US2244687A - Art of image formation - Google Patents

Description

June l0, 1941. A. NA GoLDsMiTH Erm.

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Patented June 10, 1941 ART F IMAGE FORMATION Alfred N. Goldsmith and Harry R. Menefee, New York, William Mayer, Larchmont, and Fritz Kastilan, New York, N. Y., assignors to I-R System, Inc., New York, N. Y., a corporation of New York Application June 19, 1937, Serial No. 149,078

39 Claims.

Our invention is an improvement in the art of image formation by which sharp images may be produced on suitable media, (such as a photol chemically sensitized surface, a photo-electrically sensitive apparatus, a ground glass, or the like) by the action of converging light rays which have emanated as diverging rays from objects so positioned relatively to one another and to a lens that that image-forming rays of white light emanating therefrom cannot be coverged to a single plane by heretofore known means. Our invention is particularly applicable to motion picture photography and television where lighting conditions are subject to control.

The leading object of our invention is to form on a photo-chemically or photo-electrically sensitive surface images of substantially equal sharpness from objects having a wide range of separation from a lens in the object space thereof. Further objects of our invention are to render identiilable light ,rays coming from specificl regions of the object space by impressing distinctive characteristics on the several group of rays; and to selectively focus the groups of rays reaching the camera objective and its adjuncts from speciiic regions in the object space, so as to increase the working range, or, if desired, to produce special eilects by shifting the planes of convergence of rays emanating from different regions to image planes oiset axially from their natural positions.

The image plane of an objective lens ris, strictly speaking, conjugate only to a single object plane.

When, however, an objective lens is focused on i circles of confusion of permissible diameter may be f ormed is primarily dependent on the permissible diameter of the circles of confusion in the images of such point source resulting from the use of an objective lens of given focal length and relative aperture. Such diameters should not ordinarily exceed 0.002" (i. e., two-thousandths of an inch) for motion pictures on the illm. The depth of such region is referred to herein as the working range of the lens, and every suchregion may be considered as having a conjugate image plane. Each such conjugate image plane of a diiierentregion is positioned a different distance from the second nodal point of the objective.

The total depth of all of the regions containing objects comprised in a scene constitutes, and is herein referredv to, as the object space" of the objective lens, and when such object space exceeds, in depth parallel to the optical axis, the working range of the lens, it has been heretofore impracticable to produce sharp images-in the same photograph or televised picture of all such objects because actinic rays from all the objects simultaneously activate the entire sensitive surface regardless of the different convergence points of the image rays emanating from the respective objects.

By a sharp image of objects in such a region is meant an image wherein (a) The images of objects in the plane strictly conjugate to the image plane of the objective are as sharply deiined as the'degree of perfection of the optical corrections of the lens will permit; (b) The images of objects in the plane strictly conjugate to the image plane of the objective are uniquely produced and free from overlaid and less sharply defined images;

(c) The images of objects lying near or at the inner and outer boundaries of the region are so sharply defined as to have less than the maximum permissible circles of confusion for the image of points in such objects, and

(d) The degree of correction of the optical errors of the objective is high and according to the state of the art, so that image imperfections resulting from chromatic aberration, spherical aberration, astigmatism, coma, `zonal errors, or ileld curvature and the like are inappreciable according to -good current practice. `Under the above conditions, we shall speak of a region in the object space as being conjugate to the image plane of sharpest focus nf objects within that region, and we shall considethat the image of the said region effectively lies in the said image p lane.

By our improvements, actinic rays of substantial activating amount'l reach the photo-chemically or photo-electric sensitive surface on which an image is to be formed only when the imageforming rays emanating from any object in the object space are converged within circles of confusion of permissible diameter.

It is a primary object of our invention to shift, in a direction approximately parallel tothemselves and to the optical axis, one or more groups of image rays converging toward their respective image planes and emanating from a region in the object space as above defined. By such shifts we are enabled to effect convergence to points in the rays from all the various regions. Conversely, we may shift the plane of the sensitive surface so as l to bring it sequentially into coincidence with each of the respective conjugate image planes of the various regions during the convergence of image rays from a given region at such plane and the exclusion of all other activating rays therefrom. Or we may provide a film having multiple parallel sensitive surfaces corresponding to the different regions and on which surfaces rays from the different regions are selectively caused to converge.

A usual objective lens bends image rays emanating from points of an object in its objectspace, and relatively close to its anterior principal focal point, to convergence points in a plane, in the lens image-space, .lying relatively far from the posterior principal focal point of the lens. Conversely, such lens bends image rays emanating from more distant object points to convergence points in a plane relatively closer to the lens and to its posterior principal focal point.

Converging image rays may be displacedparallel to themselves, and the plane of their convergence points shifted rearwardly without changing their radial relationship to the focal center or to one another, or relative to the radial relationship of the conjugate object points. When a chromatizer is used as hereinafter described, the effect of maintenance of relative radial relationships may be maintained though the radial relationships may be in fact disturbed. Such shifts may be effected by various known optical refracting and reflecting devices, but are most simply effected by interposing in the path of the converging rays an afocal transparent plate. The greater the thickness of the interposed plate, and the higher its refractive index, the further back the plane of the convergence points will be shifted from the lens center or from the former and natural plane of convergence to points of the rays.

