US2826634A

US2826634A - Method and means for magnetic reproduction of pictures

Info

Publication number: US2826634A
Application number: US221044A
Authority: US
Inventors: Ralph B Atkinson; Steven G Ellis
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-04-14
Filing date: 1951-04-14
Publication date: 1958-03-11
Anticipated expiration: 1975-03-11
Also published as: DE1044118B; GB725142A; FR1053634A

Description

March 1958 R. B. ATKINSON ET AL 2,

METHOD AND MEANS FOR MAGNETIC REPRODUCTION OF PICTURES Filed April 14, 1951 2 Sheets-Sheet 1 FORM MAGNETIC RECORD conT Q'Econo w m1 f mou Powum 2? D mooumoa AMPLIFIER. TRANSFER. 24 T0 sum-war j 21 ems FREQUENCY GENERATOR INVENTORS inn! 8. flzx lwsau Jrsuew 6. 11.15

March 11, 1958 R. B". ATKINSON ET AL 2,826,634

METHOD AND MEANS FOR MAGNETIC REPRODUCTION OF PICTURES Filed April 14, 1951 2 Sheets-Sheet 2 INVENTORS Raw 5. dnmvso/v draws/v G. ELL/5 United States Patent Ofiice 2,826,634 Patented Mar. 11, 1958 METHOD AND MEANS FOR MAGNETIC REPRODUCTION OF PICTURES Ralph B. Atkinson, Beverly Hills, and Steven G. Ellis, Van Nuys, Califi; said Ellis assignor to said Atkinson Application April 14, 1951, Serial No. 221,044

13 Claims. (Cl. 1786.6)

form a portion of the finished print or copy. Alternatively, it has been possible to use mechanical printing processes which generally require some form of lightsensitive materials in the production of the plate that in turn transfers ink in the desired areas and in the desired amounts to the final support. Recently, there has been developed a process making use of electrostatic forces for the attraction of a powder type of pigment, this process in general being known by the term xerography. It is always possible, of course, for an artist to trace or to make a free-hand copy of an original, but such a copy does not constitute a mechanical reproduction of the original in the usual sense of the term, and is a very expensive method of making reproductions. It is to be understood, of course, that by the term picture, we mean to include those delineations normally included in this classifictaion, together with so-called line drawings, and even type and similar forms of images which are reproduced in the same manner as pictures and line drawings, and not from so-called movable type.

While the photographic reproduction of pictures has been mechanized and simplified so that dependable, satisfactory results can be secured, this process requires the use of light-sensitive chemicals and processing chemicals of great purity, which renders the process somewhat expensive. This is particularly true where a large number of reproductions are to be made, and in addition to the expense, the processing time itself, if satisfactory results are to be obtained, is a distinct disadvantage in the use of the photographic system.

To overcome these difficulties, we have developed a method for reproducing pictures, and a means for practicing this method, in which the use of expensive lightsensitive chemicals is eliminated, with a consequent reduction of cost. In a portion of the complete method, we make use of the magnetic properties of iron and similar materials in a manner somewhat related to the magnetic recording of sound on tape.

It is therefore a major object of our invention to provide a novel method for the reproduction of pictures.

Another object of our invention is to provide such a method that uses readily available and comparatively inexpensive materials, both to form the image and to prvide a base or support for that image.

It is a further object of our invention to provide an economically practical method and means making use of that method for the reproduction of pictures in both large and small quantities.

Still another object of our invention is to provide such a method and a device for practicing this method capable of making reproductions at a rate generally intermediate that of the well known photographic process, and the mechanical printing process making use of the pressure transfer of a fluid or semi-fluid ink from rolls or plates to a support.

It is a still further object of our invention to provide a process and means for carrying out this process that can 'be used to secure reproductions of a quality equalling or exceeding the customary half-tone engravings, and capable of being used in the making of multicolor reproductions.

These and other objects and advantages of our invention will become apparent from the following description of a preferred method of practicing the invention, and of the apparatus used in this method, and from the drawings illustrating both the method and apparatus, of which:

Fig. l'is a perspective view of one form of device for producing the magnetic record used in the practice of our invention;

Fig. 2 is a fragmentary elevation, greatly enlarged, of a portion of the recording electromagnet used in our preferred form of apparatus, showing the relative location of the magnetic record material;

Fig. 3 is a schematic block diagram of a portion of the electrical components used in the magnetic record-forming device shown in Fig. 1; and

Fig. 4 is a schematic diagram illustrating the various steps in one form of our process.

