The present invention relates to a technique for controlling image forming position of a printing apparatus. More particularly, it relates to control of a conveying roller which conveys a printing medium.
An image forming apparatus of an ink jet type records on a printing medium by discharging ink from a print head during reciprocating motion in a main scanning direction. It forms an image by repeated recording in the main scanning direction while conveying the printing medium in a sub-scanning direction by means of a conveying roller. Generally, when conveying a printing medium, such as paper, on a conveying roller and the like, there are variations in the amount of conveyance (feed rate) depending on the mounting condition of the conveying roller, type of printing medium, and the like. Thus, patent document 1 discloses a technique for determining a correction value for the amount of conveyance based on printing results of a plurality of test patterns recorded using different correction values. That is, this technique selects the pattern which gives the best printing result from among the recorded test patterns and thereby determines a parameter for use to drive the conveying roller.
(Patent document 1) Japanese Patent Laid-Open No. 2003-011344
However, the technique disclosed in the above document poses the following problems if there are variations in the amount of conveyance within one roller rotation (one cycle). One of the problems is that in order for the correction value that depends on the phase of the conveyance roller during execution of an adjustment operation to be set, a different correction value is determined each time the adjustment operation is executed, the result being that a stable image quality cannot be realized. Another problem is that this technique is incapable of correcting image forming irregularities known as white streaks and black streaks caused by variations during one roller rotation.
Variations in the feed rate caused by variations in roller profile, flexure of the roller, mounting of a roller support member, and the like with a period equal to one rotation of the roller have been negligible in conventional recording resolution. However, with recent improvement in recording resolution, the effect of feed rate variations with a period equal to one rotation of the roller has increased so much in a relative manner that the variations can no longer be ignored. Consequently, conveying control with a higher accuracy is required.
Naturally, with the improvement in recording resolution, machine accuracy has also been improved to ensure recording quality. However, it is technically difficult to increase machine accuracy to the extent that the effect of the feed rate variations with a period equal to one rotation of the roller will be negligible and it is not desirable in terms of cost performance.
The present invention has been made in view of the above problems and has an object to provide a technique which can reduce misregistration in a conveying direction of a printing medium.
To achieve the above object, the present invention is configured as follows.
According to one aspect of the present invention, a printing apparatus which prints an image on a printing medium using a print head which discharges ink, the printing apparatus comprises: a conveyance unit for conveying the printing medium by rotating a roller; a detection unit for detecting a conveyance amount of a printing medium conveyed by rotating the roller in less than one rotation; an acquisition unit for acquiring a conveyance amount of the printing medium corresponding to a predetermined rotation amount of the roller by detecting the conveyance amount a plurality of times; and a setting unit for setting a rotation amount of the roller when forming an image on the printing medium based on a conveyance amount of a printing medium corresponding to the acquired predetermined rotation amount of the roller.
According to another aspect of the present invention, a printing method for a printing apparatus which has a print head which discharges ink, a conveyance unit which conveys a printing medium by rolling a roller, the printing apparatus prints an image on the printing medium using the print head, the printing method comprises: the detection step of detecting a conveyance amount of a printing medium conveyed by rotating the roller in less than one revolution; and the setting step of acquiring a conveyance amount of the printing medium corresponding to a predetermined rotation amount of the roller by detecting the conveyance amount a plurality of times, and setting a rotation amount of the roller when an image is formed on the printing medium based on an acquired conveyance amount of a printing medium.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
The present invention can provide a technique which can reduce misregistration in the conveying direction of a printing medium.
Preferred embodiments of the present invention will be described in detail below in an exemplary manner with reference to the drawings. However, components of the embodiments are strictly exemplary and are not intended to limit the scope of the present invention.
In the embodiments described below, a recording apparatus which uses a print head of an ink jet type will be taken as an example. The term “record” (or “print”) herein not only means forming meaningful information such as characters or images, but also broadly means forming images, patterns, and the like on a printing medium or processing a printing medium regardless of whether the information is meaningful or meaningless or whether the information is visible to human vision.
Also, the term “printing medium” means not only paper used on typical recording apparatus, but also broadly means something that can receive ink, such as cloth, plastic film, metal plates, glass, ceramics, wood, and leather.
