JP2001113685A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus in which shift of a head can be detected accurately when the head is replaced. SOLUTION: A specified pattern is printed by means of a plurality of heads 103 under control of a head control section 105, a specified pattern element thus printed is read out by means of a sensor 111 and subjected to sampling and A/D conversion at a pattern detecting section 106 to produce a digital value of a plurality of bits from the sensor 111. The detected digital value is stored for a specified term at a resist regulation detecting section 107 and the position of the pattern element is detected through digital processing based on the digital value. Shift of the head is calculated based on the distance from the detected position of each pattern element to the detected position of the pattern element of a reference head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus for forming an image using an ink jet recording system.

[0002]

2. Description of the Related Art In an ink jet recording system in this type of image forming apparatus, several heaters are mounted in a nozzle filled with ink, and a heater is heated by applying a pulse signal to the heater. The ink is boiled, and the ink is ejected at a bubble pressure generated by the boiling. When this is used as an image forming apparatus, several heads are arranged to form one head,
A full-color image is formed by using a combination of several such heads (for example, several heads that eject cyan, magenta, yellow, and black inks).

In such an image forming apparatus, a control circuit for driving the head is configured as shown in FIG. FIG. 1 shows a case where one head is formed. In FIG. 2, reference numeral 201 denotes a shift register;
Is a latch circuit, 203 to 206 are AND circuits, and 207 to
210 is a transistor and 211 is a heater.
Image data VDO is externally transferred as serial binary data in synchronization with the transfer clock CLK, and serially / parallel converted by the shift register 201 sequentially. 12
After eight (in this example, a head composed of 128 nozzles are used) unit image data VDO is transferred, each of the nozzles is held by the LAT signal. In addition, one head composed of several nozzles is divided into n blocks (in this example, a head composed of 128 nozzles is divided into eight blocks and used), and one pulse of enable signal BENB0 is used for one block. To n and a pulse signal HENB for driving the heater, the transistor is turned ON only for the nozzles in which image data is enabled and held, and the heater is heated to discharge ink.

Under the above-described control, one column is printed as shown in FIG. 3, and one band is printed by printing a number of columns in the main scanning direction. Send more paper and 2
Band printing is performed, and such band formation is repeated a plurality of times to form an image composed of a plurality of bands.

In order to print at an accurate position with respect to the fluctuation of the carriage speed, a linear scale having a slit 401 for each dot as shown in FIG. Head 10
The sensor 402 mounted near the sensor 3 controls the ejection of ink at an accurate position by synchronizing the ink ejection using the output signal.

The structure of the head is a type in which the head and the ink tank are integrated as shown in FIG.
(B)) and a type in which an ink tank is arranged separately from the head (FIG. 5 (a)). In the type in which the head and the ink tank are integrated, the entire head must be replaced when the ink is consumed. On the other hand, in the type in which the head and the ink tank are separately arranged, only the ink tank can be replaced when the ink is consumed.However, since the head also has a life, when the ink is discharged a certain number of times, Separately, the head must also be replaced. In any case, the head is generally treated as a consumable and is arbitrarily replaced by a user's will.

As described above, in an image forming apparatus using a plurality of heads, when one or several of the heads are replaced, as shown in FIGS. In some cases, a shift in the mounting in the horizontal direction or a shift in the mounting in the vertical direction occurs, and when printing is performed as it is, streaks occur in the horizontal or vertical direction, resulting in image unevenness.

In order to eject ink at an accurate position with respect to the main scanning position of the head, an apparatus that synchronizes ink ejection with a linear scale performs reciprocating printing as shown in FIG. Since a delay occurs from the slit position to the ejection of the ink as shown in c), the ejection position may be shifted to cause image unevenness. This was particularly noticeable in the case of line art.

Conventionally, in order to correct such image unevenness, for example, as shown in Japanese Patent Application Laid-Open No. 7-323562, a predetermined test pattern is printed, read by a sensor, binarized, and read. There is a method of detecting a shift of a printing position among a plurality of heads.

