JPH1044490A - Device and method for heat sensitive image recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a black ratio irregularity according to passage of time by measuring the voltage of a power source device and the voltage to be supplied to a thermal head, calculating a resistance value therebetween from the measured voltages, and renewing the correction coefficient based on the resistance value so as to correct the black ratio of image data. SOLUTION: In an image processing part 80, the resistance value between a power source device 86 and a thermal head 66 from the voltage of the power source device 86 inputted from a voltage measuring device 90 and the voltage to be supplied to the thermal head. According to the resistance value, the correction coefficient is renewed so as to conduct the black ratio correction of image data corresponding to each picture element. After being applied with various kinds of image processing including the black ratio correction at the image processing portion 80, the image data are temporarily stored in a memory 82. According to the voltage supplied from the power source device 86, each heat generating element comprising a glaze of the thermal head 66 is controlled based on the image data stored in the image memory 82 by a recording controlling part 84.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal image recording apparatus for forming a recorded image corresponding to image data on a thermal recording material using a thermal head and a recording method therefor. The present invention relates to a thermal image recording apparatus and a recording method capable of forming a recorded image without black ratio unevenness (density unevenness) by correcting the black ratio of the image.

[0002]

2. Description of the Related Art Thermal 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 paper, film or the like as a support is used for recording an ultrasonic diagnostic image. . In addition, thermal image recording has advantages such as elimination of wet development processing and simplicity of handling. In recent years, not only small-sized image recording such as ultrasonic diagnosis but also MRI diagnosis and X-ray For applications requiring large and high-quality images, such as diagnostics, the use of these in image recording for medical diagnosis is also being studied.

As is well known, a thermal image recording apparatus (hereinafter, referred to as a thermal image recording apparatus)
In a thermal recording apparatus), a thermal head having a glaze in which heating elements corresponding to the number of pixels in one line are arranged in one direction is used, and the glaze is slightly pressed against a thermal recording layer of a thermal material. By heating each of the glaze heating elements according to the image data of the recorded image while relatively moving both of them in a direction substantially orthogonal to the arrangement direction of the heating elements, the heat-sensitive recording layer of the heat-sensitive material is heated to form an image. We are recording.

The individual heating elements constituting the glaze are resistance elements. The thermal head has, for example, a configuration in which a plurality of resistance elements are connected in parallel between a power supply and a ground via respective switching elements. have. Then, for example, the image data value of each pixel is subjected to pulse width or pulse number modulation, and the corresponding heating element is energized for a time corresponding to the width or number of the modulated pulse, thereby setting each heating element to a predetermined temperature. Is causing fever.

[0005] By the way, a voltage dropped according to the amount of current is supplied to the thermal head by an internal resistance of a power cable from a power supply device to the thermal head. For example, when there is a large amount of low-density image data in one line of image data, the number of heating elements that are simultaneously energized is small, so that the amount of current flowing through the thermal head is small and the amount of voltage drop is small. Conversely, when there is a large amount of high-density image data, the amount of current flowing through the thermal head is large, and the amount of voltage drop increases.

Therefore, the voltage supplied to the thermal head varies for each line and further for each pixel in accordance with the density (image data value) of the recorded image. Even if the pulse width or pulse number modulation is performed according to the data, and the heating element is energized for a time corresponding to the modulated pulse width or number to generate heat, a difference occurs in the generated heat energy, Even if the image data values are the same, there is a problem that a density difference occurs in the recorded image, that is, so-called black ratio unevenness occurs.

In order to solve this problem, in a conventional thermal recording apparatus, it is assumed that the internal resistance of a power cable is substantially invariable, and based on the resistance of the power cable, individual image data is determined. Black ratio correction was performed. However, as shown in FIG.
The contact resistance of the connector 92a for connecting the power cable 6 to the power cable 88 and the connector 92b for connecting the power cable 88 to the thermal head 66 change over time, for example, increase by several tens mΩ over time.

