JPH11314427A - Position detecting system for printing medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance position detecting accuracy of a print medium by detecting the image of a series of marks moving along with the print medium, comparing it with a pattern aligned with the series of marks while being delayed by a different angular distance therefrom and delivering a signal it they match each other. SOLUTION: An SOP mark 111 is constituted by forming parts 111a-111c which is in contrast relationship with the color of a print medium at a plotting start position in a continuous color band which is in contrast relationship with the color of the print medium. An LED delivers an infrared signal to a control track 110 disposed oppositely to sensors OP5, OP6. Light reflected from the mark parts 111a-111c of a moving print medium is detected by the sensors OP5, OP6. Difference in the intensity of both detected lights is determined as a difference signal and the part 111a-111c of the print medium is determined from the variation of the difference signal. Position of the print medium can be detected accurately by delivering a signal when a specified pattern is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic printer, and more particularly, to a system for accurately detecting the position of a print medium in an electrostatic printer.

[0002]

BACKGROUND OF THE INVENTION In an electrostatic printer, a system / method for energizing a functional element (e.g., a stylus of an electrostatic printhead) in relation to a moving substrate (Paper) is disclosed by David E. Dogget in U.S. Pat. , 73
No. 1,542 (published May 15, 1988). According to the system / method, a tracking line formed on a substrate and having an energizing mark (SOP mark) that reflects light of an intensity different from the intensity of light reflected from other portions. line) to energize the functional element in relation to the moving substrate. A photo sensor attached to the tracking line senses the intensity of light reflected from the tracking line as the substrate moves. Output signal generated by the photo sensor (typically SOP
(Referred to as a signal) indicates that the SOP mark has passed the photosensor and energizes the functional element. According to the system / method, the SOP can be indicated when the paper passes the print head of the electrostatic printer.

[0003] In an electrostatic printer, there are generally a plurality of black and white lines that alternate closely adjacent one edge of the paper on which the plot is to be formed. This line (sometimes called an "indicia" or sometimes a "tick mark") can be significantly spaced, depending on the circuitry and software that operates it. Sometimes very small spacing (0.010 inches). David E.
Dogget FIG. 12 of the accompanying drawings of U.S. Pat. No. 4,731,542 shows an SOP mark for generating an SOP signal. In one embodiment, a total of two tracking lines are provided, one on each side of the print medium (substrate, paper). Tracking SOP mark
Simultaneously formed on the line; one side of the print medium
One mark of the OP mark is formed, and the other SOP mark is formed on the other surface. If the print medium is aligned with the sensors provided on each side, both SOP marks will pass through both sensors simultaneously. However, if the position of the SOP mark is not aligned, one SOP mark passes through the sensor first. Therefore, before generating the SOP signal, the print head is aligned with the left and right SOP marks within one tick mark width by the first pair of SOP marks. As a procedure of this matching method, one S of the SOP mark is used.
If the OP mark is behind the other SOP mark, the servo mechanism is energized to correct the delay on one side of the print medium. Subsequently, each SOP mark is replaced by one tick
The SOP signal is generated by the second pair of SOP marks aligned within the range of the mark. An SOP signal can be generated by any of the SOP marks.

[0004]

The sinusoidal wave 224 of FIG. 12 of the accompanying drawings of US Pat. No. 4,731,542 of David E. Dogget shows that the SOP mark on the print medium (substrate) passes through the sensor. Indicates the relative intensity of the signal generated. The position of the zero crossing 260 of the sine wave 224 moves left and right depending on the contrast between the dark mark and the bright substrate with the dark mark. S
The OP signal generates a zero intersection 260 at which data printing begins, and the position of the tick mark is ambiguous because the pitch of the tick mark (ie, the spacing between adjacent tick marks) changes the position of the zero intersection 260. If so, one tick mark may be ambiguous at the start of the plot. Since one tick mark is equivalent to four print lines (the line spacing printed by the electrostatic printhead is 0.0225 inches and the center line spacing of the tick marks is 0.010 inches).
The SOP ambiguity is four lines. This is an ambiguity that cannot be absolutely tolerated when high-precision printing needs to be performed, such as when printing is performed on a semiconductor integrated circuit.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a print medium position detecting system capable of accurately detecting the position of a print medium.

[0006]

According to the present invention, there is provided a system for designating a position on a moving print medium, comprising: A series of equally spaced tick marks printed on the print medium, each width being approximately equal to the spacing between adjacent ones; ticks set on one device, each for one section A plurality of patterns substantially identical to each other, wherein one pattern is aligned with the tick mark sequence as the tick mark sequence moves with the print medium, and the other patterns are each moved. Patterns arranged to be delayed by different angular distances from the row; projection means for superimposing the image of the moving tick mark row on the apparatus; Sensing means for sensing the image of the tick mark row, said image is for generating a signal if substantially matches the one pattern.

In order to achieve the above object, the present invention provides a system for generating timing means for detecting a tracking line composed of a series of equally-spaced marks printed on a moving print medium. It is characterized in that it is located at the first position, and the first row of the equally-spaced mark sequence passes through the first position at a constant period, and the first line at the first position. A first sensor for generating an output signal sequence; substantially the same as the first sensor, and located at a second position, and a second sensor in response to the equidistant mark sequence passing through the second position in the cycle; A second sensor that generates a second periodic signal sequence with the period delayed from the first output signal sequence by a first time corresponding to １ ／ times the period between adjacent signals of one output signal sequence; It is almost the same as the first sensor, and is located in the third position. A second time corresponding to half the period between adjacent signals of the first output signal sequence in response to the equally-spaced mark sequence passing through the third position in the cycle. A third sensor that generates a third periodic signal sequence with the same period behind the first output signal sequence; substantially the same as the first sensor, and is located at the fourth position, and the equally-spaced mark sequence is In response to passing through the fourth position in the cycle, the first output signal train is delayed from the first output signal train by a third time corresponding to 3/4 times the cycle between adjacent signals of the first output signal train. A third sensor that generates a fourth periodic signal sequence with a period (where the first, second, third, and fourth periodic signal sequences are at right angles to each other); A plurality of periodic signals generated according to the signals of the first, second, third, and fourth periodic signal sequences by combining the third and fourth periodic signal sequences; Signal processing means for the fifth periodic signal sequence is generated as the timing means comprising.

The present invention for achieving the above object is used in a print medium, and instructs a sensing means having a certain range to start plotting a print line on the print medium.
A component mark, characterized by being composed of two parts: located above a reference line, occupying a first area, and extending from said area of said sensing means. The first distance is also greater than the reference
A first portion protruding upward from the line; located below the reference line, immediately after the first portion, and from the reference line a second distance greater than the range of the sensing means. The second part protruding downward.

According to the system / method of the present invention, a print medium (a substrate on which information is to be printed) is provided.
Use a three part SOP mark in conjunction with a separate tick mark track. The first SOP mark is a continuous reference line
SOP line on one side of the second SOP
The mark portion is located on the other side of the continuous reference line, and the third SOP mark portion is located on one side of the continuous reference line. The areas of the three SOP marks are almost equal. As the substrate moves, the three-part SOP mark passes above the two sensors.

[0010] The edge of the tracking line is located above the center of response of the two sensors. Therefore, both sensors sense the tracking line and the same portion of the blank printing medium as long as the position does not deviate from the tracking line. Under ideal conditions, the outputs of both sensors are balanced. If the tracking line is displaced laterally, the outputs of both sensors will be out of balance and the servo mechanism will work accordingly to realign the printhead with the tracking line.
As the three-part SOP mark passes over the two sensors, the first SOP mark portion covers one sensor with a completely dark image and the other sensor with a blank print medium. This creates a large imbalance between the outputs of the two sensors and requires the servo mechanism to fail. Subsequently, the second SOP mark portion covers the first sensor with a blank print medium, and the second sensor is covered with a completely dark image. This again causes an imbalance between the outputs of both sensors (but the reverse is true). The third SOP mark portion creates the same state as the first SOP mark portion.

The difference between the output currents of the two sensors is 1
It generates two signals and converts them into voltage signals. When the tracking line is present, the position information of the line is included in this voltage signal, and when the SOP mark is present, the information regarding the position of the SOP is included in this voltage signal.

The peak of the signal generated by the first SOP mark portion passing through the sensor and the second signal passing through the sensor are generated.
The peak of the signal where the OP mark portion occurs is detected, and the value is stored. Subsequently, the two peak signals are added to form a reference signal (threshold). 2nd S
When the OP mark portion has passed through the sensor and the sensor starts sensing the third SOP mark portion, a signal obtained by adding the signals generated by the first and second sensors is compared with a reference signal. A signal obtained by adding the output signals generated by the first and second sensors when the third SOP mark portion of the substrate passes through the sensor (referred to as "sum signal").
Is equal to the reference signal, an SOP signal is generated,
One lot is started. An SOP signal is generated in response to a zero crossing of the sum signal indicating that a desired position to start plotting has been detected. The term "zero crossing" is not completely accurate, but it does convey the basic function of this part of the circuit. When the print medium moves from the second SOP mark portion to the third SOP mark portion above the sensor, the reference signal (threshold) and the actual level of the sum signal are compared, and if both are equal, an SOP signal is generated. A threshold is generated by adding the positive and negative peaks of the signals generated by the first and second sensors when the first and second SOP mark portions pass through the sensor.

In the prior art, the difference in contrast between the ink and the background of the print medium has caused
Depending on the reflection / illumination level of the print media, the differences in the specifications of each sensor, and the misalignment of the sensors and sensor assemblies due to uncertainties associated with the sensor assemblies, the tick mark SOP signal is best. There is a possibility of changing by four lines. Unlike the conventional system, the system of the present invention has a self-compensation function. In the system of the present invention, rather than relying on a zero crossing with respect to the absolute reference zero, the position of the sensor that senses the SOP mark, the difference in the specifications of the individual sensors, and the difference between the SOP mark and the background of the print medium. An absolute reference zero considering the difference in contrast between the two is generated, and an SOP signal is generated based on the reference level.

