US2816477A

US2816477A - Light intensity control with variable louvers for mosaic picture projection apparatus

Info

Publication number: US2816477A
Application number: US321430A
Authority: US
Inventors: Waller Fred
Original assignee: VITARAMA CORP
Current assignee: VITARAMA CORP
Priority date: 1952-11-19
Filing date: 1952-11-19
Publication date: 1957-12-17
Anticipated expiration: 1974-12-17

Description

3 5 U z 7 E) ursueo ma'miuii iml 5mm EiUUF?! Dec. 17, 1957 F. WALLER 9 LIGHT INTENSITY CONTROL wrrn VARIABLE LOUVERS FDR MOSAIC PICTURE PROJECTION APPARATUS Filed Nov. 19, 1952 z Sheets-Sheet 1 INVENTOR. I

W km-my AT fox/V575 Dec. 17, 1957 F. WALLER LIGHT INTENSITY CONTROL WITH VARIABLE LOUVERS FOR MOSAIC PICTURE PROJECTION APPARATUS Filed NOV. 19, 1952 2 Sheets-Sheet NEUTRAL INCREASE INVENTORQ United States atent O LIGHT INTENSITY CONTROL WITH VARIABLE LOUVERS FOR MOSAIC PICTURE PROJECTION APPARATUS Fred Waller, Huntington, N. Y., assiguor to The Vitarama Corporation, Huntington, N. Y., a corporation of New York Application November 19, 1952, Serial No. 321,430

12 Claims. (Cl. 88-24) This invention relates to motion picture projection and more especially to the control of the light intensity. The invention is especially useful in the projection of mosaic pictures because any difierence in the light intensity of adjacent sections of the picture is readily apparent and impairs the continuous effect of the picture.

It is an object of this invention to provide an improved light controller which is efiicient, economical, of strong construction and capable of withstanding the high temperatures of a projector without warping or other damage.

One feature of the invention relates to a grid located in or adjacent to the lamp housing of a projector and having strips forming louvers which are variable by moving the strips into difierent angular positions with respect to the light beam to change the amount of light passing to the gate of the projector. The variation in light transmitted through the grid, with the strips, in diiierent positions, being at least as great as the variation in the intensity of the light source with which the grid is intended to be used.

Another object of the invention is to provide an improved method for controlling the intensity of illumination of a projected image on a screen; and for maintaining different sections of a mosaic picture with substantially equal light intensity.

In applying the invention to the projection of mosaic images the control can be effected by either decreasing the light on a section which is of too high intensity or by increasing the light from one or more projectors which are producing images not as bright as the adjacent images.

Another feature of the invention relates to the construction of the grid with louvres under tension so as to maintain them straight and regular in spite of extreme variations in temperature.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views;

Figure l is a top plan diagrammatic view showing the light controller of this invention applied to two projectors which are being used to produce a mosaic image on a screen.

Figure 2 is a side elevation of a portion of a lamp housing, partly broken away, showing the light controller of this invention.

Figures 3 and 4 are greatly enlarged, fragmentary, sectional views of the light controller grid in difierent positions.

Figure 5 is a front view of the construction showing Figure 2 with both a motor and manual control for shifting the position of the light controller grid.

Figure 6 is a greatly enlarged sectional view on the line 6-6 of Figure 5.

Figure 7 is a sectional view on the line 7-7 of Figure 5.

Figure 8 is an enlarged, diagrammatic view showing the way in which the grid is constructed so as to maintain the louvres under constant tension.

Figure 9 is a greatly enlarged fragmentary view, partly broken away, showing the relationship of the vertical and horizontal elements of the grid, and showing the connection of the horizontal elements to the side frames of the grid.

Figure 1 shows diagrammatically the way in which two projectors are used to make a mosaic image on a screen 10. One of the images on the screen extends from the point a to the point b. The other image extends from point r: to point d on the screen. The area of the screen between the points b and c is illuminated by both projectors but these edge zones of the pictures are vignetted so that the light intensity decreases to zero across the zone bc. Since the two images decrease in intensity in opposite directions, the total illumination within the zone [7-0 is equal to that of the other illuminated areas of the screen when the light beams from the different projectors are of equal intensity.

The projector that illuminates the screen between the points a and b is indicated by the reference character 11; and that projector that illuminates the screen between the points 0 and d is indicated by the reference character 12.

