# US 5,349,375 A · Ink jet printer dot placement compensation method

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- Number: US 5,349,375 A
- Document ID: US5349375A
- Status: Granted
- Kind: A
- Application number: 07/870,449
- Filed: 1992-04-16
- Granted: 1994-09-20
- Earliest claimed: 1992-04-16
- Assignees: Lexmark International, Inc.
- Inventors: John P. Bolash; Edmund H. James, III; Randall D. Mayo; Richard G. Zumbach
- Web page: https://patentgrep.com/patent/US5349375A

## CPC

- B41J 2/5056: {using dot arrays providing selective dot disposition modes, e.g. different dot densities for high speed and high-quality printing, array line selections for multi-pass printing, or dot shifts for character inclination (B41J2/2132 takes precedence)}
- B41J 11/42: Controlling {printing material conveyance for accurate alignment of the printing material with the printhead; Print registering}
- B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS

## Abstract

In a printer having P+X printing elements for printing pixels with a vertical center-to-center spacing R.sub.1 during a plurality of line scans, and a stepper motor for moving a record medium in increments R.sub.2 where R.sub.2 is greater than R.sub.1, all points addressable printing is obtained by a combination of movement of the record medium orthogonal to the line scan direction and shifting address signals applied to the print elements. The stepper motor moves the record medium a distance k.sub.2 R.sub.2 between successive line scans and address signals are applied to (n+k.sub.1)th . . . (n+k.sub.1 +P-1)th print elements to cause a shift k.sub.1 R.sub.1 such that the sum of the distance the record medium is moved before a line scan and the shift caused by the address signals during a scan is equal to PR.sub.1 where P is the number of print elements active during the preceding line scan, or equal to any desired integral multiple of R.sub.1 in other print modes. With a print head capable of printing pixels on 1/300 inch centers, and a stepper motor capable of moving the record medium in minimum increments of 1/150 inch, all points addressable printing with a pixel resolution of 1/300 inch is achieved with increased accuracy. This same arrangement also permits printing in the character mode with a line-to-line spacing of exactly 1/6 inch. In a second embodiment the line-to-line spacing differs from 1/2 inch by a distance that has minimal impact on print quality.

## Claims

### Claim 1

A method of operating a printer mechanism having a print head for printing pixels on a record medium during a plurality of line scans as said print head is moved along an axis relative to said record medium, and a stepper motor for moving said record medium in a direction orthogonal to said axis, said print head having print elements 1,2, . . . P,(P+1) . . . (P+X) responsive to selectively applied address signals 1, 2, . . . P for selectively printing pixels at adjacent pixel positions aligned in the direction of record medium movement with a distance R.sub.1 between centers of adjacent pixel positions, and said stepper motor being responsive to energizing pulses for moving said record medium by a minimum distance R.sub.2 where R.sub.2 is greater than R.sub.1, said method comprising the steps of:
during a given one of said line scans, applying the address signals 1, 2, . . . P to said print elements (n), (n+1), . . . (n+P-1) whereby no more than P of said print elements print pixels during said given one of said line scans, n being a positive integer from 1 to X;
after said given one of said line scans, applying pulses to the stepper motor to move the record medium a distance k.sub.2 R.sub.2 ; and,
during another of the line scans following said movement of the record medium by said distance k.sub.2 R.sub.2, applying the address signals 1, 2, . . . P to said print elements (1+k.sub.1),(2+k.sub.1) . . . (P+k.sub.1) whereby pixels are printed with a shift of k.sub.1 R.sub.1 in a direction parallel to the direction the record medium is moved,
where k.sub.2, P and X are positive integers and k.sub.1 is an integer no less than 0 and k.sub.1 R.sub.1 +k.sub.2 R.sub.2 =PR.sub.1.

### Claim 2

A method of operating a printer mechanism to obtain all points addressable printing of pixels over plural line scans with the center-to center distance between all pixel print positions in the director of record movement being exactly R.sub.1, said printer mechanism having a print head for printing pixels on a record medium during a plurality of line scans as said print head is moved along an axis relative to said record medium, and a stepper motor for moving said record medium in a direction orthogonal to said axis, said print head having print elements 1,2, . . . P,(P+1) . . . (P+X) responsive to selectively applied address signals 1, 2, . . . P for selectively printing pixels at adjacent pixel positions aligned in the direction of record medium movement with a distance R.sub.1 between centers of adjacent pixel positions, and said stepper motor being responsive to energizing pulses for moving said record medium by a minimum distance R.sub.2 where R.sub.2 is greater than R.sub.1, said method comprising the following steps:
step 1) during each of said line scans, applying the address signals 1, 2, . . . P to said print elements (1+k.sub.1),(2+k.sub.1), . . . (P+k.sub.1) whereby pixels are printed with a shift distance of k.sub.1 R.sub.1 relative to where pixels would have been printed if said signals had been applied to said print elements 1, 2, . . . P, respectively, the shift distance being in a direction parallel to the direction the record medium is moved, k.sub.1 being an integer from 0 to X;
step 2) between successive ones of said line scans, applying a number of pulses to the stepper motor to move the record medium a distance k.sub.2 R.sub.2, and,
step 3) repeatedly carrying out step 1 and step 2 while applying said address signals to different ones of said print elements to vary said shift distance k.sub.1 R.sub.1, and while varying the number of pulses applied to said stepper motor so that a sum of the distance k.sub.2 R.sub.2 that the record medium is moved when a given step 2 is carried out and the shift distance k.sub.1 R.sub.1 that the pixels are printed during a step 1 next succeeding said given step 2 is equal to PR.sub.1, k.sub.2, P and X being positive integers.

