Image Construction System With Arcuately Scanning Drop Generators

Abstract

An image to be reproduced is repetitively optically scanned along successive arcuate lines and the density variations are converted to transmittable digital signals. The scanner may have several scanning heads and appropriate filters to differentiate between colors. A printer has a corresponding number of liquid drop generators scanning a receiving sheet in the same fashion. Individual drops are projected toward the sheet predestined for a certain coordinate location; the signals are received and buffered into the printer causing some drops to switch from their normal trajectory and be removed from the system, thus reproducing the image in dot-by-dot fashion.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This invention relates to the production, or reproduction, of images by precise placement of small liquid drops of a marking substance such as ink. It has been proposed to produce traces, or in some cases images, using one or more drop generators in which the individual drops are switched, so as to deposit, or not to deposit on a moving web or paper sheet. Typical of such prior art is the U.S. Pat. to Sweet and Cumming, No. 3,373,437. The liquid drops are generated at relatively high frequencies, in the order of 40 to 120 kHz., and assuming for purposes of explanation that the dots from drop deposits are about 5 mils in diameter, and that it is desired not to deposit one drop upon another, although some overlapping might be desired, such a system inherently includes a requirement for relatively high velocity relative motion between the drop-generating means and the paper or other receiving member. In some applications wherein it is desired to reproduce a relatively small number of copies it is impractical to provide high-speed reciprocating drives. An alternative to such drives is a cylindrical printing arrangement as shown in Kazan U.S. Pat. No. 3,287,734. However, mounting a receiving member on a cylinder is tedious and moreover impractical in operations wherein it may be desired to print on a moving web.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with the present invention, a printer using the jet drop technique is provided for both single and multicolor printing, wherein the relative motion between the drop generator equipment and the receiving member or web is at a relatively low speed, and the drop generator equipment is scanned at a much higher speed repetitively over the receiving member. In a preferred embodiment a rotating disc carries a plurality of drop generators and rotates over the area of the web on which an image is to be produced, causing the generators to scan repetitively in an arc over such image area. The motion of the receiving member causes the successive scans to be spaced slightly apart for example by a distance equal to the desired center-to-center spacing of the dots. Furthermore, an encoder or equivalent pulse-generating device may be coupled to the rotating scanning mechanism to generate gating pulses at a frequency corresponding to the desired center-to-center dot spacing thereby providing a synchronized control for precise side-by-side placement of the dots. The rotating device carrying the drop generators, the encoder, and the mechanism for advancing the receiving web, are all driven in synchronism, preferably from a common drive unit, to assure the exact correlation of these various devices, and thus to assure that each drop can be precisely located in a coordinate system, where the successively arcuate scan lines form one half of such system, and the output of the encoder provides the other half of the coordinate system. Each drop directed along a trajectory toward the web is destined for a certain coordinate location, and depending upon the intelligence controlling the drop-switching units, the individual drops will be removed from the trajectory, and prevented from depositing or will be permitted to deposit in the predestined location.

By employing a plurality of drop generators which scan in succession over the receiving member, it is possible to deposit drops of different colors, thus producing a multicolor print.

The input intelligence for such a printer can be provided by an optical scanner functioning in the same manner, and employing a corresponding number of optical scanning devices which are scanned in arcuate fashion over the original of an image to be reproduced. The original is moved in synchronized relation with respect to the scanning motion, and a scanner encoder is keyed or otherwise driven by the same drive unit which produces the scanning motion, and is connected to gate the outputs of the optical scanners, thereby producing intelligence which can be transmitted over presently available communications equipment. In general, the intelligence in a multicolor system includes digital switching information for each of the optical scanners, which may involve four colors, together with control signals which gate the system and distinguish between the scans for four different colors.

Accordingly, an object of this invention is to provide a novel image-producing device responsive to digital input information and creating the image from successive liquid drops which are deposited in coordinate fashion from a drop generator which is repetitively scanned over a moving web or equivalent receiving member; to provide a novel scanning and pulse intelligence-producing device for creating an input to such a printer, and to provide an image reproduction system employing the printer and scanner device, which is capable of use with presently available communications equipment.