By suitably proportioning the thickness of interposed plates, the planes of convergence points of image rays from differently positioned objects in an objectives object-space may be selectively shifted rearwardly different distances and any such plane may be made to lie at the same distance from the center of the lens Without changing the size of the image formed by such image points. So long as the thickness of such interposed plate is less than about one-tenth the focal length of the objective, the optical errors introduced thereby will be small in comparison with those of the objective and may be disregarded. Such thickness is amply sufficient to accomplish the desired shifts when using plates of glasses of available refractiveA index.

Substantially similar shifting of the planes of convergence points of converging image rays may also be effected by devices, such as fiat mirrors, or there may be used mirrors or very weak lenses which are so slightly spherical as no't to materially affect the radial position of any convergence point relative to the optical axis and are coordinated with very exact timing of the regional illuminations. l

Any such device which shifts the convergence points of converging rays rearwardly from the optical center of an objective without changing the image size by materially affecting the radial position of any convergence points relatively to the optical axis of the objective We have designated generically a differential focuser, or, briefly, diffo.

We preferably prevent activation of a sensitive surface by actinic rays which are not converged to points at the plane of such surface by eclipsing or excluding therefrom such non-converged rays. In practice We preferably converge upon a sensitive surface rays emanating from but one region at a time so as to transmit through the objective to the sensitive surface the maximum actinic rays available from each region.

The regional rays of the respective regions are coordinated, by identifying characteristics, with the means for effecting parallel shift of the rays. The identifying characteristics of the rays which we have found most advantageous for the regional distribution and identification thereof are their times of occurrence or periodicity, and their nature or wave-form, including in the latter their color or rate of vibration and their polarity or plane of vibration. The rays, light or illumination defined in the claims as being identifiable or segregatable are characterized by one or more of such attributes, and the claims are to be so understood and interpreted.

The shift parallel to themselves and to the axis of the objective of converging image rays from different regions is preferably effected by their passage through media capable of such displacement in proportion to the distance of the respective regions from the objective, as for instance by the sequential passage of rays from the respective regions through afocal transparent plates of different thicknesses, or indexes of refraction, as, for instance, sheets of optical glass having parallel surfaces.

When characteristics other than periodicity or epoch of the rays are used for identification of a region, a selector, such as a color` filter, or polarization filter, is utilized in synchronism with the ray-shifting means to eclipse rays which it is undesirable to have reach the sensitized surface at a particular instant. Such selector, as well as the diffo coacting therewith, may be either movable or stationary.

For most studio Work, subdivision of the object space into a foreground region, middle foreground region, middle background region andbackground region is sufficient for most practical purposes When a lens of reasonable working range is used, but subdivision of the object space into a greater number of shallower regions may be necessary or desirable when a lens of small working range is used. A greater number of subdivisions of the object space may be desirable or necessary when unusually close or unusually distant objects appear in the object space. Subdivision of the object space into a lesser number of regions is permissible when the Working range of the lens used is relatively great in proportion to the total object space or when it is unnecessary or undesirable to sharply converge to a point or small circle of confusion image rays emanating from a particular plane or region of the object space. For instance, when al1 of the principal objects in an object space are in the close foreground and far background, and the middle grounds are relatively empty, the subdivision of the object space into two regions may be entirely adequate. Conversely, when a lens of longer focal length, narrower angle, and short working range is used to depict a scene having a series of important objects at gradually receding positions, it may be necessary to subdivide the object space into a number of regions substantially equal 'to the objects to be depicted.

Moreover, where vsoft or diffused images of objects in a particular region are desired for special effects, the sensitive surface` may be deliberately exposed to actinic rays emanating from objects that are so positioned that image rays emanating `therefrom are not converged to points or circles of confusion of small diameter at the plane of. the sensitive surface, and the softness of the image may be accentuated by the use of a plate displacing the convergence points far from the sensitive surface. Other component parts of the picture may thus be brought into sharp cona trast witha soft part of the picture regardless of the relative positions of the objects with respect to the objective. For instance, images of objects in the foreground and background may rboth be sharp and the image of objects in the middle ground `as soft as desired in the same picture taken by a single exposure. In short, our methods permit bringing objects in any lor all portions of the object space into focus in the resulting picture. and permits softening or throwing out of focus at will any or `all objects in the object space and to any desired extent; both effects being obtainable and controllable within one and the same picture.

In order that light emanating from objects at widely spaced distances from the objective shall form sharp images in substantially the sameQ plane, it is important that- (a) Light emanating from each region in the object space have an identifying characteristic; (b) There be passed to the im-age plane of the objective only such of' the rays as emanate lfrom a region conjugate` with the image plane or made conjugate therewith by axial displacement of rays from the region to be photographed or televised;

(c) When rays from different regions are permitted to pass through the objective in regular or irregular sequence, and ynot concurrently, the groups of rays that have emanated from different regions and have been vconverged be shifted sequentially parallel to themselves and to the optical axis so that their convergence points all lie in a single plane regardless of'the regions from whichthey originated (d) When a plurality of regions are concurrently illuminated by groups of rays having different vibrationl characteristics, the rays undesired at any given instant be eclipsed by a suit` able selector to exclude undesired rays from the imageplane.

It will thusbe seen that for producing uniformly sharp pictures our invention involves means for discriminating between and selectively passing light from diil'erent -regions to an objective: an objective for converging the rays to convergence points; and means for shifting the convergence points of all the rays to the same plane regardless of the region of origin thereof.

The means for discriminating between and selectively passing the light from different regions to the objective may involve the control of the frequency or time of occurrence or time involve a combination of the control of any combination of these characteristics.