[0010]

In the conventional method of detecting a pattern position by binarizing a sensor output, the detection is performed by using many analog circuits.
There is a problem in terms of cost and board area (especially on the carriage) that the circuit configuration becomes large-scale, and furthermore, it is directly affected by noise generated by extraneous equipment or inside the equipment, and the reflectance differs. When adjustment is performed using paper, it has been difficult to detect a pattern, especially on paper having low reflectance.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object of the present invention is to provide an image forming apparatus for accurately detecting a head displacement when a head is replaced.

Another object of the present invention is to provide an image forming apparatus capable of reducing the scale and cost of a circuit configuration for accurately detecting a head displacement.

[0013]

In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus for forming an image using a plurality of heads by an ink jet recording system, wherein the plurality of heads are formed. Printing means for printing a test pattern including pattern elements parallel to each other for detecting a displacement of the mounting position of the head by the reference head and another head, and the parallel pattern elements printed by the printing means , An analog-to-digital converter for sampling the output of the sensor according to a sample clock and converting the output to a digital value, and a storage unit for storing a plurality of sequential digital values obtained by the analog-to-digital converter Average value calculating means for calculating an average value of the plurality of digital values stored by the storage means By comparing the average value obtained by the average value calculation means with the current digital value, the position of each pattern element is detected, and among the parallel pattern elements, the pattern element of the reference head is detected. Then, the time until the pattern element of the other head is detected is calculated, the distance between the two pattern elements is calculated from the calculated time, and based on the calculated distance between the pattern elements. A displacement calculating means for calculating a displacement amount of the head.

As described above, the sensor output is sampled and digitized by the analog-to-digital conversion means, and the digital value of a plurality of bits is stored / processed, so that the position of the pattern element can be accurately detected, and thus the head position. It is possible to accurately determine the amount of deviation.
In addition, by using digital processing, for example, an integrated circuit such as a gate array already existing in the device can be used, and as a result, the pattern can be detected stably with a small circuit configuration. be able to.

The value obtained by the average value calculating means is:
For example, it is a moving average value of a digital value representing a change in the output of the sensor means.

Another image forming apparatus according to the present invention is an image forming apparatus for forming an image by using a plurality of heads by an ink jet recording system, wherein an image is formed by a reference head and another head among the plurality of heads. Printing means for printing a test pattern including pattern elements parallel to each other for detecting a shift in the mounting position of the head; sensor means for scanning the parallel pattern elements printed by the printing means; and Analog-to-digital conversion means for sampling the output in accordance with a sample clock and converting it to a digital value, delay means for delaying a plurality of sequential digital values obtained by the analog-to-digital conversion means for a predetermined time, and output from the delay means The position of each pattern element is detected by comparing the digital value with the current digital value. Of the parallel pattern elements, the time from when the pattern element of the reference head is detected to the time when the pattern element of the other head is detected is determined, and the time between both pattern elements is determined from the determined time. A shift calculating unit that calculates a distance and calculates a head shift amount based on the calculated distance between the pattern elements.

Still another image forming apparatus according to the present invention is an image forming apparatus for forming an image using a plurality of heads by an ink jet recording method, wherein a reference head and another head among the plurality of heads are used. Printing means for printing a test pattern including pattern elements parallel to each other for detecting a shift in the mounting position of the head, sensor means for scanning the parallel pattern elements printed by the printing means, and the sensor means Analog-that samples the output of the
Digital conversion means, average value calculation means for detecting the maximum value and the minimum value of the digital value obtained by the analog-digital conversion means, and calculating the average value thereof, and the average obtained by the average value calculation means By comparing the value with the current digital value, the position of each pattern element is detected,
The time from when the pattern element of the reference head is detected to when the pattern element of the other head is detected is calculated, and the distance between the two pattern elements is calculated from the calculated time. Deviation calculating means for calculating the amount of deviation of the head based on the distance between the pattern elements,

[0018] In this case, it is preferable to have reset means for resetting the maximum value and the minimum value of the detected digital value each time the average value obtained by the average value calculation means matches the current digital value.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in FIG. 1 includes a print control unit 102 and a head 103. The print control unit 102 includes a linear scale sensor 4
02, a pattern reading sensor 111 and an upper cover opening / closing detection sensor 112 are connected.

