JP2791349B2 - Serial printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial printer capable of bidirectional printing.

[0002]

2. Description of the Related Art In a serial printer, a print head is moved in a direction orthogonal to a paper feeding direction so that printing can be performed in both forward and reverse directions.

By the way, in this type of printer, when printing in the forward direction and in the reverse direction due to backlash of the gear mechanism for moving the print head in the direction perpendicular to the paper feed direction or slack of the timing belt, etc. Causes a shift in the printing position.

A technique for coping with this printing position shift is disclosed, for example, in Japanese Patent Publication No. 5-28669.
In this technology, a vertical ruled line is printed in the forward direction, a vertical ruled line following the vertical ruled line is printed in a reverse direction, and the optical sensor is scanned so as to pass over each of the vertical ruled lines. The position of each vertical ruled line is detected by binarizing the output voltage value of the optical sensor to be detected, and the position of each vertical ruled line is compared based on the detected data to calculate the shift amount of the printing position in the forward and reverse directions. , The printing timing in the forward printing and the printing timing in the reverse printing are relatively shifted to correct the shift of the printing position in the normal and reverse directions.

[0005]

However, in the above-mentioned conventional technology, when the print density gradually decreases as in an impact-type printer using an ink ribbon, or when printing is performed on gray or cream color paper other than white. And the like, there is a problem that the fluctuation range of the output voltage of the optical sensor is small, and if the output voltage value of the optical sensor is binarized, the vertical ruled line position cannot be detected, and the deviation of the printing position in the forward and reverse directions cannot be detected. .

Further, in order to correct the deviation of the printing position in the forward and reverse directions with the same high accuracy as the dot width, it is necessary to set the sampling cycle of the output voltage value of the optical sensor to be smaller than the dot width. There is a problem that software such as a circuit and a control circuit is complicated and the cost is high.

According to the present invention, even when the printing density gradually decreases or when a medium of a gray or cream color is used, the deviation of the printing position in the forward and reverse directions can be detected without fail, and the invention is complicated. It is an object of the present invention to obtain a serial printer capable of correcting a deviation of a printing position in a forward / reverse direction with high accuracy without using a complicated software.

[0008]

Means for Solving the Problems The present invention, in the serial printer capable of forward and backward printing, has a large detection range than twice the dot width, forward printing has been positive printing pattern and the positive an optical sensor that outputs a voltage value that varies according been scanned over the test pattern consisting of a reverse printed patterns reverse printed on the direction the print pattern and the same row on the printing density change of the test pattern, the optical sensor Calculating means for calculating the shift amount of the print position in the forward and reverse directions based on the output voltage value and the detection width of the printhead, and printing timing in forward printing and reverse printing in the reverse direction based on the shift amount calculated by the calculating means. Print timing correction means that corrects the print position in both the forward and reverse directions by relatively shifting the print timing of the print direction.
Print pattern is one of the two patterns
The printing unit provided on one side and the scanning method of the optical sensor
Wider in the scanning direction of the optical sensor than the detection width in the direction
The first printing portion and one of the two patterns
Printing section provided in the optical sensor and in the scanning direction of the optical sensor.
First, wider in the scanning direction of the optical sensor than the detection width in
A second printing portion that generates a non-printing portion of
Printing part provided in one of the
A second non-printing portion having a predetermined width in the scanning direction of the optical sensor
A third printing portion which occur, first of the two patterns
The print section provided on the side without the print section 3
When there is no shift between the printing positions of the two patterns
Interpolate the second non-printing part without any gap in the scanning direction of the optical sensor
If the print position of both patterns is shifted, the shift
A fourth printing section for producing a third non-printing section corresponding to the amount
And the same and uniform printing density based on the printing section data.
Parallel in the scanning direction of the optical sensor
The calculating means calculates the detection width of the optical sensor in the scanning direction.
And the optical sensor when the optical sensor detects only the first printed portion.
And the optical sensor detects only the first non-printing part.
The output voltage value of the optical sensor at the time of output is
When everything falls within the detection width in the scanning direction of the optical sensor
The print position in the forward / reverse direction based on the output voltage value of the optical sensor
It is characterized in that the displacement amount is calculated .