The control of the frequency of occurrence or of time-variation of intensity of illumination in the different regions may be conveniently effected by the interruption or variation of an electric current, or by occulting mechanism, or. by a light beam sweeping mechanism, or by any combination thereof which will eii'ect a desired sequential illumination of the several regions.

The control of the rate of vibration or plane of vibration of the rays passing to the sensitized surface may be conveniently effected by color lters, or by chromatizers (as later defined), or by polarizers and analysersl The means for shifting the convergence points of rays passing to the sensitized surface may be afocal plates proportioned to the desired displacement of the convergence points, orl reecting or refracting elements of diilerent optical power, or chromatizers- Systems effecting discrimination by means of the periodicity of illumination, and effecting the shift of the convergence points by afocal elements, are optically as elcient as ordinary photography during the exposure period for each speciilc region of theg object space and are useable for both black-and- White and color photography, and hence are generally preferable.

All of the systems permit the positioning on the sensitized surface of the convergence points of rays emanating from any region by focusing `the objective inthe usual Way and by shifting the converging rays parallel to themselves and the optical axis and controlling the characteristics of the illumination of the particular region simultaneously. -All of the systems permit bringing spotlight-illuminated areas, e, g., the center of interest, into or out of focus at will by controlof the character of the spotlight illumination and its relationship to the ray-selecting and rayshifting means.

In a preferred exempliflcation, illumination isl furnished by a series of intermittently flashing lamps, such, for instance, as gas or vapor disquency of vibration or plane of vibration when 4 the rays emanating from the different zones differ in` their rates and planes of vibration, or may charge type lamps (e. g., neon-filled or mercuryvapor filled lamps) operating on a suitable voltage, which may be supplied, through a suitable timing mechanism, with brief impulses of unidirectional current or short periods of high-frequency currentl causing brief and intense flashes from the lamp. The primary source of power may, if desired, be connected directly with the timing mechanism, but it is generally preferable to handle at the timing mechanism only low Avoltage and amperages and to utilize the timing mechanism for controlling a trigger device, such as a commutator, vacuum tube amplifier, thyratron, or grid glow tube control, through which the lamp operating current is ultimately controlled.

The coincidence of the points in a single plane is secured by the axial displacement of the plane of convergence points of one or more of the groups, such displacement being along the optical axis and the convergence points of such group retaining substantially the same radial relationship to one another and to the optical axis which the points Would have had if undisplaced. By such axial displacement of one ral" group, the axial spacing is varied between the normal plane of convergence of its points and the plane of convergence points of another group or groups of image forming rays originating at a distance from the objective different from the displaced group,

This 'shifting of the rays of one group moves the image points of such group axially relatively to the plane in which rays emanating from another object are converged by the objective, and by admitting to the sensitized surface only rays from regions conjugate with the image plane or made conjugate thereto by axial displacement of rays, and by excluding all other rays, a uniformly sharp image may be produced regardless of the distances of individual objects from the lens.

Briefly summarized, our objects may be attained by systems characterized (a) By periodic or intermittent regional illumination of the object space and an axial shift of the rays from one or more regions as they are respectively caused to impinge upon the sensitive surface or ground glass, such shift being preferably effected by a rotatable dillo having one or more afocal plates moved across the optical axis and the image-forming light bundles of rays, or by a stationary diffo composed of a plurality of -afocal plates of different power to which light from the respective regions is -admitted through a shutter synchronized with the illumination rperiods and with the respective diio plates.

(b) By occulting or sweeping beams of light which light up the several regions one :after another and by having a movable diffe or a stationary diffe and movableshutter coordinated therewith so as to effect appropriate displacement of one or more groups of rays, depending on the regon illuminated.

(c) By illuminating concurrently different regions of the object space by groups of rays having diiierent planes of vibration, and effecting the axial displacement of the rays of yany group necessary to converge its points on'the sensitized surface, such displacement being elected by a fixed or movable dirlo having one lor more afocal plates, and the rays admitted to any such plate being determined by a fixed or movable selecter synchronized with the diio.

(d) By illuminating concurrently different regions of the object space by groups of rays having different rates of vibration and effecting the axial displacement of the rays of any group necessary to converge its points on the sensitized surface. Such displacement may be effected l. By a fixed or movable diffe having `one or Vmore afocal plates and the rays admitted to any such plate being determined by a fixed or movable selector synchronized with the diffo, or

2. By a fixed diffo consisting of a chromatizer" which automatically and simultaneously vbends the rays of differently colored light concurrently admitted thereto; the color of the lighting of the several regions being so arranged that the yangle of bend of that colored ray Iby the chromatizer compensates for the difference in distances 4of the regions and brings all the rays to convergence points in one plane. In this system, the angular relationships naturally prevailing between converging rays of different colors are varied by the chromatizer so that the effect of maintaining a constant radial relationship -between the convergence points is secured notwithstanding the variations effected in the angularity of the rays themselves relative to the optical axis.