The apparatus shown in FIG. 1 performs control for forming an image image on recording paper using a head 103 from serial image data VDI transferred from an external device 101 such as an image scanner, a personal computer, and a CAD. In particular, the print control unit 102 generates a signal necessary for that.

The print controller 102 comprises a CPU 109, a head controller 105, a pattern detector 106, a pattern width detector 107, and a registration adjustment amount detector 108. Among them, the CPU 109 interfaces with the external device 101, and also stores various memories and I / Os.
For example, the operation of the entire print control unit 102 is controlled.

From the external device 101, the serial image data V
When the DI is transferred, the instruction from the CPU 109
The head controller 105 temporarily stores the image data VDI for several bands in the image memory. Held image data VD
Various image processing is applied to I, and image data VDO is output to the head 103 in accordance with the scanning of the head 103.

In this embodiment, the linear scale 110 is moved along the moving path of the head 103 as shown in FIG.
Are arranged, and the linear scale sensor 402 (FIGS. 1 and 4) cooperating with the linear scale 110 is
The print control such as the output of the image data VDO is synchronized by using the signal LINSCL output in synchronization with the scan 3. The head controller 105 also generates enable signals BENB0 to BENB7 for each block of the head 103 and a pulse signal HENB for driving the heater, which is necessary for ink ejection. In the present embodiment, since the head composed of 128 nozzles is divided into eight blocks and used, there are eight block enable signals. Image data VD output from head control unit 105
O, the block enable signals BENB0 to BENB7, the pulse signal HENB for driving the heater and the like are transferred to the head 103,
The control circuit in the head 103 turns on the heater only for the nozzles for which the image data VDO and the enable signals (indicating BENB and HENB) are enabled. As a result, ink is ejected from the nozzle and adheres to the recording paper to form an image for one column. By repeating such control while scanning the head 103 in the main scanning direction, an image image for one band is formed.

In this embodiment, the head control unit 10
5 and the head 103 are provided in four circuits (sets), and cyan, magenta, yellow, and black heads and ink tanks are provided to perform full-color printing.
The following description will be omitted for only one circuit (set).

As shown better in FIG. 7, an upper cover opening / closing detection sensor 112 is attached to the apparatus main body. When the upper cover 91 is opened and the head 103 is replaced, the upper cover 91 is automatically replaced with the one shown in FIG. A test pattern as shown in (b) is printed. Each test pattern is composed of five pattern elements a to e in this example. FIG.
The pattern in FIG. 8A is for detecting a shift in the main scanning direction (horizontal direction) of the head, and the pattern in FIG. 8B is for detecting a shift in the sub-scanning direction (vertical direction) of the head.

In FIG. 8, pattern elements a / b are printed using a reference head, and pattern elements c / d / e are printed.
Prints using another head. In the present embodiment, the pattern element a / b is black and the pattern element a / b is black, since the head provided with the ink tank of another color is matched with the head provided with the black ink tank.
Printing is performed using a head provided with ink tanks in which c is cyan, d is yellow, and e is magenta. FIG. 8 (a)
Is expressed by shifting the pattern element c / d / e with respect to the pattern element b, but the printing is to be performed on the same reference line, but the head is moved in the horizontal direction as shown in FIG. , The printing result shows a state in which the printing is performed with a shift. The same applies to FIG.

