# Patent

## Title
Method for reducing banding in an imaging apparatus

## Abstract

A method for reducing banding during printing with an imaging apparatus includes establishing a current original move length; determining a current original absolute position; calculating a current adjusted absolute position based on the current original absolute position; determining a current difference between the current original absolute position and the current adjusted absolute position; determining a current move-to-move adjustment amount by subtracting the current difference from a previous difference between a previous original absolute position and a previous adjusted absolute position; and generating an adjusted move length for a next move by adding the current move-to-move adjustment amount to the current original move length.

## Background
CROSS REFERENCES TO RELATED APPLICATIONS
None.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
None.
REFERENCE TO SEQUENTIAL LISTING, ETC.
None.
BACKGROUND
1. Field of the Invention
The present invention relates to an imaging apparatus, and, more particularly, to a method for reducing banding during printing with an imaging apparatus.
2. Description of the Related Art
In prior art, a typical ink jet printer forms an image on a print medium by ejecting ink from at least one ink jet printhead to form a pattern of ink dots on the print medium. Such an ink jet printer includes a reciprocating printhead carrier that transports one or more ink jet printheads across the print medium along a bi-directional scanning path defining a print zone of the printer. The bi-directional scanning path is oriented parallel to a main scan direction, also commonly referred to as the horizontal direction. The main scan direction is bi-directional. During each scan of the printhead carrier, the print medium is held stationary. An indexing mechanism is used to incrementally advance the print medium in a sheet feed direction, also commonly referred to as a sub-scan direction or vertical direction, through the print zone between scans in the main scan direction, or after all data intended to be printed with the print medium at a particular stationary position has been completed.
For a given stationary position of the print medium, printing may take place during one or more unidirectional scans of the printhead carrier. As used herein, the term “unidirectional” is used to refer to scanning in either, but only one, of the two bi-directional scanning directions. Thus, bi-directional scanning refers to two successive unidirectional scans in opposite directions. The term “printing swath” typically refers to the depositing of ink on the print medium during a particular unidirectional scan of the printhead carrier at which time individual printhead nozzles of the printhead are selectively actuated to expel ink. A printing swath is made of a plurality of printing lines traced along imaginary rasters, the imaginary rasters being spaced apart in the sheet feed direction.
Typically, each ink jet printhead will include a plurality of ink jet nozzles arranged in one or more substantially vertical columns for expelling the ink. In ink jet printing, it is common to use the ink colors of cyan, magenta, yellow and black in generating color prints. Also, it is common in ink jet printing to have a printhead having a dedicated nozzle array for each of cyan, magenta and yellow inks, respectively, wherein the three nozzle arrays are aligned vertically, that is, aligned in a direction parallel to the sub-scan direction.
Those working in the imaging arts continually strive to improve the print quality of imaging devices, such as ink jet printers. One such attempt is directed to reducing the occurrence of horizontal banding defects in printouts generated by an ink jet printer. Horizontal banding defects may be observed on media, such as paper, as a horizontal white or a horizontal dark band. Such defects are generally attributable to errors generated by the media sheet indexing mechanism that is used to advance a media sheet in a media feed direction through the printer during the printing of the text or image on the media sheet. Such errors can be caused, for example, by mechanical tolerances of the index roller and its associated drive train. Contributing to this error are variations in the print swath height caused by variations in the height of the printhead. It is known to attempt to mask such indexing errors by adopting an interlaced printing method, also referred to. as shingling, wherein each scan of the printhead carrier (also sometimes referred to in the art as a printhead carriage) is made to vertically overlap a preceding scan. For a given swath, only a portion of the total print data for a given area on the print medium is printed. Thus, each scan of an actuated printhead produces a swath of printed output forming all or portions of multiple print lines, and multiple swaths may be required to complete the printing of any given print line. In some applications, however, such masking techniques may not be adequate to achieve the desired print quality.
SUMMARY OF THE INVENTION
The invention, in one form thereof, is directed to a method for reducing banding during printing with an imaging apparatus. The method includes establishing a current original move length; determining a current original absolute position; calculating a current adjusted absolute position based on the current original absolute position; determining a current difference between the current original absolute position and the current adjusted absolute position; determining a current move-to-move adjustment amount by subtracting the current difference from a previous difference between a previous original absolute position and a previous adjusted absolute position; and generating an adjusted move length for a next move by adding the current move-to-move adjustment amount to the current original move length.
The invention, in another form thereof, is directed to a method to change the feed rate of a printer, including applying discrete adjustments to at least some of all of a plurality of print moves such that the same total move correction is applied over any arbitrarily chosen effective printhead height in an image.
The motivation for the methods of the present invention can be understood by considering the implication of a paper feed mechanism that feeds the paper slightly less than the desired amount. The effect of this in a shingled mode is that the nozzle that should print on a given raster ends up short of the location of the first nozzle that printed on that raster. Eventually the error can become large enough that the nozzle will actually print in the wrong raster. This deviation after each move is very small and often too small to correct by making a correction to the length of the paper feed move. However, once the error builds up to the smallest paper feed move increment, then one increment can be added. This keeps the error in the paper feed direction to about the size of the smallest paper feed increment. Thus, there may be several moves per correction, wherein some moves receive correction and some moves do not receive correction.



BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a diagrammatic representation of an imaging apparatus embodying the present invention; and
FIG. 2 is a flowchart of a method for reducing banding during printing with an imaging apparatus, in accordance with an embodiment of the present invention.



DETAILED DESCRIPTION
It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.
In addition, it should be understood that embodiments of the invention include both hardware and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one embodiment, the electronic based aspects of the invention may be implemented in software. As such, it should be noted that a plurality of hardware and software-based devices, as well as a plurality of different structural components may be utilized to implement the invention. Furthermore, and as described in subsequent paragraphs, the specific mechanical configurations illustrated in the drawings are intended to exemplify embodiments of the invention and that other alternative mechanical configurations are possible.
Referring to FIG. 1, there is shown a diagrammatic representation of an imaging apparatus 10 embodying the present invention. Imaging apparatus 10 includes a controller 12, print engine 14, a power drive apparatus 16, a media transport system 18, a media supply tray 20 and a media exit tray 22. Controller 12 is communicatively coupled to each of power drive apparatus 16 and print engine 14 via a communications link 24.
As used herein, the term “communications link” generally refers to structure that facilitates electronic communication between two or more components, and may operate using wired or wireless technology. Accordingly, communications link 24 may be, for example, one of, or a combination of, a bus structure, a direct electrical wired connection, a direct wireless connection (e.g., infrared or radio frequency (r.f.)), or a network connection (wired or wireless), such as for example, an Ethernet local area network (LAN) or a wireless networking standard, such as IEEE 802.11.
In one embodiment, for example, imaging apparatus 10 may be a printer, such as for example an ink jet printer utilizing an ink jet print engine as print engine 14. In another embodiment, for example, imaging apparatus 10 may be an all-in-one (AIO) machine having printing and copying functionality in addition to scanning functionality, although in the embodiment shown in FIG. 1, a scanning device for supporting the scanning functionality is not shown. In the ink jet embodiments, print engine 14 may include a reciprocating printhead carrier that carries one or more ink jet printheads 25 in a main scan direction substantially perpendicular to a media feed direction 32, and which is operated under the control of controller 12.
As is known in the art, each ink jet printhead may include a columnar array of ink jetting nozzles. In one embodiment of such a printhead, for example, the ink jet printhead may have a columnar array of 160 nozzles having an effective nominal printhead height (H), i.e., a distance between the first nozzle and the last nozzle used in the array, of 160/600ths of an inch. In another embodiment, for example, not all of the nozzles are used, e.g., 152 nozzles, resulting in an effective nominal printhead height (H) of 152/600ths of an inch. Those skilled in the art will recognize that the number of nozzles and the effective printhead nominal height (H) may be increased or decreased from the examples described above.
Controller 12 may be, for example, an application specific integrated circuit (ASIC) having programmed and/or programmable processing capabilities. Controller 12 may include, for example, semiconductor memory, such as for example, random access memory (RAM), read only memory (ROM), and/or non-volatile RAM (NVRAM). Controller 12 may include in its memory a software or firmware program including program instructions that function as a driver for print engine 14. Accordingly, the driver, as a software or firmware program, executed by controller 12 may include a printer driver that places print data and print commands in a format that can be recognized by print engine 14.
Power drive apparatus 16 and media transport system 18 are used to transport a media sheet 26, such as a paper, transparencies, etc., from the stack of media sheets 28 held in media supply tray 20, to, through and from an imaging area 30 of print engine 14 to media exit tray 22 in media feed direction 32.
Media transport system 18 includes a sheet picking device 34 having a pick roller 36; a feed roller set 38 and corresponding pinch roller set 40; and an exit roller set 42 and corresponding backup roller set 44. Power drive apparatus 16 is drivably coupled via a transmission device 46, diagrammatically illustrated by interconnected lines, to each of sheet picking device 34, feed roller set 38 and exit roller set 42.
