KR19980063960A - Method and method for measuring ink emissions, method for measuring ink emissions from apparatus, printing apparatus, and printing apparatus - Google Patents

Abstract

A method of immediately measuring the amount of ink discharged from a nozzle is disclosed. The ink discharge measuring method includes a line pattern forming step of forming a line pattern by ejecting ink from an inkjet printhead; A first image sensing step of sensing the line pattern by an image sensing element; A second image sensing step of sensing portions other than the line pattern by the image sensing element; A density for dividing the luminance value of the portion detected in the second image sensing step by the luminance value of the line pattern detected in the first image sensing step and calculating the common number to calculate the density of each pixel of the line pattern. Calculating step; An integration step of integrating the density of each pixel of the entire line pattern calculated in the density calculation step; And an ink discharge determination step of obtaining the ink discharge based on the integration concentration calculated in the integration step.

Description

Method and method of measuring ink discharge, ink emission measurement method in apparatus, printing apparatus, and printing apparatus

The present invention relates to a method and apparatus for measuring ink discharge, a method for measuring ink discharge discharged by a printing apparatus and a printing apparatus, and in particular, an inkjet having fine nozzles for discharging a small amount of ink from each nozzle. A method and apparatus for measuring the amount of ink discharged by a single ejection operation of a printhead, such as used in a printer.

In an apparatus such as an inkjet printer having a printhead composed of a plurality of fine nozzles, in order to stabilize the print quality, it is important to control the ink discharge discharged from each nozzle to be uniform. For this purpose, it is desired to accurately and immediately obtain the ink discharge discharged from each nozzle.

As a well-known method of measuring the minute amount of colored ink droplets (for example, color ink), there are (1) a weighing method and (2) an absorbance method.

Hereinafter, the case where the ink discharge | emission discharged from the nozzle of an inkjet printer is measured by the said two methods is demonstrated.

(1) gravimetric method

In this method, the ink is discharged at regular intervals for a certain time, and the amount of ink (weight) used within that time is measured by chemical balance or the like (care must be taken to minimize evaporation of the ink during this operation). Thereafter, by dividing the used ink by the number of times the discharge operation is performed, the average amount of ink droplets (average discharge) in each discharge operation can be obtained.

(2) absorbance method

This method takes advantage of the relationship between solution concentration and light absorption, known as Lambert-Beer's law. Specifically, a solution having a certain concentration is poured into a transparent container having a certain depth, the container is irradiated with light having intensity I ₀ from one side, and then the intensity I of the light transmitted through the solution in the container is measured. Since some of the incident light is absorbed by the solution in the container, the intensity of the light decreases as it passes through the solution. It is known that the intensity falls in proportion to the concentration of the solution. If A is defined as absorbance, the relation of this law can be expressed by the following equation.

A = -Log (I ₀ / I) = ab

Where a is the slope, b is the depth of the solution and c is the concentration of the solution. By using this equation, a calibration-line showing the relationship between the concentration and the absorbance is obtained in advance for the ink to be used. Next, the ink is discharged from the nozzle toward a known volume of transparent solution (preferably a solution with the smallest possible light absorption), and then the absorbances by the solution containing the discharged ink after each discharge operation, i.e. the number of discharge operations Measure the absorbances corresponding to. From the measured absorbance and the previously obtained calibration curve, the concentration of the solution containing the ink is determined. Then, the amount of ink mixed in the solution can be obtained by considering the amount of the initial solution. The obtained ink amount is divided by the number of discharge operations to obtain an average amount of ink discharged by each discharge operation.

However, according to the above two conventional methods, it is necessary to discharge a certain amount of ink, and therefore it is impossible to immediately obtain the ink discharge discharged from each nozzle. As an experiment, the applicant of this invention measured the ink discharge | emission discharge | emission per nozzle by the weight method, discharged the ink equivalent to 500,000 dots, and found out that it took 12 minutes for the measurement. Therefore, it takes quite a long time to measure the ink emissions per nozzle of an inkjet printer with an inkjet printhead of 64 or 128 fine nozzles. In addition, in the above two methods, since the ink amount for each discharge operation is averaged, it is impossible to measure the actual ink discharge amount discharged per nozzle by one discharge operation.

The present invention has been made in view of the above situation, and an object thereof is a method and apparatus for immediately measuring the amount of ink discharged from a nozzle.

Another object of the present invention is to provide a printing apparatus having the above-described measuring apparatus and a method of measuring the amount of ink discharged from the printing apparatus.

In order to solve the above-mentioned problems and achieve the object, the method of measuring the ink discharge amount according to the first aspect of the present invention is characterized by the following configuration.

Specifically, the method for measuring the discharge amount of ink discharged from the inkjet printhead by one discharge operation includes a line pattern for forming a line pattern on the predetermined member by discharging ink onto the predetermined member from the printhead. Forming step; A first image sensing step of sensing the line pattern by an image sensing element; A second image sensing step of sensing, by the image sensing element, portions other than the line pattern on the predetermined member; For each pixel of the image sensing device, the luminance value of the portion detected in the second image sensing step is divided by the luminance value of the line pattern detected in the first image sensing step, and the common logarithm is calculated to calculate the common logarithm. A density calculation step of calculating a density of each pixel of the line pattern; An integration step of integrating the density of each pixel of the entire line pattern calculated in the density calculation step; And an ink discharge determination step of obtaining the ink discharge based on the integration concentration calculated in the integration step.

In addition, the method for measuring the ink discharge amount according to the second aspect of the present invention is characterized by the following configuration.

Specifically, the method for measuring the discharge amount of ink discharged from the inkjet printhead by one discharge operation includes the discharge amount of ink discharged by one discharge operation from each of the plurality of ink discharge nozzles of the printhead under a predetermined condition. Preliminary measuring step of measuring in advance; An ink dot formed by ink discharged from the two or more nozzles having different ink discharge nozzles among the plurality of ink discharge nozzles on the predetermined member under the predetermined condition and discharged by the two nozzles; A first concentration measuring step of measuring the concentration of these; Based on the data indicating the density of ink dots formed by the ink discharged by the two nozzles obtained in the first density measuring step and the data indicating the ink discharge rate obtained in the preliminary measuring step for the two or more nozzles. A calibration curve generation step of obtaining a calibration curve representing a correlation between the ink discharge volume discharged by one discharge operation and the concentration of the ink dot; A line pattern forming step of forming a line pattern on the predetermined member by ejecting ink on the predetermined member from any nozzle of the printhead under any condition; A first image sensing step of sensing the line pattern by an image sensing element; A second image sensing step of sensing, by the image sensing element, portions other than the line pattern on the predetermined member; For each pixel of the image sensing device, the luminance value of the portion detected in the second image sensing step is divided by the luminance value of the line pattern detected in the first image sensing step, and the common number is calculated to calculate the common number. A density calculation step of calculating the density of the pixel; An integration step of integrating the density of each pixel of the entire line pattern calculated in the density calculation step; And an ink discharge determination step of obtaining an ink discharge discharged from the arbitrary nozzles under the arbitrary conditions based on the integration concentration calculated in the integration step and the calibration curve.