Figures 5 and 6 illustrate typical apparatus which may be used in applying the magnetic particles to the record.

Figures 7 and 8 illustrate transfer of the image to another support.

Briefiy, our invention contemplates the scanning of a photograph by a small beam of light that is modulated by the picture and then falls upon a photoelectric cell. The output of the photoelectric cell is amplified and applied to a magnetic recording head that is simultane ously scanning a magnetic record member moved in synchronism with the original picture so that a magnetic record is formed having the most intense magnetization in those areas corresponding to the darkest portions of the finished copy. The magnetic record material may be in the form of a cylinder, or in the form of a sheet of material that is rolled to form a cylinder. Consequently, the magnetic record corresponds to the original picture, and to the copy that will be made from the record.

After the formation of the magnetic record, it is removed from the scanning mechanism and is dusted or lightly coated with a magnetic powder, as by flowing a mixture of oil and finely divided powder over the sheet magnetic record. The oil is then removed by a suitable solvent, as for example, carbon tetrachloride, gasoline, etc., leaving a thin coating of the iron powder. The greatest amount of powder will adhere where the magnetic intensity is the greatest, and consequently a visible indication is formed of the invisible magnetic record. Thereafter, the magnetic record is pressed against a supporting material, such as a sheet of paper, and the iron powder is transferred to the support, leaving the record material and forming a copy of the original picture. If a multicolor copy is to be made, the original picture will be scanned several times, each time through an appropriate optical filter, and a plurality of magnetic records will be made. The iron powder is such as to provide an image of the requisite color, and each of the various records, when so coated, is pressed against the support, making sure of the proper alignment of images, and a multicolor copy, comparable to that produced by the customary mechanical printing processes, is secured.

Considering .now a specific example of the process and an embodiment of the device forproducing the magnetic record, we have illustrated in Fig. 1 a preferred form of such a device. As indicated there, the numeral indicates a support such as a cabinet or other suitable means, having a power means or drive mechanism 11 that rotates a pair of mandrels' 12 and 13. For convenience, the mandrels are preferably coaxial, but as will hereafter become apparent, this is not essential. The mandrel 12 is transparent, and a light source (not shown) is located within the mandrel to project a beam of light outwardly therefrom. The mandrel 12, which is termed the master or original mandrel, is adapted to receive a transparency of a picture 14 to be copied, the transparency being wrapped around the mandrel and clamped thereto by any suitable means. A pickup head 15 is mounted on suitable guide and supporting members, and carries aphotoelectric cell receiving that portion of the light from the mandrel light source which is transmitted through the transparency 14. A lead screw 16, also driven by the power means 11, drives the pickup head from one end of the mandrel to the other, and the photocell thus scans the transparency 14 in a series of parallel lines.

In those cases where the picture to be reproduced is not in the form of a transparency, but instead is on an opaque support, a light source (not shown) may be focused on the surface of the picture to reflect into the pickup head 15 so that the latter is responsive to reflected light, rather than to transmitted light. Likewise, with transparencies, the position of the light source and the photocell may be interchanged. Regardless of which form of operation is used, however, the general operation of the device is substantially unchanged.

The second mandrel 13, which may be considered as the record mandrel, is rotated at synchronous speed with the original mandrel 12, and unless an enlargement or reduction in the size of the copy is desired, the record mandrel has substantially the same external diameter as the master mandrel 12. Wrapped around the record mandrel 13 and clamped thereto in any suitable manner is a sheet of magnetic record material, such as a sheet of so-called plastic material, coated with a suitable magnetic material such as iron oxide. The magnetic record 17 while actually in the form of a flexible sheet, is rolled to provide a cylinder having the same external diameter as the external diameter of the original picture 14 Adjacent the record mandrel 13 is a recording head 18 carried by suitable guide and supporting members and engaging a lead screw 20. The lead screw 20, like the lead screw 16, is driven by the driving means 11, and if the original picture 14 is to be reproduced without any enlargement or reduction in size, the lead screw 20 has the same lead as the lead screw 16. In this way, the pickup head 15 and the recording head 18 are synchronously moved the same linear distance along their

corresponding mandrels

12 and 13.