Each of the projectors 11 and 12 includes a light source 15, a curved reflector 16, a lamp housing 17 and a lens 18. The construction of the projectors is conventional, and it will be understood that the slides, films or other transparences to be projected are located in front of the lamp housing 17 and behind the lens 18. Within each of the lamp housings 17 there is a grid 20 which is movable to control the intensity of the light beam beyond the grid.

The details of construction of the grids 20 will be described in connection with other figures, but for the present it is sufficient to understand that each of the grids 20 has louvers through which the light beam passes, and that the grid can be rocked into different positions to change the amount of light which passes through the louvers.

In the operation of the invention, the grids 20 of the respective projectors are independently controlled. If the intensity of the light from one projector has increased so that the image on one area of the screen is noticeably brighter than the other, the grids are operated so as either to increase the light of one image area or decrease the light of the other image area, or both.

Whether a decrease in the brighter light beam, or an increase in the less intense beam, is used depends upon the existing positions of the grids in the lamp housings. If one grid is already in position to give maximum illumination, it will be evident that the grid in the other lamp housing must be operated to decrease the light of that projector if the image from it is too bright.

This invention can be used with a single projector for controlling the intensity of the illumination on the screen, but the variation in the light from a projector light source is not usually sufficient to be objectionable when only one projector is used. In the projection of mosaic images, however, otherwise inconsequential variations in light intensity are objectionable because the audience sees areas of different illumination close together on the screen.

The reflector 16, in each projector, concentrates the light to form a tapered beam in which the rays converge as they approach the opening in the front of the lamp housing 17. Figure 2 shows a side elevation of one of the lamp housings 17. The top and bottom walls of the lamp housing converge at an angle substantially,

equal to the angle of convergence of the rays of the light beam. The opening at the front of the lamp housing 17 is indicated by the reference character 22. The cross section of the lamp housing 17 is purposely made somewhat larger than the cross section of the light beam so that the edge portions of the grid 20 are not within the light beam.

The grid 20 has axles 24 at its opposite ends, and these axles extend into bearings 25 carried by a block 26 attached to the side wall of the housing. There are stops 28 attached to the top wall of the lamp housing. These stops extend downwardly far enough to prevent the grid 20 from swinging beyond the angle positions illustrated in Figure 2. The stops 28 are attached to the lamp housing by fastening means, such as bolts 30, and these bolts extend through slots 31 in the stops 28. When the bolts are loosened, the stops 28 can be moved lengthwise of the housing, to the limits permitted by the slots 31, to change the angular range of adjustment of the grid 20.

The grid 20 has side frame members 34 and top and bottom frame members 36, which are of substantial cross section. There are strips 38 (Figure 3) extending between the side frame members 34. These strips 38 have their rearward edges parallel to one another, also their forward edges; but the top and bottom surfaces of the strips 38 are in substantial alignment with the converging rays of the light beam when the grid 20 is rocked into its rearward position, as shown in Figure 3. None of the strips 38, therefore, has its top and bottom surfaces parallel with the corresponding surfaces of any other strip; and when the grid is in the position shown in Figure 3, the strips 38 offer a minimum of interference with the passage of the light beam through the grid.

The strips 38 are preferably made of metal, such as stainless steel or aluminum, and they are treated to provide them with black and non-reflecting surfaces so that they will not set up reflections and hap-hazard light beams within the lamp housing.

Figure 4 shows the way in which the strips 38 change their relations to the light rays when the grid 20 is swung forward into contact with the front stop 28. In this position, each of the strips 38 is at an acute angle to the rays of light in the light beam. The light rays which strike the bottom surfaces of the strips 38 are blocked and the only light which passes through the grid is that which travels between the rearward top edge of one strip and the forward bottom edge of the next adjacent strip above. It will be apparent that if the strips 38 are spaced closely enough, no light would pass through the grid 20 when in the position shown in Figure 4.

Since the intensity of the light sources, with which the grid is used, does not vary more than about 25%, it is sufiicient to construct the grids with the spacing of the strips 38 far enough apart to permit passage of about 75% of the light when the grid is in its maximum-obstruction position, shown in Figure 4.

