Title:
Light control mechanism
United States Patent 2318616


Abstract:
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...



Inventors:
Mayer, Alvin L.
Kossman, Hans R.
Application Number:
US36567740A
Publication Date:
05/11/1943
Filing Date:
11/14/1940
Assignee:
Mayer
Primary Class:
Other Classes:
355/68
International Classes:
G03B27/72
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Description:

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 provide 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 present invention, with parts thereof being cut away for clarity of detail.

Fig. 2 is a sectional view on line 2-2 of Fig. 1.

Pig. 3 is a sectional view on line 3-3 of Fig. 1.

As disclosed in Fig. 1 the numeral 10 indicates the bcd or frame of the printing and enlarging device, which may be supported upon leg standards I!. A prcjector 12 including a constant source of illumination, such as electric lamp 13, is mounted upon the left end of the bed for 4 projecting the images of photographic negatives, placed laterally in film gate 14, through projection lens 15 Means are disposed at the right end of the bed onto which the image of a negative is projected from projector 12. Such means 4 in its simplest form, may comprise, for the purrose of the present invention, a sensitized photographic raper support 16 including a paper gate I. or the like. into which a sheet of sensitized paper may be laterally disposed while a print is 5( being made.

A so-called projection screen or preview door I$ may be pivotaly mounted relative to the paper support 16 by means of hinges 19, or the like.

Screen 18 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 17.

Suitable means are provided for swinging screen 18 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 18 as at the lower hinge 19. The free end of lever 20 may be connected by means of a cable 21, 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 10. As clearly disclosed in Pig. 2, screen 18 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 18 are merely exemplary in nature, and, if desired, any other screen actuating mechanism may be used, such as, by way of example, the mechanism dis15 closed 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.

SIt will be observed that with screen 18 normally closed the projected image bearing beam is adapted to first fall upon the outer surface of screen 18 for enabling an operator to observe the outline of the projected image before exposSing the sensitized paper to the projected image bearing beam.

In order to ascertain the intensity of the projected image bearing beam at the approximate location of the sensitized paper, light sensitive Smeans such as, by way of example, a photo electric cell 25, or the like, may be mounted centrally of screen 18. The light sensitive cell may be wired to a suitable current measuring instrument, or meter 26, by means of conductors S27 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 18 and the light 0 sensitive cell 25 are disposed directly in the projection field of lens 15.

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 print the densest printable negative disposed in gate 14 of projector 12, a diaphragm 29 may be provided for selectively controlling the effective aperture size of projection lens 15. 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 31, see Fig. 3, to progressively reduce the effective aperture size of lens 15 as said plate is moved in a clockwise direction about the axis of shaft 30. As disclosed in Fig. 1 diaphragm 29 is preferably disposed between lens and the shutter mechanism, denoted generally 1, by the numeral 32.

In order to coordinate the effective aperture size of projection lens 15 with the actual intensity of the projected image-bearing-beam, as recorded on meter 26, means are provided for 2( 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 30 may be operatively connected to 2, a diaphragm pointer 35 which is adapted to sweep diaphragm dial 33 as diaphragm 29 is moved relative to projection lens 15.

The calibration of the diaphragm dial 33 are established relative to, and are a function of, 3 the calibrations of the light meter dial 34, whereby the effective aperture size of lens 15 is reduced as the intensity of the beam of projected light increases, thereby ermitting the intensity of the beam projected onto screen 18 to be main- 3 tained 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 18 is being opened or closed rela- , tive to the sensitized paper mounted in gate 17, and in order to provide 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. 12 of the U. S.

Patent No. 2,107,867 issued to A. L. Mayer on February 8, 1938.

Shutter means 32 may comprise a pair of individual shutter elements 50 and 51 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 10. The lower end of bell cranks 52 and 53 are connected by links 56 and 57 to arm 58 fixed to rock shaft 23 which is operatively connected to a foot treadle 59 by means of link 60, as shown.

Shutter elements 50 and 51 are so designed as to normally permit the passage of a projected beam from lens 15 to screen 18 during those periods of time when said screen is closed against support 16. 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 15 by the overlapped portions of the individual shutters. The screen actuating means is preferably so coordinated with rock shaft 23 as to swing screen 18 away from support 16, to expose the photographic paper mounted in gate 17, 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 15 through which light passing through said lens is projected onto the exposed printing paper mounted in gate 17.

As treadle 59 is released the individual shutter elements move across one another to assume their initial position, it being understood that screen 18 is closed against support 16 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 18 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 field of lens 15 concurrently with the opening of screen 18 to which it is affixed, and after the sensitized paper has been exposed, cell 25 is returned into the proI jection field of the lens as screen 18 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 0 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 5 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 0 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 45 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 re50 gardless 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 55 said shutter to expose said paper to projection and then closing said shutter incident to movement of said screen back into the field of projection.

2. In a photographic device, a film support, a 60 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 65 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, an indicating device operatively 70 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 75 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 different densities of the films 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 1( such that by manually moving the pointer of the 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 film support, a projection lens, a shutter for said lens, an adjustable diaphragm for controlling the effective 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 field 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 is a 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 field 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 field of projection.

ALVIN L. MAYER.

HANS R. KOSSMAN.