Multiple Head Ink Drop Graphic Generator

Abstract

A method of and apparatus for reproducing a graphic representation includes a scanner for scanning the original along a series of contiguous lines and transmitting an analog signal proportional to the intensity of the scanned area to an analog to digital convertor to provide a series of parallel, binary signals. Circuitry is provided which permits the digital signals to be stored and retrieved as a number of simultaneous signals from corresponding points in an equal number of transverse bands across the original. The retrieved digital signals are then used to control a bank of drop projectors, equal in number to the transverse bands, which project drops toward a receiving member mounted on a rotating cylinder, with the drop generators moving incrementally, axially of the cylinder, one line spacing each revolution of the cylinder to cause the reproduction to be produced as a series of contiguous, transverse bands corresponding to the transverse bands of the original.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

METHOD AND SYSTEM FOR RECONSTRUCTION OF IMAGES, by David Behene et al., application Ser. No., 803,910, filed Mar. 3, 1969, now U.S. Pat. No. 3,604,846.

Printing apparatus has been proposed wherein a series of printing heads, each capable of projecting a jet of coating material, are mounted in uniformly spaced relationship to each other and adjacent a moving web to project a series of streams of coating material onto the web. See for example the U.S. Pat. to Ascoli, No. 3,136,594, issued June 9, 1964. In apparatus of this type the jet of coating material is charged as it leaves each of the coating nozzles and deflecting electrodes are mounted just downstream of the outlet from the nozzle and the electrostatic field set up by the electrodes varied to control the trajectory of the jet issuing from the nozzle. In order to insure complete transverse coverage of the web, the coating heads are mounted on a pair of spring steel blades and oscillated back and forth across the web as the web moves past the nozzles.

While this type of construction permits simultaneous printing of the web in a series of transverse bands, and thus obviates the necessity of, for example, printing sequentially across the web, it will be apparent that the relative movement between the web and the coating heads resulting from the oscillation of the coating heads on their spring steel supports necessitates modulation of the electrostatic field to compensate for this relative movement. Thus, in addition to the electrodes for controlling the trajectory of the coating jets to form characters of the desired shape, it is also necessary to provide additional electrodes to modify the trajectory of the jets and compensate for the relative transverse movement between the web and the coating heads.

The patent to Ranger et al., U.S. Pat. No. 1,817,098, issued Aug. 4, 1931, also discloses a system in which an image is reproduced by projecting coating material through an electrostatic field toward a receiving member mounted on a rotable cylinder. In this system uncharged drops are imprinted upon the receiving member while charged drops are deflected by the field into a catcher and removed for recirculation. In this system it is necessary for all of the coating nozzles, each of which projects coating material of a different color, to traverse the entire width of the receiving member in order to reproduce an image corresponding to the original. Additionally, it is necessary for the scanner and printing heads to be "locked" to each other as they traverse the original and receiving members, respectively. That is, they must traverse at exactly the same speed and in identical sequence.

An original graphic representation is scanned by a scanner, or series of scanners, transversely thereof which generate an analog signal or signals, respectively, related to the density of the areas scanned and transmit this information to an analog to digital convertor. The digital signals from the convertor are stored in a manner such that signals from corresponding points in a series of regularly spaced transverse bands across the original are simultaneously accessible for transmittal to a control unit controlling a corresponding number of coating heads to permit printing of the reproduction as a series of simultaneously printed transverse bands. The preferred storage medium for this purpose is a multiple channel magnetic tape.

The control unit has a tape reader which is connected to a load register for transferring the stored digital signals to a memory unit in bytes of several bits corresponding in number to the number of transverse bands to be printed at a time on a receiving member. Through the logic circuit of the present invention the signals are then unloaded in the same bit size bytes and transmitted through amplifiers to the coating mechanism.

