JPH0571391B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording apparatus using, for example, an inkjet recording method.

Conventionally, in inkjet recording as described above, the characteristics of the head, the composition and characteristics of the ejected ink droplets,
There has been a problem in that it is difficult to control the actual print density to a desired density due to factors such as variations in the material of the recording paper.

For this reason, for example, as shown in Japanese Patent Application Laid-Open No. 55-55968, it is necessary to immediately read the recorded ink droplets and control the ejection of the ink droplets from a correction orifice provided separately based on the results. Therefore, methods have been proposed for printing with a desired density.

However, the above-mentioned method requires a correction orifice and has a complicated configuration. Furthermore, when printing, halftone processing is performed on a given multi-valued image signal, and when the density of the image is reproduced by the number of dots, the above-mentioned proposed method cannot perform accurate reading. Therefore, there was a problem that the print density could not be accurately controlled.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a recording apparatus that can accurately control print density with a simple configuration and perform high-quality recording.

Hereinafter, the present invention will be explained in detail based on the drawings. The following example uses an IJ type cylindrical piezo type Gould head.

FIG. 1 shows an image recording apparatus to which the present invention is applied. Here, calculation control unit (hereinafter referred to as CPU) 1
In response to an imaging control signal CTV from 1, a television (hereinafter referred to as TV) camera 13 images a subject (human being) 15 and supplies the imaging information signal 17 to a frame memory (hereinafter referred to as FM) 19.
This FM 19 is an analog-to-digital (hereinafter referred to as A/D) converter that converts the analog quantity of the signal 17 sent from the TV camera 13 into a digital quantity;
It includes a memory for storing information for one TV screen, a digital-to-analog (hereinafter referred to as D/A) converter for converting digital amounts into analog amounts, and an interface circuit for transmitting and receiving signals with an external control section. A D/A output signal 21 of the FM 19 is received by a monitor receiver 23 to record and display a still screen. Through the first bus line B1, the CPU 11,
A first data signal DATA1 is exchanged between the FM 19 and the line memory 31. If the TV screen is divided into 512 x 490 pixels, the capacity of this line memory 31 is equivalent to one rotation of the drum.
It must be able to store 512 or more pieces of data. Note that if high-speed access is possible between the FM 19 and other circuit sections, the line memory 31 is not particularly required. A pattern generator (hereinafter referred to as PG) 33, which stores a large number of various patterns, generates a dot-format image in accordance with a second data signal DATA2 of image density outputted from the line memory 31 via the second bus line B2. 3rd data signal for halftone display
Generates DATA3. This data signal DATA3
is supplied to the parallel-to-serial (hereinafter referred to as P/S) converter 35 as a parallel signal via the third bus line B3. A serial signal 41 output from the P/S converter 35 is supplied to a head driver 43, and ink is ejected from an inkjet (hereinafter referred to as IJ) head 47 based on the output drive signal 45.

Recording paper (not shown) wrapped around the recording drum 51
At the top, an image is printed in response to ink ejection from the IJ head 47. The position A printed in this manner is read at the position B by rotating the drum 51 in the direction a. Position B by light source 55
A light beam 57 is irradiated onto the print at , and the reflected light 5
9 is received by the photoelectric element 61. An electric signal 63 obtained by photoelectric conversion by this photoelectric element 61 is amplified by an amplifier 65, and the amplified output signal 67 is supplied to an A/D converter 69. The parallel digital signal SAD obtained by converting the analog quantity of the signal 67 into a digital quantity is sent to the CPU via the fourth bus line B4.
11.

A rotary encoder 71 directly connected to the recording drum 51 generates an output pulse 73 indicating the rotational position of the drum 51 and supplies it to the CPU 11 . In response to this output pulse 73, the CPU 11 controls the recording drum 5.
The position of the print dot (position A) by the IJ head 47 is determined by controlling the rotation drive unit (not shown) of No. 1.

The IJ head 47, light source 55 and photoelectric element 61 are placed on the base 75. A sub-scanning signal 79 is supplied from the CPU 11 to a pulse motor 81, and a base 75 interlocked with this motor 81 moves in a direction (b-direction) perpendicular to the main-scanning direction (a-direction) to perform sub-scanning. The detector 85 generates a signal STR to the drum 51 representing the recording start position on the recording paper.
Further, the detector 87 generates a signal STP representing the recording stop position on the recording paper. Both signals STR and STP are transferred to the fourth bus line B.
4 to the CPU 11 to perform an interlock operation in which printing is not performed at the seam of the recording paper.