Within the recording head 18 is a recording electromagnet generally similar to the recording electromagnets used in the magnetic recording of sound on tape. This magnet, a portion of which is illustrated in Fig. 2, includes a pair of

poles

21 and 22 that are separated a short distance apart, and bear against the magnetic coating 23 on the magnetic record material 17. Magnetic flux lines extend between

the'poles

21 and 22 and enter into the magnetic coating 23 to m-agnetize the latter in accordance with the intensity of the magnetic field. The tips of

poles

21 and 22 are shaped to concentrate the magnetic field, in accordance with the usual practices of magnetic tape recording. 'The thickness of the

poles

21 and 22, in a direction perpendicular to the plane of the drawing, is at least as great as the lead of the lead screw 20, and under certain circumstances may be greater. If the

poles

21 and 22 are thicker than the lead of the screw 20, the turns of the helix forming the path of the poles will overlap, but since all previous records are erased each time the record material 17 is magnetized, only the record of the last passage of the magnetic coating 23 between the

pole pieces

21 and 22 will remain. It will be realized that the magnetizing of the record 17, in and of itself produces no "visible image, and the indication of a visible magnetic image in Fig. 1 is merely for better understanding of the method of scanning.

in Fig. 3, we have illustrated a schematic block dia gram of the circuit connecting the photocell in the pickup head 15 to the electromagnet in the recording head 13. In this diagram, it will be seen that the photocell, designated by the numeral 24, has its output terminals connected to a modulator 25 so that the relatively slowly varying output of the photocell may easily be amplified by an amplifier 26, and also may readily be recorded by an electromagnet 27. The output of the amplifier 26 is connected to the electromagnet 27, located Within the recording head 13, and having the

poles

21 and 22. Also connected to the electromagnet 27 is the output of a bias frequency generator 28 whose function is to generate an ultrasonic frequency that is applied to the

poles

21 and 22 of the electromagnet 27 so that the magnetic coating 23 is, in effect, demagnetized or erased of all previous magnetic recordings so that only the last recording made by the

poles

21 and 22 remains in the magnetic coating 23. The use of a bias frequency generator in the recording of magnetic tapes is well known in the art, and in and of itself, it forms no part of our invention, except as it may be combined with the other features herein described.

The modulator 25 which, in effect, provides a carrier frequency for the output of the photocell 24, normally has that frequency selected to be somewhat less than ten times the fundamental frequency of the magnetic record 17. These terms may be somewhat better understood from the following description.

As previously mentioned, it will be appreciated that the

poles

21 and 22 of the recording electromagnet move relative to the surface of the magnetic record material 17 so that the path they trace is a helix. When the record material is removed from the recording mandrel 13 and flattened, the path appears as a series of straight parallel lines having a width equal to the lead of the screw 20. Each of these lines is substantially uniform throughout its width, and the intensity of the magnetic record of any individual area of the line is the integrated value of the light received by the photoceii 24 from a corresponding area of the original picture 14. If the elemental area under consideration is a square, it can easily be seen that the definition and resolution of the finished copy will be determined by the size of the square, in much the same way that the definition and resolution of the halftone engraving is determined by the number of dots or lines per inch. if a half-tone engraving is made with sixty lines per inch, there are a maximum number of sixty dots for each lineal inch of the screen. On the other hand, if the engraving is made with a screen having one hundred forty-four lines per inch, there are a maximum of one hundred forty-four dots per lineal inch. It is neither necessary nor desirable that there be greater definition and resolution in one direction than in another, and consequently half-tone screens are made so that, for example, a sixty line screen will have sixty dots or lines per inch measured in a vertical direction, and sixty dots or lines per inch measured in a horizontal direction.

By the same reasoning, if the path of the

pole pieces

21 and 22 is i of an inch wide, corresponding to one hundred lines per inch, the elemental area under consideration should be a square of an inch on each side. If the area is more than 5 of an inch long, resolution in a horizontal direction will be unduly limited. On the other hand, if the area is less than 4 of an inch long, the same resolution will be greater than necessary. Consequently, the number of lines per inch, measured along the axis of the recording mandrel 13 determines the definition and resolution of the finished magnetic record 17.

Assuming that the lead screw 20 produces a finished magnetic record 17 having a resolution of one hundred lines per inch, and assuming that the outer surface of the magnetic record has a peripheral speed of fifteen inches per second, it will be seen that the electromagnet 27 must be able to record fifteen times one hundred or one thousand five hundred cycles per second. This frequency is known as the fundamental picture frequency, and will be dependent upon the resolution of the finished magnetic record 17, measured in lines per inch, and the peripheral speed of that record when it passes beneath the recording head 13, measured in inches per second. Thus, if the resolution were to be one hundred lines per inch, and the peripheral speed were thirty inches per second, the fundamental frequency would be three thousand cycles per second.

