATIDN FILED JUNE 1'901.

- Patented Apr. 4, 1915.

4 SHEETS-SHEET I.

l 4 is SER.

x Y I.

:/ Live/dor 1. BECKER, COMBINED FOCUS AND FIELD FINDER.

Patented Apr. 4,1916.

4 SHEETS-SHEET 2 AAPPLICATION FILED IUNE 4| 190|.

1. BECKER. v COMBINED FocusAND FIELD FINDER.

APPLICATION FAILED JUNE 4.1901.

Patented Apr. 4, 1916.

4 SHEETS-SHEET 3 1. BECKER. COMBINED FOCUS-AND FIELD FINDER. APPLICATION FILED IUNE4. 190i.

Ptented Apr. 4, 191.6.

4 SHEETS-SHEET 4.

in an improved form of the combined finder UNITED s'TATEs rPATENT oEEioE. f`

' JOSEPH BECKER, 0F WASHINGTON, DISTRICT OF COLUMBIA.

COMBINED FOCUS .AND FIELD FINDER.

Speccation of Letters Patent.

Patented` Apr. 4, 1,916.

Application lfiledJune 4, 1901. Serial No. 63,106. A

To all whom t may concern.' H

Be it known that I, JOSEPH'BEGKER, a citizen ofthe United States, residing at lVashington, District of Columbia, have invented a Combined Focus and FieldFinder which permits not only of locating exactlyv on the platethe object to be photographed, but which also permits of quickly and sharply focusing the same.

. .My present patent application is identi fied for convenience .of reference in my re is fixed relatively to the stationary imagev receiving plane of the camera and which is adapted to rotate amirror that is pivotally mounted on the movable lens carriage.

Incidentally, my invention also consists lens and prism support seen in Fig. 55 of my said Case A, to constitute in combination with it and other parts a non-projecting focusiand field finder.

The invention further consists in a special means for offsetting the path of the movable image, either to secure a focus indicating positionof exact coincidence, as in Fig. 11 of my said Case B, or to secui'e a focus indicating posit-ion of non-coincidence or alinement, as, in Fig. 14 of my said Case B.. l

The general object of my present invention is to provide the common and most compact form of folding camera with an optical focuser that does not in any way complicate or interfere with the ordinary manipulation of the camera, and that does not.l add to its bulk when the camera is folded up for transportation.

In the accompanying drawings: vFigure 1 is a side elevation of one form of my folding focusing camera complete. 2 is a front elevation thereof. Fig. 3 is an-enlarged vertical section on line 3-3 of Fig. 2, showing-.only the focus and eld finding attachment. Fig. 4 is an enlarged front elevation thereof.

Figs. 5 and 6 are detailv yiews. Fig. 7 is a.face View of aspecial adjustment of the fixed mirror, by adjustment of 'the lens upon which it is mounted, the adjustment being angular about a substantially horizontal axis approximately parallel to the camera axis, and perpendicular to the paper in Fig. 7 Fig. 7a (on Sheet 1) is a fractional front view of a modified form of Fig. 7 in which provision is made for adjusting the inclination of the eye mirror 'angularly on two perpendicular horizontal axes, and, therefore, on any desired horizontal line as resultant axis of rotation. Fig. 79

(on Sheet l) is a vertical section on the vertical meridional plane 7u of F ig. 7a.` Fig. 8 1s a diagram of the optical elements of my improved focusingfinder, showing how said elements coperate to form two -substantially equal vimages 7 and c' of any given object Z directionally close by such object, and

relatively movable by change in the distance of the object or by change in the relative set of the optical elements. Fig. 9 shows the finder image of a head as it appears to the operator when he uses the apparatus in tak-l ing a. portrait and in focusing on the persons left eyebrow which is seen fractured 1n the figure, indicating that the vsubject is not in focus. Fig. 10 shows the optical elements as they are shown in Fig. 8, but on an enlarged scale to make the detail features of the fixed prism clear. Fig. 11 is a view of4 my compound form adapted for either long or short focus work, showing in dotted lines the extension bed 100 with the optical element set for long focus exposures by removal of one finder lens Z', and of one camera lens 82. Fig. 12 is a perspective showing how the finder image and the camera field both appear simultaneously to the operator.

