JP2000071488A - Linear translating system utilizing dither method for improving image quality of target image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To induce an irregular pattern of white noise artificially by controlling linear movement of a print head at a speed synchronized with rotation of a vacuum image drum and interrupting driving of a motor with a random lag when the vacuum image drum rotates. SOLUTION: A vacuum image drum 300 is related operationally with an encoder 344 and a rotation synchronizing pulse signal is generated for every revolution of the vacuum image drum 300 and delivered to a stepper motor controller 166. The stepper motor controller 166 drives a stepper motor 162 to move a print head with a constant uniform pulse train along the surface of the vacuum image drum 300 at a speed synchronized with the rotational speed thereof. When the vacuum image drum 300 rotates subsequently, the stepper motor 162 is stopped by interrupting the uniform pulse train causing a random lag in the linear movement of the print head during rotation of the vacuum image drum 300.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processor, and more particularly, to a laser thermal printer having a linear translation system using a dither method to improve the quality of a target image.

[0002]

BACKGROUND OF THE INVENTION Prepress color proofing is a high cost and time required to begin high speed, high volume printing to actually make a printing plate and produce a single sample of the target image. This is a procedure that is used in the printing industry to create a representative image of a printed matter without applying any additional processing. The target image requires some modifications and is re-manufactured several times to meet customer needs, resulting in a loss of many benefits. Using prepress color proofing saves time and money.

[0003] One such commercially available image processing device is the image processing device having halftone color proofing capability described in EP 528,441. The image processing apparatus is arranged to transfer a dye from a sheet of the dye donor material to a thermal print medium by applying a sufficient amount of thermal energy to the dye donor material, and to form a target image on the thermal print medium. ing. The image processing apparatus generally includes a material supply assembly or carousel, a lathe bed scanning subsystem (including a race bed scanning frame, a translation drive, a translation stage member, a printhead and a vacuum imaging drum), a thermal print medium and It comprises a dye donor material outlet drive mechanism.

[0004] The operation of the above image processing apparatus comprises measuring the length of a thermal print media (in the form of a roll) from a material assembly or carousel. The thermal print media is then measured and cut into sheets of the required length, transported to a vacuum imaging drum, aligned, wrapped around the vacuum imaging drum, and fixed on the drum.
The length of the dye donor material (in the form of a roll) is then also measured from the material supply assembly or carousel, measured and cut into sheets of the required length. It is then conveyed to the vacuum imaging drum and wrapped around the imaging drum so as to overlap the desired alignment with the thermal print media (already secured to the vacuum imaging drum).

After the dye donor material has been secured to the outer periphery of the vacuum drum, the operating subsystem or writing engine performs the operating function. This is accomplished by holding the thermal print media and dye donor material on a rotating vacuum imaging drum while rotating past a printhead that is exposed to the thermal print media. The translational motion then traverses the printhead and the translation stage component that are axially along the vacuum imaging drum to match the movement of the rotating vacuum imaging drum. These movements combine to create the desired image on the thermal print media.

After the target image has been written on the thermal print media, the dye donor material is then removed from the vacuum imaging drum. This is done without dispersing the underlying thermal print media. The dye donor material is then transported from the image processor by a dye donor material exit drive. Additional dye donor material is sequentially overlaid on the thermal print media on the vacuum imaging drum and then imaged on the thermal print media as described above until the intended image is completed. The completed image on the thermal print media is then removed from the vacuum imaging drum and conveyed by a receiver sheet material exit drive to an external holding tray located on the image processor.

The material supply assembly consists of a carousel assembly mounted for rotation about a horizontal axis on bearings at the upper end of a vertical quaternary body. The carousel in this case consists of a vertical circular plane with six (but not limited to six) material quaternary spindles. The support spindle has one roll of thermal print media and four rolls of dye donor material.
It is arranged to carry three rolls and provides the four main colors used in the writing process to form the target image. There is another roll (if desired) for a special color dye donor material or as a spare. Each spindle has a feeder for removing the thermal print media or dye donor material from the spindle so as to be cut into sheets. The carousel rotates about an axis to the desired position, so that the thermal print media or dye donor material (in the form of a roll) is removed, measured, cut into the required length of sheet, and then evacuated. It is carried to the image drum.

[0008] A scanning subsystem or writing engine of the racebed scanning type provides positioning and motion control of the vacuum imaging drum to facilitate placement, and mechanical loading and unloading of the vacuum imaging drum with thermal print media and dye donor material. Consists of a mechanism for providing an actuator. The scanning subsystem or writing engine provides a scanning function for holding the thermal print media and dye donor material on the rotating vacuum imaging drum, said scanning function generating a timing signal to the data path electronics as a clock signal, while a translation function. The drive traverses a translation stage member and a printhead axially along the vacuum imaging drum to accommodate movement of the vacuum imaging drum rotating past the printhead. This is done with maintained positional accuracy and allows for precise control of the placement of each pixel in order to produce the target image on the thermal print media.

