US2275905A - Image reverser for cameras - Google Patents

Description

March 10, 19% w. c. HUEBNER IMAGE REVERSER FOR CAMERAS Filed Feb. 27, 1940 4 Sheets-Sheet l INVENTURI W/u/AM C flan/v52,

ATTORNEY.

' March 10; 1942. w. c. HUEBNER v v IMAGE REVERSER FOR CAMERAS Filed Feb. 27, 1940 4 Sheets-Sheet 2 INVENTEIR WILL/AM C. Hum/me,

EWM

ATTURNEY.

March 1942- w. c. HUEBNER IMAGE REVERSER FOR CAMERAS Filed Feb. 27, 1940 4 Sheets-Sheet 3 FILLIEL v EWM ATTUHNEY.

Patented Mar. 10, 1942 UNITED STATES PATENT OFFICE IMAGE REVERSER FOB. CAMERAS William 0. Huebner, New York, N. Y.

Application February 27, 1940, Serial No. 321,014

3 Claims.

This invention relates to improvements in image reverser for cameras.

In certain arts utilizing photography, and more especially the art of photomechanical printing, it is necessary to turn or reverse the image ultimately incorporated on the press plate, dependent upon the method of printing used, in order that the impressions taken from the press plate will be read correctly. For instance, inletter press or direct printing, employing the English language, the lines of lettering or readable characters must read from right to left and be head up on the printing plate so that, when the ink impressions are obtained on the paper from the printing plate by direct contact with the printing plate, the impressions will read correctly from left to right and be head up.

The same situation also is true in the case of direct gravure printing where the lettering on the gravure cylinder or plate must read from right to left and be head up so that, when impressions are taken by direct contact, the impressions will read normally, that is, from left to right and be head up.

' In the case of offset printing, the lettering or readable characters in the English language must be incorporated on the press plate so as to read and be arranged exactly as they are to appear on the final printed sheet, that is, from left to right and head up. This is due to the fact, as well known to those skilled in the art, that the offset blanket on the blanket cylinder of the usual offset press, first lifts the ink image head up but with the lettering in reverse, considred lineally of the lines of lettering, and then the ink images of the lettering are transferred from the offset blanket to the paper with the lettering head up and reading from left to right exactly as on the press plate.

When preparing press plates for offset presses, particularly deep etch press plates, the usual method is to employ positives of the lettering and other matter to be reproduced and, by contact exposure from such positives to the sensitized press plates, obtain on the latter what may be termed photographic stencils which, after proper development, produce on the press plates, positive images of the lettering or other matter, reading from left to right and positioned head up. Obviously, to accomplish this result, the letters or other characters on the positive plate or film which is used for contact exposure on the press plate, must read from right to left and be head up. I

To obtain the proper negatives with the lettering in reverse, for photoengraving processes, it has been the general practice to employ a triangular section of glass or prism with a reflecting mirror on the long side thereof which prism is mounted in front of the camera lens. The copy (containing the letters or other readable characters), is then placed on a copyboard,

which latter is in a plane parallel to the axis of the lens but located either below or to one side of the lens axis. The image of the copy is thus reflected by the prism mirror surface to and through the lens to the negative and the letters or other readable characters will, when viewed from the emulsion side of the negative read from left to right, head up as on the printed sheet. With negatives thus produced, the same may be laid with the emulsion sides in contact with the sensitized metal plates, the exposures made and the plates then developed and etched for printing. The images thereby made on the press plates, will read from right to left, head up as required for direct relief and gravure printing.

With the prism method of reversing images, however, there are several serious disadvantages. In the first place, this method requires a so called right angle camera which is more or less cumbersome and troublesome. Furthermore, the prism method does not permit of the necessary degrees of enlargement or reduction often required in commercial practice.