[0009]

According to the present invention, forward printing has been positive printing <br/> pattern and the forward direction printing pattern with a predetermined test pattern on made of a reverse printed on the reverse printing pattern on the same line Then, an optical sensor having a detection width larger than twice the dot width is scanned to output a voltage that fluctuates according to a change in the print density of the test pattern. Then, the calculating unit calculates a shift amount of the printing position in the normal and reverse directions based on the output voltage value and the detection width of the optical sensor. The printing position in the forward and reverse directions is corrected by relatively shifting the printing timing in the directional printing. You
That is, the test pattern includes a forward print pattern and
The reverse direction print pattern prints the light sensor scanning method.
Wider in the scanning direction of the optical sensor than the detection width in the direction
A first printing unit and a first non-printing unit are provided;
If the printing position of both patterns is shifted,
A third non-print portion corresponding to the shift amount is generated. And the performance
Calculation means, the detection width of the optical sensor in the scanning direction,
When the optical sensor detects only the first printing portion,
The output voltage value and the optical sensor detects only the first non-printing part
The output voltage value of the optical sensor when the
Light when it is completely within the detection width in the scanning direction of the sensor
Based on the output voltage value of the sensor,
The shift amount is calculated, and the printing timing is determined based on the shift amount.
Correction means is used for printing in the forward direction and printing in the reverse direction.
Both the forward and reverse directions by relatively shifting the printing timing when printing
Is corrected.

Therefore, the shift amount of the print position in the forward and reverse directions is calculated irrespective of the magnitude of the fluctuation width of the output voltage of the optical sensor. Thereby, even if the print density gradually decreases or the fluctuation of the output of the optical sensor is small, such as when printing on paper other than white or gray or cream,
The displacement of the printing position in the forward and reverse directions can be reliably detected.

Further, the output voltage value of the light sensor will vary depending on the print <br/> changes in the concentration of the test pattern in a large detection range than twice the dot width, in the range larger than the dot width It will be constant. As a result, even if the sampling period of the output voltage value of the optical sensor is set to be longer than the dot width, it is possible to correct the deviation of the printing position in the forward and reverse directions with as high accuracy as the dot width, and it is necessary to use complicated software. There is no.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a serial printer to which the present invention is applied will be described with reference to the drawings. In this printer, as shown in FIG. 1, a print head 2 is provided so as to face a cylindrical platen 1, and recording paper 3 can be fed between the platen 1 and the print head 2 for printing. ing.

The platen 1 extends in a direction perpendicular to the paper feeding direction, and is conveyed so that the recording paper 3 is wound around a part of its outer periphery. This platen 1
Are rotatably supported at both ends and are also driven to rotate by a paper feed motor (not shown) via a deceleration mechanism (not shown) at the time of a line feed or the like, and are also used for conveying the recording paper 3.

The print head 2 is mounted on a carrier 4 and moves together with the carrier 4 along the platen 1 in a direction orthogonal to the paper feed direction so as to perform both forward and reverse printing. The carrier 4 is guided in parallel with the platen 1 by guide means (not shown). Carrier 4
, A part of the timing belt 5 is fixed, and a moving force is applied through the timing belt 5. The timing belt 5 is wound around timing pulleys 6 and 7 on both sides in the moving direction of the carrier 4, and is rotationally driven by a carrier motor 8 via one of the timing pulleys 6 to move the carrier 4 together with the print head 2 and the platen 1.
Along the paper feed direction.

