JP2003341030A - Image recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image recorder which can measure gradation characteristics with respect to a plurality of optical densities of an object to be measured such as transmission densities/reflection densities by a simple device, and can automatically calibrate on the basis of the measured gradation data. <P>SOLUTION: One or a plurality of light illumination means A1 and A2 and one or a plurality of light receiving means B1 and B2 are combined with each other to measure, for example, the reflection density and the transmission density. In the case of the measurement by one light receiving means B1, a device configuration and a calculation method for separately extracting a reflection density component and a transmission density component are provided from optical gradation data, in which the reflection density component and the transmission density component are mixed, are provided. Optical density gradation data is calculated for each of the plurality of optical densities, based on which an auto calibration (automatic gradation correction) is carried out. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation correction function of an image recording device.

[0002]

BACKGROUND OF THE INVENTION In recent years, a method for obtaining medical radiation image information without using a radiographic film made of a silver salt photosensitive material has been devised. For example, using an imaging plate mainly composed of a stimulable phosphor, after once accumulating a radiation image, it is taken out as a stimulable luminescent light by using excitation light,
A radiation image reader (Computed Radiograph) that obtains an image signal by photoelectrically converting this light
PHY, hereinafter abbreviated as CR) has become popular. Also,
Recently, a device (FlatPanel De) for reading radiation image information by combining a radiation phosphor or radiation photoconductor with a two-dimensional semiconductor detector such as a TFT switching element.
Tector, hereinafter abbreviated as FPD) has also been proposed.
Further, a simple X-ray such as an X-ray computed tomography apparatus (X-ray CT apparatus) or a magnetic resonance image forming apparatus (MRI apparatus)
Radiation image input devices other than radiography are also popular. These medical image input devices often provide image information in the form of digital signals. In diagnosing these medical images, a method of recording image information on a transmissive recording medium and / or a reflective recording medium and observing it in the form of a hard copy is often used. As a medical image recording apparatus for recording medical image information on a recording medium, a system of recording an image by laser exposure on a transmission recording medium using a silver salt recording material is often used. According to this method, a monochrome multi-gradation image can be drawn with excellent gradation, and high diagnostic ability can be obtained by recording on a transparent medium and observing it with transmitted light.

[0003]

In recent years, the image quality of ink jet recording has been improved with the improvement of miniaturization of ink droplets and improvement of resolution, and paper, PET (Poly Ethylene Terephthal) have been improved.
ate resin: Polyethylene terephthalate resin) has become possible to obtain a certain degree of image quality even when an image is recorded on a reflective recording medium using a support as a support. For this reason, recently, the possibility of recording a medical image using an inkjet recording apparatus has been expected. In particular, for medical images, there is a desire to record a transmission image and a reflection image with one image recording device,
In the case of the inkjet technology, the recording medium and the recording material (ink) are independent of each other, and therefore, it can be applied to a transmission image and a reflection image by simply changing the recording medium, and thus the demand can be met. There is also a demand for sharing a transmission image and a reflection image on one recording medium, but if it is an ink jet technique (for example, by using the technique described in Japanese Patent Application No. 2000-228965), the transmission image Since it can be applied to a reflection image as well, it can meet the demand. In addition, with the ink jet technique, an image can be recorded without the need for laser exposure and almost without depending on the type and physical properties of the support of the recording medium. Since a medical image requires particularly strict gradation, it is preferable that the image recording apparatus has an automatic gradation correction (so-called “auto calibration”) function. This is because an image having good gradation is always obtained. However, in the conventional medical industry, particularly in image recording apparatuses related to image diagnosis, there are many so-called central processing type connection configurations in which a plurality of modalities (medical image capturing apparatuses) are connected to one image recording apparatus. In some cases, a transparent image for diagnosis is mainly recorded by an image recording apparatus of a centralized processing type connection form. Therefore, since it is sufficient to measure only the transmission density and perform only the transmission density in the auto-calibration, there is no image recording apparatus that measures different optical density characteristics of the measured object such as the transmission density and the reflection density. As described above, it is desired that not only a transmission image but also a reflection image can be recorded on the same recording medium. In that case, it is desirable to have an auto-calibration function for both transmission density and reflection density. More preferably, it is preferable that both the transmission density and the reflection density can be measured at the same time, and the size of the device and the manufacturing cost are not increased as much as possible.

The present invention has been made in view of the above technical requirements, and it measures gradation characteristics of a plurality of optical densities of an object to be measured such as transmission density / reflection density with a simple device. It is an object of the present invention to provide an image recording device that can perform the calibration based on the measured gradation data. An object of the present invention is to provide an image recording apparatus capable of providing an image having stable gradation characteristics based on any of the densities.

[0005]

The invention according to claim 1 for solving the above-mentioned problems is, for example, as shown in FIG.
An image recording apparatus 100 for recording an image on a recording medium 4 based on an image signal representing an image, measuring a plurality of different optical densities produced from the same rank of a specific gradation test pattern, An image recording apparatus comprising: an optical density measuring unit 15 for calculating optical density gradation data for each optical density; and a gradation correcting unit 19 for correcting the gradation of an output image.

In the gradation test pattern, a plurality of patches having a difference in brightness are arranged in the order of brightness (= in a gradation pattern).
The side-by-side output is applicable. Where the patch (patc
h) means a band-shaped area where a single density is set and output by the output machine. At this time, each patch corresponds to the same rank of the gradation test pattern. Even in the same rank (within the same patch), density unevenness occurs due to incomplete output accuracy, and therefore the same point is usually measured. In that case, the present invention measures a plurality of different optical densities produced from the same point of the gradation test pattern. As an embodiment of the present invention, a mode is provided in which a plurality of different optical densities produced from the same point are measured by light received at different timings. Further, there is provided a mode of measuring a plurality of optical densities produced from the gradation test pattern while recording the gradation test pattern. Different optical densities mean light densities, optical paths, light receiving elements, etc., that is, optical densities measured under different measurement conditions depending on the conditions of the light source and the light source and the light receiving element. The optical densities of light having different densities and reflection angles (75 °, 90 °, etc.), the optical densities of light having different emission spectra, and the optical densities of light receivers having different light receiving sensitivities are applicable. The present invention includes a mode in which a plurality of different optical densities produced from the same rank of the gradation test pattern are measured based on light received by different light receiving elements or the same light receiving element.

According to a second aspect of the present invention, the gradation correction means corrects the gradation of an image to be output based on the optical density gradation data. Is.

