Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1997-12-09
2001-08-07
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S019000
Reexamination Certificate
active
06270178
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for measuring the amount of ink discharged, a printing apparatus-and a method of measuring the amount of ink discharged by the printing apparatus, and more particularly, to a method and an apparatus for measuring the amount of ink discharged by single discharging operation of a printhead, such as that used in an ink-jet printer, having fine nozzles which discharge a very small amount of ink from each nozzle.
For an apparatus such as the ink-jet printer which has a printhead consisting of a plurality of fine nozzles, it is quite important to control the amount of ink discharged from each nozzle to be uniform in order to stabilize printing quality. For this purpose, it is desired to correctly and instantly obtain the amount of ink discharged from each nozzle.
There are known methods of measuring a small amount of colored ink droplet (e.g., color ink), namely, (1) a weighing method and (2) an absorbance method.
Followings are explanation when the amount of ink discharged from a nozzle of an ink-jet printer is measured in the above two methods.
(1) Weighing Method
In this method, ink is discharged at a fixed interval for a predetermined time period, and the amount (weight) of used ink in the time period is measured by a chemical balance or the like (care must be taken to minimize vaporization vaporization of ink during this operation). Thereafter, by dividing the amount of ink used by the number of discharging operation performed, an average amount of ink droplet (an average discharging amount) in each discharging operation can be obtained.
(2) Absorbance Method
This method uses the relationship between concentration of solution and light absorption, which is known as Lambert-Beer's law. More specifically, solution having a certain concentration is poured into a transparent container having a fixed depth, and light having intensity I
0
is incidented on the container from one side, then intensity I of the light transmitted through the solution in the container is measured. Since a part of the incidented light is absorbed in the solution in the container, the intensity of the light reduces while passing the solution. It is known that the intensity is lowered in proportion to the concentration of the solution. Defining A as absorbance, the relationship of this law can be expressed in the following equation:
A=−
Log(
I
0
/I
)=
a·b·c
where a is a 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 concentration and absorbance for the ink to be used is obtained in advance Next, ink is discharged from a nozzle toward a transparent solution of a known volume (a solution which has a light absorbance as small as possible is preferred), then absorbances by the solution containing discharged ink after each discharging operation, namely absorbances corresponding to the number of discharging operations, are measured. From the measured absorbances and the calibration line which was obtained in advance, the concentration of the solution including ink is determined. Then, the amount of ink mixed in the solution can be found by taking the amount of the original solution into consideration. The obtained amount of ink is divided by the number of discharging operations, thereby finding an average amount of ink discharged by each discharging operation.
However, according to the foregoing two conventional methods, there are problems in which a certain amount of ink has to be discharged; thus, it is impossible to instantly obtain the amount of ink discharged from each nozzle. As an experiment, the applicant of the present invention measured the amount of ink discharged per nozzle by the weighing method, and found that ink corresponding to 500,000 dots were discharged, and it took 12 minutes for the measurement. Thus, it takes quite a long time to measure the amount of ink discharged per nozzle of an ink-jet printer having an ink-jet printhead consisting of 64 or 128 fine nozzles. Furthermore, in the foregoing two methods, since the amount of ink per discharging operation is averaged, it is impossible to measure the real amount of ink discharged per nozzle in a single discharging operation.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to provide a method and apparatus for instantly measuring the amount of ink discharged from a nozzle.
Another object of the present invention is to provide a printing apparatus having the aforementioned measuring apparatus, and method of measuring the amount of discharged ink in the printing apparatus.
In order to solve the above-described problems and attain the objects, the method of measuring the amount of discharged ink according to the first aspect of the present invention is characterized by the following configuration.
More specifically, the method of measuring an amount of ink discharged from an ink-jet type printhead in a single discharging operation, comprises: a density measuring step of measuring a density of an ink dot formed by ink discharged from the printhead on a predetermined material; and a determining step of determining an amount of ink discharged on the basis of the density of the ink dot measured in the density measuring step.
Furthermore, the method of measuring the amount of discharged ink according to the second aspect of the present invention is characterized by the following configuration.
More specifically, the method of measuring an amount of ink discharged from an ink-jet type printhead in a single discharging operation, comprises: a preliminary measuring step of preliminarily measuring an amount of ink discharged from each of a plurality of ink-discharging nozzles of the printhead in a single discharging operation under a predetermined condition; a first density measuring step of measuring densities of ink dots made of ink discharged from at least two different ink-discharging nozzles which discharge different amounts of ink from each other out of the plurality of ink-discharging nozzles onto a predetermined material under the predetermined condition; a calibration line generating step of generating a calibration line representing correlation between an amount of ink discharged in a single discharging operation and a density of an ink dot on the basis of data on the densities of the ink dots, measured in the first density measuring step, formed with the ink discharged from the at least two ink-discharging nozzles and data on the amount of ink, measured in the preliminary measuring step, discharged from the at least two ink-discharging nozzles; a second density measuring step of measuring a density of an ink dot formed by ink discharged from an arbitrary nozzle of the printhead under an arbitrary condition; and a determining step of determining an amount of ink discharged from the arbitrary nozzle under the arbitrary condition on the basis of the data on the density of the ink dot, obtained in the second density measuring step, and the calibration line.
Furthermore, the apparatus for measuring the amount of discharged ink according to the first aspect of the present invention is characterized by the following configuration.
More specifically, the apparatus for measuring an amount of ink discharged from an ink-jet type printhead in a single discharging operation, the apparatus comprising: receiving medium for receiving ink discharged from the printhead; density determining means for determining a density of an ink dot formed by the discharged ink on the receiving medium; memory means for storing a calibration line representing correlation between an amount of ink discharged and a density of an ink dot formed by the discharged ink on the receiving medium in a single discharging operation; and operation means for finding an amount of the discharged ink on the basis of the density of the ink dot determined by the density determining means and the calibrat
Akahira Makoto
Fujiike Hiroshi
Saito Tadao
Wada Satoshi
Yamaguchi Nobuhito
Barlow John
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Stephens Juanita
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