The movement of the print head 2 in both the forward and reverse directions and the printing operation are controlled by a CPU (Central Processing Unit) 9 constituting a computing means. That is, the carrier motor 8 is connected to the CPU 9 via the motor driver 10 and the CPU 9
The carrier motor 8 is driven by a drive signal supplied to the print head 0, and the print head 2 is moved in both forward and reverse directions. The print head 2 is connected to the CPU 9 via a pin driver 11 and a delay circuit 12 which constitutes a print timing correction means.
The print head 2 performs a printing operation at a predetermined print timing by a drive signal supplied to the pin driver 11 through the CPU, and the print head 2 prints in the forward direction by a delay signal supplied from the CPU 9 to the pin driver 11 via the delay circuit 12. The printing operation is performed such that the printing timing at the time and the printing timing at the time of reverse printing are relatively shifted.

An inspection mode switch 13 and a storage circuit 14 are connected to the CPU 9.
Is operated, predetermined storage information is read from the storage circuit 14 and a test pattern 15 as shown in FIG. 2 is printed on the recording paper 3 via the print head 2.

The test pattern 15 is shown in FIG.
Forward printing pattern printed in the forward direction as shown in
A first pattern 16 as the first pattern 1
A reverse printing pattern printed in the reverse direction on the same line as 6.
And the second pattern 17. That is,
When the inspection mode switch 13 is operated, the print head 2
1 moves in the forward direction (the direction of arrow A in FIGS. 1 and 2), the first pattern 16 is printed on the recording paper 3 and the print head 2 moves in the reverse direction (arrow B in FIGS. 1 and 2). Direction), the second pattern 17 is printed on the same line as the first pattern 16 of the recording paper 3. FIG. 2A shows the first pattern 16 and the second pattern for convenience.
The pattern 17 is shown separately.

As shown in FIG. 2A, the first pattern 16 includes a pattern 16a as a first printing portion and a first pattern 16a .
A pattern 16b as a second printing portion, a third printing portion,
The patterns 16c, 16d, and 16e are intermittently printed solidly in the row direction at predetermined intervals.
Space as the first non-printing part between the pattern and the pattern 16b
A blank portion 16g, 16h as a second non-printing portion exists between the pattern 16b and the pattern 16c, between the pattern 16c and the pattern 16d, and between the pattern 16d and the pattern 16e. 1
6i exists. On the other hand, the second pattern 17 has a blank portion 16g of the first pattern 16,
The blank portions 16g, 1 at the positions corresponding to 16h and 16i.
Patterns 17a, 17b, and 17c as fourth printing portions having the same width as 6h and 16i are intermittently solid-printed.

Therefore, when there is no shift in the print position in the forward and reverse directions, solid printing is continuously performed without a gap from the pattern 16b to the pattern 16e as shown in FIG. blank portion 16f having a predetermined width W ₀ is to remain only between.

On the other hand, when the print position in the forward / reverse direction is shifted in the forward direction, that is, the print position of the second pattern 17 is shifted in the forward direction relatively to the print position of the first pattern 16. Sometimes, as shown in FIG. 2D, the pattern 17a partially overlaps the pattern 16c, the pattern 17b partially overlaps the pattern 16d, and the pattern 17c partially overlaps the pattern 16e. 16
blank portion 16f having a predetermined width W ₀ between a and pattern 16b
Remain between the pattern 16b and the pattern 17a, between the pattern 16c and the pattern 17b, and between the pattern 16b and the pattern 17b.
a third non-printing portion having a width W ₀₀ that matches the shift amount of the printing positions of forward and reverse directions between the d and the pattern 17c
All the blank portions 16g, 16h, and 16i remain.
In addition, the overlapping part of the pattern 17a and the pattern 16c,
Overlap between overlapping portions and patterns 17c and pattern 16e of the pattern 17b and the pattern 16d are both a high density portion with a width W ₀₀ that matches the shift amount of the printing position in the forward and reverse directions.