The receiving member upon which the reproduction is printed may be mounted upon a rotating cylinder and the drop generators are moved axially of the cylinder by a stepping motor one line spacing for each revolution of the cylinder. Thus, not only is the necessity of traversing the entire width of the web with the coating mechanism obviated and the scanning operation not limited to one synchronized with the coating operation, but the necessity of modifying the trajectory of the coating material to compensate for relative transverse movement between the coating heads and the web is eliminated.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows, somewhat schematically, component for practicing the present invention;

FIG. 2 is a cross-sectional view through a typical ink drop generator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As seen in FIG. 1, the principal component of the present invention include a scanner 10, an analog to digital convertor 20, a tape reader 30, a load register 31, a memory 32, an unload register 34, a series of drop generators 35, eight being shown, a rotatable cylinder 36. The scanner 10 is shown for purposes of illustration as including a carriage 11 supported for scanning movement in the X and Y directions by motors 12 and 15 having conventional drive connections and controlled by unit 19. The original representation to be scanned and analyzed is indicated generally at 16 and it may take a variety of different forms, such as a positive or negative photographic film, or, for example, one of a set of color separations. The image on the original is a gradation of tonal densities, which may, for example, appear as portions of greater or lesser optical density, and a light source 17 is focused into a scanning light beam of predetermined small cross-sectional area through the image toward a photosensitive pick up 18. A suitable construction of this type is disclosed in U. S. Pat. No. 3,307,020 entitled HIGH INFORMATION DENSITY DATA RECORD AND READOUT DEVICE, and has the capability of producing a scanned spot of light or other radiant energy having a diameter on the order of 1 micron.

Regardless of the specific manner in which the surface of the original 16 is scanned, substantially the entire surface there of is scanned and an analog signal proportional to the intensity of the scanned area, that is light or dark in the case of a black and white representation, or, in the case of a color representation, the color of the scanned area, is generated and transmitted to the analog to digital convertor 20. Convertor 20 then converts the analog signal to a series of digital signals for transmittal to the format unit 21 over line 22. As described in detail below, the digital signals are recorded in parallel by tape recorder 23 in a parallel as a series of signals corresponding in number to the number of drop generators and these signals are thereafter retrieved for controlling the drop generators 35. Although eight drop generators and parallel signals are used for purposes of illustration, it will be apparent that the exact number may be varied as desired.

Drop generators 35 are uniformly spaced and positioned opposite the cylinder 36, and a manifold 37 supplies coating material under pressure to each of the drop generators. Liquid coating will tend to be projected from each of the generators 35 as a series of discrete coating drops and a vibrator 38 (see FIG. 2) may be provided for each drop generator to insure uniformity of size an spacing of the drops. Each drop generator 35, as shown in FIG. 2, will typically include a coating inlet chamber 40 having an orifice 41 of small diameter associated therewith and through which a filament of coating material is ejected. There is a natural tendency for this filament to break down into small, discrete drops, as indicated at 42, and uniformity of size and spacing of these drops is caused by mean of the constant frequency vibrator 38. At the point where the filament breaks down into individual drops a charge ring 43 is positioned for selectively applying an electrostatic charge to the drops passing therethrough. Positioned downstream of the charge ring are electrodes 44 and 45 and a catcher 46.

If it is desired to print a dot of coating material at a particular point on the surface of the receiving member carried by the rotatable cylinder 36, the appropriate binary signal is transmitted to the charge ring so that the drop is uncharged as it passes through the charge ring and it may then pass, undeflected, through the electrostatic deflection field established by the electrodes 44 and 45 and impinge on the surface of a receiving member. On the other hand, if it is desired to prevent a particular drop from impinging on the receiving member, the charge rings receives a binary signal of appropriate state at the instant that that particular drop is passing therethrough, charging the drop and causing it to be subsequently deflected by the electrostatic deflecting field into the catcher 46.

Referring again to FIG. 1, it will be seen that a receiving member 47 is mounted on the rotatably cylinder 36 and any convenient means, such as a stepping motor 48 and associated equipment of conventional construction, may be provided for advancing the drop generators longitudinally of the cylinder. This advancement will be intermittent, so that each drop generator 35 tracks a series of parallel, circumferential lines about the cylinder 36, although it will be apparent that continuous movement could also be utilized to cause each nozzle to track a continuous helical path. In the preferred form of the invention, however, intermittent movement is effected by suitable shifting means, including the stepping motor 48. Additionally, while means is described for purposes of illustration for moving the generators 35 axially of the cylinder 36 it will be apparent that any mechanism for causing the appropriate relative movement between generators 35 and the receiving member 47 in two directions normal with respect to each other may be utilized, including means for moving the receiving member while the generators remain stationary.