In addition, the ink discharge measuring apparatus according to the present invention is characterized by the following configuration.

Specifically, the apparatus for measuring the discharge amount of ink discharged from the inkjet printhead by one discharge operation includes: a receiving medium for receiving ink discharged from the printhead; An image sensing element for sensing a line pattern formed on the accommodation medium by the discharged ink and portions other than the line pattern; A first value for dividing the luminance value of the portion other than the line pattern sensed by the image sensing element by the luminance value of the line pattern for each pixel and calculating the common number to calculate the density of each pixel and to integrate the obtained density Calculation means; Memory means for storing a calibration curve indicating a correlation between ink discharge and a concentration of ink dots formed on the receiving medium by the discharged ink; And second calculating means for calculating the ink discharge amount based on the integrated concentration of the line pattern obtained by the first calculating means and the calibration curve.

Moreover, the printing apparatus which concerns on this invention is characterized by the following structures.

Specifically, the printing apparatus having a function of measuring the discharge amount of ink discharged from the inkjet printhead by one discharge operation, and performing printing using the inkjet printhead for discharging ink by an inkjet method, the printhead An accommodation medium for containing the ink ejected from the cartridge; An image sensing element for sensing a line pattern formed on the accommodation medium by the discharged ink and portions other than the line pattern; Dividing the luminance value of the portion other than the line pattern sensed by the image sensing element by the luminance value of the line pattern for each pixel, calculating the common number, calculating the density of each pixel, and integrating the obtained density. 1 calculation means; Memory means for storing a calibration curve indicating a correlation between ink discharge and a concentration of ink dots formed on the receiving medium by the discharged ink; And second calculating means for calculating the ink discharge amount based on the integrated concentration of the line pattern obtained by the first calculating means and the calibration curve.

In addition, the method for measuring the discharge amount of ink discharged from the printing apparatus according to the first aspect of the present invention is characterized by the following configuration.

Specifically, the method for measuring the discharge amount of ink discharged from the printing apparatus having an inkjet type printhead, a line pattern forming step of forming a line pattern on the predetermined member by discharging ink on the predetermined member from the printhead ; A first image sensing step of sensing the line pattern by an image sensing element; A second image sensing step of sensing, by the image sensing element, portions other than the line pattern on the predetermined member; For each pixel of the image sensing device, the luminance value of the portion detected in the second image sensing step is divided by the luminance value of the line pattern detected in the first image sensing step, and the common number is calculated to calculate the common number. A density calculation step of calculating the density of the pixel; An integration step of integrating the density of each pixel of the entire line pattern calculated in the density calculation step; And an ink discharge determination step of obtaining the ink discharge based on the integration concentration calculated in the integration step.

In addition, the method for measuring the discharge amount of ink discharged from the printing apparatus according to the second aspect of the present invention is characterized by the following configuration.

Specifically, the method for measuring the discharge amount of ink discharged from a printing apparatus having an inkjet type printhead, in advance, the discharge amount of ink discharged by one discharge operation from each of the plurality of ink discharge nozzles of the printhead under a predetermined condition. Preliminary measuring step of measuring; An ink dot formed by ink discharged from the two or more nozzles having different ink discharge nozzles among the plurality of ink discharge nozzles on the predetermined member under the predetermined condition and discharged by the two nozzles; A first concentration measuring step of measuring the concentration of these; Data representing the density of the ink dots formed by the ink discharged by the two nozzles obtained in the first density measuring step and data representing the ink discharge rate obtained in the preliminary measuring step for the two or more nozzles. A calibration curve generation step of obtaining a calibration curve representing a correlation between the ink discharge volume discharged by one discharge operation and the concentration of the ink dot based on the basis; A line pattern forming step of forming a line pattern on the predetermined member by ejecting ink on the predetermined member from any nozzle of the printhead under any condition; A first image sensing step of sensing the line pattern by an image sensing element; A second image sensing step of sensing, by the image sensing element, portions other than the line pattern on the predetermined member; For each pixel of the image sensing device, the luminance value of the portion detected in the second image sensing step is divided by the luminance value of the line pattern detected in the first image sensing step, and the common number is calculated to calculate the common number. A density calculation step of calculating the density of the pixel; An integration step of integrating the density of each pixel of the entire line pattern calculated in the density calculation step; And an ink discharge determination step of obtaining an ink discharge discharged from the arbitrary nozzles under the arbitrary conditions based on the integration concentration calculated in the integration step and the calibration curve.

Those skilled in the art will be apparent from the following description of the preferred embodiment of the present invention other objects and advantages other than those discussed above. In the description, reference is made to the accompanying drawings which form a part hereof and which show an example of the invention. However, such examples do not unnecessarily show the various embodiments of the present invention, and therefore, reference is made to the claims that determine the scope of the invention following the description.

1 is a block diagram of an apparatus for measuring ink discharge amount according to a first embodiment of the present invention.

2 is a diagram showing an example of a line pattern printed using an inkjet printer.

3 is a diagram illustrating an example in which a window having a fixed size is set in a line pattern to be measured.

4 is a diagram showing an aspect in which windows are divided for each pixel;

5 is a graph showing an example of a calibration curve based on experiments according to the embodiments.

6 shows a printing device incorporating a device for measuring ink discharge rate.

7 is a configuration diagram of an inkjet printhead.

8 is an explanatory diagram showing a method of controlling the amount of ink discharged by changing pulse widths applied to a heater.

FIG. 9 is an explanatory diagram showing a method of correcting a difference in the amount of ink discharged from the nozzles; FIG.

10 is an explanatory diagram showing a method of correcting a difference in the amount of ink discharged from the nozzles;

FIG. 11 is an explanatory diagram showing a method of correcting a difference in the amount of ink discharged from the nozzles; FIG.

