JPH09261476A - Density correcting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably form a high-quality image improving gradation reproduction by satisfactorily reproducing gradations even at a high-light density part in the case of thermosensitive recording. SOLUTION: Corresponding to the threshold value of image data corresponding to bottom recording energy for coloring thermosensitive recording materials, the conversion conditions of image data and image density are set while axially extending the input image data so that this threshold value can become bottom density data. Next, temporary density correction conditions are set while using these conversion conditions, afterwards, the density correction conditions are set by reducing the temperary density correction conditions in the axial direction of output image data so that this threshold value can become the bottom density data of output image data, and density correction is performed while these density correction conditions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of density correction in thermal recording.

[0002]

2. Description of the Related Art Image recording using a heat-sensitive recording material such as a heat-sensitive recording film (hereinafter referred to as a heat-sensitive film) having a film as a support and a heat-sensitive recording layer for recording an ultrasonic diagnostic image Thermal image recording) is also used. Further, the heat-sensitive image recording has advantages that it does not require a wet development process and is easy to handle. Therefore, in recent years, not only small-sized image recording such as ultrasonic diagnosis but also CT diagnosis and MRI are performed. In applications such as diagnosis and X-ray diagnosis that require large-sized and high-quality images, use for image recording for medical diagnosis is also under consideration.

As is well known, in thermal image recording, a thermal head having a glaze in which heat-generating elements are arranged in one direction is used for recording an image by heating a thermal recording layer of a thermal recording material. While slightly pressing the recording material (thermosensitive recording layer), while moving the both relatively in the direction orthogonal to the extending direction of the glaze, energy is applied to the heating element of the glaze to heat it according to the recorded image. By doing so, the heat-sensitive recording layer of the heat-sensitive recording material is heated to record an image.

In addition to such thermal recording, in various image recording devices such as laser printers and printing plate making devices, image data of images recorded from image data supply sources such as diagnostic measuring devices and image reading devices. (Image information) is received, and various kinds of image processing such as sharpness processing and shading correction are performed on this image data to obtain image data for image recording, and in accordance with this, image recording is performed on the recording material. . Here, the image recording apparatus is required to always output an image having a predetermined density according to the image data received from the image data supply source. For example, if the image data is 10b
In a device which receives it as digital data of it and records an image in accordance with it, when the digital data of 300 corresponds to the density (D) 1.2, when the digital data of 300 is received, It is required to output an image with a density of 1.2.

However, since there are individual differences among the image recording devices and the density of the recorded image depends on the installation environment of the device, etc., all the devices produce images of a predetermined density according to the supplied image data. It is impossible to output. Therefore, in a normal image recording apparatus, a density correction condition for outputting an image of a predetermined density according to the image data is set for each image recording apparatus, and the image data correction corresponding to this, that is, the density correction, is performed. Go and output the image.

[0006]

As a method of setting the density correction condition, various methods such as a method using an algorithm (density correction algorithm) for setting the density correction condition are known. The setting method is to change the recording energy from 0 when the light amount for recording is 0, such as in the case of image recording using a silver salt photographic light-sensitive material, so that the image density rises smoothly as the light amount increases. It is set to correspond to a system in which the image density rises smoothly.

However, in the above-mentioned thermal recording, there is a threshold (threshold value) for coloring with respect to the recording energy, that is, thermal energy, and even if the recording energy below the threshold is supplied, no color is generated, and Color develops sharply at the border of the shawls, and the rise is also rapid. Therefore, if the density correction condition is set by using the normal method of setting the density correction condition, good gradation reproducibility cannot be obtained. In particular, in the highlight density part (the brightest part) near the threshold, The value becomes high, delicate gradation cannot be reproduced, and high-quality images cannot be recorded.

An object of the present invention is to solve the above-mentioned problems of the prior art. In thermal recording, gradation can be reproduced well even in a highlight density portion, and gradation reproducibility is improved. An object of the present invention is to provide a density correction method capable of stably forming an excellent high-quality image.

[0009]

In order to achieve the above object, the present invention provides a heat-sensitive image in which a position corresponding to a recorded image on a heat-sensitive recording material is heated by a thermal head to record an image on the heat-sensitive recording material. A density correction method in recording, wherein the thermal recording material is expanded in the axial direction of the input image data so that the threshold becomes minimum density data according to the threshold of image data corresponding to the minimum recording energy for color development. The conversion condition of the image data and the image density is set, then the temporary density correction condition is set by using this conversion condition, and then the temporary density correction is performed so that the threshold becomes the minimum density data of the output image data. Provided is a density correction method characterized in that the density correction condition is set by reducing the condition in the axial direction of the output image data, and the density correction is performed based on the density correction condition.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The density correction method of the present invention will be described below in detail with reference to the preferred embodiments shown in the accompanying drawings.