The race bed scanning frame is provided with a structure for supporting the vacuum imaging drum and its rotational drive. A translation drive having a translation stage member and a write head comprises:
Supported by two translational bearing rods that are substantially straight along the longitudinal axis and that are parallel to the vacuum imaging drum and the lead screw, are positioned parallel to the vacuum imaging drum and the lead screw. As a result, along the vacuum imaging drum and the lead screw, they form surfaces internally and are parallel to each other. The translation bearing rod is supported by the outer wall of the racebed scanning subsystem or racebed scan frame of the writing engine. The translation bearing rods are positioned and aligned between the bearing rods to enable low friction motion of the translation stage member and translation drive. The translation bearing rod is rigid enough for this application and does not sag or deform between the mounting locations at each end. The translation bearing rod is arranged to be as parallel as possible to the axis of the vacuum imaging drum. The front translational bearing rod is positioned to position the printhead axis exactly on the axis of the vacuum imaging drum with the axis of the printhead positioned vertically, vertically, and horizontally with the axis of the vacuum imaging drum. The translation stage member front bearings are arranged to form an inverted "V" shape and provide only restraint to the translation stage member. A translation stage member having a printhead mounted on the translation stage member is held in a position that is only its own weight. The rear translation bearing rod positions the translation stage member with respect to rotation of the translation stage member about the front translation bearing rod axis. This means
During the writing process, which causes unacceptable artifacts in the target image, without activating, rattling or otherwise constraining the translational drive or translation stage members which imparts undesirable vibration or jitter to the printhead. Done. This is achieved by a rear bearing which only engages with the exact opposite rear translation bearing of the translation bearing on a line perpendicular to the line connecting the center line of the front and rear translation bearing rods.

The translation drive allows relative movement of the printhead by synchronizing it with the movement of the printhead and stage assembly so that the required movement is smooth and even throughout each rotation of the drum. The clock signal generated by the drum encoder provides the necessary reference signal that accurately indicates the position of the drum. This coordinated movement results in the printhead tracking the helical pattern around the drum circumference. The movement described above is achieved by a DC servomotor and an encoder that rotates a lead screw parallel to the axis of the vacuum imaging drum. The print head is positioned on the translation stage member in a "V" shaped groove formed in the translation stage member and is in precise positional relationship to the bearing for the front translation stage member supported by the front and rear translation bearing rods. The translation bearing rod is positioned parallel to the vacuum imaging drum so that the vacuum imaging drum automatically adopts the preferred orientation with respect to the vacuum imaging drum. The printhead is selectively positionable with respect to the translation stage member and is thus positioned with respect to the vacuum imaging drum surface. By adjusting the distance between the printhead and the surface of the vacuum imaging drum as well as the angular position of the printhead about an axis using adjustment screws, a precision adjustment means for the printhead is provided. The tension spring applies a load to the two adjusting means. The translation stage member and the printhead are mounted on a rotatable lead screw (with a threaded shaft) by a drive nut and coupling. The coupling is arranged to accommodate the misalignment of the drive nut and the lead screw, so that only rotational and parallel forces are applied to the translation stage member by the lead screw and the drive nut. The lead screw is between the two sides of the racebed scanning subsystem or racebed scan frame of the writing engine and is supported by deep groove radial bearings. At the drive end, the lead screw is continuous through a deep groove radial bearing, through a pair of spring retainers separated and loaded by a compression spring to provide an axial load, to the DC servo drive motor and encoder. The DC serve drive motor causes rotation of the lead screw that moves the translation stage member and printhead along the threaded shaft as the lead screw rotates. The lateral movement of the printhead is controlled by changing the direction of rotation of the DC serve drive motor and thus the lead screw.

[0011] The printhead includes a plurality of laser diodes coupled to the printhead by fiber optic cables that supply energy to selected areas of the thermal print media with information signals. The printhead of the image processing apparatus includes a plurality of optical fibers coupled at one end to a laser diode and coupled at another end to an array of optical fibers in the printhead. The printhead is movable with respect to the longitudinal axis of the image drum. As the radiation travels from the laser diode by the fiber optics to the printhead, and thus into the dye donor material, it is converted to thermal energy in the dye donor material and the dye is transferred to the thermal print media.

The vacuum imaging drum is cylindrical with a hollow interior; the vacuum imaging drum supports the thermal print media and the dye donor material as the vacuum imaging drum rotates, and a vacuum to maintain its position. It further has a plurality of holes extending through the housing to allow a vacuum to be applied from inside the imaging drum. The end of the vacuum imaging drum is closed by a cylindrical end plate. The cylindrical end plates are each provided with a centrally located spindle that extends outwardly through a support bearing and is supported by a race bed scanning frame. The drive end spindle extends through a support bearing and is stepped down to receive a DC drive motor rotor held by a nut. The dc motor starter is fixedly held by the race bed scanning frame member and encircles the armature to form a reversible, variable speed dc drive motor for the vacuum imaging drum. At the end of the spindle, an encoder is mounted to send a timing signal to the image processing device. The opposing spindle provides a central vacuum opening and mates with a vacuum fitting having an external flange that is rigidly attached to the racebed scanning frame. The vacuum fitting has an extension extending therethrough, but is located close to the vacuum spindle, thus creating a small clearance. With the above arrangement, a slight vacuum leak occurs between the outside diameter of the vacuum fitting and the inside diameter of the opening of the vacuum spindle. This ensures that there is no contact between the vacuum fitting and the vacuum imaging drum that imparts uneven movement or jitter to the vacuum imaging drum during rotation.

The opposite end of the vacuum fitting is 60-70 cfm
Connected to a high-volume vacuum blower capable of producing 50-60 inches of water (93.5-112.2 mm of mercury) at an air flow volume of 28.368-33.096 liters per second This applies a vacuum to the vacuum imaging drum to maintain the various internal vacuum levels of the vacuum imaging drum required during loading, scanning and removal of the thermal print media and dye donor material to produce the desired image . Without the media loaded in the vacuum imaging drum, the internal vacuum level of the vacuum imaging drum would be approximately 254-481 mm (10-15 inches) water column
(18.7-28.05 mm of mercury). When the vacuum imaging drum is just loaded with the thermal print media, the internal vacuum level of the vacuum imaging drum is approximately 50 water columns.
8-635 mm (20-25 inches) (37.4 mercury
-46.75 mm), which is the level required when removing the dye donor material to prevent the thermal print media from migrating, otherwise color matching cannot be maintained. When both the thermal print media and the dye donor material are fully loaded into the vacuum imaging drum, the internal vacuum level of the vacuum imaging drum in this arrangement will be about 1270-water column.
1524 mm (50-60 inches) (93.5-
112.2 mm).