While the fundamental frequency may actually be found in certain magnetic records, this does not often happen. Instead it is more likely that there will be relatively large areas of the original picture 14 where little or no change in light intensity occurs, and consequently there should be little or no corresponding change in the intensity of the magnetic record recorded by the

poles

21 and 22. While a so-called direct current amplifier would meet the limitations imposed by these conditions, such amplifiers are generally somewhat more expensive and less satisfactory for commercial service and operation. If the output of the photocell 24 is used to modulate a higher frequency alternating current, a more conventional amplifier may be used, resulting in lower costs and greater reliability. If the fundamental picture frequency is considered, the carrier frequency which the output of the photocell 24 modulates normally should be somewhat less than ten. times the fundamental picture frequency. While the maximum permissible carrier frequency is determined by the peripheral speed of the magnetic record 17 and the separation of the

poles

21 and 22, it is clearly desirable to keep the carrier frequency to as low a value as possible consistent with good results, since in this way less expensive and critical amplifier design may be used.

The theoretical maximum value of the carrier frequency can be determined by a consideration of the gap or separation between the

poles

21 and 22, and the peripheral speed of the magnetic record 17. It is well known in magnetic tape recording that when the frequency of the information being recorded upon the tape equals the number of gap widths that the tape moves per second, there is an excessive attenuation of the information recorded upon the tape. For example, if the gap width is of an inch, and the tape or magnetic record material 17 moves at the peripheral speed of fifteen inches per second, the tape Will move fifteen thousand gap widths per second. Consequently, there will be a very great attenuation of a signal having a frequency of fifteen thousand cycles per second. This phenomenon is well known, and is generally referred to as gap attenuation, and is comparable to a similar situation occurring in the recording of sound on motion picture film where the phenomenon is known as slot cancellation.

We have found that if the carrier frequency is approximately of the frequency at which gap attenuation occurs, very satisfactory results are obtained. While the use of the carrier frequency will theoretically provide a modulation of the resulting magnetic record, in practice this carrier modulation, which is at a frequency approximately eight times that of the fundamentaltpicture frequency, is undetectable except by a microscope or similar means. The moire that might be expected to appear under these circumstances has not been detected, and it is very possible that the presence of alternate areas of opposite magnetic polarity causes a bridging effect of the magnetic particles later applied, so that the optical effects of the carrier frequencies are suppressed, if not completely eliminated.

The bias frequency generator 28, whose use is well known in the art of tape recording, preferably has a frequency approximately twice that of the carrier frequency provided by the modulator 25, so that the bias frequency does not appear as a ripple or pattern in the final magnetic image.

After the magnetic record material 17 has been completely scanned by the recording head 18, the record is removed from the mandrel 13, and is coated with a very finely divided iron or similar magnetic powder. While this may be accomplished in a number of different ways, one method of doing this is to blow the finely divided powder on to the matrix 17 as by a dust gun 30 of any well known suitable type, as shown in Figure 5, for example. If the magnetic record 17 is in the form of a sheet that has been curved around the mandrel 13, the sheet may be flattened, and placed in a tray where it is coated with the powder, preferably by flowing a liquid over the magnetic record, the liquid comprising a ve- 'hicle, such as oil, and a magnetizable powder, such as carbonyl iron powder, iron oxide powder, or other suitable material. This procedure is illustrated, by way of example, in Figure 6 where the flattened record or matrix 17 has been placed in a tray 31 containing a liquid 32, which includes a vehicle and a magnetizable pow der, and the tray is then rocked back and forth. After the magnetic record 17 is thoroughly and uniformly coated, it is removed from the liquid and allowed to drain, thereby removing the surplus liquid and consequently the surplus iron powder. Thereafter, the vehicle is removed by a suitable agent, such as carbon tetrachloride, gasoline, or similar solvent if oil has been used as the vehicle. This step may likewise be carried out in a tray, in the same general manner as used in applying the liquid. The solvent is then allowed to evaporate from the surface of the magnetic record 17, and at this time a clearly visible image may be seen upon the surface of the magnetic record. While normally this is only an intermediate stage of the complete process, under certain conditions this may be considered as the end result, particularly if the magnetizable powder has been selected to have a color contrasting with that of the magnetic coating 23 of the magnetic record 17.