12 is an explanatory diagram showing a method of changing the print density.

Fig. 13 is an explanatory diagram showing a method of changing the print density.

14 is an explanatory diagram showing a method of changing the print density.

Explanation of symbols for the main parts of the drawings

1: image processing device

2: personal computer

3: optical system

4: XY stage

5: line sensor camera

6: light source

10: glass substrate

12: ink absorption layer

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First embodiment

1 shows a configuration of an apparatus for measuring ink discharge amount according to a first embodiment of the present invention. Reference numeral 1 denotes an image processing apparatus for measuring the density of ink dots; (2) includes a personal computer (hereinafter referred to as a PC) used to control the image processing apparatus 1 and the XY control stage 4; (3) an optical system for enlarging an image; (4), XY control stage used when measuring the density | concentration of an object continuously; (5), a line sensor camera for inputting an image of a measurement target into the image processing apparatus 1; And (6) indicates a light source provided under the XY control stage 4. The center part of the surface of the XY control stage 4 consists of glass, and a measurement object can be irradiated with the light source provided under glass, and a target image can be input by the line sensor camera 5. Thus, in this structure, the positional relationship of the line sensor camera 5 and the light source 6 is fixed. The PC 2 controls the XY control stage 4 through the RS232C or GPIB interface, and controls the image processing apparatus 1.

2 is an example of a line pattern printed on a glass substrate 10 by a plurality of different nozzles of an inkjet printer. In FIG. 2, the same nozzle direction represents the printing direction of ink dots ejected from the same nozzle, and the different nozzle direction represents the printing direction of ink dots ejected from the plurality of different nozzles in one ejection operation. Since the ink and the glass are not compatible with each other, it is necessary to apply a special treatment to the glass substrate 10 to mediate the discharged ink and the glass substrate 10 (in this example, polyvinyl alcohol is applied to the glass substrate Ink absorption layer 12 is formed). Thanks to this processing, the ink discharged from each nozzle during one discharge operation is uniformly absorbed by the ink absorbing layer to form a line pattern as shown in FIG. As the material of the ink absorbing layer 12, a material that is as transparent and colorless as possible (ie, does not absorb light) is preferable.

The image is imaged by the line sensor camera 5 under the condition that the optical system 3 is focused on the printed line pattern as shown in FIG. 2 and the magnification of the optical system 3 and the intensity of the light source 6 are appropriately adjusted. Enter. Although the magnification is 5 in this embodiment, the present invention is not limited to this magnification. The line sensor camera 5 is a monochrome camera. The image input by the line sensor camera 5 is formed in the minimum pixel unit that the image processing apparatus 1 can decompose (this apparatus uses an A / D converter having 8 bits), and each minimum pixel is A luminance level of 256 tones between 0 and 255 may be expressed corresponding to the intensity of light transmitted through each pixel.

Next, a method of measuring the density of the line pattern (corresponding to the ink discharge discharged from each nozzle) will be described.

In this embodiment, the concentration is expressed by the following equation.

Pixel Density = Log (pixel reference luminance / pixel luminance)

This will be described below in detail. In this embodiment, the density of the line pattern is determined by how much the incident light is absorbed while passing through the line pattern having the color (density) to be measured. The higher the concentration of the line pattern to be measured, the more light is absorbed and the intensity of the transmitted light decreases. Therefore, the luminance level of the minimum pixel in the area of the line pattern to be measured decreases. In contrast, when the density of the line pattern is low, the luminance level of the minimum pixel should be high. This embodiment focuses on this fact and replaces the density with the light absorption rate (although the luminance level measured by the image processing apparatus 1 is actually).

Thereafter, a frame (hereinafter referred to as a window) having a fixed size is set for the image of the line pattern which is the measurement target input by the line sensor camera as described above. The window is composed of n x m pixels as shown in Fig. 4 (because of using a line sensor camera, the m pixels are scanned in the width direction of the line pattern for m pixels to obtain an image as shown in Fig. 4). . Here, the luminance level (pixel luminance: Qnm) of each pixel is obtained. In addition, a window having the same size is set in the image of the portion (plain glass portion) without the line pattern to obtain the luminance level (pixel reference luminance: Inm) of each pixel. The pixel reference luminance is shown in the portion indicated by the broken line in FIG. 4 in the window. Then, the pixel concentration for each of the corresponding pixels is calculated by the following equation based on the above equation (1).

Pixel Density Dnm = Log (pixel reference luminance Inm / pixel luminance Qnm)

Using Equation 2, the concentration for each pixel is obtained. The density of the entire window is obtained by summing all the pixel concentrations Dnm (that is, the density of all the pixels in the window) obtained for n = 1 to n and m = 1 to m.

The window size may be arbitrarily determined in consideration of the size of the line pattern to be measured (the window size should be at least large enough to cover the entire line pattern). If the window size is set too large for the line pattern, the low density pixels around the line pattern will be pixel density Inm ≒ Qnm. Substituting this into equation (2) yields the following equation.

Pixel Density Dnm = Log (Inm / Qnm) ≒ Log1 = 0

Specifically, if a window whose size is too large on the line pattern is set, the pixels with low density around the line pattern will be pixel density ≒ 0. Therefore, even if the pixel concentration # 0 is added, the sum of the pixel concentrations in the window does not change much. In other words, if a window whose size is too large on the line pattern is set, the obtained concentration will substantially represent only part of the line pattern. Thus, according to the method of the present invention, the exact concentration of the line pattern is calculated regardless of the window size.

The XY control stage 4 is controlled by the PC 2 to read the line pattern continuously. Thereafter, by setting a window to the line pattern, the density of the entire line pattern can be obtained.

Based on the line pattern obtained by the above-mentioned method, the ink discharge | emission discharged by one discharge operation | movement of the nozzle which printed the line pattern using the calibration curve mentioned later is calculated | required.

Assuming that the line pattern is formed in the ink ejected for 50 times, the density of the line pattern obtained above is the sum of the concentrations of the ink dots corresponding to 50 times the ejected ink. Therefore, to obtain the ink discharged by one discharge operation based on the calibration curve, the density of the line pattern is divided by the number of discharged ink discharged to form the line pattern.

