US3668984A - Optical character spacing system for phototypesetting - Google Patents

Abstract

A character image projection system successively projects image bearing light beams along a common optical axis toward a photosensitive surface. The images of the individual characters are spaced on the photosensitive surface to form lines of composition. The spacing is accomplished by collimating the image bearing light beams, then diverting the collimated beam by means of a movable reflecting surface into a refocusing and scan lens assembly from which the light beams emit onto the photosensitive surface. The position of the reflector may be controlled by a servo mechanism which responds to character image space information from a computer. The refocusing and scan lens assembly incorporates compensation for the angular position of the reflecting member whereby the character images remain in focus and are properly spaced even though the photosensitive surface is maintained flat at the image plane of the system.

Description

, w 1:, XF? 3965389984 I v muumvu uaMLEIS g I} Rosin June 13, 1972 OPTICAL CHARACTER SPACING Artorney-Marechal, Biebel, French & Bugg SYSTEM F OR PHOTOTYPESETTING I [72] Inventor: Seymour Rosin, Massapequa, NY. [73] Assignee: HarrisJmenype Corporation, Cleveland, A character image PI'OJfiCUOH system successively pro ects 57 ABSTRACT Ohio image bearing light beams along a common optical axis I toward a photosensitive surface. The images of the individual [22] Filed: May 4, 1970 characters are spaced on the photosensitive surface to form I pp No: 34,300 lines of composition. The spacing is accomplished by collimat- 8 ing the image bean'ng light beams, then diverting the collimated beam by means of a movable reflecting surface into a refocusing and scan lens assembly from which the light beams 52 U.S.Cl ..95 4.s 51 Int.C1 5s FieldofSear-ch ..95 4.5

reflector may be controlled by a servo mechanism which responds to character image space information from a computer. The refocusing and scan lens assembly incorporates UNITED STATES PATENTS compensation for the angular position of the reflecting member whereby the character images remain in focus and 3,106,880 10/1963 Rossetto ...95/4.5

are properly spaced even though the photosensitive surface is 3,509,804 5/1970 Kohler "9514.5 maintained fl t at the image plans fm System,

[ 56] References Cited Primary E.raminer.lohn M. Horan 6 Claims, 4 Drawing Figures FLASH fl y t 42 SELECTOR B CIRCUITS 32 i ea umnog s5 CHARACTER ERVO SELECTOR so 6 r ---1 1o 84' MEMORY I TAPE I I CHARWIDTH READER I JUSTIFY 1 K 65 "B41b21/22 emit onto the photosensitive surface. The position of the OPTICAL CHARACTER SPACING SYSTEM FOR PHOTOTYPESETTING CROSS REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION This invention relates to high speed phototypesetting machines of the kind in which characters for the formation of lines of composition are selected from input information, usually in the form of selection codes, and image bearing light beams of the individual characters, in the order of selection, are directed to different positions on a photosensitive surface, such as photographic film or paper. In the past various arrangements have been made for the directing of the image bearing light beams to the correct positions, in succession, for spacing of the images formed on the photosensitive surface. These prior art arrangements to a great extent form a major limitation upon the total speed capacity of the system. The systems require stopping and starting of members which have appreciable inertia. In one system used in a number of different machines, the light beams are collimated and then directed into a refocusing lens and a right angle reflector assembly which are mounted on a movable carriage. This carriage is moved across the photosensitive surface by amounts corresponding to the width of the character images and thus placing the character image in proper position, in succession, to form lines of composition. This achieves variable character spacing according to the character image widths, and with lines justified by interword, and in some cases intercharacter, spacing. Another form of device employs a carriage which moves the entire width of the photosensitive sufface, for example by directing the loop of film from a supply roll into a movable carriage, whereby the loop provides sufficient flexibility to accommodate carriage movement and the carriage movement causes displacement of the light beams on the photosensitive surface. In either event, a movable carriage is required which must follow a stop-start sequence to achieve the proper character spacing. Efforts to make these carriages light in weight have been partially successful, but nevertheless there is still enough inertia involved, particularly when it is desired to achieve character images in the sum of 50 characters per second and higher, while retaining the high quality expected of phototypesetting apparatus.

