JP3554431B2 - Thermal recording device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field of a thermal recording apparatus using a thermal head.
[0002]
[Prior art]
For recording an ultrasonic diagnostic image, image recording using a heat-sensitive recording material such as a heat-sensitive recording film (hereinafter, referred to as a heat-sensitive film) formed by forming a heat-sensitive recording layer using a film as a support (hereinafter, also referred to as a heat-sensitive image recording) ) Is used.
Further, such thermal image recording has advantages such as no necessity of wet development processing and easy handling, and in recent years, not only small-sized image recording such as ultrasonic diagnosis but also MRI For applications requiring large and high-quality images, such as diagnostics and X-ray diagnostics, use for image recording for medical diagnosis is also being studied.
[0003]
As is well known, thermal image recording uses a thermal head having a glaze in which heating elements are arranged in one direction, and both are orthogonal to the glaze with the glaze slightly pressed against a thermal film (thermosensitive recording layer). By applying energy to each heating element while relatively moving in the direction, the heat-sensitive recording layer of the heat-sensitive film is heated to record an image.
[0004]
[Problems to be solved by the invention]
By the way, the resistance value of the heating element of the thermal head changes according to the heating time and the heating energy. Since the heating element is a heating element, for example, the amount of heat generated increases as the resistance value decreases, and the temperature of the heating element increases as much as the resistance value decreases, resulting in an increase in image density. The density image cannot be recorded.
In addition, since the heat generation history of each heat generating element of the thermal head mounted on the thermal recording apparatus (how much heat is generated with respect to the performed image recording = the total heat generation amount) is naturally different from each other. The amount of change also differs for each heating element. Therefore, as the image recording is performed, a difference (variation in the resistance value) occurs in the resistance change amount of each heating element, and density unevenness occurs in the recorded image according to the difference.
[0005]
In order to solve this, in an image recording apparatus using a thermal head, image recording is performed by performing image correction according to the resistance value of each heating element, so-called resistance value correction, at the time of image recording.
However, as disclosed in Japanese Patent Publication No. 3-37512, in an image recording apparatus using a conventional thermal head, resistance correction is performed by measuring the resistance of each heating element and using the resistance. Therefore, it is not possible to sufficiently correct the density unevenness caused by the variation in the resistance value of each heating element.
[0006]
Such density unevenness of the recorded image causes a deterioration in the quality of the finished image, and is a serious problem in applications requiring high-quality image recording. In particular, high-quality images are required for medical applications as described above, and density unevenness is a serious problem that leads to obstruction of image observation and diagnostic errors.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. In a thermal recording apparatus using a thermal head, density unevenness caused by variation in resistance value of each heating element is sufficiently corrected by resistance value correction. It is an object of the present invention to provide a thermal recording apparatus capable of stably forming a high-quality image without density unevenness.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a thermal head having a glaze formed by arranging heating elements in one direction, and contacting the glaze with a thermosensitive recording material to be orthogonal to the arrangement direction of the heating elements. Means for relatively moving the thermal head and the thermal recording material in the direction, receiving image data from an image data supply source, performing image processing including resistance value correction on the image data, and forming an image as thermal recording image data A processing unit, and a temperature measuring unit for a thermal head, wherein the image processing unit sets the respective resistance values on the basis of the maximum resistance value of the heating element excluding both ends in the extending direction of the grace. in response are those performing the resistance value corrected using the resistance correction data set for each heating element, and temperature of the thermal head or the image data values of the recorded image, if In response to both, to provide a thermal recording apparatus comprising means for adjusting the correction coefficient of the resistance correction.
[0010]
In the thermal recording apparatus, it is preferable that the resistance value correction data is subjected to a spatial frequency process.
[0011]
Further, in the image recording apparatus, it is preferable that the image processing unit updates the resistance value correction data every time a predetermined number of images are recorded.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the thermal recording apparatus of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
[0013]
FIG. 1 shows a schematic diagram of an example of the thermal recording apparatus of the present invention.