In one aspect of the present invention, the change in ink strength to form SOP marks on the substrate results in a change due to the reflection / illumination level of the print media, as well as specific characteristics of the sensor. Automatically compensate for position changes.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a sheet on which an image is to be printed (print medium).
SOP mark 11 provided on a separate track above
1 is an illustration.

FIG. 2 shows the SOP mark 111 shown in FIG. 1A.
It is an illustration of a relative position of two sensors OP5 and OP6 for detecting the state.

FIG. 3 shows the sensors OP5 and OP shown in FIG.
Portions 115t, 11 of the opening 115 in which 6 is set
5 is an illustration of a waveform 130 generated when the SOP mark 111 passes through 5b.

FIG. 4 shows the SOP mark 1 of the substrate.
11 (FIG. 1) is a block diagram of a circuit for processing signals generated by the sensors OP5 and OP6 when passing through the sensors OP5 and OP6 shown in FIG.

FIGS. 5A and 5B show a two-part SO.
5 is an illustration of a waveform at a P-mark, showing the effects of sensor sensitivity imbalance, changes in print media illumination levels, or even changes in reflection levels.

FIG. 6 shows a prior art two-part SOP.
It is an illustration of a mark.

FIG. 7 is an illustration of the two-part SOP mark of the present invention, which consists of two parts located above and below the tracking line.

FIG. 8 is an illustration of the three-part SOP mark of the present invention and the sensors OP5 and OP6 that detect the mark (the position of the center line 114 of the three-part SOP mark and the center line 214 of the sensors OP5 and OP6). Is shifted).

FIG. 9 is an illustration of two replicas of the circuit shown in the block diagram of FIG. 4 according to one embodiment of the present invention (replica 3A processes the signal generated by the left SOP mark and replica 3A ´ is the right SO
The signal generated by the P mark is processed).

FIGS. 10, 11 (a) to 11 (c), and FIGS. 12 (a) to 12 (e) show the operating principle of the circuit shown in FIG.

FIGS. 13 and 14 show the SOP mark 111,
Tick mark 720 and right angle gratings 701a, 701
01b, 701c, 701d
Indicates the position of OP6.

FIGS. 15 and 16 are block diagrams of the quadrature sensor circuit used in the system / method of the present invention.

FIG. 17 shows the SOP mark 111 of the print medium.
FIG. 17 is a plan view showing the position of the sensor assembly with respect to the moving tick mark 720.

FIG. 18 is a perspective view of the sensor assembly 700, showing the positions of the right-angle gratings 701a, 701b, 701c, and 701d with respect to the sensors OP1, OP2, and OP3.
And openings 115 for sensors OP5 and OP6
The positions of t and 115b are shown.

FIG. 19 is a perspective view of the sensor assembly 700 in relation to a moving print medium.

FIG. 20 is a plan view of an LED phototransistor package constituting the sensors OP1 to OP6.

FIG. 21 shows a portion 115t, 1
The position of the LED / phototransistor package of OP5 and OP6 with respect to the position of 15b is shown (sensor OP
Only the light emitted from the LED No. 6 is detected by the phototransistors of the sensors OP5 and OP6).

FIG. 22 shows the R of the sensor assembly 700 (FIG. 17) that generates a right angle output signal for the print media moving tick mark 720 (FIGS. 13, 14, and 17).
onchi gratings 701a, 701b, 701c, 701d,
701d indicates the relative position. FIG. 23 shows that the tick mark 720 (FIG. 17) of the print medium is
Ronchi gratings 701a, 701b, 701c, 701
d (FIGS. 13, 14, 17, and 18), the right-angle sensors OP1, O2 shown in FIGS.
5 shows waveforms generated by P3, OP4, and OP2.

FIG. 24 shows the right angle sensors OP1, OP3,
A process of performing exclusive-OR processing on the sine signal and the cosine signal generated by OP4 and OP2 to generate a print signal for each plot line on the print medium will be described.

In order to understand the present invention, the optical sensors OP1 to OP6 (FIG. 1, FIG. 13, FIG. 14, FIG. 17, FIG. 17) for the tick mark 720 (FIGS. 13, 14, 17) and the SOP mark 111 (FIG. 1, FIG. 13, FIG. 1, 2, 3, 4 and 1
It is the liver and kidney that the position of 3, 3, 14 and 15) should be confirmed. As shown in FIGS. 17 to 19, sensors for detecting the tick mark 720 and the SOP mark 111 of the print medium are housed in the same sensor assembly 700. The structure of the sensor assembly is the applicant of the present application.
Dale C. Frese concurrent application filed by Synergy Computer Graphics Corporation "A Sensor Assembly f
or Sensing Printed Marks on a Print Medium "(U.S. patent application Ser. No. 07 / 455,642); Referenced in the application specification.

FIG. 17 is a plan view of the sensor assembly 700, showing the sensor assembly 700 with respect to the print medium 128.
The positional relationship of is shown. The print medium 128 is the sensor assembly 7
00 in the direction of arrow 129 in relation to
The P mark 111 passes under the sensors OP5 and OP6, and the tick mark 720 sequentially turns the sensors OP1 and OP6.
Pass under OP3, OP4, OP2.

FIG. 18 is a perspective view of the sensor assembly 700, showing the right-angle gratings 701a to 701d and the opening 11
5 shows the positional relationship of the optical sensors OP1 to OP6 with respect to the portions 115t and 115b (FIG. 1). FIG. 19 shows a moving print medium 128 and ticks of the print medium 128.
The positional relationship of the sensor assembly 700 with respect to the mark 720 and the SOP mark 111 is shown. The sensor assembly 700 is located above the print medium 128 and the sensor OP
1, OP3, OP4, OP2 are tick marks 720
, And senses light reflected from tick mark 720, while sensors OP5, OP6
The SOP mark 111 is adjacent to the mark 111.
Sensing light reflected from one or three parts.

Screws are screwed into two sets of three screw holes 702, 702 'on both sides of the sensor assembly 700 to fix the sensor assembly 700 to a frame (not shown); It goes without saying that the sensor assembly 700 can be fixed to the structure using another appropriate fastener. The top surface of the sensor assembly 700 is provided with a glass coating of opaque conductive material; a semi-transparent rectangular piece 701 is provided in the center of the glass parallel to the tick marks 720 of the print medium 128, It can be positioned below the mark 720. The small translucent window 115 adjacent to the rectangular piece 701 corresponds to the portions 115t and 115b of the opening 115 shown in FIG. The center rectangular piece 701 has four sets of mutually perpendicular angles, typically (but not necessarily) engraved.
Ronchi gratings 701a, 701b, 701c, 701d
Is built in. A Ronchi grating is a set of lines (ruled lines) made on or within a glass surface, consisting of a series of rectangular pieces of alternating opaque areas and translucent spaces. In each set of grids 701a-701d as one embodiment of the present invention, the spacing between the edge of one line in the set of lines (scores) and the edge of the next line is 0.01 ". And the width of each score line is 0.005 ″.
In this embodiment, each print line starts every 0.0025 ", so that four pairs of print media are placed between each pair of adjacent lines of the Ronchi grid. The configuration of the Ronchi grid is approximately the same as that of the tick mark, and since the preferred embodiment has a print dot size of about 0.005 ", the dark portion of the tick mark can be printed with a width of one dot. For example, the width of each dark part of a tick mark is 0.005 ". Since the print line starts every 0.0025", printing a small part of every fourth line (commonly called one-on, three-off) The black marks and white spaces are alternately printed (each black mark has a width of 0.005 "and each white space has a width of 0.005"), which is a tick mark track on the print medium. It is formed. In this embodiment, the print line is printed at 12.5 Hz, 25 Hz or 50 Hz (determined by the user).

As described later, the Ronchi gratings 701a,
01b, 701c, 701d (FIGS. 13, 14,
7, FIG. 18) generates a "quadrature signal (a signal that is 90 degrees out of phase)" to start each print line.

To start plotting at a desired print line, the SOP signal 130 (FIGS. 3, 10, and 11 (a) to
11 (c), 12 (a) to 12 (e)) and the quadrature signals (FIGS. 22 and 23) are separately generated, and plotting on the print medium 128 is started by the SOP signal 130. Each time the SOP signal is generated, a one-line plot is started with the quadrature signal. First, SOP signal 1
30 (FIG. 3) will be described.

FIGS. 1 and 2 show the SOP mark 111 of the print medium 128 in relation to the opening 115 of the sensor assembly 700 (FIGS. 17, 18 and 19) containing the optical sensors OP1 to OP6. The sensor assembly 700 is attached to the structure of the electrostatic printer. When the SOP mark 111 of the print medium 128 passes through the opening 115, the optical sensors OP5 and OP6 (FIG. 2) pass through the portions 115t and 115b of the opening 115, A change in light reflected from the print medium 128 caused by the passage of the SOP mark 111 is detected. SOP mark 11 shown in FIG.
FIG. 3 shows a waveform generated when 1 passes through the opening 115.

As shown in FIG. 1, the SOP mark 111 according to the present embodiment is composed of continuous color bands 110l and 110r which are in contrast to the color of the print medium 128. At the position where plotting is started, the three parts 1 of the SOP mark 111 are displayed in a color that is in contrast to the color of the print medium 128.
11a, 111b and 111c are formed. Print medium 12
When 8 is a bright color such as white, color bands 110l and 11
0r and the portions 111a, 111b, 111c are dark colors such as black. The parts 111a and 111c have the center line 1
14 (reference line), extending vertically upward to form a dark rectangular portion in contrast to the lighter color of the print medium, and portion 111b is centered at 11
It extends vertically downwards from 4 and forms a dark colored rectangle which is also in contrast to the lighter color of the print medium.

