JPH02169267A - Thermal recording system - Google Patents

Abstract

PURPOSE:To perform the recording of an intermediate-tone sharp image by applying data to a thermal head for each bit unit and at the same time, applying a strobe signal with a pulse width corresponding to bits. CONSTITUTION:After preheating, image data is entered in a head control circuit 16 and the image data entered in the head control circuit 16 is allowed to undergo data conversion. Then the most significant bits are entered in the data input terminal 4 of a thermal head 20. The image data after conversion is written in a shift register 6. Next, a latching signal LT2 is applied to the terminal 3 of the thermal head 20 from the head control circuit 16, and data in the shift register is shifted to a latching circuit 7. Then the data is entered in an input terminate at one of AND gates and a strobe width in compliance with the current printing bit data and head temperature is determined by a value stored in ROM 17 using the head control circuit 16. Finally voltage is applied to a heat generating element.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thermal recording method that enables halftone image recording on a recording medium (for example, plain paper, thermal paper, processed paper, OHP sheet, etc.). It is something.

[Prior Art] Conventionally, for example, a multi-tone thermal transfer recording device that implements a multi-tone thermal transfer recording method that enables half-tone recording, such as a printer device that performs printing with a thermal head, has not been able to control print density thermally. This is done by controlling the energy supplied to the head, that is, the head voltage, the energization time, etc.

[Problems to be Solved by the Invention] However, in the conventional multi-gradation thermal transfer recording system, when printing for N gradations, the number of heating elements in the head, that is,
For example, if the image data is 6 bits, the data is transferred 64 times, and if the image data is 8 bits, the data is transferred 4 times, 256 times. However, there is a problem in that there is a limit to the printing time and it is not possible to shorten the printing time any further.

In addition, when recording high-definition images, the number of bits of image data increases, which not only increases the recording time but also increases the number of parallel-to-serial conversion circuits that convert image data into head drive data, which is input to the thermal head. There was a problem in that the circuit configuration for generating the signal became complicated.

As a method of shortening the recording time, for example, Japanese Patent Application Laid-open No. 57
The one disclosed in Japanese Patent No.-57682 is known.

This is based on the basic principle of transferring image gradation data bit by bit, which reduces the number of data transfers and shortens data transfer time, but does not energize the heating element continuously. Therefore, even if the current is energized for the energizing time corresponding to the number of gradations, the heat dissipation of the heating element during the period when the current is not energized will cause data with a large number of gradations to be smaller than data with a smaller number of gradations. There was a possibility that the print density would become lighter.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal recording method which solves the above-mentioned problems, prevents reversal of image density during recording, and enables good halftone image recording.

[Means for Solving the Problems] In order to achieve such an object, the present invention converts image data into head drive data in a thermal recording method for recording an image on a recording medium, and converts image data into head drive data. Bit-slicing the data and applying the sliced bits to the thermal head bit by bit,
By applying a strobe signal with a pulse width corresponding to the sliced bits, halftone recording is possible depending on the pulse width of the strobe signal applied to the recording head and the number of times a serial data string is applied to the recording head. It is characterized by:

[Function] In the present invention, image data is converted into head drive data,
The converted head drive data is bit sliced, and the sliced bits are applied to the thermal head on a bit-by-bit basis, as well as a strobe signal having a pulse width corresponding to the sliced bits.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the invention.

In the figure, 17 is a ROM, which converts the binary number "00" into a data bit roll, and the binary number "01J".
In the case of data bit '0IOJ, the binary number is "10"
In the case of data bit rlol, the binary number is "11"
In this case, a table for converting data bits to rill is stored, and data for determining the strobe width is also stored, and is divided into a predetermined number of tables for each head temperature and printing ink color. Table 1 shows the correspondence between binary numbers and data bits. L and S are head control circuits, and RO! Convert digital image data to head drive data based on the table stored in if 17,
The heating element is driven based on the converted head drive data. The image data is obtained by A/D converting video No. 43, and is manually inputted to the head control circuit 16 via a terminal 15 from a rice memory (not shown). 21 is a thermistor, and 19 is a temperature detection circuit, which detects the temperature of the thermal head 20. 18 is the system controller (
CPU) controls the head control circuit 16 and 1101, 117 based on the detected temperature. Note that 22 is a RAM, which is used as a work area for the system controller 18 and a buffer area for temporarily storing data. Further, 20 is a thermal head, the configuration of which is shown in FIG.

In FIG. 2, reference numeral 6 denotes a shift register, which converts serial data D^ inputted via a terminal 5 into parallel data in synchronization with a clock signal CL inputted via a terminal 4. Reference numeral 7 denotes a data latch circuit which latches the no-polar signal of the shift register 6 in synchronization with a latch signal LT input manually via the terminal 3.

, A1-A312 are AND gates which output the data signal of the data latch circuit 7 for a time corresponding to the pulse width of the strobe signal ST inputted via the inverter 9. ■, ~T, 12 are transistors, and heating elements R1 ~ R5 according to the pulse from AND gate ~A312
12.

Table 1 FIG. 3 shows a flowchart of an example of a control procedure by the system controller 18.

FIG. 4 shows an example of timing when printing gradation "50". Here, it is assumed that all one line of image data 15 input to the head control circuit 16 is r50.