Figure 5 shows the front of the lamp housing 17 with the opening 22 through which the mid portion of the grid 20 is visible. A portion of the end of the grid is shown through a broken-away part of the front wall of the housing 17. This figure also shows the apparatus for swinging the grid 20 angularly to vary the intensity of the light beam that comes from the lamp housing.

At one side of the lamp housing 17, the axle 24 of the grid extends for a substantial distance beyond the bearing block 26 and into a housing 40. One end of the axle 24 projects beyond the housing 40 and has a knob 42 connected to it. When the grid is to be adjusted manually, the adjustment is effected by turning the knob 42 one way or the other depending upon whether the light is to be increased or decreased.

There is a clutch plate 44 secured to a collar 45 which slides longitudinally on the axle 24. A spring 46 urges the clutch plate 44 toward the left ipFigure 5. A key 47 permits the collar 45 to move longitudinally on the axle 24, but causes the collar and axle to rotate as a unit.

Another collar 50 turns freely on the axle 24 and carries a clutch plate 52 against which the clutch plate 44 is held by the pressure of the spring 46.

The collar 50 is rotated by a worm wheel 54, which is driven by a worm 56, attached to a drive shaft 58. This drive shaft 58 has a large spur gear 60 at one end; and the spur gear 60 meshes with a pinion gear 62 on a shaft below the spur gear 60. The pinion gear 62 is attached to the armature shaft of an electric motor 64, secured to one side of the housing 40. The pinion gear 62, spur gear 60, worm 56 and worm wheel 54, constitute reduction gearing through which the grid axle 24 is moved by the motor 64.

The motor 64 is reversible so that it can shift the grid 20 in either direction, and it is used when the grid is to be operated by remote control. This is desirable when the projectors are used for projecting mosaic images because it enables the light intensity from the plural projectors to be controlled by one attendant. Remote control means, for the motor 64, are shown in Figure 5. Power for the motor is supplied by a manually-operated reversing switch 66, movable to one side from a neutral position to supply power to operate the motor 64 in one direction, and movable to the other side of the neutral position to supply power to operate the motor 64 in a reverse direction. Of the two different positions, on either side of the neutral positions, one corresponds to an increase in light intensity and the other to a decrease in light intensity.

The illumination of a screen is ordinarily more intense in the center of a projected image because the optical systems of the projectors tend to concentrate light at the center of the projected beam. This excess illumination at the center of the image can be counteracted with this invention by making some of the strips 38 so that they have up-turned lips 70 along their forward edges. The strip 38 at the center of the grid has the highest lip 70 and the height of this lip decreases progressively on both sides of the center of the strip.

Figure 6 shows a sectional view through the midportion of the strip 38. The adjacent strips 38 have lips 70 which are somewhat lower; and other strips 38, further from the center, have successively lower lips. Beyond the center region of the grid, the strips 38 are made without any lip 70.

The grid is provided with vertical strips 74 for maintaining the horizontal strips 38 with the forward and rearward edges of each strip parallel to those of the other strips, and for preventing warping of the strips 38 under the influence of the extreme temperature variations to which they are subjected in use. These vertical strips 74 are in alignment with the light rays when the grid is in position to transmit a maximum of light and they have their forward and rearward edges parallel to the corresponding forward and rearward edges of the other vertical strips. The vertical strips have little or no influence upon the variation in light since the rocking movement of the grid is in a direction almost parallel to the faces of the vertical strips.

The grid is constructed by having about one half of the width of each of the strips 38 pass through slots 76 in the side frame members 34; and the vertical strips 74 are held in slots 78 in the top and bottom frame members 36.

Figure 8 shows the construction of the grid frame before the strips are connected with the frame. The side frame members 34 are preferably bowed outwardly away from one another, as indicated in full lines, the extent of the bow being somewhat exaggerated for clearer illustration. These side frame members 34 are forced into the parallel relation, indicated in dot-and-dash lines in Figure 8, before the strips 38 are attached to the frame members. The strips-38 are then placed between the side frame members 34 with the ends of the strips 38 projecting through and beyond the slots 76, as shown in Figure 9. The extending ends of the strips 38 are bent upwardly or downwardly along the outside face of the side frame member 34 and welded, or otherwise secured, to the face of the frame member.

When the force holding the side frame members 34 parallel with one another is released, the strips 38 are placed under tension because they are then the only means maintaining the side frame members 34 parallel with one another.

