JPH1034997A - Thermal recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress fluctuation in the density of image due to abrasion of the protective film of a thermal head significantly by adding the total image data of image data of each pixel every time when the image of one pixel is recorded and calculating the grand total of the pixels of recorded image data and then correcting the image data to be supplied using the grand total. SOLUTION: The recorder performs weighting using an exponential function preset for an image data driving each pixel of a thermal head 66 and calculates the amount of corrosive abrasion of a protective film due to thermal recording of the image data approximately. It is then added in order to determine the accumulated amount of corrosive abrasion of the protective film for each pixel and an image data for driving the thermal head 66 is corrected depending on the accumulated amount of corrosive abrasion. Consequently, fluctuation of density due to corrosive abrasion of the protective film is corrected and thermal recording can be performed with high image quality over a long term. A thermal recording image data corrected at a thermo-history correcting section 82 is delivered to an image memory 84 and stored therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of a thermal recording apparatus using a thermal head.

[0002]

2. Description of the Related Art For recording an ultrasonic diagnostic image, an image recording using a heat-sensitive recording material (hereinafter referred to as a heat-sensitive material) formed by forming a heat-sensitive recording layer using a film or the like as a support (hereinafter also referred to as a heat-sensitive recording). ) Is used. In addition, thermal recording has advantages such as no need for wet development processing and easy handling, and in recent years, in recent years, not only small-sized image recording such as ultrasonic diagnosis but also CT diagnosis and MRI diagnosis have been performed. For applications requiring large and high-quality images, such as X-ray diagnosis and the like, the use for image recording for medical diagnosis is also being studied.

[0003] As is well known, thermal recording uses a thermal head having a glaze in which heating elements are arranged in one direction (main scanning direction) for recording an image by heating a thermal recording layer of a thermal material. Glaze to heat-sensitive material (heat-sensitive recording layer)
In a state in which both are moved slightly in the sub-scanning direction orthogonal to the main scanning direction while slightly pressed, the respective glazes in accordance with the image data of the recording image supplied from an image data supply source such as MRI. By applying energy to the heating elements of the pixels and generating heat in accordance with the recorded image, the thermosensitive recording layer of the thermosensitive material is heated to perform image recording.

[0004]

Incidentally, a protective film is formed on the glaze of the thermal head to protect a heating element or the like that overheats the heat-sensitive material. Therefore, it is the protective film that comes into contact with the thermal material during thermal recording, and the heating element overheats the thermal material through the protective film, thereby performing thermal recording. As a protective film,
Usually, a ceramic having abrasion resistance is used, but the protective film slides on a heat-sensitive material in an overheated state at the time of heat-sensitive recording, and thus wears and deteriorates as image recording is performed. As the wear of the protective film progresses, the heat capacity of the protective film decreases, and as a result, the amount of heat of the heat-sensitive material with respect to the amount of heat generated by the heating element (that is, the applied energy) increases.
Therefore, in thermal recording using a thermal head, the recording sensitivity increases with time, and the applied energy, that is, the recording density for image data, increases.

Here, in thermal recording by a thermal head, all pixels do not always record an image of the same density, and the amount of heat generated by the heating element of each pixel differs according to the recorded image. In other words, the thermal history received by each pixel of the thermal head usually differs for each pixel. for that reason,
The degree of progress of wear of the protective film differs for each pixel, and a difference occurs in the amount of change in recording density with respect to image data for each pixel, which is one of the causes of image density unevenness.

[0006] Such density unevenness naturally causes deterioration of the image quality of a recorded image. In particular, in the medical applications described above, a high-quality multi-tone image is required,
Since the density unevenness is a serious problem that leads to a diagnosis error, the allowable level for the density unevenness is very severe, and a solution is desired.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, and to greatly reduce image density unevenness caused by abrasion of a protective film of a thermal head due to superimposed thermal recording. Another object of the present invention is to provide a thermal recording apparatus capable of stably recording a high-quality thermal image over the entire image recording.