In the present embodiment, the upper cover opening / closing detection sensor 112 constitutes a head replacement detecting means, and it is assumed that the head has been replaced when the upper cover 91 is opened. Of course, instead of the upper cover opening / closing detection sensor 112, the apparatus may detect the head replacement according to an instruction of a maintenance person or a user.

Further, a pattern reading sensor 111 which is a reflection type optical sensor is attached near the head as shown in FIG. After printing the test pattern as shown in FIG. 8, each pattern element is read by the sensor 111,
The registration adjustment amount is detected through the following steps. The sensor 111 is relatively scanned with respect to the pattern.
More specifically, in the present embodiment, scanning in the main scanning direction is performed by moving the sensor 111 with respect to the sheet, and scanning in the sub-scanning direction is performed by transporting the sheet to the sensor 111. Do.

8 (a) and 8 (b), first of all,
The sensor 111 scans the pattern elements a / b, and the pattern detecting unit 106 in the print control unit 102 detects a portion where the density of the pattern changes based on the output of the sensor 111. Then, pattern element a / c, pattern element a
Similarly, each of the two pattern elements is scanned in / d and the pattern elements a / e to determine the distance between the two pattern elements. After obtaining these data, a difference from the other data is obtained based on the data of the pattern element a / b to determine in what direction and how much the other head is attached to the reference head. It can be calculated.

The operation of each section will be described below. First, the internal configuration and simple operation of the head 103 will be described again with reference to FIG.
This is performed using

The head 103 comprises a shift register circuit 201, a latch circuit 202, AND circuits 203 to 206, transistors 207 to 210, and a heater 221 as shown in FIG. The head 103 is synchronized with the transfer clock CLK from the head control unit 105,
The serially transferred image data VDO is converted into parallel data by the shift register 201, and when the 128 unit data are prepared, the latch 2 is latched by the holding signal LAT.
02 temporarily holds the data. The held image data VDO is used as follows. That is, the block enable signal BENB0 generated by the head control unit 105
7 and the heater drive pulse signal HENB are both enabled, and the transistors 207 to 210 corresponding to only the nozzles for which image data is enabled are turned on, the heater 221 is heated, ink is ejected from the nozzles, and ink is printed on the recording paper. Attach and form an image.

Next, the internal configuration and a brief description of the head control unit 105 which generates signals necessary for driving the head 103 will be described with reference to FIG.

As shown in FIG. 9, the head control unit 105
Mainly include an image memory 901, an image memory control unit 902,
Image synchronization signal generator 903, heater drive signal generator 90
4. As described above, the image memory control unit 902 controls the memory for temporarily storing the serial image data VD transferred from the external device 101 for several bands in the image memory 901 and scans the stored image data for the head 103. , Memory control for outputting the image data VDO to the head 103 is performed. When inputting the image data VDI to the image memory 901, an address signal of the memory 901 is generated in synchronization with the transfer timing of the data from the external device 101.
When the image data VD is sequentially stored and output from the memory 901 in accordance with the scan of the head 103, the synchronization timing (HSYN) from the image synchronization signal generation unit 903 is used.
An address signal of the memory 901 is generated in synchronism with (CTRG), and the image data VDO is output from the memory 901.

As shown in FIG. 10, the image synchronizing signal generator 903 includes an HSYNCTRG generator 1001, a counter 1002, comparators 1003 and 1004, and an AND circuit 10.
05 to 1008, and a CPU I / F unit 1009. This image synchronization signal generation unit 903
3 and a synchronizing signal HSYNCT for outputting image data VDO from the image memory 901 using the signal LINSCL output from the linear scale sensor 402 by scanning.
RG is being generated. Also, the synchronization signal HSYNCT
The RG is counted by the counter 1002, the scan position of the head is recognized, and compared with the area data set by the CPU 109, a print area signal WIND as shown in FIG. 11 is generated.