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 view showing the general arrangement of a scanning device provided according to the invention;

FIG. 2 is an illustration of the coordinate scanning technique employed by the scanning device and by the printer;

FIG. 3 is a block diagram showing the pulse intelligence equipment associated with the scanning device, and indicating the connections to one of a plurality of optical scanners;

FIG. 4 is a similar block diagram illustrating the intelligence-receiving and handling equipment for the printer, and showing diagrammatically the connections from this equipment to one drop generator;

FIG. 5 is a diagram showing the general arrangement of a multicolor scanning printer provided in accordance with the invention;

FIG. 6 is an enlarged detail view, partly broken away and shown in section, illustrating details of one drop generator;

FIG. 7 is a further enlarged sectional detail, showing details of the switching head of a drop generator;

FIG. 8 is a sectional view illustrating the rotating liquid and electrical connections employed on the rotating shaft of the printer shown in FIG. 5; and

FIG. 9 is a slightly enlarged sectional view, taken on line 9-9 in FIG. 8, showing the arrangement of liquid passages in the shaft.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to the drawings, and particularly to FIGS. 1 and 3, an original copy or print 10, having an image of pictorial or text matter to be reproduced, is supported on a transversely movable base 12 for scanning by the optical scanner. This scanner includes a disc 15 or equivalent rotating support which is rotated at a predetermined constant speed by a drive shaft 16 from a drive unit 18 which may include a motor and appropriate gear reduction and speed control device. The drive unit also has an output indicated schematically at 19 to the base 12 for advancing the base at a predetermined relatively slow rate with respect to the rotating scanning disc 15. This causes the optical scanners 20a, 20b, 20c and 20d to scan in sequence over arcuate paths across the original 10. As shown in FIG. 2 these paths are represented by the arcuate lines 21, with the scanning viewed from above and the motion of the optical scanning unit (or the printing units shown in FIG. 5) progressing from left to right. Motion of the copy from top to bottom produces the spacing of successive arcuate scans, and this spacing is controlled by the drive arrangement whereby through the drive 19 the base 12 is advanced by the amount between successive scan centers during the interval between commencement of scans by successive scanning units.

The drive 18 also is connected to a scanner encoder 24 which is constructed to produce pulses at regular intervals during the scanning motion. A typical encoder might be a "light chopper" employing a disc or drum with slits or opaque marks which repetitively interrupts the path between a light source and a photocell. Other encoders such as a magnetic pickup head and a magnetic recording surface may likewise be employed. As shown in FIG. 2, the occurrence of the encoder pulses can be used to break the arcuate scans into a coordinate system, the vertical lines 25 representing the occurrence of successive encoder pulses, and thus a coordinate system is created wherein the occurrence of a given encoder pulse during a given arcuate scan represents a particular coordinate in the system. In the scanner shown in FIGS. 1 and 3, separate scanning units 20a--20d are employed, each responding to a different color, for example red, cyan, yellow and black. In order to provide time for blanking and control signals which also can be produced from the encoder, it is preferred that the angular extent of the arcuate scans be slightly less than 90.degree.. In a typical arrangement each scan will extend for approximately 88.degree., leaving 2.degree. of movement to accommodate control information.

Referring to FIG. 3, each of the scanning units includes a light source 30 which is focused by an optical system 31 projecting a small light spot on the copy 10. The reflection of this spot of light from the copy is directed through a further optical system 32, which directs the light into a beam splitter 35. Two separate beams of light pass from the beam splitter, one beam passing along the path indicated at 36 and through a suitable color filter 38, and another or reference beam 39 being directed through a neutral density filter 40.

Light from the color filter 38 is focused by an optical system 42, including an aperture or slit, into a pickup photomultiplier 44. Light from the neutral density filter 40 is similarly focused through an optical system, including an aperture, onto a second photomultiplier 46. The separate outputs from these photomultipliers are amplified by suitable amplifiers, indicated generally at 48, and the two signals are directed to a log ration amplifier 50. It should be understood that this arrangement is repeated for each of the scanning units, with the physical elements including the photomultipliers or equivalent transducers mounted as part of each scanning unit, and the electronics being mounted externally of the rotating system with suitable slip ring connections or the like providing the necessary electrical connections. In a multicolor system this arrangement is repeated for each of four colors, and in FIG. 3 the scanning electronics is shown in detail for one color, with the outputs of the corresponding electronics for the other three colors being indicated with a suitable legend.