[0008]

According to the present invention, there is provided a thermal recording apparatus for recording an image by driving a thermal head in accordance with image data supplied from an image data supply source. Means for performing predetermined weighting on image data recorded by the thermal head using an exponential function, and calculating, for each pixel of the thermal head, a total of one image of the weighted image data;
Means for adding the total of the image data of each pixel for each image recording of one image to calculate a total amount of the recorded image data for each pixel, and storing the total; A thermal recording apparatus, comprising: a correction unit configured to correct supplied image data.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thermal recording apparatus according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a schematic diagram showing an example of a thermal recording apparatus according to the present invention. A thermosensitive recording device 10 (hereinafter, referred to as a recording device 10) shown in FIG. 1 is a thermosensitive recording material (hereinafter, referred to as a cut sheet of a predetermined size such as B4 size).
The heat-sensitive material A is subjected to thermal recording, and the loading unit 1 in which the magazine 24 in which the heat-sensitive material A is stored is loaded.
4. Supply / transport section 16, recording section 20 for performing thermal recording on thermal material A by thermal head 66, and discharge section 22
Is configured. As shown in FIG. 2, the thermal head 66 is connected to an image processing unit 80, a thermal history correction unit 82, an image memory 84, and a recording control unit 86.

In such a recording apparatus 10, one heat-sensitive material A is pulled out from the magazine 24, the heat-sensitive material A is transported to the recording section 20, and the thermal head 66 is pressed against the heat-sensitive material A while the glaze is extended. The heat-sensitive material A is transported in the sub-scanning direction (the direction indicated by the arrow X in the drawing) orthogonal to the existing direction, that is, the main scanning direction (the direction perpendicular to the paper in FIGS. 1 and 2), and heats the respective heating elements according to the recorded image. Thus, heat-sensitive recording is performed on the heat-sensitive material A.

The heat-sensitive material A is formed by using a resin film such as a transparent polyethylene terephthalate (PET) film or paper as a support and forming a heat-sensitive recording layer on one surface thereof. Such a heat-sensitive material A is usually formed into a laminate (bundle) of a predetermined unit of, for example, 100 sheets and packaged with a bag or a band. Are placed in the magazine 24 of the recording apparatus 10 with the sheet as the lower surface, and are taken out one by one from the magazine 24 and subjected to thermal recording.

The magazine 24 is a housing having a lid 26 that can be opened and closed. The magazine 24 stores the heat-sensitive material A and is loaded in the loading section 14 of the recording apparatus 10. The loading unit 14 includes the recording device 10
Insertion hole 30 formed in housing 28 of
And guide rolls 34, 34, and a stop member 36. The magazine 24 is inserted into the insertion port 30 with the lid 26 side first.
Then, while being guided by the guide plate 32 and the guide roll 34 and being pushed to a position where it comes into contact with the stop member 36, the recording device 10 is loaded into a predetermined position of the recording device 10. The loading section 14 is provided with an opening / closing mechanism (not shown) for opening and closing the lid 26 of the magazine. In addition, as an opening and closing mechanism of this lid 26,
Various known lid opening / closing mechanisms can be used.

The supply / transportation means 16 takes out one heat-sensitive material A from the magazine 24 loaded in the loading section 14 and transports it to the recording section 20, and uses a suction cup 40 which adsorbs the heat-sensitive material A by suction. Single wafer mechanism, conveyance means 4
2, a transport guide 44, and a pair of regulating rollers 52 located at the exit of the transport guide 44. The conveying means 42 includes a conveying roller 46 and a pulley 4 coaxial with the conveying roller 46.
7a, a pulley 47b and a tension pulley 47c connected to a rotary drive source, an endless belt 48 stretched over the three pulleys, and a nip roller 50 forming a roller pair with the transport roller 46. 40
The leading end of the heat-sensitive material A sheet-fed by the conveying roller 46
And the nip roller 50 to transport the heat-sensitive material A.