For example, in the thermal head 66 to which a voltage of 15 V is supplied, the contact resistance value of the connectors 92a and 92b is changed from 10 mΩ to 15 mΩ over time by 5 m.
It is assumed that Ω has increased. Although a current of 20 to 30 A may momentarily flow through the thermal head 66, here,
For example, if a current of 20 A flows through the thermal head 66, a voltage change of 0.1 V occurs, and the voltage supplied to the thermal head 66 is 15V-0.1V.
= 14.9V.

As described above, in the conventional thermal recording apparatus, the contact resistance values of the connectors 92a and 92b change with time, and the voltage supplied to the thermal head 66 changes accordingly. In particular, heat energy is two times the voltage
Because it changes in proportion to the power, the fluctuation of the supplied voltage greatly affects the recorded image, and even if the black ratio correction is performed on the image data based on the resistance value of the power cable, it will not change over time. There was a problem that the black ratio unevenness would recur.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal image recording apparatus and a recording method capable of preventing the occurrence of unevenness in the black ratio due to aging, in view of the problems of the prior art. Is to do.

[0011]

To achieve the above object, the present invention relates to a thermal image recording apparatus for forming a recorded image corresponding to image data on a thermal recording material using a thermal head, comprising a power supply unit. And a voltage measuring device for measuring a voltage supplied to the thermal head, and a resistance value between the power supply device and the thermal head is calculated from the measured voltage, based on the calculated resistance value. And an image processing unit for performing a black ratio correction on the image data by using the updated correction coefficient, thereby providing a thermal image recording apparatus.

The present invention also relates to a thermal image recording method for forming a recorded image corresponding to image data on a thermal recording material using a thermal head, wherein a voltage of a power supply device and a voltage supplied to the thermal head are controlled. Measuring, calculating a resistance value between the power supply device and the thermal head from the measured voltage, updating a correction coefficient based on the calculated resistance value, and using the updated correction coefficient Another object of the present invention is to provide a thermal image recording method characterized by performing black ratio correction on image data.

Here, it is preferable that a current of 10 mA or more is applied to the thermal head to measure the voltage, and it is further preferable that the current be 100 mA or more. Further, it is preferable that the correction coefficient is changed in proportion to the resistance value, and it is further preferable that the correction coefficient is changed using a conversion table indicating a relationship with the resistance value. Preferably, a warning is issued when the resistance value is equal to or more than a predetermined value, and the warning is such that a voltage drop due to a resistance between the power supply and the thermal head exceeds 5% of a voltage of the power supply. It is preferably emitted when

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic view of an embodiment of a thermal image recording apparatus according to the present invention. The illustrated thermal image recording apparatus (hereinafter, referred to as a thermal recording apparatus) 10 performs thermal image recording on a thermal recording material of a predetermined size such as a thermal recording film A of B4 size (hereinafter, referred to as thermal film A). The loading unit 14, the supply and transport unit 16, the recording unit 20,
The discharge unit 22 includes a power supply unit 23 (not shown) (see FIG. 2).

The heat-sensitive film A is formed by forming a heat-sensitive recording layer on one surface of a transparent film such as a transparent polyethylene terephthalate (PET) film as a support. Body (bundle)
Is stored in the magazine 24, and the magazine 2 is stored one by one.
4 and used for thermal image recording.

The loading section 14 is provided in the housing 2 of the thermal recording apparatus 10.
8, guide plate 32, guide roll 3 formed in 8
4, 34 and a stop member 36. The magazine 24 is inserted into the insertion opening 3 of the loading section 14 with the lid 26 side first.
0 to the inside of the thermal recording apparatus 10 and the guide plate 32
While being guided by the guide rolls 34, 34, the thermal recording device 10 is pushed down to a position where it contacts the stop member 36.
At a predetermined position.

The supply and transport section 16 takes out the thermal film A from the magazine 24 loaded in the loading section 14 and transports the thermal film A to the recording section 20, and uses a sucker 40 that sucks the thermal film A by suction. It has a leaf mechanism, a transport 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 conveying rollers 46,
A pulley 47a coaxial with the transport roller 46, a pulley 47b connected to a rotary drive source, a tension pulley 47c,
Endless belt 4 stretched over these three pulleys
8. It has a nip roller 50 pressed by the transport roller 46 and the like.