FIG. 1 shows a schematic view of an example of a thermal recording apparatus for carrying out the density correction method of the present invention. The thermal recording device 10 (hereinafter referred to as the recording device 10) shown in FIG.
For example, a monochrome image is recorded by recording a heat-sensitive image on a heat-sensitive recording film (hereinafter, heat-sensitive film A) which is a cut sheet of a predetermined size such as B4 size, and the heat-sensitive film A is accommodated. Magazine 2
4 has a loading section 14, a feeding / conveying section 16, a recording section 20 for recording a thermal image on the thermal film A by the thermal head 66, and an ejection section 22.

In the recording apparatus 10 as described above, the thermal transfer film A is transferred to the recording section 20 by the supply transfer section 16 and the thermal head 66 is pressed against the thermal film A while the glaze 66a extends in the extending direction (see FIG. 1). Further, the thermosensitive film A is conveyed in a direction orthogonal to the paper surface of FIG. 2) and each thermosensitive recording point is heated in accordance with the recorded image, thereby recording the thermosensitive image on the thermosensitive film A.

The recording apparatus 10 of the illustrated example uses a heat sensitive film A as a heat sensitive recording material formed by forming a heat sensitive recording layer on a support such as a resin film or paper. The heat sensitive film A is a transparent polyethylene terephthalate. (PET)
A transparent film such as a film is used as a support, and a thermosensitive recording layer is formed on one surface of the support. Such a heat-sensitive film A is usually formed into a laminated body (bundle) of a predetermined unit such as 100 sheets and packaged in a bag or a band. In the illustrated example, the heat-sensitive recording layer is kept in a predetermined unit bundle. Are stored in the magazine 24 of the recording device 10 with the lower surface as the lower surface, and the magazines 2 are stored one by one.
4 and used for thermal image recording.

The magazine 24 is a housing having a lid 26 that can be opened and closed, and accommodates the thermosensitive film A to store the recording device 1 therein.
0 is loaded into the loading section 14. The loading unit 14 has an insertion opening 30, a guide plate 32, guide rolls 34, 34, and a stop member 36 formed in a housing 28 of the recording apparatus 10, and the magazine 24 has the lid 26 side first. The recording medium 10 is inserted into the recording device 10 through the insertion port 30, is guided by the guide plate 32 and the guide roll 34, and is pushed to a position where it comes into contact with the stop member 36, so that the recording device 10 is loaded at a predetermined position.

The feeding and conveying means 16 takes out the thermosensitive film A from the magazine 24 loaded in the loading section 14 and conveys it to the recording section 20, and uses a suction cup 40 for adsorbing the thermosensitive film A by suction. It has a mechanism, a conveyance means 42, a conveyance guide 44, and a regulation roller pair 52 located at the exit of the conveyance guide 44. The transport means 42 is
The conveying roller 46, a pulley 47 a coaxial with the conveying roller 46, a pulley 47 b connected to a rotation drive source, and a tension pulley 47 c, an endless belt 48 stretched over the three pulleys, and pressed by the conveying roller 46 Nip roller 50, and the leading end of the heat-sensitive film A sheet-leaved by the suction cup 40
6 and the nip roller 50 to convey the heat-sensitive film A.

When a recording start instruction is issued in the recording apparatus 10, the lid 26 is opened by an opening / closing mechanism (not shown), and the sheet-fed mechanism using the suction cup 40 takes out one thermal film A from the magazine 24, and the thermal film The leading end of A is supplied to the conveying means 42 (conveying roller 46 and nip roller 50). When the heat-sensitive film A is nipped by the conveyance roller 46 and the nip roller 50, the suction by the suction cup 40 is released, and the supplied heat-sensitive film A is guided by the conveyance guide 44 to the regulating roller pair 52 by the conveyance means 42. Conveyed. When the heat-sensitive film A to be used for recording is completely discharged from the magazine 24, the lid 26 is closed by the opening / closing means.

