USRE21149E - Exposure apparatus fob cameras - Google Patents

Description

July l1, 1939- H. F. TNNIES Re. 21,149

EXPOSURE APPARATUS FOR CAMERAS I Original Filed Nov. 19, 1934 2 Sheetsv-Shee't l July 11, 1939. H. F. TNMES 1 Re. 21,149

EXPOSURE APPARATUS FOR CAMERAS Original Filed NV. 19, 1934 2 Sheets-Sheet 2 Reima! July 111,'193'9 UNITED sTATEs PATENT OFFICE y Original No. 2,051,061, dated- Augnst 18, 1936, Se-

rial No. 753,752, November 19, 1934.

Application for reissue October 24, 1938,- Serial No.

'I'his invention relates to exposure apparatus for cameras, and more particularly to photoelectric apparatus for facilitating the proper exposure of the negative, either by indicating that adjustment of the diaphragm or shutter speed which is appropriate for the light conditions then existing or by automatically making the necessary adjustment.

Objects oi the invention are to provide exposure apparatus for cameras which is of relatively small size and which may be incorporated in or located adjacent the usual lens and-diaphragmassembly with little or no increase in the size of the camera. An object is to provide photoelectric exposure apparatus for cameras which may serve both as an exposure meter and as an automatic diaphragm,.

the. apparatus preferably being so constructed that the exposure meter portion of the apparatus affords a visual indication as to whether or. not the brightness of the scene to be photographed is in excess of that critical value which will permit use of the automatic diaphragm. A further object is to provide photoelectric apparatus for incorporation in a. camera adjacent the usual lens anddiaphragm assembly, the photoelectric apparatus including an electrical measuring vinstrument actuating a plurality of .diaphragm blades, the measuring instrument and blades being so related that the diaphragm blades can not decrease the maxlmum lens opening unless the measured brightness .o of the scene to be photographed exceeds that critic al value for which the maximum lens opening and a predetermined snapshot time of exposure are appropriate. Other objects relate to the provision of exposure apparatus including an elecu trical measuring instrument having a single magnet ic circuit and a plurality of moving systems which carry diaphragm blades, the magnetic circuit being of approximately annular form to permit the mounting of the electrical instrument in the lens and shutter assembly of a camera without substantial increase in the size thereof.

These and other objects and' advantages of the invention will be apparent vfrom the following specification when taken with the accompanying u drawings in which:

Fig. l is a front elevation of a camera provided with photoelectric exposure Aapparatus embodying the invention;

Fig. 2 is a transverse section through the lens 50 and shutter assembly as viewed on line 2-2 of Fig. 3, the automatic diaphragm and exposure meter elements being shown substantially in elevation and thephotosensitive device lbeing shown in central section and turned thr'ough 90 for the 5|' better illustration ofthe electrical connections;

`z4 claims. (ol. eis-s4) Figs. 3 and 4 are respectively a top View and a longitudinal section through lens, shutter and exposure apparatus; l

Fig. 5 is a sectional view, similar to Fig. 2, oi

another form of automatic diaphragm construcl tion;

Fig.- 6 is an enlarged fragmentary View of the moving coil and blade assembly of Fig. 5;

Fig. 'l is a sectional view of another form of the invention;

Fig. 8 is a plan view of a rotary disc calculator;

Figs. 9 and l0 are sectional views of additional embodiments of the invention;

Fig. 11 is a fragmentary vertical section on line II-IIofFig.l0; l

Fig. l2 is a front elevation of an embodiment of the invention in which both the -photosensitive apparatus and the automatic exposure apparatus are incorporated in the lens tube or casing which houses the lenses and shutter `of the camera; and

Fig. 13 is a fragmentary sectional view of a combined automatic and manually adjustablediaphragm. v

In the drawings, the reference numeral I identiies the casing or lens tube which. supports lenses 2, 2' that are carried by the usual ring mountings 3, 3', the casing having a threaded sleeve l or other appropriate `means at its inner end for attaching the casing to a camera 5. In addition to the lenses, the casing houses appropriate mechanism such as shutter 6 and an iris diaphragm I for controlling'the exposure of the negative. The shutter mechanism includes pin 8 which extends to the exterior of the casing and is adjustable along a scale 9 which is graduated in the usual 35 manner to indicate the exposure period for snapshots 'or "instantaneous" exposures, and also the settings for time and bulb exposures. The diaphragm 'I lis similarly provided withl an indicating arm or pointer IIJ which-is displaceable along a 40 graduated scale I I to adjust the effective aperture of the lens system. The mechanism for actuating the shutter and diaphragm is positioned, as is cusparatus for indicating, in terms of time or of lens aperture, a factor which affects the `exposure, and also an automatic diaphragm mechanism. This apparatus is energized by the current -developed by a photocell l2 which may be', and preferably is, of the current-generating type,