The recording section 20 has a thermal head 66, a platen roller 60, a cooling fan 76 for cooling the thermal head 66, a cleaning roller pair 56, a guide 58, a guide 62, a transport roller pair 63, and the like.

In the illustrated example, the thermal head 66
For example, a thermal head body which performs thermal image recording at a recording (pixel) density of 300 dpi, and has a glaze in which heating elements for performing thermal recording for one line are arranged in one direction on a thermal film A; A heat sink fixed to the thermal head body. 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 film A at a predetermined position, and conveys the heat-sensitive film A in a direction substantially perpendicular to the glaze extending direction. The cleaning roller pair 56 is a roller pair including an adhesive rubber roller and a normal roller.

The power supply section 23 supplies power of a predetermined voltage to the loading section 14, the supply / transport section 16, the recording section 20, the discharge section 22, and the like. Here, FIG. 2 shows a conceptual diagram of the power supply unit 23 of the thermal recording apparatus of the present invention. The power supply unit 23 shown in the figure shows the relationship between the thermal head 66 and the power supply, and includes a power supply 86, a power cable 8
8 and a voltage measuring device 90.

In this embodiment, the power supply 86 supplies, for example, a voltage of 15 V to the thermal head 66. The power supply 86 and the thermal head 66 are connected to each other by connectors 92a and 92b by a power cable 88. Connected. The voltage measuring device 90 includes a power supply 86
And a voltage supplied to the thermal head 66. The voltage measuring device 90, the power supply device 86, and the thermal head 66 are respectively connected to the auxiliary connector 94.
a, 94b.

In the voltage measuring device 90, a connector 92
Since the voltage is measured via the auxiliary connectors 94a and 94b instead of the terminals a and 92b, almost no current flows through the voltage measuring device 90, and the voltage of the power supply 86 and the voltage supplied to the thermal head 66 are accurately measured. Can be measured. The voltage is measured, for example, every time a predetermined number of thermal image recordings are performed, at predetermined time intervals, or in the thermal recording apparatus 10.
It is performed periodically and automatically, such as at the time of startup.

The thermal recording apparatus of the present invention is basically like this. Next, the operation of the thermal recording apparatus will be described.

In the thermal recording apparatus 10, when recording is instructed, the lid 26 of the magazine 24 is opened by an opening / closing mechanism (not shown), and the thermal film is transferred from the magazine 24 by the sheet-feeding mechanism using the suction cup 40. A is taken out, and the leading end of the thermal film A is supplied between the transport roller 46 of the transport means 42 and the nip roller 50. When the heat-sensitive film A is nipped between the transport roller 46 and the nip roller 50, suction by the suction cup 40 is released,
The supplied thermal film A is transported along the transport guide 44.

When the heat-sensitive film A to be used for recording is completely discharged from the magazine 24, the lid 26 is closed by the opening / closing means. The distance from the 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 film A in the conveyance 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 stops here.

The leading end of the heat-sensitive film A is a pair of regulating rollers 52.
Is reached, the temperature of the thermal head 66 is confirmed. If the temperature of the thermal head 66 is a predetermined temperature, the conveyance of the heat-sensitive film A by the regulating roller pair 52 is started, and the heat-sensitive film A is conveyed to the recording unit 20. Is done.

Before the thermal film A is conveyed, the support member 68 is rotated upward (in the direction opposite to the direction of arrow a), and the glaze of the thermal head 66 and the platen roller 6 are rotated.
No contact with 0. When the conveyance is started by the above-described regulating roller pair 52, the heat-sensitive film A is then nipped by the cleaning roller pair 56, and further the guide 58
It is conveyed while being guided by.

When the leading end of the heat-sensitive film A is conveyed to the recording start position (the position corresponding to the glaze), the supporting member 68
Is rotated in the direction of arrow a, the thermal film A is sandwiched between the glaze of the thermal head 66 and the platen roller 60, and the glaze is pressed against the recording layer. Next, the heat-sensitive film A is transported by the platen roller 60, the pair of regulating rollers 52, the pair of transport rollers 63, and the like while being held at a predetermined position by the platen roller 60.