The following describes a method for obtaining a calibration curve used as a reference for measuring the amount of ink discharged by any nozzle of the inkjet printhead by one discharge operation under any condition. In the following description, the ink discharged by one discharge operation is usually a drop of ink. However, since the ink may not form a drop, the expression of the discharged ink discharged by one discharge operation is used instead of a drop of ink.

As a first step, the ink discharges discharged from two or more different nozzles of the plurality of nozzles of the inkjet printhead, which are the targets of the ink discharge measurement, are measured using the gravimetric method or the absorbance method described as the prior art. Here, it is desirable for each of the two or more different nozzles to have as many different emissions as possible under certain conditions.

In this embodiment, the ink discharges discharged by one discharge operation from four different nozzles each having different discharges under a predetermined condition are measured in advance by gravimetric method.

Next, the ink discharges by one discharge operation discharge the ink on the glass substrate 10 under the same conditions as above from the four nozzles obtained as described above. The concentration of ink dots (which may be a line pattern) formed on the glass substrate 10 is measured by the same method as described above. By performing the above measurement, the ink discharge amounts discharged from the four nozzles and the density of the ink dots formed by the discharged ink are obtained in a one-to-one correspondence relationship. The density data of the ink dots formed by the four nozzles is obtained based on the average value of the concentrations of the 50 samples of the printed dots. The standard deviation of the concentration data in this measurement was within 5% of the mean value.

FIG. 5 is a graph showing a relationship between the ink discharge amount discharged by one discharge operation and the concentration of ink dots formed on the glass substrate 10 by the discharged ink. In Fig. 5, the black dots represent the ink ejection discharged by the four nozzles and the concentration of the ink dots. It can be seen from FIG. 5 that the four points are located on a substantially straight line. Therefore, by drawing a straight line passing through the four points, the density of the ink dot corresponding to any ink discharge on the straight line can be obtained in a one-to-one correspondence relationship. I will call this straight line a calibration curve.

Since the calibration curve is represented by a straight line, at least two points need to be displayed on the graph to obtain the calibration curve. Therefore, instead of using four nozzles as described above, at least two nozzles can be used to obtain a calibration curve. However, since the data representing the ink emissions measured by the gravimetric method or the absorbance method are used to obtain the calibration curve, the accuracy of the measurement method directly affects the accuracy of the measurement of the ink emissions. Therefore, it is considered desirable to find the calibration curve using two or more nozzles. In addition, the calibration curve needs to be measured again every time the ink used changes.

In the above-described method, by measuring the concentration of the line pattern formed by the ink discharged from the arbitrary nozzles under arbitrary conditions, the discharge amount of the ink discharged from each nozzle can be obtained by referring to the calibration curve.

If the data indicating the obtained calibration curve are stored in the memory of the PC 2, the concentration measurement data can be immediately converted into the emission data by using the PC 2.

Next, a printing apparatus having a function of measuring the ink discharge amount will be described.

6 shows a printing apparatus incorporating an apparatus for measuring ink ejection. In Fig. 6, reference numeral 51 denotes a personal computer (hereinafter referred to as a PC) for controlling the printing apparatus and the apparatus for measuring the ink discharge amount, having an image processing function; 52, a main body of the printer; 53, a printer stage on which a print medium is set; And 54 denotes an inkjet printhead which performs printing while moving left and right. Reference numeral 55 denotes a print medium such as paper; 56 a line sensor camera; 57, a microscope for enlarging printed line patterns; 58, a microscope stage (empty to use a light source); 60, a transparent substrate, such as a glass substrate; And 61 denotes a roller used to move the transparent substrate 60 on the stage 58 for the microscope 57.

In the apparatus, the print head 54 prints on the print medium 55 while moving in the left and right directions. After printing a predetermined time or a predetermined number of lines, the printhead 54 moves to the transparent substrate 60 to print a line pattern using nozzles currently in use. The printed line pattern on the transparent substrate 60 is moved under the microscope 57 to measure the density of the line pattern according to the above-described method using the light source 59 and the line sensor camera 56. Next, the PC 51 immediately converts each measured concentration into ink discharge with reference to the calibration curve obtained in advance. If the ink discharge amount is outside the predetermined range, for example, the pulse discharge amount applied to the printhead or the like is changed to appropriately control the ink discharge amount discharged from the nozzle.

In this case, the printer does not need to interrupt the printing operation from the time when the printhead 54 finishes printing the line pattern on the transparent substrate 60 to the time when the ink discharge is calculated, that is, the calculation and printing of the ink discharge The actions can be performed in parallel.

Further, by developing a print pattern of several lines on the image memory of the apparatus, the PC 51 can predict which nozzles are used continuously and for how long. The PC 51 determines the timing of measuring ink discharge based on the prediction. Therefore, depending on the printing pattern, there may be a case where no ink discharge is measured during the printing operation. This series of control can be arbitrarily changed by changing the control program stored in the PC 51.

Hereinafter, the structure of the inkjet printhead and the method of controlling the ink discharge | emission discharged from the inkjet printhead are demonstrated.

Fig. 7 is a diagram showing the configuration of the inkjet printhead IJH.

Referring to FIG. 7, an inkjet printhead IJH is a heater substrate 104, which is usually a substrate on which a plurality of heaters 102 for heating ink are formed, and a ceiling plate mounted on the heater substrate 104. plate, 106). The ceiling plate 106 is formed with a plurality of outlets (nozzles) 108. At its rear, tunnel-like fluid passages 110 are formed which communicate with the outlets. Each of the flow paths 110 is separated from adjacent flow paths by the partition walls 112. Each of the flow paths 110 is commonly connected to one ink chamber 114 at the rear thereof. Ink is supplied to the ink chamber 114 through the ink inlet 116 and then supplied to each flow path 110 from the ink chamber 114.

The heater substrate 104 and the ceiling plate 106 are arranged so that the position of each heater 102 matches the position of the corresponding flow path 110, and is assembled in the state shown in FIG. 7 shows only two heaters 102, the heaters 102 are actually arranged corresponding to each flow path 110. When a predetermined driving pulse is supplied to the heater 102 in the assembled state shown in FIG. 7, film boiling occurs in the ink above the heater 102 to form bubbles, and the ink is formed by the volume expansion of the bubbles. Is extruded from the outlet 108 and discharged. Therefore, by controlling the drive pulse applied to the heater 102, for example, the size of the bubble can be adjusted by controlling the size of electric power. That is, the volume of ink discharged from each discharge port can be controlled as desired.

FIG. 8 is a timing diagram for explaining a method of controlling ink discharge by changing the power supplied to each heater as described above.