### Claim 3 (depends on 2)

The method as claimed in claim 2 wherein k.sub.1, on succeeding executions of step 1, has cyclically repeating values of 0,2,4,6,0 . . . during successive ones of said line scans.

### Claim 4 (depends on 2)

The method as claimed in claim 2 wherein PR.sub.1 =1/6 inch.

### Claim 5 (depends on 2)

The method as claimed in claim 2 wherein R.sub.1 =1/300 inch and R.sub.2 =1/75 inch.

### Claim 6 (depends on 2)

The method as claimed in claim 2 wherein R.sub.1 =1/300 inch and R.sub.2 =1/150 inch.

### Claim 7 (depends on 2)

The method as claimed in claim 2 wherein pulses are applied in pairs to said stepper motor, each of said pulses energizing said stepper motor to move said record medium 1/150 inch.

### Claim 8 (depends on 2)

The method as claimed in claim 2 wherein said stepper motor has a number of phases and k.sub.2 is a multiple of a positive integer m, where m represents a number of stepper motor pulses and is evenly divisible by a number representing the number of phases of said stepper motor.

### Claim 9

A method of operating a printer mechanism having a print head for printing pixels on a record medium during a plurality of line scans as said print head is moved along an axis relative to said record medium, and a stepper motor for moving said record medium in a direction orthogonal to said axis, said print head having a plurality of print elements 1,2 . . . P,(P+1) . . . (P+X) responsive to selectively applied address signals 1, 2, . . . P for selectively printing pixels at adjacent pixel positions aligned in the direction of record medium movement with a distance R.sub.1 between centers of adjacent pixel positions, and said stepper motor being responsive to energizing pulses for moving said record medium by a minimum distance R.sub.2 where R.sub.2 is greater than R.sub.1, said method comprising the following steps:
step 1) during a given one of said line scans, applying the address signals 1, 2, . . . P to said print elements (1+k.sub.1), (2+k.sub.1) . . . (P+k.sub.1) whereby said print elements print pixels which are shifted by a shift distance k.sub.1 R.sub.1 relative to where pixels would have been printed if said addressing signals had been applied to said print elements 1,2, . . . P, respectively, the shift distance being parallel to the direction the record medium is moved and k.sub.1 being zero or a positive integer no greater than X;
step 2) between successive ones of said line scans, applying pulses to the stepper motor to move the record medium a distance k.sub.2 R.sub.2 ; and,
step 3) repeatedly executing step 1 and step 2 while applying said address signals to different ones of said print elements to vary said shift distance k.sub.1 R.sub.1 and while varying the number of pulses applied to said stepper motor so that a sum of the distance k.sub.2 R.sub.2 that the record medium is moved when step 2 is executed and the shift distance k.sub.1 R.sub.1 that the pixels are printed during a next succeeding execution of step 1 differs from PR.sub.1 by no more than one-half R.sub.1, k.sub.2, P and X being positive integers.

### Claim 10 (depends on 9)

The method as claimed in claim 9 wherein k.sub.1, on succeeding executions of step 1, has cyclically repeating values of 0,2,4,6,0, . . . during successive ones of said line scans.

### Claim 11 (depends on 9)

The method as claimed in claim 9 wherein PR.sub.1 =1/6 inch.

### Claim 12 (depends on 9)

The method as claimed in claim 9 wherein R.sub.1 =1/300 inch and R.sub.2 =1/75 inch.

### Claim 13 (depends on 12)

The method as claimed in claim 12 wherein pulses are applied in pairs to said stepper motor, each of said pulses energizing said stepper motor to move said record medium 1/150 inch.

### Claim 14 (depends on 9)

The method as claimed in claim 9 wherein R.sub.1 =1/300 inch and R.sub.2 =1/150 inch.

### Claim 15 (depends on 9)

The method as claimed in claim 9 wherein PR.sub.1 +k.sub.1 R.sub.1 is approximately 1/8 inch.

### Claim 16 (depends on 9)

The method as claimed in claim 9 wherein P and less than P address signals are applied to said print elements on a first and succeeding alternate ones of said line scans and the second and succeeding alternate ones of said line scans, respectively.

### Claim 17 (depends on 9)

The method as claimed in claim 9 wherein k.sub.2 is 8, 9 or 10.

### Claim 18 (depends on 9)

The method as claimed in claim 9 wherein said stepper motor has a number of phases and k.sub.2 is a multiple of a positive integer m, where m represents a number of stepper motor pulses and is evenly divisible by a number representing the number of phases of said stepper motor.