A thermosensitive recording device 10 (hereinafter, referred to as a recording device 10) shown in FIG. 1 records a thermosensitive image on a thermosensitive recording film (hereinafter, referred to as a thermosensitive film A) which is a cut sheet of a predetermined size such as a B4 size. A recording unit 20 for recording a thermal image on the thermal film A by a thermal head 66, and a discharge unit 22. The loading unit 14, in which the magazine 24 containing the thermal film A is loaded, is provided. It is composed. As shown in FIG. 3, an image processing unit 80, an image memory 82, and a recording control unit 84 are connected to the thermal head 66 of the recording unit 20, and a correction data storage unit 86 is further connected to the image processing unit 80. Is connected.
[0014]
In such a recording apparatus 10, the thermal film A is transported to the recording unit 20 by the supply transport unit 16, and the thermal head 66 is pressed against the thermal film A while being perpendicular to the extending direction of the glaze 66 a of the thermal head 66. The heat-sensitive film A is conveyed in the direction to be heated (see FIG. 2), and each heat-generating element is heated according to the recorded image, so that the heat-sensitive image is recorded on the heat-sensitive film A.
[0015]
The recording apparatus 10 in the illustrated example uses a heat-sensitive film A as a heat-sensitive recording material having a heat-sensitive recording layer formed on a surface thereof, such as a resin film or paper as a support. The heat-sensitive film A is, for example, a transparent film. A transparent film such as a polyethylene terephthalate (PET) film is used as a support, and a heat-sensitive recording layer is formed on one surface thereof.
Such a heat-sensitive film A is usually formed into a laminate (bundle) of a predetermined unit of 100 sheets or the like and packaged with a bag or a band. Are placed in the magazine 24 of the recording apparatus 10 with the surface as a lower surface, and are taken out of the magazine 24 one by one and provided for thermal image recording.
[0016]
The magazine 24 is a housing having a lid 26 that can be opened and closed. The magazine 24 stores the heat-sensitive film A and is loaded in the loading section 14 of the recording apparatus 10.
The loading section 14 has an insertion opening 30, a guide plate 32, guide rolls 34 and 34, and a stop member 36 formed in a housing 28 of the recording apparatus 10, and the magazine 24 is arranged such that the lid 26 side is first. It is inserted into the recording device 10 from the insertion opening 30 and is pushed to a position where it comes into contact with the stop member 36 while being guided by the guide plate 32 and the guide roll 34, so that the recording device 10 is loaded at a predetermined position.
[0017]
The supply / conveyance means 16 is for taking out the thermal film A from the magazine 24 loaded in the loading unit 14 and transporting the thermal film A to the recording unit 20, and a sheet-feeding mechanism using a suction cup 40 for sucking the thermal film A by suction. It has a means 42, a transport guide 44, and a pair of regulating rollers 52 located at the outlet of the transport guide 44.
The conveying means 42 includes a conveying roller 46, a pulley 47 a coaxial with the conveying roller 46, a pulley 47 b connected to a rotation driving source and a tension pulley 47 c, an endless belt 48 stretched over the three pulleys, The heat-sensitive film A is conveyed by holding the front end of the heat-sensitive film A, which has been sheet-fed by the suction cup 40, between the conveyance roller 46 and the nip roller 50.
[0018]
When an instruction to start recording is issued in the recording apparatus 10, the lid 26 is opened by an opening / closing mechanism (not shown), and the sheet-feeding mechanism using the suction cup 40 takes out one heat-sensitive film A from the magazine 24, and the leading end of the heat-sensitive film A Is supplied to the transport means 42 (the transport roller 46 and the nip roller 50). When the thermal film A is nipped by the transport roller 46 and the nip roller 50, the suction by the suction cup 40 is released, and the supplied thermal film A is guided by the transport guide 44 to the regulating roller pair 52 by the transport unit 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.
[0019]
The distance from the conveying means 42 defined by the conveying guide 44 to the regulating roller pair 52 is set slightly shorter than the length of the heat-sensitive film A in the conveying direction. After reaching the regulating roller pair 52, the regulating roller pair 52 is initially stopped, and the leading end of the heat-sensitive film A is temporarily stopped and positioned here.