The vertical strips 74 extend through and beyond the slots 78, in the top and bottom frame members 36, and are attached to these frame members 36 in a manner similar to that used to attach the horizontal strips 38 to the side frame members 34.

There are slots 81 extending inwardly from the rearward edges of the horizontal strips 38 for substantially one half of the width of these strips. There are complementary slots 82 extending inwardly from the forward edges of the vertical strips 74. The slots 81, in successive strips 38, are in substantially vertical alignment with one another. The slots 82 are spaced from one another by the intended spacing of the strips 38, and these slots 82 extend in the direction of the rays of light so as to hold intermediate portions of the horizontal strips at the intended angle to the axis of the light beam, if the tension of the strip 38 is not sufficient.

When each vertical strip 74 is inserted .into the slots 81 of the horizontal strips 38, with the slot 82 of the vertical strip engaging the horizontal strip 38 in front of the slot 81, the strips engage with one another, as shown in Figure 9, and in a manner similar to that of the separators commonly used in conventional egg boxes.

The preferred embodiment of the invention has been illustrated and described. Terms of orientation are, of course, relative. Changes and modifications can be made and some features of the invention can be used in different combinations without departing from the invention as defined in the claims.

I claim as my invention:

1. Mosaic picture projection apparatus comprising two projectors in position to project adjacent sections of a mosaic picture on a screen, light intensity control apparatus for maintaining uniformity of illumination of the adjacent edge portion of the different sections of the mosaic image including a separate grid located in the ligth beam of each projector and between the light source and the projection gate of the projector, each grid having a plurality of slots with substantially parallel entrances, supports on which the respective grids rock to move the top and bottom walls of the slots into various angular positions with respect to the direction of the rays of the light beams to change the amount of light passing through the grid, independent actuators for the respective grids and remote control means for each actuator, the remote control means including manually-actuated controllers at a single control station and at a location within sight of the screen for selective operation by an attendant watching the screen.

2. The light-intensity control apparatus described in claim 1, characterized by light housing shields that extend toward the focal planes of the projectors, and grids located in the shields and supported by the shields at substantial distances from the focal planes of the projectors to avoid grid shadow in the projected images.

3. Mosaic picture projection apparatus comprising two projectors in position to project adjacent sections of a mosaic picture on a screen, control apparatus for obtaining substantially equal light intensity of the adjacent edge portions of different sections of the mosaic image produced by the projectors on a screen, said control apparatus including a separate grid in the light beam of each projector and between the light source and the projection gate of the projector at a region where the light beam tapers to reduced cross section, each grid having a plurality of slots with substantially parallel edges and with the top and bottom walls of the different slots converging in accordance with the rays of the light beam in which the grid is located, a support for each grid, including bearings on which the grid rocks to move the top and bottom walls of the slots into different angular positions with respect to the direction of the rays of the light beam to change the amount of light passing through the grid, a separate reversable motor operably connected to each grid, and a remote control means for each motor, each of the remote-control means including a switch actuator movable into one position to shut off the power to the motor and in opposite directions to other positions that supply power to drive the motor in a forward and reverse direction, the switch actuators being located at. a common control station at a location within sight of the screen and from which an attendant can watch the screen.

4. Light-intensity control apparatus for a mosaic projector and to be located in the light beam from the light source and between the light source and the projection gate and including a frame and strips supported by the frame with their forward edges substantially parallel to one another and spaced from one another in the directions of the minimum dimensions of the strip so that they form slots in the grid with the wide faces of the strips forming the tops and bottoms of the slots, and with adjacent strips converging in accordance with the convergence of the light beam with which the grid is intended to be used, supporting means for the frame including a bearing-having a pivot axis with at least a substantial component of its direction of extent parallel to the forward edges of the strips, a reversible electric motor, motion-transmitting connections, including an irreversible speed reducer through which the motor operates the grid, and remote-control means that are movable into different positions to stop and start the motor and to reverse its direction of movement.

5. A light-intensity controller for location adjacent the lamp housing and between the light source and the projection gate in the converging light beam of a mosaic projector, said controller comprising a frame with opposite side members of generally arc-shaped contour in planes parallel to one another, and with the axis of curvature of each side member on the side of the frame from which the light beam converges thin flexible strips connected at their opposite ends to the respective side members of the frame and forming louvers through which the light beam passes, the surfaces of the louvers converging in accordance with convergence of the light beam with which the controller is intended to be used and a frame-supporting bearing having a pivot axis which is generally parallel to the axis of curvature of the arcshaped side members.

