US2318616A - Light control mechanism - Google Patents

Description

May 1l, 1943. A. L. MAYl-:R ErAL LIGHT CONTROL MECHANISM med Nav. 14. 1940 Patented May 11, 1943 LIGHT CONTROL MECHANISM Alvin L. Mayer, Cincinnati,

Kossman,

Ohio, and Hans R.

New York, N. Y.; said Kossman assignor to sai-d Mayer Application November 14, 1940, Serial No. 365,677

3 Claims.

This invention relates generally to photographic equipment, and more particularly to a means for controlling and standardizing the intensity of a beam of projected light, such as used in photographic projection.

An object of the present invention is to provide simple mechanical means for enabling an operator to accurately and expeditiously adapt or standardize the intensity of a projected beam to the particular negative being printed, in accordance with its individual density.

Another object of the invention is to provide, in a photographic printing and enlarging machine, means for enabling an operator to preview the projected. negative in its entirety prior to the actual printing exposure, and to simultaneously therewtih observe the actual recorded intensity of the projected negative at the locus of preview.

A further object of the invention is to prolvide means for directly measuring the intensity of the projection beam.

Still a further object of the invention is to provide means of the character stated which are inexpensive and durable, yet exceedingly accurate.

These and other objects are attained by the means described herein and disclosed in the accompanying drawing, in which:

Fig. 1 is a side view of a commercial printing and enlarging machine embodying the presenti invention, with parts thereof being cut away for clarity of detail.

Fig. 2 isA a sectional View on line 2-2 of Fig. 1.

Fig. 3 is a sectional view'on line 3 3 of Fig.v l.

As disclosed in Fig. l the numeral I0 indicates the bed or frame of the printing and enlarging device, which may be supported upon leg standards I!. A projector I2 including a constant source of illumination, such as electric lamp I3, is mounted upon the left end of the bed for projecting the images of photographic negatives, placed laterally in nlm gate I4, through projection lens I5. Means are disposed at the right end of the vleed onto which the image of a negative is projected from projector I2, Such means in its simplest form, may comprise, for the purpose of the present invention, a sensitized photographie paper support I6 including a paper gate I1. or the like. into which a sheet of sensitized paper may be laterally disposed while a print is being made.

A so-called projection screen or preview door I! may be pivotally mounted relative to the paper support i8 by means of hinges I9, or the like. Screen I8 is normally urged, by suitable means not illustrated, to the closed position indicated in Fig. 1 for normally precluding projection of light onto the sensitized paper mounted in gate I1.

Suitable means are provided for swinging screen I8 about its vertical axis for the purpose of uncovering or exposing, the sensitized paper mounted therebehind. Such screen actuating means may comprise a screen actuator lever 20, one end of which is fastened relative to screen I8 as at the lower hinge I9. 'I'he free end of lever 20. may be connected by means of a cable 2l, or the like, to the upper end of arm 22, the lower end of which is carried by and secured to rock shaft 23. Cable 2| is shown passing over pulley 24 which may be suitably mounted to bed IU. As clearly disclosed in Fig. 2, screen I8 will be swung from its closed position to the open position, denoted by the broken lines, as rock shaft 23 is turned in a clockwise direction.

It should be understood that the means hereinabove described for actuating screen I8 are merely exemplary in nature, and, if desired, any other screen actuating mechanism may be used, such as, by way of example, the mechanism disclosed in U, S. patent issued to A. L. Mayer on February 8, 1938, No. 2,107,867. The present invention is not directed to, nor concerned with the specific details of the particular screen actuating means employed.

It will be observed that with screen I8 normallyV closed the projected image bearing beam is adapted to first fall upon the outer surface of screen I8 for enabling an operator to observe the outline of the projected image before exposing the sensitized paper to the projected image bearing beam.

In order to ascertain the intensity ofthe projected image bearing beam at the approximate location of the sensitized paper, light sensitive means such as, by way of example, a photo electric cell 25, or the like, may be mounted centrally of screen I8. The light sensitive cell 25 may be wired to a suitable current measuring instrument, or meter 26, by means of conductors 21 and 28.

From the foregoing it is obvious that the actual intensity of an image-bearing-beam of projected light will be indicated on meter 26 during those periods of time when screen I8 and the light sensitive cell 25 are disposed directly in the projection field of lens I5.

In order to adapted the intensity of the projected beam to the particular negative being projected in accordance to its individual density, and in order to establish a projection beam having a so-called standard intensity which is of such a magnittude as to prini-I the densest printable negative disposed in gate I4 of projector I2, a diaphragm 29 may be provided for selectively controlling the effective aperture size of projection lens I5. As disclosed in Figs. 1 and 2 diaphragm 29 may comprise a plate, the lower end of which may be carried by and secured to rock shaft 30 in such a manner as to cause the upper apertured portion 3I, see Fig. 3, to progressively reduce the effective aperture size of lens I as said plate is moved in a clockwise direction about the axis of shaft 30. As disclosed in Fig. 1 diaphragm 29 is preferably disposedbetween lens I5 and the shutter mechanism, denoted generally by the numeral 32'.

In order to coordinate the effective aperture size of projection lens I5 with the actual intensity of the projected image-bearing-beam, as recorded on meter 25, means are provided for translating the reading of meter 26 to a reading on diaphragm dial 33, which latter reading is a definite predetermined function of the reading of the light meter 26.

Rock shaft may be operatively connected to a diaphragm pointer 35 which is adapted to' sweep diaphragm dialY 33 as diaphragm 29 is moved relative to projection lens I5.

The calibration of the diaphragm dial 33 are established relative to, and are a function of, the calibrations of the Ylight meter dial 34, whereby the effective aperture size of lens I5 is reduced as the intensity of the beam of projected light increases, thereby permitting the intensity of the beam projected onto screen I8 to be maintained at a predetermined standard during the printing operation.