Power drive apparatus 16 may include as a power source a motor, such as a direct current (DC) motor or a stepper motor. Transmission device 46 may be, for example, a set of gears and/or belts, and clutches configured to transmit a rotational force to the respective rollers at the appropriate time, in conjunction with commands supplied to power drive apparatus 16 from controller 12. Feed roller set 38 and exit roller set 42 may be drivably coupled together, for example, via a pulley/belt system or a gear train. A position of the sheet of media 26 in relation to printhead 25 may be determined and maintained as a cumulative absolute position, based for example, on counting steps moved by the stepper motor in embodiments where such a power source is used.
In the embodiment shown, media supply tray 20 combines with print engine 14 to define a media path 48, which in this embodiment defines an L-shaped media path through imaging apparatus 10. It is contemplated, however, that media supply tray 20 may be of other configurations, such as wherein media supply tray 20 is oriented substantially horizontally, such that media path 48 is defined as a substantially flat media path through imaging apparatus 10. As a further alternative, media supply tray 20 may be connected via a C-shaped paper path having additional rollers.
Sheet picking device 34 is configured to automatically pick a media sheet, such as media sheet 26, from the stack of media sheets 28 located in media supply tray 20, and is sometimes implemented in the art by a mechanism commonly referred to as an auto compensator pick device. Sheet picking device 34 includes a pick arm 50 containing a plurality of gears that are drivingly coupled to sheet pick roller 36. Further, sheet pick roller 36 is positioned by pick arm 50 to contact the top media sheet in the stack of media sheets 28 in media supply tray 20. The picked sheet is conveyed in media feed direction 32 to feed 10 roller set 38, which under the control of controller 12, incrementally feeds the picked sheet of media, e.g., the sheet of media 26, in an indexed fashion during printing.
FIG. 2 is a flowchart of a method for reducing banding during printing with an imaging apparatus, such as imaging apparatus 10, wherein imaging apparatus 10 currently has a media underfeed that results in dark bands being present in the printed image. The method may be implemented, for example, by program instructions executed by the processor of controller 12 of imaging apparatus 10, or alternatively, by a processor of a host computer (not shown) communicatively coupled to imaging apparatus 10, and may include the printer driver, in whole or in part.
In the examples that follow, it has been determined to increase the media feed per effective printhead height by 3/2400ths of an inch for plain paper and 4/2400ths of an inch for glossy paper, resulting in an overall federate increase of 0.47% and 0.63%, respectively. The increase of effective media feed rate for glossy paper is larger than for plain paper, for example, due to increased media slippage in feed roller set 38 associated with the glossy surface of the glossy paper. Those skilled in the art will recognize that the increase in effective feed rate may be increased or decreased from these exemplary increases. Various results are demonstrated in the spreadsheets included in Appendices A, B, C, D, E, and F that follow this section. Another advantage is the ability to change the feed rate as required.
At step S100, a current original move length, i.e., for the next print media move, is established. The original move length may change during the printing of the page. For example, in one embodiment for printing plain paper with a full head height, the original move length from one move to the next may alternate between 158/1200ths of an inch and 162/1200ths of an inch (i.e., 1264/9600ths of an inch and 1296/9600ths of an inch), as illustrated for example in Appendix A. In another embodiment for edge-to-edge printing using one-half the printhead height, for example, the sequential moves, in 1/1200ths of an inch, may be a repeating pattern of [50, 158, 50, 50], as illustrated for example in Appendix C. Those skilled in the art will recognize that other patterns of sequential original moves may be established, for example, depending on the number of printing swaths used to complete printing of a particular print line.
At step S102, a current original absolute position is determined. Assume, for example, that the original absolute position for the first printing pass is zero (0), then, for plain paper where the original move lengths are established to alternate between 1264/9600ths of an inch and 1296/9600ths of an inch, the sequence of original absolute positions, in 9600ths, are 1264, 2560, 3824, 5120, 6384, etc., as illustrated in Appendix A.
At step S104, a current adjusted absolute position is calculated based on the current original absolute position. The following exemplary equation may be used in performing this calculation:

AdjAbsPos=int((3*OrigAbsPos+Divisor/2)/Divisor)+OrigAbsPos

wherein:

    
    
        AdjAbsPos is the current adjusted absolute position;
        int is a function performing real number truncation to form an integer;
        OrigAbsPos is the current original absolute position; and
        Divisor is an established constant that is based on an effective printhead height.
    
    


The Divisor is chosen such that for any effective printhead height group of moves, the same amount of correction is applied. This is to insure that the increase is evenly spread down the page. For example, if the effective printhead height is 160/2400ths of an inch, i.e., 640/9600ths of an inch, where the standard is to use 9600ths of an inch, then the Divisor in this example will be 640 and the original absolute position for the first move is 1264. Accordingly, based on the equation above the adjusted absolute position is 1270, as illustrated in Appendix A. For the next move, the Divisor is again 640, the original absolute position is 2560, and the adjusted absolute position is 2572, etc.
Table I, below, shows an exemplary Divisor that may be used for each of a plurality of particular printing modes, and an associated effective adjusted feed rate. In this example, the print modes include plain paper normal, plain paper normal edge-to-edge (E2E), plain paper normal edge-to-edge (E2E) using one-half printhead height, best using one-half printhead height, best (fall printhead height) and normal glossy.







TABLE I







Exemplary Divisor for Each of a Plurality of Printing Modes











Effective




Adjusted



Divisor
Feed Rate %















Plain Paper Normal
640
0.469



Plain Paper Normal E2E
624
0.481



Plain Paper Normal E2E, 1⁄2 Head
616
0.487



Best 1⁄2 Head
432
0.694



Best
456
0.658



Normal Glossy
468
0.641










At step S106, a current difference between the current original absolute position and the current adjusted absolute position is determined. Thus, for example, as illustrated in Appendix A, the difference between the original absolute position for the first move of 1264 and the adjusted absolute position of 1270 is 6; the difference between the original absolute position for the second move of 2560 and the adjusted absolute position of 2572 is 12, etc., as illustrated in Appendix A.
At step S108, a current move-to-move adjustment amount is determined by subtracting the current difference determined in step S106 from a previous difference, wherein the previous difference is the difference between a previous original absolute position and a previous adjusted absolute position. Thus, referring to Appendix A, the current move-to-move adjustment amount for the first media move after printing has started is the difference between the previous difference of zero (0) and the current difference of 6, which is a current move-to-move adjustment amount of 6, i.e., 6/9600ths; the current move-to-move adjustment amount for the second media move is the difference between the previous difference of 6 and the current difference of 12, which is a current move-to-move adjustment amount of 6, i.e., 6/9600ths; etc.
At step S110, an adjusted move length is generated for a next move by adding the current move-to-move adjustment to the amount to the original move length. For example, as illustrated in Appendix A, if the original move length is 1264 (i.e., 1264/9600ths), then the adjusted move length is 1270 (i.e., 1270/9600ths); if the original move length is 1296 (i.e., 1296/9600ths), then the adjusted move length is 1302 (i.e., 1302/9600ths); etc.
At step S112, it is determined whether all the media moves are completed. If YES, then the process is complete and the page has been completely printed. If NO, then the process returns to step S100. In other words, steps S100-S110 are repeated until all media moves during printing are completed, as illustrated in the example of Appendix A.
Appendices B, C, D, E and F illustrate other examples in using the method described above, demonstrating variations in the effective printhead height, divisor, and/or original move lengths, as indicated in the respective Appendix.
In implementing the present invention, if media transport system 18 is not capable of moving, for example, in 9600ths of an inch increments, such as in the case where the smallest increment of the media transport system is 1/2400ths of an inch, then the move is truncated to a whole 2400ths of an inch, and the remainder is carried over to the next move. For example, if an adjusted move length of 1270/9600ths of an inch is desired, the whole 2400ths move is 317/2400ths (i.e., 1268/9600ths), and thus, 2/9600ths will be carried over and added to the next adjusted move length, e.g., 1302/9600+ 2/9600= 1304/9600(i.e., 326/2400ths).