However, assuming that the complete process is to be used, the next step is the transfer of the magnetic particles from the magnetic record 17 to their final support. This can be done, for example, by pressing the coated matrix 17 against a final support 33, such as a sheet of paper, by rubbing with the side of the hand, as illustrated in Figure 7, or by passing the matrix and final support between a pair of

rollers

34 and 35, as shown in Figure 8, in addition to other well known methods. If the particles are finely divided and dispersed iron or one of its compounds, without any coating thereon, it is generally desirable that the final support, such as paper, be coated with some material, such as gelatin or a sizing, that will act as an adhesive for the particles and insure their removal from the magnetic field temporarily holding them to the magnetic record 17. Under certain conditions, it is both desirable and practical to coat the iron particles with a suitable pigment or vehicle containing a pigment, and under these conditions, the final support may be dampened with a suitable solvent for the pigment or vehicle to insure the transfer of the latter from the magnetic record 17 to the final support. While magnetic powders may be obtained in various colors, it is not al- "'7 ways possible to obtain the particular colorTdesir ed, and consequently the coated powders offer substantially unlimited color variations. This use of the coated powder is particularly desirable where multicolor prints are to be made, since in this way the'colors may be balanced as conditions require.

After the magnetic record has transferred its coating of magnetic powder to the final support, the record may again be coated and re-used to produce a large number of prints. If only a small number of prints are to be made from a magnetic record 17, it is usually more convenient to use .this record in the form of a relatively fiat sheet that is handled as just described. However, if a great number of copies are to be made, it is generally preferable to retain the record in its cylindrical form, coating it with the magnetizable powder or pigment-like material while in the cylindrical form, and then transferring the pigment-like material to the final support in a manner similar to that employed in the rotary press or duplicator. By the term pigment-like material, we

mean to include both the uncoated magnetizable powder of any color, as well as the coated magnetizable powder preveiously described. In each case, it will be appreciated, the magnetizable material acts in the general manner of a pigment so that an optical contrast is produced between the magnetizable material and its final support.

As previously suggested, the magnetic record material 17 may be considered as the final support if the magnetizable powder that is flowed over it produces an optical contrast between the powder and the magnetic coating 23 of the record. In this connection, it will be realized that the magnetic coating 23 may be of any suitable ferromagnetic material of high retentivity, and such materials are available in different colors. Such coatings at present are commonly available in both red and black, and if a red coating is selected, for example, a black magnetizable material may be flowed over the magnetic record 17 to provide the desired visible image.

It should be noted, however, that the use of the magnetic record 17 as the final support for the image is a relatively expensive procedure. Magnetic material of the type forming the magnetic record 17 is considerably more expensive than paper, and if the record is used as the final support, it cannot later be used without destroying the image formed on it. One of the principal advantages of our invention is that it permits the reproduction of pictures at a low cost, and by transferring the picture or image from the magnetic record 17 to a less expensive support, such as paper, the record may be re-used, thereby materially reducing the cost of the finished print. Furthermore, by using the magnetic record 17 as the final support, only one copy or print may be secured unless the original picture or image 14 is scanned a number of times. Consequently, from economics of the situation, if a number of copies of the same image are to be made, the magnetizable material will be transferred from the magnetic record 17 to a final support. If only a single print is to be made, it is still less expensive to transfer the image to a final support other than the magnetic record, at least insofar as the cost of materials is concerned.

It will be noted that in transferring the magnetizable material forming the image from the magnetic record 17 to the final support, the image is reversed, from right to left. Consequently, it is important in making the magnetic record 17 that this be kept in mind. If the original picture or image 14 is in the form of a transparency, a right-to-left reversal may be accomplished by placing the transparency on the mandrel 12 so that the front or forward surface is facing inwardly, against the surface of the mandrel. If this is done, the magnetic image formed on the magnetic record 17 will be reversed, from right to left, and when the second reversal is accomplished, in the transfer of the magnetic material from the magnetic 8 record to the final support, the picture will be seen in its normal, unreversed, condition.

Where the original picture or image 14 is not in the form of a transparency, but must be scanned by reflected light as previously described, the rotation of the lead screw 20 may be reversed so that the pickup head 15 and the recording head 18 move in opposite directions. This accomplishes a top to bottom reversal, but when the final image on the magnetic record 17 is viewed in its normal position, it will be found that a right-to-left reversal has occurred.