The CPU 11 also connects via the fifth bus line B5.
The first address signal ADR1, write signal WR and first read signal READ1 are sent to the line memory 31,
The second address signal ADR2 is sent to PG33, the code signal LOAD is sent to P/S converter 35, and the voltage control signal is sent to P/S converter 35.
CONT to the voltage control section 91, the second read signal
READ2 is supplied to the A/D converter 69, respectively. As a result, in the line memory 31,
In response to the write signal WR, the first address signal ADR
The data signal DATA1 is stored at the address specified by 1. Also, in response to the first read signal READ1,
Read the data stored at the specified address and
Let it be the data signal DATA2. The PG33 searches for a storage pattern that approximates the data pattern represented by the second data signal in accordance with the second address signal ADR2, and generates a third data signal that represents the searched approximate pattern.
In the P/S converter 35, the load signal
The third data signal is temporarily stored in response to LOAD,
Output pulse 73 from rotary encoder 71
By supplying the signal as a shift signal, the serial signal 41 is outputted sequentially. Voltage control section 91
In this case, the voltage signal is output according to the control signal CONT.
CVOLT is generated and sufficient voltage amplification is performed by the head driver 43. Further, the A/D converter 69 converts the analog signal 67 into a digital signal SAD according to the second read signal READ2.

In addition, consider A4 paper as the recording paper. If the width direction of the A4 recording paper is wound around the recording drum 51, the circumference of the drum 51 will be 210 mm.
On the other hand, if the reading resolution is 10 lines per mm and the density information of one reading pixel is 256 gradations, then 16800
(=210×10×8) bits of line memory are required. Therefore, the storage capacity of the line memory 31 is
It is set to 2100 bytes. In addition, one pixel is composed of 4 x 4 recording pixels (this "recording pixel" which is a unit that constitutes one pixel is also referred to as a "picture element" hereinafter), and printing is performed for one recording pixel. Ru1
Assuming that the dot diameter is 20 μm, the number of recording dots per revolution of the drum 51 is 14849 (=(210×
√2)/0.02) dot. Therefore, the number of output pulses 73 in the rotary encoder 71 is required to be 14,849 per rotation.

FIG. 2 shows a test pattern based on one pixel with a 4×4 pixel configuration for expressing halftones. Here, one pattern consists of 4 columns of data R1 to R2 and 4 rows of data, and indicates 16 picture elements 1 to 16 separated by each column and row. This test pattern shows intermediate density D, and picture elements 6, 7, 10
and 11 to print dots A, B, D and C. Four pixels based on such a test pattern were recorded experimentally in a square shape, and the positional correspondence between them and the aperture APT of the density detector, which has an area of 1 pixel (4 x 4 pixels), was determined. Shown in FIGS. 3A and 3B. The minimum number of pixels to be recorded on a trial basis is four. In other words, 4
If there is an area for a pixel, the aperture of the recording paper and the density detector can be printed as shown in the printing dots A1, B1, C1, and D1 as shown in FIG. 3A, or the printing dots A2, B2, C2, and D2 as shown in FIG. 3B. Even if the APT is slightly shifted in position, a sufficiently accurate average image density can be detected within the range of one pixel involved in reading, that is, 4×4 recording pixels (picture elements).

FIG. 4 shows defined addresses of pixels on the drum 51. That is, one revolution of the drum 51 is divided equally into a predetermined number of pixels, and each of the equally divided pixels is defined as an address 0, 1, 2, . . . , M, M+1, . . . from the recording start point. Also, Y perpendicular to the direction of rotation of the drum
Divide equally in the direction, and similarly from the recording start point to 0,
Addresses are defined as 1, 2, ..., N, N-1, .... Therefore, for example, the address of pixel P is (M,N)
is defined as Furthermore, since one pixel has a 4×4 dot configuration, the interior of the pixel P is partitioned into 4×4 squares.

Now, four mutually adjacent addresses (M, N),
(M+1, N), (M, N+1) and (M+1,
Consider the case where a test pattern of density D shown in FIG. 2 is printed on recording paper at each of the four pixels (N+1).