6. A light-intensity controller, as described in claim 5, characterized by slots in the side frame members extending in directions that converge similarly to the convergence of the rays of the light beam and for receiving the ends of the strips.

7. A light-intensity controller, as described in claim 5, characterized by strips that extend through and beyond the side frame members and that have their extending ends bent over into contact with the outer faces of the side frame members, and means securing the bent-over strip ends to the side frame members.

8. A light-intensity controller to be located adjacent 4 to the lamp house of a projector and in the light beam between the light source and the projection gate and including a grid comprising a frame, strips supported by the frame, with the forward and rearward edges of the strips substantially parallel to one another and the wide surfaces of the respective strips converging in accordance with the convergence of the rays of the light beam with which the grid is intended to be used, and a pivotal support for the grid with an axis of rotation substantially parallel to the forward and rearward edges of the strips, the middle portions of the strips that cross the center region of the light beam having lips along their edges for obstructing a portion of the light, each of the lips having its maximum height at the center of the grid and decreasing progressively in height toward each side of the center, and strips both above and below the center of the grid having lips with maximum heights that are progressively less as the strip is located progressively further from the center of the grid.

9. A light-intensity controller to be located adjacent to the lamp house of a projector and in the light beam between the light source and the projection gate and including a grid comprising a frame, strips supported by the frame, with the forward and rearward edges of the strips substantially parallel to one another and the wide surfaces of the respective strips converging in accordance with the convergence of the rays of the light beam with which the grid is intended to be used, the frame having slots therein which extend in directions that are in substantial alignment with the light rays at each region of the frame when the grid is located in position to transmit maximum light of the light beam with which it is intended to be used, the strips of the grid having their end portions extending into said slots for holding the strips with their wide surfaces substantially parallel to the rays of the light beam.

10. The light-intensity controller described in claim 9, with the ends of the strips projecting beyond the frame and bent over into contact with the frame and bonded to said frame.

11. A light-intensity controller to be located adjacent to the lamp house of a projector and in the light beam between the light source and the projection gate and comprising a grid having a frame with side frame members that have a bias to oppositely bowed positions in which the middle portions of the side frames are spaced from one another by greater distances than the tops and bottoms of the side frame members, strips supported by the frame and extending between the side frame members and holding the side frame members in substantial alignment with one another so that the bias of said side frame members imparts a tension to the strips, the forward and rearward edges of the strips being substantially parallel to one another while the wide faces of the strips converge toward a center which corresponds to a center of convergence of the light rays of the beam with which the light-intensity controller is intended to be used, and a pivotal support on which the grid is movable into different angular positions with respect to the axis of the light beam.

12. A light-intensity controller to be located adjacent to the lamp house of a projector and in the light beam between the light source and the projection gate and comprising a grid including a frame with top, bottom, and side frame members, strips extending between the side frame members, the opposite ends of said strips being attached to the side frame members and the forward edges of the respective strips being substantially parallel to one another, other strips extending between the top and bottom frame members, said other strips having slots extending inwardly from their forward edges for a distance approximately half-way to the rearward edge of the strip and at spacings corresponding to the desired spacings of the strips that extend between the side frame members, there being complementary slots in the strips that extend between the side frame members, the complementary slots extending inwardly from the rearward edges of the strips and being spaced along the length of each strip at distances corresponding to the spacing of the strips that extend between the top and bottom frame members, and a pivotal support on which the grid is movable into different angular positions with respect to the light beam in which it is intended to be used.

References Cited in the file of this patent UNITED STATES PATENTS 947,490 Gwodz Ian. 25, 1910 1,333,482 Goldie Mar. 9, 1920 1,335,889 Fulton Apr. 6, 1920 1,467,194 Peterson Sept. 4, 1923 1,520,869 Killian Dec. 30, 1924 1,627,396 Lehmann May 3, 1927 1,806,452 Fulgora May 19, 1931 1,808,352 Hollen June 2, 1931 2,186,203 Centano Jan. 9, 1940 2,278,142 Mack et al Mar. 31, 1942 2,610,544 Waller et al Sept. 16, 1952