The distance from the conveying means 42 defined by the conveying guide 44 to the regulating roller pair 52 is set to be slightly shorter than the length of the heat sensitive film A in the conveying direction, and the heat sensitive film A is conveyed by the conveying means 42. The leading end of the sheet reaches the regulation roller pair 52, but the regulation roller pair 52 is initially stopped, and the leading edge of the heat-sensitive film A is temporarily stopped and positioned here. When the tip of the heat-sensitive film A reaches the regulation roller pair 52, the temperature of the thermal head 66 (glaze 66a) is confirmed, and the thermal head 66 is detected.
If the temperature is a predetermined temperature, the regulation roller pair 52 starts to convey the heat-sensitive film A, and the heat-sensitive film A is conveyed to the recording unit 20.

FIG. 2 shows a schematic diagram of the recording unit 20 and a block diagram of the image recording control system. The recording unit 20 has a thermal head 66, a platen roller 60, a cleaning roller pair 56, a guide 58, a cooling fan 76 (see FIG. 1) for cooling the thermal head 66, and a guide 62. The thermal head 66 is capable of recording an image up to a maximum B4 size, for example, and records about 300 dpi (pixels).
A thermal head for performing high-density thermal image recording, in which heating elements for thermal recording on the thermal film A are arranged in one direction (perpendicular to the paper surface in FIGS. 1 and 2) to form a glaze 66a. It has a main body 66b and a heat sink 66c fixed to the thermal head main body 66b. The thermal head 66 has an arrow a around a fulcrum 68a.
The support member 68 is rotatable in the opposite and opposite directions.

The platen roller 60 holds the heat sensitive film A at a predetermined position, rotates at a predetermined image recording speed, and conveys the heat sensitive film A in a direction orthogonal to the main scanning direction (direction of arrow b in FIG. 2). . The cleaning roller pair 56 is
It is a roller pair consisting of an adhesive rubber roller 56a and a normal roller 56b. The adhesive rubber roller 56a removes dust and the like adhering to the thermosensitive recording layer of the thermosensitive film A, and attaches the dust to the glaze 66a and the image Prevents adverse effects on records.

In the recording apparatus 10 of the illustrated example, before the heat-sensitive film A is conveyed, the supporting member 68 is rotated upward, that is, in the direction opposite to the arrow a direction, and the thermal head 66 (glaze 66a) and the platen are rotated. It is not in contact with the roller 60. When the transport by the above-mentioned regulation roller pair 52 is started, the heat-sensitive film A is then nipped by the cleaning roller pair 56 and further transported while being guided by the guide 58. When the leading edge of the thermosensitive film A is conveyed to the recording start position (the position corresponding to the glaze 66a), the support member 68 rotates in the direction of the arrow a, and the thermosensitive film A moves the glaze 66a of the thermal head 66 and the platen roller 60. Then, the glaze 66a is pressed by the recording layer, and the heat sensitive film A is held at a predetermined position by the platen roller 60, and the platen roller 60 (and the regulation roller pair 52 and the conveyance roller pair 63) is held.
Is transported in the direction of arrow b.

With this conveyance, the heat-sensitive recording is performed on the heat-sensitive film A by heating the respective heating elements of the glaze 66a according to the recorded image. Here, in the recording apparatus 10 of the present invention, this thermal recording is performed by the following recording control system.

As shown in the block diagram of FIG. 2, the thermal head main body 66b of the thermal head 66 has an image processing device 80, an image memory 82, and a recording control device 84.
Is connected.

The image data from the image data supply source R such as CT or MRI is sent to the image processing device 80. The image processing apparatus 80 is a combination of various image processing circuits and memories, and includes a density correction unit 86 that performs density correction,
An image processing unit 88 that performs various types of image processing such as sharpness correction is configured to receive image data (image information) from an image data supply source R, perform various types of correction and processing, and perform thermal recording. The heat-sensitive recording image data for

As described above, since the recording devices 10 have individual differences and the installation environments also differ, all recording devices 10 have a predetermined density according to the image data supplied from the image data supply source R. It is impossible to output the image of. In addition, the state of the recording device 10 changes with time,
For example, the glaze 66a becomes dirty or worn, the resistance value of the heating element changes, and the like, and the recording density of the image data also changes with time. Therefore, in the recording apparatus 10, a density correction condition for outputting an image of a predetermined density corresponding to the image data, such as a density correction function or a density correction table, is set for each image recording apparatus, and accordingly, The supplied image data is corrected, that is, the density is corrected. Further, in order to cope with the change with time, the density correction condition needs to be updated regularly, for example, every one week. The density correction unit 86 receives the image data of the image to be recorded from the image data supply source R, performs density correction on the image data according to a density correction condition described later, and then the image processing unit 88.
And the density correction condition is set.