Furthermore, the term “ink” (also referred to as “liquid”) should be interpreted broadly as is the case with the term “record” (or “print”). That is, it means a liquid which may be used to form images, patterns and the like or to process a printing medium, or to process ink when applied to a printing medium. The phrase “process ink” means the process of solidifying or insolubilizing coloring material in the ink applied to the printing medium, for example.
Besides, the term “nozzle” refers collectively to discharge ports, flow paths connected to them, and elements which generate energy used to discharge ink unless otherwise specified.
A first embodiment of an image forming apparatus according to the present invention will be described below by taking a color ink jet printer as an example.
<Equipment Configuration>
In
Reference numeral 106 denotes a pulley which rotates when receiving power from a carriage motor as a drive source for causing round-trip scanning of a carriage unit 102 in a main scanning direction. Reference numeral 107 denotes a carriage belt which transmits motor drive power received through contact with the pulley to the carriage unit 102. Reference numeral 111 denotes a guide shaft located in the main scanning direction to support the carriage unit 102 and guide its movement. Reference numeral 109 denotes a transmissive photocoupler mounted on the carriage unit 102, and 110 denotes a light shielding plate installed near a carriage home position. Reference numeral 112 denotes a home position unit (also called a recovery unit) including a cap member which caps the front face of an ink jet head and a suction unit which sucks ink by creating negative pressure in this cap, and further including a recovery system such as a member which wipes the front face of a head.
Reference numeral 113 denotes an ejection roller used to eject the printing medium such as paper. It sandwiches the printing medium in cooperation with a spur roller (not shown) and ejects it out of the printer. In addition, there is a line feed unit which delivers a printing medium by a predetermined amount in a sub-scan direction.
In
The print head 201 has a Bk-ink discharge unit consisting of an array of nozzles which discharge Bk ink as well as nozzle groups which respectively discharge Y, M, and C inks. The nozzle groups are arranged in line integrally composing a color-ink discharge unit. They are installed in the same range as Bk-ink discharge ports.
Discharge ports 222 are formed at a predetermined pitch on a discharge port surface 221 which faces a printing medium 108 such as paper with a predetermined clearance (e.g., approximately 0.5 to 2.0 mm). Also, electrothermal transducers (such as heaters) for generating energy used in ink discharge are installed along the wall of each flow path 224 connecting each of the discharge ports 222 with a common ink chamber 223.
Further, a cartridge 150 is mounted to a cartridge unit 102 in positions such that the plurality of discharge ports 222 will intersect a scanning direction of the carriage unit 102. Appropriate electrothermal transducers (hereinafter referred to as “discharge heaters”) 225 are driven based on an image signal or discharge signal inputted via the electrical contact 219. Specifically, the inks in the flow paths 224 are caused to undergo film boiling and the inks are discharged through the discharge ports 222 under the pressure of generated bubbles.
The reflective optical sensor 130 has a light-emitting unit 331 and light-receiving unit 332. Light Iin 335 emitted from the light-emitting unit 331 is reflected by a surface of the printing medium 108. Reflected light includes regularly reflected light and irregularly reflected light. To detect density of an image formed on the printing medium 108 more accurately, it is desirable to detect irregularly reflected light Iref 337. For this reason, the light-receiving unit 332 is placed such that it receives reflected light at an angle different from an incident angle of light from the light-emitting unit 331 so as to detect scattered reflection in this embodiment. A detection signal resulting from the detection is transmitted to an electrical circuit board of the printer.
It is assumed here that a white LED or three-colored LED is used as the light-emitting unit and photodiode sensitive to a visible-light region is used as the light-receiving unit to make registration adjustments for all the head which discharge C, M, Y, or K inks. However, it is preferable to use a three-colored LED capable of selecting colors which have high detectivity if adjustments are made among different colors when detecting relationship between relative recording position and density of colors printed one over another.
Incidentally, in detecting the density of an image formed on the printing medium 108, it is only necessary to detect a relative value rather than the absolute value of the density although details will be described later. Also, it is only necessary to have detection resolution enough to detect relative density differences among individual patterns belonging to an adjustment pattern group described later (hereinafter each pattern among adjustment patterns will be referred to as a patch).