` the cell being mounted on the camera body behind means, such as a multiple compartment baffle I3 and multiple lens plate I4, lfor restricting the beam of light rays which reaches the photocell to approximately the image angle of the camera. This type of light restricting means is described and claimed in my copending application Serial No. 728,573, filed June l, 1934, now Patent No. 2,067,843.

As shown in Figs. 2 and 4, the measuring instrument includes two permanent magnets I5 of approximately semi-annular form which YVconstitute a single magnetic circuit with two air gaps in which the moving coils I6, I6' are pivotally mounted. This particular form of magnetic field Structure is of small size and makes it possible to locate the entire assembly within the lens and shutter ycasing I. The field magnets surround the axis of the casing and, obviously, the magnets are arranged with their unlike poles in proximity. The moving system pointer II having a bent end which moves over an indicator plate I8 within the upper portion I9 of the casing, the pointer end moving along and adjacent the inner face of the casing to cooperate with a scale 20 on the exterior surface 0f the projecting circular wall I9 of the casing.

The scale 20 may be graduated in terms of one of the factors, time or diaphragm opening, which affect the exposure and, in Fig. 3, a time scale ranging from 16 seconds to 1;@0 second is illusvtrated.

.knob 23 which extends to the exterior of casing I. When the switch is closed, the moving sys- `tems IB, I6' are displaced in accordancewith the brightness of the scene toward which the camera and the photocell are directed, and the position of the pointer l1 on the scale 20 indicates the appropriate value of one exposure factor when the other exposure factors have definite preselected values. The illustrated time graduations 0f scale 20 correspond, for example, to an lassumed film speedof 20 Scheiner and an assumed maximum diaphragm opening of f3.5. The corresponding graduations of the shutter speed scale 9 and theY exposure meter scale 20 are preferably in axial alinement. The three exposure factors are so re1ated-that, if it is preferred to assume definite values for film speed 'and exposure time, the scale 20 may be graduated in terms of diaphragm openings. As will be described hereinafter, this measurement of the scene brilliancy, in terms of one factor for assumed values of the other factors, may be converted into an equivalent relationship of other `values of the three factors by means of a computer.

' -The measuring apparatus also includes an automatic diaphragm since each moving system I6, I6' has fixed thereto a sickle-shaped diaphragm blade 2l of light material, such as hard rubber, .a molded synthetic resin or a thin blackened.

sheet of brass or aluminum. In the absence of all current supply to the measuring apparatus,

I6 carries av the inner semi-circular edges of the diaphragm blades are radially spaced by a substantial distance from the adjacent edges of the lens assembly. The spacing permits a substantial angular displacement of the moving systems to take place before the effective diaphragm opening is decreased by the movement of the diaphragm blades into the path ofthe light beainbetween the camera lenses. This delay in the reduction ofthe diaphragm opening is necessary for proper operation of an automatic diaphragm since the apparatus must be designed for one predeterminedV exposure period and, obviously, no decrease in the opening must take place until the scene brightness exceeds that critical value which corresponds to a full diaphragm opening and the predetermined exposure time. The illustrated apparatus was designed fora normal snapshot exposure of Q5 second, but it will be apparent that any other value may be selected for the predetermined normal exposure period. Reverting to the indicator plate I8, it will be noted that the plate is divided into two significant areas I8, Ib, preferably of contrasting color, which meet at the 1,455 second graduation on scale 20. .The significance of these regions of plate I8 is that, when the camera is directed towards a scene and the pointer Il fails to move out,of the region ISB, the operator knows that the light is below that critical value which will give a proper exposure of the film when the shutter is Set for the predetermined speed of 1,(35 second. Under such conditions, the indicated longer exposure must be used or, for less than the maximum diaphragm opening, the exposure time must be 4correspondingly increased beyond the indicated value.

