JPH10278331A - Thermal recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recording a high quality thermal image stably using a thermal recording data subjected to appropriate image processing by reducing whitened false outline being produced through sharpness correction significantly in a thermal recorder employing a thermal head. SOLUTION: An image data from an image data source is subjected to gradation correction to produce a record data indicative of energy being applied to a thermal head. The record data is subjected to at least sharpness correction before an image is recorded on a thermal recording material by means of a thermal head. The record data subjected to sharpness correction and having a value smaller than kE0 , i.e., a record data value E0 corresponding to an image data value 0 multiplied by a constant k (k<1), is entirely converted to kE0 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art An image recording using a heat-sensitive recording material (hereinafter, referred to as a heat-sensitive material) in which a heat-sensitive recording layer is formed using a film or the like as a support for recording an ultrasonic diagnostic image (hereinafter referred to as a heat-sensitive image recording). Is used. In addition, thermal image recording has advantages such as no necessity of wet development processing and easy handling. In recent years, not only small-sized image recording such as ultrasonic diagnosis but also CT diagnosis,
For applications requiring large and high-quality images, such as RI diagnosis and X-ray diagnosis, 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, in which a thermal recording layer of a thermal material is heated to record an image. While slightly pressing the (thermosensitive recording layer), both are relatively moved in a direction perpendicular to the glaze extending direction, energy is applied to each heating element of the glaze, and heating is performed according to a recorded image. Thereby, the image recording is performed by heating the heat-sensitive recording layer of the heat-sensitive material.

[0004]

In such a thermal recording apparatus, image data is received from an image data supply source such as a CT diagnostic apparatus or an MRI diagnostic apparatus, and the image processing apparatus performs sharpness correction or the like on the image data. By performing predetermined image processing (correction) such as gradation correction to obtain thermal recording image data corresponding to the thermal recording, the thermal head is driven in accordance with the thermal recording image data to generate heat from each heating element, thereby forming an image. A thermal image corresponding to the image data supplied from the data supply source is recorded.

Here, the image processing performed by the image processing device of the thermal recording apparatus includes, specifically, sharpness correction (sharpness processing) for enhancing the outline of an image; Tone correction for obtaining an appropriate image corresponding to individual differences of the recording device; temperature rise correction for adjusting heat generation energy in accordance with the temperature of the heating element; density unevenness caused by glaze variations in the thermal head, etc. Shading correction; resistance value correction for correcting the difference in resistance between each heating element; image data corresponding to the same density at the same density regardless of changes in the thermal head power supply voltage drop due to changes in the recording pattern. Black ratio correction;

[0006] Among them, the sharpness correction enhances the sharpness of an image, particularly a high-definition halftone image, by enhancing the outline of the image in order to obtain a sharp image with high image quality and sharpness. Things. That is, in the thermal recording device,
When recording an image on a thermosensitive material with a thermal head,
Compared to recording an image on a photosensitive material with laser light, there is basically blurring of the image due to heat diffusion.In order to compensate for the blurring of the image due to the heat, the degree of sharpness enhancement is increased by image processing. Thus, a high-quality image is obtained.

On the other hand, in the gradation correction, the temperature difference between the respective heating elements during recording and the temperature distribution of the entire thermal head are reduced to perform high-quality thermal recording.
Even when the recording density is 0 (that is, the value of the image data input from the image data source is 0), a predetermined amount of recording energy is applied so that the heat-sensitive material A does not develop color (preferably immediately before coloring). Recording data value E ₀ (E ₀ >
0).

Therefore, when the sharpness correction is performed after the gradation correction, as shown in FIG. 4A, the density of the outline or the like changes sharply in one line in the main scanning direction of the image to be recorded. If there is a portion (hereinafter, referred to as an edge portion), after the sharpness correction, as shown in FIG.
In some cases, the density difference at the edge portion is emphasized and the peak value D _LP of the print data on the low density side becomes considerably smaller than E ₀ . For this reason, in the actual recorded image, even if the emphasized edge portion is alleviated due to the diffusion of heat at the edge portion, a non-colored portion remains without being sufficiently colored at a portion where color should be originally formed. As a result, a false contour may be generated in which the contour looks white, and a problem may occur in which a recorded image may feel uncomfortable.

The occurrence of false contours in a recorded image has been a serious problem when high-quality image recording is required, particularly when a high-definition halftone image is recorded. In particular, in applications where high-definition, high-quality halftone images are required, such as in the aforementioned medical applications, it becomes an obstacle to image observation,
It was a serious problem that led to medical mistakes.