First, the first address signal ADR from the CPU 11
1 is set to “M”, and the first bus line B1 is set to “M”.
The first data signal DATA1 having the value D is stored in the line memory 31. This requires CPU1
1, the first address signal ADR1 on the fifth bus line B5 is set to "M", and the value D is output as the first data signal DATA1 to the first bus line B1. Next, by setting the write signal WR on the fifth bus line B5 to "1", the density data D is written into the M address of the line memory 31. After that, the CPU 11 sets the first address signal ADR1 to "M+1" and outputs the write signal again.
Set WR to “1”. As a result, data D is also written to address (M+1) of the line memory 31.

By the way, direction b in FIG. 1 is assumed to be the sub-scanning direction during recording. Therefore, initially, the pulse motor 81 is reversed to move the base 75 in the direction opposite to the b direction and return to the recording start position (not shown). In this state, each counter in the CPU 11 is cleared to the initial state. This CPU 11 includes an integration counter CNTX in the drum rotation direction, a 4-ary counter CNTY in the horizontal axis direction, and a drum rotation direction position (address).
It includes an X position counter CNPX and a Y position counter for the position in the horizontal axis direction.

Since one pixel is composed of 4 x 4 dots, the CPU
It is assumed that one pulse of the sub-scanning signal 79 from 11 causes the base 75 to advance in pitch by 1/4 pixel. Therefore, in preparation for moving to the address (M, N), the base 75 is advanced from the recording start position by 4N pulses. This results in
This means that the IJ head 47 is placed at a predetermined position in the horizontal axis direction Y. Next, the detector 85
detects the recording start position in the drum rotational direction and generates a recording start signal STR. This signal STR
As a result, the integration counter CNTX in the CPU 11 is activated and counts the output pulses 73 generated by the rotary encoder 71. That count is
Recording starts when 4M is reached. by the way,
On the recording side, the pixel position in the drum rotation direction is calculated using a value obtained by reducing the output of the rotary encoder 71 to 1/4. That is, an X position counter that counts the output pulses of the rotary encoder 71.
When the counting state of CNPX is 0 to 3, the data stored at address 0 in the line memory 31 is output, and when the counting state of counter CNPX is 4 to 7, the data stored at address 1 in the line memory 31 is output. Output some data. In this way, an address in the line memory 31 at the time of reading is designated by an integer value that is 1/4 of the integrated value of the output pulses 73 generated by the rotary encoder 71 from the recording start position. Clearing the counter CNTX is
Recording stop signal detected by detector 87
Performed by STP. Therefore, the integration counter
When the count state of CNTX reaches 4M, address M of the line memory 31 is accessed. Then, the CPU
A write signal WR is output from the line memory 31, and the data D stored in the address M of the line memory 31 is
Second bus line B2 as data signal DATA2
It is supplied to PG33 via. In that state,
The second address signal ADR2 output from the CPU 11 via the fifth bus line B5 is set to address 0.
As a result, the 4×4 stored in PG33
One column of the data pattern consisting of dots is selected,
The third data signal DATA3 is supplied to the P/S converter 35 via the third bus line B3. Note that the third data signal DATA3 in this case is the first column data R1 consisting of picture elements 1 to 4 of the pattern shown in FIG. Therefore, these picture elements 1~
Each data of 4 is sequentially output by the P/S converter 35 and becomes a serial signal 41. In response to this signal 41, the IJ head 47 controls the concentration D shown in FIG.
A dot pattern of picture elements 1 to 4 is printed corresponding to the pattern. This ink ejection operation is performed sequentially in synchronization with the output pulses 73 from the rotary encoder 71. Therefore, after counting 4 pulses for printing picture elements 1 to 4, it is necessary to set the address of the line memory 31 to (M+1). Therefore, the counter
CNTX is 4M+4CNPX (M+1), CNPY is N, and the second address signal ADR2 is 0.

Since data of density D is also stored at address (M+1) of the line memory 31, the second data signal DATA2 becomes data of density D again. Therefore, as in the case of address M described above, picture elements 1 to 4 in the first column in the pattern shown in FIG. 2 are printed with four dots in the first column of pixel address (M+1,N). . When picture elements 1 to 4 at this address (M+1, N) are printed, the counting state of the counter CNTX that integrates the output pulses of the rotary encoder 71 is 4M.
It becomes +8. However, since the data stored after addresses 0 to (M-1) and (M+2) in the line memory 31 is a blank area that is not printed, the density is zero, so the printing of the first column after address (M+2) is Not done.