As an example, the density correction condition is set in the following procedure. When the operator or the like issues an instruction to set (update) the density correction condition, the density correction unit 86
The image data of the density correction chart for setting the density correction condition is output to the image processing unit 88. After that, the image processing unit 88 performs a predetermined process on the image data and outputs it to the memory 82 as heat-sensitive record image data in the same manner as the normal image recording, and the heat-sensitive record image data is output by the recording control device 84. After being read, the thermal head 66 operates in response to this, and as described above, the thermal film A,
A density correction chart for setting density correction conditions, in which images of various densities are recorded, is recorded and output. The operations of the image processing unit 88, the memory 82 and the recording control device 84 will be described in detail later.

The density of each image on the density correction chart is measured by a densitometer, and the measurement result is input to the density correction unit 86 using the operation panel 90 of the recording apparatus 10 or the like. Upon receiving the measurement result, the density correction unit 86 receives the density measurement result and the image density of the recording apparatus 10, that is, the density correction unit 8
From the image density corresponding to the image data of the density correction chart output by the printer 6, the density of the image output by the recording apparatus 10 becomes a predetermined density according to the supplied image data (that is, the image correction condition). Data correction conditions) are set and stored. The density correction is performed based on this density correction condition.

Here, in the thermal recording, there is a threshold (threshold) for coloring with respect to the recording energy (heat energy), color is rapidly generated at the threshold, and the rising is also rapid. Therefore, if the density correction conditions are set using a normal method, good gradation reproducibility cannot be obtained, and in particular, the γ value becomes high in the highlight density part, and subtle gradation reproduction cannot be performed, resulting in high image quality. As described above, such an image cannot be recorded. On the other hand, in the recording apparatus 10 of the illustrated example, based on the density correction method of the present invention, the image data-density conversion condition according to the threshold is enlarged in the axial direction of the input image data (preprocessing) Setting the density correction condition by setting the temporary density correction condition using the data-density conversion condition and reducing the temporary image density correction condition according to the threshold in the output image data axis direction (post-processing). As a result, it is possible to stably obtain a high-quality heat-sensitive recorded image with good gradation reproducibility even in the highlight density portion.

Hereinafter, the thermal head 66 of the recording apparatus 10 will be described.
In FIG. 3, the relationship between the recording energy (heat energy) and the color density (D) is shown in the graph of FIG. 3A, and the density correction unit 86 takes the case where the color development threshold is point P as an example. A method of setting the density correction condition in the above will be described. In the following description, the value of the image data S _th corresponding to the color development threshold may be a little smaller than the point P because the highlight may cover the point P or just around the point P. In the recording apparatus 10 of the illustrated example, the image data from the image data supply source R is 10 bi.
Since it is sent as t (0-1023) digital data,
Obtains image data S _th corresponding to color threshold P, as shown in FIG. 3 (b), the image data S _th
3 to 1023 are image data 0 to 1023, the graph of FIG. 3A is enlarged in the input image data axis (X axis) direction (preprocessing). That is, the input image data X in FIG. 3A is converted into the following expression X _new = 1023 × ([X−S _th ] / [1023−
S _th ]) image data-density conversion conditions are set.

Next, from the image data-density conversion conditions shown in FIG. 3B, the density measurement result of the density correction chart, and the like, the supplied image data as shown in FIG. A temporary density correction condition for converting the input image data (X axis) into the output image data (Y axis) subjected to the density correction is set. As a temporary density correction condition setting method, various known gradation correction condition setting methods used in printers and the like using a silver salt film can be used. Energy 0
Various methods such as a method of setting a density correction condition using a gradation correction algorithm set corresponding to a system that smoothly rises from are available. A method for setting such density correction conditions is also disclosed in Japanese Patent Laid-Open No. 59-83150.

In the recording apparatus 10 of the illustrated example,
Image data received from the image data supply source R is 10 bits
However, in the density correction unit 86,
Since this image data is converted to 12 bits together with the density correction and various image processes thereafter are performed, the output image data is 0 to 409 under the temporary density correction condition shown in FIG.
5 and 12 bit digital data.