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, recording is performed while greatly reducing false contours which may be lost due to sharpness correction. An object of the present invention is to stably record a high-quality thermal image by appropriately expressing thermal processing image data (hereinafter, referred to as recording data) by vividly expressing an outline in an image.

[0011]

In order to achieve the above object, a thermal recording method according to the present invention is applied to a thermal head obtained by performing a gradation correction process on image data input from an image data source. Record data that represents the energy
When at least a sharpness correction process is performed and an image is recorded on a thermosensitive recording material by a thermal head, a constant k (k) is added to a print data value E ₀ corresponding to an image data value 0 among print data after the sharpness correction process. Value kE multiplied by <1)
All recorded data of a value smaller than ₀ to provide a thermal recording method characterized by converting the kE _0.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thermal recording method 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 of the present invention utilizing the thermal recording method of the present invention. FIG.
Is a thermosensitive recording device 10 (hereinafter, referred to as a recording device 10) that performs thermal image recording on a thermosensitive recording material (hereinafter, referred to as a thermosensitive material A) which is a cut sheet of a predetermined size such as a B4 size. The loading unit 14 into which the magazine 24 containing the heat-sensitive material A is loaded,
6. It has a recording unit 20 for recording a thermal image on the thermal material A by the thermal head 66, and a discharge unit 22. As shown in FIG. 2, an image processing unit 80 and a recording control unit 84 are connected to the thermal head 66 of the recording unit 20, and a data storage unit 86 is connected to the image processing unit 80.

In such a recording apparatus 10, the heat-sensitive material A is conveyed to the recording unit 20 by the supply / conveyance unit 16, and the thermal head 66 is pressed against the heat-sensitive material A while the glaze extends in the direction in which the glaze extends (see FIGS. The thermosensitive material A is conveyed in a direction perpendicular to the paper surface (in the direction perpendicular to the plane of FIG. 2), and heat-generating elements are heated in accordance with the recorded image, thereby performing thermosensitive image recording on the thermosensitive material A.

The heat-sensitive material A is obtained by forming a heat-sensitive recording layer on one surface of a support such as a film such as a transparent polyethylene terephthalate (PET) film or paper. 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 of the magazine 24 one by one and provided for thermal image 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 the guide rolls 34, 34, and the stop member 36, and 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 supply / transportation means 16 takes out the heat-sensitive material A from the magazine 24 loaded in the loading section 14 and transports the heat-sensitive material A to the recording section 20, and uses a sucker 40 for sucking the heat-sensitive material A by suction. It has a mechanism, a transporting means 42, a transporting guide 44, and a pair of regulating rollers 52 located at an outlet of the transporting guide 44. The conveying means 42 includes a conveying roller 46, a pulley 47a coaxial with the conveying roller 46,
It has a pulley 47b and a tension pulley 47c connected to a rotary drive source, an endless belt 48 stretched over these three pulleys, and a nip roller 50 pressed by a transport roller 46. The heat-sensitive material A is conveyed by holding the tip of the leafed heat-sensitive material A between the conveyance roller 46 and the nip roller 50.

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-feeding mechanism using the suction cup 40 takes out one heat-sensitive material A from the magazine 24, and The leading end of A is supplied to the conveying means 42 (conveying roller 46 and 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 and regulated by the conveyance means 42 to the regulating roller pair 52.
Transported to 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 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 material A in the conveying 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,
The cleaning roller pair 56, the guide 58, a cooling fan 76 (see FIG. 1) for cooling the thermal head 66 and the guide 62, and the image processing unit 8 constituting a recording control system
0 and a recording control unit 84. Thermal head 66
Is, for example, capable of recording images up to a maximum of B4 size.
A thermal image recording apparatus capable of performing thermal image recording at a recording (pixel) density of about 300 dpi, in which heating elements for performing thermal recording on the thermal material A are arranged in one direction (perpendicular to the paper surface in FIGS. 1 and 2). It has a thermal head main body 66b on which the thermal head 66a is formed, and a heat sink 66c fixed to the thermal head main 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 platen roller 60 rotates at a predetermined image recording speed while holding the heat-sensitive material A at a predetermined position, and conveys the heat-sensitive material A in a direction perpendicular to the main scanning direction (the direction of arrow b in FIG. 2). . 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 recording apparatus 10 shown in the drawing, before the heat-sensitive material A is conveyed, the support member 68 is rotated upward (in the direction opposite to the direction of the arrow a), and is moved with 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). With this conveyance, each heating element of the glaze 66a is heated according to the recorded image, so that the heat-sensitive material A
The thermal image recording is performed.