In preparing the positives necessary for deep etch offset printing, hereinbefore referred to, the method heretofore employed and the one which is necessary in that type of cameras known as a straight lin camera, that is, a camera wherein the copy, lens, and negative are all arranged in the line of the lens axis with the planes of the copy and negative parallel to each other and perpendicular to the lens axis, the following method has heretofore been employed. The copy (containing the letters or other readable characters) is placed on the usual copyboard located in front of and facing the lens and the negative then exposed in the usual manner. After development of the negative, the latter is then placed on the copyboard in front of and facing the lens and exposed through the lens onto av second sensitized plate or film which latter obviously then becomes a positive. While this method permits of the necessary enlargements or reductions required in commercial work, it is subject to a serious disadvantage, particularly in deep etch offset work, in that the positives so made from the negatives by ness that are obtainable from direct contact exposure from-a negative to a positive.

obtaining a reversed negative; the usual or ortho- One object of this invention, therefore, is

provide a simple and efficient attachment for a lens of a straight line camera such that the image of the copy to be reproduced, is so turned on the negative that a contact positive can Be made from such negative and the latter in turn used for contact with the sensitized surface of a press platein preparing the press plate for offset printing.

Another object of the invention is to provide a photographic image reversing device such that, when the device is applied to'or associated with a lens of a camera and th copy to be photographed, with the matter thereon readable from left to right head up, is placed in front of and facing the lens, the image of the copy may be focused on a sensitized element in such manner that the resultant image produced on the sensitized element, when viewed from the emulsion side of the negative, will read from left to right and head up.

A further object of the invention is to provide an image reversing attachment for a camera lens which comprises a series of image reflectors so arranged that the image of a copy located in front of and facing the lens first impinges upon or is picked up by the incident reflector of the series and is then reflected successively to the others of the series and from the last of the series directly to and through the lens.

A difliculty commonly experienced in camera work, particularly where images must be reflected from one surface to another is the formation of so called ghost images due to side leakage of light which give faint reflections outside the work area, thus bringing in unnecessary light and graying the images produced on the negative so that proper contrast of the image is not projected on the ground glass and thus necessitating more time exposure around the outer edges than at the center.

To eliminate such ghost images, and particularly where very fine work is required, another object of the present invention is to provide simple means for trapping such ghost images or intercepting stray light rays around the work area, which means are readily removable and interchangeable for others of different characteristics best suited for each particular job.

Other objects of the invention will more clearly appear from the description and claims hereinafter following.

In the drawings forming a part of this specification, Figure 1 is a front elevational view Showing one embodiment of the invention as mounted on the lens of a straight line camera. Figure 2 is a side elevation of the image reverser shown in Figure 1. Figur 3 is an elevational view of the image reverser shown in Figure 1, but taken from the rear side thereof, the image reverser being removed from the lens barrel. Figure 4 is a vertical sectional view corresponding substantially to the line 44 of Figure 1. Figure 5 is a view similar to Figure 1, but with a front plate removed and with the light'interceptor or ghost trap plat shown in section. Figure 6 is a horizontal sectional view corresponding to the section line 6-6 of Figure 5. Figure 7 is an enlarged detail sectional view, illustrating one of the means for holding a mirror in place. Figures 8, 9 and 10 are schematic views illustrating, respectively, the prism method heretofore referred to of dox method of obtaining a negative in a straight line camera; and the method of obtaining a re versednegative in accordance with the present invention in a straight line camera, the negatives in the several views indicating the emulsion sides thereof. Figures 11, 12, 13, 14 and 15 are elevational views of different designs of ghost image trap plates or light interceptors. Figure 16 is an edge elevational view of one of the light interceptors shown in Figures 11 to 15. Figure 17 is an elevational view of a light interceptor or ghost image trap plate showing a light diffuser mounted thereon and Figure 18 is a side elevational view of the structure shown in Figure 17.

Referring first to the construction illustrated in Figures 1 to 7, I0 indicates, conventionally, the barrel of a lens of a straight line camera and to which, in the form of the invention chosen for illustration, the improved image reverser is adapted to be attached.