When a recording start instruction is issued in the recording apparatus 10, the lid 26 is opened by the opening / closing mechanism,
The sheet-feeding mechanism using the suction cup 40 takes out one heat-sensitive material A from the magazine 24 and transports the front end of the heat-sensitive material A to the conveying means 42.
(A roller pair composed of the transport roller 46 and the nip roller 50). When the heat-sensitive material 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 material A is guided by the conveyance guide 44 to the regulating roller pair 52 by the conveyance means 42. Conveyed. When the heat-sensitive material 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 conveyance means 42 defined by the conveyance guide 44 to the regulating roller pair 52 is set slightly shorter than the length of the heat-sensitive material A in the conveyance direction. The leading end of the heat-sensitive material A reaches the regulating roller pair 52 by the conveyance by the conveying means 42, but the regulating roller pair 52 is initially stopped, and the leading end of the heat-sensitive material A is temporarily stopped and positioned here. At the time when the tip of the heat-sensitive material A reaches the regulating roller pair 52, the temperature of the thermal head 66 (glaze 66a) is confirmed. Is started, and the heat-sensitive material A is conveyed to the recording unit 20.

FIG. 2 is a schematic diagram of the recording unit 20. The recording unit 20 includes a thermal head 66, a platen roller 60,
It has a pair of cleaning rollers 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 (thermal head main body 66b) is connected to an image processing unit 80, a thermal history correction unit 82, an image memory 84, and a recording control unit 86 that constitute a recording control system. Here, the heat history correction unit 8
2 is a characteristic part of the present invention. Thermal head 6
Numeral 6 is for performing thermal recording at a recording (pixel) density of about 300 dpi, for example, capable of recording an image up to a maximum of B4 size. Glaze 66a arranged in the scanning direction)
And a heat sink 66c fixed to the thermal head body 66b. The thermal head 66 is supported by a support member 68 that is rotatable about a fulcrum 68a in the direction of arrow a and in the opposite direction. The glaze 66a has its surface covered with a protective layer made of wear-resistant ceramic.

The platen roller 60 rotates at a predetermined image recording speed while holding the heat-sensitive material A at a predetermined position, and moves the heat-sensitive material A in a sub-scanning direction (arrow X direction) orthogonal to the main scanning direction.
Is transported. The cleaning roller pair 56 is a roller pair including an adhesive rubber roller 56a, which is an elastic body, and a normal roller 56b. The adhesive rubber roller 56a removes dust and the like adhering to the heat-sensitive recording layer of the heat-sensitive material A, and glazes 66a. This prevents dust from adhering to the surface and adversely affecting image recording.

In the illustrated recording apparatus 10, before the heat-sensitive material A is conveyed, the support member 68 is rotated upward (in a direction opposite to the direction of arrow a), and is moved between the thermal head 66 (glaze 66a) and the thermal head 66 (glaze 66a). There is no contact with the platen roller 60. When the conveyance by the above-described regulating roller pair 52 is started, the heat-sensitive material A is then nipped by the cleaning roller pair 56 and further conveyed while being guided by the guide 58. When the leading end of the heat-sensitive material A is transported to the recording start position (the position corresponding to the glaze 66a), the support member 68
Is rotated in the direction of arrow a, the thermal material A is sandwiched between the glaze 66a of the thermal head 66 and the platen roller 60, and the glaze 66a is pressed against the recording layer. While being held at a predetermined position, the sheet is conveyed in the direction of arrow b by the platen roller 60 (and the pair of regulating rollers 52 and the pair of conveying rollers 63). Along with this conveyance, the heating element of each pixel of the glaze 66a is heated according to the recorded image, so that the thermal recording is performed on the thermal material A.

Image data from an image data source R such as CT or MRI is sent to an image processing unit 80. The image processing unit 80 receives the image data from the image data supply source R, performs formatting (enlargement / reduction of the image, frame allocation) as necessary, and uses the image data to emphasize the outline of the image. Sharpness treatment; γ of heat-sensitive material A
Gradation correction for obtaining an appropriate image according to the value, etc .; temperature correction for adjusting the heat generation energy according to the temperature of the heating element of each pixel; variations in the shape of the glaze 66a and the center and both ends in the main scanning direction. Correction for correcting the difference in density of the pixels; resistance correction for correcting the difference between the resistance values of the heating elements of the respective pixels; color development at a density corresponding to the image data irrespective of the change in the power supply voltage drop of the thermal head due to a change in the recording pattern. , And outputs it to the thermal history correction unit 82 as thermal recording image data for thermal recording by the thermal head 66.