On the other hand, when the print position in the normal / reverse direction is shifted in the reverse direction, that is, when the print position of the second pattern 17 is shifted in the reverse direction relative to the print position of the first pattern 16. As shown in FIG. 2F, the pattern 17a partially overlaps the pattern 16b,
b partially overlaps the pattern 16c and the pattern 17
c is partially overlapped on the pattern 16d, between the pattern 16a and the remaining blank portion 16f having a predetermined width W ₀ between the patterns 16b, between the pattern 17a and the pattern 16c, the pattern 17b and the pattern 16d and pattern blank portion 16g of the width W ₀₀ that matches the shift amount of the forward and reverse directions of the printing position between the 17c and the pattern 16e, 16h, so that the 16i remains. In this case as well, the overlapping portion of the pattern 17a and the pattern 16b, the overlapping portion of the pattern 17b and the pattern 16c, and the pattern 17c and the pattern 1
Overlap and 6d are both a high density portion with a width W ₀₀ that matches the shift amount of the printing position in the forward and reverse directions.

An optical sensor 18 is connected to the CPU 9.
The operation of the optical sensor 18 is controlled, and the output data of the optical sensor 18 is input. Optical sensor 1
Numeral 8 is mounted on the carrier 4 so as to face the printing surface of the recording paper 3 and, in this embodiment, be located one line downstream of the print head 2. For this reason, the optical sensor 18 faces the test pattern 15 by a line feed operation of one line after the printing of the test pattern 15, and is scanned over the test pattern 15 by the subsequent movement operation of the carrier 4.
The line feed operation and the movement operation of the carrier 4 at this time are C
Controlled by PU9. That is, when the inspection mode switch 13 is operated, the CPU 9
, The test pattern 15 is printed on the recording paper 3, and then the paper feed motor is driven to feed a new line by one line so that the optical sensor 18 faces the test pattern 15.
After that, the carrier motor 8 is driven to
Is scanned.

As shown in FIG. 3, the light sensor 18 includes an infrared light emitting diode 18a and a phototransistor 1
8b, when the test pattern 15 is scanned, light is emitted from the infrared light emitting diode 18a to the test pattern 15 by a driving signal from the CPU 9 and the reflected light is received by the phototransistor 18b. Is output from the phototransistor 18b. That is, the output voltage of the phototransistor 18b fluctuates according to a change in the print density of the test pattern 15. The infrared light emitting diode 1
The light emitted from 8a to the test pattern 15 is converged by the convex portion at the tip of the infrared light emitting diode 18a, and is applied to the test pattern 15 without waste.

The infrared light emitting diode 18a and the phototransistor 18b are covered with a housing 20 so that disturbance light does not enter the phototransistor 18b.
A slit 20 a is formed in the housing 20 at a portion facing the printing surface of the recording paper 3, and the infrared light emitting diode 18 a passes through the slit 20 a from the test pattern 15.
Is illuminated, and the reflected light is applied to the slit 20.
The light is received by the phototransistor 18b through a. That is, the width D of the slit 20a is the detection width of the optical sensor 18.

The width D of the slit 20a, as shown in FIG. 4 (a), than the width of the with the pattern 16a is set smaller than the width W ₀ of the blank portion 16f
Small set, and the length L of the slit 20a is set smaller than the height H of the test pattern 15. The width D of the slit 20a is set to be larger than twice the dot width.
5, the output voltage of the phototransistor 18b fluctuates according to the print density change.

[0026] For example, when the optical sensor 18 is scanned across the front and rear blank portion 16f of the large width W ₀ than the width D of the slit 20a, a slit 20a as shown by the two-dot chain line in FIGS. 4 (a) In the position where the entire area of the phototransistor faces the printing portion, light is irradiated only from the infrared light emitting diode 18a to the printing portion and the light reflectance is low.
7b is not turned on, the output voltage value of the phototransistor 17b becomes high, which is "V _B" as shown in Figure 4 (b).
Then, when a part of the slit 20a reaches the blank portion, a current gradually starts flowing through the phototransistor 18b, and the output voltage value of the phototransistor 18b changes accordingly.
It gradually decreases as shown in FIG. Thereafter, when the slit 20a moves by a distance equal to the width dimension D, the entire area of the slit 20a faces the blank portion (see the broken line state), and light is emitted only from the infrared light emitting diode 18a to the blank portion, so that the phototransistor 18b 4B is lower than “V _B ” as shown in FIG.
_W ". Slit 20a from this state - the (W ₀ width D) moves only (one-dot chain line state), the output voltage value of the phototransistor 18b gradually rises back to the "V _B". Accordingly, the output voltage value of the phototransistor 18b when the entire area of the slit 20a faces the printing portion is “V _B ”, and the output voltage value of the phototransistor 18b when the entire area of the slit 20a faces the blank portion is “V _B ”. _B ”, which is lower than“ V _W ”, and the output voltage of the phototransistor 1 from“ V _B ”to“ V _W ”.
Output voltage waveform of 8b is inclined at a range of the width D of the slit 20a, and becomes the output voltage waveform in between the phototransistor 18b is constant in a range obtained by subtracting the width D of the slit 20a from the width W ₀ of the blank portion.