The image synchronizing signal generation unit 903 also scans the pattern printed on the printing paper when the pattern is scanned by the sensor 111 as shown in FIG. Since the distinction becomes indistinguishable, the resist area signal RE
It also generates GIWIND. When the registration adjustment amount is detected, only the registration area signal REGIWIND is enabled, and the CPU (REGIWIN) is turned off so that WIND is turned off.
RD). This is because when WIND is enabled and the head control unit 105 outputs control signals (VDO, BENB, HENB, etc.) for ink ejection,
This is because ink is ejected.

Further, in synchronization with the synchronization signal HSYNCTRG, the heater drive signal generation section 904 includes a signal (block enable signals BENB0 to BENB7) for selecting which block of the head 103 is to be driven, and a heater drive pulse. The signal HENB is generated.

Image data is printed using the above signals, and when the head 103 is replaced as described above, five pattern elements a as shown in FIGS. To print a test pattern composed of .about.e. After printing the test pattern, each pattern element is read using the sensor 111 attached near the head 103, and the amount of registration adjustment is detected.

On the basis of the output of the sensor 111, a portion where the density of the pattern changes is detected by the pattern detection section 106 in the print control section 102. Details of the pattern detection unit 106 are shown in FIGS. The pattern detection unit 106
The analog-digital conversion means of the present invention, the storage means for holding the output digital value thereof, the average value calculation means for calculating the average value of a plurality of digital values, and at least a part of the shift calculation means (the position of each pattern element) Function to detect the

In FIG. 13, reference numeral 1301 denotes an 8-bit A /
D converter, 1302 is a shift register, 1303 is an 8-bit × 64-stage shift register, 1304, 130
Reference numeral 5 denotes a 1/64 unit that generates 1 / 64th of the input digital value, 1306 denotes a sign inverter, 1307 denotes an adder, 1308 denotes an integrator, and 1309 denotes a digital comparator.

First, the output of the sensor 111 is 8 bits A /
The data is input to a D converter 1301 and converted into a digital value. Although not shown, an amplifier is built in the sensor 111, and an output from the sensor 111 can be obtained as a voltage signal. In this embodiment, the A / D converter 1301 outputs the converted digital value by serial communication. Therefore, the A / D converter 1301 performs serial communication using the shift register 1302 and outputs the digital value as parallel data. This digital value is then 8 bits x
The data is input to the 64-stage shift register 1303. This 8-bit × 64-stage shift register 1303 has an 8-bit parallel input, and 6 bits for each input bit.
There is a 4-bit shift register. That is, the 8-bit × 64-stage shift register 1303 holds the digital value of the sensor sampled 63 times before this time. 1304 and 1305 are 1/6
4 units, 1306 is a sign inverter, 1307 is an adder, 13
08 is an integrator. The digital value integrated by the integrator 1308 corresponds to the average value of the output digital values of the sensor 111 sampled 63 times before this time, that is, a moving average. Hereinafter, the circuit operation of FIG. 13 will be described in detail.

The digital value sampled this time is D
0, the digital value sampled one time before is D1, the digital value sampled two times before is D2,.
If the digital value sampled the previous time is Dn,
The average value Avr of the digital values sampled 63 times before this time is

[0043] It is represented by This can be considered as in the following equation.

[0044]

The first term on the right side of the above equation (2) is the previous moving average value. Therefore, the current moving average value can be obtained by adding the digital value of the sensor detected this time to the previous moving average value and subtracting the digital value sampled 64 times before.

In FIG. 13, the output of 1/64 unit 1304 is D64 / 64, and the output of 1/64 unit 1305 is D64.
0/64, and the output of the sign inverter 1306 is -D64 / 64. Therefore, the adder 1307
Is (D0 / 64-D64 / 64). This is input to an integrator 1308 and integrated, so that a moving average value of digital values sampled 63 times before the current time can be obtained.

The comparator 1309 includes an integrator 130
An output digital value of No. 8 and a digital value sampled this time are input, and a REGIPT signal, which is binary digital data representing a test pattern detection result, is output based on a result of comparing these.