As described above, the surface of the glaze 66a is:
It is covered with a protective film to protect the heating elements, etc.
Since the protective film is overheated and comes into sliding contact with the heat-sensitive material A, it gradually wears as heat-sensitive recording is repeated. Here, the abrasion of the protective film is not uniform over all the pixels, but differs according to the thermal history of each pixel. This is one of the causes of the density unevenness of the image. The thermal history correction unit 82 corrects image density unevenness caused by abrasion of the protective film of each pixel of the glaze 66a of the thermal head 66, so that even if a large number of images are recorded, a high-quality high-order image without uneven image density can be obtained. This is for stably forming a toned image.

FIG. 3 conceptually shows the progress of wear of the protective film of the glaze 66a. As shown in FIG. 3, the abrasion of the protective film proceeds in a substantially conical shape corresponding to only the portion that is actually overheated. That is, the thermal head 66
In the corrosion of the glaze 66a, the bottom area of the cone hardly changes and only the height (depth) increases, and the corrosion proceeds. Therefore, the degree of progress of corrosion, that is, the amount of corrosion (volume) V can be represented by the depth L of corrosion.

FIG. 4 shows an example of the relationship between the applied energy and the logarithm of the corrosion depth L of the protective film when the thermal recording is performed at a predetermined distance. The applied energy and the progress of the corrosion of the protective film are shown. It can be seen that the amount of corrosion increases exponentially with an increase in the applied energy. Further, FIG. 5 shows an example of the relationship between the recording distance l and the corrosion depth (logarithm) L of the protective film when the applied energy is constant. In the example shown in FIG. 5, a is an example where the applied energy is 70 mJ / mm ² , and b is an example where the applied energy is 50 mJ / mm ^2.
It is an example of a mJ / mm ^2. As shown in FIG. 5, in the thermal recording, between the recording distance and the progress of corrosion of the protective film,
There is a linear relationship, and the amount of corrosion linearly increases as the recording distance increases.

The inventor of the present invention concluded that the abrasion of the protective film of the thermal head 66 is not physical abrasion but rather chemical corrosion, and the amount of the corrosion depends on the applied energy. Has found that it can be approximately predicted by putting it on a mathematical expression using an exponential function.

As is well known, the rate constant k of a chemical reaction is expressed by the Arrhenius equation k = A × exp (−E / RT) [or lnk = lnA−
(E / RT)], and the reaction amount V can be approximately indicated by k × t (reaction time). Thermal head 66
If the wear of the protective film is chemical corrosion wear, the wear should proceed in accordance with the above equation, and the reaction temperature T, that is, the reciprocal (1 / T) of the temperature of the protective film due to the heat generated by the heating element and lnk
If a so-called Arrhenius plot is performed, the relationship should be a straight line having a slope of (−E / RT).

In the thermal head 66, the reaction temperature is the temperature of the heating element (that is, the protective film), and this temperature rises in proportion to the rise in applied energy.
The reaction temperature can be replaced by the applied energy. Further, as described above, the corrosion amount, which is the reaction amount, is the corrosion depth L.
Further, the depth L of corrosion when a predetermined distance is recorded is proportional to the rate constant k. From the above, as shown in FIG. 4, the applied energy and the logarithm of the corrosion depth L of the protective film have a linear relationship, and FIG.
As shown in the above, the fact that the logarithm of the corrosion depth L of the protective film and the recording distance also have a linear relationship indicates that the wear of the protective film of the thermal head 66 is chemical corrosion wear, and is expressed by Arrhenius equation. As shown in the figure, it progresses exponentially. Further, as shown in FIG. 3, the fact that the progress of corrosion progresses in a conical shape in a low area is not abrasion due to physical friction, but the wear of the protective film of the thermal head 66 is caused by chemical corrosion wear. Is shown.