As described above, the recording control system of the thermal head 66 basically includes the image processing section 80 and the recording control section 84. The image processing unit 80 is connected to a data storage unit 86 that stores data for various types of image processing (correction) performed by the image processing unit 80 and image data supplied from the image data supply source R. Is done. Further, the portion corresponding to the glaze of the base 66d of the heat sink 66c of the illustrated thermal head 66 includes:
Thermistors are arranged at predetermined intervals, for example, at five places, detect the temperature of the glaze 66a (that is, the temperature of the heating element in this portion), and, as indicated by the two-dot chain line, convert the detection result into an image processing unit. Send to 80. The image processing unit 80 receives the detection result, and detects the temperature of each heating element by, for example, linear interpolation. A thermometer T for detecting an ambient temperature near the thermal head 66 is provided in the recording unit 20, and sends a measurement result to the image processing unit 80.

Image data from an image data source R such as CT or MRI is sent to the image processing unit 80 as, for example, 10-bit (0 to 1023) digital data. The image processing unit 80 is a combination of various image processing circuits and memories. The image processing unit 80 receives image data from the image data supply source R, and sharpens the image data to enhance the outline of the thermosensitive recording image. Correction processing (sharpness processing),
In addition to the false contour reduction processing, which is a feature of the present invention, the gamma value of the thermosensitive material and the gradation correction for obtaining an appropriate image corresponding to the thermosensitive recording apparatus, especially the thermal head, etc., and the temperature of the heating element of the thermal head Temperature correction to adjust the heat generation energy according to the temperature, shading correction to correct the density unevenness caused by the shape variation in the longitudinal direction of the glaze of the thermal head, resistance correction to correct the difference between the resistance values of each heating element, recording pattern Irrespective of the change in the thermal head power supply voltage drop amount due to the change, predetermined image processing (correction) such as black ratio correction is performed so that image data corresponding to the same density is colored at the same density. (Enlargement / reduction, frame allocation) to obtain recording data corresponding to the thermal recording by the thermal head 66.

Here, in the thermal recording method of the present invention,
The order of these corrections is not particularly limited as long as the sharpness correction processing and the false contour reduction processing are performed at least after the gradation correction, and the other correction orders are not particularly limited. Gradation correction refers to the state of the recording apparatus and the γ of the heat-sensitive material A.
This is a correction for correcting the image data according to the value or the like and obtaining an image in which the gradation is appropriately expressed. As described above, the recording device 10 is a device that receives image data as 10-bit digital data and performs image recording in accordance with the digital data.
If the image data corresponds to a density (D) of 1.2,
When receiving 512 image data, it is basically required to output an image having a density of 1.2. However, there are individual differences in devices, and the installation environment and the like are also different.
Further, the γ value of the heat-sensitive material A also differs depending on the maker or the production lot. Therefore, it is impossible for all devices to output an image of a predetermined density according to the supplied image data. Therefore, gradation correction is performed to form a thermal recording image in which gradation is appropriately expressed according to image data. In a normal thermal recording apparatus including the recording apparatus 10 in the illustrated example, the image data sent from the image data supply source R is converted into recording data corresponding to the heat value of the thermal recording by this gradation correction. You.

The method of gradation correction is not particularly limited, and various known methods can be used.
To create a correction chart in which images of a plurality of densities are recorded, and measure the densities of the images recorded in the correction charts with a densitometer.
A method of creating a correction table, that is, a gradation curve (or a correction function) from an image density recorded in a correction chart using a density correction algorithm and converting image data into print data using the correction table is exemplified. You.

The recording data converted by the gradation correction so as to correspond to the amount of heat generated has a recording energy of such a degree that the heat-sensitive material A does not develop color (preferably immediately before coloring) even if the recording density is 0. Is supplied to the thermal head 66, the correction table is created as described above. In addition,
As described above, the value of the recording data corresponding to the recording energy in this case is E ₀ . With such a configuration, it is possible to reduce the temperature difference between the respective heating elements during recording, to reduce the temperature distribution of the entire thermal head 66, to obtain a high-quality image, and to use the base material of the heat-sensitive material A. Is a transparent PET film or the like, the surface of the heat-sensitive material A can be slightly melted to reduce diffuse reflection of light, and the transparency of the heat-sensitive material A can be improved.