The drum rotates and reaches the recording stop position. The detector 87 detects the stop position and issues a recording stop signal.
STP occurs. In response, the CPU 11 advances the pulse motor 81 by one step to move the base 75 to b.
direction, and the printing position by the IJ head 47 is shifted by one picture element. The counting state of the counter CNTY, which performs integration in the horizontal axis direction in the CPU 11, becomes 1, and preparations are made for printing the second row of picture elements 5 to 8 in the pattern shown in FIG. In this state,
The second address signal ADR2 is set to 1 by the CPU 11.
shall be. When the drum 51 rotates and the recording start position is detected by the detector 85, a recording start signal is generated.
STR is supplied to the CPU 11, the counter CNTX is energized, and the output pulse 7 of the rotary encoder 71 is
Count 3. When the counting state reaches 4M, the second address signal ADR2 is set to 0, and printing is started in the same manner as described above. In this case, the dot print is
This is performed based on picture elements 5 to 8 in the second row R2 in the pattern shown in FIG. Similarly, the count of counter CNTX in CPU11 is (4M
+4) to (4M+7), the address (M
+1) pixel 5 of second column data R2
8 to 8 print dots one after another, completing the printing of the second row. Below, in the same way, the counter in CPU11
Let the count of CNTY be 2 or 3, and the third one accordingly.
Picture elements 9 to 12 of column data R3, fourth column data R4
For each of picture elements 13 to 16, dots are sequentially printed for pixels at addresses M and (M+1). In this way, as shown in FIGS. 3A and 3B, the addresses (M,N) and (M+
Two pixels (1, N) are recorded.

Next, it is necessary to record the two pixels on the right shown in FIGS. 3A and 3B. In this case, since the test pattern data representing the density D has already been written into the line memory 31 by the CPU 11 as described above, there is no need to write it again. Therefore,
Exactly the same operation may be performed except that the Y position counter CNPY in the CPU 11 is set to N+1.

In this way, the density of the dot pattern recorded at position A can be adjusted to position B using the configuration shown in FIG.
Read at The signal 67 obtained by such readout is used as the second readout signal from the CPU 11.
A/D conversion is performed by READ2. The digital data signal SAD resulting from the conversion is taken in as density data to the CPU 11 via the fourth bus line B4. A comparator in the CPU 11 calculates the difference between the imported concentration measurement data and the known concentration value.
A control signal CONT representing the difference is supplied to the voltage control section 91 via the fifth bus line B5.

FIG. 6 shows the head driver 4 shown in FIG.
3. IJ by IJ head 47 and voltage control section 91
The control section is shown. Note that this circuit is a modification of the constant voltage circuit. Here, 611 is a D/A converter that converts the digital amount of head voltage setting data into analog amount based on the voltage control signal CONT supplied from the CPU 11, 613 is a head drive power supply, and 615
is a series transistor 617 that controls the voltage to the head 47 according to the data of the control signal CONT.
is an error detection transistor, 619 is a Zener diode that determines the reference voltage, and 621 is for switching.
FETs, R _r1 to R _r4 are resistors. A P/S converter 9 is connected to the gate of FET621 as shown in FIG.
A serial signal 41 from 1 is supplied.

A voltage control signal that indicates the difference between the measured concentration and the known concentration as a digital amount is added to the circuit configured in this way.
CONT is converted into an analog signal by the D/A converter 611 and controls the voltage applied to the IJ head 47. For example, if the reference head drive voltage during test pattern recording is 50V, data equivalent to 50V is output from the CPU 11 to the D/A converter 611 in the voltage control section 91. The reference concentration value at this time is
Set it to 0.5. However, if the density value as a result of the density measurement is 0.4, the CPU 11 assumes that the recording density is 0.1 less and operates to increase the head drive voltage and increase the amount of ink ejection. As a result, data corresponding to 60V is commanded from the CPU 11 to the D/A converter 611, the ink ejection amount is increased with a head drive voltage of 60V, and the test pattern is again recorded in the same manner as described above. As a result, the pattern density increases, and this is read again by the density detector and the CPU 11
This operation is repeated until the error between the known concentration and the measured concentration value falls within a predetermined range. If ink does not come out due to head clogging, etc., an interlock routine is included in the optimal head applied voltage control routine described above, and an alarm is issued if the ink does not fall within a predetermined error range even after several times of control. Good too.