According to a third aspect of the present invention, at least one of the plurality of optical densities is a reflection density, and at least another one is a transmission density. 2 is the image recording apparatus.

The invention according to claim 4 is, for example, as shown in FIGS.
4. The optical density measuring means comprises a plurality of light transmitting / receiving pairs comprising one light emitting means and one light receiving means, as shown in FIG. This is an image recording device.

According to a fifth aspect of the present invention, for example, as shown in FIG. 3c, the optical density measuring means includes a plurality of light irradiating means and a plurality of light sources which simultaneously receive light from the one light irradiating means. The image recording apparatus according to claim 1, 2 or 3, further comprising a light receiving unit.

The invention according to claim 6 is, for example, as shown in FIGS.
As shown in FIG. 4, the optical density measuring means is a plurality of light irradiating means for irradiating different positions on the gradation test pattern, and one of the light irradiating means for simultaneously receiving light using the plurality of light irradiating means as a light source. The image recording apparatus according to claim 1, 2 or 3, further comprising a light receiving unit.

The invention according to claim 7 is, for example, as shown in FIGS.
As shown in (c), the spot widths of the first spot and the second spot, which are irradiated to different positions on the gradation test pattern by any two light irradiation means of the plurality of light irradiation means, 7. When W1 and W2, respectively, the shift length ΔX of the center positions of the first spot and the second spot satisfies the relational expression ΔX> (W1 + W2) / 2. The image recording apparatus described in 1.

The invention according to claim 8 is, for example, as shown in FIGS.
As shown in FIG. 5, the optical density measuring means is based on the amount of light received by the one light receiving means, and is based on the optical gradation data about the light using the plurality of light emitting means as the light source (referred to as “mixed optical gradation data” .) Is generated and the optical density gradation data is obtained from the mixed optical gradation data by extracting the optical gradation data for the light using only one of the plurality of light irradiation means as a light source. The image recording apparatus according to claim 6 or 7.

According to the image recording apparatus of the sixth or seventh aspect, according to the one light receiving means for simultaneously receiving the light having the plurality of light emitting means as the light sources, the plurality of light emitting means are used as the light sources. Only optical density by light can be measured. The present invention temporarily generates optical gradation data (mixed optical gradation data) for light using a plurality of light irradiation means as a light source,
From the mixed optical gradation data, the optical gradation data for the light using each one of the light irradiation means as the light source is extracted (separated and extracted) by a calculation process. When the output value of the light receiving means is acquired by the light quantity or light attenuation rate depending on the type of light receiving means,
The mixed optical gradation data may be treated as gradation data of light intensity or light attenuation rate, separated and extracted, and then converted to optical density to obtain optical density gradation data, or converted to optical density and then separated and extracted. Optical density gradation data may be obtained. That is, the processing procedure does not matter. When the output value of the light receiving means is acquired as the optical density depending on the type of the light receiving means, the optical density gradation data can be obtained by separating and extracting the mixed optical gradation data. In order to perform separation / extraction, it is necessary for a plurality of light irradiation means to irradiate different positions on the gradation test pattern with light, and in order to improve the accuracy of separation / extraction (and thus the optical density measurement accuracy), It is preferable to satisfy the requirement of 7.

The invention according to claim 9 is characterized in that, for example, as shown in FIG. 13, the gradation correction means includes gradation creation table selection means 50 for selecting a gradation creation table. The image recording apparatus according to claim 8.

The invention according to claim 10 is characterized in that the pattern recording means records the gradation test pattern on the recording medium by an ink jet system. The described image recording apparatus.

The invention according to claim 11 is the image recording apparatus according to any one of claims 1 to 10, characterized in that the image is a medical image.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments described below.

<Definition of Terms> The following terms have the following meanings. The "output" of an image is to embody the image in an output object based on an image signal representing the image, and mainly corresponds to "record" or "display" the image. Since the present invention is an invention relating to an image recording apparatus, "outputting" means "recording" an image exclusively on a recording medium. "Density" represents so-called optical density D, and DT = -log10
It is defined by T or DR = -log10R. For example, it refers to the density measured by an optical densitometer PDM-65 (manufactured by Konica Corporation). Note that T and R are light transmittance and reflectance, respectively. The former density is called the transmission density, and the latter density is called the reflection density. Since the present invention can be applied to both the transmission density and the reflection density, the density means either the transmission density or the reflection density unless otherwise specified.

The term "output density" refers to the density of an output material obtained when an image is output, and includes the density due to the recording material adhering to the recording medium and the density due to the recording medium. It refers to the density of the entire image. The “brightness” is the lightness in the CIE-LAB color system recommended by CIE1976, and is a kind of psychophysical quantity that well expresses the degree of light and shade. The image signal value S (hereinafter, also simply referred to as “signal value”) can take any value among integers in the range of 0 ≦ S ≦ Smax. Here, Smax is the maximum image signal value, and when the image signal input to the image recording apparatus is an image signal forming an N-bit gradation, Smax = 2 ^ N-1.
The “gradation characteristic” is a characteristic indicating a relationship between a signal value in an image signal and a physical quantity or a psychophysical quantity. For example,
The "density gradation characteristic" is a characteristic showing the relationship between the signal value and the density, and the "density gradation characteristic curve" is the signal value on the horizontal axis.
It is assumed that the vertical axis represents the gradation characteristic with the density. Also,
The terms "brightness gradation characteristic" and "brightness gradation characteristic curve" mean that the above definition is replaced with "brightness". Furthermore, "transmission density gradation characteristics" or "reflection density gradation characteristics"
"Transmission density" and "Reflection density" respectively
Is the gradation characteristic. The "transmissive recording medium" is a recording medium whose main purpose is to observe as a transmitted image.
The “reflection recording medium” is a recording medium whose main purpose is to observe as a reflection image.