APPENDIX A







Print Mode: Plain Paper Normal


Print Head Nozzles Used: 160


The divisor is used to determine the change in the original move length to


attain the desired feedrate change while only altering


the feedrate over print-head height by an integer value of 1 (2400ths)


Passes 2


divisor (4*9600ths) = 640


















Difference






Original
Original
Adjusted
between original
Move to Move


Original move
move
Absolute
Absolute
Abs Pos and
adjustment


length
length
Position
Position
adjusted Abs Pos
amount
Adjusted move
Adjusted


(1200ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
length (9600ths)
Feedrate %

















158
1264
1264
1270
6
6
1270
0.46875


162
1296
2560
2572
12
6
1302


158
1264
3824
3842
18
6
1270


162
1296
5120
5144
24
6
1302


158
1264
6384
6414
30
6
1270


162
1296
7680
7716
36
6
1302


158
1264
8944
8986
42
6
1270


162
1296
10240
10288
48
6
1302


158
1264
11504
11558
54
6
1270


162
1296
12800
12860
60
6
1302


158
1264
14064
14130
66
6
1270


162
1296
15360
15432
72
6
1302


158
1264
16624
16702
78
6
1270


162
1296
17920
18004
84
6
1302


158
1264
19184
19274
90
6
1270


162
1296
20480
20576
96
6
1302


158
1264
21744
21846
102
6
1270


162
1296
23040
23148
108
6
1302


158
1264
24304
24418
114
6
1270


162
1296
25600
25720
120
6
1302


158
1264
26864
26990
126
6
1270


162
1296
28160
28292
132
6
1302


158
1264
29424
29562
138
6
1270


162
1296
30720
30864
144
6
1302


158
1264
31984
32134
150
6
1270


162
1296
33280
33436
156
6
1302


158
1264
34544
34706
162
6
1270


162
1296
35840
36008
168
6
1302


158
1264
37104
37278
174
6
1270


162
1296
38400
38580
180
6
1302


158
1264
39664
39850
186
6
1270
















APPENDIX B







Print Mode: Plain Paper Normal E2E


Print Head Nozzles Used: 156


The divisor is used to determine the change in the original move length to


attain the desired feedrate change while only altering


the feedrate over print-head height by an integer value of 1 (2400ths)


Passes 2


divisor (4*9600ths) = 624


















Difference






Original
Original
Adjusted
between original
Move to Move


Original move
move
Absolute
Absolute
Abs Pos and
adjustment


length
length
Position
Position
adjusted Abs Pos
amount
Adjusted move
Adjusted


(1200ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
length (9600ths)
Feedrate %

