In any event, it will be seen that the scanning unit scans the surface of the original 16 from one end to the other and transmits an analog signal proportional to the intensity of the scanned area to the analog to digital convertor 20, which in turn transmits the digital signals via unit 21 to the tape recorder 23. In this regard it should be noted that the scanner is not "locked" in with the operation of the printing means. That is, the scanning operation proceeds entirely independently of the printing operation and the only interconnection is through the circuitry herein described. The type of tape recorder and reader utilized employ eight channels corresponding in number to the number of drop generators 35, and the tape is thus capable of supplying information bytes of eight bits, with each of the bits in each byte being otherwise unrelated to each other and, in effect, controlling one of the drop generators. The tape reader includes an internal tape generated clock which provides a read frequency signal on line 58, and suitable controls are also incorporated in the unit for starting, stopping and advancing, all of these controls being conventional and well known in the art. The tape reader 30 is connected to unload information, a byte at a time, into a first or loading register 31, which in turn is connected to load information one byte at a time into a suitable memory 32, such as a typical core matrix memory.

In one embodiment of the invention the memory 32 is divided into two units, each capable of storing 2, 048 eight-bit bytes of information. The memory output is connected to an unloading register 34 which handles output information from the memory one byte at a time and is connected to pass this information on through amplifiers 50 (and other suitable pulse shaping circuits which are not shown for purposes of simplification) to the charging rings of the coating drop generators 35. For purposes of this invention, the surface of the receiving member can be considered to be divided in matrix fashion, with the individual, parallel circumferential or helical scan lines followed by the drop generators 35 defining one set of parallel matrix coordinate lines and the other coordinate lines being defined by a second set of lines perpendicular to and at the same spacing as the first set of lines. Additionally, different density levels, similar to half tone printing, may be obtained by utilizing a submatrix system of coordinates at each coordinate position in the matrix. Thus, as explained in detail in U.S. Pat. No. 3,604,846, each coordinate position in the matrix can be divided into a, for example, 3 .times. 3 submatrix containing nine coordinate positions so that density levels can be varied from white (no drops applied to the submatrix) to black (drops applied at all nine coordinate positions in the submatrix).

When a submatrix of coordinates is employed for obtaining different density levels, the input tape has the various densities recorded on it in piecewise serial fashion. For example, where a 3 .times. 3 submatrix is desired the tape must have three bits of information (corresponding to one submatrix column) serially recorded on one tape track. This is serially followed on the same track by three bits of information for the corresponding columns of all submatrices in the associated scan line. Serially following this are the three-bit sets for all second submatrix columns and then the three-bit-sets for all third submatrix columns. Thus each track of the input tape carries information to enable an associated drop generator to control placement of drops within three adjacent three-drop-sets as the drop generator makes three successive passes over the drop receiving member. Three passes of any drop generator 35 then correspond to one scan of light source 17.

The format program (FIG. 1 block 21) reads the digitized density signals from converter 20 and performs a table look-up to convert each density (in the 3 .times. 3 example) to a nine bit binary code; each bit position corresponding to a submatrix square. Thereafter the converted density values are formatted in piecewise serial form as above described.

After submatrix formatting has been accomplished, it is necessary to get the density data into a form suitable for simultaneous use by eight drop generators. This is most conveniently accomplished by carrying out an intermediate storage and retrieval operation. All the formatted density information representing the entire original image is serially stored in a form suitable for multiple access; preferably on an eight band data disk. Thereafter the eight bands are read out simultaneously to eight magnetic recording heads in recorder 23 and recorded on eight side-by-side tracks on one magnetic tape. This tape then is supplied to tape reader 30 for control of the drop generators.

To initiate operation of the buffer, closing of the manual start switch 51 will produce an output from OR gate 52 to set the running control flip-flop 53, thus producing a set output from this flip-flop which is connected to signal the tape reader 30 over line 54, and hence initiate reading of information from the tape. The output from flip-flop 53 also provides an input to a load control counter 55 to clear that counter and prepare it for a loading operation. With the counter cleared, its output line 56 is at a low logic level, and this results in a high level logic signal from the inverting amplifier 57 to the loan control AND gate 60. This enables the AND gate 60, and clock pulses over line 58 from the tape reader 30 are transmitted by AND gate 60 to the counter 55, and are subsequently accumulated in this counter as they occur, until the counter fills. The counter 55 has a capacity of one half of the memory 32. The output from AND gate 60 also is transmitted to the load register 31 as a transfer input signal, and further is connected to the set input of the memory load control flip-flop 61.