FIG. 14 shows a waveform when a pattern is read with the above circuit configuration. FIG. 14A shows the arrangement of the pattern elements a and b. FIG. 14B shows a sensor output (solid line) and a moving average waveform (dashed line) when a pattern printed with ink having a low reflectance (for example, black) is read. FIG. 14C shows a sensor output (solid line) and a moving average waveform (dashed line) when a pattern printed with ink having a high reflectance (for example, yellow) is read. As can be seen from the figure, the pattern element position can be detected at the same timing regardless of the reflectance of the pattern to be read. Focusing on the fact that the position of the intersection (intersection) of the sensor output (solid line) and the waveform of the moving average (dashed line) is substantially constant irrespective of the reflectance of the pattern to be read, and based on the position of the intersection This is because the position of the pattern element is detected.

With respect to the binary digital data (REGIPT), the registration adjustment amount detection unit 108 calculates the distance between each set of pattern elements based on these data.

FIG. 15 shows details of the registration adjustment amount detection unit 108. The registration adjustment amount detection unit 108 detects another part of the deviation calculation means in the present invention (the time from when the pattern element of the reference head is detected to when the pattern element of the other head is detected). Function). Remaining function of deviation calculating means (function of calculating the distance between both pattern elements from the detected time and calculating the amount of deviation of the head based on the calculated distance between the pattern elements)
Is assigned to the CPU 109 (FIG. 1). It should be noted that the assignment of specific functions of the shift calculating means is arbitrary, and the present invention is not limited to the embodiment.

In FIG. 15, reference numeral 1601 denotes a flip-flop, 1602 denotes a counter, and 1603 denotes a CPU I / F. Based on the REGIPT signal output from the pattern detection unit 106, the registration adjustment amount detection unit 108
02, the distance between the pattern elements is counted, and after the pattern reading is completed, the data of the counter 1602 is read by the CPU. This data is the data of the distance between the pattern elements a / b in FIG.

The above operation is performed by pattern elements a / c,
By repeating the pattern element a / d and the pattern element a / e, the distance between each pattern element is similarly obtained. After obtaining each of the above data, a difference from each of the other data is calculated based on the data of the pattern element a / b to calculate how much the other head is attached to the reference head. It becomes possible. It is also possible to detect the shift direction by the sign (+/-) of the difference result.

FIG. 8A shows a pattern for detecting a lateral registration error shown in FIG.
By performing with respect to the pattern for detecting the vertical resist displacement shown in FIG. 3B, it is possible to detect the displacement due to the vertical / horizontal attachment.

A configuration in which the pattern detection unit 106 in FIG. 13 is replaced as shown in FIG. 17 is conceivable.

The pattern detecting section 106 shown in FIG. 17 comprises a sensor 111, an 8-bit A / D converter 1901, an 8-bit shift register 1902, an 8-bit × 64-stage shift register 1903, and a digital comparator 1904. The pattern can be detected with a smaller hardware configuration than the configuration. This is a circuit configuration that simply compares the digital value of the sensor output sampled 64 times before and the digital value of the sensor output sampled this time, and outputs the result as REGIPT. The digital value of the sensor output sampled 64 times before corresponds to a signal obtained by delaying the sensor output. That is, the shift register 1903 in this configuration functions as a delay unit that delays the sensor output for a predetermined time. This circuit configuration is much simpler than the configuration in FIG.

FIG. 18 shows a waveform when a pattern is read with such a circuit configuration. FIG. 18A shows the arrangement of the pattern elements a and b. FIG. 18B shows the sensor output (solid line) when reading a pattern printed with ink with low reflectance (for example, black) and the waveform of the delay signal (dashed line). FIG. 18C shows a sensor output (solid line) when a pattern printed with ink having a high reflectance (for example, yellow) is read, and a waveform of the delay signal (broken line). As can be seen from the figure, the pattern element position can be detected at the same timing regardless of the reflectance of the pattern to be read. This is due to the fact that the intersection point between the sensor output and the waveform of the delay signal is substantially constant regardless of the reflectance of the pattern. It is preferable that the delay amount of the delay signal is set such that the intersection position is about half the height of the peak value of the sensor output. Thereby, the position of the intersection (the rising position of the REGIPT signal)
Is clearly determined.