In this embodiment, two types of constant voltage pulses are applied to each heater 102 in order to adjust the amount of ink discharged. The two pulses are a preheat pulse and a main heat pulse (hereinafter simply referred to as a heat pulse) as shown in FIG. 8. The preheat pulse is a pulse for heating the ink to a predetermined temperature before actually ejecting the ink. The pulse width of this pulse is set to a value smaller than the minimum pulse width t5 required for discharging ink. Therefore, ink is not discharged by this preheat pulse. This preheat pulse is applied to each heater 102 in order to raise the initial temperature of the ink to a predetermined temperature in advance so that ink discharge is always constant when applying a constant temperature to the heater 102 later. Alternatively, the temperature of the ink can be adjusted in advance by adjusting the width of the preheat pulse. In this case, the ink discharge rate may change for the same heat pulse. In addition, by heating the ink before the application of the heat pulse, the preparation time required for discharging the ink upon application of the heat pulse can be shortened, thereby improving the responsiveness of the printhead to the heat pulse.

The heat pulse is actually a pulse for discharging ink. The pulse width of the heat pulse is set to a value larger than the minimum pulse width t5 required to discharge the ink. The energy generated by each heater 102 is proportional to the width (applied time) of the heat pulse. Therefore, the deviation of the characteristics of the heaters 102 can be adjusted by adjusting the width of each heat pulse.

Ink discharge may be adjusted by adjusting the interval between the preheat pulse and the heat pulse to control the diffusion state of the heat upon application of the preheat pulse.

As apparent from the above description, the ink discharge amount may be controlled by adjusting the application time of the preheat pulse or the heat pulse, or may be controlled by adjusting the interval between the application time of the preheat pulse and the application time of the heat pulse. Therefore, by adjusting the application time of the preheat pulse or the heat pulse, or the interval between the application time of the preheat pulse and the application time of the heat pulse, the responsiveness of the printhead to the ink discharge or the applied pulse as desired. I can adjust it.

Next, the adjustment of such ink discharge | emission is demonstrated.

As shown in Fig. 8, assume that different amounts of ink are discharged from the discharge ports (nozzles) 108a, 108b, 108c upon application of the same energy. Specifically, when a predetermined energy is applied at a predetermined temperature, the ink discharged from the nozzle 108a is 36 pl (pico liter); The amount of ink discharged from the nozzle 108b is 40 pl; The amount of ink discharged from the nozzle 108c is 40 pl; Assume that the resistances of the heaters 102a and 102b corresponding to the nozzles 108a and 108b are 200 Ω, and the resistance of the heater 102c corresponding to the nozzle 108c is 210 Ω. Further, assume that the ink discharge amount discharged from the nozzles 108a, 108b, 108c should be adjusted to 40 pl.

The widths of the preheat pulse and the heat pulse can be adjusted to adjust the amount of ink discharged from the nozzles 108a, 108b, 108c by the same amount. Various combinations of widths of preheat pulses and heat pulses are conceivable. In this embodiment, by adjusting the width of the preheat pulses, the amounts of energy generated by the heater pulses are equalized for the three nozzles, and the ink emissions are adjusted.

Since the heaters 102a and 102b for the nozzles 108a and 108b have the same resistance, that is, 200 Ω, they are generated by the heat pulses by applying voltage pulses having the same width to the heaters 102a and 102b. You can equalize the amounts of energy you get. In this embodiment, the width of each voltage pulse is set to be t3 longer than the above-described width t5. However, different amounts of ink, 36 pl and 40 pl, are ejected from the nozzles 108a, 108b upon application of the same energy. In order to increase the amount of ink discharged from the nozzle 108a, a preheat pulse having a width t2 longer than the width t1 of the preheat pulse applied to the heater 102b is applied to the heater 102a. By this operation, the ink discharges discharged from the nozzles 108a and 108b can be adjusted to 40 pl.

The heater 102c for the nozzle 108c has a resistance of 210 Ω which is greater than the resistance of the other two heaters 102a and 102b. For this reason, in order for the heater 102c to generate the same amount of energy as the energy generated by the other two heaters, the width of the heat pulse must be set to a value longer than the width of the heat pulse. Therefore, in this embodiment, the width of the heat pulse is set to be t4 longer than the width t3. Since the ink emissions emitted from the nozzles 108b and 108c upon application of the same amount of energy are the same, the width of the required preheat is the same as that applied to the heater 102b. That is, a preheat pulse having a width t1 is applied to the heater 102c.

As described above, the same amount of ink can be discharged from the nozzles 108a, 108b, 108c which discharge different amounts of inks upon application of predetermined energy to corresponding heaters having different resistances. It is also possible to intentionally make the ink emissions different. The preheat pulse is used to reduce the variation of the ink discharge discharged from each nozzle.

The following describes two representative methods for reducing inequality in printing by an inkjet printhead.

9 to 11 show a method (hereinafter referred to as bit correction) for correcting a difference between ink emissions emitted from a plurality of nozzles of the inkjet printhead IJH.

First, as shown in FIG. 9, ink is discharged onto a predetermined substrate P from, for example, three nozzles, nozzle 1, nozzle 2, and nozzle 3 of the inkjet printhead IJH. Then, the size of the ink dots made up of the ink discharged from the respective nozzles 1, 2, 3 is measured, and the ink discharge amount discharged from each nozzle is measured. In the measurement of ink discharge, the heat pulses (see FIG. 8) applied to the heaters of the nozzles are initially set to a fixed pulse width, and the preheat pulse widths (see FIG. 8) are changed as described above. As a result, as shown in FIG. 10, a curve indicating a relationship between the preheat pulse widths (indicated by the heating time in FIG. 10) and the ink emissionss is obtained. To fix the ink discharged from each nozzle at 20 ng, it can be seen from the graph shown in FIG. 10 that the pulse width applied to nozzle 1 is 1.0 μs, 0.5 μs for nozzle 2 and 0.75 μs for nozzle 3. . Therefore, by applying the preheat pulses having the pulse widths to the heaters of the nozzles, it is possible to adjust the amount of ink discharged from each nozzle to a certain amount of 20 ng. Correcting the amount of ink discharged from each nozzle as described above is called bit correction. In this embodiment, the pulse width of the preheat pulse is changed in four stages to achieve a correction range of the ink discharge amount of about 30%. Also, the resolution of the correction is between 2% and 3%.