Therefore, by using a preset exponential function, the amount of corrosion of the protective film due to the image recording can be estimated from the applied energy, that is, the image data for driving each pixel of the thermal head 66. The recording apparatus 10 according to the present invention utilizes this to perform a weighting using a preset exponential function on the image data for driving each pixel of the thermal head 66, so that the recording apparatus 10 can respond to the image data. Approximately calculate the amount of corrosion of the protective film (or a numerical value corresponding to the amount of corrosion) by the thermal recording, and add up this to find out the amount of corrosion of the protective film of each pixel up to the present. By correcting the image data for driving the thermal head 66, density unevenness due to abrasion of the protective film is corrected, and high-quality thermal recording can be performed for a long period of time.

The thermal history correction unit 82 generates a histogram using, as a parameter, image data of thermal recording (image data output from the thermal history correction unit 82 to the image memory 84) x for each thermal recording of one image. create. Next, weighting is performed on the image data x, which is a parameter of the histogram, using an exponential function created in advance, expressed by the following equation y = Aexp (Bx), to approximate the corrosion amount y corresponding to the image data x. Is calculated. A and B are constants appropriately determined according to the characteristics of the heat-sensitive material and the thermal head.
Can be obtained experimentally by creating a graph shown in FIG. It should be noted that the corrosion amount y for the image data
May be calculated in advance and stored in the heat history correction unit 82. Furthermore, using the created histogram,
The amount of corrosion y in the thermal recording of one image of each pixel is added,
The total corrosion amount Y in one image recording is calculated for each pixel. The total corrosion amount Y calculated for each pixel is added each time image recording is performed, and is stored as the total amount of corrosion of the protective film for each pixel by thermal recording until now, that is, the accumulated corrosion amount Z. Is done.

The accumulated heat amount Z
A correction formula for density unevenness caused by corrosion of the protective film of the thermal head 66 using, for example, the following formula: En = Eo × (1-k ×) where En is the corrected image data and Eo is the supplied image data. Z) is previously set and stored, and the thermal history correction section 82 uses the equation and the accumulated corrosion amount Z up to the previous time to convert the image data Er supplied from the image processing section 80 into the correction data. The image data is corrected and output to the image memory 84. In the above equation, k is a constant appropriately determined according to the characteristics of the thermal head 66 and the like. Further, the heat history correction unit 82 uses the corrected image data by using En,
As described above, a histogram of one image recording is created, and the accumulated corrosion amount Z is updated.

It is naturally most preferable to calculate the accumulated corrosion amount Z in accordance with all the pixels. However, if the memory capacity is limited, for example, one out of five pixels or ten pixels is used.
The accumulated corrosion amount may be representatively calculated for each pixel at a predetermined interval such as a pixel, and the representative accumulated corrosion amount may be corrected as the accumulated corrosion amount Z of the corresponding pixel. The accumulated corrosion amount Z of all pixels may be calculated by interpolation or the like using the amount. Further, the step size of the image data of the density histogram may be appropriately determined according to the available memory capacity and the like. Further, instead of creating a histogram for each image, a histogram may be created for a plurality of thermal recordings, and the accumulated corrosion amount Z may be updated.

The thermal recording image data corrected by the thermal history correction section 82 is sent to an image memory 84 and stored therein. The recording control device 84 sequentially reads out the thermal recording image data stored in the image memory 84 line by line in the main scanning direction in accordance with the recording order, and records data (output image density) corresponding to the read thermal recording image data. Is output to the thermal head 66. Each heating element point of the thermal head 66 generates heat in accordance with the recording data, and the heat-sensitive material A is applied to the platen roller 60 as described above.
The thermal recording is performed while being conveyed in the direction of arrow b by the above method.

The heat-sensitive material A on which the heat-sensitive recording is completed is conveyed by the platen roller 60 and the conveyance roller pair 63 while being guided by the guide 62, and is discharged to the tray 72 of the discharge section 22. The tray 72 protrudes outside the recording apparatus 10 through a discharge port 74 formed in the housing 28, and the heat-sensitive material A on which an image is recorded is discharged to the outside through the discharge port 74 and is taken out.