The LED 126 (FIG. 2) generates a specific optical signal such as an infrared signal, and transmits the generated optical signal to the print medium 12.
8 on the surface 128a facing the sensors OP5 and OP6 and to the portion where the control track 110 is located. The print medium on which the control track 110 is printed is located at a distance C from the LED 126,
Emits not only the surface 128a of the print medium located directly above the LED 126, but also the control tracks 110 and the SOPs provided on the control tracks 110.
It also hits the mark 111. LED 126 and two sensors OP5 (portion 111 of SOP mark 111)
a, sensing light reflected from 111c), OP6 (S
The light reflected from the portion 111b of the OP mark 111 is sensed by a sensor assembly 700 (FIGS. 1, 17, and 1).
8, FIG. 19). Sensor O
P5 is adjacent to the portion 115t of the opening 115 (FIG. 1), and the sensor OP6 is adjacent to the portion 115b of the opening 115. The LED 126 (FIGS. 2 and 21)
5 is located in a portion to be the adjacent dark band 110.
Therefore, when the print medium 128 passes through the opening 115 (the movement direction of the print medium is indicated by the right-pointing arrow 116 in FIG. 1), the sensor OP6 reflects the LED 1 reflected from the print medium.
26 light are sensed.

The difference signal 130 (FIG. 3) is supplied to the sensor OP
5 shows relative changes in the intensity of light received by OP6. The difference signal 130 is (output signal of sensor OP6) − (output signal of sensor OP5). The dark band 110 of the print medium 128 is the sensor OP
5, the level 130l of the signal 130 is zero at the time of symmetrical matching with OP6. Sensor is control truck 11
If properly matched to zero, the portion 130l or 130r of the waveform 130 will be zero. In the event of a mismatch, the signal 130l will not go to zero and the servomechanism will work to align the print head and thus the sensor to the control track, and the signal 130l will go to zero. In this embodiment, there are two control tracks 110, one on each of the right and left edges of the print media 128. If the print medium 128 is displaced in the horizontal direction, the left signal 130l and the right signal 130l deviate from zero by the same amount in the same direction, and the servo mechanism operates to print.
Align the head with the control track. However, if the print medium 128 expands or contracts, the left signal 130l
And the right signal 130l deviates from zero in the opposite direction, in which case the servo mechanism does not work.

When the dark portion 111a of the SOP mark 111 passes through the sensor OP5, the amount of light reflected from the print medium 128 is reduced.
Senses. Accordingly, the difference signal 130 (FIG. 3) rises from the value represented by the portion 130l of the waveform 130 to a positive value (level B) corresponding to the portion 130b of the waveform 130; the light background of the print medium 128 is the SOP mark The straight line replacement (li
near replacement) by the sensor OP6
This rise occurs because the output signal of the sensor OP5 increases and the output signal of the sensor OP5 decreases linearly (indicated by the positive slope of the portion 130a of the curve 130). Print medium 12
8 moves rightward in the direction of arrow 116 and the opening 11
5, the dark portion 111a of the SOP mark 111 passes through the portion 115t of the opening 115, the output signal of the sensor OP5 starts rising, and the difference signal (OP6-OP5) has a negative gradient shown by the portion 130c of the curve 130. ) Decreases. The flat portion 130b of the curve 130 is (width Wm of the dark portion 111a of the SOP mark 111)-(opening 11
5 is the width Ws) of the portion 115t. Needless to say,
The width Wm of the portion 115 t of the SOP mark 111 is
5 is smaller than the width Ws of the portion 115t, the waveform 13
The zero portion 130b still has a finite length, but constant light is reflected from the light color portion of the print
Since the light reaches the sensor OP5 through the fifteenth part 115t, the level difference between the part 130l and the part 130b of the waveform 130 becomes small. The flat portion 13 is formed only when the width Wm of the portion 111a and the width Ws of the portion 115t of the opening 115 are the same.
0b disappears. In this embodiment, Ws = 0.0
5 "and Wm = 0.07".

The dark portion 11 of the SOP mark 111 (FIG. 1)
When the left edge of 1a starts to pass through the portion 115t of the opening 115, the right edge of the dark portion 111b of the SOP mark 111 becomes the opening 1
15 (FIG. 2) begins to pass through sensor OP6 behind portion 115b. Thus, the difference signal 130 decreases at twice the speed at which the dark portion 111a of the SOP mark 111 rises when passing through the opening 115 and the sensor OP5. Therefore, the slope of the portion 130c of the curve 130 in FIG. 3 is twice the slope of the portion 130a of the curve 130. The dark portion 111a of the SOP mark 111 has an opening 115
When the dark portion 11b of the SOP mark 111 comes to the portion 115b of the opening 115, the difference signal 130 becomes level A (the portion 130 of the curve 130).
d). Dark portions 111a and 111 of the SOP mark 111
If the contrast between b, 111c and the background color of the print medium 128 changes, the sensitivity (relative position) of the sensor to the tracking line 110 changes, and S
There is a difference between the light hitting the dark portions 111a and 111c of the OP mark 111 and the light hitting the portion 11b of the SOP mark 111, and the absolute values of the levels A and B differ.

If the print medium 128 advances further in the direction of arrow 116, the sensor OP5
11c starts to be detected. During this time, the portion 111b of the SOP mark 111 passes through the portion 115b of the opening 115, and the amount of light reflected from the print medium 128 to the sensor OP6 gradually increases. In response, difference signal 130 begins to rise at the rate indicated by portion 130e of curve 130 (FIG. 3). The slope of portion 130e is positive, but the absolute value is the same as the slope of portion 130c. When the dark part 111b of the SOP mark 111 has passed through the part 115b of the opening 115 and the dark part 111c comes to the part 115t of the opening, the difference signal 130 (FIG. 3) again reaches a positive value indicated by the part 130f of the curve 130. . As the dark portion 111c passes through the portion 115t of the opening 115, the difference signal 130 starts to decrease (part 130g), and again the portion 1 of the curve 130
The level indicated by 30r is reached.

One important feature of the present invention is that, in the present embodiment, the crossover point 130p is defined by one half of the portion 111b of the SOP mark 111 and the portion 111c.
Is the time when one half of the
The portion 130e of 30 is the positive displacement peak value A of the difference signal 130.
And the reference level set by the negative displacement peak value B. Crossover point 13
0p is the sensitivity and position of the sensor, the print media 128
A portion 111a of the SOP mark 111 in contrast with the background color of the light reflected from the print medium 128;
It may or may not be 0 volts depending on various parameters such as the color of 111b, 111c and the intensity of light reflected from the same. Therefore, in the present invention,
Crossover point 130p considering system uncertainty
Is automatically set using the three-part SOP mark 111. The exact mathematical relationship will be described later with reference to FIG.

FIG. 4 shows a block diagram of the circuit of the system of the present invention. The detailed circuit shown in FIG. 9 will be described later. FIG. 4 shows the uncertainty of the color contrast between the print medium background and the SOP mark 111, the uncertainty of the change in the sensitivity of the sensors OP5 and OP6, and the sensors OP5 and OP6 with respect to the tracking line 110.
SOP mark 11 that generates an SOP signal at an accurate position of the print medium 128 regardless of the uncertainty of the position of the SOP mark 11
1 illustrates the principle of operation.

As shown in FIG. 4, the sensors OP5, OP5
The output signal of No. 6 is subtracted in the adding circuit 141 to become the difference signal 130 described above. The difference signal 130 is sent via a line 142 to a node 142a, from which the line 143
a to the positive peak detection / holding circuit 144a via
The signal is sent to a negative peak detection / holding circuit 144b via a line 143b. The peak detection / holding circuit used in the system of the present invention is known, and only one example will be described later with reference to FIG. Output signals of the positive peak detection / holding circuit 144a and the negative peak detection / holding circuit 144b are sent to the addition circuit 147 via lines 146a and 146b, respectively. The addition circuit 147 is a peak detection / holding circuit 1
Generate a signal proportional to the algebraic sum of the peaks detected by 44a, 144b and send it over line 148. Since the peak detected by the peak detection / holding circuit 144a and the peak detected by the peak detection / holding circuit 144b have opposite polarities, the line 1
The signal sent via 48 is proportional to the difference between the absolute values of the two peaks. The difference signal on line 148 is sent to the positive input of comparison circuit 149. The signal sent over line 148 represents the difference level, and thus represents the crossover point 130p (FIG. 3). At the same time, the output signal of the difference signal generation circuit 141 (signal 130 in FIG. 3) is sent directly via line 145 to the negative input of the comparison circuit 149. If the reference signal sent via the line 148 matches the output signal of the difference signal generating circuit 141 sent via the line 145, the comparison circuit 149 generates an output signal, and the signal is output via the line 150. send. The signal sent from comparison circuit 149 via line 150 is the SOP signal, which initiates plotting of print media 128. Since the comparator 149 compares the level of the signal sent via the positive input line 148 with the waveform 130 sent from the difference signal generation circuit 141 via the line 145, the SOP signal is output from the portion 115t of the opening 115. , 115
b and thus the uncertainties of the sensors OP5, OP6,
A change in the color of the SOP mark 111 with respect to the background of the print medium 128, a change in light detected by the sensors OP5 and OP6, a change in specifications of the sensors OP5 and OP6, and the like.
It is not affected by various system parameters which influence the strength of the signals generated by the sensors OP5 and OP6. In summary, the circuit of FIG. 4 automatically considers these parameters and normalizes the SOP signal by generating a parameter reference signal to remove (no
rmalize).

FIG. 5A shows uncertainties such as a change in the reflectance of the print medium 128, an imbalance between the sensitivity and the specifications of the sensor, and a change in the color of the two-part SOP mark as the prior art. , OP6 on the output signal. The output signals of the sensors OP5 and OP6 are not quadrangular but triangular, and reflect the difference in the width of the SOP mark in relation to the sensor opening. Referring to FIG. 1, the triangular waveform corresponds to the case where the widths Wm and Ws are equal. SOP mark 211 as prior art shown in FIG.
Has a clear color contrast with the background medium 128. The SOP mark 211 has two parts 211
a, 211b, and portions 211a, 211b
Are both control tracks 11 as preferred embodiments of the present invention.
The height of the control track 210 is the same as 0. Part 211
a, the height Hm of 211b is also the sensor field (sensor)
field) less than Hs. However, the SOP mark 21
1 indicates that the SOP signal is generated due to system uncertainties such as a deviation from a perfectly equidistant position from the center line of the sensor, a change in illuminance, a change in contrast of the SOP mark 211 with respect to the background, and an unbalance in sensor sensitivity. The SOP mark 211 is less reliable in generating the SOP signal because it occurs at the wrong time.