<Overall Configuration of Image Recording Apparatus> Here, an inkjet recording apparatus will be described as a specific example of an embodiment of the image recording apparatus according to the present invention with reference to FIGS. 1 and 2. . A medical image can be recorded by this inkjet recording device, and the medical industry can be supported. In particular, according to the present invention, a common transmission / reflection medium that can be used as both a transmission medium and a reflection medium can be supplied with good gradation. FIG. 1 is a functional block diagram of an inkjet recording apparatus. FIG. 2 shows a portion 100a in FIG.
3 is a detailed block diagram of FIG. As shown in FIG. 1, the image recording apparatus 100 of this embodiment has a recording head unit 120 as a recording unit that records an image by ejecting ink. Further, the image recording apparatus 100 includes a control unit 101.
An image processing unit 110, a gradation correction unit 19 in the image processing unit 110, a recording medium conveying unit 130 using a conveying roller or the like, and a gradation test pattern image signal storage unit 1.
7 and an optical density gradation data storage means 16. The image recording apparatus 100 further includes an optical density measuring unit 15. The optical density measuring means 15 is a light irradiating means 10.
1, a light receiving unit 11, a combined light receiving amount calculation unit 12, an optical density calculation unit 13, and a separation extraction unit 18. See also FIG.
As shown in FIG. 3, the image recording apparatus 100 has a recording head transport unit 140.

The control means 101 controls each part of the image recording apparatus 100. Further, the control unit 101, as the control characteristic of the present embodiment, is a gradation correction for correcting the gradation characteristics of the image recording apparatus 100, the recording medium 4, or the recorded image so as to be optimized for each observation environment. It also controls the unit 19.

The image processing means 110 receives an image signal from an external medical imaging device or storage device and also executes necessary image processing. The gradation correction unit 19 of the image processing unit 110 optimizes the gradation characteristics of the image recording apparatus 100, the recording medium 4, or the recorded image for each observation environment as the image processing that is a feature of this embodiment. The gradation correction process is performed to correct.

The image signal input from the outside may be via various networks. The image signal processed by the image processing means 110 is sent to the control means 101.

As shown in FIG. 2, the recording head unit 12
0 has four types of black ink K1 with different densities.
The K4 recording heads 120a to 120d are provided in a line, and a recording head control signal according to an image signal is supplied from the control unit 101. These recording heads 12
0a to 120d may be integrated or may be individually provided. As described above, by forming an image using four types of black inks having different densities, it is possible to obtain higher image quality as an image for medical diagnosis or reference.
It is possible to obtain a multi-tone image. In order to create a medical image requiring multi-gradation, it is desirable to use at least 3 to 4 types of black ink having different densities.
The "black inks having different densities" are inks that use black dyes or pigments and have different dye (pigment) concentration ratios. For example, four types of inks, K1, K2,
When four kinds of substantially uniform density images are recorded on a recording medium using only one ink of K3 and K4, the optical densities of the recorded images are different. Further, in order to eliminate the streak unevenness peculiar to the image recording apparatus, it is necessary to uniformly eject the ink from the recording head onto the recording surface, and as a result, the ink image receiving layer is thickened as the ink absorption amount increases. There must be. When the ink image receiving layer is thick, the surface of the recording surface is apt to be scratched, and the recording medium must be handled more carefully.

The ink ejecting mechanism of the ink jet head 120 may be a system using the piezo effect or a system using the force of bubble formation that occurs when the ink is instantly heated. About 64 to 512 nozzle holes are suitable as a medical inkjet. The flight speed of ink drops is 2
~ 20 m / s is preferable, and the amount of ink ejected from one drop is 1 to 5
0 picoliter is preferred. The recording medium conveying means 130 conveys the recording medium 4 in the main scanning direction. The print head carrying unit 140 carries the print head in the sub-scanning direction. Here, the recording medium carrying means 130 carries the recording medium 4 in the direction of arrow A based on the recording medium carrying signal. The recording head transport unit 140 moves the recording head unit 120 in a direction B orthogonal to the transport direction A of the recording medium 4. While the recording head conveying means 140 moves the recording head unit 120 in the direction of arrow B based on the head conveying signal, each recording head 120a to 120d ejects ink onto the recording medium 4 based on the recording head control signal to form an image. Form.

<Optical Density Measurement> Next, the processing contents of the optical density measuring means 15 will be described.

<Acquisition of Profile> FIG. 3 shows five structural examples of the light irradiation means and the light receiving means. While recording the image on the recording medium while conveying the recording medium, the recording head 12
Since the output density relating to the image on the recording medium moving to the lower side of 0 is measured at the time of image recording, the profile can be obtained by fixing the position of the light irradiation means or the light receiving means and reading the density in time series. it can. Light irradiation means L
A light source such as an ED or a lamp can be used. As the light receiving means, a light receiving device such as a photodiode or a photomultiplier tube (PMT) can be used. The profile may be acquired as a density profile or a light attenuation rate profile. When the current value is proportional to the amount of light, it can be obtained as a density value via a log amplifier (not shown).

FIG. 3A shows a case where two light sources are provided and two light receivers are provided. This is a configuration example in which a light source A1 and a light receiver B1 for measuring reflection density in an image, and a light source A2 and a light receiver B2 for measuring transmission density in an image are paired. In this configuration example,
The light received by the light receiver B1 is preferably only the light originating from the light source A1, and the light originating from other light sources (eg, the light source A2, external light, etc.) is noise. , Only the light from the light source A1 is the light receiver B
It is preferable to configure so as to reach 1. Receiver B
The same applies to 2.

The positional relationship between the light source and the light receiver does not matter.
For example, as shown in FIG. 3B, the light receivers B1 and B2 can be arranged on opposite sides of the recording medium 4. With this arrangement, it becomes difficult to receive light originating from each other's light sources.

The configuration example shown in FIG. 3 (c) is a case where one light irradiation means A1 has two light receiving means B1 and B2. The light emitted from the light source A1 is reflected or transmitted, but the reflected component is received by the light receiver B1 and the transmitted component is received by the light receiver B2.

The configuration example shown in FIG. 3D is a case where one light receiving means B1 is provided for two light irradiating means A1 and A2. The configuration example shown in FIG. 3E is a configuration example in which one light receiving unit B1 is provided for two light irradiation units A1 and A2, and the transmission density and the reflection density are measured.
In the configuration example shown in FIGS. 3D and 3E, signals originating from both light sources that simultaneously receive light are mixed, but the signals can be separated and extracted as described below.