The diameter of the lens tube I may be some' what reduced or, alternatively, larger diaphragm openings may be had with the same maximum casing diameter by providing a lost motion conv nection between the'rioving coil system IS and the diaphragm blade 25, Figs. 5 and 6. 'Ihis blade is pivotally mounted with respect to the moving coil I-E and has a slot 26 for receiving the bent end of an arm 2l which is fixed to the moving coil. The moving coil IE which carries the exposure meter pointer II may therefore return to its normal zero current position but this outward movement of 'the diaphragm blade 25 and of 'the moving coil I6 and its blade 24 is arrested by spring stops 2li as soon as the blades have moved to clear the maximum lens opening. The blade 25 is returned to full open position by a coil spring 29 which has its inner end fixed to the moving coil system, the outer end of the blade. The operating characteristics of both moving coil systems are substantially the same;

and the length of the slot 26 in blade 25 issuch si-hat the initial closing movement of both blades takes place when the current supply to the measuring apparatus rises above the critical brightness value which brings the pointer I'I into alineynient with the dividing line between the two regions of the indicator plate I 8.

An alternative vcompact arrangement for ob- 'taining a full range of movement of the coil I5u and pointer I'Iais shown in Fig. 7. lThe upper portion of the casing Ia is enlarged to permit the blade 24a, of the upper moving system I6, to be withdrawn from the lens opening when the measured brightness is below the critical value corresponding to the preselected shutter speed. As in the Fig. 5 construction, the lower moving vanice system It and diaphragm blade ublengage the stop 23* when the blade 24h is clear of the light passage through the lenstube. 'It will be noted that the inner edges of the blades'll,` 241 are delined by three straight lines which form a semihexagonalv recess, the blades thus cooperating to produce a substantially hexagonally shaped openlng which, for optical reasonsis to be preferred when only two blades are employed. Upon increasing vcurrent flow, the moving coil I6u rotates to move blade 24n towards the lens, and both coils and their blades are rotated when the measured brightness exceeds the value for which a decreased diaphragm opening is appropriate.

If the operator wishes to employ a iilm speed and/or a shutter speed which differ from the preselected normal values, the computer .shown in Fig. 8 may be employed to convert the observed reading of scale 2Ilv into other equivalent data. The computer includes the stationary disks 3 I 32 which are marked in terms of diaphragm openings and film speed, and the intermediate disk 33 which has a time or shutter speed scale. The iilm speed value for the type of iilm most commonly used, for example, the value Scheiner, is in line with the maximum lens opening, f3.5,

and the computer is operated by adjusting the disk 33 to bring the observed time reading, as indicated by the pointer I1 and scale 20,i'nto alinement with these selected normal values. The illustrated setting of the computer is correct for an observed reading of 1/5 Second. The alined portions of the several scales then indicate vthe proper exposure data for other iilm speeds and/or smaller diaphragm openings.

' Since this observed reading is more than the selected snapshot setting vof 1/5 second, the operator knows that the automatic shutter blades are not operative to decrease the maximum aperture. When the brightness of the scene is such as to bring the pointer I1 into the region I8h of the indicator plate, the operator may use the normal 1/35 second exposure and the automatic.

diaphragm, or may use any combination of ,stop and shutter speed by first moving switchA arm' 2| to open the electrical circuit. By setting the computer disk 33 to bring the observed time reading, say IAO() second, in line with the corresponding diaphragm opening of f3.5 and 20 lm speed, other combinations of the three exposure factors may be read from the computer disks.

The measurement of brightness values is not necessary when the camera is provided with a shutter having a xed exposure period, as is the case with various types of. motion picture cameras. As shown in Fig. 9, the mechanism includes three permanent magnets I5 forming the eld structure'for the moving coils I6", lid which have diaphragm blades 24|c rigidly fixed thereto. Spring stops 28 engage the blades to arrest the opening movement as soon as the blades pass slightly beyond their maximum opening positions. The moving coilIGc carries a short pointer I'Ic which is concealed by the casing Ic when the blades are fully open, the pointer moving intol view through the window 30 when the scene is of such brightness that the measuring apparatus produces an appreciable closln'g movement of the blades. This' particular form of the invention includes three overlapping blades but it is to be understood that any desired number of blades may be used.

As shown in Figs. 10 andll, are carried bycoil systems 35, that are in axial allnement and pivotally'mounted in the gaps bef desired positions.

l openings.

the blades 34,34'

tween the two sets of pole pieces 36, 38' oi a magnetic field system 31. The direction of current Y iiow through the moving coils is such that the coils turn in opposite directions. The general arrangement is similar to that of Fig. 2 in that the bladesand moving coils are rigidly connected and the yblades therefore have a substantial range of idle. movement before the opening is reduced in size. The-magnet is therefore slotted, as indicated at 33, to permit the necessary outward movement of the blades. When the pin and slot construction of Figs. 5 and 6 is employed, this slotting of the magnet will not be necessary and a single set of pole pieces may be employed.