The recording data obtained by the gradation correction is further subjected to a sharpness correction. The sharpness correction (sharpness processing) is a correction for enhancing the sharpness of an image by enhancing the outline of a recorded image in order to obtain a clear and sharp image. Various known methods can be used for the sharpness correction. For example, the sharpness correction is performed as follows. One screen is divided into n × n pixels, and the j-th _print data in the extending direction of the glaze 66a in a certain pixel line i is represented by S _ij (i = 1, 2,..., N, j = 1, 2,.
Assuming that n), in the sharpness correction, the recording data S _ij is first converted into a ^first unsharpness signal U ¹ _ij which is electrically blurred recording data. The first unsharpness signal U ¹ _ij is obtained by averaging the image data S _ij and the surrounding recording data.

(Equation 1) Is required. Note that M is the first unsharpness signal U
A number of pixels or mask size used to create a ¹ _ij, L is defined by (M-1) / 2.

Next, the first unsharpness signal U ¹ _ij
Are further averaged to obtain a second unsharpness signal U ² _ij
Is calculated. The second unsharpness signal U ² _ij is
Like the unsharpness signal U ¹ _ij , it is calculated by the following equation (2).

(Equation 2)

Next, the first unsharpness signal U ¹ _ij
And the second unsharpness signal U ² _ij . Then, the difference is multiplied by the sharpness correction coefficient K and the first unsharpness signal U ¹ _ij is added, that is, the recording data S _ij corrected for sharpness is obtained by the following equation (3). . S _ij = U ¹ _ij + K · (U ¹ _ij −U ² _ij ) (3)

Here, the sharpness of the thermal recording image is affected by the temperature of the thermal head 66 (heating element), the recording speed, the γ value of the thermal material A, and the like. The earlier, the lower the γ value of the heat-sensitive material A, the lower the sharpness of the recorded image becomes. Therefore, if necessary, the sharpness correction coefficient K may be changed accordingly to perform the sharpness correction. . In this case, for example, a table (or function) of a weighting coefficient corresponding to the temperature of the heating element, the recording speed, the γ value of the heat-sensitive material, or the like is created and read out at the time of the sharpness correction to perform the sharpness correction. A method of multiplying the coefficient K is exemplified.

Here, as described above, after the gradation correction,
When performing the sharpness correction, the recording data D after the gradation correction
The recording data value E corresponding to the image data value 0₀(> 0)
Is corrected based on the reference. For this reason, FIG.
As shown in (a) to (c), the image to be recorded
If there is an edge in the image, sharpening
The density difference at the edge is emphasized, and the recording data
Data value D_LIs E₀Or E ₀If the value is close to
Record data value D on low density side_LPeak value D of_LP
Is E₀May be much smaller than the actual record
Due to the thermal diffusion of the edges in the image, this enhanced
Even if the edge is relaxed, the color is not sufficiently developed
False contours appear as if the edge part is white.
Problem that the recorded image seems uncomfortable
sell.

On the other hand, in the present invention, the recording data D having been subjected to the sharpness correction as described above is subjected to a process of converting the recording data D smaller than a predetermined value into a predetermined value. Specifically, of the recording data D after the sharpness correction, the recording data value E ₀ corresponding to the image data value 0 is set to a constant k (k <
By converting all the recording data D smaller than the value kE ₀ multiplied by 1) to kE ₀ , the occurrence of false contour is prevented.

FIG. 3 is a schematic diagram showing an example of a conversion process according to the image recording method of the present invention. FIG. 3A shows an example of print data in the main scanning direction after gradation correction and before sharpness correction, and FIG. 3B shows print data immediately after the print data of FIG. FIG. 3C shows an example of (b)
5 is an example of recording data after the false contour reduction processing of the present invention has been applied to the recording data of FIG. FIG. 3D is an example of a thermal recording image formed based on the pattern of the recording data in FIG.

Hereinafter, an example of the thermal recording method of the present invention will be described with reference to FIG. First, assume that tone correction is performed on image data input from an image data source, and a pattern of print data D in the main scanning direction as shown in FIG. 3A is obtained. Here, at the center of the pattern of the print data D in FIG. 3A, there is an edge portion where the print data value (that is, density) changes rapidly.

Next, when the above-described sharpness correction is performed on a series of recording data D having such an edge portion, as shown in FIG. The pattern of D is obtained. That is, the image data value D _L of the low-density side of the vicinity of the edge portion (small end of the image data value) is converted highlighted into smaller peak value D _LP, the peak downward (low concentration direction) in the edge portion formed Is done. On the other hand, the image data value _DH on the high density side (the side with the larger image data value) near the edge portion is emphasized and converted into a larger peak value _DHP , and a peak is formed upward (high density direction) at the edge portion. Is done. Here, if the data of FIG. 3B is to be recorded by the thermal head as it is, as shown in FIG. 4C, the low-density-side peak portion (that is, the edge portion) also dissipates heat. Regardless, as described above, there is a case where no color is generated, a white outline appears, and a false contour is generated.