Next, FIGS. 12 to 14 show a method of correcting the inequality of printing in the scanning direction of the inkjet printhead by adjusting the density of dots printed by the ink ejection nozzles (ie, the number of dots printed on a unit area) (hereinafter, Shading correction).

For example, as shown in FIG. 12, based on the amount of ink discharged from nozzle 3 of the inkjet printhead, the amount of ink discharged from nozzle 1 is about 10% or less than the reference, and is discharged from nozzle 2. Assume that ink emissions are about 20% more than the baseline. In this situation, while the inkjet printhead IJH is scanning, as shown in FIG. 13, heat pulses are applied to the heater of nozzle 1 once every 9 reference clocks, and 1 to every 12 reference clocks to the heater of nozzle 2. Heat pulses are applied once, and heat pulses are applied to nozzle 3 once every 10 reference clocks. Thus, by adjusting the number of ejection operations in the scanning direction for each nozzle, the density of the ink dots in the scanning direction can be set to a uniform density, as shown in Fig. 14, thereby preventing uneven printing. have. Correcting the density of ink dots printed in the scanning direction as described above is called shading correction. In this embodiment, the correction range of the ink density by about 40% is achieved by this correction. In addition, the distance between each dot can be theoretically controlled to be infinitely short (i.e., to increase the resolution). However, doing so significantly increases the amount of data, which slows down processing. Thus, an increase in resolution of about 10% is a practical limit.

In the case where ink emission is measured using the measuring device according to the first embodiment and the printing operation is actually performed by the printing device according to the measured result, a method of changing the pulse width of the prehit pulse or the density of dots to be printed. By appropriately adjusting the amount of ink discharged by using a method of changing, the inequality in density caused by the difference in the amount of ink discharged from each nozzle can be corrected.

Second embodiment

In the first embodiment, a line sensor camera is used to read a line pattern image. In addition to line sensor cameras, CCD cameras or other area sensors may be used. Increasing the gradations of the luminance levels (in the first embodiment, 256 gradations since using an A / D converter having 8 bits) to, for example, 16 bits, can further improve the accuracy of the measurement data.

In addition, the image pattern printed on a glass substrate is not limited to a line pattern, It may be a dot pattern. In this case, printing must be performed under the same driving conditions, and the size of the window set on the printed image input into the image processing apparatus must be large enough to include all the dots.

The present invention is applicable to the modified or modified embodiments of the above-described embodiments within the spirit thereof.

Each of the above-described embodiments includes, among inkjet printers, means for generating thermal energy (e.g., an electrothermal transducer, a laser beam generator, etc.) as energy used in the execution of ink discharge, the thermal energy of which is used. By way of example, a printer causes a change in the ink state. According to this inkjet printer and printing method, a high density, high precision printing operation can be achieved.

As a representative configuration and principle of the inkjet printing method, for example, it is preferable to carry out using US Patent Nos. 4,723,129 and 4,740,796. The above method can be applied to both a so-called on-demand type and a continuous type. In particular, in the case of on-demand type, this method corresponds to a rapid response that corresponds to print information and exceeds film boiling in each of the electrothermal transducers arranged in correspondence with a sheet or liquid channels containing liquid (ink). By applying at least one drive signal that imparts a temperature rise, thermal energy is generated by the electrothermal transducer, causing film boiling on the thermal working surface of the printhead, resulting in a liquid (ink) in one-to-one correspondence with the drive signal. This is effective because bubbles can be formed in the cavities. At least one droplet is formed by ejecting the liquid (ink) through the outlet by the growth and contraction of the bubbles. When the drive signal is applied as a pulse, the growth and contraction of the bubbles are made immediately, and in particular, the discharge of the liquid (ink) with excellent response characteristics can be properly achieved.

As the pulsed drive signal, signals described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Better printing can be performed using the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise of the thermally acting surface.

The configuration of the printhead includes, in addition to the configuration combining the discharge nozzles, the liquid passages, and the electrothermal transducers as described in the above specifications (linear liquid crystal or rectangular liquid crystal liquid), the US discloses a configuration in which the thermal action portion is disposed in the bent region. Configurations using Patent Nos. 4,558,333 and 4,459,600 are also included in the present invention. In addition, the present invention discloses a Japanese Patent Laid-Open Publication No. 59-123670, which discloses a configuration using a slot common to a plurality of electrothermal transducers as the discharge portion of the electrothermal transducers, or to absorb pressure waves of thermal energy. The present invention can also be effectively applied to a structure based on Japanese Patent Laid-Open No. 59-138461 which discloses a configuration having an opening corresponding to the discharge portion.

In addition, with a full line type printhead having a length corresponding to the width of the maximum print medium that can be printed by the printer, a plurality of printheads as described in the above specification may be combined to obtain a full line length. Any configuration or configuration as a single printhead obtained by integrally forming printheads may be used.

In addition, as described in the above embodiments, when mounted to the apparatus main body, not only the replaceable chip type printhead which can be electrically connected to the apparatus main body and can receive ink from the apparatus main body, but also is integrated with the print head itself. Alternatively, a cartridge type printhead in which an ink tank is disposed may also be applied to the present invention.

The addition of recovery means for the printhead, preliminary auxiliary means, and the like, which is provided as the configuration of the printer of the present invention, is preferable because the printing operation can be further stabilized. Examples of such means include, for printheads, capping means, cleaning means, pressurization or suction means, and preheating means using an electrothermal transducer, separate heating elements, or a combination thereof. do. Providing a preliminary ejection mode to perform ejection separately from printing is also effective for stable printing.

In addition, in each of the above-described embodiments of the present invention, ink is assumed to be a liquid. In addition, the present invention may use an ink that is solidified at room temperature or lower, or an ink that is softened or liquefied at room temperature, or in the inkjet method, ink viscosity is controlled by performing temperature control of the ink itself within a range of 30 ° C to 70 ° C. It is customary to have a stable discharge range so that ink that liquefies upon application of a print signal may be used.

In addition, in order to prevent the temperature rise caused by thermal energy by actively using the temperature rise caused by the thermal energy as energy for changing the ink state from the solid state to the liquid state, it is solidified in the standing state and liquefied when heated. It is also possible to use ink. In either case, ink liquefied upon application of thermal energy in accordance with a print signal and discharged in a liquid state, or ink that starts to solidify at the time of reaching the print medium may be applied to the present invention. In this case, the ink is held in the liquid or solid state in the concave portions or through-holes of the porous sheet, as described in Japanese Patent Laid-Open No. 54-56847 or 60-71260. Can be arranged against the field. In the present invention, the film boiling method is very effective for the inks.