Regarding stability of a detection system including the reflective optical sensor 130, it is sufficient if detected density differences are not affected during detection of one adjustment pattern group. Sensitivity is adjusted, for example, by moving the reflective optical sensor 130 to a margin of the printing medium. A possible adjustment method involves adjusting emission intensity of the light-emitting unit 331 or gain of detection amplifier of the light-receiving unit 332 such that a detection level will reach an upper limit. Incidentally, sensitivity adjustment is not essential, but it is a suitable method for improving an S/N ratio and increasing detection accuracy.
A controller 400 is a main control unit. It has a CPU 401 in the form of, for example, a microcomputer; ROM 403 which stores programs, required tables, and other fixed data; and RAM 405 with an area for use to load image data, work area, and the like. A host machine 410 is a source of image data. Specifically, it may be a computer which creates or processes images and other data related to printing, a reader which reads images, or the like. Image data, commands, status signals, and the like are transmitted and received to/from the controller 400 via an interface (I/F) 412.
A console 420 is constituted of a switch group which accepts commands from a user. It includes, a power switch 422, switch 424 used to start printing, and recovery switch 426 used to start suction recovery. It also includes a registration adjustment start switch 427 for manual registration adjustment and registration adjustment value setting input section 429 for use to enter adjustment values manually.
A sensor group 430 is used to detect condition of the apparatus. It consists of the reflective optical sensor 130, the photocoupler 109 used to detect the home position, a temperature sensor 434 mounted at an appropriate location to detect ambient temperature, and the like.
A head driver 440 is used to drive a discharge heater 441 in the print head 201 according to print data and the like. The head driver 440 has a shift register which align print data along the discharge heater 441 and a latch circuit which latches with an appropriate timing. Also, the head driver 440 has a logic circuit element which operates the discharge heater 441 in sync with a drive timing signal, timing setting unit which appropriately sets a drive timing (discharge timing) for dot formation/alignment, and the like.
The print head 201 is equipped with a sub-heater 442. The sub-heater 442 is used for temperature adjustment in order to stabilize ink discharge characteristics. It may be formed on the print head substrate simultaneously with the discharge heater 441 and/or mounted on the print head body or head cartridge.
A motor driver 450 drives a main scanning motor 452. A sub-scanning motor 462 is used to convey (sub-scan) the printing medium 108 and driven by a motor driver 460.
Normally, a printing medium such as paper is conveyed through rotation of a conveying roller (hereinafter referred to as a “roller”). For example, if the roller is 47 mm in circumference, the printing medium is conveyed 47 mm by one rotation of the roller. Generally, however, there is slight deviation in the amount of conveyance when a printing medium is conveyed by a conveying roller.
One of the components is a fixed component (A in
Incidentally, since the fixed component (A in
If it is assumed that the rotation angle of a roller for paper conveyance is constant and if roller cross-sectional shape is a perfect circle, when the roller is rotated by an angle of R, the amount of conveyance is a constant L0, as shown in
Such variations in the amount of paper conveyance dependent on the cycle of the roller affect actual images. Variations in the amount of paper conveyance dependent on the cycle of the roller mean deflection in the landing position of ink droplets.
In
Further, bending of the conveyance roller can be given as another cause for generation of a displacement component.
As explained above, several causes exist for differences in conveyance amount in response to the rotational starting position of the conveyance roller, that is, causes for differences in conveyance amount in a single revolution of the conveyance roller. Although there are several causes for the difference in conveyance amount, the problem occurring when an image is formed on a printing medium due to a differing conveyance amount is the same, and since it is possible to adapt to the shift in conveyance amount due to several causes in the present embodiment, the recording position misalignment in the conveyance direction can be reduced. Further, the application of the present invention is not limited to causes for the occurrence of the shift in conveyance amount explained above.
When the roller is located in L1 in
<Derivation of Fixed Component>
Normally, adjustment of the amount of paper conveyance unit adjustment of a fixed component (A in
However, as described above, the variations in the amount of conveyance have a period equal to one rotation of the conveying roller. In particular, if the period of variation can be approximated by one period of a sine function, it can be seen from
Thus, it can be seen that by controlling the rotation of the conveying roller based on the average amount of conveyance determined in this way, it is possible to reduce the effect of the fixed component (A in
<Detection of Displacement in Conveyance using Reference Patterns (Outline)>
Next, description will be given of a method for detecting displacement in conveyance corresponding to positions of the conveying roller.