Assuming that amplifier 50 provides an output corresponding to the scanning of the color "red" (magenta), this output is directed to a threshold logic circuit 52 which is constructed and arranged to provide an output only if the scanning unit output has a signal from the corresponding difference amplifier that exceeds a predetermined level. In other words, the scanning unit must "see" a certain intensity of red before there will be an output from the threshold logic circuit. The output of the logic circuit 52 is directed to one input of a NAND gate 55, and the other input to this gate circuit is from the scanner encoder 24, which serves to provide a regular sampling of the threshold logic output circuit, hence the output from the NAND gate, along the red signal line 56, will be a pulsed signal indicating presence or absence of a red dot in the print to be reproduced. Corresponding pulse signals appear on the lines 57, 58 and 59, corresponding to the presence or absence of dots of cyan, yellow, and black colors.

The outputs of the four sampling gates are connected into a blanking circuit 60 including a suitable control flip-flop and gating circuits which are keyed from the scanner encoder. As previously mentioned, between each arcuate scan and the gating pulses received from the encoder during this scan, there is a short period in which gating pulses are transmitted from the scanning encoder to control the gating of the scanner unit outputs. These signals cause only the appropriate output from that scanning unit next to scan the original to be transmitted over the transmission system, indicated generally at 62. The resulting signal is digital in nature, essentially a string of control pulses which are time based according to the scanning operation, and which depending upon available bandwidth can be transmitted over presently available systems such as telephone lines.

FIG. 4 shows in block form a suitable arrangement for the control of the printer. The receiver is indicated by the input arrow 65 which receives the pulse information from the transmitter 62, and directs this information to an input shift register 67. This register transfers the digital information into a buffer memory or storage unit 68. In general, the digital information corresponding to each scan is stored in the buffer memory with appropriate signals distinguishing that information from the information for other scans. This information is taken from the memory through an output shift register 70 as it is needed to control the printer, and it is transmitted through blanking control flip-flops and gate circuits, indicated generally at 72, to provide an output on one of the four control lines 73, 74, 75 and 76. Each of these control lines is connected to a suitable amplifier 78 (only one shown in FIG. 4) which in turn directs the pulses signal to the switching units of a jet drop projector unit which is indicated generally at 80.

A printing device of the type employing four such drop generators, designated 80a--80d, which are scanned in sequence over a web or other suitable receiving member, is shown in FIG. 5. The web 82 is driven through drive rollers 84 from the suitable drive means 85, in the direction indicated by the arrow. The web is thus moved over the locating table or support surface 87. The drop generators 80a--80d are supported on a disc or plate 90 which is in turn carried on a rotatable shaft 91 driven from the drive means 85. This same drive means, as shown schematically, also drives a printer encoder 95 which provides registering or control pulses for the system.

A detail of one of the drop generators 80a--80d and its mounting is shown in FIGS. 6 and 7. An orifice 100 is provided in a liquid ink supply tube 102 which is carried in an adjustable ball-type mounting 103. This mounting is in turn positioned within a correspondingly shaped socket 104 fastened to the disc 90. The switching controls include a charging electrode 105, and deflecting electrodes 107. The connection to the charging electrode is indicated at 110, the connection to the deflection electrodes is indicated at 112. The catcher unit 115 projects into the lower end of the unit, in close proximity to the path or trajectory of the drops issuing from the orifice 100. The stimulating transducer, which stimulates the drop generator to produce drops at the desired frequency, is indicated generally at 118, it being understood, as shown in FIG. 5, that there are preferably separate stimulators for each drop-generating unit.

The liquid ink supply is conducted to the individual drop generators through flexible hoses 120a--120d which extend through separate passages 122a--122d (FIGS. 8 and 9) inside the rotating shaft 91 into respective ones of the rotary connectors 125a--125d. These four connectors receive different color inks from the respective reservoirs 127a--127d, which are supplied through pumps 128. Similarly, each of the catcher units 115 is connected into a common return tube 130 which in turn extends through a passage 132 in the shaft to the rotary joint 135 providing an exit for the liquid collected from the respective catcher units. A collector tank 137 and vacuum pump 138 provide continuous suction through the collector system. The slip rings 140 and corresponding brushes 142 provide separate electrical connectors from the amplifiers 78 (FIG. 4) for the respective charging electrodes, power supply for the deflecting electrodes, and power supply for the high frequency stimulators.

