US2358678A - Facsimile apparatus - Google Patents

Description

- Sept. 19, 1944. c. J. YOUNG FACSIMILE APPARATUS Filed Dec. 24, 1941 2 Sheets-Sheet l INVEINTOR fiar FZZJJG A'iTORNEY Patented Sept. :19, 1944 UNITED STATE rscsmmn s'rrmrus Charles J. Young. Ardmore, 2a., assignmto Radio Corporation of America, a corporation of Delaware Application December 24, 1941, Serial No. 424,275

(Claims.

the transmission and reproduction of intelligence,

and more particularly to the transmission and reproduction of facsimiles.

The art of facsimile transmission and reception has been developed to a high degree, and is be ing found particularly useful at the present time for the transmission of messages by so-called tape type of facsimile wherein the intelligence to be transmitted is recorded on a comparatively narrow tape, in contradistinction to the normal facsimile transmissions wherein a comparatively large sheet is used in the nature of a photograph or the like. Accordingly, it is one of the objects of my invention to provide an apparatus which will be particularly useful for the transmission and reception of optical images recorded on a comparatively narrow tape.

One of the disadvantages attendant the transmission of facsimiles of the tape type is the fact that the average scanning arrangement is too bulky and is .not adaptable for this problem, but special scanning arrangements must be utilized. Accordingly, it is another of the objects of my invention to provide a scanning arrangement which will be particularly useful for the scansion of facsimiles recorded on narrow bands of tape.

In facsimile transmission known to the prior art it has been customary to develop a continuous signal, and this signal is then chopped, as illustrated in United States Patent #1389587 granted January 20, 1931, as exemplary of chopping apparatus, and the result is a series of modulated pulses. According to the present invention the chopping is accomplished by the scanning element per se, thus minimizing the amount of equipment necessary.

Also at the present time facsimile transmissions of the tape type have found interest for such as the transmission of orders to police cars. and particularly at the present-time it is findin interest in the transmission of intelligence to and from aircraft and particularly military aircraft.

My invention, in general, contemplatesthe use of a transparent or translucent tape on which is recorded or marked the intelligence to be transmitted. This tape is passed between a. light masking arrangement which admits a slit of light which (Cl. 178-73) My invention relates. in general, to devices for passes normally through the tape and a scanning arrangement. The scanning arrangement consists in a small cylindrical member having cut through the surface thereof a plurality of small holes spaced apart a short distance from. each other and the entire group forming a spiral around the periphery of the cylinder of either 360 or 180, asmay bedesired. Positioned inside the cylindrical arrangement which is rotated is a photocelland, as the cylinder is moved, there will be developed a chopped tone due to the spacing of the holes or apertures from each other Referring to Fig. 1, there is shown in elevation a schematic arrangement of a transmitter according to my invention. In this figure a supply roll it of a thin narrow transparent or translucent tape is provided and is fed through guide rollers ll into contact with a plate I 2.- The intelligence to be transmitted ma be written on the tape or recorded on the tape in a suitable fashion at this stage of the transmission. The

tape passes thence through guide rollers 13 and the tape I I is looped as illustrated and passes thence between guide rollers it. A source of light it is provided which passes through lens I! and thence through an aperture in a masking arrangement consisting of elements 18 and it. Such masks are well known per se, and accordingly will not be described in detail here, but all that is necessary is that the mask will admit and allow to pass therethrough a strip of light which. in general, should consist of a sti'ipof the width of a scanning line of the intelligence to be scanned.

Positioned adjacent the masking arrangement and spaced apart therefrom is the scanning cylinder 20 having a plurality of apertures cut through the outer surface thereof, andwhich will be described and, illustrated in greater detail hereinafter in the description of Fig. 2. Positioned on the inside of the cylinder is a photocell 2| having the anode thereof positioned so as t any aperture in the scanning cylinder which comes within the path of the slit 01' light. Signals from the photocell are passed to appropriate amplifying means. The tape on which the intelligence is recorded is passed between the masking arrangement and the'scanning cylinder so that portions of the slit of light will be blocked by the opaqueness o! the intelligence recorded on the tape. Hence, as the cylinder is moved the holes will progress steadily across the slit of light which has been intercepted in part by the material on the tape, and rotation of the cylinderwili pass the apertures from one side or the tape to the other so as to scan a single line by the complete rotation of the scanning if the apertures are cut so as to form a 360 spiral. Of course, for special purposes a 180 spiral might be utilized, but since the particular length of the spiral is not of the essence of this invention, this particular arrangement need not be discussed here as to the length of the spiral utilized.

Referring to Fig. 2, there is shown a perspective view of the scanning arrangement. As illustrated in this figure, a driving motor 30 having a shaft 3| has fastened to the shaft thereof the member 20 having a cylindrical section and into. the cylindrical section is cut the plurality of holes 32 spaced apart from each other by slight amount and being arranged in a spiral form of chopped signals representative of the optical valuesalong a line of the tape will be transmitted. The tape is moved forward slowly relatively to the scanning by each aperture and, in general, advances a single line during the time that the cylindrical member revolves and scans an entire line thereof.

It will be appreciated that an arrangement similar to the present arrangement for scansion purposes might be used at the receiver as well Such an arrangement would be very useful, since around the periphery of the cylindrical section.

