US2699101A - Photocomposing machine - Google Patents

Description

Jan. 11, 1955 "w. F. c. FERGUSON ETAL 2,699,101

PHOTOCOMPOSING MACHINE 2 Sheets-Sheet l Filed Sept.v l, 1950 vinili Jan. 11, 1955 w. c. FERGUSON ET AL 2,699,101

PHOTOCOMPOSING MACHINE 2 Sheets-Sheet 2 Filed Sept. l, 1950 INVENTORS j United States Patent Oce 2,699,101 Patented Jan. 11,I 1955 PHOTOCOMPOSIN G MACHINE Walter F. C. Ferguson, West Orange, N. J., and John H. Greig, New York, N. Y., assignors to Mergenthaler Linotype Company, a corporation of New York Application September 1, 1950, Serial No. 182,854 z claims. (ci. 9s-4.5)

This invention relates to photocomposing machines, that is to say, machines wherein images of selected characters are projected optically onto a photographic mem- In many machines of this type, it has been customary to employ character arrays consisting of either a plurality of opaque characters arranged on a translucent background, or a plurality of translucent characters arranged on an opaque background. In view of the wide range assortment of characters necessarily employed in the composition of type for printing, one of the diiiiculties encountered in the design of such machines is the problem of projecting any desired character of the array'onto the photographic member in focus at the center of the optical axis in order that each character composed will be aligned with respect to all the other characters of the sequence. Generally speaking, only that particular character of the array located along the optical axis will be so properly projected.

Various solutions to this problem have already been proposed. One proposed solution was to arrange the characters around the periphery of a revolving drum and to instantaneously project the selected character onto the photographic member as it passes the axis of the optical system. Another proposal was to arrange the characters in vertical and horizontal rows on a shiftable plate and provide mechanism to move the plate vertically and horizontally in a plane to bring any individual character into the optical axis or, in the alternative, to move the optical system with respect to the character plate to accomplish the same result. Still another proposal was to provide each individual character of the array with a separate optical system. The foregoing proposals, While all mechanically or optically feasible, are entirely unsatisfactory due primarily to the costly, cumbersome and highly complicated apparatus required.

The present invention offers a satisfactory solution to the above problem, comprising in essence a rapid and etiicient system for selectively projecting parious characters of afront plate in any desired sequence onto a photographic member in proper focus at the optical axis with an absence of distortion and color fringe, and without any motion of the font plate or the associated optical system.

In the accompanying drawings, the invention is shown merely in preferred form and by way of example, and obviously many changes and variations may be made within its spirit. It is to be understood, therefore, that the invention is not limited to any particular form or embodiment except inesofar as such limitations are specied in the claims.

Referring to the drawings:

Fig. l is a diagrammatic view invention;

Fig. 2 is a greatly magnified perspective of a proposed crossed diffraction grating to be employed inthe present invention; and

Fig. 3 is a diagrammatic view illustrating the projection of one of the characters of the font through the diffraction grating.

The apparatus illustrated in the drawings is enclosed in a suitable dark chamber (not shown). In order to eliminate the effects of color fringe on the composed characters, a source of monochromatic light is used to supply the illumination for the field. The monochromatic light is produced by passing the light of a standard mercury vapor lamp 1 illustrating the present through a standard lter 2 which will transmit only light in the immediate vicinity of the green line of the mercury spectrum, that is tosay, in the immediate vicinity of the Wave length 5461 Angstrom units. However, any other suitable means for producing monochromatic light of other Wave lengths may be employed in lieu theerof. The eld light is projected by a condenser lens system 3 upon an array of characters on a font plate 4.

The array of characters may comprise, as stated, either a plurality of translucent characters against an opaque background, or a plurality of opaque characters against translucent background. The plate 4 may be made of glass or in the form of a photographic film, or otherwise, with the characters arranged thereon in vertical and horizontal rows. In addition, the plate 4 should be removaile to facilitate the substitution of characters of different onts.

The characters are adapted to be composed individually in line on a photographic film 5 by the operation of a keyboard. To this end, any suitable shutter arrangement may be employed to permit the iield light to pass through the chosen character. One such possible arrangement is shown in the drawings, comprising a plurality of pivoted horizontal bars 6, there being one of such bars for each horizontal row of characters, and a plurality of pivoted vertical bars '7, there being one of such bars of each vertical row of characters. The operation of a particular key will, therefore, pivotally displace one bar of each set to uncover the particular character associated therewith.

The array of characters 4 is located at the focal plane of a collimating lens component 8 which renders the light rays coming from the single exposed character practically parallel. The parallel light rays then pass through a pair of crossed diffraction gratings 9, constituting the most important component of the present invention.

The diffraction grating is well knownvin the field of optics and may be brieiiy described as an optical device having a very large number of parallel and very narrow transmitting or light reecting areas capable of setting up wave interference by diffraction, reflection or refraction. Only the former, that is, the transmitting type grating, is shown and described in the present application. However, it should be borne in mind that reection gratings could also be effectively employed with but a few modiiications of the present apparatus. A parallel beam of monochromatic light incident upon diifraction gratings of the transmitting type, due to the Wave-like nature of the light, sets up secondary wavelets at each of the light transmitting areas, which wavelets produce interference with wavelets set up by other light transmitting areas, giving rise to an interference pattern. When an image of a figure is thus transmitted, by properly focusing the interference pattern, it is possible to form an entire row of two dimensional images of the gure, and when two gratings are crossed at right angles, it is apparent that this Would add another interference pattern at right angles to the one caused by the first grating, thereby making possible the formation of an entire field of images of a given figure in two dimensions.