One improvement of the system of the present invention when compared to the prior art system is that the SOP mark 211 extends above and below the centerline 114 (reference line), and 211a, 2
The height Hm of 11b is larger than the height of the sensor field Hs. This is shown in FIG. In FIG. 7, the height of each part 211a ', 211b' of the SOP mark 211 'is Hm. As described later, (1) Hm is Hs (opening 1
15 height) and (2) control track 21
The displacement of the sensor with respect to the center line 214 of 0 'is Hm.
If the difference is smaller than the difference between the SOP mark 211 'and Hs, the detection does not depend on the deviation. But S
Even in the case of the OP mark 211 ', the sensitivity of the sensor is unbalanced, the contrast between the print medium and the SOP mark changes,
The problem of inaccuracy in the generation of the SOP signal due to changes in the reflectance of the print medium and the like remains. The signal represented by the waveform 201 is a difference signal between the output signals of the sensors OP5 and OP6 generated by the SOP mark 211 ′ moving in the direction of the arrow 216 together with the print medium 128.

Therefore, the two-part SOP mark 21 having a weak contrast between the SOP mark and the background color is used.
The signal level of the waveform 202 generated by 1 ′ is lower than the waveform 201. If two sensors (sensors OP5 and OP6 in FIG. 2) for detecting the SOP mark are completely matched and are located at the same distance from the control track 110 (see FIG. 1), two waveforms 201 and a zero intersection point 201p, 20
2p matches. However, if the sensitivities of the two sensors are not balanced, as shown in the figure, the zero crossing point 202p of the waveform 202 is displaced to the right from the zero crossing point 201p of the waveform 201 by an amount corresponding to the unbalance. SOP mark 211
′ Are portions 111a, 1 of the SOP mark 111 (FIG. 1).
It comprises two portions 211a 'and 211b' corresponding to 11b.

The portion 211a of the SOP mark 211 is SO
The sensor OP is smaller than the portion 211b 'of the P mark 211.
5, because it is close to OP6, the difference signal waveform 202 (OP5-O
P6) rises by an amount corresponding to the amount of decrease in the intensity of the output signal of the sensor OP6 when the portion 211a 'of the SOP mark 211 passes through the sensor OP6 as the print medium moves in the direction of the arrow 216. When the portion 211b 'of the SOP mark 211 enters the field of the sensor OP5, the output signal of the sensor OP5 decreases, and
When the portion 211a 'of the P mark 211' has passed through the field of the sensor OP6, the output signal of the sensor OP6 increases, and the difference signal 202 (OP5-OP6) decreases from a positive value to a negative value. SOP mark portions 211a ', 211
Difference signal 2 for some reason, such as a change in the color of b '
If the positive peak value A 'of 02 becomes larger than the negative peak B' of the difference signal waveform 202 '(FIG. 5A), the zero-crossing point 202p of the waveform 202 is displaced later. The same is true when the sensitivity of the sensor is unbalanced. On the other hand, a waveform 201 indicates a state where the output signals of the sensors OP5 and OP6 are balanced.

S at which zero-crossing point 201p of waveform 201 occurs
Fig. 5 shows the transition (tran-sition) of the OP signal.
(B). Needless to say, if the zero crossing point of the waveform 201 is displaced with time, the transition of the SOP signal is also displaced with time, and the SOP signal is changed to the tick mark track 218.
With respect to the tick mark. As shown in FIG. 5B, if the zero-crossing point of the waveform 202 in FIG. 5A is displaced, the SOP signal of the SOP signal is moved by the time required for the print medium to move a distance corresponding to 3/4 pitch of the tick mark. The time of occurrence shifts. The tick mark pitch corresponds to a print line group consisting of four print lines.
Since the plot is set to start on the same one of the print lines, the displacement SOP signal that missed the plot start print line will cause the printer to
Plot two print lines late. In case of high resolution plotting such as printed circuit board, this deviation (diff
erence) is one important condition for ensuring a high quality plot.

In the two-part SOP mark 211 '(FIG. 7), the zero crossing point 202p (FIG. 5 (a)) is one-half of the distance between the common points of adjacent tick marks from the desired zero crossing point 201p. It is shifted by the distance that exceeds. The causes include changes in the color contrast between the two parts of the SOP mark 211 and the background of the print medium, and the sensors OP5 and OP6 with respect to the tracking line 110.
The change of the relative position of.

The three-part SOP mark 111 (FIG. 1) of the present invention shown in FIG. 8 solves the above-described difficulties of the two-part SOP marks 211 (FIG. 6) and 211 '(FIG. 7), and is indispensable. Generate the SOP signal at the correct time. As shown in FIG. 8, the center line 114 of the three-part SOP mark 111 (FIG. 1) of the present invention is shifted by a distance D from the center line 214 between the sensors OP5 and OP6. Hs and Ws are respectively the height and width of the portion 115t of the opening 115 in a direction perpendicular to the direction 116 (FIG. 1) in which the print medium 128 moves along the sensors OP5 and OP6. Hm, W
m is the height and width of the SOP mark 111 in a direction perpendicular to the 116 direction. Hm is the height measured from the center line 114 of the SOP mark 111.

Assume the following three: (i) the response of each sensor OP5, OP6 is uniform throughout its area; (ii) SOP mark 111 and control track 110
(Iii) SOP mark 111 and control track 110
The illuminance of the image of the SOP mark 111 is the sensor OP5,
It does not change with time when passing through OP6. The sensor OP5 in the portion 115t of the opening 115 outputs the output signal Ra for the background portion (bright portion) of the print medium.
w (volts / area) and an output signal Rab (volts / area) for the dark part (image part) are generated.
The sensor OP6 in 15b outputs an output signal Rbw (volt / area) for the background portion (light portion) of the print medium.
And an output signal Rbb (volt / area) for the dark part (image part).

Therefore, if Hm−Hs>D> 0 (ie, if the deviation of the SOP center line 114 from the sensor center line 214 in FIG. 8 is as shown in FIG. 8 and smaller than Hm−Hs), 116 print media
Part 111a of the SOP mark
OP5 when the sensor reaches the portion 115t of the opening 115
Is the sum of the response to the background and the SOP mark exposed to the sensor OP5 due to misalignment: OA = (Ws) (D) (Raw) + (Ws) (Hs −
D) (Rab) This is a part (area DW) of the background of the print medium.
s) has been exposed to the sensor OP5, and
This means that the OP mark portion 111a occupies the area that should be completely filled. Further, the intensity OB of the output signal of the sensor OP6 at this time is given by the following equation: OB = (Ws) (Hs) (Rbw) This is the non-image portion (white portion (background)) (area) of the print medium 128. WsHs) completely fills the field of the sensor OP6.

The difference signal (signal 130 previously described with reference to FIGS. 1 to 3) (OB-OA) is therefore given by: POS = (Ws) [(D) (Rab)-(D) (Raw) + (Hs) (Rbw)-(Hs) (Rab)] (A1) This represents a positive peak of the signal POS when the SOP mark 111 is displaced in the positive direction with respect to the sensor position. .

On the other hand, when the SOP center line 114 is displaced in the opposite direction toward the opposite side of the sensor center line 214 and the amount of negative displacement D is smaller than Hs−Hm, (0>D> Hs −Hm), the output signal of sensor OP5 is given by: OA = (Ws) (Hs) (Rab) This means that the SOP mark portion 111a completely fills the opening 115 portion 1115t. I do. The output signal of the sensor OP6 is given by the following equation: OB = (Ws) (Hs + D) (Rbw)-(Ws)
(D) (Rbb) This means that a part (area-WsD) of the SOP mark is exposed to the sensor OP6 (D is negative in this case). And the portion 115t of the opening 115
Is given by the following equation: POS = (Ws) [(D) (Rbw)-(D) (Rbb) + (Hs) (Rbw)-(Hs) (Rab)] (A2) The case where the portion 111b of the SOP mark 111 reaches the portion 115b of the opening 115 can be similarly considered.

Also in this case, in the case of a positive displacement within the range of Hm-Hs>D> 0, OA = (Ws) (Hs-D) (Raw) + (Ws)
(D) (Rab) OB = (Ws) (Hs) (Rbb), where a part (area WsD) of the portion 111b of the SOP mark 111 is exposed to the sensor OP5,
The packaging of the print medium 128 is the part 1 of the opening 115.
It means that it occupies the rest of 15t. SO
The portion 111b of the P mark 111 corresponds to the portion 11 of the opening 115.
5b is completely filled, so the difference signal POS is given by: POS = (Ws) [(D) (Raw)-(D) (Rab) + (Hs) (Rbb)-(Hs) ( (Raw)] (B1) This is because the portion 111b of the SOP mark 111 has the opening 11
5 represents the negative peak of the difference signal at the time of the positive displacement D when it comes to the portion 115b.

OA = (Ws) (Hs) (Raw) OB = (Ws) (Hs + D) (Rbb)-(Ws) In the case of a negative displacement D in the range of 0>D> Hs-Hm.
(D) (Rbw). In this case, a part (area WsD) of the print medium is exposed to the sensor OP6, and the SOP mark 111
Portion 111b occupies the remaining portion of the portion 115b of the opening 115 above the (Ws) (Hs + D) portion.

Therefore, in this case, the difference signal POS is given by the following equation: POS = (Ws) [(D) (Rbb)-(D) (Rbw) + (Hs) (Rbb)-(Hs) (Raw) (B2) This represents a negative peak of the difference signal at the time of the negative displacement D.