Also, 640 nozzles are arranged in each nozzle column to provide a resolution of 600 dpi in the paper conveying direction. The EVEN and ODD nozzle columns of each color are placed being displaced 1/1200 inch in the paper conveying direction. Consequently, the resolution in the paper conveying direction is 1,200 dpi when both EVEN columns and ODD columns are used for recording.
In the following description, a print head with two nozzle columns per color as shown in
First, reference patterns (first patterns) indicated by white dots in
Next, the paper is conveyed by a distance equal to half the length of the nozzle column. Feed resolution is a variable which depends on printer performance, but it is assumed here that the paper can be conveyed theoretically at a resolution of 9,600 dpi. That is, the paper is conveyed theoretically at 1/9600 inch per pulse. Under these conditions, to convey the paper by a distance equal to half the length of the nozzle column:
640*25.4/1200=13.55 [mm],
a theoretical instruction pulse value (count) to be used is:
(640*25.4/1200)/25.4*9600=5120 (pulses)
After the paper conveyance, adjustment patterns (second patterns) indicated by black dots in
If the amount by which the paper is conveyed based on an instruction pulse value after the white dots are recorded is equal to half the length of the nozzle column, a region with an area factor of nearly 100% is formed by printing the black dots over the white dots as shown in
On the other hand, depending on the accuracy of the individual apparatus or changes in the printing medium caused by the environment and the like, the amount by which the paper is conveyed based on the instruction pulse value may deviate from the value equal to half the length of the nozzle column. In that case, even if black dots are overprinted, a patch with an area factor lower than 100% (50% at the minimum) will be formed as shown in
In forming a patch such as shown in FIG. 11B, suppose the area factor becomes 100% when the instruction pulse value is set, for example, at 5122 rather than 5120. In that case, it can be seen that for the combination of the given printer and printing medium, the correct instruction pulse value needed to feed the printing medium by 13.55 mm is 5122. That is, it is possible to derive the correct instruction pulse value by checking the area factors of the patches produced by varying the instruction pulse value for conveyance after white dots are recorded. The difference (+2 in this case) between the correct instruction pulse value (5122 in this case) and theoretical instruction pulse value (5120 in this case) corresponds to displacement in conveyance. A concrete method for constructing a patch using the above-described principle will be described below.
<Adjustment Patch Configuration Example 1>
Enlarged view A in
Enlarged view B in
Enlarged view C in
As described above, when recording a patch whose theoretical pulse adjustment value is “0,” the area factor is approximately 100%. However, depending on the accuracy of the individual apparatus or changes in the printing medium caused by the environment and the like, the amount of paper conveyance corresponding to the instruction pulse value can differ from its theoretical value. That is, a patch area factor of approximately 100% may be produced by a pulse adjustment value other than “0.”
Incidentally, the adjustment pattern of “+5” and adjustment pattern of “−5” in
<Adjustment Patch Configuration Example 2>
With configuration example 1, it is necessary to change the instruction pulse value during recording of a pattern. This makes it necessary to arrange patches in the paper conveying direction. However, the arrangement in the paper conveying direction results in increased paper consumption. On the other hand, configuration example 2 allows paper feed adjustment to be made without changing the instruction pulse value.
First, reference patterns (first patterns) indicated by white dots in
Next, to convey the paper by a distance equal to half the length of the nozzle column, the conveying roller is rotated with a theoretical instruction pulse value of 5120.
After the paper conveyance, adjustment patterns (second patterns) indicated by black dots in
Theoretically, the adjustment pattern at the reference position of (3) has the lowest patch area factor, which theoretically is approximately 12.5% (=100/8). However, depending on the accuracy of the individual apparatus or changes in the printing medium caused by the environment and the like, the amount of paper conveyance corresponding to the instruction pulse value can differ from its theoretical value. In that case, the patch area factor will exceed 12.5%.
Incidentally, the adjustment pattern of “−3” and adjustment pattern of “+3” in
It is also preferable to use function approximation such as shown by the curve in
<Adjustment Patch Configuration Example 3>
Configuration example 3 is similar to configuration example 2, but the number of divisions of nozzles which record adjustment patterns is increased to further increase adjustment resolution. In the following example, the nozzles are divided into eight parts.