If the size of the copy or reproduction is to be different from that of the original 14-, this may be accomplished at the time of making the magnetic record 17. When doing this, it is necessary to insure the synchronization of the recording head 18 with the pickup head 15, and this is done by turning both the master mandrel 12 and the record mandrel 13 at the same angular velocity. If the diameter of the record mandrel 13 is then made greater than that of the master mandrel 12, the circumference of the record mandrel is increased and one dimension of the magnetic record 17 must be correspondingly increased. To retain the same proportions of the finished copy, and to prevent distortion, the length of the record mandrel 13 must be increased in the same ratio as its diameter was increased, and the lead screw 20 must be changed so that the recording head 17 traverses the increased length of the mandrel in the same length of time as before. When these changes have been made, the magnetic record 17 that is then produced will be mechanically enlarged from the size of the original 14. Reduction of the magnetic record may be accomplished in the reverse manner from that described. By replacing the photocell of the pickup head with a magnetic pickup, and by placing a magnetic record 17 on the master mandrel 12, magnetic records may be magnetically reproduced, and may simultaneously be enlarged or reduced.

While it is usually more convenient to have the master mandrel 12 and the record mandrel 13 driven by the same power means 11, this is not necessary, and separate drive or power means may be used so long as the mandrels are rotated in synchronism. If this is done, the mandrels may be separated any desired distance, varying from a fraction of an inch, to thousands of miles.

It will be appreciated that it is possible to change the operation of the amplifier 26 so that instead of causing the greatest energization of the electromagnet 27 when the photocell 24 receives the least amount of light from the original picture 14, the electromagnet will be most strongly energized when the photocell receives the greatest amount of light. in this way, it is possible to form positive magnetic images from positive" or negative original pictures. Similarly, the response of the amplifier may be made suitably non-linear to compensate for non-linear response of the photocell 24, and attenuation and non-linear response of the electromagnet 27 and magnetic record material 17, thus providing a control of the brightness and contrast levels of the finished print. Expressed differently, the amplifier 26 may be used to match the available characteristics of its input circuit to its output circuit.

From the foregoing, it will be seen that we have provided a new method of reproducing pictures or images that is fully capable of accomplishing the objects and securing the advantages heretofore stated. One of the features of our invention is that it may be used to produce high quality work, having good definition and resolution, at a high rate of speed. Furthermore, this may be accomplished without the use of a dark room, so that the various steps may be accomplished in full light, permitting the inspection of the process and product at all stages. The equipment is readily portable and service and maintenance requirements are reduced to a minimum, by making the recording head 13 in a manner to facilitate replacement of the electromagnet 27 and its associated

poles

21 and 22, electromagnets having various gap widths may be used to meet the special requirements of diiferent jobs.

It will be apparent that changes and modifications may be made in both the particular process described, and in the particular form of apparatus used. These changes which occur to' those skilled in the art are considered to be within the broad scope of our invention, and consequently we do not wish to be restricted to the particular steps described, nor their precise sequence, nor to the particular form or arrangement of parts herein described and shown, except as limited by our claims.

We claim:

1. The method of reproducing images which includes the steps of: forming a magnetic replica of said image; applying an excess of a liquid mixture of a vehicle and a pigment-like material having ferromagnetic properties to said magnetic replica; removing the excess of the mixture not held by magnetic attraction to the replica; and adding a solvent to remove the vehicle from said replica, leaving said material distributed thereover in proportion to the residual magnetism remaining in said replica, whereby a visible image is formed.

2. The method of reproducing images which includes the steps of: forming a magnetic replica of said image; applying an excess of a liquid mixture of a vehicle and a pigment-like material having ferromagnetic properties to said magnetic replica; removing the excess of the mixture not held by magnetic attraction to the replica; adding a solvent to remove said vehicle from said replica, leaving said material distributed thereon in proportion to the residual magnetism remaining in said replica; and transferring said material from said replica to a final support, thereby forming a visible copy of the image reproduced.

3. The method of reproducing images which includes the steps of: scanning said image, in a series of parallel lines, with means to produce an electric current varying in accordance with the graduations of said image; using said electric to modulate a carrier current that is applied to an electromagnet; causing said electromagnet to scan a magnetic record material in a series of laterally aligned parallel lines to form a magnetic replica of said image; applying a finely divided pigment-like material having ferromagnetic properties to said magnetic replica; subjecting said pigment-like material to mechanical forces that tend to remove it from said replica except where held thereto by magnetic attraction, leaving said material distributed thereon in proportion to the residual magnetism remaining in said replica; and transferring said material from said replica to a final support, thereby forming a visible copy of the image reproduced.