The outer surface of the vacuum imaging drum has an axially extending plane extending about 8 degrees around the circumference of the vacuum imaging drum. The vacuum imaging drum is vacuumed from one axially extending plane on the circumference of the vacuum imaging drum to the other axially extending plane, and from one inch from one end to a vacuum. About 25.4mm from the other end of the image drum
It also has a circumferential recess extending circumferentially to (1 inch). When mounted on a vacuum imaging drum, the thermal print media is mounted in a circumferential recess, and the circumferential recess is approximately 0.12 mm (0.004 mm) thick of the loaded thermal print media.
Inches).

The purpose of the circumferential recess on the vacuum imaging drum surface is to remove wrinkles in the dye donor material as it is mounted on the thermal print media during loading of the dye donor material. This ensures that no folds or wrinkles occur so that the dye donor material reaches the image area and does not significantly affect the target image. Vacuum holes in the surface of the vacuum imaging drum make it difficult to ensure that entrained air is removed, and the circumferential recess substantially eliminates air entrapment along the edges of the thermal print media. In addition, residual air between the thermal print media and the dye donor material adversely affects the intended image.

The purpose of the plane extending in the axial direction of the vacuum imaging drum is twofold. First, the leading and trailing edges of the dye donor material ensure that they are somewhat protected from the effects of turbulence during relatively high speed rotations experienced by the vacuum imaging drum during image processing. Thus, turbulence has less tendency to lift the leading or trailing edge of the dye donor material. Second, the axially extending plane of the vacuum imaging drum further ensures that the leading and trailing ends of the dye donor material are retracted from the periphery of the vacuum imaging drum. This can cause the dye donor material to come into contact with other parts of the image processing device, such as the printhead, causing misalignment and possible failure of the target image, causing harmful and catastrophic damage to the image processing device. Lower.

In addition, the plane extending in the axial direction of the vacuum imaging drum may be used when the dye donor material is held on the surface of the vacuum imaging drum by a vacuum from the inside of the vacuum imaging drum.
It acts to apply a bending force to the edge of the dye donor material. As a result, when the vacuum is released in the vacuum imaging drum, the ends of the dye donor material tend to lift off the surface of the vacuum imaging drum. Thus, releasing the vacuum eliminates the bending force on the dye donor material, which is utilized as an advantage in removing the dye donor material from the vacuum imaging drum.

The task of loading and unloading the dye donor material from the vacuum imaging drum requires precise alignment of the thermal print media and dye donor material. The leading edge of the dye donor material must be precisely controlled during the process. In image processing devices such as those disclosed in the above-mentioned U.S. patents, such leading edge control utilizes a multi-chamber vacuum imaging drum. One suitable control chamber is applied to the vacuum holding the leading edge of the dye donor material. Another chamber utilizing a separate valve controls the vacuum that holds the trailing edge of the thermal print media to the vacuum imaging drum.
In order to load a thermal print and dye donor material sheet with this arrangement, an image processor is required to send the leading edge of the thermal print media and the dye donor material to a vacuum port controlled by a chamber utilizing respective valves. It is. A vacuum is then applied so that the leading edge of the dye donor material is fixed relative to the vacuum imaging drum surface.

To remove the dye donor material or thermal print media (discarding used dye donor material or transporting the completed thermal print media to an output tray), the edge of the thermal print media or dye donor material is freed and a vacuum is applied. As if protruding from the surface of the image drum,
It is necessary to release the vacuum from the same chamber. The image processor then positions the articulating skive in the path of the free rim and raises the rim further to send the dye donor material to a waste container or the output tray.

The sheet material exit drive mechanism includes a waste exit for the dye donor material and a print thermal print media sheet material exit. The dye donor material outlet drive mechanism comprises a waste dye donor material stripper blade positioned adjacent to the upper surface of the vacuum imaging drum. At the removal position, the stripper blade is in contact with the waste dye donor material on the vacuum imaging drum surface. When not in operation, the stripper blade is moving up and away from the vacuum imaging drum surface. A driven waste dye donor material drive mechanism belt is disposed horizontally to carry the waste dye donor material, which is removed from the surface of the vacuum imaging drum by a stripper blade and to an outlet formed outside the image processing apparatus. The waste container for waste dye donor material is separated from the image processing device. The print thermal print media sheet material exit drive mechanism comprises a movable thermal print media sheet material stripper blade positioned adjacent the upper surface of the vacuum imaging drum. At the removal position, the stripper blade is in contact with the printed thermal print on the vacuum imaging drum surface. In the inactive position, the stripper blade has moved up and away from the vacuum imaging drum surface. The driven thermal print media sheet material drive belt is positioned horizontally and carries the printed thermal print media removed by the stripper blade from the surface of the vacuum imaging drum. Then, the print thermal print medium on which the target image has been created is transported to an exit tray outside the image processing apparatus.

Although the arrangement of currently known and used image processing devices is satisfactory, there is room for improvement. In a laser thermal imaging device, as the vacuum imaging drum rotates, the printhead moves along the vacuum imaging drum in a path (slow scanning direction) parallel to the longitudinal axis of the vacuum imaging drum. The linear motion system moves the printhead in a "slow scan" direction from the origin to the start of a scan point where image data begins to be written to the opposite end of the drum. The combined movement of the printhead in the slow scan direction and the vacuum image drum rotation perpendicular to the printhead movement (fast scan direction) results in a single continuous spiral written image around the vacuum image drum. Is formed.