The characteristic features and advantages of our improvements will further appear from the following description and the `accompanying drawings in illustration thereof. I

In the drawings,

Fig. 1 is a diagram-matic view illustrating the layout of a stage or set having thereon objects in regions differently spaced from the camcra and adapted to be photographed by aca-mera in accordance with our invention;

Fig. 1A is a diagrammatic view illustrating the eii'ect on the size of the circles -of confusion of focusing the camera on objects in the various regions of the set in accordance with previous practices;

Fig. 1B is a diagrammatic illustration of the effect on the sizeof the -circles of confusion in images of objects throughout the set when the pictures are taken in accordance with our invention;

Fig. 2 is a diagrammatic view illustrating graphically a layout and apparatus for the practice of our invention by a system characterized by periodic regional illumination;

Fig. 3 is a diagrammatic front elevation showing the arrangement of the objective, diiio, and iilm exposure aperture of the camera shown in Fig. 1, the camera casing'being removed;

Fig. 4 is a View of a further developed and modied form of camera and lighting mechanism for practicing our invention by a system characterized by periodic regional illumination;

Fig. 5 is a transverse sectional view of the lighting control mechanism shown in Fig. 4;

Fig. 6 is a front elevation, with parts broken away, of the camera shown in Fig. 4;

Figs 7 to 12, inclusive, illustrate diagrammattically a set having objects thereon in different regions, theimages which are individually made in sequence by such objects, and the composite picture of such objects made inaccordance with our invention when using a system characterized by periodic regional illumination;

Fig. 13 is 4a perspective diagrammatic view illustrating the practice of our invention with a set illuminated by occulted or sweeping rays;

Fig. 14 is -a longitudinal sectional view of a lamp and lamp mounting suitable for use in various illuminating systems involved in the practice of our invention;

Fig. l5 is a transverse sectional view taken on the line I5--I5 of Fig. 14;

Fig. 16 is a diagrammatic view illustrating the practice ofour invention with a lighting system illuminating different regions by individually occulted or sweeping lamps;

Fig. 17 is a diagrammatic view illustrating the practice of our invention by a lighting system having a single source of illumination and sweeping the rays over the set by -a movable reflector;

Fig. 18 is a front elevation of a modified form gf diffo adapted for use in practicing our invenion;

Fig. 19 is a sectional view of the diifo shown in Fig. 18 taken -on the line IB-IB of Fig. 18.

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Fig. is a fragmentary sectional view of a pair of dilo plates taken onthe line 23-20 of Fig. 19;

Fig. 21 lis a front elevation of a modied form of diifo adapted for coaction with movable shutter shown in Fig. 22;

Fig. 22 is a front elevation of a rotatable shutter for use with the stationary diffo plate of Fig. 21;

Fig. 23 is a diagrammatic view illustrating the arrangement of the dillo and shutter shown in Figs. 21 and 22 with an objective lens;

' Fig, 24 is a front elevation of a. modified i'orm of diilo having plates of differentlgwidths;

Fig. 25 is a front elevation of a modied formof diio having plates of varying light-transmitting capacity;

Fig. 26 is a diagrammatic layout illustrating the practice -of our invention where the object space has regions illuminated by rays having different planes of vibration;

Fig. 27 shows diagrammatically the arrangement of polarity analyzers, objective, dillo, and sensitized surface for forming images of objects on a set illuminated by polarized light, as shown in Fig. 26;

Fig. 28 is a front elevation of the ditto sho in Fig. 27;

Fig. 29 is a front elevation lyzer shown in Fig. 27;

Fig. 30 shows diagrammatically a further arrangement of objective, analyzer, dillo and sensitized surface by which there may be photoof the polarity analgraphed a set illuminated by polarized light, as

shown in Fig. 26;

Fig. 31 is a front elevation of the dillo shown in Fig. 30;

Fig. 32 is a Lfront elevation of the analyzer shown in Fig. 30;

lig. 33 is a front elevation of a modied diffo; an

Fig. 34 is a front elevation of a modied' analyzer, which may be respectively substituted for the diffo andanalyzer shown in Fig. 30;

Fig. 35 is a perspective view illustrating the practice ofour invention for photographing a set illuminated by rays having diiler'ent rates of vibration;

Fig. 36 is a diagrammatic layout of color filter, objective and diffo for photographing objects on a set illuminated' as shown in Fig. 35;

Figs. 37 and 38 are front elevations, respecgi/ely, of the diffo and color lter shown in Fig;

Fig. 39 is a diagrammatic view illustrating a phenomenon involved in the practice of our invention by means involving chromati/zers;

Fig. 40 is a diagrammatic view illustrating a further phenomenon availed of in the vpractice of our invention by means of chromatizers;

Fig. 41 is a diagrammatic illustration showing how the phenomena illustrated in Figs. 39 and 40 coact in the practice of our invention by means of chromatizers; v

Fig. 42 shows diagrammatically the arrangement of a chromatizer, objective and sensitized surface involved in the practice hof our invention by means of chromatizers; and

Fig. 43 is an enlarged view of the chromatizer shown in Fig. 42 and the paths of rays passing therethrough.

Fig. 44 is a diagrammatic view illustrating an adaptation of our invention in conjunction with multi-layer lm, thedistances and parts being shown out of proportion for the sake of clearness.

For convenience and simplicity we herein i1- lustrate and describe an embodiment of our invention involving the use of a motion picture camera, but it will be understood that the transmitter of tele I'ision apparatus may be used in lieu of the photo-chemically sensitive surface of the camera.

As illustrated in the drawings, a motion picture I camera I contains supports for a lm having a sensitized surface 2 in the image-space of an objective 3 whose object space comprehends the stage or set 4, which may be deemed to consist of the foreground region 5, the middle foreground region 6, the middle background region I and the background region 8. If desired, the rear of the set may consist of a translucent screen 9, on which may be projected from the rear a. scene or action complementary to the scene or action in the object space 4.

lamps having gas-filled bulbs through which a high voltage current is discharged controllably 3 at specified times so as to produce a number of flashes per second, each flash being in general of but a few tens of micro-seconds duration but ofhigh lumen output per flash. For instance, we may utilize (Illustratively) lamps making 24 flashes of light per second, each ilash of approximately ten micro-seconds duration and a `luminous output of about 83,000,000 lumens during the ash, equal to about 830 lumen-seconds output per ash. Generally, however, it is preferable to use lamps making 48 flashes per second and have the sensitized surface exposed only during alternate flashes of each lamp.