4. The method of reproducing images which includes the steps of: scanning said image with a photocell, said scanning being accomplished in a series of parallel sweeps in the form of narrow lines across said image; using the output of said photocell to modulate a carrier frequency; amplifying said modulated carrier frequency and thereafter applying it to the input terminals of a recording electromagnet; scanning a magnetic record material with said electromagnet in synchronism with said scanning of said image by said photocell to form a magnetic replica of said image; applying a mixture of a vehicle and a pigment-like material having ferromagnetic properties to said magnetic replica; removing said vehicle from said replica, leaving said material distributed thereon in proportion to the residual magnetism remaining in said replica; and transferring said material from said replica to a final support, thereby forming a visible copy of the image reproduced.

5. A device for producing a magnetic record of a visual image to be reproduced, which includes: a photocell; a first mandrel adapted to receive said image and rotate it with respect to said photocell so that the latter scans said image; a light source positioned to project a beam of light from said image to said photocell, the intensity of said light beambeing controlled by the optical effect of said image; a first lead screw connected to said photocell in a manner to move said photocell along the length of said mandrel as the latter is rotated; means driving said first mandrel and said first lead screw; a modulator connected to the output of said photocell, said modulator having a carrier frequency oscillator operating at a frequency slightly less than that at which gap attenuation occurs, whose output is modulated by the output of said photocell; an amplifier connected to the output of said modulator; a recording electromagnet connected to the output of said amplifier and adapted to electromagnetically record said modulated carrier on a magnetic record material; a second mandrel adapted to receive a magnetic record material and rotate it with respect to said recording electromagnet so that the latter scans said record; a second lead screw connected to said recording electromagnet in a manner to move said electromagnet along the length of said second mandrel as the latter is rotated; and means driving said second mandrel and said second lead screw in synchronism with said firstmandrel and said first lead screw, respectively.

6. The method of producing a magnetic record of a visual image which includes: scanning said image to develop an electrical signal varying in amplitude in accordance with variations in the characteristics of the image; modulating a high frequency carrier with said signal to produce a modulated carrier current; energizing a magnetic recording head with said modulated carrier current; and scanning a magnetizable record material, in a series of laterally aligned side-by-side lines, with said magnetic recording head, whereby a magnetic replica of said image is provided.

7. The method of producing a magnetic record of a visual image which includes: scanning said image to develop an electrical signal varying in amplitude in accordance with variations in the characteristics of the image; modulating a carrier current of frequency about of the frequency at which gap attenuation would occur with said output to provide a modulated carrier current; energizing a magnetic recording head with said modulated carrier current; and scanning a magnetizable record material with said magnetic recording head, whereby a magnetic replica of said image is provided.

8. The method of producing a magnetic record of a visual image which includes: scanning said image to develop an electrical signal varying in amplitude in accordance with variations in the characteristics of the image; providing a carrier current whose frequency is several times the highest frequency that said output may have and slightly less than the frequency at which gap attenuation occurs; modulating said carrier current with said output to provide a modulated carrier current; arnplifying said modulated carrier current; energizing a magnetic recording head with said amplified modulated carrier current; and scanning a magnetizable record material with said magnetic recording head, whereby a magnetic record of said image is provided.

9. A device for producing a magnetic record of a visual image to be reproduced, which includes: a pickup means for producing an electrical signal varying in amplitude in accordance with gradation of said image; means for scanning said image by said pickup means to cause the path of said pickup means to cover said image in a series of side-by-side lines; an oscillator and modulator connected to said pickup means and acting to modulate higher frequency oscillations in accordance with the output of said pickup means, the frequency of said oscillator being slightly less than that at which gap attenuation occurs; an amplifier connected to the output of said oscillator and modulator; a recording electromagnet connected to the output of said amplifier means; and means for scanning a magnetic record material with said recording electromagnet in synchronism with said scanning of said image by said pickup means, the path of said recording electromagnet across said record material being in a series of side-by-side lines, whereby a magnetic replica of said image is produced,

10. The method of reproducing a visual image which includes the steps of: developing an electrical signal varyin ma nitude in'accordance with gradation of the image, modulating a carrier with said signal to produce a modulated signal, magnetizing a record material with said modulated signal to form a magnetic replica of said image, wherein the gradations of said image are reproduced as variations in residual magnetic intensity in said replica; applying a flowable pigment-like material having ferromagnetic properties to said record material; and subjecting said pigment-like material to mechanical forces tending to remove it from said record material except where held thereto by magnetic attraction in amounts corresponding to said residual magnetic intensity, Whereby a visible image is formed having substantially the gradations of said image being copied.