When the leading end of the heat-sensitive film A reaches the regulating roller pair 52, the temperature of the thermal head 66 (glaze 66a) is confirmed. If the temperature of the thermal head 66 is a predetermined temperature, the heat-sensitive film A by the regulating roller pair 52 is detected. Is started, and the heat-sensitive film A is conveyed to the recording unit 20.
[0020]
FIG. 2 shows a schematic diagram of the recording unit 20.
The recording unit 20 includes 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 for performing thermal image recording at a recording (pixel) density of about 300 dpi, for example, capable of recording an image up to a maximum of B4 size, and has one heating element for performing thermal recording on the thermal film A. A thermal head main body 66b formed with a glaze 66a arranged in a direction (a direction perpendicular to the paper surface in FIGS. 1 and 2 and an arrow c in FIG. 3) and a heat sink 66c fixed to the thermal head main body 66b (FIG. 3) reference). The thermal head 66 is supported by a support member 68 that is rotatable around a fulcrum 68a in the direction of arrow a and in the opposite direction.
[0021]
The platen roller 60 rotates at a predetermined image recording speed while holding the heat-sensitive film A at a predetermined position, and conveys the heat-sensitive film A in a direction perpendicular to the extending direction of the glaze 66a (the direction of the arrow b in FIG. 2). .
The cleaning roller pair 56 is a roller pair including an adhesive rubber roller 56a and a normal roller 56b, and the adhesive rubber roller 56a removes dust and the like attached to the heat-sensitive recording layer of the heat-sensitive film A, and removes dust to the glaze 66a. Adhesion and dust are prevented from adversely affecting image recording.
[0022]
In the recording apparatus 10 in the illustrated example, before the heat-sensitive film A is conveyed, the support member 68 is rotated upward (in the direction opposite to the direction of the arrow a), and the thermal head 66 (glaze 66 a) and the platen roller 60 are rotated. Not in contact with
When the conveyance by the above-described regulating roller pair 52 is started, the heat-sensitive film 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 film A is conveyed to a recording start position (a position corresponding to the glaze 66a), the support member 68 rotates in the direction of arrow a, and the heat-sensitive film A is moved to the glaze 66a of the thermal head 66 and the platen roller 60. , And the glaze 66a is pressed against the recording layer, and the heat-sensitive film A is held at a predetermined position by the platen roller 60, and is moved by the platen roller 60 (and the regulating roller pair 52 and the transport roller pair 63). It is transported in the b direction.
[0023]
Along with this conveyance, the heat-generating elements of the glaze 66a are heated according to the recorded image, so that the heat-sensitive image is recorded on the heat-sensitive film A.
Here, in the recording apparatus 10 of the present invention, the resistance correction of the thermal image recording is performed as follows.
[0024]
FIG. 3A is a schematic perspective view of the thermal head 66, and FIG. 3B is a block diagram of a recording control system of the thermal head 66.
As shown in FIG. 3, the recording control system of the thermal head 66 basically includes an image processing unit 80, an image memory 82, and a recording control unit 84. The image processing unit 80 is connected to a correction data storage unit 86 that stores a weighting function or a weighting table according to the thermal head temperature and the image data value (that is, the image density value) used for the resistance value correction.
[0025]
Image data from an image data source R such as CT or MRI is sent to the image processing unit 80.
The image processing unit 80 is a combination of an image processing circuit and a memory for performing the following various image processing, receives image data from the image data supply source R, and emphasizes the outline of the image on the image data. sharpness correction for (sharpening); thermal film gradation correction to obtain a proper image in accordance with the γ value and the like of a; temperature adjusting heating energy in accordance with the temperature of the heating element correction; glaze 66 a Shading correction to correct the density difference between the center and both ends; Resistance correction to correct the difference in resistance between each heating element; Image data corresponding to the same density at the same density regardless of the number of heating elements to be heated Performs predetermined image processing such as black ratio correction for color development, and performs formatting (enlargement / reduction, frame allocation) as necessary, And outputs the image memory 82 as a heat-sensitive recording image data corresponding to the recording.