The light from each lamp is concentrated as much as possible in the region to which the lamp appertains, as for instance, by means of reflectors I4, I5, I6 and I1. i`

The'lights I0, II, I2 and I3 may be flashed one after another in sequence by connecting them in circuits under the control of contacts as illustrated diagrammatically in Fig. 2.

As graphically illustrated in Fig. 2, a synchronous motor I8 may be connected by the conductors I9 and I9 in circuit with the motor I8a. for operating the camera I. The synchronous motor I8 has connected. therewith an insulated shaft 20 having fixed thereto a commutator ring 2I electrically connected with the commutator ring segment 2Ia; a commutator ring 22 electrically connected with the commutator ring s egment"22a`; a commutator ring 23 electrically connected with the commutator ring segment 23a' posite terminals of the lamps Il), II, I2 and I3 are electrically connected through the .brushes 2lb, 22h, 23h and 24h with the commutator rings 2|, 22, 23, and 24. When the camera is operated by its motor I8a, the motor I8 in synchronism therewith rotates the shaft 20 so as to bring the segments 2Ia, 22a, 23a and 24a into contact, one after another, with the brush 25 so as to supply current to the lamps I0, II, I2 and I3 one after another to effect the flashing of these lamps in sequence. An additional portable lamp I' may have one of its terminals electrically connected with the source 26 and its other terminal connected through a portable conductor 21 with any one of the brushes 2lb, 22h, 23h or 24h depending on whether'the portable lamp is used for a spotlight in the regions 5, 6, 'I or 8.

Commutator rings and brushes are preferably so operated relatively to the operation of the camera. shutter as to complete the circuits effecting the ashing of each of the lamps sequentially during the period that the shutter of the camera is open for the exposure of a single image frame, so that an image of the objects in each of the regions 5, 6, 1 and 8 may be made on the sensitized surface of the film as such objects are illuminated by the respective flashes of the lamps. It may, however, for certain purposes be desirable to imprint the images of the objects illuminated by each flash on a. different section or frame of the sensitized film.

It is obvious that the convergence points of the rays emanating from the different regions 5, 6, 1 and 8 during the illumination thereof by the respective flashes would ordinarily lie in different planes after passing through the objective 3, since each region would have its complementary image plane. But by our improvements the convergence points are shifted by displacing the converging rays parallel to themselves and to the optical axis of the objective proportionately to the distances between the image planes naturally conjugate to the respective regions.

This displacement of the convergence points may be effected (Figs. 2 and 3) by means of afocal transparent plates 28, 29, 30 and 3| having thicknesses proportionate to the requisite displacements necessary to 'bring the convergence points all in the same plane normal to the optical axis regardless of the region from which the rays emanate. These plates are so coordinated with the timing of the lamp circuits that each lamp flashes when its complementary afocal transparent plate is substantially centered in the optical axis of the objective, due leeway in position being allowed in the design.

The positioning of the afocal transparent plates may be conveniently effected by mounting them in a. disc 32 which may be ythe shutter of the camera or may be a separate disc so positioned that the segment thereof containing the afocal plates coincides with the opening ofthe camera shutter. 'Ihe shaft 20a carrying the disc 32 is rotated by the motor IBa'in synchronous relation with the rotation of the shaft 20 by the motor IBa.

By suitably adjusting the brushes 2 Ib, 22h, 23D and 2lb the relative positions of motor shafts may be readily coordinated to produce a. ash of the desired lamp when the center of its complementary afocal plate is in the optical axis. Hence the rays emanating from objects in the region villuminated by the flash of the lamp are displaced, after passing through the objective, so that the convergence point-s` of such rays are shifted from the plane in which they would fall as a result of the action of the objective alone into a plane coincident with .the exposed sensitized surface 2 of the film.

It is, of course, quite possible to focus the objective so that the rays from one of the regions will be converged by the objective directly in the sensitized surface plane, but this may necessitate the use of an undesirably thin afocal plate for displacing the converging points from some or all the remaining regions and may also render difficult the dynamic balancing of the disk carrying the afocal plates.V Hence, for practical reasons, it is generally desirable to provide afocal plates for each of the regions, and in the absence of the afocal plates none of the rays emanating from objects in the object space are sharply converged on the sensitized surface plane.

While, for simplicity of illustration, we have shown a single lamp illuminating each region, it will be understood that there will be concentrated on each region the rays from as many lamps as are necessary to give the desired intensity of lighting to that particular region, and that the lamps of -a particular region may be flashed simultaneously, or may be flashed sequentially during the period when the afocal plate complementary to that particular region lies in the optical axis. Such sequential flashing of a number of lamps in a region while its complementary afocal plate is in the optical axis merely involves a multiplication of timing contact devices so as -to provide an individual control for each lamp 1n properly timed relation to the movement of the afocal plate or any equivalent electro-mechanical timing device.