However, in the target image, various workpieces are generated due to periodic disturbance due to slight displacement during rotation of the drum of the linear motion control system. Indeed, since the system response is finite due to system inertia, what happens in an attempt to track the perturbation of rotational motion results in oscillations in a linear system. The frequency-dependent periodic perturbations, their associated amplitudes and phases, result in visually objectionable patterns occurring in the target image.

[0023]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and in order to overcome the above-mentioned drawbacks, an irregular pattern of noise called white noise is applied to the movement of the linear motion control system. The purpose is to induce artificially.

[0024]

SUMMARY OF THE INVENTION The foregoing objects are attained by providing a printhead, a vacuum imaging drum adapted to receive thermal print media on the drum, a lead screw for moving the printhead, and a vacuum imaging drum. A motor that rotates the lead screw to produce a linear movement of the print along a line parallel to the vertical axis, and controls the linear movement of the print head at a speed synchronized with the rotation of the vacuum imaging drum;
This is achieved by an image processing device comprising a linear motion control system that shuts off the motor drive with a random delay as the vacuum imaging drum rotates.

A further object is to provide a print head, a vacuum imaging drum adapted to receive a print medium on the drum, and an operation associated with the vacuum imaging drum, wherein each rotation synchronization pulse signal upon rotation of the vacuum imaging drum. An encoder that generates once, a motor that causes a linear movement of the print head along a line parallel to the vertical axis of the vacuum imaging drum, and a synchronous pulse signal received from the encoder and drives the motor to rotate the vacuum imaging drum. Generates a uniform pulse train that moves the printhead along the surface of the vacuum imaging drum at a speed that is synchronized with and interrupts the uniform pulse train that causes a random delay in the linear movement of the printhead as the vacuum imaging drum rotates This is achieved by an image processing apparatus comprising a linear motion control system.

A further object of the present invention is a method of exposing an image to a thermal print medium, the method comprising: rotating a vacuum image drum of an image processing apparatus having a thermal print medium on a drum; Generates once for each pulse signal, sends a synchronization pulse signal to the linear motion control system, and images at a speed synchronized to the rotational speed of the vacuum imaging drum in a linear direction along a line parallel to the printhead longitudinal axis. Each step of generating a uniform pulse train to drive the printhead of the processing device and interrupting the uniform pulse train so as to cause a random delay in the drive of the printhead in a linear direction when the vacuum imaging drum rotates. Is achieved.

In the arrangement of the present invention, minor changes in the linear motion control system are not required for the changes required for the rest of the image processor. The present invention is directed to overcoming one or more of the problems set forth above. To summarize briefly,
According to one aspect of the invention, the invention resides in an image processing apparatus for receiving a thermal print material for processing a target image on a thermal print medium and a dye donor material. The image processor comprises a vacuum imaging drum that holds a sheet of dye donor material and a sheet of thermal print media. In the present invention, an irregular paran of noise, commonly referred to as white noise, is artificially induced in the linear motion control system at an appropriate amplitude and speed, and the amplitude and speed are both the size of the image over the length of the image. It is randomly variable in a way that not only preserves accuracy but also does not cause significant errors in dot placement. Thus, undesirable periodic patterns are masked or masked and cannot be identified in the target image, thereby improving the image quality of the target image.

Although not described in detail, the invention may be applied to other applications utilizing linear motion control systems, such as films,
It will be apparent to those skilled in the art that it can also be used for plates or inkjet writers.

[0029]

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawings, like reference numerals designate like or corresponding parts throughout the views.
FIG. 1 shows an image processing apparatus 10 according to the present invention. The image processing apparatus 10 includes an image processing housing 12 having a protective cover.
including. A movable, hinged image processing door 14 is mounted to the front of the image processing housing 12, and a lower sheet material tray 50a and an upper sheet located inside the image processing housing 12 for supporting thermal print media 32 in the housing. Access to the material tray 50b is enabled. Only one of the sheet material trays 50a, 50b is moved from the sheet material tray to the thermal print medium 3.
2 to create a target image; one of the sheet material trays 50a, 50b holds any of the alternative types of thermal print media 32 or functions as a backup sheet material tray. In this regard, lower sheet material tray 50a includes lower sheet material tray 50a and, ultimately, lower media lift cam 52a for lifting thermal print media 32, and includes rotatable lower media roller 54a and second rotatable upper media roller. When both rollers are rotating toward 54b, it allows the thermal print media 32 of the lower sheet material tray 50a to be pulled upward toward the movable media guide 56. Upper sheet material tray 50b
Includes an upper sheet material tray 50b and an upper media lift cam 52b for lifting the thermal print media 32 in the upper sheet material tray 50b toward an upper media roller 54b that is directed toward a movable media guide 56.

Movable media guide 56 initially has a pair of media guide rollers 58 which engage with thermal print media 32 to assist upper media rollers 54b in transporting to media staging tray 60, thereby allowing thermal print media 3 to move.
Guide 2 The media guide 56 is mounted and hinged at one end to the racebed scan frame 202 (FIG. 2) and is unconstrained at the other end to allow multiple positioning of the media guide 56. As shown in the position,
The media guide 56 then rotates downward at the unconstrained end, and the direction of rotation of the upper media roller 54b is directed upward through the inlet passage 204 under a pair of media guide rollers 58 to provide a rotatable vacuum imaging drum. The movement is reversed for movement of the moving thermal print medium 32 in the media staging tray 60 around 300.