In any of the configuration examples shown in FIG. 3, when viewed in a plane perpendicular to the recording medium, the light irradiation means (light sources) A1 and A2 and the light receiving means (light receivers) B1 and B2 are
It need not be on a straight line in the recording medium conveyance direction. For example, in FIGS. 3A, 3B, and 3D, the light source A1 and the light source A2 are arranged at different positions in the direction perpendicular to the recording medium conveyance direction and parallel to the recording medium (referred to as the “scanning direction of the recording unit”). good. In FIGS. 3A, 3B and 3C, the light receiver B1 and the light receiver B2 may be arranged at different positions in the scanning direction of the recording section. 3A to 3E, the light source A1 and the light receiver B1 may be arranged at different positions in the scanning direction of the recording section. Figure 3
In (a) and (b), the light source A2 and the light receiver B2 may be arranged at different positions in the recording section scanning direction. In FIG. 3C, the light source A1 and the light receiver B are placed at different positions in the recording section scanning direction.
Two may be arranged. In FIGS. 3D and 3E, the light source A2 and the light receiver B1 may be arranged at different positions in the recording section scanning direction. Also, when viewed in a plane perpendicular to the recording medium,
Light emitting means (light sources) A1 and A2 and light receiving means (light receiver)
Even when B1 and B2 are on a straight line in the recording medium conveyance direction, the order of arrangement of the light source and the light receiver does not matter, for example, the light source A1, the light source A2, and the light receiver B along the recording medium conveyance direction.
The order may be 2, the light receiver B1. In short, it may be arranged so that the light receiver can receive the light to be received. Therefore, since there is a degree of freedom in arrangement, it is possible to flexibly deal with other design restrictions.

<Position relation of spots> In order to perform separation / extraction, it is necessary for a plurality of light irradiation means to irradiate different positions on the gradation test pattern with light, and the accuracy of separation / extraction (and thus optical density measurement). In order to improve (accuracy), it is preferable to satisfy the following spot positional relationship. Figure 4 (a)
Is a configuration example of a combination of transmission density / reflection density, (b)
Is an example of the configuration of a combination of reflection densities at different reflection angles. FIG. 4C is an example of a spot positional relationship (good example), and FIG. 4D is an example of a spot positional relationship (bad example).

When the spot widths of the first spot and the second spot which are irradiated to different positions on the gradation test pattern by any two light irradiation means of the plurality of light irradiation means are W1 and W2, respectively. The displacement length ΔX of the center positions of the first spot and the second spot preferably satisfies the relational expression ΔX> (W1 + W2) / 2. In this way, the light emitted from the respective light irradiating means does not mix near the image surface, so that the density measurement accuracy is improved. Here, the spot width is defined as the diameter of a substantially circular range where the intensity is 1 / e2 or more when the intensity at the spot center is 1 in the light intensity distribution when light is irradiated on the entire surface of the recording medium. To do.

Further, when the gradation test pattern has density patches of substantially the same size, the width of the density patch in the density scanning direction is A, and the number of the light irradiating means is n, each spot is A. It is preferable that they are arranged at an interval of / n. This is because the steps of the obtained density profile are arranged at equal intervals, which facilitates edge detection.

<Averaging Processing> Next, the average received light amount calculation unit 1
The averaging process in 2 will be described. FIG. 5 is a gradation test pattern diagram (a) and a corresponding profile diagram (b) for explaining the averaging process in the average received light amount calculation unit 12. The optical density of each patch, that is, the optical density gradation data is obtained based on the received light intensity profile or density profile acquired in the previous stage, but due to factors such as uneven recording, variations in light source / light reception, and electrical noise in the circuit, As shown in FIG. 5B, the profile varies. Therefore, a method of detecting a substantially uniform density range in each patch and obtaining an average value in the range can be considered. The average received light amount calculation unit 12 is achieved by either hardware or software. First, the edges of the profile are detected. For example, since the portion where the gradient of the profile sharply increases is an edge, the edge can be easily detected by using the threshold method. A substantially uniform density range can be recognized based on the detected positions of the edges, and the average value in that range can be used as the average density of the patch. At that time, rather than strictly determining the average concentration using a large number of data, a random (or at a predetermined timing) number data within the range is extracted,
You may ask for the average. Although the population is small and the measurement accuracy is slightly lowered, it is actually confirmed that the statistical variation has almost no effect if the number of samples is 10 or more. In this way, the optical density of each patch included in the gradation test pattern, that is, the optical density gradation data can be obtained.

<Averaging Process of Mixed Profile> FIG. 6
4D is an example of the configuration shown in FIGS. 4A and 4C (where the spot position is 1 /
It is a figure of the profile obtained in the case of 2 patch shift. FIG. 6A shows a gradation test pattern to be measured. The gradation test pattern is recorded on the recording medium based on the image signal stored by the gradation test pattern storage means 17 or transferred from the outside. Main scanning direction A
The patches having different recording densities form gradations, and each patch extends in the sub-scanning direction. The gradation test pattern image signals form a two-dimensional array of image signals in which the same signal values are localized so that the recorded images have substantially the same density in a predetermined area. In FIG. 6A, there are seven patches (P0 to P6) having different densities. The patch P0 is a non-printed part.

FIG. 6B shows the profile of the transmitted light amount It, and FIG. 6C shows the profile of the reflected light amount Ir. Figure 4 (a) (c)
In the configuration example shown in (1), neither It's profile nor Ir's profile is obtained, and Itotal's profile in which It and Ir are mixed is obtained (FIG. 6D). This is averaged as described above. Since the profile of Itotal has a step shape, the average concentration can be easily calculated as described above. That is, the portion where the gradient of the light amount profile sharply increases is recognized as an edge.
Take the average value in the plateau part. As a method for detecting the edge part, the threshold method is used to detect the point where the gradient (proximity data) becomes steep, and the sampling interval and plateau width are known. The concentration can be determined. The profile of Itotal is 2 (n + 1) for (n + 1) density patches.
+1) steps (n: natural number, n = in the figure)
6). As described above, the data (A0, B0 to A0) of the average value of the light amount corresponding to each step of the Itotal profile
n, Bn) is obtained. Next, the data is separated and extracted into an It component and an Ir component.

<Separation / Extraction> Next, the separation / extraction processing in the separation / extraction unit 18 will be described. The density patch is (n +
1) In the case of It (0) + Ir (0) = A0 It (0) + Ir (1) = B0 It (1) + Ir (1) = A1 It (1) + Ir (2) = B1 It (2) ) + Ir (2) = A2 It (2) + Ir (3) = B2 (hereinafter omitted) It (n) + Ir (n) = An It (n) + Ir (0) = Bn The average transmitted light amount and the average reflected light amount of the patch can be obtained. The calculation formula for n = 6 is shown in FIG. Next, in the case of n = 6, the simultaneous equations shown in FIG. 7 (a) are solved by the matrix shown in FIGS. 7 (b) (c) to obtain It (k) and Ir (k) (however, k =
0, 1, ..., 6). By substituting this into the equation shown in FIG. 7D, the transmission density Dt (k) and the reflection density Dt (k) are obtained. The transmission density Dt (k) and the reflection density Dt (k) correspond to the optical density gradation data, respectively. Optical density measuring means 15
Outputs the transmission density Dt (k) and the reflection density Dt (k) to the optical density storage means 16. The optical density storage means 16 stores it.