Where the spotlight I0' is to be maintained upon a person or center of interest moving through the different regions of the object space, one terminal of such spotlight may be permanently connected to thelsource of current and the other terminal' of the spotlight brought into contact, manually or mechanically, with the respective brushes, complementary to the region in which the center of interest is at the moment, so that the spotlighrt; will be flashed in synchronism with the afocal plate appropriate to the region occupied. The flashing spotlight III' may be conveniently mounted upon a usual but heavier form of swivel microphone boom 33. One of the terminals of such spotlight is connected permanently with the source of current and the other terminal of such spotlight may be connected through a conductor 34 with a contact 35 near the swivel bearing and which makes lighting contact, as the boom is moved, with the contact plates 36, 31, 38 and 39 connected with the respective brushes 2Ib, 22h, 23h and 2lb. As the boom carries the spotlighlt from one region to another, the source of current for flashing the light is shifted from one brush to another, so that correct synchronization between the flashes and the afocal plates is constantly maintained. If the spotlight is kept in one position but tilted and rotated to follow the center of interest, the correct synchronization between the flashes and the afocal plates can similarly be maintained either manually or by a suitable contactor assembly.

Instead of controlling the flash of the lamps in synchronism with the complementary plaltes of a diilo 'by a separate timing device synchronously driven in appropriate timed relationship to the camera shutter and diffe, as above described, the timer may be mounted as an integral part of the camera structure, and the film feeding mechanism, the diffo mechanism and the of objectives 3 may be brought into alignment with the aperture Ia (Fig. 6). A usual camera drive shaft Ib has fixed thereto, in lieu of the usual shutter for controlling the aperture la, the difi'o disk 32' containing the afocal plates 28', 28', 38' and 3 I lwhich are moved sequentially past the aperture la behind the objective 3.

The shaft Ib acts through suitable gearing upon the film sprocket 48 to feed the nlm 4I step by step past the lm gate 42 so that the film is stationary during the passage of the plates 28', 28', 38' and 3|' past the aperture la. A bracket 43 is xed to the camera casing and supports an electric motor 44 and a flash timer 45 having a shafit 48 coupled to the motor shaft and to the camera shaft Ib.

The shaft 46 has mounted thereon a series `of insumed cams 41 (Fig. 5), each of which is adapted to engage'and rock one of a series of contact vibrators 48 mounted on insulating shoes 48 which are adjustable around yokes age current, such as a battery 5I, (Fig. 4) has one of its poles connected by suitable conductors wiith terminals 48a, 4812 48c and 48d of the respective vibrators 48. The complementary terd minals 48a', 48h', 48e and 48d' are respectively connected with low tension windings of ignition coils 52a, 52h, 52e and 52d, which also have connected therewith spark gap condensers connected with the battery 5I. 'I'he high tension windings of 'the ignition coils 52a, 52h, 52e and 52d are connected through suitable conductors with the vapor lamps I8, II, I2 and I3, which have suitable condensers and bleeder resistances 53 in parallel and grounded surge resistances 54 connected therewith.'

'Ihe foregoing timing mechanism closes tickler circuits of the lamps I8, II, I2 and I3 so as to cause flashing of the lamps by currenit supplied from a high voltage source, such as a central station, from which alternating current ows through the conductors 55 and 58 through the plate transformers 51 and lament transformers 68 of suitably grounded rectifier tubes to provide the high voltage DC current through the conductors 58a, 58h, 58e and 58d to charge the condensers which operate the vapor lamps `enlciently in flashes.

The number of vibrator contacts andcircuits controlled thereby will of course be varied to lconform with the numberof the regions into which the object space of the `objective 43 is`to be divided, and the blocks 48 will be so ad- 'justed angularly that the flash of eachlamp will objective 3 is capable of phtographing without the formation of circles of confusion of objectionable size, the composite picture formed by ithe rays emanating in sequence from the several regions'wili be formed entirelyl by the action of rays converged to points or at least converged within the circles of confusion of unobjectionable size.

The difference in the relative sizes of the circles of confusion in images of objectpoints in the object space when the rays from all such objects are simultaneously converged by an objective and the relative sizes of the circles of confusion, where the images of the object points in the object space are made in accordance with our invention, is diagrammatically vand graphically illustrated in Figs. 1A and 1B.

If it be assumed that the objective 3, at a certain working speed or relative aperture, be focused in Fig. 1 so that. the sensitized surface of the film is in a plane conjugate to a plane 88' ,in the foreground region 5, and that the object space is constantly. and uniformly illuminated, then the graph 6I, (the curved shape of which resembles a skewed parabola) indicates the increasing size of the circles of confusion formed by rays emanating from objects in front of or behindthe plane 68. The objects in the plane 68 will form circles of confusion of minimum diameter, corresponding,` presumably, to a sharply dened image, and which minimum diameter may be deemed to correspond to the distance'between the nadir 62 and the point- 63. As the distance of the object from the plane 68 increases or diminishes, the diameters of the corresponding circles of confusion increase toward an arbitrarily selected maximum, which ,should preferably not exceed .002 inch for images on motion picture film, and which may be indicated by the distances 62-.64. 'Ihe distance between the upper ends 88 and 66 of the legs of the parabolic-shaped graph at the height of the point 64 is indicative of the region or working range of the lens 3 lwithin which objects will generate images containing circles of confusion within the permissible limit.

Objects beyond the working range of the lens.

will be too soft," or out of focus, to be tolerable.