Further, the pattern detecting section 106 shown in FIG.
May be replaced with a configuration as shown in FIG. FIG.
9, 111 is a sensor, 2101 is an 8-bit A /
D converter, 2102 is an 8-bit shift register,
103 is a maximum value detection circuit, 2104 is a minimum value detection circuit,
2105 and 2106 are both 1/2 units, 2107
Is an adder, and 2108 is a comparator. In this configuration, when one pattern element is detected,
The maximum value and the minimum value of the digital value of the sensor output are always detected, and an intermediate value between the maximum value and the minimum value is calculated,
The calculated value and the digital value of the sensor output detected this time are compared by the comparator 2108, and the result is
It has a circuit configuration to output as PT.

FIG. 20 shows a waveform when a pattern is read with such a circuit configuration. FIG. 20A shows the arrangement of the pattern elements a and b. FIG. 22B shows a waveform of a sensor output (solid line) and a calculated intermediate value (broken line) when a pattern printed with ink having a low reflectance (for example, black) is read. FIG. 22C shows a sensor output (solid line) and a waveform of a calculated intermediate value (dashed line) when a pattern printed with ink having a high reflectance (for example, yellow) is read. Also in this case, the pattern element position can be detected at substantially the same timing regardless of the reflectance of the pattern to be read.

Although the preferred embodiment of the present invention has been described above, various modifications and changes are possible. For example,
In the test patterns shown in FIGS. 8A and 8B, a plurality of sets (X sets) are juxtaposed to each other, and the test patterns shown in FIGS.
Test patterns shown in FIG. In this case, measurement results can be reduced by obtaining X results and using the average value.

[0060]

As described above, according to the present invention,
A predetermined pattern is printed by a plurality of heads, the printed predetermined pattern element is read, and a deviation amount of another of the plurality of heads from a reference head is digitally detected from the read pattern element. Therefore, it is possible to accurately detect a displacement between the heads due to the mounting of the heads when the heads are replaced and a displacement occurring in reciprocating printing. Further, these deviation detection functions can be realized with a small circuit configuration and at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing details of an internal circuit of the head in the embodiment of FIG. 1;

FIG. 3 is a diagram illustrating an example of a print result in the embodiment of FIG. 1;

FIG. 4 is a diagram showing a configuration of a linear scale and a slit in the embodiment of FIG. 1;

FIG. 5 is a diagram illustrating a configuration example of a head and an ink tank.

FIG. 6 is a diagram showing a printing result when the head is shifted.

FIG. 7 is a diagram showing a main body configuration including an upper cover in the embodiment of FIG. 1;

FIG. 8 is a diagram showing a print pattern in the embodiment of FIG.

FIG. 9 is a block diagram illustrating a configuration of a head control unit in the embodiment of FIG. 1;

FIG. 10 is a block diagram illustrating a configuration of an image synchronization signal generation unit used in the head control unit of FIG. 9;

FIG. 11 is an explanatory diagram showing definitions of a print area signal WIND and a synchronization timing HSYNCTRG.

FIG. 12 is an explanatory diagram showing the definition of a resist area signal REGIWIND.

FIG. 13 is a block diagram illustrating a first configuration example of a pattern detection unit in the embodiment of FIG. 1;

FIG. 14 is a waveform chart for explaining the operation of the pattern detection unit in FIG. 13;

FIG. 15 is a block diagram illustrating a configuration of a registration adjustment amount detection unit in the embodiment of FIG.