In addition, as the above application, it is possible to provide m light receivers for n light sources and obtain a plurality of types of optical densities. For example, transmission / reflection densities, reflection angles (75 °, 90 °, etc.), combinations of light sources having different emission spectra, combinations of light receivers having different light receiving sensitivities, and the like are conceivable, but not limited thereto. Taking into consideration the light receiving characteristics of light adaptation defined by CIE, light is emitted in the spectrum of A light source, C light source, D65 light source, etc., which are standard light sources defined by JIS,
The corrected optical density may be obtained.

<Gradation Correction (Calibration)> Next, the gradation correction processing in the gradation correction unit 19 will be described. In the present embodiment, the gradation correction unit 19 refers to the optical density gradation data calculated by the optical density measuring unit 15 and sets the conversion processing setting of the image signal (signal value conversion characteristic // Alternatively, the gradation of the output image is corrected by selecting (or image recording characteristics). Figure 8
FIG. 4 is a schematic explanatory diagram of an input / output characteristic 22 in the image recording device. The elements that determine the gradation characteristics in the image recording device correspond to the signal value conversion characteristics 20 and DDL that convert the input signal value corresponding to the image signal into a digital driving level (hereinafter referred to as “DDL”). An image recording characteristic 21 for recording a density patch and generating an output density D is roughly classified into two. The DDL is a digital value that is given as an input to the recording system that generates the output density D, and the DDL set of the recording system is
It is all possible discrete values that can produce density values on the recording system.

Since the input / output characteristic (so-called γ-LUT) 22 in the image recording apparatus is determined by the combination of the signal value conversion characteristic 20 and the image recording characteristic 21, at least one of the two characteristics should be changed. Γ-LUT22
Can be changed. As shown in FIG. 8, a desired γ-LUT 22 having a characteristic that the output density D is linear with respect to the image signal value is set. Signal value conversion characteristics 2
By changing 0 or the image recording characteristic 21, the density gradation characteristic of the image recording apparatus can be corrected so that the actual γ-LUT 22 substantially matches the desired γ-LUT 22.

When correcting the gradation, a desired density gradation characteristic can be obtained by fixing the image recording characteristic 21 and changing only the signal value conversion characteristic 20, for example. In addition, like the ink jet system, the image recording characteristic 21 is obtained by combining the dither matrix used for gradation formation.
When it is relatively easy to change, it is possible to obtain a desired density gradation characteristic by changing not only the signal value conversion characteristic 20 but also the image recording characteristic 21.
In particular, when changing the input / output characteristics 22 in the image recording apparatus by changing only the signal value conversion characteristics 20,
It is common to perform gradation correction using a gradation test pattern.

FIG. 9 shows an example of gradation correction. Figure 9 (a)
Is before correction, and (b) is after correction. First, the image signal is converted into DDL by the conversion characteristic 42. The optical density gradation data obtained by the optical density measuring means 15 and the DDL when each density patch is recorded are made to correspond to each other.
The -D characteristic (that is, the image recording characteristic) 42 is obtained.
The signal value-DDL characteristic 44 for obtaining the desired γ-LUT 46 can be obtained based on the gap between the measured γ-LUT 43 and the desired γ-LUT 46, and the corrected γ-LUT
The LUT 45 substantially matches the desired γ-LUT 46. For a plurality of optical densities such as transmission density Dt and reflection density Dr,
When gradation correction is performed, if desired γ-LUTs for them are set in advance, the optical density measuring means 1
The signal value-DDL characteristic can be uniquely obtained by obtaining the DDL-D characteristic from the optical density gradation data output by the signal No. 5. This allows the DDL to be shared for a plurality of optical densities. When stored as a gradation test pattern, it is preferable to store as a DDL. Furthermore, it is preferable to cover the entire range of gradation characteristics at equal intervals. The larger the number, the more rigorous the gradation correction is possible, but 8 to 3
It should be 2 points.

<Gradation Creation Table> As a method of changing the image recording characteristic 21, there is the following method of changing the gradation creation table. FIG. 10 shows an example of the gradation creation table.
When the image recording method using the dither matrix is adopted, the gradation creation table is created by previously determining the number and amount of ink drops to be ejected to each cell. In the present embodiment, the density gradation characteristic is used when performing the gradation correction, but the present invention is not limited to this, and the gradation correction may be performed based on the brightness gradation characteristic. The "cell" refers to a minimum recording area in which the image recording apparatus can control ink ejection.
As shown in FIG. 10A, for example, one square is added but corresponds to a cell, and a dither matrix is formed by a total of four cells of LU (upper left), RU (upper right), LL (lower left), and RL (lower right). Are formed. For example, one cell is one side
1 pixel when forming an image using a 2 × 2 dither matrix, which is 7.5 μm square
On the other hand, since gradation is expressed in units of 35 μm on each side, the resolution of this image recording apparatus is 720 dpi (d
pi = dot per inch; 1 inch = 25.4 mm). Figure 1
The gradation table of 0 (b) (c) is LU (upper left), RU
The details of the ink ejected to each cell (upper right), LL (lower left), and RL (lower right) are shown. In the figure, ◯ represents one ink droplet, and the difference in filling in ◯ corresponds to the color depth. In this embodiment, since four types of ink having different densities are used, ink droplets ◯ having four types of densities are described on the gradation table. When two ink droplets are ejected to the same cell, for example, in LU of DDL = 15 in FIG. 10C, dark ink is ejected first, and then thin ink is ejected at substantially the same position. means. It is also possible to create a gradation table that includes a case in which a thin ink is first ejected and then dark ink is ejected at substantially the same position in an overlapping manner.
By changing the ejection order of the dark and light inks, it is possible to control the reflection density while keeping the transparent density constant.
Specifically, when ejecting inks having different densities to the same cell, the reflection densities can be suppressed lower than the transmission densities by landing the inks on the recording medium in a slower order (for example, last) as the inks get thinner. it can. Further, the reflection density can be controlled without affecting the transmission density so much by changing the dye density ratio in the similar color inks having different densities or using a combination of different kinds of dyes or pigments.