If the objective be focused on objects in the plane 18 in the middle foreground region 6, then the distance between the upper ends 1I and 12 of the parabolic graph 13 will be indicative of the region or working range of the lensV when so focused and within which working range objects will generate images containing circles of confusion within the permissible limit. In this case the objects that are in exact focus will form images having circles of confgusion of minimum diameter slightly smaller than is the case with objects ln the plane 88 when the objective is focused on the plane 88.

If the objective be focused on objects in the plane 88 in the middle background 1, the distance between the upper ends 8| and 82 ofthe parabolic graph 83 will be indicative of the region or working range of the lens when so focused, and within such range objects will generate images containing circles of confusion within the permissible limit and the smallest circles of confusion generated will be smaller than any circles of confusion generated when the lens is focused on and the projection of thisv graph beyond the background itself is indicative of the region or working range of the lens when so focused. Objects Within such working range will generate images containing circles of confusion within the permissible limit and the smallest circles of confusion will be smaller than the minimum size of any circles of confusion generated by the objective when focused on the planes 60, 'I0 or 80. It will, of course, be understood that if the background did not obstruct the object space, images would also bel formed with permissible circles of confusion from objects between the background and the far end of the parabolic curve 92.

It will be noted from the parabolic curves that the objective 3 has a lesser working range in front of a plane of sharpest focus than behind a plane of sharpest focus for each setting of the lens, and that the curves become of sharper minima, and hence indicative of less working range of the lens, as the plane of focus approaches the lens, and that the minimum realizable circle of confusion and the greatest Working range is obtained by sharp focusing on a plane toward the background. But regardless of the 'plane on which the objective is focused, it is impossible to secure an image having permissible circles of confusion of objects spaced over the entire object space in the case illustrated. Hence it is impossible in this case, with any one setting of the objective alone, to obtain desired results of forming images with satisfactory sharpness (reduced diameter of circles of confusion in the image) over the entire set from foreground to background.

In Fig. 1B we have indicated graphically the effect of our improvements upon the working range of the lens and the diameter of the circles of confusion formed on the sensitized surface from rays emanating from anywhere within the object space. In this figure the full line curve indicates the approximate performance of our improved system when the illumination of the regions by the flashing lamps and the displacement of the convergence points of the image rays by the afocal plates are properly coordinated. The maximum permissible diameters of the circles of confusion are indicated by the position of the line |0I. The objective 3 will be focused so that rays emanating from objects in the plane 60 will be converged at points in a plane in front of the sensitized lni surface a distance equal to the displacement power of the thinnest afocal transparent plate 28. With the lens so focused and the foreground illuminated, the, convergence points of rays emanating from objects in the foreground region will be displaced rearwardly so that they fall on the sensitized surface or suf- `iiciently close thereto to form circles of confusion of lesser diameter than the maximum permissible. The next thicker afocal transparent plate 29 has`a displacement powerequal to the distance between the plane of the sensitized film surface and the plane in which the objective 3 (without further adjustment) converges to points, rays emanating from objects in the middle foreground region 6. Hence when the middle foreground 6 is illluminated and the afocal transparent plate 29 interposed in the path of the converging rays, the convergence points of such rays will be shifted rearwardly into coincidence with the plane of the sensitized surf-ace, or so close `thereto that the circles of confusion formed will be of less diameter than the maximum permissible. The next thicker afocal transparent plate 30 has a displacement power equal to the distance between the sensitized film surface and the plane in which rays emanating from the middle background region 1 are normally converged by the objective 3 without further adjustment. Hence when the middle background region I is illuminated and the afocal transparent plate 30 is interposed in the optical path, the convergence points of rays emanating from the region 1 will be shifted backward into coincidence with the plane of the sensitized film surface or so close thereto that the circles of confusion formed thereby will be of less diameter than the permissible maximum.

The next thickest afocal transparent plate 3| has a displacement power equal to the distance between the sensitized film surface and the plane in which the objective 3 without further adjustment normally converges to points the rays emanating from objects in the background region 8. Hence when the background region 0 is illuminated and the afocal transparent plate 3| is positioned in the optical axis, the plane in which the rays emanating from the region 8 are converged to points by the objective 3 is shifted rearwardly into coincidence with the sensitized film surface or so close thereto that the circles of confusion formed thereby are of less diameter than the permissible maximum.

Since the ash of the front lamp |0 illuminates only the foreground region y5 to an intensity sufficient to photographically activate the particular sensitive film employed, all or substantially all of the rays passing throughthe objective 3 and plate 20 will be converged sufficiently close to the sensitized surface that the diameters of the circles of confusion will all be less than the permissible maximum and will vary only in proportion to the spacing of objects within the normal working range of the objective 3, as illustrated by the first loop of the graph |00.

'I'he flash of the lamp will illuminate only the region 6 to an intensity suiiicient to photographically activate the particular sensitive film employed, the rays therefrompassing through the objective 3 and the plate 29 will likewise be converged to points in a plane substantially coincident with the plane of the sensitivev film surface, or so close thereto that the diameters of the circles of confusion will vary only in proportion to the spacing of objects within the normal working range of the objective 3 at the distance of the region 6, as illustrated by the second loop of the graph |00.

The flash of the lamp |2 illuminates only the region 'I to an intensity suicient to photographically activate the sensitive iilm surface and hence rays passing through the objective 3 and plate 30 are converged to points in a plane substantially coincident with the sensitive film surface and the diameters of the circles of confusion vary only in proportion to the spacing between objects within the normal working range of the objective 3 at the distance of the region 1, as illustrated by the third loop of the graph |00.