The camera proper, Fig. l, is a folding bellows camera of the usual construction comprising a box 23, a hinged cover 19, which opens and locks at right angles to serve as camera bed, a bar 50 adapted to slide in and out on the bed, and a lens carrying frame which is adapted to be clamped -on bar 50 at any desirable-point or unclamped and pushed back into box 23 for folding. The in and out motion of bar 50 being limited, the" lens frame should for my purpose preferably be clamped to bar 50 at the point which will give the lens all the freedom of motion desirable and not more. l, therefore, provide bar 50 with a projecting lug 90, against which the lens carrying frame is brought to bear before it 1s clamped.

Fastened to the sideof the lens carrying vframe by screws u, o and 0, Fig. 3, is a boxside walls n n carry coperating lugs z z,

Fig. 4, to serve as abutments for a`lens Z which is firmly held in Contact with' the .various abutments y 2 a and the top wall x by a bent spring o. This spring o, shown enlarged in Fig. 5, has its lower end notched is as easily 'remounted for use and its abut-4 v toforni a tenon Q which engages in a hole r formed in-the rear wall t; and this same spring 0` has its upper end recessed and partly turned up, as seen at 3 and at s in Fig. 5, to form a step-like notch adapted to engage the lower rear edge of the lens Z. The spring o is easily pulled out of engagement with recess r to free the lens Z, which can then be removed for cleaning. The lens ments fr, y, a, z are so selected and arranged as to insure that it will always accurately and automatically return to its proper position in the finder .frame or housing.

The lens Z supports cemented thereon by means of Canada balsam a small total reflection prism p the hypotenuse face of which acts as a fixed mirror, and this mirror, being virtually an integral part of the lens, is surely held in and always automatically returned to its desired position. A second lens Z', which does not have to be so accurately set, is kept in place by a shouldered block w which is fastened ,in place by a screw passing through the back wall t. The.

upper end of this wall t is provided with a rectangular opening 26, Fig. 3, the edge of,

which serves as bounding line for the finder image. The side walls fn, n at their lower yfront ends are perforated at 3 points to admit a rod 5, Fig. 4, which is bent back upon itself at 13 to form a shorter but parallel branch 5.` This shorter branch serves as lock to prevent any rotation of '5 and it also acts as a support for the spiral spring 6. By taking hold at the bend 13, rod 5 and its shorter branch can easily be slippedl into position and they are effectively held in place against removal, by friction, as soon as pressure is applied to spring 6. Rod 5 serves as a pivotal axis for a base plate 4, Figs. 3 and 6, which carries the total reflection prism c.

The two rearwardly converging sides of plate 4 are folded down to form stiflening flanges 9, one of which, Qin Fig. 3, is eX- tended to form the lever arm m. At their forward end 10 the two flanges become parallel and are shaped to coperate with the f downwardly bentlugs 11, 11 in forming two angular or V bearings 12 adapted to rest directly on axis 5. The front of plate 4 has two upwardly turned lugs 7, 7, Fig. 6,

andthe rear edge has an upwardly extending flexible hooked arm 8, Figs. 3 and 6.'

The prism c is mounted by restino` its lower edge on 4 and against the lugs'7, 7 and then snapping its upper rear edge in under the to themovable end of spring 6. The lower end of this pin 15, Fig. 3, is used as a handle for connecting and disconnecting the spring 6 with the base plate 4 while the latter is in place on axis 5.

The fixed end of spring 6 is hooked over the lower edge of the inside wall n, and this hook suffices to hold the spring against accidental removal, provided the spring 6 has been connected to plate 4. Spring 6 acts to pull the two bearings of'plate 4 firmly down into contact with rod 5l and to keep the end of arm m pressed in Contact with the cam face 7c of plate 17. The latter has slots 20, 20 and clamp screws 21, 22 providing for vertical adjustment on a base block 18 which is rigidly fastened to the base 19,

Fig. 1, ofthe camera. This simple'arrange- 'ment permits of adjusting the inclined plane or cam la, so itshall answer for any lens, whatever be its focal length. To make this adjustment easier and more certain (with lenses ofapproximately'the same focal length) I have designed the device so that the lever m shall, when the camera is. Vin focus on a very distant object, be in contact with saidcam immediately over screw 21. Two observations then will in all cases sufice to set the cam or to correct its set if it should have become deranged, and this without any necessity whatever for actually determining the focal length of the lens.