[0026]
Here, as shown in FIG. 3, five notches 66d, 66d... Are formed in the fins of the heat sink 66c of the thermal head 66 in the illustrated example at a portion corresponding to the glaze 66a, and the heat sink in this portion is formed. A thermistor 88 is arranged at the base of 66c. Each thermistor 88 detects the temperature of the glaze 66a by measuring the temperature of the base of the heat sink 66c. In the illustrated example, the temperature of the glaze 66a is determined at five points (that is, the temperature of the heating element in this portion). ) Is detected.
[0027]
The result of the temperature detection by the thermistor 88 is sent to the image processing unit 80. The image processing unit 80 detects the temperature of each heating element (each pixel) by, for example, linear interpolation, and performs the above-described temperature correction according to the detected temperature. I do.
Further, in the recording apparatus 10 according to the present invention, the resistance is corrected by adjusting the coefficient according to the temperature of each heating element and the image data value.
[0028]
As described above, in a printing apparatus using a thermal head, the resistance value of the heating element varies with use, and this is one of the causes of density unevenness of a printed image. , The resistance value of each heating element is measured, and the resistance value is corrected in accordance with the resistance value to record an image. However, according to the study of the present inventor, the thermal image is also affected by the temperature of the thermal head, that is, the temperature of each heating element, and the density of the recorded image, that is, the image data value of the image to be recorded. In a conventional device for correcting the resistance value, it is not possible to sufficiently correct the density unevenness caused by the variation in the resistance value.
On the other hand, in the recording apparatus 10 of the present invention, the coefficient of the resistance value correction is adjusted according to the temperature of the heating element and the image data value of the recorded image obtained from the temperature detection result by the thermistor 88 described above.
[0029]
In the illustrated example, the resistance is corrected by adjusting the coefficient according to both the heating element temperature and the image data value as a preferable correspondence. However, the present invention is not limited to this. The resistance value may be corrected by adjusting the coefficient according to only one of the data values.
[0030]
In the recording apparatus 10, the resistance value correction is basically performed by transferring the resistance value correction data [R / Rm] from a previous image processing circuit (for example, a shading correction circuit or image data from an image data supply source R). The image data value (image density value) D is multiplied by (D × [R / Rm]).
In the resistance value correction data [R / Rm], R represents the resistance value of the heating element, and Rm represents the maximum resistance value of all the heating elements. That is, in the recording apparatus 10, the resistance value correction is performed based on the maximum resistance value Rm of each heating element of the thermal head 66.
In the recording apparatus 10, resistance value correction data, ie, [R / Rm], is calculated for each heating element and stored in the memory of the image processing unit 80. When the resistance value is corrected, the resistance of the corresponding heating element is calculated. The resistance value correction is performed by reading the value correction data and multiplying the read out value correction data by the image data value D.
[0031]
Here, in the recording apparatus 10 of the present invention, the resistance value correction is performed by adjusting (correcting) the coefficient to be multiplied by the resistance value correction data according to the temperature of the heating element and the image data value D of the recorded image.
As described above, the correction data storage unit 86 is connected to the image processing unit 80. The correction data storage unit 86 stores a weighting function (or a table corresponding thereto) for calculating a weight α according to the temperature of the thermal head 66 (heating element) as shown in FIG. 4B, a weighting function for calculating a weight β (D) corresponding to the image data value D of the recorded image is stored.
[0032]
The image processing unit 80 uses the function (table) shown in FIG. 4A stored in the correction data storage unit 86 together with the resistance value correction data at the time of resistance value correction, and detects the detected heating element. Is calculated (or read) according to the temperature of the image data, and further, according to the image data value D output from the image processing circuit before the resistance value correction, using the function shown in FIG. The weight β (D) is calculated, and the image data Da corrected by the following equation is calculated as a coefficient by which both weights are multiplied by the resistance correction data [R / Rm].
Da = D × (1-α × β (D) × (1- [R / Rm]))
[0033]
Therefore, according to the recording apparatus 10 of the present invention, it is possible to perform thermal image recording in which the temperature unevenness of the thermal head and the image data value are also compensated, and the density unevenness caused by the resistance value variation of each heating element is sufficiently corrected. High-quality images without density unevenness can be formed stably.