FIG. 11 is a gradation characteristic diagram for explaining the case of correcting the gradation for both the transmission density and the reflection density. When observing an image as a transmission image, the gradation correction may be performed by paying attention to only the transmission density, and when observing the image as a reflection image, the gradation correction may be performed by focusing only on the reflection density. However, in the case of common use, it is necessary to perform correction so that the gradation characteristics of both approaches the desired gradation characteristics. It is also possible to prepare a plurality of tables in which the output densities match one optical density, and select a table in which other focused densities are closest to the ideal gradation characteristics. For example, the gradation characteristic of transmission density obtained by using the gradation creation table of FIG. 10 (b) is shown in FIG. 11 (d-1), and the gradation characteristic of reflection density is shown in FIG. 11 (e-1). On the other hand, FIG.
The gradation characteristics of transmission density obtained using the gradation creation table of (c) are shown in FIG. 11 (d-2), and the gradation characteristics of reflection density are shown in FIG.
It is (e-2). In this case, gradation characteristics can be comprehensively improved by selecting the gradation creation table of FIG.

By simultaneously obtaining the transmission density and the reflection density, it is possible to infer the characteristics of the image recording medium. In the transmission / reflection common medium, a plurality of gradation tables are prepared, and a table is selected in which the transmission density gradation characteristics and the reflection density gradation characteristics are totally optimum. Although it is possible to measure the transmission image and the reflection image alone, this embodiment is particularly effective for a transmission / reflection shared medium.

FIG. 12 shows an example of recording a gradation test pattern. As shown in FIG. 12, each gradation test pattern is recorded on one recording medium 4 using two different gradation generation tables.
To record. FIG. 12A shows a first mode in which a gradation test pattern is recorded using two different gradation creation tables. Since the gradation test patterns exist in parallel positions, two density measuring means are required, but the measuring time is short. FIG. 12B shows a first mode in which a gradation test pattern is recorded using two different gradation creation tables. Since the gradation test pattern exists in the serial position,
One concentration measuring means is sufficient, but the measuring time is long. Also,
By recording the gradation test pattern recorded by a plurality of gradation generation tables on one recording medium, it can be used as a judgment for visually selecting the gradation generation table having the most preferable gradation.

FIG. 13 is a block diagram relating to selection of a gradation creation table by the gradation correction unit 19. A method of reading the density and automatically selecting the optimum gradation creation table will be described. As shown in FIG. 13, a gradation test pattern is output to the recording medium using three different gradation creation tables,
Optical density gradation data 1, 2, and 3 are obtained for each of the transmission density and the reflection density, and the density gradation characteristics are compared. For example, a value is input to the gradation creation table selection means 50 by weighting which of transmission density and reflection density should be prioritized. The gradation creation table selection means 50 selects the gradation creation table that has created the gradation characteristic showing the highest value among the input values.

As a method of identifying the type of recording medium,
An identification mark may be attached to a part of the recording medium in advance, and a unit for reading the identification mark may be provided. The identification mark may be optical or shape. Further, the type of recording medium may be input, or the image forming table may be selected based on the input information. It is preferable that the input means has a recording medium identification means. A form such as automatic recognition of bar code or the like, manual recognition of input or the like is conceivable, but not limited to this. Alternatively, a method of identifying the type of recording medium using a densitometer can also be applied.

<Description of Recording Medium> The recording medium of the present embodiment is characterized in that a substantially monochrome image is drawn with the liquid ink. Practically made into a sheet with an area of 15 x 10 cm or more, with square-shaped notches,
It is preferable that the recording medium has at least one void-type ink absorbing layer on at least one surface and is made of a colorless or blue-colored resin having a thickness of 75 to 250 μm. Further, if the thickness is less than 75 μm, the sheet hangs down and is difficult to handle. On the contrary, if the thickness is more than 250 μm, there is a drawback that the weight becomes considerable when carrying the sheets one after another.

Since the conventionally used X-ray film is colorless and transparent or colored blue, the recording medium of the present embodiment has a support made of a resin colored colorless or blue so that the user does not feel uncomfortable. It is preferably used. In addition, the recording medium of the present embodiment has at least one void-type ink absorbing layer on at least one side, and the surface having no ink absorbing layer is such that the films do not pass each other when the printer is machine-transported or stacked. It is a preferred embodiment to have a layer on which a mat processing is applied to prevent sticking.

The recording medium of the present embodiment can be obtained by increasing the porosity of the ink absorbing layer as much as possible, and by matting the surface or the like to produce irregularities.
Further, a white metal oxide such as titanium oxide or lead oxide can be added to the ink absorbing layer or a layer thereunder. It is also possible to provide a layer on the side opposite to the side having the ink absorbing layer of the support and disperse a metal oxide such as titanium oxide or lead oxide therein, or to provide the ink absorbing layer on both sides of the support. .

As the material of the support of the recording medium of the present embodiment, polyesters such as polyethylene terephthalate, cellulose esters such as nitrocellulose and cellulose acetate, polysulfone, polyimide,
Polycarbonate or the like can be used. Further, it is preferable that this sheet recording medium is colored blue. This blue coloring is for preventing the eyes from being dazzled by excessive transmitted light from the non-image portion as described above, and also has an effect of making a black image look more preferable. Therefore, since the ink absorbing layer is provided on at least one surface of the sheet-like support, the recording medium support is subjected to corona discharge treatment, flame treatment, ultraviolet irradiation treatment, etc. to improve the adhesiveness of the ink absorbing layer. Need to be kept.

The ink absorbing layer is preferably a layer having a three-dimensional network structure having a porosity of 40 to 90%. This three-dimensional network structure is formed from silica fine particles or organic fine particles having an average particle diameter of 20 nm or less and a water-soluble resin,
In addition, the mass ratio of the silica fine particles or organic fine particles to the water-soluble resin is preferably in the range of 1.2: 1 to 12.1. In this case, the pores forming the voids of the three-dimensional network structure have an average diameter of 5 to 40 nm, and the pores forming the voids have a pore volume of 0.3 to 1 ml / g. Silica particles are inorganic silicic acid, and have ^{2 to} 3 silalol groups per 1 nm ^{2 of} their surface, and a three-dimensional network structure is formed by connecting secondary particles having a particle size of 10 to 100 nm in which silica fine particles are aggregated. It preferably comprises a chain.