The process of adjustment isas follows:

The camera is mounted on a firm base or tripod and first focused by the usual method on a very distant object. The operator, then lookingin the finder, will, if the device'is out of adjustment, see the distant object" broken. while looking in the finder, mends the broken image of the distant object by lowering or raising cam k at itsrear end about.

the forward screw 22 as a pivot and, when the image is mended, he tightens screw 21 and loosens screw'22 to prepare for the second operation. He now focuses by the usual method on a near object; then, looking in. the finder, he mends the broken image of the near object (if such image should appear broken) by raising or lowering the forward He then loosens screw 21, and,

ext'reme outer end of its stroke.

end of the cam about screw 2l as a pivot and then-clamps screw 22. It will be noted that the first adjustment for the distant 0blimmediately over screw 21, and which, as 4stated above, is the point corresponding approximately to the set for infinity. Where the lever m bears during the second adjustment is not material, although it Would be better to haveit at about one-sixth from the When the camera is folded up the objective carrier is pushed back into case 23 of the apparatus, and lever m falls from cam /c into a position such as to occupy as little place in length as possible so it can easily lodge itself in case Q3, the same as all the other parts of the finder. -An opening in the rear wall t is provided, Fig. 3, to allow the prism c to turn as far back as is necessary to make lever nz come well forward.

A diagonal cross Qi on the nearly vertical face of prism C, Figs. 2 and i, serves indirectly as a bead sight for the eye which will be known to be in a correct position when the cross is seen in the finder in the center of the fixed-mirror p which serves as peep sight. To facilitate the correct placing of the eye. that is, to facilitate finding the image of the cross in the peep mirror p, I provide on the camera box 23 a mark 25, Figs. l and 2. The cross' being traced on the vertical face of the prism, its image does not change place visibly in the finder in spite of the oscillations of the reflecting prism c, because in the adopted arrangement the visible image of the cross, though movable, does not appear to'move, for it moves in a direction coincident with the linev of sight. here the frame t n is to be fixe'dvto the camera without adjustment, the upper reflector /1 should be adjustable about an axis through lugs z e, Fig. 4, and'to secure this adjustment all that is necessary is to make stop y/HFig. adjustable in a line parallel with the principal axis of the camera. Such adjustment, shown at (i2 in Figs. 7a and 7, Sheet one of the drawings, raises or lowers the`apparent position of the centering cross as seen in the finder, and, therefore, serves to make the center of the finder image correspond with that of the camera image. Parts L, RZ, Z, X, X, and Y in these Figs. 7 and 7 correspond to those parts of'the other figures that have the corresponding lower case letters.y

The lenses Z and Z', or L. which I have shown as preferable, are divergent lenses; but I do not `limit myself' to the use of a divergent lenticular system or even to a lenticw ular system. In the lenticular systems, lenses of any plus or minus focal length might be used, and even those in which the focal length is infinite; that is, glass with flat faces neither convergent' nor divergent may present advantages. The glass may be a simple Wedge, or Vif no drop in the line of sight is required a piece of plain glass will do, and in the latter-casel a frame corre- Y sponding to the outline of the plate is often l all that is necessary. When the margins of a picture are secondary, the focusing-finder reduces itself to the refiectors setas if the field limiting means were present, and' so as to act, therefore, as centerers; that is, as' means for centering the image on the plate without determining its extent.

The fundamental'7 principles involved in A the structure of my Figs. l and 2 are eluci dated in Fig. 8, Where the reflector c is shown set parallel With relation to p, from which it is separated in this its parallel position by a distance ofb centimeters. The object Z to be photographed emits two distinct groups of rays: one group that proceeds directly from Z through lens Z to form the image f; and a second 'set that proceeds by reflectionon o and then on yz to form: first, the full size image 'g in mirror ci.' then the full size image in mirror 72,' finally the reduced image z' inlens Z. As the separation of the mirrors c, p in this their parallel relation is I) centimeters, the image 7L must be offset with relation to the object d back and 1 upwardly through al distance equalvto 2 Z centimeters, so that the lens Z formsy an image z' of 72, which is similarly offset back and upwardly from the image f. In speaking of the images f, 5;, it' and z' as being formed I use the term formed as it is always used in the science of optics; that is, without alf leging anything as to visibility. What parts of an image are visible, and what parts are 'not visible, depends upon proportions, rela comprised in this same angle alpha (c).