Similarly, as shown in FIGS. 2D and 2F, the printing position in the forward and reverse directions is shifted and the width D of the slit 20a is changed.
The remaining blank portion 16g of the small width W ₀₀ than when the optical sensor 18 is scanned over this back and forth, and FIG. 5 (b)
Phototransistor when the entire area of the slits 20a as shown is opposed both sides of the printing unit phototransistor 18b output voltage value "V _B" next, slit 20a is across a blank portion when the opposite the printing portion and lower the output voltage value of 18b is than "V _B", "V _W" (FIG. 4
(Refer to (b)), and the phototransistor 1 has a higher output voltage value from “V _B ” to “V”.
Output voltage waveform of 8b is inclined at a range of the width W ₀₀ of the blank portion,
And the output voltage waveform in between the phototransistor 18b is constant in a range obtained by subtracting the width W ₀₀ of the blank portion from the width D of the slit 20a.

The phototransistor 18b is connected to the CPU 9 via an A / D converter 19, and an output voltage value is input to the CPU 9. The CPU 9 samples the output voltage value of the phototransistor 18b at a predetermined timing, and calculates the deviation amount of the printing position in the forward and reverse directions based on the output voltage value of the phototransistor 18b and the width D of the slit 20a at this time. A delay signal is supplied to the delay circuit 12 based on the shift amount, and the delay circuit 12 relatively shifts the print timing in forward printing and the print timing in reverse printing to shift the print position in both the forward and reverse directions. Correction is made so as not to occur.

Here, when calculating the shift amount of the print position in the forward and reverse directions, the absolute amount of the shift of the print position in the forward and reverse directions is calculated based on the output voltage value of the phototransistor 18b and the width D of the slit 20a. Calculate and determine the direction of the print position shift in the forward and reverse directions based on the output voltage value of the phototransistor 18b at the predetermined position, and determine the absolute amount of the print position shift in the forward and reverse directions and the absolute The amount of deviation of the print position in the forward and reverse directions is calculated from the direction of the deviation.

Here, the width D of the slit 20a is
The width W of the blank portion smaller than the width D of the slit 20a
Attention is paid to the relationship between ₀₀ and the output voltage value V of the phototransistor 17b. The entire area of the slit 20a is the slit 20a
When opposed to only the blank portion 16f of the large width W ₀ than the width D of the illuminance (broken line state of FIG. 4 (a)) and E _W, when the entire area of the slit 20a is opposed only to the printed portion (FIG. 4 the illuminance of the chain line state) of (a) is taken as E _B, the average illuminance E in the slit 18a when the slits 20a are opposed to the both side of the printing unit across a blank portion of the width W ₀₀ is, E = ( W ₀₀ / D) × E _W + (1− (W ₀₀ / D)) × E _B (1), and the ratio of the width W ₀₀ of the blank portion of the test pattern 15 to the width D of the slit 20 a is: From formula (1), W ₀₀ / D = (E−E _B ) / (E _W −E _B ) (2)

On the other hand, from the characteristics of the phototransistor, the output voltage value V of the phototransistor 18b is generally

[0032]

(Equation 1)

[0033] a since, the output voltage value at E _W and V _W, and the output voltage value at the E _B and V _B, the slits 20
The relationship between the width D of a, the width W _{00 of the} blank portion, and the output voltage value V of the phototransistor 17b is obtained from the equation (2).