Roll 30 of dye donor roll material 34
Is connected to a media carousel 100 at the bottom of the image processing housing 12. A four roll 30 is utilized, but only one is shown for clarity. Each roll 30
Include dye donor materials 34 of different colors, generally black, yellow, magenta, and cyan. The above dye donor roll material 3
4 is ultimately cut into dye donor sheet material 36 and is directed to a vacuum imaging drum 300 to form a media containing dye that is transferred to thermal print media 32, as described in more detail below. In this regard,
A media drive mechanism 110 is attached to each roll 30 of dye donor roll material 34, and the dye donor roll material of interest 34 has three media drive rollers 112 by being metered upwards to a media knife assembly 120. .
After the dye donor material 34 has reached a predetermined position, the media drive rollers 112 stop driving the dye donor material 34 and the two media knife blades 122 located at the bottom of the media knife assembly 120 cause the dye donor material 34 is cut into a dye donor sheet material 36. The lower media roller 54a and the upper media roller 54b, along with the media guide 56, then pass the dye donor sheet material 36 on the media staging tray 60 and ultimately go to the vacuum imaging drum 300 for thermal printing on the vacuum imaging drum 300. Align the thermal print media 32 with the thermal print media 32 using the same method described above for changing the media 32. The dye donor sheet material 36 is placed on the thermal print media 32 with a narrow space or gap between the two created by the microbeads embedded in the thermal print media 32 surface.

The laser assembly 400 includes a number of laser diodes 402 therein. The laser diode 402 is connected to the distribution block 406 by a fiber optic cable 404 and finally to the print head 500. Printhead 500 directs thermal energy from laser diode 402 that causes dye donor sheet material 36 to change to the desired color through the gap with thermal print media 32. As shown in FIG. 2, the printhead 500 includes a lead screw drive nut 254.
And a lead screw 250 by a drive coupling (not shown).
And allows axial movement along the longitudinal axis of the vacuum imaging drum 300 to transfer data to form a target image on the thermal print media 32.

For writing, the vacuum imaging drum 300 rotates at a constant speed and the printhead 500 begins to move at one end of the thermal print media 32 to transfer a specific dye donor sheet material 36 on the thermal print media 32. The entire length of the thermal print medium 32 is traversed to complete the process. After the print head 500 has completed the transfer process for the particular dye donor sheet material 36 on the thermal print media 32, the dye donor sheet material 36 is then removed from the vacuum imaging drum 300 and the skive or jet umbrella 16 (FIG. 1) from the image processing housing 12. The dye donor sheet material 36 is ultimately removed by the user and placed in the waste container 18. Thereafter, the above described method is repeated for the other three rolls 30 of the dye donor material 34.

After the colors from four but not limited to four of the dye donor sheet materials 36 have been transferred and the dye donor sheet material 36 has been removed from the vacuum imaging drum 300,
The thermal print media 32 is removed from the vacuum imaging drum 300 and is transported by the transport drive mechanism 80 to the color coupling assembly 180.
Transported to The entrance door 182 of the color combination assembly 180
The thermal print media 32 is open to allow entry into the color combining assembly 180, and once the thermal print media 32 enters the color combining assembly 180, it is closed. The color combining assembly 180 processes the thermal print media 32 and further couples the transferred color to the thermal print media 32, encapsulating the microbeads on the media. After the color combining process is completed, the media exit door 184 opens and the thermal print media 32 having the target image on the media exits the color combining assembly 180 and the image processing housing 12 and goes to the media stop 20.

Referring to FIG. 2, the vacuum imaging drum 30
0, Image processing apparatus 1 including print head 500 and lead screw 250 assembled in race bed scanning frame 202
1 shows a perspective view of a No. 0 racebed scanning subsystem 200. FIG. Vacuum imaging drum 300 is mounted for rotation about the X-axis of racebed scanning frame 202. The print head 500 is movable with respect to the vacuum imaging drum 300 and is arranged to direct a light beam to the dye donor sheet material 36. The light beam from the print head 500 of each laser diode 402 (not shown in FIG. 2) is individually modulated by a modulating electronic signal from the image processor 10 representing the shape and color of the original image, resulting in a dye donor. The colors on the sheet material 36 are heated, and the presence of the colors vaporizes only those heated areas required on the thermal print media 32. This reconstructs the shape and color of the original image.

The printhead 500 is mounted on a movable translation stage member 220 and is supported on translation bearing rods 206 and 208 for low friction sliding movement. The translation bearing rods 206 and 208 are strong enough to bend or deform as little as possible between the points of attachment, are positioned as parallel as possible to the X axis of the vacuum imaging drum 300, and the axis of the printhead 500 is Perpendicular to the X axis. The front translation bearing rod 208 is mounted on the translation stage member 220 vertically and horizontally with respect to the X axis of the vacuum imaging drum 300.
The rear translation bearing rod 206 is mounted on the translation stage member 220 only with respect to the rotation of the translation stage member 220 about the front translation bearing rod 208, so that the member tightens, rattles, or neglects during creation of the target image. Translation stage member 2 which gives undesirable vibration or jitter to print head 500
There are no 20 over constraints.

Referring to FIGS. 2 and 3, the lead screw 250 is shown at the drive end to a linear drive motor 258, including an elongated threaded shaft 252 mounted to the racebed scan frame 202 by radial bearings 272. The lead screw drive nut 254 is
A hollow center for engaging the threads of the threaded shaft to allow the lead screw drive nut 254 to move axially along the threaded shaft 252 as it is rotated by the linear drive motor 258. The portion 270 includes a groove. Lead screw drive nut 254 is integrally mounted to printhead 500 by a lead screw coupling (not shown) and a peripheral translation stage member 220 so that threaded shaft 252 is rotated by linear drive motor 258. First, the lead screw drive nut 254 moves the translation stage member 220 axially along a threaded shaft 252 that ultimately moves the printhead 500 axially along the vacuum imaging drum 300.