As described above, according to the present invention, the ink is immediately measured for each ejection operation by measuring the concentration of the line of the ink dot or line pattern formed by the ink ejected from the printhead and obtaining the ink ejection based on the measured density. Emissions can be obtained.

In addition, by calculating the density of each pixel in the line pattern and integrating the density of each pixel of the entire line pattern, even when the density of the line pattern is not uniform within the same line pattern, the accurate density of the entire line is obtained and the correct ink Emissions can be obtained.

Further, by obtaining in advance the correlation between the amount of ink discharged and the density of the ink dot formed by the discharged ink, the correlation and the measured density of the ink dot or line pattern formed by the ink discharged from any nozzle are referred to. The discharge amount of ink discharged from any nozzle can be easily obtained.

Further, ink is formed by forming ink dots or line patterns on a transparent substrate, inputting their images using a camera while irradiating the ink dots or line patterns with light, and performing image processing on the input images. The density of the dot or line pattern can be obtained immediately.

Also, by using two or more nozzles whose discharges are already known, and obtaining a calibration curve indicating the correlation between the ink discharge and the concentration of the ink dot formed by the ink discharged by the nozzles, the calibration curve and arbitrary From the density of the line of the ink dot or line pattern formed by the ink discharged from the nozzle of the ink discharge amount discharged from any nozzles under any conditions can be determined.

In addition, in order to determine the discharge amount of ink discharged from the nozzle in advance, a gravimetric method or absorbance method can be used, whereby the discharge amount of ink discharged from the nozzle can be accurately determined.

Further, by providing an XY stage or an X stage that is movable with respect to a camera that performs image processing on the ink absorbing medium, the density of lines of a plurality of ink dots or line patterns can be measured continuously. Thus, the ink emissions emitted from the plurality of nozzles of the printhead can be measured continuously.

In addition, by incorporating a device for measuring ink discharge into the printing apparatus, data on the ink discharge obtained from the measuring apparatus can be fed back to the printing apparatus so that the data can be used to control the ink discharge in a uniform amount. have.

The present invention is not limited to the above embodiments, and various variations or modifications may be made within the spirit and scope of the present invention. Therefore, the following claims are made for the public to evaluate the scope of the present invention.

Claims (28)