A load control AND gate 62 receives an enabling signal each time the load flip-flop 61 is set, and this AND gate has two additional inputs, one coming directly from the output of an oscillator 63, and the other coming from the output of a dividing flip-flop 64. Therefore, the AND gate 62 is enabled on every other output from the oscillator 63, provided the load flip-flop 61 is set. An output from AND gate 62 produces a load signal to the memory 32, and also produces a reset or clear signal to the load flip-flop 61, thus immediately inhibiting AND gate 62. This circuit therefore permits the loading, one byte at a time, of information from register 31 into memory 32. So long as the run control flip-flop 53 remains in its set condition, this sequence repeats and the tape unit unloads the position control information into the register 31, from whence the information is transferred into the memory 32. It will also be seen that the output from dividing flip-flop 64 is transmitted to an invertor 65 and thence, over line 66 and 67 to a frequency divider 68, a vibrator 38 in each drop generator 35, and a synchronous motor drive 69 for driving the cylinder 36 in synchronization with the rate of drop generation to insure positioning of the drops at the proper matrix or submatrix coordinate positions.

When the load counter 55 is full, a high level output on line 56 results in a low level output from the invertor 57, inhibiting the AND gate 60 and terminating the transfer pulses to register 31. Further, line 56 is connected through a delay circuit 72 to the clear or reset input of flip-flop 53, thus removing the run signal from line 54 and stopping the tape unit. The output from the delay circuit also is transmitted over line 73 to the set input of a further control flip-flop 75 which indicates that the buffer is ready for a printing operation.

The output of flip-flop 75, the manually operated switch 76, and an output upon startup from encoder 77 in response to the sensing of a 30 fiducial mark 78 act as inputs to an AND gate 79. Therefore, to initiate the first printing operation switch 76 is closed and, as soon as fiducial mark 78 passes encoder 77, AND gate 79 is enabled to provide a set signal to the stop control flip-flop 81. If at any time it is desired to stop the printing operation, the manually operated stop switch 82 can be operated to provide clear or reset signals to flip-flops 75 and 81. The set output of flip-flop 81 provides an enabling circuit to a print control AND gate 83. The second input to AND gate 83 is from a revolution counter 84 which counts pulses corresponding to the rotational passage at circumferentially extending matrix positions beneath the drop generators 35 and generates an output to AND gate 83 when a number of such positions corresponding to the total circumference of the cylinder have passed. When this signal is received, the resulting output from AND gate 83 provides a set input to the print control flip-flop 86, and also provides a signal over line 87 to the OR gate 52, to again set the run control flip-flop 53, since it is now possible to commence a loading operation from the tape reader, with the printer beginning to use information from the memory 32.

It should be understood that on a starting, a further loading operation may begin after the load control 55 has terminated loading of the first 2, 048 bytes and the printing cycle has begun. This is due to the fact that the memory actually has twice this capacity. One half can be fully loaded at the start, then unloading will proceed from that half of the memory while loading can similarly occur in the other half of the memory with the information being transferred internally from input to output of the memory. AND gate 97 receives inputs from the oscillator 63, the dividing flip-flop 64 and the print flip-flop 86. However, the input from dividing flip-flop 64 is received through an inverter 65 and therefore the pulses on which AND gate 97 is enabled are the opposite pulses from those on which AND gate 62 is enabled. In this manner the loading and unloading of the memory is interlaced.

Unloading from the memory into register 34 will continue as the register is available to receive additional bytes of information, and each transfer of one byte will add, via line 99, another count into the unload or frame counter 100, which has a capacity of 2,048. When this counter fills, it produces an output on line 101 to the clear or reset input of print control flip-flop 86, resulting in an inhibiting signal to the AND gate 97 and thereby preventing further transfer of pulses to the amplifiers 50 and memory 32 and unload register 34 until a signal from revolution counter 84 indicates that a number of axially extending matrix positions have passed equivalent to one complete revolution of cylinder 36. This will cause AND gate 83 to set the print flip-flop 86 and begin operation on the next scan over the receiving member. Flip-flop 86 also produces an output signal to the clear input of counter 100 to reset this counter for further counting operations. This assures that each printing operation begins in a new scan at the same circumferential location, and assures proper alignment of successive "strings" of dots produced by successive scans of the receiving member past the drop projector. Centering of each dot within its assigned matrix or submatrix cell is accomplished by driving stimulators 38 in synchronism with the above described memory unloading operation. Also, the rotating drum 36 could be replaced by other means for repeatedly moving the receiving member past the drop generators.