154
1232
1232
1238
6
6
1238
0.48076923


158
1264
2496
2508
12
6
1270


154
1232
3728
3746
18
6
1238


158
1264
4992
5016
24
6
1270


154
1232
6224
6254
30
6
1238


158
1264
7488
7524
36
6
1270


154
1232
8720
8762
42
6
1238


158
1264
9984
10032
48
6
1270


154
1232
11216
11270
54
6
1238


158
1264
12480
12540
60
6
1270


154
1232
13712
13778
66
6
1238


158
1264
14976
15048
72
6
1270


154
1232
16208
16286
78
6
1238


158
1264
17472
17556
84
6
1270


154
1232
18704
18794
90
6
1238


158
1254
19968
20064
96
6
1270


154
1232
21200
21302
102
6
1238


158
1264
22464
22572
108
6
1270


154
1232
23696
23810
114
6
1238


158
1264
24960
25080
120
6
1270


154
1232
26192
26318
126
6
1238


158
1264
27456
27588
132
6
1270


154
1232
28688
28826
138
6
1238


158
1264
29952
30096
144
6
1270


154
1232
31184
31334
150
6
1238


158
1264
32448
32604
156
6
1270


154
1232
33680
33842
162
6
1238


158
1264
34944
35112
168
6
1270


154
1232
36176
36350
174
6
1238


158
1264
37440
37620
180
6
1270
















APPENDIX C







Print Mode: 1/2 Head Plain Paper


Normal E2E


Print Head Nozzles Used: 154


The divisor is used to determine the change in the original


move length to attain the desired feedrate change while only altering


the feedrate over print-head height by an integer value of 1 (2400ths)


divisor (4*9600ths) = 616 (3*9600ths) = 616


















Difference






Original
Original
Adjusted
between original


Original


Original move
move
Absolute
Absolute
Abs Pos and
Original move

Absolute


length
length
Position
Position
adjusted Abs
length
Original move
Position


(1200ths)
(9600ths)
(9600ths)
(9600ths)
Pos (9600ths)
(1200ths)
length (9600ths)
(9600ths)

















50
400
400
402
2
50
400
400


158
1264
1664
1672
8
158
1264
1664


50
400
2064
2074
10
50
400
2064


50
400
2464
2476
12
50
400
2464


50
400
2864
2878
14
50
400
2864


158
1264
4128
4148
20
158
1264
4128


50
400
4528
4550
22
50
400
4528


50
400
4928
4952
24
50
400
4928


50
400
5328
5354
26
50
400
5328


158
1264
6592
6624
32
158
1264
6592


50
400
6992
7026
34
50
400
6992


50
400
7392
7428
36
50
400
7392


50
400
7792
7830
38
50
400
7792


158
1264
9056
9100
44
158
1264
9056


50
400
9456
9502
46
50
400
9456


50
400
9856
9904
48
50
400
9856


50
400
10256
10306
50
50
400
10256


158
1264
11520
11576
56
158
1264
11520


50
400
11920
11978
58
50
400
11920


50
400
12320
12380
60
50
400
12320


50
400
12720
12782
62
50
400
12720


158
1264
13984
14052
68
158
1264
13984


50
400
14384
14454
70
50
400
14384


50
400
14784
14856
72
50
400
14784


50
400
15184
15258
74
50
400
15184


158
1264
16448
16528
80
158
1264
16448


50
400
16848
16930
82
50
400
16848


50
400
17248
17332
84
50
400
17248


50
400
17648
17734
86
50
400
17640


158
1264
18912
19004
92
158
1264
18912
















APPENDIX D







Print Mode: 1/2 Head Photo


Print Head Nozzles Used: 144


The divisor is used to determine the change in the original move length


to attain the desired feedrate change while only altering


the feedrate over print-head height by an integer value of 1 (2400ths)


Passes 16


divisor (3*9600ths) = 432


















Difference









between original




Original
Original
Adjusted
Abs Pos and
Move to Move


Original move
move
Absolute
Absolute
adjusted Abs
adjustment


length
length
Position
Position
Pos
amount
Adjusted move
Adjusted


(1200ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
length (9600ths)
Feedrate %

