First, in order to raise the temperature of the heating elements 81 to 8s, 2 of the thermal head 20 to the coloring temperature of the ink sheet (in case of thermal transfer recording method) or thermal paper (in case of /!5 thermal recording method), Perform preheating.

That is, the head control circuit 16 outputs dummy data "1".
" is transferred to the data input terminal 5 of the thermal head 20 as data D^1, and the transferred data DAI is written to the shift register 6 in synchronization with the clock CLKI for 512 bits. After writing, the data is transferred to the input terminal 3 of the thermal head 20. 51 of the latch circuit 7.
Write "1" to all 2 bits. Then, a strobe pulse STI having a width necessary to raise the heating element to the coloring temperature is applied to the input terminal 2 of the thermal head to perform preheating.

After preheating, the thermal head 20
In order to eliminate uneven printing, image data is manually inputted to the head control circuit 16 in step 51, and in step S2,
The image data 15 input manually to the head control circuit 16 is converted into data, and the upper bits are input to the data input terminal 4 of the thermal head 20. Here, in step S3, the image data after conversion is set to 9 bits. First, step S
At step 4, the value "1" of hit 8, which is the upper hit, is inputted to data input terminal 5 of thermal head 20 as data D, and written into shift register 6. and,
512 to shift register 6 by clock CLK2
After inputting the bit data concave 2, in step 55,
A latch signal LT2 is applied from the head control circuit 6 to the terminal 3 of the thermal head 20, and the latch signal LT2 is applied to the terminal 512 in the shift register.
The bit data is passed to the latch circuit 7 and latched. Next, in step S6, the data latched by the latch circuit 7 is converted to data D by AND gate 8,~^51.
The head control circuit 16 determines the strobe width according to the current print bit data and head temperature based on the value stored in the ROM 17, and applies it as data ST2. Also, the data ST2 is passed through the inverter 9 to the AND gates ^1 to A3.
12 and connect it to the other input terminal of transistor T1.
- T512 is set to 01 and voltage is applied to the heating elements R1 to R512. Note that at this time, the strobe width of the strobe signal ST2 is approximately 28 times the pulse width required to color the ink or thermal paper by one tone of density.

After applying voltage to the heating elements R1 to R6, 2, step S
7, and in step S8, N becomes "0".
” or not. In this case, since N is not "O", the process returns to step S4 and the procedures from step S54 to step S8 are performed.

Then, bit 6 of the image data, etc.
The procedure from step 54 to step S8 is repeated for bit O.

In this case, a strobe signal ST3 is applied to the thermal head 20 corresponding to each bit data OA3 to DAIII.
~STIO is approximately 27.26.2% of the strobe width required to develop color for one gradation, respectively, z4.
23.22.2+, with 2° times the pulse width.

Next, a data conversion method in this embodiment will be explained.

The 6-bit image data is divided into three blocks of 2 bits each, and data conversion is performed for each block according to the conversion rules shown in Table 1. Figure 4 shows the gradation level “50”.
” An example of the timing when printing is shown.

That is, the 6-bit data of 50 (110010,1) is converted to 9-bit data of 462 (111001110a), and the same processing as the head drive described above is performed on this 9-bit data.The strobe width corresponding to each bit at this time is is the number of conversion bits obtained by adding a weight α to the pulse #IAN necessary for producing 64 gradations of color.For example, the strobe width corresponding to bit 0 of 9 bits of conversion data is (N+α). )/29.

In this way, instead of driving the head for each gradation,
By converting the bits of image data to prevent image deterioration and driving the head so as to express gradations in units of bits, printing time can be shortened and the hardware configuration can be simplified.

In this embodiment, image data is sequentially applied to the thermal head starting from the most significant bit.
Similar effects can be obtained by sequentially applying the signals starting from the least significant bit of the image data.

In the above-mentioned embodiments, the thermal transfer recording method and the heat-sensitive recording method have been described as examples, but the present invention is not limited thereto. For example, an image may be recorded on a recording medium by ejecting ink liquid. It can also be applied to inkjet recording methods and the like.

[Effects of the Invention] As explained above, according to the present invention, since it is configured as described above, it is possible to prevent the image density from reversing during image recording.
It is possible to provide a thermal recording method that can perform halftone image recording satisfactorily.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing a multi-gradation thermal transfer recording apparatus implementing a multi-gradation thermal transfer recording method according to an embodiment of the present invention, and Fig. 2 is a configuration of the thermal head shown in Fig. 1. FIG. 3 is a flowchart showing the control procedure by the system controller 18, and FIG. 4 is a timing chart showing an example of the timing when printing in 50 gradations. 6...Shift register, 7...Latch circuit, 1...Head control circuit, 17...ROM. 19... Temperature detection circuit, 20... Thermal head, 21... Thermistor, R3-R5, 2... Heating element, T1-T, 12... Transistor. Ne1 Figure 1; Showing f Therma heart, 7F20/) structure Neo figure Figure 2 F Reheat change's 1 Raisode P Tegagawa page - 4-Flow 1 in 1000th figure

Claims (1)

[Claims] 1) In a thermal recording method that records an image on a recording medium,
A strobe that converts image data into head drive data, slices the converted head drive data, applies the sliced bits to the thermal head in bit units, and has a pulse width corresponding to the sliced bits. A thermal recording method that enables halftone recording according to the pulse width of a strobe signal applied to a recording head by applying a signal and the number of times a serial data string is applied to the recording head. .