It will thus be seen that by means of the present invention a digital reproduction of a graphic representation may be accomplished without the necessity of traversing the entire surface of the receiving member with any one drop projecting mans, without operating the scanner and printing unit simultaneously, and without compensating for transverse movement between the drop generators and the receiving member, and that unique circuitry is provided for accomplishing these results. Furthermore, it will be seen that this invention may be extended to multiple color reproduction by merely duplicating the disclosed apparatus to create a separate channel for each color.

While the method and forms of apparatus herein describe constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

Claims

1. Apparatus of the type described comprising: a. means for continuous line-by-line scanning of a graphic representation and transmitting an analog signal related to the density of the area scanned, b. means for converting said analog signals to digital signals, c. means for storing said digital signals serially line by line in sections comprising equal numbers of lines of graphic information, d. means for parallel retrieval from said sections of the graphic information stored therein, said retrieval information being in the form of bytes comprising bits from corresponding locations within said sections whereby the bits in one byte represent binary graphic information at corresponding points in non adjacent evenly spaced lines across a reproduction of aid graphic representation, and corresponding bits in successive bytes represent binary graphic information at adjacent points along one of said lines across said reproduction, e. a plurality of drop generators corresponding in number to the number of bits in each of said bytes, f. a receiving member, g. means for moving said drop generators relative to said receiving member in a first direction at a rate corresponding to the retrieval rate of said bytes and in a second direction at a slower rate corresponding to the rate of retrieval of entire lines of graphic information, and h. means for projecting streams of drops simultaneously from each of said drop generators toward said receiving member and selectively catching drops from each of said streams in response to the character of the bits in each of said retrieved bytes whereby said drop generators print progressively widening bands which meet to define a composite reproduction

2. The apparatus of claim 1 further comprising: a. an oscillator generating signals at a uniform frequency, b. means for controlling the frequency of drop projection from said drop generator in response to said oscillator signals, and c. means for controlling the retrieval of signals from said storing means

3. The apparatus of claim 1 wherein: a. said storing means comprises a multi-channel tape recorder, and

4. The apparatus of claim 3 further comprising: a. means for regulating the frequency of drop projection from said drop generators in synchronism with the retrieval of said bytes of graphic

5. A method of reproducing a graphic representation comprising the steps of: a. scanning a master image in two coordinate directions and creating a matrix of information bits representative of image density and coordinate location for every resolution element within said image, b. storing said matrix of information bits for retrieval in a plurality of parallel information streams; the simultaneous output of said parallel information streams representing binary image information at equally spaced observation points along a line parallel to one of said coordinate directions and the serial output of each of said streams corresponding to movement of said observation point in a direction parallel to the other of said coordinate directions followed by incremental lateral shifting and continued parallel movement, c simultaneously generating said plurality of parallel information steams in response to outputs from a master clock, b. generating a plurality of streams of drops of coating material of uniform size and spacing in synchronism with the generation streams, e. repeatedly moving a receiving member past said stream of drops at a speed related to the drop generation rate and in a direction corresponding to the second of said coordinate directions, f. moving the receiving member in a direction corresponding to the first of said coordinate directions and with progressive movement corresponding to aforesaid incremental lateral shifting of said information streams, g. applying the serial output of each of said information streams to charge control apparatus for a different one of said streams stream and for each position within each of said information streams charging a drop to a level corresponding to the binary state of the information stream, h. deflecting and catching all drops carrying a charge corresponding to one binary information state and printing with all drops carrying a charge corresponding to the other binary information state thereby creating a set of parallel printed image bands of progressively increasing width, and l. continuing the progressive movement of the receiving member in said first direction until said parallel printed image bands become contiguous

6. A method according to claim 5 wherein: a. said matrix of information comprises a submatrix of bit positions for each of said resolutions elements; and b. the number of bits within said submatrix correspond to the density level

7. A method according to claim 5 wherein: a. said progressive movement of the receiving member in the first direction is performed in incremental steps in timed relation with the incremental shifting of the information streams.