Suggestions have been made in the prior art for spacing of characters on the photosensitive surface through the use of rotatable reflecting members, such as a mirror, which is moved to different angular positions and therefore reflects the image bearing light beams to different regions of the photosensitive surface in order to achieve character spacing U.S. Pat. No. 1,175,685, issued Mar. 14, 1916, discloses a typical such system, wherein the photosensitive surface is mounted in a flat image plane, and a movable optical system is incorporated in conjunction with the angularly moving mirror in order to maintain proper focus of the character images. Other suggestions have been made using angularly movable or rotatable mirrors or reflectors, in which the film is mounted along an are which has the center of rotation of the mirror as its focus. This has been found, however, to result in some distortion in the character images, since they are being focused onto the photosensitive surface along a short are, rather than over a flat plane. Furthermore, handling of photosensitive materials, particularly film, is somewhat difficult and when the film in particular is curved transversely to its length, it is difficult to maintain it accurately across the desired arc, hence this arrangement has considerable practical drawbacks.

SUMMARY OF THE INVENTION In accordance with the present invention, successive image bearing light beams of the characters to form lines of composi- 1x A I 3,668,984

tion are produced by equipment which is known per se, and the size of the images may be controlled by known meansr The path of the image bearing light beams is directed through the collimating lens system (in some cases part of the size control) which collimates the image bearing beam into parallel rays and the collimated beam is directed to a rotating reflector such as a mirror. The angular WWW trolled by a servo motor system which holds the mirror in selected different angular positions with the accuracy necessary for phototypesetting quality. The servo motor is controlled in accordance with the image width information derived at the time of selection of thecharacter, by apparatus which is per se known. The collimated beams are 'thus reflected to different locations, and a scan and refocusing lens assembly receives these beams, at the different an ular locations, from the rotatable reflector, and directs the beams onto the photosensi; tive surface. This surface, such as photographic film or paper, is mounted in an image plane and the scan lens assembly focuses the image bearing beams in this plane, to form successive properly sized images of the individual characters, in the proper succession.

With regard to this point, a desirable arrangement, and probably the most practicable one, dictates that any angular displacement of the mirror should have its counterpart in a linear displacement on the film plane. This should be true whether the angle is relatively large, such as that needed to change from the center to edge of the line, or relatively small such as that needed to change from one character to the next, and this relationship should hold anywhere in the line.

In order to achieve this, the optical system should have properties different from those of normal, or so-called distortion free, lenses. For the latter (FIG. 3, hereinafter described) consider collimated light which, falling on lens L from the left will be converged to a point A at a distance from the lens. The relationship from the diagram can then be written as:

y f tan 0 where y is the distance of .A from theoptical axis.

Relating this to an actual system, the point A is on the film and the latter is intersected by the optical axis XX in the center of the line. From equation l it is seen that the relationship between angular motion 0 in the collimated space and interval y on the film, is non-linear. Further, upon differentiating l we get dy=fsec 0d6 (2) which gives the relationship for small displacements dy on the film to d6 for angle (character interval).

By changing 1 so that it reads:

3 =f" 6 (1) and its differential then becomes dy f d6 2 and both large and small displacements become linear and independent of position on the line.

The scan lens assembly thus is of a special construction which obeys the relationship of formula 1' instead of formula I, and compensates for distortion of the image size at the extreme angular positi mwmlg eithegsidg of a mid position in which beams reflected from it would intersect the photosensitive surface at right angles. The scan lens assembly then has designed into it compensation for changes in focus due to the increase in length of the optical path as the light beams intersect the photosensitive surface at angles decreasing from at either ends of the lines being composed. Therefore, the scan lens assembly operates as a passive element which provides the necessary compensation for distortion and/or change in focus due to deviation of the light beam from direct right angle intersection with the image plane. The result is lines of composition which are in focus across the entire width of the column and character images which are sharp, not distorted, and properly spaced from each other in accordance with typographical quality.

Proper spacing and undistorted images are the most significant things about the special scanning lens design. A camera lens could serve the purpose of focusing the image on a flat plane, because the light entering the lens is collimated. The displacement of the image along the base line would not be directly proportional to the angle of rotation of the mirror, however, but it would be directly proportional to the tangent of the angle. The width of the image itself would also be proportional to the tangent of the angle of rotation.

The spacing distortion might be, with difficulty, compensated by rotating the mirror in step sizes modified by the tangent function. The angle of rotation for a character ofa given size would be different at the end of the line than at the center. But, this still would not compensate for the distortion of the width of the image. The special scan lens also accomplishes that correction, and the entire dual function is achieved in a passive element.