As the fine particles, colloidal silica, calcium silicate, zeolite, kaolinite, halosite, muscovite, talc, calcium carbonate, calcium sulfate, aluminum oxide and the like can be used. Polyvinyl alcohol is preferable as the water-soluble resin, but examples of other water-soluble resins include gelatin and others disclosed in JP-A-7-276789. The ink absorption layer is 50-500 m ² /
It preferably has a specific surface area of g. Also, in order to prevent sheets from sticking to each other when stacking sheets,
It is preferable to disperse matte particles having an average particle diameter of 5 to 100 μm on the surface. A surfactant may be added as an antistatic agent. On the surface without ink absorption layer,
Gelatin or a water-soluble resin can be applied to prevent curling. In addition, antistatic processing, mat processing for preventing sticking, coloring with blue, and metal oxide particles such as titanium oxide particles and zinc oxide particles can be added to this layer.

When reading a transmitted X-ray image, many films are often handled in a short time. At this time, since the front and back of the image can be seen at a glance, it is preferable that the front and back can be easily identified by making a notch in the right shoulder of the sheet, for example.

<Explanation of Ink> In this embodiment, an image can be formed by ejecting a plurality of inks having different color tones by using an ink jet head which is a means for ejecting a plurality of inks independently. . Further, an image can be formed by ejecting a plurality of single color inks having different densities by using an inkjet head which is a means for ejecting a plurality of inks independently. That is, these inks may be used individually or in combination, and different ink jet heads may be used for each single-color ink having a plurality of levels of density, for example, two levels, three levels, and four levels. For example, in the case of monochrome image formation, K1, K2, K3, and K4 inks can be used. If a color image is to be formed, the inkjet head is used for each ink of yellow (Y), magenta (M), cyan (C) and black (K).

As the color material of the ink dissolved or dispersed in water, any of pigments, water-soluble dyes and disperse dyes may be used. As the pigment, conventionally known organic and inorganic pigments can be used. For example, many azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthaloni pigments. Examples thereof include cyclic pigments, dye lakes such as basic dye type lakes and acid dye type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black and daylight fluorescent pigments, and inorganic pigments such as carbon black.

As the method for dispersing the pigment, various types such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill and a paint shaker can be used. It is also possible to add a dispersant when dispersing the pigment. Examples of the dispersant include anionic surfactants, nonionic surfactants, and polymer dispersants.

As the ink used in this embodiment, a black ink can be prepared by selecting an appropriate pigment, combining known dyes, or using a single type of dye.
Examples of water-soluble dyes include acid dyes and basic dyes reactive dyes. As the black dye, CI (color index) direct black 9, 17, 19, 2
2, 32, 51, 56, 62, 69, 77, 80, 9
1, 94, 97, 108, 112, 113, 114, 1
17, 118, 121, 122, 125, 132, 14
6, 154, 166, 168, 173, 199 and the like.

As the ink used in this embodiment, a black ink can be prepared by selecting an appropriate pigment, using a known combination of dyes, or a single type of dye. For example, carbon black is used as a pigment, and ethylene glycol, a surfactant, an antiseptic agent, or the like is mixed to obtain a black ink that is water-soluble at room temperature. When using a dye Direct Black 19 (DirectBlack1
9), Direct Black 159, Saha Black 1
(Surfer Black 1), Acid Black 2
A water-soluble black ink that is liquid at room temperature can be obtained by preparing a solution in which ethylene glycol, glycerin, a surfactant, a preservative and the like are added to (Acid Black 2) or CI Food Black 2 or the like. The direct black 19 (blue ink) is used for adjusting the color tone by mixing an appropriate amount.

It is preferable as an image forming method that a combination of inks having different densities and color tones is used to cover a wide density area while subtly changing the color tones according to changes in the density of the image. When using inks with different color tones, Acid Blue 9 (Acid
Blue9), Acid Red 52 (Acid Red)
52) and 94, Acid Yellow 23 (Acid Ye)
low23), Direct Yellow 86 (Direc)
In addition, it is a preferable embodiment that the ink disclosed in JP-A No. 2000-129182 is used.

Examples of the water-soluble organic solvent used in the ink include alcohols (eg, methanol, ethanol,
Propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc., polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol) , Dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether,
Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monomethyl ether Ethyl ether, triethylene glycol monobutyl ether,
Ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, Triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine,
Tetramethylpropylenediamine, etc., amides (eg, formamide, N, N-dimethylformamide,
N, N-dimethylacetamide, etc.), heterocycles (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-
Examples thereof include dimethyl-2-imidazolidinone), sulfoxides (eg dimethyl sulfoxide etc.), sulfones (eg sulfolane etc.), urea, acetonitrile, acetone and the like.

If desired, a surfactant may be added to the ink. Surfactants preferably used in the ink include anionic surfactants such as dialkyl sulfosuccinates, alkylnaphthalene sulfonates and fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycol. , Nonionic surfactants such as polyoxyethylene / polyoxypropylene block copolymers,
Examples include cationic surfactants such as alkylamine salts and quaternary ammonium salts. In addition to these, an antiseptic agent, an antifungal agent, a pH adjusting agent, a viscosity adjusting agent and the like can be added to the ink as required.

In the above embodiment, the ink jet recording method was used as the recording means, but the present invention is not limited to this, and impact recording such as a wet / dry silver salt laser recording method, a thermal transfer recording method and a wire dot recording method. method,
Alternatively, a recording method that can express other gradations can be applied. Further, it is not necessary to limit to the serial recording method, and a so-called line recording method may be used. Further, in order to operate various devices that realize the functions of the above-described embodiments, a program code of software for realizing the functions of the above-described embodiments is supplied to a computer in an apparatus or system connected to the various devices. The present invention also includes what is supplied and operated by operating the above various devices according to a program stored in the computer (CPU or MPU) of the system or apparatus. Further, in this case, the program code itself of the software realizes the function of the above-described embodiment, and the program code itself and a means for supplying the program code to the computer,
For example, a storage medium storing the program code constitutes the present invention. Examples of storage media that store such program codes include flexible disks, hard disks, optical disks, magneto-optical disks, and CD-RO.
M, magnetic tape, non-volatile memory, ROM, etc. can be used. Moreover, not only when the functions of the above-described embodiments are realized by executing the supplied program code by the computer, but also the OS (operating system) or other application software in which the program code is operating in the computer. Needless to say, the program code is also included in the present invention when the functions of the above-described embodiments are realized in cooperation with. Further, after the supplied program code is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the CPU provided in the function expansion board or the function expansion unit based on the instruction of the program code. It is needless to say that the present invention also includes a case in which the above processes perform a part or all of the actual processing and the functions of the above-described embodiments are realized by the processing. Medical image capturing apparatuses include simple X-ray image capturing apparatuses such as CR and FPD, X-ray computed tomography apparatuses (X-ray CT apparatuses), magnetic resonance image forming apparatuses (MRI apparatuses), ultrasonic image capturing / diagnosing apparatuses, and electronic devices. Examples include, but are not limited to, endoscopes and fundus cameras. In particular, the present invention is effective because the effect of gradation correction is remarkable in an image requiring a very high image quality, which is a medical image for monochrome multi-gradation obtained by a simple X-ray imaging apparatus. In addition, in each of the above-described embodiments, an example in which a medical image recording device is mainly used has been described, but the present invention is not limited to the use of the image recording device and is applicable to a wide field of using a digital printer. It is possible. Further, the present invention can be applied not only to a monochrome image but also to a color image in which primary colors of YMCK or RGB are combined.