But because of the offset mentioned above the visible part of this image z' comprised in the angle alpha (oz) does not correspond to the part of the image f comprised in the- I "same angle; it follows, therefore, that when the object cZ is not at infinite distance and the mirrors 7) c remain parallel the eye sees of the object an incomplete image, the nnss-` mg part of which'ls filled by a portion of anotherl image, which does not register or match with the first. l the first image corresponds t0 the middle of the eyebrow of a person being photographed,

If the missing part of Fig. 9, this middle part of the eyebrow is seen in the finder as a part of the other image, and consequently is raised so that the eyebrow looks as if broken into three parts. By proper angular displacement ofmirror c, however, tojshift image i, the latter may be brought into apparent coincidence with the image f, so that the eye shall see in the finder only one -image that is complete and without any discontinuity. The angle through which reflector c must be turned about pivot j to obtain `this apparent coincidence depends on the `-distance of the object. When the object is far off or at infinity the linear distance 2 b centimeters between this object al .and its image h appears so small as to be negligible; that is to say, that the two images f and i practically coincide, with the mirrors parallel.l As the object approaches, however, the two images f finder.

The exact law connecting mirror inclinations with camera extensions is shown in Fig. 23 of my said Case A, in which the mirrors M4 and N4 correspond, respectively, to thepresent mirrors c and p, and as a result thereof the'same is necessarily curved, its curvature being greatest at the highest point of the cam to lessen gradually as the cam falls. Where, therefore, a straight cam is used, such as 7s in Fig. 1, the device is not theoretically accurate and it can only be"` exact for two different distances of the object point. llhere the object pointA to be focused on is too small to be conveniently divided by the edge of prism p, my mirrors are set as explained in connectionl with Figs. 14 to 16 of my said Case B to offset the vertical path of the movable image.

.The path of the movable image may be offset horizontally to any desired degree by means of the arrangements shown in Figs. 7, 7a, and 7b, used for tilting the mirror pabout a horizontal axis parallel to the axis of lthe camera lens. The normally fixed mirror p, therefore, has two distinct angular adjustments that differ in kind and in purpose, to wit: first, one angular adjustment produced by lug Y, Fig. 7b, and which takes place on the transverse horizontal axis a 2,' secondly, a second adjustment produced by screw 60, Fig. 7, and which takes place about a longitudinal axis parallel to the camera lens. The first on a 2 as axis raises or lowers'the line of sight passing through the fixed mirror p by raising or lowering the image in p of the cross lines reflected in the lower mirror c; and-the second-adjustment produced by screw-60, Fig. 7a, serves to horizontally offset thevertical path of themovable image withv reference to the object.

To sum up: when my finder is'used to locate the image on the plate, and also for focusing the same, it is always arranged so as to produce two images of all objects that are examined with it and its mechanism is combined with that of the camera so that the operator can by the relative position of the two images judge whether the object is or is not in focus and in which direction it is out of vfocus so he may easily bring it is secured by making the finder not with an ordinary lens, symmetrical with respect to its principal axis, but by means of a suitably chosen asymmetrical lens. All rays emanating from the object and meeting such a lens are refracted by it inthe direction of the eye as if they proceeded from the image f, and are all comprised in the pencil of raysbeta ((5,), which emerges lfrom the symmetrical lens in its superior part; this part alone of the lens is, therefore, useful and lines, being of no use whatever, is suppressed. The finder, though eccentric, hasto be made inthe usual form of a rectangle corresponding to the dimensions of the sensitive plate; that is to say, it is stilla rectangle, but one whose center is not situated on the principal optical axis of the lens in which it is taken. This very importantdisposition of the finder is applicable to all finders; as well to those which are used simplyas finders to locate the object on the camera plate as to `tho-se which focus because it is evident that -the refraction is entirely independent of the presence of reflectors c and p; that is to say, of whether it is necessary to see in the finder the image f and part of image i, or only image f. Inpractice, it is not indispensable vthat the pencil ofrays gamma (Y) be outside of the pencil of rays beta It is sufiicient that it `be out of the axis of the latter; that is to say, that the finder does not hide the principal or central part of the object which is to be focused upon.

Fig. 12 is a perspective on the vertical lio consequently the other part shown in dotted ,10.5

the camera. `perspective plane that is situated directly plane AC', Fig. 11, of'the rear end wall 99 of the camera as perspective plane, showing how the finder and the camera as well as the camera field and finder image must appear to an operator who has leveled his camera and placed his eye Ain a correct obA serving position at a distance to the rear of Point C is the point of the opposite and at the same level as the observing eye. According to the rules of perspective, point C is the image of the infinitely distantcentral point C of thecamera field; and it is also the vanishing point of the three parallel. central rays CE, CF, CA of Fig. ll, as well as of all other horizontal lines parallel to the camera axis. The finder i image appears with its center directly over sighting point Q5. 1n Fig. 12 the vanishing point C is closer to the finder with long focus than with short focus because the eye in short focus work is at E, Fig. 11, while it is lower at Efor long focus work; otherwise the appearances are the same in all cases. The operator places his eye at the correct elevation by positioning it to see the cross 2li-appear as reflected centrally in the eye mirror, as illustrated in Fig'lQ. I The part 40 of the reecting prism p, Fig.