In the case where Hm−Hs>D> 0, the position 120 (dotted line in FIG. 8) of the SOP mark 111 indicates the sensor OP.
5, the difference signal POS is at the center of the OP6 field.
Is given by: POS = 1/2 (Ws) [(D) (Rab)-(D) (Raw) + (Hs) (Rbw)-(Hs) (Rab)] + 1/2 (Ws) [(D) (Raw)-(D) (Rab) + (Hs) (Rbb)-(Hs) (Raw)] = 1/2 (Ws) (Hs) (Rbb-Rab + Rbw-Raw) E1) Also in the case of 0>D> Hs−Hm, POS = １ ／ (Ws) (Hs) (Rbb−Rab + Rbw−Raw) (E2) The position 120 of the SOP mark 111 is the sensor OP5 and the sensor OP5.
When in the center of the field at P6, this situation is equivalent to the situation corresponding to when the portion 111a is adjacent to the sensor for each sensor exposed on the right, and the portion 111b for each sensor exposed on the left. It is equivalent to the corresponding situation when it is adjacent to the sensor,
The results E1 and E2 are obtained. In this position, the difference signal PO
S is independent of displacement D and is zero if the sensor responds to reflectance and the illuminance of the image and background is balanced. Therefore, the improved two-part SOP mark 211 ′ of FIG. 7, which generates the SOP signal at the zero crossing point,
Although the problem of misalignment of the SOP mark from the center line 114 as the prior art has been solved, problems such as changes in the illuminance of the print medium, changes in reflectance, and unbalance in the sensitivity of the sensor have not been solved. The portion 111c (FIG. 1) of the SOP mark 111 of the present invention is the same as the portion 111a. Therefore, at the time of the positive / negative displacement D, the portion 111a
(A1) and (A2) at the point 115t of
(A1) and (A2) also when the portion 111c reaches the portion 115t of the opening 115 at the same positive / negative displacement D. Actually, as described later, the portion 111b of the SOP mark 111
Only the first half 111c-1 of the portion 111c of the SOP mark 111 adjacent to the SOP mark 111 needs to exist.

As described above with reference to FIG. 1, the difference signal 130 (SOP) has the positive peak value B when the portion 111a comes to the portion 115t of the opening 115, and the portion 111b
Reaches a portion 115b of the opening 115, the negative peak value A is reached.

Therefore, in the system of the present invention shown in FIG. 9, the reference signal is の of the sum of the positive peak value and the negative peak value; therefore, Hm−Hs>D> 0
In the case of, V _ref = １ ／ (Ws) [(D) (Rab) − (D) (Raw) + (Hs) (Rbw) − (Hs) using equations (A1) and (B1). (Rab) + (D) (Raw)-(D) (Rab) + (Hs) (Rbb)-(Hs) (Raw)] = 1/2 (Ws) (Hs) (Rbb-Rab + Rbw-Raw) (C1) Similarly, when 0>D> Hs−Hm, the equations (A2) and (B
Using 2), V _ref = (Ws) [(D) (Rbw) − (D) (Rbb) + (Hs) (Rbw) − (Hs) (Rab) + (D) (Rbb) − (D) (Rbw) + (Hs) (Rbb) − (Hs) (Raw)] = １ ／ (Ws) (Hs) (Rbb−Rab + Rbw−Raw) (C2) Therefore, equation (C1) , (C2), the reference voltage _Vref is the same when the SOP mark 111 is displaced in any direction D from the center line 214 (FIG. 8), and is therefore independent of the displacement amount D. Furthermore, if the sensor responses match, that is, if both sensors respond similarly to the image part (dark part) and the background part (light part), (Raw = Rbw, Rab = Rbw)
bb) The reference voltage V _ref is zero.

This time, the portion 111 of the SOP mark 111
b second half 111b-2 and first half 1 of portion 111c
Consider a case where 11c-1 comes to the opening 115 (that is, a case where the position 121 in FIG. 8 is at the center of the portions 115t and 115b of the opening 115). The output signal of the sensor OP5 at the time of the positive displacement D in the range of Hm−Hs>D> 0 is given by the following equation: OA = １ ／ (Ws) [(Hs−D) (Raw) + (D) (Rab) )] + 1/2 (Ws) [(D) (Raw) + (Hs-D) (Rab)] = 1/2 (Ws) (Hs) (Raw + Rab) This is the difference between the parts 11b and 111c of the SOP mark 111. It represents the combined partial contribution.

Similarly, OB = 1/2 (Ws) (Hs) (Rbb + Rbw) Therefore, the difference signal POS is given by the following equation: POS = OB-OA = 1/2 (Ws) (Hs) (Rbb-Rab + Rbw) −Raw) (D1) 0>D> Hs−Hm Similarly, at the time of negative displacement D, OA = １ ／ (Ws) (Hs) (Rab + Raw) OB = １ ／ (Ws) [( Hs + D) (Rbb)-(D) (Rbw)] + 1/2 (Ws) [(Hs + D) (Rbw)-(D) (Rbb)] = 1/2 (Ws) (Hs) (Rbb + Rbw) POS is given by: POS = １ ／ (Ws) (Hs) (Rbb−Rab + Rbw−Raw) (D2) Thus, at this point, regardless of the direction of displacement, the portion 111b of the SOP signal 111 is Half and part POS signal when half each me to the other sensor 111c becomes V _ref (formula (C1), (D1) refer). Therefore, the expression (C
1) and (C2), the reference voltage _Vref is defined as described above, and the SOP signal is generated when the difference signal POS reaches the reference voltage _Vref . Sensors OP5 and OP6
Regardless of the relative sensitivity of the SOP mark 111, an SOP signal is generated whenever the equal portion of the second portion 111b and the third portion 111c of the SOP mark 111 comes to the opening 115. Thus, the object of the present invention to reliably generate the SOP signal even when the position of the sensor is displaced or the sensor signal is unbalanced is achieved. One preferred embodiment of the present invention will now be described in detail with reference to FIGS.

In this embodiment, two tracking lines, one on each side of the print medium, are provided.
10 (FIG. 1). Each tracking as described above
Line 110 is a continuous tick mark zone 720 (FIG. 1).
Adjacent to 3). The print medium 128 is the sensor OP1
The tracking line 110 is printed by the black printhead above the sensor as it moves toward OP6 (FIG. 13). The black print head simultaneously prints a pair of SOP marks 111 (FIGS. 1 and 8), one on the left and one on the right, of the print medium 128 as part of the tracking line 110. Prior to the start of the plot, the print medium 128 is aligned within one tick mark range by the first pair of SOP marks and the servo mechanism. The servo mechanism corrects the angle of the print head based on the difference between the detection times of the first pair of left and right SOP marks 111. The SOP is started by the second pair SOP mark 111. Actually, one S in the second pair SOP mark
The SOP starts only with the OP mark.

The quadrature phase signal sensors OP1, OP2, O
P3, OP4 and SOP mark sensor OP5, O
P6 is both housed in the sensor assembly 700 (FIGS. 17, 18 and 19). The circuit is composed of two circuit boards, a sensor circuit board A (the circuit in FIG. 15) and a sensor circuit board B (the circuit in FIG. 16). Because two tracking lines 110 are used, two sets of quadrature signal sensors O
P1 to OP4, two sets of SOP mark sensors OP5,
OP6 (one set each on the left and right). L of each sensor
Light generated by ED is reflected from the print medium 128. The image printed on print medium 128 determines the intensity of light reflected toward the sensor.

As shown in FIG. 15, the sensor circuit board A is composed of three functional blocks: a sine block, a cosine block, and an SOP block. The sensor circuit board B shown in FIG. 16 is a part of each sine block and cosine block. The sine and cosine blocks have the same structure because they perform the same function. Each block has two sensors (the sine block has OP1 and OP2, the cosine block has OP3,
OP4, and SOP blocks have OP5 and OP6). Further, in the present embodiment, as described above, six sensors (OP1 to OP
6) are all housed. Each sensor OP1 to OP
Reference numeral 6 includes a phototransistor and an LED.
The sensor may be, by way of example, MTRS9070 (LB) Infrared / Photo Darlington from Marketch Corporation (NY). As shown in FIG.
070 (LB) package includes an LED section 740, a phototransistor section 741, and leads 742-1 to 74.
2-4 (four in total). LED section 740
The surface of the phototransistor portion 741 transmits light almost completely. However, in the SOP block (FIG. 21),
Only one of the two sensors actually works. 21, two sensor packages shown in FIG. 20 are used as sensors OP5 and OP6. The LED 126 of one package is located between OP5 and OP6. The center line of the opening 115 is located directly below the LED 126. Therefore, the aperture 1 emitted from the LED 126
Light passing through 15 produces substantially identical images (intensity and angle of reflection) of tracking line 110 at each phototransistor of sensors OP5 and OP6. The lead LSRV (FIG. 15) is connected to an external circuit (not shown) for detecting the reflectance of the print medium 128. Print medium 1
28 depends on the material of the print medium 128,
White paper has higher reflectivity than many plastic films. The external circuit adjusts the intensity of the light emitted by the LED of the SOP sensor by adjusting the current passing through the terminal LDRV.

The sensor circuit board A shown in FIG. 15 uses two identical circuits 620c and 620d to output two output signals RA.
S, -RAS is generated. As described later, the SOP signal is generated by the output signals RAS and -RAS generated by the sensors OP5 and OP6 when the SOP mark 111 passes,
It supplies vertical position information to the moving print medium.

Next, circuits 620c and 620d for generating RAS and -RAS signals will be described. When the sensor assembly 700 is located on the left side of the moving print medium, the signals are referred to as LRAS and -LRAS; these two signals are added together and the LF POS of the SOP generation circuit described later with reference to FIG. Generate a signal. (RRA on the right
Generate RT POS with S and -RRAS).