[0068]

According to the first aspect of the invention, it is possible to measure the gradation characteristics for a plurality of optical densities, and to perform calibration (tone correction) for a plurality of optical densities.
There is an effect that is possible. According to the second aspect of the invention, there is an effect that auto-calibration (automatic gradation correction) can be performed for a plurality of optical densities. According to the invention described in claim 3, there is an effect that it is possible to perform gradation correction of a recording medium in which a transmission image and a reflection image are shared. According to the invention described in claim 4, there is an effect that one optical density is measured by one light transmitting / receiving pair, and calibration (gradation correction) for a plurality of optical densities is possible. According to the invention described in claim 5, there is an effect that the structure of the light irradiation means is simplified and the device can be downsized. According to the invention described in claim 6, there is an effect that the structure of the light receiving means is simplified and the device can be downsized. According to the invention described in claim 7, since the light emitted from the respective light irradiating means is not mixed near the image surface, there is an effect that the density measurement accuracy is improved. According to the invention described in claim 8, the light received by one light receiving means can be separated into the elements caused by the two light emitting means, and calibration (gradation correction) for a plurality of optical densities is possible. There is an effect that. According to the invention described in claim 9, it is possible to satisfy both the gradation characteristics for two optical densities such as transmission / reflection density, and it is possible to record an image that can withstand observation, both a transmission image and a reflection image. effective. According to the tenth aspect of the invention, there is an effect that the advantage of the inkjet recording apparatus capable of recording both transmission / reflection images can be effectively utilized. According to the invention described in claim 11, there is an effect that it is possible to meet a high demand in the medical field.

[Brief description of drawings]

FIG. 1 is a functional block diagram of an inkjet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a detailed block diagram of a portion 100a in FIG.

FIG. 3 is a schematic diagram showing five configuration examples of a light irradiation unit and a light receiving unit according to an embodiment of the present invention.

FIG. 4A is a configuration diagram of a combination of transmission density / reflection density in the embodiment of the present invention, and FIG. 4B is a configuration diagram of a combination of reflection densities at different reflection angles. (c) (d)
FIG. 6 is a plan view of an example of a spot positional relationship.

5A and 5B are a gradation test pattern diagram (a) and a corresponding profile diagram (b) for explaining the averaging process in the average received light amount calculation unit 12.

6A and 6B are diagrams showing a gradation test pattern of a measurement target, FIG. 6B is a profile of a transmitted light amount It, FIG. 6C is a profile of a reflected light amount Ir, and FIG. It and Ir
Is a mixed Itotal profile.

FIG. 7 is a formula used for a calculation example in the embodiment of the present invention.

FIG. 8 is a schematic explanatory diagram of input / output characteristics in the image recording apparatus.

FIG. 9 is a diagram showing an example of gradation correction according to an embodiment of the present invention. (a) is before correction, and (b) is after correction.

FIG. 10 is a diagram showing an example of a gradation creation table according to an embodiment of the present invention.

FIG. 11 is a gradation characteristic diagram for explaining a case where gradations of both transmission density and reflection density are corrected.

FIG. 12 is a plan view of a recording medium showing an example of recording a gradation test pattern.

FIG. 13 is a block diagram relating to gradation selection table selection of the gradation correction unit 19;

Claims (11)

[Claims] 1. An image recording apparatus for recording an image on a recording medium based on an image signal representing an image, wherein a plurality of different optical densities produced from the same rank of a specific gradation test pattern are measured, An image recording apparatus comprising: an optical density measuring unit for calculating optical density gradation data for each of the plurality of optical densities; and a gradation correcting unit for correcting the gradation of an output image. 2. The image recording apparatus according to claim 1, wherein the gradation correction unit corrects the gradation of an image to be output based on the optical density gradation data. 3. The image recording according to claim 1, wherein at least one of the plurality of optical densities is a reflection density, and at least another one is a transmission density. apparatus. 4. The optical density measuring unit according to claim 1, wherein the optical density measuring unit comprises a plurality of light transmitting / receiving pairs each including one light emitting unit and one light receiving unit. Image recording device. 5. The optical density measuring means comprises one light irradiating means and a plurality of light receiving means for simultaneously receiving light having the one light irradiating means as a light source. The image recording apparatus according to claim 2 or 3. 6. The optical density measuring means includes a plurality of light irradiating means for irradiating different positions on the gradation test pattern with light, and a light for simultaneously receiving light using the plurality of light irradiating means as a light source. The image recording apparatus according to claim 1, 2 or 3, comprising a light receiving unit. 7. The spot widths of a first spot and a second spot irradiated by different two light irradiating means of the plurality of light irradiating means to different positions on the gradation test pattern are W1 and W2, respectively. 7. When W2, the displacement length ΔX between the center positions of the first spot and the second spot satisfies the relational expression ΔX> (W1 + W2) / 2. Image recording device. 8. The optical density measuring means is based on the amount of light received by the one light receiving means, and is based on optical gradation data of light using the plurality of light emitting means as a light source (referred to as "mixed optical gradation data"). .) Is generated and the optical density gradation data is obtained from the mixed optical gradation data by extracting the optical gradation data for the light using only one of the plurality of light irradiation means as a light source. 7. The method according to claim 6,
Alternatively, the image recording apparatus according to claim 7. 9. The image recording apparatus according to claim 1, wherein the gradation correction means includes gradation creation table selection means for selecting a gradation creation table. . 10. The image recording apparatus according to claim 1, wherein the pattern recording unit records the gradation test pattern on the recording medium by an ink jet method. 11. The image recording apparatus according to claim 1, wherein the image is a medical image.