It is this phenomenon, which incidentally may be studied in greater detail in any elementary textbook on physics or optics, that makes possible the present invention. As shown in Fig. 2 of the drawings, the crossed grating 9 herein employed is composed of two individual gratings 9a made of some translucent substance, such as collodion, having a furrowed or corrugated surface j consisting of a multiplicity of tiny rounded ridges, there being about 600 to the inch. The gratings 9EL are mounted together back to back, preferably on some light transmitting member 9b, such as for example a glass plate, in such a manner that the direction of the ruling of one is at right angles to the direction of the ruling of the other. Due to this peculiar construction of the gratings, the crossed rulings form a system of tiny convex lenses, This lens-like feature of the grating has two advantages over the conventional type grating. For one thing, light ncident upon the system is better concentrated in the desired direction than in an ordinary grating system. Also, all, or nearly all, the light incident on the system is utilized, none being wasted by conventional absorbing sections between transmitting slits.

The field light, therefore, creates an image of the single character selected by the shutter arrangement, and the lightfroml the character so exposed` is divided by the crossed diffraction grating 9 so that a single` principal image, as well as a .multiplicity of higherorder images, is formed on' a masking screen 1.1, the images being focusedthereon by the .lens-10. The spacing between the images projected on the masking screen 11 is a `function of the focal length of the lens 10and the number of lines per inch of the gratings 92, and the lens 10 should be selectedaor corrected so that all the potentially useful images will be projected 4in a flat field. lf the spacing betweenthe characters on the-plate 4 is entirely uniform and equal, the spacing between images of the field will not bei-precisely uniformA and equal, although-it will be very nearly rso .(the spacing between lower order images differing from the spacing ybetweenhigherorder images by affew thousandths of an inch), but by corrective spacing of the characters on the plate 4, it is possible to insure that one image of each `of the different selected characters of the array falls along a path of projection common to all characters. It is `also possible to employ a square symmetrical: array of characters and at the same time insure thatk one of the images falls along the common path of projection by corrective bending of the light rays which form the image to be photographed. In this way, a symmetrical array of several hundred characters can be employed, the central character of the array being located squarely on the optical axis, and a multiplicity of images of any individually selected character can be created, the number offsuch images and the spacing between them being so controlled that one image of the character `will always falll on the optical axis. The masking screen `11Qis provided with an aperture 12 located in irwith the optical axistto transmit the single image so a mg.

Figure 3 will be helpful in understanding the foregoing explanation. In that figure, the principal image A of one of the characters located in the vicinity of the upper left 4hand portion of the plate 4 (the numeral 1 being chosen for purpose of illustration) is shown falling in the vicinity of the lower right hand region of the masking screen 11 after having been projected through the crossed diffraction grating 9. Well over 50() distinguishable images can be formed about the principal image A of which the central 400, more or less, will be of practically equal intensity, at least for purposes of printing.

As already explained, while the principal image A merely falls on the masking screen 11, nevertheless one of the plurality of images formed will always fall on the optical axis and be transmitted through the aperture 12. Thus, a camera focused upon this point can photograph, in turn,each of the characters of the array4 so projected.

The image is thereafter (Fig. 1) projected through a collimating lens 13 and reflected by a prism 14 through the imagelenses 15 and 16 onto the photographic film 5. In the embodiment shown in the drawings, the heavycarriaged photographic film 5 remains stationary while the comparatively light prism 14 and lenses 15 and 16 are mounted on a movable carriage 17, which latter is adapted to scan the said film 5, moving a set distance after the composition of each character. The masking screen 11 should be located at the focal plane of the collimating lens 13, said lens serving to render the rays of light parallel so that neither focus nor magnification is disturbed by the `movement of the carriage 17. it should be noted that the point size of the characters to be composed can be quickly changed by moving the lens 16 and the film 5 in the directions indicated by the arrows in Fig. 1.

What is claimed is:

1. In a typographical photocomposing machine, the combination of a stationary font plate comprising an array of type characters arranged in different positions thereon and in spaced relation to each other, means for illuminating any selected type character in the array, a diffraction grating system for producing, by means of interference of the light waves emanating from each different selected character in the array, a multiplicity of images of the selected character, a lens system for focusing all of said images in a common plane, with one image falling on the optical axis of the system, a mask located in said plane and containing an aperture positioned on the optical axis, said mask permitting transmission of the light Waves forming the image fal'iing on the optical axis while preventing transmission of the light waves forming the other images, and a light sensitive member onto which the projected images of the different selected characters are recorded, one after another, as they `are successively formed at the mask aperture.

2. A combination according to claim 1., including a photographic lens system interposed between `the mask and the light sensitive member forl focusing onto the light sensitive member the images of the different selected characters as they are successively formed at the mask aperture.

References Cited in the file of this patent UNITED STATES PATENTS 1,424,886 Douglass Aug. 8, 1922 1,544,090 Eppenstein June 30, 1925 1,833,634 Brasse Nov. 24, 1931 1,960,011 Ives May 22, 1934 2,021,162 Walton Nov. 19, 1935 2,174,003 Ives Sept. 26, 1939 2,180,417 Huebner Nov. 21, .1939 2,322,602 Terry Iune 22, 1943 FORElGN PATENTS 711,918 France July 8, 1931

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