[0034]

(Equation 2)

## EQU1 ##

Based on the above equation (4), the entire area of the slit 20a has a width W larger than the width D of the slit 20a.
The output voltage value V _W of the phototransistor 18b when facing only the blank portion 16f of _{0 and} the phototransistor 1 when the entire area of the slit 20a faces only the printing portion.
8b, the output voltage value V _B and the slit 20a
An output voltage value V of the phototransistor 18b of the case opposed to the both side of the printing unit across a blank portion of smaller width W ₀₀ than the width D of 0a, the blank portion which is calculated based on the width D of the slit 20a than the width W _00, it can detect the absolute amount of displacement of the forward and reverse directions of the printing position. Since the value of the constant β in Expression (3) is approximately “1”, for example, the slit 20a
If the width dimension D is set to 2 mm, it is sufficient to detect a voltage variation of about 5% in order to detect a blank portion of W ₀₀ = 0.1 mm. Absolute amount can be detected.

Further, paying attention to the test pattern 15 when the forward and reverse directions of the printing position is displaced, they were separated by X ₁ and X ₂ with respect to the center position of the blank portions 16f as shown in FIG. 2 position P1 ( Comparing the output voltage values of the phototransistor 18b at the start point position of the blank portion 16g) and the position P2 (end point position of the blank portion 16g), FIG.
As shown in (f), one of the output voltages is lower than the output voltage value V _B (the output voltage value when light is emitted only from the infrared light emitting diode 18a to the printed portion), and the other is the output voltage value due to dot overlap. It is higher than the value V _B.

Then, based on this characteristic, the output voltage value of the phototransistor 18b at the position P1 is
Compared by _B, the output voltage value is output voltage of the phototransistor 18b value at the position P1 as shown in FIG. 2 (e) V
_If it is lower than _B, it is determined that the print position in the forward / reverse direction is shifted in the forward direction. Conversely, the determination and the output voltage value of the phototransistor 18b at the position P1 as shown in FIG. 2 (f) when higher than the output voltage value V _B, the forward and reverse directions of the printing position is shifted in the opposite direction It is supposed to.

Next, the operation will be described. If the printing position in both the forward and reverse directions is shifted, by operating the inspection mode switch 13, the printing position shift in both the forward and reverse directions is automatically corrected, and proper printing can be performed.

That is, when the inspection mode switch 13 is operated, the print head 2 is driven to print while moving in the forward direction, so that the first pattern 16 is printed on the recording paper 3 and the print head 2 is moved in the reverse direction. The second pattern 16 is printed on the recording paper 3 while printing is performed, and a test pattern 15 as shown in FIG. 2D or 2F is printed.

After printing the test pattern 15, the recording paper 3
Is changed by one line, and thereafter, the carrier 4 is scanned, and the optical sensor 18 is scanned on the test pattern 15.
During this scanning, light is emitted from the infrared light emitting diode 18a to the test pattern 15 through the slit 20a, and the reflected light is received by the phototransistor 18b through the slit 20a, and the width D of the slit 20a is larger than twice the dot width. The output voltage of the phototransistor 18b fluctuates according to the change in the density of the test pattern 15 within the circuit.

The output voltage of the phototransistor 18b is input to the CPU 9 via the A / D converter 19, and the CPU 9 samples the output voltage value of the phototransistor 18b at a predetermined timing. Output voltage value and slit 20a
The shift amount of the printing position in the normal and reverse directions is calculated based on the width D, and a delay signal is supplied to the delay circuit 12 based on the shift amount. The print timing at the time is relatively shifted, whereby the shift of the print position in both the forward and reverse directions is corrected. Here, when calculating the shift amount of the print position in the forward and reverse directions, the entire area of the slit 20a is slit. 20a and the output voltage value V _W of the phototransistor 18b when the opposed to only the reference blank portion 16f of the large width W ₀ than the width D of the output of the phototransistor 18b when the entire area of the slit 20a is opposed only to the printed portion the voltage value V _B, the slits 2
0a and the output voltage value V of the phototransistor 18b of the case opposed to the printing unit on both sides across the blank portion of smaller width W ₀₀ than the width D of the slit 20a, the width D of the slit 20a
As a result, the width W _{00 of the} blank portion based on the above equation (4),
That is, the absolute amount of deviation of the print position in the forward and reverse directions is calculated.