5
40
40
40
0
0
40
0.69444444


21
168
208
209
1
1
169


5
40
248
250
2
1
41


5
40
288
290
2
0
40


5
40
328
330
2
0
40


21
168
496
499
3
1
169


5
40
536
540
4
1
41


5
40
576
580
4
0
40


5
40
616
620
4
0
40


21
168
784
789
5
1
169


5
40
824
830
6
1
41


5
40
864
870
6
0
40


5
40
904
910
6
0
40


21
168
1072
1079
7
1
169


5
40
1112
1120
8
1
41


5
40
1152
1160
8
0
40


5
40
1192
1200
8
0
40


21
168
1360
1369
9
1
169


5
40
1400
1410
10
1
41


5
40
1440
1450
10
0
40


5
40
1480
1490
10
0
40


21
168
1648
1659
11
1
169


5
40
1688
1700
12
1
41


5
40
1728
1740
12
0
40


5
40
1768
1780
12
0
40


21
168
1936
1949
13
1
169


5
40
1976
1990
14
1
41


5
40
2016
2030
14
0
40


5
40
2056
2070
14
0
40


21
168
2224
2239
15
1
169
















APPENDIX E







Print Mode: Glossy Photo


Print Head Nozzles Used: 152


The divisor is used to determine the change in the original move length


to attain the desired feedrate change while only altering


the feedrate over print-head height by an integer value of 1 (2400ths)


Passes 16


divisor (3*9600ths) = 456


















Difference









between original




Original
Original
Adjusted
Abs Pos and
Move to Move


Original move
move
Absolute
Absolute
adjusted Abs
adjustment


length
length
Position
Position
Pos
amount
Adjusted move
Adjusted


(1200ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
length (9600ths)
Feedrate %

















17
136
136
137
1
1
137
0.65789473


21
168
304
306
2
1
169


17
136
440
443
3
1
137


21
168
608
612
4
1
169


17
136
744
749
5
1
137


21
168
912
918
6
1
169


17
136
1048
1055
7
1
137


21
168
1216
1224
8
1
169


17
136
1352
1361
9
1
137


21
168
1520
1530
10
1
169


17
136
1656
1667
11
1
137


21
168
1824
1836
12
1
169


17
136
1960
1973
13
1
137


21
168
2128
2142
14
1
169


17
136
2264
2279
15
1
137


21
168
2432
2448
16
1
169


17
136
2568
2585
17
1
137


21
168
2736
2754
18
1
169


17
136
2872
2891
19
1
137


21
168
3040
3060
20
1
169


17
136
3176
3197
21
1
137


21
168
3344
3366
22
1
169


17
136
3480
3503
23
1
137


21
168
3648
3672
24
1
169


17
136
3784
3809
25
1
137


21
168
3952
3978
26
1
169


17
136
4088
4115
27
1
137


21
168
4256
4284
28
1
169


17
136
4392
4421
29
1
137


21
168
4560
4590
30
1
169
















APPENDIX F







Print Mode: Glossy Normal


Print Head Nozzles Used: 156


The divisor is used to determine the change in the original move length to attain


the desired feed rate change while only altering


the feed rate over print-head height by an integer value of 1 (2400ths)