[0034]
The weighting function or table for obtaining the weights α and β may be appropriately determined according to the characteristics of the thermal head 66 to be used, the characteristics of the heat-sensitive film A, the device configuration (heating, cooling efficiency, and the like).
The correction data storage unit 86 may store the resistance value correction data.
[0035]
As described above, Rm of the resistance value correction data is the maximum resistance value among all the heating elements, and the resistance value correction is performed based on this.
Here, due to the manufacture of the thermal head, the end of the glaze 66a in the extending direction has a greater variation in the resistance value of the heating element than the center, and the end does not often correspond to a recorded image. The change in the resistance value of the heating element over time is large. Therefore, when the resistance value of this portion becomes the reference of the resistance value correction data, that is, Rm, the resistance value correction becomes unstable.
Therefore, in the recording apparatus 10 of the present invention, the maximum resistance value Rm, which is a reference of the resistance value correction data, is selected and set from a predetermined number of points at the end in the extending direction of the glaze 66a, for example, from the heating elements excluding 100 pixels. Preferably.
[0036]
There is no particular limitation on the number of heat generating elements at the end excluding the setting of the maximum resistance value Rm, and it may be appropriately determined according to the characteristics and size of the thermal head 66, the characteristics of the heat-sensitive film A, the format with the highest recording frequency, and the like. However, for example, in the case of a thermal head 66 (3072 pixels) having a maximum B4 size and a recording density of 300 dpi as described above, the maximum resistance value Rm may be set from among the values excluding about 100 pixels at both ends.
[0037]
The resistance value of each heating element is usually measured by measuring a current value or a voltage while all the heating elements of the thermal head are generating heat.
Therefore, in the recording apparatus 10 of the present invention, R / Rm of each heating element obtained by actual measurement is subjected to spatial frequency processing, and this is stored in the image processing unit 80 as resistance correction data [R / Rm]. Then, it is preferable to perform resistance value correction.
[0038]
The spatial frequency processing method is not particularly limited, and can be performed by, for example, a filtering process.
[0039]
As described above, the resistance value of each heating element changes over time as image recording is performed.
Therefore, in a preferred embodiment, the recording apparatus 10 of the present invention is configured to measure the resistance values of all the heating elements and update the resistance correction data [R / Rm] every time a predetermined number of recordings are performed. You.
There is no particular limitation on the method of measuring the resistance value of the heating element. A method of measuring a current value by applying a constant voltage, a method of measuring a voltage by supplying a constant current, and measuring a calorie by supplying a constant energy Various methods for measuring the resistance value of the heating element, such as a method for performing the heating, are exemplified. In the recording apparatus 10 in the illustrated example, for example, the method is performed by a method schematically illustrated in FIG.
[0040]
As shown in FIG. 5, in the recording apparatus 10, a constant current source 92 for measuring a resistance value and a resistance measurement signal generating section 94 are arranged in addition to the driving power supply 90 and the recording control section 84 described above.
The thermal head 66 is (the heating elements), the changeover switch SW ₁ connecting by switching the driving power source 90 or the constant current source 92 and the thermal head 66, a thermal head 66 recording controller 84 or the resistance measurement signal generator changeover switch SW ₂ to be connected are connected by switching between parts 94.
[0041]
In a normal state, the driving power supply 90 and the recording control unit 84 are connected to the thermal head 66. However, when an instruction to update the resistance value correction data is issued, a control unit (not shown) that controls the entire recording apparatus 10. ) by being switched over switch SW ₁ and the switching switch SW _2, as illustrated in FIG. 5, the thermal head 66 and the constant current source 92 and a resistance measuring signal generating portion 94 is connected.
In this state, by supplying a predetermined current from the constant current source 92 to the thermal head 66 and measuring the voltage of the thermal head 66, the resistance value of each heating element is measured.
The resistance value of each heating element is sent to the image processing unit 80 , and resistance value correction data is calculated from the maximum resistance value Rm and the resistance value R of each heating element as described above, and is stored in the image processing unit 80. Thus, the resistance value correction data is updated.