During this conveyance, each of the glaze heating elements is heated in accordance with the recorded image, so that the heat-sensitive film A
The thermal image recording is performed. The thermal film A on which the thermal image recording has been completed is transported by the platen roller 60 and the transport roller pair 63 while being guided by the guide 62,
The sheet is discharged to the tray 72 of the discharge section 22. The tray 72 is
Thermal recording device 1 through discharge port 74 formed in housing 28
The heat-sensitive film A, which protrudes to the outside and has an image recorded thereon, is discharged to the outside through the discharge port 74 and is taken out.

The thermal recording apparatus 10 basically operates in this manner. Next, the thermal image recording method of the present invention will be described.

First, FIG. 3 shows a conceptual diagram of an embodiment of the power supply section. In the figure, a power supply unit 23a includes a power supply device 8
6, a power cable 88 and a voltage measuring device 90, and the power supply 86 and the thermal head 66 are connected to the power cable 8
8 are connected via connectors 92a and 92b, respectively. Also, a voltage measuring device 90 and a power supply 86
And the thermal head 66 are connected via auxiliary connectors 94a and 94b, respectively.
Is supplied with a control signal from the voltage measuring device 90.

In the thermal image recording method of the present invention, a control signal is output from the voltage measuring device 90 to the thermal head 66 so that a predetermined constant current I corresponding to the voltage supplied from the power supply 86 is applied to the thermal head. The voltage V1 of the power supply 86 and the voltage V2 supplied to the thermal head 66 are measured by a voltage measuring device 90. The voltage measured by the voltage measuring device 90 is input to an image processing unit described later.

The measurement of the voltages V1 and V2 is performed periodically and automatically, for example, every time a predetermined number of thermal images are recorded, at a predetermined time, or every time the thermal recording apparatus 10 is started up. Shall be. In addition, the amount of current flowing through the thermal head 66 is preferably 10 mA or more, and more preferably 100 mA or more, in order to accurately measure the voltage of the power supply 86 and the voltage supplied to the thermal head 66. .

Next, FIG. 4 is a block diagram of an embodiment showing a processing system for image data. As shown in the figure, the image data is subjected to various image processing including black ratio correction in an image processing unit 80 and then temporarily stored in an image memory 8.
2 is stored. Then, the recording control unit 84 controls the image memory 84 according to the voltage supplied from the power supply device 86.
Thermal head 6 based on the image data stored in
The heat generation of the individual heating elements constituting the glaze of No. 6 is controlled.

Here, an example of a calculation formula used for correcting the black ratio of the image data of each pixel in the image processing section 80 will be described.

[0039]

(Equation 1)

In the above equation (1), N is the number of pixels in one line, D is the image data value, and M is the maximum image data value. K is a correction coefficient, D
(N) is an image data value of the pixel n before correction, H (D) is a correction data value for the image data value D, and D _C (n) is an image data value of the pixel n after black ratio correction.

In the above formula (1), first, a correction data value H (D) for each image data value D is calculated. For example, in an apparatus in which the range of the image data value D is 2048 gradations from 0 to 2047, the corresponding correction data values H (0) to H (2047) are calculated for 2048 correction data values. .

At this time, the image data value D (n) before correction
Is greater than or equal to the image data value D, D ′ (n) is the image data value D. Conversely, if the image data value D (n) is smaller than the image data value D, D ′ (n) n) is an image data value D (n). Then, the correction data value H corresponding to the image data value D (n) before correction of each pixel n
By using (D (n)), the corrected image data value D
_C (n) is calculated.

In the image processing section 80, the voltage measuring device 9
From the voltage V1 of the power supply 86 input from 0 and the voltage V2 supplied to the thermal head 66, the calculation formula R =
Using (V1−V2) / I, a resistance value R between the power supply device 86 and the thermal head 66 is calculated. Then, the correction coefficient k of the above equation (1) is updated according to the resistance value R, and the black ratio of the image data corresponding to each pixel is corrected using the above equation (1).

The correction coefficient k is updated, for example, in proportion to the resistance value R, or the value of the correction coefficient k corresponding to the resistance value R is held in advance as a conversion table, and this conversion table is used. It is preferable to update.