The flash of the lamp I3 illuminates only the background region 8 to an intensity sufficient to `photographically activate the particular sensitive film employed. Hence rays passing through the objective 3 and the plate 3| are converged to points in a plane substantially coincidentwith the sensitive film surface, andthe diameters of the circles of confusion formed thereby vary only in proportion to the spacing of objects within the normal working range of the objective 3 at Ille dktance of the region I, as illustrated by the fourth loop of the graph III.

It will be noticed that the upper points of innection of the graph -Ill have been shown slightly above the crossing points of the dotted line curves BI, 13, Il and i! illustrating the re- `spective working ranges of the objective I alone at the various regional distances. 'Ihls is so shown because there may be a certain amount of spillover of light between the adjacent regions, but such spillover may be so limited as to keep the apices of the graph Il., -at all studio distances from the lens, below the maximum circle of confusion limit indicated by the line IOI.

It will thus be seen that by oui invention there 1 is provided an optical system of universal working range for the object space or within the region of suitably controlled illumination and that an image Aof each object is imprinted on the sensitized surface by rays that converge to DOints substantially in the plane of such sensitiaed surface regardless of the positions of the v objects themselves.

If, for instance, as shown in Fig. '1, the object space contains the objects III, i, III and III in the respective regions I, i, 1 and l, the flash of the lamp il will imprint on the sensitive surface a sharp image of the object Ill as shown in Pig. 8. leaving .the remainder of the sensitive surface unactivated; the flash of the lamp II will imprint on the sensitized surface an image of the unobscured portion of the object |09, as shown in Fig. 9, without further activating the area containing the image of the object I" and without activating the, remainder of the. sensitive surface: the ash of the lamp I! will imprint "on the sensitive surface an image of the unobstructed portion of the`.object III, as shown in Fig. 10, without further activating the areas occupied by the images of the objects Ill, Ils), and without activating the remainder of the sensitive cuit which supplies current thereto continuously so that the light is constant. In the embodiment illustrated, each of the lamps IIia, IIa, Ila and Ila is moimted in aframe or bracket III, and the framework has fixed bearings IIZ and Iii on which antifrictionally supported bearings I Il and I I6 rotate. A parabolic, elliptic, or cylindrical reilector IIB is mounted on the bearings I Il, I I5 with the filament of the lamp in approximately the focal line of the reilector.

An opaque housing II'I is also mounted on the bearings III, III, and' supports asemi-cylindrical condenser' lens `I I8 which concentrates the total emitted light into a narrow beam or sheet of the desired dimensions. The frame III may be provided with adjustably hinged shutters H9, by the surface; and the flash of the lamp Ilrwill imprint on the sensitive surface an image shown in Fig. l1 of the unobscured portion of the object III without iurther`activating the areas occu- Died by the images of the objects Ill; I and III. Hence the developed illm will show, as illustrated in Iiig.l l2, a composite image of all of the objects, and each portion of the composite image will be sharp.

Periodical regional illumination by occulted rays In lieu of or tc supplement the periodic regional illuminationby flashes of intermittent light, we

may periodically illuminate the regionsl, 8, 1 and I in timed relation to the convergence points displacer or diffo" by means of a source of constant illumination whose rays sweep as a narrow beam in a regular or irregular sequential order conforming to the order of the diil'o'l elements.

For instance-as shown in Fig. 13, we may pro-` Each illuminant may-consist of a high eillciency incandescent lamp of the linear illament type, as illustrated in Figs. 14 andA 15, and each lamp may have its terminals connected in a cirand 3l, as, yfor instance, by Synchronous motors III fed from the samealternating current sourcesy as the synchronous motor Ila for actuating the driving mechanism of the diil'o plate and camera.

It will be understood that, as the casing I I1 and parts connected therewith are rotated with the shutters II9 retracted to provide an adequate opening, the sheets of light emanating from the lenses `I I8 sweep -over thefspt so as to illuminate the regions 5, 6, 'I and 8 one after another as the afocal plates 2l, 29, ll and 3| move across the optical axis of the objective. Hence the objects in the respective regions are illuminated to photographic intensity coincidentallywith the positloning -of the respective afocal plates to displace the planes of the convergence points normally conjugate with such @regions to the plane of the sensitized nlm surface.

Instead of sweeping sheets of light the. depth ofthe set, as above described, a series of lamps Illa',

IIa', Ila' and Naf, similar to the lamps Ilia, Ila,

slit, so that the at beam from each` lamp Ilia',

IIa', Ila' and i3d' will illuminate only the zcne to which such lamp is appurtenant. In such set up, the housings II'I and the lenses IIB will be initially so adjusted angularly relative to one another that the rotation of the lenses III will cause the illumination of the region by one lamp to be discontinued as or before the illumination of the next region by its lamp commences.

If desired, supplementary lamps I0", provided with the shielding `and operating mechanisms above described, may be disposed in any region and the eirulgence of light therefrom so timed as to synchronize with the position of the afocal plate which is complementary to the region illuminated by such lamp or lamps I Il".

In some cases the light from a single lamp may suillce when the light therefrom is swept over the set in the manner described in connection with Figs. 13, 14 and 15, or, is shown in Fig. 17, the light from a single reversed lamp Ilial may be swept across the set so as to illuminate 'the several regions to photographic intensity, one at a time, by means of a reilector, such, for instance, as a rotating polygonal reflector |23 through suitable gearing by a synchronous motor |24 lin timed relation to the movement of the driven

Images