In the method for measuring the amount of ink discharged from the ink-jet type printhead by one discharge operation, A line pattern forming step of forming a line pattern on the predetermined member by discharging ink from the print head onto the predetermined member; A first image sensing step of sensing the line pattern by an image-sensing device; A second image sensing step of sensing, by the image sensing element, portions other than the line pattern on the predetermined member; For each pixel of the image sensing device, the luminance value of the portion detected in the second image sensing step is divided by the luminance value of the line pattern detected in the first image sensing step, and the common logarithm is calculated to calculate the common logarithm. A density calculation step of calculating a density of each pixel of the line pattern; An integration step of integrating the density of each pixel of the entire line pattern calculated in the density calculation step; And An ink discharge determination step of obtaining the ink discharge based on the integration concentration calculated in the integration step Ink emission measurement method comprising a. The method according to claim 1, further comprising a preliminary measuring step of previously measuring a correlation between the ink discharged by one discharge operation and the concentration of ink dots formed by the ink before the ink discharge determining step. Ink discharge measurement method to use. The method of claim 1, wherein the predetermined member is a transparent substrate, and in the first and second image sensing steps, light transmitted from a light source disposed behind the substrate and transmitted through the line pattern is detected. Ink discharge measurement method to use. The method according to claim 1, further comprising a discharge adjustment step of adjusting the ink discharge amount to a desired amount based on the ink discharge amount determined in the determination step after the ink discharge determination step. 5. The method of claim 4, further comprising a discharge step of discharging ink to a print medium after the discharge adjustment step. In the method for measuring the discharge amount of ink discharged from the inkjet printhead by one discharge operation, A preliminary measuring step of preliminarily measuring the ink discharge amount discharged by one discharge operation from each of the plurality of ink discharge nozzles of the print head under a predetermined condition; An ink dot formed by ink discharged from the two or more nozzles having different ink discharge nozzles among the plurality of ink discharge nozzles on the predetermined member under the predetermined condition and discharged by the two nozzles; A first concentration measuring step of measuring the concentration of these; Based on the data indicating the density of ink dots formed by the ink discharged by the two nozzles obtained in the first density measuring step and the data indicating the ink discharge rate obtained in the preliminary measuring step for the two or more nozzles. A calibration line generation step of obtaining a calibration line representing a correlation between ink discharged by one discharge operation and the concentration of ink dots; A line pattern forming step of forming a line pattern on the predetermined member by ejecting ink on the predetermined member from any nozzle of the printhead under any condition; A first image sensing step of sensing the line pattern by an image sensing element; A second image sensing step of sensing, by the image sensing element, portions other than the line pattern on the predetermined member; For each pixel of the image sensing device, the luminance value of the portion detected in the second image sensing step is divided by the luminance value of the line pattern detected in the first image sensing step, and the common number is calculated to calculate the common number. A density calculation step of calculating the density of the pixel; An integration step of integrating the density of each pixel of the entire line pattern calculated in the density calculation step; And An ink discharge determination step of obtaining an ink discharge discharged from the arbitrary nozzles under the arbitrary conditions based on the integration concentration calculated in the integration step and the calibration curve; Ink emission measurement method comprising a. The method of claim 6, wherein, in the preliminary measuring step, ink discharged from each of the plurality of ink discharge nozzles is measured by a weighing method or an absorbance method. . The method of claim 6, wherein the predetermined member is a transparent substrate, and in the first and second image sensing steps, light transmitted from a light source disposed behind the substrate and transmitted through the line pattern is detected. Ink discharge measurement method to use. 7. The method of claim 6, further comprising, after the ink discharge determining step, an emission adjusting step of adjusting the ink discharge to a desired amount based on the ink discharge determined in the determining step. 10. The method of claim 9, further comprising a discharge step of discharging ink to a print medium after the discharge adjustment step. An apparatus for measuring the amount of ink discharged from an inkjet printhead by one discharge operation, A receiving medium for receiving ink discharged from the printhead; An image sensing element for sensing a line pattern formed on the accommodation medium by the discharged ink and portions other than the line pattern; A first value for dividing the luminance value of the portion other than the line pattern sensed by the image sensing element by the luminance value of the line pattern for each pixel and calculating the common number to calculate the density of each pixel and to integrate the obtained density Calculation means; Memory means for storing a calibration curve indicating a correlation between ink discharge and a concentration of ink dots formed on the receiving medium by the discharged ink; And Second calculation means for calculating the ink discharge amount based on the integration concentration of the line pattern obtained by the first calculation means and the calibration curve; Ink emission measuring apparatus comprising a. 12. The apparatus according to claim 11, wherein the accommodation medium is a transparent substrate, and the device further comprises a light source for irradiating light onto the line pattern from behind the accommodation medium. 12. The method of claim 11, wherein the receiving medium is moved relative to the image sensing element, continuously and automatically measuring an integrated concentration of a plurality of line patterns formed on the receiving medium, and forming the plurality of line patterns. And an XY stage for continuously obtaining each ink discharge rate. 12. The apparatus as claimed in claim 11, further comprising adjusting means for adjusting the amount of ink discharged from the printhead based on the amount of ink discharged by the second calculating step. A printing apparatus having a function of measuring the discharge amount of ink discharged from an inkjet printhead by one discharge operation, and performing printing by using an inkjet printhead which discharges ink by an inkjet method, A receiving medium for receiving ink discharged from the printhead; An image sensing element for sensing a line pattern formed on the accommodation medium by the discharged ink and portions other than the line pattern; Dividing the luminance value of the portion other than the line pattern sensed by the image sensing element by the luminance value of the line pattern for each pixel, calculating the common number, calculating the density of each pixel, and integrating the obtained density. 1 calculation means; Memory means for storing a calibration curve indicating a correlation between ink discharge and a concentration of ink dots formed on the receiving medium by the discharged ink; And Second calculation means for calculating the ink discharge amount based on the integration concentration of the line pattern obtained by the first calculation means and the calibration curve; Printing apparatus comprising a. The printing apparatus according to claim 15, wherein the accommodation medium is a transparent substrate, and the apparatus further comprises a light source for irradiating light onto the line pattern from behind the accommodation medium. 16. The ink discharge amount of claim 15, wherein the receiving medium is moved relative to the image sensing element, continuously and automatically measuring a concentration of a plurality of line patterns formed on the receiving medium, and forming the plurality of line patterns. And an XY stage for continuously obtaining. 16. The printing apparatus according to claim 15, further comprising adjusting means for adjusting the ink discharged from the inkjet printhead based on the ink discharge calculated by the second calculating step. A method for measuring the amount of ink discharged from a printing apparatus having an inkjet printhead, A line pattern forming step of forming a line pattern on the predetermined member by discharging ink from the print head onto the predetermined member; A first image sensing step of sensing the line pattern by an image sensing element; A second image sensing step of sensing, by the image sensing element, portions other than the line pattern on the predetermined member; For each pixel of the image sensing device, the luminance value of the portion detected in the second image sensing step is divided by the luminance value of the line pattern detected in the first image sensing step, and the common number is calculated to calculate the common number. A density calculation step of calculating the density of the pixel; An integration step of integrating the density of each pixel of the entire line pattern calculated in the density calculation step; And An ink discharge determination step of obtaining the ink discharge based on the integration concentration calculated in the integration step Ink emission measurement method comprising a. 20. The method according to claim 19, further comprising a preliminary measuring step of preliminarily obtaining a correlation between the ink discharged by one discharge operation and the concentration of ink dots formed by the ink before the ink discharge determining step. Ink emission measurement method The method of claim 19, wherein the predetermined member is a transparent substrate, and in the first and second image sensing steps, light transmitted from a light source disposed behind the substrate and transmitted through the line pattern is detected. Ink discharge measurement method to use. 20. The method according to claim 19, further comprising, after the ink discharge determining step, an emission adjusting step of adjusting the ink discharge to a desired amount based on the ink discharge determined in the determining step. 23. The method of claim 22, further comprising a discharging step of discharging ink to a print medium after the discharging adjustment step. A method for measuring the amount of ink discharged from a printing apparatus having an inkjet printhead, A preliminary measuring step of preliminarily measuring the ink discharge amount discharged by one discharge operation from each of the plurality of ink discharge nozzles of the print head under a predetermined condition; An ink dot formed by ink discharged from the two or more nozzles having different ink discharge nozzles among the plurality of ink discharge nozzles on the predetermined member under the predetermined condition and discharged by the two nozzles; A first concentration measuring step of measuring the concentration of these; Data representing the density of the ink dots formed by the ink discharged by the two nozzles obtained in the first density measuring step and data representing the ink discharge rate obtained in the preliminary measuring step for the two or more nozzles. A calibration curve generating step of obtaining a calibration curve representing a correlation between the ink discharge volume discharged by one discharge operation and the concentration of the ink dot based on the basis; A line pattern forming step of forming a line pattern on the predetermined member by ejecting ink on the predetermined member from any nozzle of the printhead under any condition; A first image sensing step of sensing the line pattern by an image sensing element; A second image sensing step of sensing, by the image sensing element, portions other than the line pattern on the predetermined member; For each pixel of the image sensing device, the luminance value of the portion detected in the second image sensing step is divided by the luminance value of the line pattern detected in the first image sensing step, and the common number is calculated to calculate the common number. A density calculation step of calculating the density of the pixel; An integration step of integrating the density of each pixel of the entire line pattern calculated in the density calculation step; And An ink discharge determination step of obtaining an ink discharge discharged from the arbitrary nozzles under the arbitrary conditions based on the integration concentration calculated in the integration step and the calibration curve; Ink emission measurement method comprising a. 25. The method of claim 24, wherein in the preliminary measuring step, ink discharged from each of the plurality of ink discharge nozzles is measured by gravimetry or absorbance. 25. The method of claim 24, wherein the predetermined member is a transparent substrate, and in the first and second image sensing steps, light transmitted from a light source disposed behind the substrate is transmitted to sense light transmitted through the line pattern. Ink discharge measurement method to use. 25. The method of claim 24, further comprising, after the ink discharge determining step, a discharge adjusting step of adjusting the ink discharge to a desired amount based on the ink discharge determined in the determining step. 28. The method of claim 27, further comprising a discharging step of discharging ink to a print medium after the discharging adjustment step.