As shown in FIG. 15, the current of the collector lead 602d of the phototransistor Q6 is
8 is modulated by the light reflected from the light. The output current of the collector lead 602d of the phototransistor Q6 is a resistor 603d, a capacitor 605d, and an operational amplifier (op a
mp) 604d and is processed by the low-pass filter to become the voltage signal -RAS, and the resistor 618d
Pass through. In OP6, pin 1 is connected to the + 12V power supply and the anode of D6, pin 2 is connected to the signal LDRV of pin 12 of sensor circuit board A, and pin 3 is the input lead of low-pass filter 601d. This is an output lead for sending an output signal via the lead 602d, and the pin 4 is connected to a -12V power supply.

Almost the same circuit for processing the output signal of phototransistor Q5 shown in FIG. 15 generates the + RAS signal. + RAS signal generating circuit 620c;
The circuit 620d for generating the S signal includes the sensors OP5, O5
The connection of P6 is different. LED5 of sensor OP5
Is not connected and does not function; the reason will be described later with reference to FIG.

Referring to circuit 620c, low pass filter 601c, which receives the output signal of lead 602c (pin 3) of OP5, has a reverse input lead toward op amp 604c and an output lead out of op amp 604c. On the other hand, a resistor 603c and a capacitor 605c are connected in parallel. The output lead 602c of the phototransistor Q5 is connected to the reverse input lead of the op amp 604c. The non-reversing input lead of op amp 604c is grounded. The low-pass filter 601c converts the optical modulation current signal sent via the lead 602c into the lead 619c of the output terminal of the opamp 604c.
And converts it into a voltage to remove high frequency environmental noise in the signal. In order to make the voltage output signal almost zero when adding RAS and -RAS to generate the LF POS or the RT POS when the light intensity incident on the sensors OP5 and OP6 is almost the same, the circuit 601d, 6
The specifications of 01d must be the same. Therefore, the resistance value of the resistor 603c is set at the time of design, but the resistance value of the resistor 603c is determined at the time of testing so that the specifications of the circuits 601d and 601d are the same. This scheme must be followed because the cost of adjusting the sensor specifications is higher than the cost of adjusting resistor 603d to make the overall response the same.

Lead 6 of low-pass filter 601c
The output signal of 19c is processed by the resistor 618c to become the output signal + RAS. The difference between the + RAS signal and the -RAS signal becomes the LFPOS signal or the RT POS signal. As described above, in the substantially same circuit shown in FIG.
Generate S.

FIG. 9 is a detailed diagram of a circuit for generating an SOP signal by sensing the SOP mark shown in FIG. 1 and the waveform 130 shown in FIG. S for generating left SOP signal
OP circuit 3A and SOP circuit 3 for generating right SOP signal
There is A '. As described above, the two SOP signals measure and adjust the angle of the print head with respect to the print medium 128. In FIG. 9, the upper SOP circuit 3A
And the lower SOP circuit 3A 'have the same operating principle,
Only the upper SOP circuit 3A will be described.
The same components of the circuits 3A, 3A 'have the same numbers,
(′) Is added to the component number of the circuit 3A (example:
Resistors 300a, 300a ').

The circuit 3A includes a plurality of functional blocks 144a,
144b, 149, and 151. These functional blocks correspond to the functional circuit of FIG. 4, and the components of the circuit of FIG. 9 corresponding to the functional blocks of FIG. Show. Therefore, peak detection /
The holding circuits 144a, 144b and the comparator 149 are surrounded by the same numbered lines. The hysteresis circuit 151 is included in the comparison circuit 149 of FIG. 9, but is not shown in FIG. As will be described later, the hysteresis circuit 151
When the first portion 111a, 111b of the OP mark 111 is sensed, a bias voltage is supplied to the circuit of FIG. 9 to prevent the generation of the SOP signal until the difference signal 130 switches from the positive peak to the negative peak of the waveform segment 130c (FIG. 3). I do.

Adder circuit 141 (not shown in FIGS. 4 and 9)
Is sent as an input signal LF POS to the circuit 3A via the LF POS lead. A voltage divider constituted by resistors 300a and 300b having the same resistance value attenuates the signal LF POS by half, and
6, 308, and 317 compensate for the attenuation of the LF POS at the node 145 of the signal transmission path. Comparator 149 compares the voltage at node 145 with a reference voltage. The operational amplifier (op amp) 301a of the peak detection / holding circuit 144a has a positive going signal (positive going) of the signal LFPOS of the non-inverting input lead of the op amp 301a.
peak) and a peak detection / holding circuit 144b
The operational amplifier (op amp) 301b follows the negative going peak of the signal LF POS at the non-inverting input lead of the op amp 301b.

The output signal of the op amp 301a is connected to the lead 30
2a to the capacitor 304 from the diode 303a
a to charge the capacitor 304a to the level of the positive peak signal LF POS. Similarly, the signal LF P
After being amplified by the op amp 301b, the OS is sent to the capacitor 304b through the reverse polarity diode 303b, and charges the capacitor 304b to the level of the negative peak signal LF POS.

The analog switch 307 sets the capacitor 3
04a and 304b are discharged. A

[Outside 1]

[0084]

[Outside 2]

[Outside 3]

[0098] The capacitor 304a is
304b is discharged.

The voltages (positive peak and negative peak of the POS signal) stored in the capacitors 304a and 304b are added at a node 148 after passing through a buffer amplifier (voltage follower), and compared via a resistor 313. Sent to the negative input lead of the comparator 315 for comparison stage 1
Enter 49. The positive input lead of comparator 315 is at node 1

[Outside 4]

In the case of-, the input signal LF POS is almost 1 /
Equal to 2. As described above, the signal LFPOS is a difference signal generated by the sensors OP5 and OP6 that sense light reflected from the SOP mark 111 (FIG. 1) of the present invention.

The resistor 30 forming one voltage divider
6, 308, 316, 317 resistance values

[Outside 5]

Sometimes, the setting is made to be about 1/2 of the initial value in the LF POS read. Low-pass composed of capacitor 309 and resistor 306
The filter removes high frequency noise and introduces a delay that matches the delay of the quadrature signal sensor circuit described below, so that the SOP signal generated in the circuit of FIG. Chase. Regarding this delay matching, the sine block and cosine of the quadrature signal sensor circuit of FIGS.
It will be described later in connection with blocks.

The output signal of comparator 315 is passed through digital inverter 320 to node 321 and from there to the input lead of inverter 322 and to control the clock (CP) input lead of flip-flop 318.

Flip-flop 323 receives the output signal of digital inverter 322 and receives the output signal.

[Outside 6]

[0092]

[Outside 7]

[0093]

[Outside 8]

[0094]

[Outside 9]

This time, FIGS. 10, 11 (a) to 11
(C) and FIG. 9 with reference to FIGS. 12 (a) to 12 (e).
The operating principle of this circuit will be described in detail.

As shown in FIG. 10, there are SOP marks on both sides of the print medium 128; FIG. 10 shows the print medium as seen through the print medium toward the sensor as if it were transparent. As described above, there are a total of two sensor assemblies, one on each side of the print medium 128 (FIG. 1), and each sensor assembly has two SOP detection sensors (a left sensor OP5, OP6 and a right sensor OP5 ', OP6
') (FIG. 10). Although each sensor OP5, OP6 has one LED, only one LED actually works and the light emitted by that LED is reflected from the print medium 128. Sensors OP5, OP6, OP5 ', OP
6 'are each oriented correctly with respect to the left and right sides of the print medium. Left and right sensor assembly 700, 700 '
Of the SOP mark detection sensors OP5 and OP6 of each set of the pair, the tracking is performed when the tracking line 110 is aligned with the sensors OP5 and OP6.
Exposure to line 110.

When the SOP mark 111 is detected, two output signals are generated, one on each side of the print medium 128; on the left, OP5 generates + LRAS (401) and OP6 generates -LRAS (402). OP5 ′ generates + RRAS (401 ′) on the right side, and OP6 ′
'Generates -RRAS (402'). This output signal is shown in FIGS. 11 (b) and 11 (a). OP5, OP
6, OP5 'and OP6' output circuits are + LRAS, -L
The principle of generating RAS, + BRAS, -RRAS is shown in FIG.
5 as described above. In normal times, on the left side, by way of example, the SOP mark 111 does not come under the sensor assembly, so the sensor has a width sufficient to cover half of each SOP mark detection sensor (OP5, OP6). Looking at a simple line of 110. Therefore, each SOP mark detection sensor (OP5, OP6) is exposed to the semi-dark portion (tracking line) and the semi-bright portion (background) image, and the output of each sensor is, as shown, between zero volt and V volt. It is an intermediate value between.

First part 111a of SOP mark 111
Enters the sensor field, the exposure rate of the left sensor assembly 700 to the dark image of OP5 and the right sensor assembly OP6 'increases, and the + LRAS signal, -RR
The AS signal approaches zero volts along each of the waveform segments 401a, 410a '. At the same time, OP6 of the left sensor assembly 700 and the right sensor assembly 700 '.
Exposure rate of OP5 'to a perfect bright image increased, and -LR
The AS output signal and the + RRAS output signal approach the peak positive voltage + V along waveform segments 402a and 402a ', respectively. When the central portion 111b of the SOP mark 111 comes over the sensor assembly 700, 700 ', the state is reversed, and the left OP5 and the right OP6' are exposed to a complete clear image, and the sensors OP5, OP6 ' The output signal reaches the positive peak voltage + V along waveform segments 401b, 401b ', respectively. At the same time, the left sensor OP
6 and the right side sensor OP5 'are exposed to a complete dark image, and the output signal is
It decreases to zero volts along 2b '(FIGS. 11 (b) and 11 (a)). Finally, if the last part 111c of the SOP mark 111 is on the sensor assembly 700, 700 ', the same state as when the first part 111a of the SOP mark 111 is on the sensor assembly 700, 700'. And the output signals of OP5 and OP6 'decrease to zero volts along waveform segments 401c and 401c', respectively, and the output signals of OP6 and OP5 'increase to + V volts along waveform segments 402c and 402c', respectively.