As best shown in FIG. 3, an annular shaft loading magnet 260a is integrally mounted to the drive end of the threaded shaft 252, and another annular shaft loading magnet 260b mounted to the race bed scanning frame 202. They are separated. Axial load magnets 260a and 260b are preferably made of a rare earth material such as neodymium-iron-boron. Typical circular boss 26 of threaded shaft 252
2 is in the hollow portion of the annular shaft load magnet 260a and has a generally V-shaped surface at the end for receiving the ball bearing 264. Circular insert 266 may be connected to another annular shaft load magnet 260.
b, having a precisely shaped surface at one end for receiving the ball bearing 264 and a flat surface at the other end for receiving the end cap 268. End cap 2
68 is disposed on the ring-shaft load magnet 260b, and covers and protects the ring-shaft load magnet 260b.
Attached to racebed scan frame 202 to provide zero axis stop. The circular insert 266 is preferably comprised of a material such as Rulon J® or Delrin AF®, both of which are well known to those skilled in the art.

The lead screw 250 functions as follows. The linear drive motor 258 is energized and imparts rotation to the lead screw 250 as indicated by the arrow in FIG. 3 to move the lead screw drive nut 254 axially along the threaded shaft 252. Annular shaft loading magnets 260a and 260b are magnetically attracted to each other to prevent axial movement of lead screw 250. However, annular shaft load magnets 260a, 2
60b, that is, clearly the threaded shaft 2
While the 52 is rotating, the annular shaft load magnets 260a, 26
The ball bearing 264 rotates the lead screw 250 while maintaining a slight separation that prevents mechanical friction during 0b.

Referring to FIG. 4, a vacuum imaging drum 300
FIG. Vacuum imaging drum 300 has hollow interior 30
4 having a cylindrical vacuum drum housing 302.
Further, the vacuum imaging drum 300
From the hollow interior 304 of the thermal print media 32 as the vacuum imaging drum rotates.
And a plurality of vacuum grooves 302 and vacuum holes 306 to support and maintain the position of the dye donor sheet material 36.

The end of the vacuum image drum 300 is the vacuum end plate 30.
8 and the drive end plate 310. Drive end plate 310 is equipped with a centrally located drive spindle 312 that extends outwardly through support bearings 314. Drive spindle 312 extends through support bearing 314 and is stepped down to receive a DC drive motor armature held by a drive nut.
The DC motor starter 342 is a race scan frame member 2
The DC drive motor armature, which is held in a fixed manner by 02 and surrounds the DC drive motor armature, forms a reversible and variable DC drive motor for the vacuum imaging drum 300. As described above, details of the driving elements of the vacuum imaging drum 300 are described in U.S. Pat.
No. 428,371. At the end of the drive spindle 312, a drum encoder (FIG. 8) is mounted and sends a timing signal to the image processing device 10.

The vacuum spindle 318 has a central vacuum opening 320 aligned with a vacuum fitting fitted with an external flange rigidly attached to the racebed scanning frame 202.
Having. The vacuum fitting has an extension that extends away from but near the vacuum spindle 318, thus creating a small clearance. In the above arrangement, a slight vacuum leak occurs between the outside diameter of the vacuum fitting and the inside diameter of the central vacuum opening 320 of the vacuum spindle 318. This ensures that there is no contact between the vacuum fitting and the vacuum imaging drum which imparts uneven movement or jitter to the vacuum imaging drum 300 during rotation. An example of such an arrangement is cited in U.S. Pat. No. 5,428,371, as above.

The opposite end of the vacuum fitting is 60-70 cfm
Connected to a high-volume vacuum blower capable of generating 50-60 inches of water (93.5-112.2 mm of mercury) with an air flow volume of 28.368-33.096 liters per second. A vacuum is created in the vacuum imaging drum 300 to maintain the various internal vacuum levels of the vacuum imaging drum required during loading, scanning and removal of the thermal print media 32 and dye donor sheet material 36 to produce the desired image. Form. When the medium is not loaded in the vacuum imaging drum 300, the internal vacuum level of the vacuum imaging drum 300 is about 254-4.
81mm (10-15 inches) (18.7-2 mercury column)
8.05 mm). When the thermal print medium is just loaded in the vacuum imaging drum 300, the internal vacuum level of the vacuum imaging drum 300 is about 508-6 of water column.
35mm (20-25 inches) (37.4-4 mercury column)
6.75 mm), which is the thermal print medium 3
This is the level required when removing the dye donor material 36 so that the 2 does not move, otherwise the match between colors cannot be maintained. When both the thermal print media 32 and the dye donor sheet material 36 are fully loaded into the vacuum imaging drum 300, the internal vacuum level of the vacuum imaging drum 300 in this arrangement will be approximately 1270-1524 mm water column (50
-60 inches) (93.5-112.2 mm of mercury).