It will be noted that a separate coil system -39 is provided for theexposure meter pointer 4I). This is an alternative for the described arrangements in which one moving system carries both the pointer and one of the diaphragm blades.

yAn exceedinglycompact arrangement of the exposure meter and automatic diaphragm may be had by mounting the photoelectric cell structure on the outer end of the lens tube or casing I, as shown in Fig. 12. .Thecell and lens plate construction described in my copending application makesl a comparatively thin assembly which4 need'not increase the overall length of the lens tube. The cell and lens plate 4I are of annular form and lie between the front lens ring 3 and the outer edge of the casing I;

Whether or not the diaphragm blades are provided for an automatic control of the diaphragm opening, it` is novel, so far as I am aware, to arrange the measuring apparatus of an electrically actuated exposure meter within a lens tube of the usual design. The advantage of this design is that the moving pointer of the exposure meter travels over a scale that isclosely adjacent the shutter and diaphragm scales. It is therefore to be understood that this invention contemplates a use of the exposure meter elements without the automatic diaphragm blades just as, see Fig. 9, the automatic shutter features may be usually employed whether or not the exposure meter feaf 'combined by providing means for mechanically moving the automatic diaphragm blades into the As shown in Fig. 13, the outer ends of the diaphragm blades 24r1 extend into the path of movement of the lobes 42 which project inwardly from the ring 43 that is rotatable in the lens casing Id. The ring 43 has a pointer 44 which projects through the casing wall to cooperate with a graduated scale, 45, of diaphragm The several illustrated forms of the invention are indicative of the Wide range of latitude in the design and construction of the novel exposure apparatus and it is to be understood that many,

changes may be made in the design, construction and relative location of the various elements without departing from the spirit of my invention as set forth in the following claims.

I claim: d v

1. Exposure apparatus forphotographic `purposes randy of the type including an electrical measuring instrument adapted to be energized by photosensitiye means responsive to the brightness of the sceneto be photographed, characterized by the fact that said apparatus ismounted adjacent the lens of the camera, andk aidinstrument includes indicating means divi ed -into two ranges corresponding to those values of the ISIS brightness of an object to be photographed which lie below and above, respectively, the critical brightness value for which a lm of preselected lm'speed will be properly exposed by a preselected combination of diaphragm opening and shutter speed.

2. Exposure apparatus as claimed in claim 1, wherein said measuring instrument includes a plurality of diaphragm blades for controlling the effective diaphragm opening, said blades restricting the max imum opening only when the bright ness of the object to be photographed exceeds the( said critical value.

3. Exposure apparatus as claimed in claim 1, in combinatipn with an adjustable shutter, an adjustable diaphragm, and means for rendering the measuring instrument inoperative.

4. Exposure apparatus as claimed in claim 1, wherein the photosensitive means is located around the lens at the outer end ofthe lens tube.

5. Exposure apparatus as claimed in claim 1, wherein the electrical instrument comprises a plurality of moving coil systems and a sing] magnetic circuit therefor.

6. In a diaphragm, the combination with a camera lens, a plurality of diaphragm blades for adjusting the eiective lens opening, and measuring apparatus including a plurality of moving coils for actuating said blades, said measuring apparatus being adapted to be energized by photosensitive means responsive to the brightness of the object to be photographed, of means preventing said measuring apparatus from moving Said diaphragm blades into the path oi the light rays passing through said lens until the' current supply to said measuring apparatus rises above a.

critical value corresponding toa predetermined brightness appropriate for a preselected combination of iilmv speed, Speed. V

` '7. A diaphragm as claimed in claim 6, in combination with a pointer actuated by said measuring apparatus anda scale cooperating with said pointer to measure one exposure factor for a prelens opening and shutter Vselected lm speed and preselected value of the other exposure factor.