Although the thermal recording apparatus of the present invention has been described in detail above, the present invention is not limited to the above-described examples, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

[0034]

As described in detail above, according to the thermal recording apparatus of the present invention, even when thermal recording is performed on a large number of sheets, it is possible to prevent the occurrence of density unevenness due to abrasion of the protective film. It is possible to stably obtain a high-quality thermal recording image over a long period of time.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an example of a thermal recording apparatus of the present invention.

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

FIG. 3 is a conceptual diagram for explaining wear of a protective film of a thermal head.

FIG. 4 is a graph showing a relationship between wear of a thermal head protective film and applied energy.

FIG. 5 is a graph showing the relationship between the wear of the thermal head protective film and the recording distance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 (Thermal) recording device 14 Loading part 16 Supply / conveyance means 20 Recording part 22 Ejection part 24 Magazine 26 Lid 28 Housing 30 Insertion port 32 Guide plate 34 Guide roll 36 Stop member 40 Sucker 42 Transporting means 44 Transport guide 48 Endless belt 50 Nip roller 52 Regulator roller pair 56 Cleaning roller pair 58, 62 Guide 60 Platen roller 63 Transport roller pair 66 Thermal head 68 Support member 72 Tray 74 Discharge port 76 Cooling fan 80 Image processing unit 82 Heat history correction unit 84 Image memory 86 Recording control unit A heat-sensitive material

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 22, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

FIG. 3 conceptually shows the progress of wear of the protective film of the glaze 66a. As shown in FIG. 3, the abrasion of the protective film proceeds in a substantially conical shape corresponding to only the portion that is actually overheated. That is, the thermal head 66
In the abrasion of the glaze 66a, the bottom area of the cone hardly changes, and only the height (depth) increases, leading to abrasion . Therefore, the degree of progress of wear , that is, the amount of wear (volume) V can be represented by the depth L of wear .

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0023

[Correction method] Change

[Correction contents]

FIG. 4 shows an example of the relationship between the applied energy and the logarithm of the abrasion depth L of the protective film when performing thermal recording at a predetermined distance. The applied energy and the abrasion depth of the protective film are shown.
There is a linear relationship with the logarithm of the progress of L , and it can be seen that the amount of wear increases exponentially as the applied energy increases. FIG. 5 shows the recording distance l and the wear depth (logarithm) L of the protective film when the applied energy is constant.
An example of the relationship with is shown. In the example shown in FIG.
In the example application energy of 70mJ / mm ^2, b is applied energy is an example of 50 mJ / mm ^2. As shown in FIG. 5, in thermal recording, there is a linear relationship between the recording distance and the progress of wear of the protective film, and the amount of wear linearly increases as the recording distance increases.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

The inventor of the present invention concluded that the abrasion of the protective film of the thermal head 66 is not physical abrasion but rather chemical corrosion.
It has been found that the amount of wear can be approximately predicted from the applied energy by using a mathematical formula using an exponential function.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

In the thermal head 66, the reaction temperature is the temperature of the heating element (that is, the protective film), and this temperature rises in proportion to the rise in applied energy.
The reaction temperature can be replaced by the applied energy. Further, as described above, the corrosion amount, which is the reaction amount, is equal to the wear depth L.
, And the depth L of wear when recording for a predetermined distance is proportional to the rate constant k. From the above, as shown in FIG. 4, the applied energy and the logarithm of the wear depth L of the protective film have a linear relationship, and FIG.
The fact that the logarithm of the abrasion depth L of the protective film and the recording distance also have a linear relationship as shown in the above indicates that the abrasion of the protective film of the thermal head 66 is a chemical corrosion abrasion. As shown in the figure, it progresses exponentially. Further, as shown in FIG. 3, the fact that the wear progresses in such a manner that the low area progresses in a constant conical shape is not the wear due to physical friction, but the wear of the protective film of the thermal head 66. Indicates chemical corrosion wear.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

Accordingly, by using a preset exponential function, the amount of corrosion and abrasion of the protective film due to the image recording can be estimated from the applied energy, that is, the image data for driving each pixel of the thermal head 66.
Recording apparatus 10 according to the present invention, by using this, the image data for driving each pixel of the thermal head 66, by performing weighting using the exponential function which is set in advance, in accordance with the image data Approximately calculate the amount of corrosion and wear of the protective film by thermal recording (or a numerical value corresponding to the amount of corrosion and wear ), and add this to find out the amount of corrosion and wear of the protective film of each pixel up to the present, By correcting the image data for driving the thermal head 66 accordingly, unevenness in density due to corrosion and abrasion of the protective film is corrected, and high-quality thermal recording can be performed for a long period of time.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