The phototransistor 1 at the position P1
The output voltage value of 8b was sampled compared with the output voltage value V _B, when the output voltage value of the phototransistor 18b at the position P1 as shown in FIG. 2 (e) is lower than the output voltage value V _B is It determines that the forward and reverse directions of the printing position is shifted in the positive direction, when the output voltage value of the phototransistor 18b at the position P1 as shown in FIG. 2 (f) the reverse is higher than the output voltage value V _B is It is determined that the print position in the forward / reverse direction is shifted in the reverse direction, and the print position shift in the forward / reverse direction from the absolute amount of the print position shift in the forward / reverse direction and the direction of the print position shift in the forward / reverse direction. Calculate the amount.

Accordingly, the shift amount of the print position in the forward and reverse directions is calculated based on the output voltage value of the phototransistor 18b and the width D of the slit 20a. It can be calculated irrespective of the magnitude of the fluctuation range of the output voltage, so that even when the print density gradually decreases or when printing is performed on paper other than white, such as gray or cream, The displacement can be reliably detected.

Further, since the width D of the slit 20a is set to be larger than twice the dot width, the output voltage of the phototransistor 18b becomes constant within a range larger than the dot width, and the output voltage of the phototransistor 18b becomes constant. Even if the sampling period of is set larger than the dot width,
The deviation of the printing position in the forward / reverse direction can be detected with high accuracy (high resolution) equivalent to the dot width, and there is no need to use complicated software. For example, when the width W ₀₀ of the blank portion when the width D of the slit 20a to 2mm is 0.1mm, the photo when the slits 20a are opposed to the both side of the printing unit across a blank portion of the width W ₀₀ The output voltage value of the transistor 18b becomes constant within a range of D−W ₀₀ = 1.9 mm (see FIG. 5), and within this range, the phototransistor 18b
Can be set, and the sampling cycle of the output voltage of the phototransistor 18b can be set to be much longer than the dot printing cycle. Further, if the output voltage of the phototransistor 18b is sampled only a plurality of times in this range and the absolute value of the print position deviation in the forward and reverse directions is calculated from the average value of the output voltage values, a more accurate detection result can be obtained. .

Further, since the optical sensor 18 having a detection width larger than twice the dot width can sufficiently cope with it, a low-resolution low-cost sensor can be used.

[0047]

As described in the foregoing, in the serial printer according to the present invention has a large detection range than twice the dot width, forward printing has been positive printing pattern and the positive
Reverse direction is reverse printed on the direction the print pattern and the same line
An optical sensor that outputs a scanned test pattern on consisting of a printing pattern voltage value that varies in accordance with the printing density change of the test pattern, the output voltage value of the light sensor Oyo
Calculating means for calculating a shift amount of forward and backward directions of the printing position based on the fine detection width, the printing timing of the printing timing and the reverse printing during forward direction printing based on the shift amount calculated by the calculating means A printing timing correction means for correcting the printing position in both the forward and reverse directions by relatively shifting
With a forward print pattern and a reverse print pattern.
Is provided on one of the two patterns.
The detection width in the scanning direction of the optical sensor in the printing section
A first printing unit wider in the scanning direction of the optical sensor than
Printing provided on one of the two patterns
From the detection width of the optical sensor in the scanning direction
Also produces a first non-printing area wide in the scanning direction of the optical sensor.
The second printing portion to be made, and any one of the two patterns
The printing section provided on one side and the scanning of the optical sensor
A third non-printing portion having a predetermined width in the direction
A print portion and a third print portion of the two patterns.
Printing part provided on the side where no
When there is no shift in the printing position of
Interpolate without gaps in the scanning direction of the optical sensor and
When a shift occurs in the printing position,
And a fourth printing section for producing a third non-printing section.
Light with the same and uniform print density based on
Which are arranged in parallel in the scanning direction of the sensor,
It has a detection width that put in the scanning direction of the light sensor, a light sensor
Output voltage value of the optical sensor when only the first print part is detected
And the optical sensor when the optical sensor detects only the first non-printing portion.
Sensor output voltage and the third non-printing part
Of the optical sensor when everything falls within the detection width in the direction
Calculates the deviation of the print position in the forward and reverse directions based on the force voltage value.
Even if the print density gradually decreases, or if a medium tone paper such as gray or cream color is used, the deviation of the print position in the forward and reverse directions can be reliably detected, and complicated software can be used. There is an excellent effect that the deviation of the printing position in the forward / reverse direction can be corrected with high accuracy without using it.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a serial printer to which the present invention is applied.