8. In an automatic diaphragm for a camera lens, an electrical measuring apparatus having a plurality of coil systems, a diaphragm blade carried by each coil system, means mounting `a coil system-for free pivotal movement between a no-current position and a maximum-current position in accordance with the magnitude of the Vcurrent passed through said coil system, means mounting the remaining coil systems for pivotal movement, stop means arresting the opening movement of the diaphragm blades carried. by said remaining coil systems when the saidl blades are clear of the maximum lens opening, a pointer v phragm comprising electrical vmeasuring apparatus adjacent the lens and ,having a plurality of moving coil'systems, a diaphragm blade carriedby each of said coil systems,- a single magnetic'eld system oi said lens and cooperating with all of said coil systems, and a pointer carried by one of said moving coil systems and movable over an indicator plate, said measuring apparatus being adapted to be energized by photosensitive means responsive to thebrightness oi' .the scene to be photographed.

10. The invention as claimed in claim 9, in

combination with manually adjustable diaphragm spondingto ranges of brightness above and below that critical brightness value appropriate for a preselected 'combination` of nlm speed, diaphragm opening and time of exposure.v

i2. The combination withthe lens of 'a camera,'and a casing housing the lens and adapted to be secured to a camera, of an automatic diaphragm comprising electrical measuring apparatus adjacent said lens and' adapted to be energized by photosensitive means responsive to the brightness of the scene to be photographed, said measuring apparatus having a plurality o! moving coil systems each carrying adiaphragm blade, and a single magnetic field system surrounding the axis of said lens and cooperating with all 'of said coil systems, and means 4for preventing operation of said automatic diaphragm.

13. The invention as claimed in claim l2, whereinA said means for preventing-operation of said automatic diaphragm retains the said diaphragm blades in fully opened positions,

14. In an automatic diaphragm, the combination of a casing having spaced lens elements' defining a light passage through the casing,- an electrical measuring apparatus within said casing having a plurality of coils each pivoted on an axis parallel to the axis of the light passage and means forming a single magnetic circuit cooperating with all of said pivoted coils, and

claim 14, v wherein thereY are two diaphragm blades, and the inner edge of each blade is defined by three straight lines that form a semiy hexagonal recess in the blade.

16. An automatic diaphragm as claimed in claim 14, wherein each blade is xed toits associated moving coil, the inner edges of said blades being spaced ,from said light passage 'when said moving coils are not energized. f

17. yAn automatic diaphragm as claimed i claim 14, in combination with an indicator plate,

a pointer carried by one of said moving coils,r

a lost motion connection between the said coil and its blade, and means for 'arresting the opening movement of that blade when it clears the said light passage, the said indicator plate being divided into two signiiicant areas corre-v 15. An automatic diaphragm as claimed in n associated moving coils and that one or said moving coils carries a pointer, said casinghaving a windowopening through which said pointer is visible substantially only when said moving systems are displaced to such extent as to move said diaphragms into said light passage.

19. Photographic apparatus comprising the y combination with a lens tube and a lens having the mounting ring thereof secured to the front end of saidlens tube, of exposure apparatus including a photoelectric cell supported by said tube and rearwardly oi.' the front end thereof.

20. Photographic apparatus comprising the e combination with ,a lens tube housing the lens of a camera, of exposure apparatus and a photoelectric cell supported by and at the front end of said tube; said exposure apparatus including a plurality oi blades adjacent said lens and means energized b y said cell to actuate said blades to restrict the opening through said tube when thebrightness of the object to be photographed exceeds that critical value for which a preselected exposure period is appropriate for a preselected iilm speed andthe maximum open-y instrument includes a movable pointer cooper- 22. An automatic shutter for a camera, comprising a pair of pivoted diaphragm blades, and electrical measuring apparatus for adjusting said blades, the inner edges of said blades having similar semi-hexagonal recesses which cooperate to 5 from a substantially hexagonal opening.

23. Diaphragm apparatus for use with a camera lens, comprising a plurality of diaphragm blades, electrical measuring apparatus including moving coils for actuating said blades, and man- 1o ually adjustable means to set said blades `mechanically to any desired stop opening.

24. Exposure apparatustor photographic purposes and of the type including an electrical measuring instrument adapted to be energized by 15 photosensitive meansrespon'sive to the brightness of the scene to -be photographed, characterized by the fact that said apparatus is mounted adjacent the lens of the camera; and said ating with indicating means including scale divisions corresponding to preselected increments of brightness values and graduated in values of one exposure factor, viz., diaphragm opening or shutter speed, and means dividing said scale 2s divisions into two ranges corresponding to those values of brightness which lie above and below, respectively, the critical brightness value for which one preselected and ilxed exposure period is appropriate for one preselected and xed tllm 30 speed at the maximum diaphragm opening ofthe camera lens.

mms FERDINAND u

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