In the left sensor assembly 700, OP5
Of FIG. 11 is subtracted from the output signal of OP6.
The LF POS signal indicated by the left waveform 403 in (c) is obtained, and OP6 ′ is output from the right sensor assembly 700 ′.
Is subtracted from the output signal of OP5 'and RT
It becomes a POS signal. The waveforms 403, 403 'are the same as the difference signal 130 as described in detail above with reference to FIGS. FIG. 12A shows the LFPO signal because the SOP signal is similarly generated on both sides of the print medium 128.
This indicates either the S signal or the RT POS signal. The time scale and the voltage scale in FIG. 12A are enlarged for easy viewing.

[Outside 10]

FIG. 12 (a) shows the LF POS signal appearing on the positive lead of the comparator 315 (FIG. 9) when not performed. In the positive lead of the comparator 315, the LF POS signal is attenuated to 入 力 of the input value by the function of the voltage divider constituted by the resistors 306, 308, 316 and 317 provided in this route.

[Outside 11]

Since the signal is added to the signal, the positive read actual input signal of the comparator 315 becomes a signal as shown by the tick line waveform 405 in FIG. 12B. The output signals of the +/- peak detection / hold circuits 144a and 144b are shown in FIG.
The waveforms 407 and 408 of FIG. The sum of the two outputs is waveform 406, which is the signal at node 148 (FIG. 9) of the negative input lead of comparator 315.

Initially, the peak holding capacitor 304
a and 304b are discharging and the hysteresis

[Outside 12]

The log switch 307 is reset, and the hysteresis flip-flop 318 is reset.

[Outside 13]

[0104]

[Outside 14]

The initialization for preparing the preparation is performed.

First part 111a of SOP mark 111
If the signal reaches the sensor, the input signal LF POS (FIG. 12)
(A), FIG. 12 (b)) goes positive along the waveform segment 407a, and the positive peak detection / holding circuit 144a sets the input signal L to ま で of the positive change of the waveform segment 402a.
Follow F POS and reach peak value + V / 2.
The peak value is + V / 2 due to the function of the voltage divider constituted by the resistors 300a and 300b.

When the central portion 111b of the SOP mark 111 reaches the sensor assembly 700, the input signal LF PO
S (FIG. 12 (a)) transitions through zero along waveform segment 404b to a negative peak value. Also in this case, the negative peak detecting / holding circuit 144b again applies a half of this negative change to the waveform segment 408a (FIG. 12B) due to the function of the voltage divider constituted by the resistors 300a and 300b.
Along -V / 2.

Last part 111c of SOP mark 111
Are sensors OP5 and OP6 (or OP5 'and O
Upon reaching P6 '), the input signal 404 returns to a positive peak through zero along waveform segment 404c. During this change of the input signal LF POS, the crossover point 404
SOP signal (LF SOP or RT SO
P) occurs.

[Outside 15]

The signal on the force lead is set to a "high" voltage state equal to the initial voltage of waveform 405 and the SOP mark 1
11 are ready for detection. Negative peak detection / hold circuit 144
Since b is initially set to zero volts, the signal on the negative input lead reaching comparator 315 (node 148)
Of the waveform segment 406 due to the action of the voltage divider formed by the resistors 312a and 312b.
It rises to 1/4 of the peak value V along a. At this point, the signal appearing on the positive input lead that has reached comparator 315 is, as shown by waveform 405, a 1 / 2LF POS
Hysteresis F

[Outside 16]

[0110]

[Outside 17]

[Outside 18]

This added voltage keeps the voltage on the positive input lead of comparator 315 higher than the voltage on the negative input lead of comparator 315. Therefore, during this time, the state of the comparator 315 is not switched, and erroneous generation of the SOP signal is prevented. If there is no added voltage during a portion of this time, the LF POS and the voltage at node 148 are both substantially zero volts, and even a small change in environmental noise can cause the state of comparator 315 to switch. Only during the transition to the central portion 111b of the SOP mark 111, the input signal swings sufficiently negative, and the state of the output of the comparator 315 switches at the crossover point 404t of the waveform segment 409b. The state of the output of the comparator 315 switches to low at the crossover point 404t of the waveform segment 409b, and when the output reaches zero volt, the hysteresis FF31 is output.
8 is set, and the added bias voltage V _bias for the positive input of the comparator 315 disappears.

When the central portion of the SOP mark 111 has completely passed through the sensor, the LF POS signal is
It swings to a negative peak along 4b. Positive peak detection /
As in the case of the holding circuit 144a, the negative peak detection / holding circuit 144b subtracts one half of this value from the waveform segment 408a.
Along to the -V / 2 level. The output signal of the positive / negative peak detecting / holding circuit is again applied to the node 148.
And sent to the negative input lead of comparator 315. The threshold at which the positive / negative peak voltage detected by the peak detection / holding circuits 144a / 144b is compared with the signal LF POS (waveform 405) halved at node 145 is set. At the crossover point 405p, LFP
If の of the OS signal equals the voltage level at node 148, comparator 315 switches from a low state to a high state along waveform 409d, and STO

[Outside 19]

It goes low along 10a to indicate that an SOP mark has been detected.

[Outside 20]

[0114]

[Outside 21]

Next, a circuit for generating a quadrature signal will be described.

As shown in FIG. 15, the sensors of the sine block are OP1 and OP2. In OP1,
Pin 1 is connected to the + 12V power supply and the anode of LED D1, pin 2 is connected to the cathode of LED D1, grounded through resistor 600a, and pin 3 is connected to the + 12V power supply and the phototransistor Q1. Connected to the collector, with pin 4 connected to the emitter of Q1 and a resistor 600
e. The other terminal of the resistor 600e is connected to another resistor 600f, and the other terminal 600f 'of the resistor 600f is connected in series to pin 3 of the sensor OP2. In OP2, pin 1 is LED
It is connected to the anode of D2, grounded through a resistor 600b, pin 2 is connected to the cathode of LED D2 and the -12V power supply, and pin 4 is connected to the -12V power supply and the emitter of phototransistor Q2. And the pin 3 is connected to the collector of the phototransistor Q3. The resistors 600a and 600d are current setting resistors. The resistance values of the resistors 600a and 600d are ticks.
50% dark image formed by superimposing the mark track at right angles to the Ronchi score lines 701a-d, 50%
The factory is set so that the sensors OP1 and OP2 are exposed to the% bright image. SIN common terminal for 600e and 600f
E output. This output signal 602a is
15 to 16 along the E input lead.

Next, as shown in FIG.
1. The current sent from OP2 to the SINE input (pin 10) via lead 602a is converted to a voltage by a low-pass filter circuit 601a composed of an op amp 606a, a resistor 605a, and a capacitor 607a. Sent through. Capacitor 60
7a and resistor 605a are in parallel with the inverted input and output leads of op amp 606a. op amp
The non-inverting input of 606a is grounded. op amp60
The output signal of lead 609a of 6a,
The output signal of the lead of the pass filter circuit 601a passes through a differentiating circuit composed of a capacitor 608a and a resistor 611a, and a DC component generated by sensors OP1 and OP2 that detect a change in the reflectance of a print medium or a print image is generated. Attenuated. The capacitor 608a of the resistor 611a
The terminal on the opposite side is connected to a + 5V power supply. The capacitor 608a and the resistor 611a form one differentiating circuit. The voltage at resistor 611a is directly proportional to the rate of change of the input signal at lead 609a. Therefore, as described later, since the input signal of the lead 609a is substantially triangular, the voltage of the resistor 611a is a square wave, and the tip (positive) transition coincides with the positive peak of the triangular wave of the lead 609a. Further, the positive level of the same triangular wave voltage of the resistor 611a is the lead 609a (dv / dt).
The negative level is directly proportional to the negative gradient of the input waveform of the voltage of the lead 609a. In addition, since the reflectance of the print medium and the print image is not completely uniform, low frequency (<50 Hz) noise is generated as compared with the signal frequency, which causes erroneous variation in the interval between printed lines. ). A differentiating circuit composed of a capacitor 608a and a resistor 611a attenuates this low frequency noise, thereby improving printing accuracy.

The output signal generated at the junction between the capacitor 608a and the resistor 611a of the differentiating circuit is
0a to the negative input lead of comparator 614a. The positive input lead of the comparator 614a is connected to the resistor 61
The negative input lead is connected to the same + 5V power supply via a resistor 611a. Capacitor 612a is connected to output lead 617a and positive input lead of comparator 614a. An AC hysteresis circuit composed of a capacitor 612a and a comparator 614a provides a glitch (gl) for switching the state of the square wave.
itch) and lead 610a of capacitor 608a
Is converted into a clean square wave with a desired voltage change. The output is +5 through a resistor 613a.
V power supply.

The output signal of the lead 617a of the comparator 614a is sent to a line driver (line driver) 616a, and the pins 7 and 9 of the line driver 616a output the output signal, respectively.

[Outside 22]

Since the cosine block of the sensor circuit board shown in FIGS. 15 and 16 is the same as the above-mentioned sine block, its detailed description is omitted, and pins 3 and 5
Out

[Outside 23]

The structure of the sensor circuit board has been described above, and then the principle of operation of the sine block and the cosine block of the sensor assembly will be described.

As previously mentioned, one preferred embodiment of the present invention is a quadrature signal sensor assembly 700 (FIG. 1).
7) Four sets of Ronchi gratings 701a to 701d
Is carved. FIG. 22 shows the relative position of each grid with respect to the moving tick mark at time t0. In this example, the spacing between tick marks as well as the width of each tick mark is 0.005 inches ("one on,
three off ”configuration. (Dot size is about 0.005 inch). The width and spacing of the opaque lines are almost the same as those of the tick marks. Referring to FIG. 17, four sets of gratings 701a are provided in sensor assembly 700.
Ticks where the first set lattice 701a moves
If the marks are in phase, that is, if each opaque scored line is directly below one tick mark and completely overlaps the tick mark, the second set grating 701b is 90 degrees out of phase and the third set grating 701c Are out of phase by 270 degrees, and the fourth set of gratings 7
01d is 180 degrees out of phase. FIG. 22 shows the relative position of each grating at time t0 when the grating 701a is in phase with the moving tick mark. Two sets of gratings (7) in which the center point of the rectangular window 701 is 180 degrees out of phase each.
01a / 701d, 701b / 701c), and the misalignment error when the print medium is at an angle to the marking line is minimized.