The light source l6 sends a beam of light through the lens I] and thence through the masking means comprising the sections l6 and l9,-and from there through the transparent tape and through the aperture in the cylindrical section 20 which at the particular instant happens to be adjacent the slit in the masking means. The light beam passing through the masking slit should form a fairly intense linear section of light which is the width of the displacement between the aperture at one end of the spiral and the aperture at the other end of the spiral on the scanning cylinder. This is indicated at 35. The photocell 2| positioned inside the scanning cylinder is indicated with the leads thereof positioned on the outside and in a readily accessible position. No means have been shown for holding the photocell in a particular position, nor for holding the masking means in a particular position, since well known means may be used for this purpose, and since these means do not form a part of the invention perse.

This operation of the device is as follows. The tape containing'the intelligence to be transmitted is passed slowly between the masking arrange- .ment and the scanning element and a beam of light rplays therethrough, striking the outer surface of the scanning member 20. As the scanning member is rotated a single hole or aperture will appear between the photocell and the beam of light passing through the masking aperture, and the optical value of the elemental section of the tape adjacent this hole will be transmitted to the photocell and an electridal impulse developed, As the cylinder member 20 rotates this aperture will pass out of the: beam, and an opaque section between this aperture and the adjacent aperture will then interrupt or chop the light to the photocell. As the rotation continues the next aperture comes in to the beam of light at a position adjacent that at which the first aperture intersected the beam of light, and as this cycle goes on progressively each aperture will come in to the beam of light and transmit the optical value of the tape at the particular point at which it is adjacent thereto. Hence, a set it will be seen that the elements forming the scanner at the transmitter might, by slight rearrangement and by the use of a modulated light source such as a lamp rather than a photocell, be utilized as a receiver and thus the two arrangements might almost be completely.interchangeable.

Referring to Fig. 3, there is shown a partial view of the tubular member 20. In this view the tubular member has been cut and has been brought into the plane of the paper and the section illustrated herein represents that section which would be seen-where the spiral apertures begin and end. In this illustration 9. full 360 spiral has been used. The numerals on the left hand side refer to inches and actually a tubular member of approximately four inches in circumierence has been found to be very practical. As shown, there might be provided twenty scanning apertures, each aperture being two hundredths by one tenth of an inch. If this be done and the tubular member is revolved at the rate of sixty revolutions per second, there will be a 1200 cycle sub-carrier developed and the signal de-.

one hundredth of an inch in diameter and the tubular member was revolved at the rate of sixty revolutions per second, there would be developed a 6,000 cycle sub-carrier. Such a design as this would be used in a case where the transmission was to comprise D. C. impulses or sub-carrier frequency modulation. The 6,000 cycle carrier would permit stable alternating current amplifiers to be used in conjunction with the photo tube and the signal could be subsequently rectified to give well formed direct current impulses to control, for example, a frequency modulator. Present practice has tended toward sub-carrier frequency modulation, particularly for use with so-called tape facsimile transmissions.

It will be appreciated that there may be other departures which will fall fairly within the spirit and scope of my invention, and I claim all such departures falling fairly within my invention as identified in the hereinafter appended claims.

What I claim is: a

1. The method of scanning an optical image including the steps of developing signals representative of the optical value of an elemental section of the image, interrupting the development of the signals for a time period substantially commensurate with the period of signal development, and developing signals representative of an additional elemental area after each interruption,

whereby light values are translated into electric frequency measured by the rate at which the signals are developed and interrupted.

2. Apparatus for developing electrical signal energy indicative of the variations of light intensity of elemental areas of an optical image .edge of the tubular'member, means for projecting an optical image upon the tubular member through the slot in the masking element, a light translating element positioned to receive the light of the optical image as projected through the slot in the masking element and individual apertures of the tubular member to translate said light values into proportional strength electric currents, and means for rotating the tubular member relative to the masking element so that the I currents superimposed upon a predetermined tone width of the slot is scanned by the said apertures and simultaneously a predetermined chopper frequency is generated due to the revealing and eclipsing of the light from the light translating element.

3. Apparatus for developing recurring electrical.

signals indicative of the optical values of an optical image, comprising a source of light, a tubular member having a plurality of spaced apertures arranged helically around the periphery of said tubular member, masking means positioned for admitting therethrough a beam of light of elemental width, means for directing the optical image to be scanned between said tubular member .and said source of light, means. for rotating said tubular member, and photoelectric means positioned so as to have light from said beam of light within the field of said beam of light and representative of said optical values directed by said tubular means onto said photoelectric means.

4. Apparatus for developing recurring electrical signals indicative of the optical values of an optical image, comprising a source of light, a tubular member having a plurality of spaced apertures in the periphery thereof, masking means positioned for admitting therethrough a beam of light of elemental width, means for directing the optical image to be scanned between said tubular member and said source of light, means for rotating said tubular member, and photoelectric means positioned within said tubular member so as to have light from said beam of light within the fleld oi said beam of light directed by said tubular means onto said photoelectric means and wherein light representative of said optical values is directed onto said photoelectric means by the pas-- sage of the apertures in said tubular member sequentially through the beam of light.

. CHARLES J. YOUNG.

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