FIG. 2 is a diagram showing a correspondence relationship between a mode of a test pattern change and an output voltage waveform of an optical sensor at that time.

FIG. 3 is a sectional view of an optical sensor.

FIG. 4 is a diagram showing the relationship between the test pattern and the output voltage waveform of the optical sensor when a blank portion larger than the detection width of the optical sensor exists in the test pattern.

FIG. 5 is a diagram showing the relationship between the test pattern and the output voltage waveform of the optical sensor when a blank portion smaller than the detection width of the optical sensor exists in the test pattern.

[Explanation of symbols]

2 Print Head 3 Recording Paper 9 CPU (Calculation Means) 12 Delay Circuit (Print Timing Correction Means) 15 Test Pattern 16 First Pattern (Forward Print Pattern) 17 Second Pattern (Reverse Print Pattern)

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41J 2/51 B41J 19/18 B41J 29/46

Claims (1)

(57) [Claims] 1. A serial printer capable of forward and backward printing, has a large detection range than twice the dot width, in the forward direction printing has been positive printing pattern and the forward direction printing pattern on the same line An optical sensor that scans over a test pattern including a reverse print pattern printed in the reverse direction and outputs a voltage value that fluctuates according to a change in print density of the test pattern; an output voltage value and a detection width of the optical sensor Calculating means for calculating the shift amount of the printing position in the forward and reverse directions based on the print timing, and relative to the printing timing for the forward printing and the printing timing for the reverse printing based on the shift amount calculated by the calculating means. shifting and a printing timing correction means for correcting the forward and backward shift of the printing position, the and the forward printing pattern and the reverse printing pattern
Is provided on one of the two patterns.
A detection unit in the printing unit and in the scanning direction of the optical sensor.
A first mark wider in the scanning direction of the optical sensor than the projection width;
Character part and one of the two patterns.
Printing section and the scanning direction of the optical sensor
A first width wider than the detection width in the scanning direction of the optical sensor.
A second printing portion that generates a non-printing portion of
Printing part provided in one of the
A second non-printing having a predetermined width in the scanning direction of the optical sensor;
And a third printing portion that produces
The printing section provided on the side not having the third printing section
And the printing position of both patterns does not shift
Sometimes the second non-printing part is moved in the scanning direction of the optical sensor.
Interpolation without gaps, and there is no
When this occurs, the third non-printing portion corresponding to the shift amount is
The fourth print portion to be generated is determined based on the print portion data.
Scanning of the optical sensor with the same and uniform print density
Are those obtained by parallel direction, said calculating means, detection in the scanning direction of the optical sensor
Width and the optical sensor has detected only the first printed portion
The output voltage value of the optical sensor when
Output of the optical sensor when only the first non-printing portion is detected
The voltage value and the third non-printing part are determined by the scanning method of the optical sensor.
Of the optical sensor when it is completely within the detection width in
Based on the output voltage value, the deviation amount of the print position in the
A serial printer characterized by calculating .