Consequently, if the deviation in the amount of conveyance is constant on a per-sheet basis, white noise components are averaged and reduced, improving the S/N ratio. Thus, adjustment accuracy of the eight-part split patterns can be higher than that of the two-part split patterns. Suppose, there is a deviation equivalent to one pulse in relation to an instruction pulse value of 1280 (=5120/4). In the case of two-part split, the patches are subjected to a deviation equivalent to four pulses. In the case of eight-part split, the patches are subjected to a deviation equivalent to seven pulses. That is, the eight-part split has a larger impact on the patches.
Furthermore, in the case of eight-part split, the amount of conveyance per stroke is approximately 3.4 mm, making it possible to take 14 measurements per rotation of the roller. Thus, by using the average value of the 14 measurements as the amount of paper conveyance, it is possible to calculate the amount of paper conveyance more stably.
<Flow of Deriving Average Amount of Conveyance and Instruction Pulse Value>
In Step S1601, an adjustment patch is formed at a first position (phase) of the conveying roller. That is, a reference pattern (first pattern) is formed using upstream nozzles and an adjustment pattern (second pattern) is formed using downstream nozzles.
In Step S1602, the amount of dot displacement at the first position (phase) is derived by measuring the adjustment patch formed in Step S1601. Details have been described in “Adjustment patch configuration example 2” and will be omitted here.
In Step S1603, the conveying roller is rotated by a half turn (180 degrees) from the position (phase) at which the reference pattern (first pattern) has been formed in Step S1601. Incidentally, the rotation angle of the conveying roller can be detected with much higher accuracy than the amount of dot displacement using an encoder (not shown) mounted on the conveying roller.
In Step S1604, an adjustment patch is formed at a second position (phase) of the conveying roller. That is, a reference pattern (first pattern) is formed using upstream nozzles and an adjustment pattern (second pattern) is formed using downstream nozzles.
In Step S1605, the amount of dot displacement at the second position (phase) is derived by measuring the adjustment patch formed in Step S1604. Details have been described in “Adjustment patch configuration example 2” and will be omitted here.
In Step S1606, an instruction pulse value corresponding to an average amount of conveyance is derived. That is, an average amount of displacement is calculated from the amount of dot displacement at the first position (phase) and amount of dot displacement at the second position (phase). Then, a correct instruction pulse value (5122 in this case) is calculated from a pulse adjustment value (e.g., +2) corresponding to the average amount of displacement and a theoretical instruction pulse value (e.g., 5120). The calculated correct instruction pulse value as the rotational amount of the conveyance roller during conveyance of the printing medium executed after print scanning in image formation is set, and the conveyance roller is driven based on the set pulse value. By driving the conveyance roller in this manner, the conveyance shift amount of a fixed component resulting from a full rotation of the conveyance roller is absorbed, enabling image formation with low density unevenness.
As described above, the average amount of displacement is derived from the amount of displacement at two positions (phases) of the conveying roller. The use of the average amount of displacement makes it possible to derive an almost constant correction value regardless of the timing of adjustment operation. By driving the conveying roller using the correction value thus derived, it is possible to reduce misregistration in the conveying direction of the printing medium.
In the above description, assuming that the variable component (B in
Also, the friction and amount of slippage between the conveyance roller and the printing medium differs depending on the type of printing medium. For this reason, by setting the amount of rotation of the roller for each type of printing medium, the average conveyance amount can be calculated with even higher accuracy.
A method for reducing the fixed component by deriving the average amount of conveyance has been described in the first embodiment. However, eccentricity of the conveying roller or the like can cause degradation of recorded images as shown in
<Variable Component Due to Eccentricity>
It is known, for example, that the variable component (B in
<Adjustment Patch Configuration Example>
Incidentally, variable components other than sine functions are mainly attributable to paper slippage and the like as described above. It is known that the paper slippage and the like can be regarded as white noise (random noise). Therefore, with increases in the amount of conveyance, the variable components other than sine functions are averaged and noise is reduced relatively. That is, the S/N ratio is increased. However, simply increasing the amount of conveyance increases the amount (length) of the printing medium needed for registration adjustment. Thus, description will be given below of a method for reducing the variable components other than sine functions while curbing increases in consumption of the printing medium.