The improved image reversing device, as shown, preferably consists of a main metal frame, housing or supporting member A, having a vertical back wall I2 with a suitable opening I3 therein adapting the supporting member to be slipped over the lens barrel, as best shown in Figures 4 and 6, and ,detach'ably secured thereto by thumb nuts I4-I4. Rigid with the back wall I2 is a plurality of spaced posts I2 adapted to bear against the lens barrel base IIl to both steady the attachment and assure its correct position relative to the camera lens.

The supporting member or housing A is formed with a depending chamber defined by vertical side walls I5-I5 extending parallel to the lens axis and a back wall I6 extending at an angle of 45 to the vertical, as best shown in Figures 1, 2 and 5. Said chamber has a front rectangular opening I! which faces the usual copyboard of a straight line camera which, as hereinbefore explained, has the copyboard in line with the axis of the lens and facing the latter. As will be seen from Figure 1, said chamber defined by the walls I5I6 is ofiset slightly downwardly and to one side of the lens axis. Disposed within said chamber and positioned on the inclined back wall I6, is the incident or first reflecting mirror I3 of the series of mirrors of the image reverser. Said mirror is preferably held in place by a pair of bush pins I9-I9 disposed at the side edges of the mirror I8, each of said bush pins, as best shown in Figure 7, having a stem 20 which extends loosely through a corresponding opening ZI in the wall.- Each bush pin, when brought down into contact With the mirror, is then adapted to be securely held by tightening up the thumb nut 22, as shown. To facilitate insertion and removal of the mirror I8, the wall I6 is provided with a detachable flange It at the lower edge, said flange being held in place by thumb screws I6.

Above the incident chamber defined by the walls I5 and IS, the housing or supporting member A is provided with a wall 23 which is in a. plane parallel to the axis of the lens and is inclined at an angle of 45 to the vertical and from the outer side of the supporting member toward the top thereof, as best shown in Figures 1 and 3. Said inclined wall 23 in conjunction with the back wall I2 and vertical front wall 24 defines what may be termed the second or intermediate chamber of the housing or supporting member and is in open communication with the incident or first described chamber, as indicated by the opening 25, best shown in Figures 5 and 6. Mounted on the inner side of the inclined wall 23 (see Figures and 6) is a second or intermediate reflecting mirror 26, the same being secured in position by bush pins l9-22 in the same manner as previously described in connection with the mirror II. The front wall 24 is made detachable from the main member A, as by the thumb screws 24, to allow of access to the interior of the member A, as clear from Figures 5 and 6. The detachable wall or plate 24 is preferably provided with a handle 34.

The housing or supporting member A is formed with a third chamber which is disposed directly in front of the lens, said chamber being defined in part by the rear vertical wall I2, bottom and top horizontal walls 21 and 26 (see Figure 4) and a front wall 29. The latter is preferably made detachable as by screws 29 and extends in a vertical plane intersecting the axis of the lens at an angle of 45, as shown. Secured to the inner face of said wall 29 is the third or emitting reflecting mirror 39 of the series, the same being secured in the same manner by bush pins as heretofore described in connection with the mirror l8. The third chamber defined by the walls 12, 21, 26 and 29 is obviously normally in unrestricted communication with the second chamber, as will appear from Figure 6.

With the image reversing device attached to the camera lens, as shown, and assuming the copy to be on a copyboard in front of and facing the lens, it is evident that an image of the copy will first strike or impinge upon the mirror 18, as indicated by the dot dash line :c. From the mirror 18, the image will be reflected vertically to the second or intermediate mirror 26, as indicated by the dot dash line 1 From the mirror 26, the image is reflected a second time horizontally to the mirror 30 as indicated by the dot dash line 2 in Figures 1 and 5, and from the mirror 30, the image is finally reflected and emitted horizontally directly into the lens as indicated by the dot dash lines and arrow m, in Figures 2, 4 and 6, and thence, obviously, through the lens to the sensitized element behind the lens where the exposure is made.