With reference to FIG. 6, it will be noted that the longitudinal axes of each of the drop generator units is inclined in a rearward direction with respect to the predominant direction of relative movement between the receiving member or web 82 and the drop generator. In this case, since the rotary scanning movement of the drop generators is at a considerably higher speed than the advancing movement of the web, the inclination of the drop generator is provided at an angle with respect to the plane of the disc 90 such that the drops are projected with a horizontal velocity component which effectively cancels the velocity contribution produced by the rotation of disc 90. As a result thereof the drops descend in a nearly vertical trajectory.

The encoder 95 provides a source of control pulses which serve to step the signals from the memory through the output shift register 70 and gate these switching signals to the drop generators. The encoder preferably also controls the stimulating frequency of the stimulating devices 118, by controlling their driving amplifier 144 (FIG. 4) at a frequency which corresponds to the scanning rate of each drop generator across the web 82. In other words, the frequency resulting from control by the encoder will produce drops spaced apart such that they are deposited in adjoining positions along an arcuate scan line on the web 82, and if drops are permitted to deposit successively, a solid generally arcuate line may be formed across the web. Forward motion of the web 82 is sufficient, and is correlated through the common drive means 85, to cause successive scans of the drop generators 80a--80d to fall along arcuate scan lines spaced apart by a selected distance. For example, if it is desired that the dots formed by deposited drops should join, or slightly overlap, then the forward motion of the web 82 between the beginnings of the succeeding scans will equal the desired center-to-center spacing of the dots. The successive control pulses from the encoder will provide timed gating signals according to the center-to-center spacing desired for successive drops from the drop generators in a single scan. Thus the digital intelligence to the charging electrodes 105 is gated to assure precise placement of the liquid drops along the scan lines at predetermined coordinate positions on the web 82.

While the method herein described, and the form of apparatus for carrying this method into effect, constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to this precise method and form of apparatus, and that changes may be made in either without departing from the scope of the invention.

Claims

I claim:

1. The method of creating a pattern by selective spatial and positional control over a large number of small liquid drops, comprising the steps of:

a. first scanning a master representation of the pattern to be reproduced over successive arcuate paths;

b. creating digital control signals from the scanning operation;

c. generating a liquid jet along a predetermined trajectory;

d. stimulating said jet from a source of vibration responsive to said scanning to cause the jet to break into individual drops having essentially the same size and velocity characteristics such that successive drops will deposit on the member in adjacent positions whereby a continued deposit of drops will produce an essentially continuous arcuate line for each scan;

e. scanning the jet repetitively in successive arcuate paths over a drop receiving member at a constant speed, the paths being spaced such that successive lines or parts thereof formed on the receiving member adjoin in the same manner as successively deposited drops; and

f. switching selected ones of said drops from their respective trajectories in response to the signals from step b and removing such drops from the system thus causing the remaining drops to form a pattern of predetermined configuration on the receiving member.

2. Apparatus for producing a graphic representation from digital output information, comprising:

means for supporting a receiving member;

a plurality of marking units arranged to place individual dots of a different color on the receiving member;

scanning means carrying said marking units and causing them to scan sequentially over said supporting means in a curved path and a coordinated drive means causing relative movement between the receiving member and said scanning means whereby said marking units scan the receiving member in succession over arcuate paths of predetermined spacing;

a control for said marking units including synchronizing means correlated to said scanning means and connected to switch each said marking unit according to input intelligence signals and place dots at precise positions on the receiving member;

said control including blanking means for directing the intelligence signals in succession to the marking units as each unit scans across the receiving member;

said control including an encoder means also coordinated with said drive means and arranged to generate gating signals according to the center-to-center spacing of dots on the receiving member; and

gating means connected to control said marking units under the combined influence of gating signals and intelligence input signals.

3. Apparatus according to claim 2, wherein said marking units each include means for generating a stream of spaced liquid drops toward the receiving member at a rate corresponding to the scanning velocity, and switching means responsive to the control signals to deflect certain of the drops from their normal trajectory according to the control signals whereby drops are deposited on the receiving member according to a coordinate intelligence pattern.