Actually, the white noise component described above is superimposed on the measured values in the A-B, A-H, and B-H intervals. However, the amounts of conveyance in the A-B, A-H, and B-H intervals are approximately 3.4 mm, 23.7 mm, and 20.3 mm, respectively. Consequently, the noise level in the A-H interval is an average (integration) of seven measurements taken in the A-B interval while the noise level in the B-H interval is an average of six measurements taken in the A-B interval. Thus, it can be seen that the amount of displacement can be detected more accurately if the difference between the A-H interval and B-H interval is used as measurement data in the A-B interval instead of using data obtained by direct measurement in the A-B interval. This method makes it possible to derive accurate adjustment values for the instruction pulse value without increasing the amount of recording in the paper conveying direction.
<Modeling of Variable Components>
The method described above makes it possible obtain the amount of displacement for each stroke of paper conveyance (approximately 3.4 mm). Therefore, by repeating measurements 14 (=47/3.4) times, it is possible to obtain the amount of displacement in each phase during one rotation of the conveying roller, and thereby derive an adjustment value for the instruction pulse value.
Incidentally, as described above, it is known that the variable component attributable to displacement (eccentricity) in the mounting position of the roller support member is equal in period to one rotation of the roller and has the same effect in the positive and negative directions. Thus, the variable component can be modeled (approximated) using a sine function, making it possible to derive more accurate adjustment values for the instruction pulse value. Also, the sine function can be determined uniquely using four or more measurement points (amounts of displacement) during one rotation of the conveying roller, making it possible to speed up adjustment operation.
In Step S2101, an adjustment patch is formed. That is, a reference pattern (first pattern) is formed using upstream nozzles and an adjustment pattern (second pattern) is formed using downstream nozzles.
In Step S2102, the amount of dot displacement at the position (phase) of formation of the adjustment patch is derived by measuring the adjustment patch formed in Step S2101. Details have been described in the first embodiment and will be omitted here.
In Step S2103, the conveying roller is rotated by a predetermined angle from the position (phase) at which the reference pattern (first pattern) has been formed in Step S2101. For example, it is rotated here by a ¼ turn (approximately 11.8 mm). Incidentally, the rotation angle of the conveying roller can be detected with much higher accuracy than the amount of dot displacement using an encoder (not shown) mounted on the conveying roller.
In Step S2104, it is checked whether amounts of displacement have been acquired at four or more positions (phases) during one rotation of the conveying roller. If yes, the flow goes to Step S2105. Otherwise flow returns to Step S2101.
In Step S2105, modeling (function approximation) is performed based on the amounts of displacement derived at the positions (phases) of the conveying roller in Steps S2101 to S2104. In the presence of eccentricity and the like, it is preferable to express the amounts of displacement in terms of a sine function with a period equal to one rotation of the conveying roller.
In Step S2106, a correct instruction pulse value for each phase of the conveying roller is derived using the function modeled in Step S2105. That is, the correct instruction pulse values for the phases of the conveying roller detected by the encoder are derived from the function.
By controlling the conveying roller based on the instruction pulse values thus derived, it is possible to reduce misregistration in the conveying direction of the printing medium. The second embodiment, in particular, can reduce displacement within one rotation of the conveying roller.
As a method for acquiring the conveyance amount for each phase angle of a rotation of the conveyance roller other than the embodiments mentioned above, the following method can also be used.
Moreover, because the nozzle-space distance and accuracy of the print head necessary for the method to acquire the conveyance amount of the present embodiment are regulated by the print head creation process, known values are used. In particular, the present method uses a nozzle-space distance to acquire an amount of misalignment of the conveyance amount.
First, as shown in
Next, the distance between the two straight lines formed on the printing medium is measured using an optical sensor attached to the carriage.
By printing the two straight lines shown in
Moreover, while nozzles 1 through 9 are used in the explanation above, the numbers are not restricted, and any nozzles can be used. When selecting the nozzles to be used to print the straight line in the present embodiment, it is preferable to select nozzles with a distance similar to the conveyance amount during actual printing.
Also, when the light-emission unit (
For this reason, the thickness of the printed line must be approximately ¼ the size of the sensor aperture unit. In other words, a sensor with an aperture unit that is approximately 4 times the printed straight line must be used. This means that when the line is formed with a width of 100 μm, the aperture unit must be 400 μm, and a sensor with even higher accuracy is necessary for length measurement.