Passes 8


divisor (3*9600ths) = 468


















Difference







Original
Adjusted
between original
Move to Move


Original move
Original
Absolute
Absolute
Abs Pos and
adjustment
Adjusted move


length
move length
Position
Position
adjusted Abs Pos
amount
length
Adjusted


(1200ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
(9600ths)
Feed rate %

















37
296
296
298
2
2
298
0.64102564


41
328
624
628
4
2
330


37
296
920
926
6
2
298


41
328
1248
1256
8
2
330


37
296
1544
1554
10
2
298


41
328
1872
1884
12
2
330


37
296
2168
2182
14
2
298


41
328
2496
2512
16
2
330


37
296
2792
2810
18
2
298


41
328
3120
3140
20
2
330


37
296
3416
3438
22
2
298


41
328
3744
3768
24
2
330


37
296
4040
4066
26
2
298


41
328
4368
4396
28
2
330


37
296
4664
4694
30
2
298


41
328
4992
5024
32
2
330


37
296
5288
5322
34
2
298


41
328
5616
5652
36
2
330


37
296
5912
5950
38
2
298


41
328
6240
6280
40
2
330


37
296
6536
6578
42
2
298


41
328
6864
6908
44
2
330


37
296
7160
7206
46
2
298


41
328
7488
7536
48
2
330


37
296
7784
7834
50
2
298


41
328
8112
8164
52
2
330


37
296
8408
8462
54
2
298


41
328
8736
8792
56
2
330


37
296
9032
9090
58
2
298


41
328
9360
9420
60
2
330









The foregoing description of several methods and embodiments of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.

## Claims

1. A method for reducing banding during printing with an imaging apparatus, comprising:
a) establishing a current original move length for a sheet of media;
b) determining a current original absolute position for said sheet of media;
c) calculating a current adjusted absolute position for said sheet of media based on said current original absolute position;
d) determining a current difference between said current original absolute position and said current adjusted absolute position;
e) determining a current move-to-move adjustment amount by subtracting said current difference from a previous difference between a previous original absolute position and a previous adjusted absolute position; and
f) generating an adjusted move length for a next move of said sheet of media by adding said current move-to-move adjustment amount to said current original move length.

2. The method of claim 1, further comprising repeating acts a) through f) until all print moves are completed.

3. The method of claim 1, wherein said current original absolute position and said current adjusted absolute position are cumulative move distances resulting from a series of moves.

4. The method of claim 1, wherein said calculating said current adjusted absolute position based on said current original absolute position is performed by the equation:


AdjAbsPos=int ((3*OrigAbsPos+Divisor/2)/Divisor)+OrigAbsPos, wherein:

AdjAbsPos is said current adjusted absolute position;
int is a function performing real number truncation to form an integer;
OrigAbsPos is said current original absolute position; and
Divisor is an established constant that is based on an effective printhead height.

5. The method of claim 4, wherein said Divisor is chosen such that the adjustment is evenly distributed over essentially any effective printhead height.

6. The method of claim 1, wherein said method is performed via program steps executed by a controller associated with said imaging apparatus.

7. The method of claim 1, wherein said banding is dark horizontal bands.

8. An imaging apparatus having a controller, a print engine, a media transport system, and a power drive apparatus, said power drive apparatus being drivably coupled to said media transport system for supplying a sheet of media to, through and from an imaging area of said print engine, said controller being communicatively coupled to said print engine and said power drive apparatus, said controller executing program instructions for reducing banding during printing with said imaging apparatus, comprising:
a) establishing a current original move length for said sheet of media;
b) determining a current original absolute position for said sheet of media;
c) calculating a current adjusted absolute position for said sheet of media based on said current original absolute position;
d) determining a current difference between said current original absolute position and said current adjusted absolute position;
e) determining a current move-to-move adjustment amount by subtracting said current difference from a previous difference between a previous original absolute position and a previous adjusted absolute position; and
f) generating an adjusted move length for a next move of said sheet of media by adding said current move-to-move adjustment amount to said current original move length.

9. The imaging apparatus of claim 8, further comprising repeating acts a) through f) until all print moves are completed.

10. The imaging apparatus of claim 8, wherein said current original absolute position and said current adjusted absolute position are cumulative move distances resulting from a series of moves.

11. The imaging apparatus of claim 8, wherein said print engine carries a printhead, and said calculating said current adjusted absolute position based on said current original absolute position is performed by the equation:


AdjAbsPos=int (( 3* OrigAbsPos+Divisor/2)/Divisor)+OrigAbsPos, wherein:

AdjAbsPos is said current adjusted absolute position;
int is a function performing real number truncation to form an integer;
OrigAbsPos is said current original absolute position; and  Divisor is an established constant that is based on an effective printhead height.

12. The imaging apparatus of claim 11, wherein said Divisor is chosen such that the adjustment is evenly distributed over essentially any effective printhead height.

13. The imaging apparatus of claim 8, wherein said banding is dark horizontal bands.