` 1o, a; the right 0f the 1in@ 2, ring. s, which is drawn touching the top edge of mirror c, and the lower edge of lens Z is suppressed because it is useless for reflection and causes an interruption of the images. To make the line of separation between the two image fragments as sharp as possible around the whole periphery of the prism 79 as it appears in Fig. 8, all of the prism walls, except two, to wit, the cemented face and the hypotenuse face, must converge, Fig. l0, in a point situated on the opposite side of the lens very lnearly in its focal plane. The degree of convergence depending on the focal length of the finder lens ought, therefore, to be different when the rear lens (in case two are used as mentioned below) is removed. But to avoid any such necessity I prefer to make the convergence a little greater than is required for the one lens and a little less than would be best for the combination of the two lenses.

To simplify the explanation, I have so far spoken of the finder as composed of a single lens, but it is evident that it could consist tances. The double lens of the nder serves then with the complete' objective and, when the front of the objective is takenfof to add to the focal length, the second lens of the Where the finder is thus established for two focal lengths, there should necessarily be two distinct and differently inclined planes to oscillate the mirror 0;' oneJc, Fig. l1, which is to be used when the objective and the finder are complete; the other, c, Fig. 11, when they are incomplete. lVhen the finder is composed of ya single lens L, as in Figs. n and 7'", it is better, in order to avoid curvatures of too short radii, to use a biconcave lens. The surface by which prism P is fixed to such a bi-concave lens has then to have a convex curvature corresponding to the concave surface to which it is fixed.

The main advantages of my present invention are: first, 'that the camera may be manipulated as easily as if no focuser were present, either to open it up for use' or to fold it up compactly for transportation;

' secondly, that during the said folding operation the focuser automatically finds its way into a heretofore unused inside rece-ss of the folded up camera; thirdly, that the focuser, when in position of use, does not project laterally with reference to lthe main body of the camera; fourthly, that a positive means is provided for offsetting the apparent path of the movable image inand in any desired degree through and including zero value; ffthly, that the finder image appears as a reduced copy of the original object situated directionally close by such original.

lVhat I claim as my invention and desire to secure by Letters Patent is:

1. As an attachment for cameras, the combination with a lens, of a reflecting prism with tapering sides, cemented thereon, and a second reflector, cooperating with the lens and prism, to forni duplicate images of an obj ect'viewedin the lens.

2. As an attachment for cameras, the comhination with an eccentric d ivergent lens, of

a refiecting prism cemented thereon, and a Vobject, of means for adjusting the lens on an axis perpendicular to the pivot of the pivt oted reflector.

4. As an. attachment for cameras, the combmation with a lens and a reflecting prism cemented thereon and a second reflector pivoted to coperate With the lens and prism in forming two relatively movable images of an obj ect, of means for adjusting the lens on an axis perpendicular to the pivot of the pivoted reflector, and other means for adjusting it on an aXis parallel with such pivot. v

5. The combination with a folding camera and its finder, of automatic means for mutilating the finder image When the camera is out of focus, such means being adapted to automatically open and fold up With the camera.

6. The combination With a camera having a compound objective which may be used whole With short focus or in part With long focus, of a finder having means to change its eldto correspond with that of thel objective.

7 The combination With a camera having a compound objective which may be used` Whole With short focus or in part with long focus, of a finder having means to change its ield to correspond With that of the objective and Without changing the size of the finder image.

Oopiesuf this patent may be obtained for ve cents each, by addressing the focus,

8. The combination with a camera having a compound objective which may be used whole With short focus or in part with long focus, of a iinder comprising two lenses, and means for unmounting one of them so the finder may be used with single lens or With compound lens in the same manneras the camera.

9. The combination with a camera having' a compound objective which may be used Whole with short focus or in part with long of a finder comprising two eccentric lenses, and means for unmounting one of them so the finder may be used with single lens or With compound lens in the same man ner as the camera.

l0. The combination with a camera and its finder, of means for forming the nder image directionally close by the original object and automatic means for mutilating the finder image When the camera image is or would be out of focus.

` JOSEPH BECKER.

Witnesses:

GUY E. PADGETT, GEO. W. PoE.

Commissioner of Patents,

Washington, D. C.

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