At time t0, with respect to the sensor OP1, the first set of gratings 701a reflects the maximum amount of light to the sensor OP1 since the light portions of the tick marks are not blocked by the opaque markings of the grating. Second set, third set grid (70
1b, 701c) sensor OP located behind
3, for OP4, an intermediate amount of light is reflected to sensors OP3, OP4 because the opaque engraving blocks a portion of the light reflected from the tick mark, and for opaque engraving, for sensor OP2. A minimal amount of light is reflected back to the sensor OP2 because the bright portions of the and the tick mark completely overlap.

As the print medium 128 moves from right to left, the light intensities detected by the sensors OP1 and OP3 located behind the first and second gratings 701a and 701b indicate the tick mark track Drop as the dark portion of the grid enters the translucent portion of the grating, and at the same time the third set,
The intensity of light sensed by the sensors OP4 and OP2 located behind the fourth set gratings 701c and 701d increases.
Therefore, if the intensity of light sensed by these sensors is plotted, a periodic waveform as shown in FIG. 23 is obtained.

A current modulated by the detected light intensity flows through the four sensors OP1 to OP4. The four currents are combined at the nodes 602a, 602b (FIG. 15) into two currents: each combined current is the sum of the sensor intensities 180 degrees apart. Pin 4 of sensor OP1
The output currents of OP1, OP2 are summed at node 602a to generate a bipolar current signal due to the positive current flowing out of and the negative current flowing into pin 3 of sensor OP2. This signal has less symmetry than the signal generated by the individual sensors, because mismatches between the line width of the image and the line width often result in oppo-site effects at sensors 180 degrees apart. Are better. This is because the light intensity increases in OP1 and the positive current increases, and the light intensity decreases in OP2 and the negative current output decreases. The sum of the two currents is positive and is attenuated by the inverse effect at each sensor. Similarly, when the intensity of light sensed by the sensor OP1 decreases, the positive current decreases and the negative current increases, and the sum of the two currents is negative. Therefore, the total variation from the + peak to the-peak is twice that of the individual sensors.
Again, for that purpose the sensors OP3, OP4 are similarly connected in order to improve the signal symmetry.

The combined currents 602a and 602b of the SINE lead and the COSINE lead are converted into voltages by low-pass filter circuits 601a and 601b (FIG. 16), respectively, and sent through the leads 609a and 609b. Output currents corresponding to Ronchi lattices having phases of 0 degree, 90 degrees, 270 degrees, and 180 degrees are sine, cosine, -sine, and -cosine, respectively (see FIG. 23).

Referring to FIG. 15, the intensity of light is
Since it changes in P1, OP2, Q1,
Obviously, the phototransistor current of Q2 is modulated. The two currents are added at the SINE node corresponding to pin 10 in FIG. 15 to form a single current signal, which is sent via lead 602a to the circuit of FIG. The current of the lead 602A is
The voltage signal is converted by a low-pass filter 601a composed of a resistor 605a and an op amp 606a, and sent via a lead 609a. A differentiating circuit consisting of a capacitor 608a and a resistor 611a attenuates the DC bias and low frequency signal mainly resulting from the following two: low frequency signal due to changes in the reflectivity of the print medium 128 (so-called "mottling"). Occurs; the allowable rate in each of the sensors OP1 to OP4 is 10%.
The imbalance of the current setting resistors 600a-600d results in a DC bias voltage that must be attenuated.

The voltage signal on the lead 609a has a triangular waveform with a DC bias. Capacitor 608a and resistor 61
A differentiating circuit 1a converts the triangular waveform signal on lead 609a to a substantially square waveform signal and sends it via lead 610a. The transition of the signal on lead 610a corresponds to the peak of the triangular waveform of the signal on lead 609a.
The transition of this voltage signal on lead 610a toggles the output signal of comparator 614a, thereby creating a clean square wave at node 617a with a TTL level signal. The line driver 616a couples the output signal S

[Outside 24]

The noise at the time of the operation is removed.

[Outside 25]

Is generated from the output signal. Differential outside sensor assembly 700

[Outside 26]

[0131]

[Outside 27]

That is, two signals SINE and COSIN
E contains information on the position of each print line.
This information is present at the moment of each of the square wave SINE and COSINE transitions. This square wave signal SINE, C
OSINE is exclusive-ORed, and each transition has a third frequency that is twice the frequency that indicates the position of the print line.
Signal. The frequency of the third square wave signal is twice the frequency of each component wave (see FIG. 24). Each edge of this third square wave is the starting point of the print line.

Therefore, the edges of the SOP signal and the exclusive OR processing signal occur simultaneously, and the SOP of the correct print line is started.

A list of components of the circuit of FIGS. 9, 15 and 16 is given in the following table:

[0135]

[Table 1]

The present invention is not limited to the embodiments introduced above, but it is obvious to those skilled in the art that various other modified embodiments are possible within the scope of the appended claims. Think.

[Brief description of the drawings]

FIG. 1 is an illustration of an SOP mark 111 provided on a separate track on a sheet (print medium) on which an image is to be printed.

FIG. 2 is an illustration of a relative position of two sensors OP5 and OP6 for detecting an SOP mark 111 shown in FIG.

FIG. 3 is a diagram illustrating a case where the parts 115t and 115b of the opening 115 in which the sensors OP5 and OP6 shown in FIG.
4 is an illustration of a waveform 130 generated when a mark 111 passes.

FIG. 4 shows the SOP mark 111 of the substrate (FIG. 1).
Is a block diagram of a circuit that processes signals generated by the sensors OP5 and OP6 when passing through the sensors OP5 and OP6 shown in FIG.

FIG. 5 is an illustration of a waveform in a two-part SOP mark.

FIG. 6 is an illustration of a two-part SOP mark as prior art.

FIG. 7 shows a two-part SO according to the invention, consisting of two parts located above and below the tracking line.
It is an illustration of a P mark.

FIG. 8 is an illustration of a three-part SOP mark of the present invention and sensors OP5 and OP6 for sensing the mark.

FIG. 9 is an illustration of two replicas of the circuit shown in the block diagram of FIG. 4, according to one embodiment of the present invention.

FIG. 10 is a diagram showing the operation principle of the circuit shown in FIG.

FIG. 11 is a diagram showing the operation principle of the circuit shown in FIG. 9;

FIG. 12 is a diagram showing the operation principle of the circuit shown in FIG. 9;

FIG. 13: SOP mark 111, tick mark 72
0 and right-angle gratings 701a, 701b, 701c, 7
It is a figure which shows the position of the sensor OP1-OP6 with respect to 01d.

FIG. 14 shows an SOP mark 111 and a tick mark 72.
0 and right-angle gratings 701a, 701b, 701c, 7
It is a figure which shows the position of the sensor OP1-OP6 with respect to 01d.

FIG. 15 is a block diagram of a quadrature signal sensor circuit used in the system / method of the present invention.

FIG. 16 is a block diagram of a quadrature signal sensor circuit used in the system / method of the present invention.

FIG. 17 is a plan view showing the position of the sensor assembly with respect to the SOP mark 111 and the moving tick mark 720 of the print medium.

FIG. 18 is a perspective view of a sensor assembly 700.

FIG. 19 is a perspective view of a sensor assembly 700 in relation to a moving print medium.

FIG. 20 is a plan view of an LED phototransistor package constituting the sensors OP1 to OP6.

FIG. 21 is a diagram showing the positions of the LED / phototransistor packages of OP5 and OP6 with respect to the positions of the portions 115t and 115b of the opening 115.

FIG. 22 shows a Ronchi grid 7 of a sensor assembly 700 (FIG. 17) that generates a right-angle output signal for a moving tick mark 720 (FIGS. 13, 14 and 17) on a print medium.
It is a figure which shows the relative position of 01a, 701b, 701c, 701d, 701d.

FIG. 23 shows a tick mark 720 (FIG. 1) on a print medium.
7) is the Ronchi grid 701a of the sensor assembly 700,
701b, 701c, 701d (FIGS. 13, 14,
7, FIG. 18), the quadrature phase signal sensors OP1, OP3, OP4, O shown in FIGS.
It is a figure showing the waveform which P2 generates.

FIG. 24: Quadrature phase signal sensors OP1, OP3, OP
4 is a diagram illustrating a process of performing exclusive OR processing on a sine signal and a cosine signal generated by OP2 to generate a print signal of each plot line on a print medium.

[Explanation of symbols]

 110 tracking line 111 SOP mark 115 aperture 116 print medium moving direction 126 LED 128 print medium 130 SOP signal 700 sensor assembly 701a-d Ronchi grating 720 tick mark OP1-OP6 optical sensor

Claims (4)

[Claims] 1. A plurality of mark detecting elements for detecting a mark having substantially the same width and an interval between adjacent lines printed on a moving print medium, and a mark having the same shape as the mark, In a print medium position detection system provided with a mask portion provided corresponding to each of a plurality of mark detection elements, signals detected by the respective mark detection elements via the mask section all exhibit strength at the same cycle. And a set of the plurality of mark detection elements and the mask section are arranged so that the phases of the respective signals are repeatedly detected with a shift at a fixed interval. 2. The printing method according to claim 1, further comprising timing signal output means for sequentially extracting a maximum value or a minimum value of the signals detected by the plurality of mark detection elements and outputting the maximum value or the minimum value as a timing signal. Media position detection system. 3. The print medium position detection system according to claim 2, wherein printing on said print medium is started using a timing signal output from said timing signal output means. 4. The apparatus according to claim 1, wherein the mark detection element and the mask portion are four.
2. The apparatus according to claim 1, wherein a plurality of sets are provided, and the phases of the signals detected in each set are repeatedly detected with a shift of 1/4 cycle.
The print medium position detection system as described in the above.