In this way, by using the method described above, the shift in conveyance amount corresponding to a position of one revolution of a conveyance roller can be acquired. As in the first embodiment, by detecting the conveyance amount at two or more positions on the conveyance roller, the fixed components of the roller rotation such as type of printing medium and environment can be acquired, and a conveyance amount corresponding to the printing medium that decreases the effect of these fixed components can be acquired.
As shown above, the present invention has a characteristic not of depending on a method for acquiring a conveyance amount, but of realizing paper medium conveyance amount adjustment that reduces the effect of shift components due to a revolution of the conveyance roller. According to the present invention, an error component during acquisition of conveyance amount due to a conveyance roller shift is acquired by an operation of rotating a roller less than one revolution can be acquired, and execution of conveyance control which decreases an error component is possible.
Also, when rotating a conveyance roller over more than one revolution in acquiring a conveyance amount or a conveyance error, the amount of consumed printing medium and time for acquisition increase by the amount of the conveyance roller rotation. However, in the present invention, because a conveyance amount or conveyance error is acquired with a rotation amount of a rotation roller in less than one revolution, the consumed amount of printing medium and time for acquisition is reduced. Moreover, although a conveyance amount of the printing medium with respect to a predetermined rotation amount is acquired by a plurality of roller revolutions, even if rotation of a conveyance roller or a conveyance amount acquisition operation in less than one rotation is executed a plurality of times, the overall rotation amount of the conveyance roller is still less than one revolution. For this reason, the amount of printing medium required for the conveyance amount acquisition operation is shorter than the circumference of the conveyance roller, and can be reduced to significantly less than the amount of printing medium required for conventional conveyance amount correction.
Moreover, by rotating a conveyance roller by less than one revolution, regarding position determination of a plurality of sampling points when acquiring conveyance amount, it is desirable to divide the circumference of the conveyance roller by a constant number and acquire the positions. For example, if the conveyance amount is to be acquired with 8 sampling points, the conveyance amount is acquired at positions A-H as shown in
Also, although a composition in which the conveyance amount is acquired using a plurality of points was described, the conveyance amount must be acquired using a minimum of 2 sampling points, and in this case it is preferable to acquire the conveyance amount using 2 points positioned 180° from each other on the roller. Normally, because the shape of the conveyance roller becomes close to an oval shape, the shift component can be reduced in most cases by acquiring the conveyance amount using 2 sampling points offset 180° from each other.
Embodiments of the present invention have been described in detail above, but the present invention may be applied either to a system consisting of two or more devices or to an apparatus consisting of a single device. For example, the present invention may take the form of an image output terminal of an information processing apparatus such as a computer installed either integrally or separately, a copying machine combined with a reader or the like, or a facsimile machine equipped with transmission and reception capabilities.
Incidentally, the present invention can also be achieved by a configuration in which a software program that implements the functions of the embodiments described above is supplied to a system or apparatus either directly or remotely and a computer in the system or apparatus reads out and executes the supplied program code. Thus, program code itself installed on the computer to implement functions and processes of the present invention on the computer also implements the present invention.
In that case, the program code may take any form including object code, programs executed by an interpreter, and script data supplied to an OS as long as it has program functions.
Recording media available for use to supply programs include, for example, floppy (registered trademark) disks, hard disks, optical disks (CD and DVD), magneto-optical disks, MO disks, magnetic tapes, and non-volatile memories.
The functions of the above embodiments may be implemented not only by the program read out and executed by the computer, but also by part or all of the actual processing executed, in accordance with instructions from the program, by an OS running on the computer.
Furthermore, the functions of the above embodiments may also be implemented by part or all of the actual processing executed by a CPU or the like contained in a function expansion board inserted in the computer or a function expansion unit connected to the computer if the processing is performed in accordance with instructions from the program code that has been read out of the storage medium and written into memory on the function expansion board or unit.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2006-056899, filed Mar. 2, 2006, and Japanese Patent Application No. 2007-047886, filed Feb. 27, 2007, which are hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
---|---|---|---|
2006-056899 | Mar 2006 | JP | national |
2007-047886 | Feb 2007 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2007/053755 | 2/28/2007 | WO | 00 | 11/21/2008 |