Also, the orifice diameter of the head 47 is 20μm to 15μm.
If it is about m, depending on the combination with the ink, it may be difficult to produce the first dot after recording is stopped. If the control method of this embodiment is used, the head drive voltage is automatically increased, the ink is ejected, and then the dot diameter is controlled to converge to the optimum dot diameter. It also has the advantage of improving reliability.

In this embodiment, an IJ head is used as the recording section, but any other recording section may be used as long as the recording dot diameter can be varied.

In this way, in this embodiment, a dot pattern is formed on the recording material according to data representing a predetermined density,
The dot diameter is controlled by detecting the image density of the dot pattern and comparing the detected image density with the predetermined density.

With this configuration, the required density is always reproduced, so high-quality images can be obtained.

Particularly when an ink jet head is used, changes in the material of the recording material, the composition of the ink, or changes in the environment are likely to cause changes in the viscosity of the ink and the degree to which it soaks into the paper. According to this embodiment, the density on the recording material is directly detected, and the ejection amount of the IJ head is feedback-controlled based on the detection output, so even if the above-mentioned changes occur, extremely stable and good image density can be obtained. becomes possible.

The present invention as described above is a dot signal generating means that develops a given density signal into dots and generates a dot signal for displaying halftones in a dot format with a dot density corresponding to the density of the density signal. and control means for inputting a test signal of intermediate density to the dot signal generating means to generate a dot signal having a dot density in a predetermined matrix size corresponding to the intermediate density of the test signal;
A recording means for recording information by discharging a recording agent onto a recording material based on a given dot signal, and a dot signal generated from the dot signal generating means in response to the test signal of the intermediate density for testing. means for reading dots recorded on the recording material by the recording means, the dots having a size related to the matrix size set so as to obtain an average density of the predetermined matrix size; The apparatus includes an aperture size reading means, and a means for changing the driving amount of the recording means in accordance with the average density of the aperture size read by the reading means.

According to the present invention, since a dot signal having a dot density corresponding to a test signal of an intermediate density value is generated and recording is performed using such a dot signal, it is possible to appropriately detect the recording state of an intermediate density. Furthermore, when reading dots corresponding to recorded intermediate density values, the average density of an aperture size related to the matrix size set so as to obtain the average density of a predetermined matrix size is read. Even if the test signal corresponding to the density value is converted into sparse dots, or even if the relative position of the recording material and the reading means is slightly shifted, it is possible to detect a sufficiently accurate average density. It's all about what you can do. Therefore, the driving amount of the recording means can be changed with high precision, and the printing density can be controlled with high precision with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a recording device to which the present invention is applied, FIG. 2 is a diagram showing a test pattern, and FIGS. 3A and B are diagrams showing an example in which four test patterns of FIG. 2 are recorded. , FIG. 4 is a diagram showing pixel addresses on the recording drum, FIG. 5 is a block diagram showing the recording pixel reading section, and FIG. 6 is a block diagram showing the inkjet control section. 11... Arithmetic control device, 23... Monitor receiver,
31... Line memory, 33... Pattern generator, 47... Inkjet head, 51... Recording drum, 71... Rotary encoder, 81... Pulse encoder, 613... Head drive power supply, 617
...Error detection transistor, 621...Switching FET, ART...Aperture.

Claims (1)

[Scope of Claims] 1. A dot signal generating means that develops a given density signal into dots and generates a dot signal having a dot density corresponding to the density of the density signal and for displaying halftones in dot format. and control means for inputting a test signal of an intermediate density to the dot signal generating means to generate a dot signal having a dot density in a predetermined matrix size corresponding to the intermediate density of the test signal. a recording means for recording information by ejecting a recording material onto a recording material based on a dot signal; means for reading dots recorded on the recording material by a recording means, the aperture size being set in relation to the matrix size so as to obtain an average density of the predetermined matrix size; A recording device comprising: reading means; and means for changing the drive amount of the recording means in accordance with the average density of the aperture size read by the reading means.