The outer surface of the vacuum imaging drum 300 has an axially extending plane 322 (shown in FIGS. 4 and 5) extending about 8 degrees around the circumference of the vacuum imaging drum 300. The vacuum imaging drum 300 extends from the axially extending plane 322 on the circumference of the vacuum imaging drum 300 to the other of the axially extending planes 322 and about 25.4 mm from one end of the vacuum imaging drum 300. (1 inch) to vacuum imaging drum 3
Donor support ring 32 forming a circumferential recess 326 that extends circumferentially from the other end of 00 to about 1 inch (25.4 mm).
4

When attached to the vacuum imaging drum 300,
The thermal print media 32 is mounted in a circumferential recess 326 (shown in FIGS. 6a to 6c) so that the donor support ring 324 is about 0.004 inch (0.102 mm).
Has a thickness substantially equal to the thickness of the loaded thermal print medium 32. The purpose of the circumferential recess 326 on the surface of the vacuum imaging drum 300 is to
6 to remove wrinkles in the dye donor sheet material 36 when the dye donor sheet material is mounted on the thermal print media 32 during loading. This means
It ensures that no folds or wrinkles occur so that the dye donor sheet material 36 does not reach the image area and have a significant adverse effect on the target image. It is difficult to ensure that the air trapped by the vacuum holes 306 in the vacuum imaging drum 300 is removed, and the circumferential recess 326 substantially eliminates air trapping along the edge of the thermal print media 32. In addition, the residual air between the thermal print media 32 and the dye donor sheet material 36 adversely affects the target image.

The axially extending flat surface 322 is such that the leading and trailing edges of the dye donor sheet material 36 are subject to the effects of increasing turbulence during relatively high speed rotation of the vacuum imaging drum 300 during the image scanning process. Make sure you are somewhat protected. Thus, the increased turbulence tends not to lift or separate the leading or trailing edge of the dye donor sheet material 36 from the vacuum imaging drum 300. Further, the axially extending flat surface 322 ensures that the front and rear ends of the dye donor sheet material 36 are retracted from the periphery of the vacuum imaging drum 300. This causes the dye donor sheet material 36 to cause media jams in the image processing device 10, resulting in harmful damage to the image processing device resulting in possible loss of the target image and possible damage to the print head 500. Image processing device 1
Zero the likelihood of contact with other components.

The control circuit shown in the block diagram of FIG. 8 represents a linear motion system 900, and the present invention allows the printhead 500 to be dynamically (vacuum imaged) at any programmable traversal speed (based on the number of channels). In response to changes in rotational speed). To drive the lead screw 250, the present invention employs a stepper motor 162 (FIG. 8) that can be driven in a microstepping mode
Use

As shown in FIG. 8, the motor 345 drives the vacuum imaging drum 300 in a rotatable manner. Encoder pulses from the image drum encoder 344 are input to a programmable frequency divider (902) via a random disable unit (903). A program divisor (n) is added and the input encoder frequency is divided into reduced output values. Then the pulse output from the programmable frequency divider 902 is
Acts as a clock pulse and serves as a stepper motor controller 1
66 circuits are driven. (Stepper motor controller 16
6 is IM483 of Intelligent Motion Systems, Inc.
Standard components such as high performance microstepping controllers. ) Pulse counter 904 tracks the number of input clock pulses generated by the above circuit. When the programmable threshold arrives (MAXPL
USE), the pulse counter 904 no longer applies the clock pulse input to the stepper motor controller 166 (using the standard AND gate logic control circuit 906), effectively stopping the stepper motor 162. This MAXPU
The LSE value arrives at the end of each swath 450, so that the printhead 500 stops moving, but the vacuum imaging drum 300 has a "dead band" 200
0 (where image formation is not performed because there is no image receiving medium). In preparation for starting the next swath 450, the drum encoder 344 sends an index pulse. This means that the pulse counter 90
4 is reset and the clock pulse is input to the stepper motor controller 166, thus restarting the stepper motor 162 for the next swath 450.

As described above, the control circuit determines two values (n and MAXPULS) that change depending on the number of channels.
E). Where n is a truncation value equal to the encoder resolution divided by the desired microsteps per revolution (pulses / microsteps), and MAXPULSE is equal to the desired number of microsteps per revolution. As shown in the table of FIG.
The channel swath is a programmable frequency divider 9
An n value of 22 is required as input to 02. Before the stepper motor controller 166 input fails, the pulse counter 904 can cause 488 (MAXPULSE) pulses to be input to the stepper motor controller 166. 10,000 pulses / rotary drum encoder 344
Thus, after division by a programmable frequency divider 902 value (here 22), the first 9,856 pulses are 448 microsteps (seven full steps with 64 microsteps per step occur).
Occurs. The rotation of the stepper motor 162 is then based on 144 pulses (10, 0, 0) from the drum encoder 344.
(00 minus 9,856) does not work.
(These 144 pulses occur during the "dead band" between the swaths 450.) The table in FIG. 8 shows typical values for n and MAXPULSE, indicating a variable number of channels. In each case, different values of n and MAXPULSE are added. Note that the present invention allows for a different number of full steps for each number of designated channels, each full step comprising a number of microsteps (64 microsteps per step in the preferred embodiment of the present invention). deep. The predetermined program values of n and MAXPULSE are stored in the program memory so that the values are accessible and available for a certain number of channels. Using the above method, the stepper motor speed is appropriately varied based on the number of channels used.

In order to generate a target image, the vacuum image drum 300 is rotated by the operation of the motor 345 to a desired speed. As described above, the vacuum imaging drum 30
0 is coupled to the drum encoder 344 and generates 10,000 pulses per rotation synchronization signal to the data path electronics and linear motion system 900. With each synchronization pulse, the linear motion produces a constant uniform pulse train, and the print head 500 moves along the vacuum imaging drum 300 at the rotating and synchronized speed of the vacuum imaging drum 300 and in proportion to the width of the write swath 450. Then, the stepper motor 162 is driven (FIG. 7). The pattern followed by the printhead 500 along the rotating vacuum imaging drum 30 is spiral as shown in FIG. Write swath 450 follows vacuum imaging drum 300 as shown separately in FIG. 7 for clarity. In actual operation, each writing swath 450 is immediately adjacent to a preceding writing swath 450 that follows the surface of the vacuum imaging drum 300. In FIG. 7, reference numeral 456 represents the position of the printhead 500 at the beginning of the spiral, and reference numeral 458 represents the position of the printhead 500 at the spiral end. Because of the sinusoidal nature of the position error inherent to the stepper motor drive system, various types of discriminating and preferably imaging artifacts such as banding are apparent. Some more prominent patterns are
Caused by swath and swath phase shift.