In order to interrupt the projection beam during those periods of time during which the projection screen I8 is being opened or closed relative to the sensitized paper mounted in gate I1, and in order toprovide means coordinated therewith'for accurately controlling the projection time, a unique shutter element, denoted generally by the numeral 32 may be employed to advantage. In the interests of convenience and brevity of disclosure, it should be observed that the particular shutter means 32 illustrated in Fig. 1, are similar to and are substantial duplicates of the shutter device illustrated in Fig. l2 of the U. S. Patent No. 2,107,861 issued to A. L. Mayer on February 8, 1938.

Shutter means 32 may comprise a pair of individual shutter elements and 5I which are formed on bell crank elements 52 and 53 respectively, and which in turn are pivotally mounted to shaft 54 carried by bracket 55, secured to bed I0. The lower end of bell cranks 52 and 53 are connected by links 55 and 51 to arm 58 fixed to rock shaft 23 which is operatively connected to a foot treadle 59 by means of link 69, as shown. Shutterelements 5l] and 5I are so designed as to normally permit the passage of a projected beam 4from lens I5 toV screen IB during those periods of time when said screen is closed against support I5. As shaft 23 is rotated, links 56 and 51 cause the individual shutter elements to move across'each other thereby obstructing the passage of light from lens I5 by the overlapped portions of the individual shutters. The screen actuating means is preferably so coordinated with rock shaft 23 as'to swing screen I8 away from support I6, to expose the photographic paper mounted in gate I1, during that period of time when the projected beam is thus obstructed.

Further rotation of shaft 23 causes the individual shutter elements to move past each other for providing an opening in front of lens I5 through which light passing through said lens is projected (liuto the exposed printing paper mounted in gate As treadle 59 is released the individual shutter elements move across one another to assume their initial position, it being understood that screen I8 is closed against support I6 while the beam of projected light is interrupted or obstructed by the moving shutters.

From the foregoing it is apparent that the direct intensity of the projected beam may be accurately measured and, if necessary, standardized while the projection screen I8 is closed, and while the negative is being projected thereon for inspection and observation by the operator. After the intensity of the projected beam has been standardized, the light sensitive cell 25 is removed from the projection eld of lens I5 concurrently with the opening of Screen I8 to which it is affixed, and after the sensitized paper has been exposed, cell 25 is returned into the projection field of the lens as screen I8 is closed.

It is to be understood that various modifications and changes in the structural details of the device may be made, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed is:

1. In a photographic device, a film support, a paper support, a projection lens between said film support and said paper support, a projection screen normally disposed between said lens and said paper support in parallel adjacency to the plane of the paper supported thereby, a shutter for said lens, light sensitive means disposed on said projection screen in the field of projection of said lens, means for moving said screen and light sensitive means out of the field of projection of said lens, a meter operatively connected to said light sensitive means for visually indicating variations in the intensity of the projected beam on said screen, means for controlling the intensity of said beam and manually operable means for coordinating said last mentioned means relative to said meter indication for standardizing the intensity of the projected beam regardless of the particular density of the particular film being projected. and means interconnected with said screen moving means for closing said shutter incident to movement of said screen from the field of projection then opening said Vshutter to expose said paper to projection and then closing said shutter incident to movement of said screen back into the field of pro-v jection.

2. In a photographic device, a lm support,- a paper support, a projection lens between said film support and said paper support, a projection screen normally disposed between said lens and said paper support in parallel adjacency to the plane of the paper supported thereby, a shutter for said lens, light sensitive means disposed on said projection screen in the field of projection of said lens, means for moving said screen and light sensitive means out of the field of projec# tion of said lens, an indicating device operatively connected to said light sensitive means for visually indicating by the swing of a pointer over a dial variations in the intensity of the projected beam on said screen, means for controlling the intensity of the projected beam by varying the effective aperture size of said lens, and means for.

correlating the setting of said last mentioned means in accordance with the reading on said indicating device for standardizing the intensity of the projected beam for diierent densities of the lms being projected, said means comprising in combination, a dial, a pointer movable over said dial and means for operatively interconnecting said pointer to said beam-intensity controlling means, the relationship between the reading of said indicating device to said second dial being such that by manually moving the pointer ofthe second dial to correspond with the reading on the indicating device the intensity of the projected beam will equal a predetermined standard.

3. In a device of the class described, a source of illumination, a nlm support, a projection lens, a shutter for said lens, an adjustable diaphragm for controlling the eiective aperture of said lens, a paper support, a pivotally mounted projection screen normally disposed between said lens and said paper support, photoelectric means sensitive to variations in the intensity of the beam projected through said lens said means secured to and carried by said screen, means for moving said screen out of the eld of projection of said lens, an indicating device operatively connected to said photoelectric means for visually indicating variations in the intensity of the projected beam on said screen, said indicating device including a calibrated dial and a pointer the swing of which is proportional to and a function of the intensity of the projected beam, a second indicating device operatively secured to said diaphragm, said device including a calibrated dial and a manually movable pointer the swing of which isa function of the effective aperture of said lens, the calibrations of said last mentioned dial being so related to the calibrations of the dial of said first mentioned indicating device that the intensity of the projected beam will be established at a predetermined standard when the manually movable pointer is set to correspond with the same calibration on its dial as is indicated by the pointer of said first mentioned indicating device, and means interconnected with said screen moving means for closing said shutter incident to movement of said screen from the eld of projection then opening said shutter to expose said paper to projection and then closing said shutter incident to the movement of said screen back into the eld of projection.

ALVIN L. MAYER. HANS R. KOSSMAN.

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