The thermal history correction unit 82 generates a histogram using, as a parameter, image data of thermal recording (image data output from the thermal history correction unit 82 to the image memory 84) x for each thermal recording of one image. create. Next, weighting is performed on the image data x, which is a parameter of the histogram, using an exponential function created in advance, represented by the following equation y = Aexp (Bx), and the corrosion wear amount y corresponding to the image data x is calculated. Approximately calculated. A and B are constants appropriately determined according to the characteristics of the heat-sensitive material and the thermal head, for example,
By creating the graph shown in FIG. 4, it can be obtained experimentally. Incidentally, corrosion grinding for the image data
Worn amount y may be stored in the thermal history correction unit 82 previously calculated. Further, using the created histogram, the amount of corrosion and wear y in the thermal recording of one image of each pixel is calculated.
Is added, and the total corrosion and wear amount Y in one image recording is calculated for each pixel. Total corrosion wear amount Y calculated for each pixel
Is added each time image recording is performed, and is stored as the total amount of corrosion wear of the protective film for each pixel, that is, the accumulated corrosion wear Z, by thermal recording until now.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

The thermal history correction unit 82 uses the accumulated corrosion wear amount Z to correct the density unevenness caused by the corrosion wear of the protective film of the thermal head 66, for example, a correction formula. A correction formula expressed by the following formula, En = Eo × (1−k × Z), where En is the input image data and supplied image data Eo, is set and stored in advance. The image data Er supplied from the image processing unit 80 is corrected using this equation and the accumulated corrosion wear amount Z up to the previous time, and output to the image memory 84. In the above equation, k is a constant appropriately determined according to the characteristics of the thermal head 66 and the like. Further, the thermal history correction unit 82 creates a histogram of one-image recording using the corrected image data En and updates the accumulated corrosion wear amount Z as described above.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0030

[Correction method] Change

[Correction contents]

It is naturally most preferable to calculate the accumulated corrosion wear amount Z according to all the pixels. However, if the memory capacity is limited, for example, one pixel out of every five pixels or ten pixels is used. The accumulated corrosion wear amount is typically calculated for each pixel at a predetermined interval such as, and the representative accumulated corrosion wear amount may be corrected as the accumulated corrosion wear amount Z of the corresponding pixel, or Alternatively, the accumulated corrosion wear Z of all pixels may be calculated by interpolation or the like using the representative accumulated corrosion wear . Further, the step size of the image data of the density histogram may be appropriately determined according to the available memory capacity and the like. Further, instead of creating a histogram for each image, a histogram may be created for a plurality of thermal recordings, and the accumulated corrosion wear amount Z may be updated.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction contents]

The thermal recording image data corrected by the thermal history correction section 82 is sent to an image memory 84 and stored therein. The recording control unit 86 sequentially reads out the thermal recording image data stored in the image memory 84 line by line in the main scanning direction according to the recording order, and records the recording data (output image density) according to the read thermal recording image data. Is output to the thermal head 66. Each heating element point of the thermal head 66 generates heat according to the recording data, and as described above, the thermal recording is performed while the thermal material A is conveyed in the direction of the arrow b by the platen roller 60 or the like.

Claims (1)

[Claims] 1. A thermal recording apparatus for recording an image by driving a thermal head in accordance with image data supplied from an image data supply source, wherein an exponential function is used for the image data recorded by the thermal head. Means for calculating a total weight of one image of the weighted image data for each pixel of the thermal head by performing predetermined weighting for each pixel of the thermal head; and calculating a total of the image data of each pixel for each image recording of one image. It is characterized in that it has means for calculating and storing the sum of the recorded image data for each pixel and storing the sum, and correcting means for correcting the image data supplied from the image data supply source using the sum. Thermal recording device.