To prevent such disturbances / banding, an artificial random pattern of noise is applied to the linear motion control system 900 at an appropriate amplitude and speed, both randomly variable. This obscures or masks the periodic pattern, thus making it indistinguishable, but not only preserves the dimensional accuracy of the target image over the length of the target image, but also has significant consequences for dot placement. Does not induce errors. This is achieved by a high frequency counter that runs periodically and ends in a
This is done by artificially interrupting the uniform pulse train that controls 62. This delay time must be in a suitable range so that the end of one delay period occurs before the start of the next synchronization.

FIG. 9 shows an index pulse and an encoder pulse.
8 and the step clock shown in FIG.
Not use normal dithering
A timing diagram (line AF) is shown. Demonst
For modulation purposes, a specific example is the 10 frequency division
I use 9 and MAXPULSE. Index par
Luz (Line A, INDEX PULSE) is a stepper
Serves as a synchronization pulse for the clock. Program
Frequency divider 902 (10 in this example)
Coda clock (line B, ENCODER) CLK)
And the step clock (line C NORMAL)
STEP CLK). MAXPULSE
(9 in this example) When a step clock pulse is generated
Step until the index pulse occurs again.
The clock does not work.

The dither function uses the encoder clock
9 and STEP in FIG. CLK DITHERE
As shown by D (line F),
And works to generate a random time shift. DIT
HERED DISABLE (Line D) (Random
Is 908), the encoder clock will not work
Indicate the random time where desired. ENC
ODER CLK GATED (line E) is STEP
CLK Step color indicated as DITHERED
Block that results in a variable random time delay in the
Indicates a coder clock.

In this example, care must be taken in the design of the ninth such that the last step clock pulse occurs before the subsequent index pulse.
If the integration time delay is too long, then position control will be lost due to misstep clock pulses that result in undesirable image compression and excessive dot placement errors.

The invention has been described by reference to a preferred embodiment. However, it will be understood and understood that variations and modifications may be effected by those of ordinary skill in the art without departing from the scope of the invention as described herein and within the scope of the invention as defined by the appended claims. Will.
For example, the present invention is applicable to an image processor including an inkjet printer. In addition, dye donors also include dyes, pigments, or other materials that are transferred to the thermal print media. Paper, thermal print media
Films, plates and other materials that can receive or form an image are also included.

[Brief description of the drawings]

FIG. 1 is a side view in a vertical sectional view of an image processing apparatus of the present invention.

FIG. 2 is a perspective view of a racebed scanning subsystem or writing engine of the present invention.

FIG. 3 is a horizontal sectional view of a lead screw of the present invention, which is a partially simulated plan view.

FIG. 4 is a perspective view of a print swath generated by rotation of a drum and a lead screw movement for directly printing on an intermediate receiver.

FIG. 5 is a plan view of the surface of the vacuum imaging drum of the present invention.

FIGS. 6 (a)-(c) are plan views of a vacuum imaging drum showing the order of placement of thermal print media and dye donor material.

FIG. 7 is a perspective view of a print swath generated by rotation of a vacuum imaging drum and a lead screw movement of a print head for printing a target image.

FIG. 8 is a schematic diagram of a linear motion control system according to the present invention.

FIG. 9 is a timing diagram illustrating a relationship between an index pulse, an encoder pulse, and a step clock according to the present invention.

[Explanation of symbols]

 162 Step motor 166 Step motor controller 344 Image drum encoder 902 Frequency divider 904 Pulse counter 906 Standard AND logic control circuit 2000 Dead band

Claims (3)

[Claims] A print head, a vacuum imaging drum adapted to receive a thermal print medium on the drum, a lead screw for moving the print head, and a line parallel to a longitudinal axis of the vacuum imaging drum. A motor for rotating the lead screw so as to produce a linear movement of the print along with controlling the linear movement of the printhead at a speed synchronized with the rotation of the vacuum imaging drum, and randomizing when the vacuum imaging drum rotates A linear motion control system for interrupting the driving of the motor with a long delay. 2. A printhead, a vacuum imaging drum adapted to receive a print medium on the drum, and operatively associated with the vacuum imaging drum, once per rotation synchronization pulse signal during rotation of the vacuum imaging drum. An encoder that generates a motor that causes the print head to move linearly along a line parallel to the longitudinal axis of the vacuum imaging drum; receives the synchronization pulse signal from the encoder, drives the motor, and drives the vacuum Generating a uniform pulse train that moves the printhead along the surface of the vacuum imaging drum at a speed synchronized with the rotation speed of the imaging drum, wherein the randomness in the linear motion of the printhead as the vacuum imaging drum rotates A linear motion control system that interrupts the uniform pulse train causing a long delay. Apparatus. 3. A method for exposing an image on a thermal print medium, the method comprising: rotating a vacuum image drum of an image processing apparatus having a thermal print medium on a drum; and a rotation synchronization pulse based on the rotation of the vacuum image drum. Generating once for each signal, transmitting the synchronization pulse signal to the linear motion control system,
Generating a uniform pulse train to drive the print head of the image processing device at a speed synchronized with the rotational speed of the vacuum imaging drum in a linear direction along a line parallel to the longitudinal axis of the print head; Blocking the uniform pulse train so as to cause a random delay in driving the printhead in a linear direction as the vacuum imaging drum rotates.