11. The method of producing a magnetic replica of a visual image which includes the steps of: scanning said image to develop an electrical output varying in amplitude in accordance with variations in the characteristics of the portion of the image being scanned; modulating a carrier current by said output of said scanning means, said carrier current having a frequency several times the highest frequency of said output of said scanning means and slightly less than that at which gap attenuation occurs; energizing an electromagnet with said modulated I icr current; and scanning a magnetizable record material with said electromagnet in a manner corresponding to the scanning of said image, whereby said record ma terial is magnetized in a manner corresponding to the variations in said modulated carrier current to produce a magnetic replica of said image.

12. The method of reproducing a visual image which includes the steps of: scanning said image with means to produce an electric signal varying in accordance with the gradations of said image; modulating a high frequency carrier current with said signal to provide a carrier signal modulated in accordance with the gradations of said image; applying said modulated carrier signal to an electromagnet; causing said electromagnet to scan a magnetic record material in synchronism with the scanning of said image to form a magnetic replica of said image; applying a fiowable magnetic pigment material to said record material; and removing the excess of said pigment material from said record material so that said pigment material adheres to said record material in amounts varying with the residual magnetism of said record material, whereby a visible image is formed. w

13. The method of reproducing a visual image which includes the steps of: scanning said image with means to produce an electric signal varying in accordance with the gradations of said image; modulating a high frequency carrier current with said signal to provide a modulated carrier signal, said carrier current having a frequency several times greater than the highest fequency of said electric signal and less than the frequency at which gap attenuation occurs; applying said modulated carrier signal to an electromagnet; causing said electromagnet to scan a magnetic record material in synchronism with the scanning of said image to form a magnetic replica of said image; applying a iiowable magnetic pigment material to said "record material; and applying mechanical force tending to remove said pigment material from said record material, whereby the excess of said pigment material is removed, non-magnetized portions of said record material having substantially no pigment material left thereon and magnetized portions having amounts left thereon varying with the residual magnetism of said portions, whereby a visible image is formed.

References rCitc-d in the tile of this patent UNlTED STATES PATENTS Re. 22,869 Hueber Apr. 15, 1947 1,426,384 Hoke Aug. 22, 1922 1,590,399 Tykocinski June 29, 1926 1,867,542 Hammond July 12, 1932 1,917,509 Ybarrondo July 11, 1933 1,945,626 Baird Feb. 6, 1934 1,974,911 Buecker Sept. 25, 1934 2,236,373 Kowalski Mar. 25, 1941 2,517,808 Sziklai Aug. 8, 1950 2,520,761 Giel Aug. 29, 1950 2,530,564 Blaney Nov. 21, 1950 2,572,550 White Oct. 23, 1951 2,573,881 Walkup Nov. 6, 1951 2,657,932 Blaney Nov. 3, 1953 2,698,875 Greenwood Jan. 4, 1955 FOREIGN PATENTS 475,383 Great Britain Nov. 18, 1937 456,810 Great Britain Nov. 16, 1936 OTHER REFERENCES Magnets, Underhil, 1st ed., 1924; page 317. Copy in Div. 48.

Mechanics Magazine, vol. 31; A. D. 1839, page 31.

I U. S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,826,634 Ralph B. Atkinson et 31. March 11, 1958 It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 9, line 39, for "graduations" read gradations line 40, after "electric? insert current 3 column 10, line 63, for "gradation" read gradations line 69, for "higher" read high column ll, line '7, for "gradation read gradations --3 column 12, line 9, for feqnency" read frequency Signed and sealed this 17th day of June 1958.

(SEAL) Attest:

KARL H. AXLINE I ROBERT C. WATSON tt sting icer Conmissioner of Patents U. 3. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,826,634 Ralph B. Atkinson et a1. March 11, 1958 It is hereby certified that error appears .in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 9, line 39, for "graduations" read gradations line 40, after "electric" insert current column 10, line 63, for "gradation" read gradations line 69, for "higher" read high column 11, line '7, for "gradation" read gradations column 12, line 9, for "fequency" read frequency Signed and sealed this 17th day of June 1958.

(SEAL) Attest:

KARL H.

AXLINE ROBERT C. WATSON Attesting Officer I Commissioner of Patents