In carrying out the invention, while it is obvious that the shapes and sizes of the mirrors may be varied, nevertheless in the preferred form of the invention, the first 'or incident mirror 18 is made the largest, the second mirror 26 somewhat smaller, and the third or emitting mirror 36 the smallest, so that the maximum amount of image will be picked up by the incident or first mirror i6 and the image gradually reduced and rendered sharper as it is finally emitted from the last mirror 30 directly into the lens, and which mirror 30 should be placed as close to the lens as possible. For lenses of different focus, proportional changes of reflecting surfaces may be made so as to utilize the focal length of any lens of given capacity.

To trap or intercept ghost images or stray light rays around the work areas of the reflected images, a trap plate 3| is employed as best shown in Figures 1, 5 and 6. Said plate, which preferably consists of a fiat piece of sheet metal of generally rectangular outline having a flange 32 at one edge thereof for ease of manipulation, is insertable horizontally within guide slots 33 provided therefor in the member A. As will be apparent from Figures 5 and 6, the trap plate 31 is located intermediate -the second and third ghost images or stray light beams prior to the reflection of the image onto the last of the refleeting mirrors 3|.

In utilizing the trap plates '31, the same are centrally apertured as indicated at 36, by dotted lines in Figure 2 and full lines in Figures land 15. In the trap plate 3|, said central aperture is of generally star shape and its over-all area will be adapted to the particular size and capacity of the lens with which the image reverser is being employed. In actual practice, it has been found that different styles of apertures produce better results on different classes of work and in Figures 12, 13 and 14, are illustrated three different styles of trap plates 3|, 31 and 31 having respectively square, diamond and circular apertures 35*, 35 and 35. The sizes and contours of the openings 35, 35, 35 and 35 will be varied in in accordance with the requirements in reductions in the image size to be produced on the negative compared to the size of the image on the copy'; the size of the reproduced image where the same is employed under the rated focal length of the lens; and where the ratio is maintained at 1 to 1 but where the size'of the image is up to or slightly beyond the focal length of the lens.

In Figure 11 is shown a special form of trap plate 31 wherein the central aperture 35 has left within it a central section supported by connector arms 31 which square central section is provided with a plurality of apertures 38. The holes 38 let through a certain portion of the light and even out the light field as it strikes the sensitized surface of the negative and actual practice mirrors 26 and 30 so as to thus intercept all up when viewed from the emulsion side.

has demonstrated that the reflected images pass through the apertures of the trap plate without aberrations of the image beyond the power of the lens and is particularly effective in fine type of work where there is a tendency of the light to spread over thin areas and produce only partial light action and soft edges.

In certain other instances, it has been found desirable to effect a wider diffusion of light, in which case a trap plate such as shown in Figures 17 and 18 at 3| is employed. In this trap plate, the central aperture 35 is preferably similar to that shown in Figure 15 but with cross bars to support the diffuser 39. The latter preferably comprises a central post-like structure detachably mounted on the cross bars of the plate 31, the post having radiating therefrom a series of sharply tapered or cone-like opaque arms 4|, as shown. With this combination of ghost image trap and light diffuser, the stray light rays around the work area are not only intercepted, but the light is so diffused as to produce a uniform exposure on the sensitized surface over the entire work area of the image.

Referring to Figure 9, there is there illustrated schematically, the usual complete reversing process which takes place in the orthodox or ordinary exposure of a copy to a negative. In said Figure 9, 40 indicates conventionally the copy to be reproduced and having thereon a line of lettering or numerals (1940) extending horizontally and reading from left to right, as shown. When the image of said copy s transmitted through the lens 4|, the image is completely reversed as shown on the negative 42, that is, the lettering or numerals read from right to left and are head Heretofore, in the making of positives for deep etch offset, it has been customary to take such negative 42, place it on the camera copyboard (corresponding to the copy 40) and project an image of said negative 42 to make a positive.