In addition, the change amount of the resistance value R (R1−R2) is too large, so that the density unevenness of the recorded image due to the black ratio unevenness cannot be properly corrected according to the thermal image recording method of the present invention, for example. In some cases, it is preferable to issue a warning without performing correction using the above calculation formula. As a guide for issuing a warning, for example, the thermal head 6
It is preferable that when the maximum current flows through 6, the voltage drop due to the resistance value R exceeds 5% of the voltage.

The thermal image recording method of the present invention is basically as described above. The black ratio correction applied to the thermal image recording apparatus and recording method of the present invention is applicable to an image recording apparatus that modulates image data using pulse width modulation or pulse number modulation. In addition, the present invention is not limited to the above-described embodiment, and various improvements and changes may be made without departing from the spirit of the present invention.

[0047]

As described above in detail, the thermal image recording apparatus and recording method of the present invention can be used periodically and automatically.
The resistance value between the power supply device and the thermal head is calculated, and the correction coefficient of the black ratio correction is updated based on the resistance value,
The black ratio correction is performed on each image data. Therefore, according to the thermal image recording apparatus of the present invention, it is possible to always provide a high quality recorded image without deterioration of the quality of the recorded image due to unevenness of the black ratio over time.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of one embodiment of a thermal image recording apparatus of the present invention.

FIG. 2 is a conceptual diagram of a power supply unit of the thermal image recording apparatus of the present invention.

FIG. 3 is a conceptual diagram of an embodiment of a power supply unit of the thermal image recording apparatus of the present invention.

FIG. 4 is a block diagram of a processing system for image data of the thermal image recording apparatus of the present invention.

FIG. 5 is a conceptual diagram of a power supply unit of the thermal image recording apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thermal image recording apparatus 14 Loading part 16 Supply / conveyance part 20 Recording part 22 Ejection part 23 Power supply part 24 Magazine 26 Cover 28 Housing 30 Insertion port 32 Guide plate 34 Guide roll 36 Stop member 40 Sucker 42 Conveyance means 44 Conveyance guide 46 Conveyance Rollers 47a, 47b pulley 47c tension pulley 48 endless belt 50 nip roller 52 regulating roller pair 56 cleaning roller pair 56a adhesive rubber roller 56b roller 58, 62 guide 60 platen roller 63 transport roller pair 66 thermal head 68 support member 68a fulcrum 72 tray 74 discharge port 76 cooling fan 80 image processing unit 82 image memory 84 recording control unit 86 power supply unit 88 power supply cable 90 voltage measuring device 92a, 92b connector 94a, 94b auxiliary connector A Thermal recording film

Claims (8)

[Claims] 1. A thermal image recording apparatus for forming a recorded image corresponding to image data on a thermal recording material using a thermal head, comprising: a voltage measuring device for measuring a voltage of a power supply device and a voltage supplied to the thermal head. Device, the resistance value between the power supply device and the thermal head is calculated from the measured voltage, a correction coefficient is updated based on the calculated resistance value, and the updated correction coefficient is used. An image processing unit for performing a black ratio correction on the image data. 2. A thermal image recording method for forming a recorded image corresponding to image data on a thermal recording material using a thermal head, comprising: measuring a voltage of a power supply device and a voltage supplied to the thermal head; From the measured voltage, a resistance value between the power supply device and the thermal head is calculated, a correction coefficient is updated based on the calculated resistance value, and the image data is updated using the updated correction coefficient. A thermal image recording method, wherein black ratio correction is performed using 3. The thermal image recording method according to claim 2, wherein the voltage is measured by applying a current of 10 mA or more to the thermal head. 4. The method according to claim 3, wherein the current is 100 mA or more.
2. The thermal image recording method described in 1. above. 5. The thermal image recording method according to claim 2, wherein the correction coefficient is changed in proportion to the resistance value. 6. The thermal image recording method according to claim 2, wherein the correction coefficient is changed using a conversion table indicating a relationship with the resistance value. 7. The thermal image recording method according to claim 2, wherein a warning is issued when the resistance value is equal to or more than a predetermined value. 8. The thermal image recording method according to claim 7, wherein the warning is issued when a voltage drop due to a resistance between the power supply and the thermal head exceeds 5% of a voltage of the power supply. .