For this reason, in the present invention, the following conversion is performed on the image data D after the sharpness enhancement processing, and the minimum value of the recording data value D is set to kE ₀ , as shown in FIG.
As shown in FIG. 3C, the recording data after the sharpness correction is prevented from becoming an unnecessarily small value, and the heat is diffused at the edge portion in the actual recorded image, as shown in FIG. 3D. As described above, it is possible to express the contour vividly without causing a false contour.

[0038]

(Equation 3)

This conversion is performed on all image data. _Dm is the maximum value of the recording data and may be determined as appropriate. Here, as the value of k,
It is preferably 0.5 to 0.9, more preferably 0.6 to 0.7, but may be appropriately determined according to the performance of the thermal head to be used, the characteristics of the heat-sensitive recording material, and the like. Not limited. If it is less than 0.5, false contours may not be sufficiently removed, and if it is more than 0.9, the sharpness may not be sufficiently improved, and a sufficiently high image quality may not be obtained. Not preferred.

As described above, the image data is supplied from the image data source R such as CT or MRI, and the image processing unit 80 performs the temperature correction in addition to the gradation correction, the sharpness correction, and the false contour reduction processing of the present invention. Image processing such as shading correction, resistance value correction, and black ratio correction is performed, and the thermal recording data according to the thermal recording by the thermal head 66, which is formatted as necessary, is stored in the data storage unit 8.
6 is stored. The recording control unit 84 includes a data storage unit 86
The thermal recording image data is sequentially read out one line at a time in the longitudinal direction of the glaze 66a of the thermal head 66, and a recording signal (voltage application time width corresponding to the image in pulse width modulation) corresponding to the read thermal recording image data is thermally read. Output to the head 66.

The heating resistor 90 provided for each pixel of the thermal head 66 generates heat in accordance with the recording signal. As described above, while the heat-sensitive material A is conveyed by the platen roller 60 or the like in the direction of the arrow b, Thermal image recording is performed. The heat-sensitive material A on which the heat-sensitive image recording has been completed is guided by the guide 62 while the platen roller 60 and the conveying roller pair 63 are being transferred.
And is discharged to the tray 72 of the discharge unit 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 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 modifications may be made without departing from the gist of the present invention. Of course.

[0043]

As described above in detail, according to the present invention, in thermal recording using a thermal head, false contours, which are whitened out due to sharpness enhancement processing, are greatly reduced while the recorded image is reproduced. The outline can be vividly expressed. Therefore, a high-quality thermal image can be stably recorded by the thermal recording image data that has been appropriately image-processed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of a thermal recording apparatus for performing a thermal recording method of the present invention.

FIG. 2 is a conceptual diagram of one embodiment of a recording unit of the thermal recording apparatus shown in FIG.

FIG. 3 is a schematic diagram illustrating an example of a conversion process according to the thermal recording method of the present invention. (A) is an example of print data in the main scanning direction after gradation correction and before sharpness correction, (b)
(A) is an example of the recording data immediately after performing the sharpness correction on the recording data of (a), (c) is an example of the recording data after performing the false contour reduction processing of the present invention on the recording data of (b), ( d)
FIG. 9C is an example of a thermal recording image formed based on the pattern of the recording data in FIG.

FIG. 4 is a schematic diagram showing an example of a conversion process by a conventional thermal recording method. (A) is an example of print data in the main scanning direction after gradation correction and before sharpness correction, (b) is an example of print data immediately after sharpness correction is performed on the print data of (a), (c) () Is an example of a thermal recording image formed based on the pattern of the recording data of (b).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 (Thermal image) recording device 14 Loading part 16 Supplying and conveying means 20 Recording part 22 Discharge part 24 Magazine 26 Lid 28 Housing 30 Insertion opening 32 Guide plate 34 Guide roll 36 Stopping member 40 Sucker 42 Transporting means 44 Transporting guide 48 Endless belt Reference Signs List 50 nip roller 52 regulating 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 80 image processing section 84 recording control section 86 data storage section

Claims (1)

[Claims] An image data input from an image data source is subjected to gradation correction processing, and at least sharpness correction processing is performed on recording data representing energy to be applied to a thermal head. When recording an image on a recording material, of the recording data after the sharpness correction processing, the recording data value E ₀ corresponding to the image data value 0 is smaller than a value kE ₀ obtained by multiplying the recording data value E ₀ by a constant k (k <1). All recorded data of value k
Thermal recording method characterized by converting the E _0.