In Figure 8 is indicated schematically the prism method of obtaining a reversed negative. heretofore practiced, the original copy as indicated at I40 is disposed in a plane parallel to the axis of the lens Ill butoffset to one side thereof, generally horizontally below the lens v axis. The image of the copy I40 is reflected by the prism 50 through the lens, 'thus producing a negative I42 which, when viewed from the emulsion side, 'has thelettering or numerals reversed from the orthodox negative, that is, reads from left to right but is head up as in the origon the negative reversed from the orthodox neg-.

ative, is obtained with the present invention. In said figure, 240 indicates the copy in which the lettering or numerals read from left to right, head up in the usual manner and, after the image thereof has been reflected by the three mirrors of the reversing device A and through the lens 2, a reversed from the orthodox image is obtained on the negative 242, that is, viewed from the emulsion side, the lettering .o r numerals read from left to right and head up. While in Figure 10, the line of the lettering or numerals in the copy is shown as extending vertically, whereas it appears horizontally in the negative, this is due to the fact of the use of the three mirrors and involves merely a matter of routine on the part of the operator as to whether the lines of the copy are arranged vertically and those of the negative horizontally or those of the copy horizontally and those of the negative vertically in the camera.

- With the improved image reverser,it is evident that the same can be used in a straight line .camera and any degree of enlargement or reduction obtained that may be required by commercial considerations, simply by adjusting the copy toward or from the lens as permitted by the usual straight line camera copyboard construction. In

duced as indicated in Figure 10 by the image reverser, it is evident that a contact positive may be made directly therefrom for deep etch ofiset, thus assuring a positive which is sharp and clear.

While in the preceding description, reference has been made to letters, numerals or readable characters .to be reproduced, nevertheless it will be evident that the invention applies equally to the reversal of illustrations or other matter which require correct positioning as to right and left when incorporated on the press plates and whether the printing is to be done in single color or multiple color. It will also be evident that the mirrors are all detachable, and readily accessible for cleaning or interchange for others,

and the plates for intercepting the stray light rays or ghost images, as previously indicated, are

readily interchangeable. The reverser, as will be apparent from the preceding description, is compact, light in weight and relatively inexpensive.

Although there has herein been shown and described what is now considered the preferred manner of carrying out the invention, the same is merely illustrative and all changes and modifications are contemplated that come within the scope of the claims appended hereto.

What is claimed is:

1. An image reverser for straight line cameras comprising, in combination: housing means; an optical system consisting of a series of three refiecting mirrors of progressively increasing area disposed in said housing means, said housing means being apertured to engage a camera lens. barrel; means for mounting the smallest mirror closely facing the lens and intersecting the lens axis at about forty-five degrees when the lens axis is horizontal; means for mounting the intermediate size mirror in a position displaced laterally from but facing the smallest mirror and parallel to the lens axis; and means for mounting the largest mirror facing the intermediate mirror at an angle of about forty-five degrees to the lens axis, said several mounting means for said mirrors being also such that, when the smallest mirror intersects the horizontal lens axis at about forty-five degrees and is positioned in a vertical plane, said intermediate mirror is positioned at an angle of about forty-five degrees to the vertical and the largest mirror at an angle of about forty-five degrees to the vertical.

2. An image reverser in accordance with claim 1 having ghost image trap means carried by and disposed within the housing means and located between two of said mirrors, said ghost image trap means being apertured for the passage of a true image of the copy but with the aperture of such restricted area as to prevent.

passage of ghost images between said two mirrors while the true image is traveling and being transmitted within said housing means.

3. An image reverser in accordance with claim 1 having apertured light-diffusing means carried by and disposed within the housing between two of said mirrors.

WILLIAM C. HUEBNER.

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