4. Apparatus for digitally reproducing copies of an image comprising:

means for supporting a representation of the image to be reproduced;

first scanning means arranged to scan the image on said supporting means over a plurality of adjacent arcuate scan lines;

signal-generating means coordinated with and driven by said first scanning means to produce an output of a series of pulse information signals representing in digital form the location of individual dots comprising the output of the scanning means;

said signal-generating means including a first encoder driven with said first scanning means and producing gating pulses time based according to the desired center-to-center spacing of the dots in the image;

said first encoder having its gating pulse output connected to control the output from said signal-generating means;

means for supporting receiving member such as a copy sheet;

a marking unit including means for generating discrete marking drops at a predetermined rate;

second means for scanning said marking unit over a receiving member on said supporting means along a plurality of arcuate scan lines corresponding to the scan of said first scanning means and at a rate corresponding to the drop generation rate of said marking unit;

said second scanning means including a rotatable member carrying said marking unit and arranged to scan said marking unit repetitively over the receiving member;

drive means connected to rotate said rotatable member and to advance said supporting member in coordinated fashion whereby said marking unit follows successive arcuate scans over the receiving member spaced apart by the center-to-center drop spacing desired in the resultant image;

drop control means connected to said marking unit and constructed and arranged to cause certain of the individual drops to deposit on the receiving member and other drops to be intercepted after leaving said generating means;

control circuits coordinated with said second scanning means and receiving said information signals from said signal generating means, said control circuits having an operating connection to said drop control means for causing deposit of individual drops on the copy sheet in accordance with the signals to reproduce the image in dot matrix form on the receiving member;

a second encoder operated from said drive means to generate positional time based gating signals for locating drop placement from said marking unit during its scanning movement; and

a gating output from said second encoder to said control circuits for controlling the timing of information signals to said marking unit.

5. 5. Apparatus as defined in claim 4, wherein there are a plurality of first scanning means each responsive to a different color, and a corresponding number of marking units each generating drops of a corresponding different color, said second scanning means being constructed and arranged to scan said marking units sequentially and repetitively along arcuate scans across the receiving member to reproduce a multicolor image in dot matrix form.

6. A jet drop recorder comprising:

a modulatable drop generator;

said drop generator being modulatable by generating a stream of drops of equal size at a constant frequency and selectively removing drops from the stream in accordance with a predetermined program;

support means for supporting a planar receiving member in the field of coverage of the drop generator;

rotating means for producing rotary scan motion of the drop generator around a stationary axis in a plane parallel to the plane of a receiving member on said support means;

translating means producing linear motion of a receiving member on said support means past an arcuate section of the rotary motion of the drop generator thereby enabling drop deposition on the receiving member along successive spaced arcuate lines;

a coordinated drive system connected to operate said rotating means at a predetermined constant speed and to stimulate said drop generator at a corresponding frequency to produce adjoining drop deposits on the receiving member along the scan direction and also connected to said translating means for spacing successive scans such that drop deposits in successive scans can adjoin; and

an encoder operated from said drive system to generate positional time based gating signals for stimulating said drop generator to locate the drop deposits in adjoining relation along each arcuate scan line.

7. Apparatus for producing a graphic representation from digital input information, comprising:

means for supporting a receiving member;

a marking unit including means for generating a stream of spaced liquid drops toward the receiving member at a rate corresponding to movement of said scanning means to place individual dots in adjoining positions on the receiving member;

scanning means carrying said marking unit to scan over said supporting means in a curved path;

advancing means causing relative movement between the receiving member and said scanning means in a direction transverse to the curved scan path whereby said marking unit scans the receiving member in spaced arcuate paths;

drive means operating said scanning means and said advancing means at correlated speeds to assure proper spacing of successive scan paths over the receiving member;

switching means in said marking unit to deflect certain of the drops from the stream according to the input signals;

a control for said marking unit including synchronizing means correlated to said scanning means and connected to switch said marking unit according to input intelligence signals and place dots at precise positions on the receiving member;

said control including an encoder means synchronized with said drive means and arranged to generate gating signals according to the center-to-center spacing of dots in the arcuate paths on the receiving member; and

gating means connected to control said switching means under the combined influence of gating signals and intelligence input signals.

8. Apparatus according to claim 7, wherein said advancing means includes a movable carriage providing the supporting means for the receiving member, said scanning means including a rotatable member mounting said marking unit and arranged to rotate in a fixed circle over the path of movement of said carriage across the receiving member, and said drive means is constructed and arranged to rotate said rotatable member at a fixed speed and to advance said carriage at a predetermined lower speed causing said marking unit to make closely spaced successive arcuate scans across the receiving member.

9. Apparatus according to claim 7, including a plurality of marking units each arranged to place dots of a different color on the receiving member;

said scanning means being arranged to scan said marking units sequentially over said supporting means; and

said control including blanking means for directing the intelligence signals in succession to the marking units as each unit scans across the receiving member.