Finally, as shown in FIG. 3D, the output image data Y _new is converted from the image data S _th (10 bits to 12 bits) according to the image data S _th corresponding to the threshold P. Therefore, it will be 4 times) to 40
The temporary density correction condition shown in FIG. 3C is reduced in the direction of the output image data axis (Y axis) so that the area becomes area 95.
Complete the density correction conditions (post-processing). That is, FIG.
The output image signal Y of (c) is expressed by the following formula Y _new = Y × ([1023-S _th ] / 1023) × 4 +
The conversion is completed at S _th × 4 to complete the density correction condition, and the correction of the input image data supplied to the density correction unit 86, that is, the density correction is performed using this.

As described above, the image data from the image data supply source R such as CT or MRI is sent to the image processing apparatus 80, and the density correction section 86 performs density correction according to the density correction conditions. Then, it is sent to the image processing unit 88. The image processing unit 88 receives the image data from the density correction unit 86, and performs sharpness correction (sharpness processing) on the image data to emphasize the contour of the image; a proper image according to the γ value of the thermal film A or the like. Gradation correction to obtain
Temperature correction for adjusting the heat generation energy according to the temperature of the thermal recording point; Shading correction for correcting the density difference between the central portion and both ends of the glaze 66c; Resistance correction for correcting the difference in resistance value of each heating element; Performs predetermined image processing such as black ratio correction to produce image data corresponding to the same density at the same density regardless of the change in resistance value of the heating element; The thermal head 66
Output to the image memory 82 as heat-sensitive recording image data for heat-sensitive recording.

The recording control device 84 sequentially reads the thermal recording image data stored in the image memory 82 line by line in the extending direction of the glaze 66a, and records the recording data (output image density) corresponding to the read thermal recording image data. The voltage application time width according to the above is output to the thermal head 66. Each heating element of the thermal head 66 generates heat in accordance with recording data, and as described above, thermal image recording is performed while the thermal film A is conveyed in the direction of arrow b by the platen roller 60 or the like.

Thermal film A on which thermal image recording has been completed
While being guided by the guide 62, is transported to the platen roller 60 and the transport roller pair 63 and discharged to the tray 72 of the discharge unit 22. The tray 72 is projected to the outside of the recording apparatus 10 via a discharge port 74 formed in the housing 28, and the thermal film A on which an image is recorded is discharged to the outside via the discharge port 74 and taken out.

Although the density correction method of the present invention has been described in detail above, the present invention is not limited to the above examples, and various improvements and changes may be made without departing from the gist of the present invention. Of course.

[0036]

As described above in detail, according to the density correction method of the present invention, even in the highlight density portion, it is possible to obtain excellent gradation in the thermal image recording regardless of the threshold of color development. The tones can be reproduced, and a high-quality image having excellent gradation reproducibility can be stably formed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an example of a thermosensitive recording apparatus that implements a density correction method of the present invention.

FIG. 2 is a conceptual diagram of a recording unit of the thermal recording device shown in FIG.

3 (a), (b), (c) and (d) are graphs for explaining the density correction method of the present invention.

[Explanation of symbols]

 10 (Heat Sensitive) Recording Device 14 Loading Unit 16 Supply Conveying Unit 20 Recording Unit 22 Ejecting Unit 24 Magazine 26 Lid 28 Housing 30 Insertion Port 32 Guide Plate 34 Guide Roll 36 Stopping Member 40 Sucker 42 Conveying Means 44 Conveying Guide 48 Endless Belt 50 Nip roller 52 Control roller pair 56 Cleaning roller pair 58, 62 Guide 60 Platen roller 63 Conveying roller pair 66 Thermal head 68 Support member 72 Tray 74 Ejection port 76 Cooling fan 80 Image processing device 82 Image memory 84 Recording control device 86 Density correction unit 88 Image processing section A Thermal (recording) film

Claims (1)

[Claims] 1. A density correction method in heat-sensitive image recording, wherein a position corresponding to a recorded image of a heat-sensitive recording material is heated by a thermal head to record an image on the heat-sensitive recording material, wherein the heat-sensitive recording material develops color. According to the threshold value of the image data corresponding to the lowest recording energy, the threshold value is expanded in the axial direction of the input image data so as to be the lowest density data,
The conversion condition of the image data and the image density is set, then the temporary density correction condition is set by using this conversion condition, and then the temporary density correction is performed so that the threshold becomes the minimum density data of the output image data. A density correction method characterized in that the density correction condition is set by reducing the condition in the axial direction of the output image data, and the density correction is performed based on the density correction condition.