The primary object of the invention, therefore, is to provide a novel phototypesetting machine, and particularly a novel character spacing apparatus for such machine, wherein lightweight low-inertia moving parts are employed with novel passive or nonmoving elements for purposes of spacing the images of successively projected characters.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the phototypesetting machine and its character spacing apparatus, as provided by the invention, together with block diagram illustrations of the controls therefor;

FIG. 2 is a fragmentary view of the typical character font disc which may be employed in the apparatus shown in FIG. 1, illustrating the character selection code and the font selection prisms used in conjunction with the-character selection and projecting system;

FIG. 3 is-a diagram showing relationships in the optical system; and

FIG. 4 is a detail drawing of the scan lens.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, the character image projecting system includes a continuously rotating character font disc 10 which may be of the type shown in U.S. Pat. No. 3,223,017, although the character width information may be omitted from the disc in this particular instance. As shown in FIG. 2, the disc includes at least two font circles 11 and 12, each of which includes a full font oftype, different from the other, as a transparency through an opaque background. The character selection code, unique for each character in the font, is contained within a separate zone 14. Further details regarding the selection code and its use are described in U.S. Pat. No. 3,059,219.

The selection code in zone 14 cooperates with a pair of photocells l and cooperating light sources 16 to generate character selection pulses which are directed to selector circuits 18 that in turn control a flash control unit 20. This unit drives a high speed flash lamp 22 (or a corresponding spark gap) which creates an intense beam of light, having a short time duration in the order of a microsecond. This light passes through the font selector prisms 25 which are located on either side of the disc 10, and exits from these prisms along an optical path 26 which is common to the successively connected images. Details of the construction and operation of the font prism system are disclosed in U.S. Pat. No. 3,099,945.

The image bearing light beams then proceed through one of a plurality of sizing lenses 28 carried for example in a turret 29 such that any selected one of these lenses is movable into the optical path, thus changing the size ofthe resultant image. A1- ternatively, adjustable character sizing lenses could be employed. In any event, the sizing lens which is in the operation position produces a real image of the character at a field lens 30, which is essentially operative to gather the light rays for the further operation of the optical system. The image bearing beams proceed from the field lens 30 to a reflector system shown schematically at 32, in which the light is redirected as necessary. This system may include prisms with multiple reflecting surfaces for orienting the character images as negessary, however for simplification there is shown merely a single reflecting surface.

The light beams then pass to a collimating lens system 35. This collimating lens preferably has some adjustment of its focal length, sufficient for initial set-up and precise focusing, but once this adjustment is made, ordinarily the collimating lens is not further adjusted. The collimated light beams emitted from the collimating lens 35 are directed onto a rotatable reflector or mirror 40 which is connected to the shaft 42 of a servo motor 44 which functions as a means for selectively changing the angularity of the reflection of the collimated lens, in order to direct the collimated light beams to different portions of a photosensitive surface 45, which may be for example photographic film or paper from a supply r011 46, passing to a take-up roll 47 under the control of a motor 48 that functions as a leading or line spacing control for the spacing ofsuccessive lines of composition. The reflector 40 directs light to the plane of the photosensitive material 45 in such a way that the center ofa line to be formed on the material 45 is at a point at right angles to the beam of light coming from the reflector 40. Thus, the reflector displaces the beams to either side of this center path.

Between the reflector 40 and the image plane defined by the position of the photosensitive material 45, there is a scan or refocusing lens 50 which functions to focus the collimated light beams and thus produce areal image at the image plane and on the photosensitive material. At the same time, this scan lens provides compensation for the angularity of light beams striking the photosensitive surface at some angle less than as when the light beams are displaced to either side of the center. Obviously, the farther the light beams are displaced in either direction, the more acute this angle will become, and in an ordinary optical system this would produce blurring of the images due to change in optical path, and would also produce a distortion of the image, with the character image tending to become wider as it is displaced farther from the center mark.

The scan lens 50 thus functions as a passive element which provides for proper focus and sizing and spacing of the character images, while permitting the photosensitive material to be supported in a plane. This scan lens is ofa special design, such that light being focused by it obeys the relationship y =f' 9 rather than the more usual y f tan 9, as shown in FIG. 3.

The specifications for a typical scan lens, which has been used successfully, are as follows:

Surf. Radius C.A./2 Thickness lndex/ Elemm mm t(mm) Dispersion ment a. STOP 11.08 79.84

b. l1l.870 30.84 5.94 1.707.542 1 g. 2677.500 39.77 11.83 1.707.542 IV Various controls and devices can be used for the selection an spacing of the characters to produce justified lines of composition. By way of example the selector circuits may be of the type described and shown in 1.1.8. Pat. No. 3,339,470 issued Sept. 5, 1967. These circuits are controlled through a character selector 55 receiving character codes from a master control unit 60, particularly from its memory or register section 62.