[0042]
The number of thermal recordings for updating the resistance correction data is not particularly limited, and may be appropriately set in accordance with the characteristics of the thermal head, a format with a high recording frequency, and the like. The number may be about 1,000 to 10,000. Further, a counter may be provided in the recording device 10 to automatically update the resistance value correction data, and the updating may be automatically performed every time a predetermined number of images are recorded. May be appropriately performed according to the conditions.
Alternatively, an operator or serviceman may determine the image quality of the recorded image, record a predetermined number of images at the time when it is determined that the resistance value correction data needs to be updated, and issue an update instruction.
[0043]
In the recording apparatus 10, as described above, the image data from the image data supply source R such as CT or MRI is sent to the image processing unit 80, where the image processing unit 80 performs sharpness correction, gradation correction, temperature correction, Predetermined image processing such as shading correction, resistance value correction, and black ratio correction described above is performed, and further, is formatted as necessary, and is converted into image data corresponding to the thermal recording by the thermal head 66. The image data is output from the image processing unit 80 and stored in the image memory 82.
The recording control unit 84 sequentially reads out the thermal recording image data stored in the image memory 82 line by line in the direction in which the glaze 66a extends, and records signals (voltage application according to the image) according to the read thermal recording image data. (Time width) is output to the thermal head 66.
Each heating element of the thermal head 66 generates heat according to the recording signal, and as described above, the thermal image recording is performed while the thermal film A is conveyed in the direction of the arrow b by the platen roller 60 or the like.
[0044]
The heat-sensitive film A on which the heat-sensitive image recording has been 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 unit 22. The tray 72 protrudes outside the recording device 10 through a discharge port 74 formed in the housing 28, and the heat-sensitive film A on which an image is recorded is discharged outside through the discharge port 74 and is taken out.
[0045]
As described above, the thermal recording apparatus of the present invention has been described in detail. However, the present invention is not limited to the above-described example, and various improvements and modifications may be made without departing from the scope of the present invention. It is.
[0046]
【The invention's effect】
As described above in detail, according to the thermal recording apparatus of the present invention, density unevenness caused by variation in the resistance value of each heating element of the thermal head can be sufficiently corrected by resistance value correction. High-quality images without unevenness can be stably formed.
[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. 3A is a schematic perspective view of a thermal head, and FIG. 3B is a block diagram of a recording control system of the thermal head.
FIGS. 4A and 4B are graphs showing weighting functions for resistance value correction.
FIG. 5 is a block diagram showing a method of measuring a resistance value.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 (Thermal) recording device 14 Loading part 16 Supplying and conveying means 20 Recording part 22 Discharging part 24 Magazine 26 Cover 28 Housing 30 Insertion opening 32 Guide plate 34 Guide roll 36 Stopping member 40 Suction cup 42 Transporting means 44 Transport guide 48 Endless belt 50 Nip roller 52 Restriction 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 Exit 76 Cooling fan 80 Image processing unit 82 Image memory 84 Recording control unit 86 Correction data storage unit 88 Thermistor 90 Drive power supply 92 Constant current source 94 Resistance measurement signal generator A Thermal (recording) film

Claims (3)

A thermal head having a glaze in which heating elements are arranged in one direction,
Means for contacting the glaze and the thermosensitive recording material, and relatively moving the thermal head and the thermosensitive recording material in a direction orthogonal to the arrangement direction of the heating elements;
An image processing unit that receives image data from an image data supply source, performs image processing including resistance value correction on the image data, and converts the image data into thermal recording image data;
Thermal head temperature measuring means,
Further, the image processing unit may calculate resistance value correction data set for each heating element according to each resistance value based on a maximum resistance value of the heating element excluding both ends in the extending direction of the grace. And a means for adjusting the correction coefficient of the resistance value correction in accordance with the temperature of the thermal head, the image data value of the recorded image, or both. Thermal recording device. 2. The thermal recording apparatus according to claim 1 , wherein the resistance value correction data is obtained by performing spatial frequency processing. 3. The thermal recording apparatus according to claim 1 , wherein the image processing unit updates the resistance value correction data every time a predetermined number of images are recorded.

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