16 is a diagram showing a print pattern in which a plurality of sets of the pattern of FIG. 8 are juxtaposed.

FIG. 17 is a block diagram illustrating a second configuration example of the pattern detection unit in the embodiment of FIG. 1;

FIG. 18 is a waveform chart for explaining the operation of the pattern detection unit in FIG. 17;

FIG. 19 is a block diagram illustrating a third configuration example of the pattern detection unit in the embodiment of FIG. 1;

FIG. 20 is a waveform chart for explaining the operation of the pattern detection unit in FIG. 19;

[Explanation of symbols]

 Reference Signs List 101 external device 102 print control unit 103 head 105 head control unit 106 pattern detection unit 108 registration adjustment amount detection unit 109 CPU 110 linear scale 111 sensor 112 upper cover open / close detection sensor 402 linear scale sensor

Claims (5)

[Claims] 1. An image forming apparatus for forming an image using a plurality of heads by an ink jet recording method, wherein a displacement of a mounting position of a head is detected by a reference head and another of the plurality of heads. Printing means for printing a test pattern including pattern elements parallel to each other, sensor means for scanning the parallel pattern elements printed by the printing means, and digitally sampling the output of the sensor means according to a sample clock. Analog-to-digital conversion means for converting to a value, storage means for holding a plurality of sequential digital values obtained by the analog-to-digital conversion means, and calculating an average value of the plurality of digital values stored by the storage means Average value calculating means, and the average value obtained by the average value calculating means and the current digital value are calculated. The position of each pattern element is detected by comparison, and the time from when the pattern element of the reference head is detected among the parallel pattern elements to when the pattern element of the other head is detected. Is calculated, and the distance between both pattern elements is calculated from the obtained time,
And a displacement calculating means for calculating a displacement amount of the head based on the calculated distance between the pattern elements. 2. The value obtained by the average value calculating means is:
The image forming apparatus according to claim 1, wherein the image forming apparatus is a moving average value of a digital value representing a change in an output of the sensor unit. 3. An image forming apparatus for forming an image using a plurality of heads by an ink jet recording method, wherein a displacement of a mounting position of a head is detected by a reference head and another of the plurality of heads. Printing means for printing a test pattern including pattern elements parallel to each other, sensor means for scanning the parallel pattern elements printed by the printing means, and digitally sampling the output of the sensor means according to a sample clock. Analog-to-digital conversion means for converting a value into a value; delay means for delaying a plurality of sequential digital values obtained by the analog-to-digital conversion means for a predetermined time; digital value output from the delay means and a current digital value; By comparing the positions of the pattern elements, the position of each pattern element is detected. Calculating the time between the detection of the pattern element of the reference head and the detection of the pattern element of the other head, calculating the distance between the two pattern elements from the obtained time; And a shift calculating unit that calculates a shift amount of the head based on the determined distance between the pattern elements. 4. An image forming apparatus for forming an image using a plurality of heads by an ink jet recording method, wherein a displacement of a mounting position of a head is detected by a reference head and another of the plurality of heads. Printing means for printing a test pattern including pattern elements parallel to each other, sensor means for scanning the parallel pattern elements printed by the printing means, and digitally sampling the output of the sensor means according to a sample clock. Analog-to-digital conversion means for converting the value into a value, average value calculation means for detecting the maximum value and the minimum value of the digital value obtained by the analog-digital conversion means, and calculating the average value thereof; The position of each pattern element is detected by comparing the average value obtained by the means with the current digital value. The time from when the pattern element of the reference head is detected to when the pattern element of the other head is detected is calculated, and the distance between the two pattern elements is calculated from the calculated time. And a displacement calculating unit for calculating a displacement amount of the head based on the distance between the pattern elements. 5. A reset means for resetting the maximum value and the minimum value of the detected digital value each time the average value obtained by the average value calculation means matches the current digital value. 5. The image forming apparatus according to 4.