The control unit also includes a character width memory tion system adapted to create selectively different characters along a common optical axis,

means for supporting a photosensitive surface in an image plane spaced from said projection system,

an improved optical spacing system comprising a series of optical elements including a collimating lens receiving light beams from said projection system,

selectively movable means for changing angularly the direction of the collimated beams according to desired 64, into which is loaded all of the unique typographic widths 10 character image spacing,

for the various characters on the font 10. A justification coma scan lens receiving the collimated beams from said movaputer section 65 also is incorporated in the control unit to calble means and refocusing the beams to produce images culate the widths of interword spaces necessary to make on the photosensitive surface, said scan lens including justified lines of the words and characters making up a line. means constructed and arranged to adjust the beams ac- The control unit 60 transmits character identification codes cording to the relationship to the selector 55, and width information to the mirror servo control 68 which in turn drives the motor 44. Preferably a positional encoder 69 is also driven from motor 44, and connected in a feedback loop to the servo control 68. The control unit receives input information from any suitable source, such as a tape reader 70. The reader may be used to load width information into the character width memory, and also to feed character codes and function codes to the memory 62, preferably in the form of a sufficient number of codes to complete a single line of composition and cause sufficient movement of the leading motor 48 to be ready to commence the next line.

It should be noted that while a preferred embodiment is shown in FIG. I, certain simplifications of the system are possible. The size control can be omitted, and different sizes of master characters employed, or variable character image size not provided at all. The field lens and reflector system 32 can be omitted, with the projection system (flash source and disc) feeding directly into the collimating lens 35. Also suitable choice of size control lenses, and arranging them to act as collimating lenses feeding directly to the reflector 40, can provide further simplification ofthe system.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

30 field lens.

y =f' 6, where y is the distance of the image from the intersection of the axis of the scan lens and the image plane, f is the effective focal length of the scan lens, and 0 is the angle between the collimated beams and the optical axis of the scan lens.

2. A phototypesetting machine as defined in claim 1, including a magnification lens between said projection system and said collimating lens, and a field lens receiving light from said magnification lens and gathering the light into said collimatin g lens.

3. A phototypesetting machine as defined in claim 2, including a plurality of magnification lenses and mechanism for selectively moving one of said magnification lenses into operating position between said projection system and said rotatable about an axis at right angles to such collimated beams.

5. A p'hototypesetting machine as defined in claim 4, wherein said reflecting member is rotatable about an axis parallel to the vertical dimension of the character field of the 0 character images to cause side by side spacing of the character images on the photosensitive surface.

6. A phototypesetting machine as defined in claim 5, including a servo motor connected to control the angular position of said reflecting member.

1. In a phototypesetting machine having a character projec- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 66 8 9 84 Dated June 13 1972 Inventor(s) Seymour Rosin It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: 7

Amendment A filed in the Patent Office on August 16, 1971 was partially entered during the printing of the patent. In Column 4, line 68, the following sentence was not entered by the Patent Office.

-Surface a is merely a mask opening (not shown) to the left of element I.---

Signed and scaled this 20th day of February 1973.

(SEAL) Attest:

EDWARD MFLETCHERJR. ROBERT GOTTSCHALK Commissioner of Patents Attesting Officer

Claims (6)

1. In a phototypesetting machine having a character projection system adapted to create selectively different characters along a common optical axis, means for supporting a photosensitive surface in an image plane spaced from said projection system, an improved optical spacing system comprising a series of optical elements including a collimating lens receiving light beams from said projection system, selectively movable means for changing angularly the direction of the collimated beams according to desired character image spacing, a scan lens receiving the collimated beams from said movable means and refocusing the beams to produce images on the photosensitive surface, said scan lens including means constructed and arranged to adjust the beams according to the relationship y'' f . theta , where y'' is the distance of the image from the intersection of the axis of the scan lens and the image plane, f is the effective focal length of the scan lens, and theta is the angle between the collimated beams and the optical axis of the scan lens.

2. A phototypesetting machine as defined in claim 1, including a magnification lens between said projection system and said collimating lens, and a field lens receiving light from said magnification lens and gathering the light into said collimating lens.

3. A phototypesetting machine as defined in claim 2, including a plurality of magnification lenses and mechanism for selectively moving one of said magnification lenses into operating position between said projection system and said field lens.

4. A phototypesetting machine as defined in claim 1, wherein said movable means for changing the angular direction of the collimated beams is a reflecting member intersecting the beams emitting from said collimating lens and rotatable about an axis at right angles to such collimated beams.

5. A phototypesetting machine as defined in claim 4, wherein said reflecting member is rotatable about an axis parallel to the vertical dimension of the character field of the character images to cause side by side spacing of the character images on the photosensitive surface.

6. A phototypesetting machine as defined in claim 5, including a servo motor connected to control the angular position of said reflecting member.

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