JPH02136251A - Density gradation control type thermal printer - Google Patents

Abstract

PURPOSE:To simplify circuit constitution by eliminating complicated signal processing on the side of a substrate by respectively supplying a current to heating resistor elements by odd and even number groups in a time sharing manner corresponding to two non-simultaneous strobe signals by the control in a thermal line head. CONSTITUTION:In a thermal printer wherein a current is supplied to each of heating resistor elements for a current supply time being an integral multiple of a unit current supply time to control the density gradation of each pixel, strobe signal forming means 6, 8 imparting the first and second strobe signals ST1, ST2 for performing the supply of a current for a unit current supply time in a time sharing manner are provided at first. Further, the first current supply means A1, A3 - A511 for supplying a current only to odd number heating resistor elements in response to the first strobe signal ST1 and the second current supply means A2, A4 - A512 for supplying a current only to even number heating resistor elements in response to the second strobe signal ST2 are provided. By this method, a current is selectively supplied to each of the heating resistor elements only for a unit time.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a 1Q degree gradation control type thermal device in which the density gradation of each pixel is controlled by energizing each heating resistor element for an energization time that is an integral multiple of the unit energization time. Regarding printers. [Prior Art] In this type of printer, pixels on one print line are
A thermal line head is used in which a large number (for example, 512) of corresponding heating resistive elements are arranged in a line. During printing, these heating resistive elements are pressed against the recording paper directly (in the case of a direct thermal method) or indirectly through an ink ribbon (in the case of a thermal transfer method). Then, by selectively energizing each heating resistor element according to the image signal,
The color develops in dots on the recording paper, or is transferred from the ink ribbon to the recording paper in dots, and an image corresponding to one print line is recorded at one time. By repeating such a printing operation for, for example, 600 printing lines in the paper feeding direction, - images are recorded. By the way, if all of these large number of heating resistive elements are energized at the same time, the instantaneous power consumption becomes extremely large, placing a large burden on the power supply circuit. Therefore, initially, we divided the heat generating resistor element on the left half and the heat generating resistor element on the right half into blocks A and B, respectively, and energized each block in a time-sharing manner to reduce the maximum instantaneous power consumption. P is reduced to reduce the load on the power supply circuit. However, when electricity is applied to each block, there is a problem in that the recording density becomes thinner than the intended density at the block boundaries. This is because the degree of heat dissipation is large at the boundaries (ends) of the blocks, so even if the heating resistor there is energized for a predetermined period of time, the amount of heat actually given to the recording paper or ink ribbon is lower than the intended value. To become. Therefore, recently, the heating resistive elements are divided into odd-numbered ones and even-numbered ones, and each group is energized in a time-sharing manner. FIG. 5 shows a circuit configuration of a thermal line head used in such a thermal printer of the odd/even group energization method. FIG. 6 shows the timing of signals at each part of this thermal line head. In Fig. 5, a resistor R is connected between the output terminal of the inverting circuit N1-N512 and the power supply voltage terminal (+VB).
1 to R512 are heating resistance elements, respectively. Among these heating resistance elements, the odd number heating resistance elements R1 and R3
, R5, . . . R511 belong to the odd group, and even numbered heating resistive elements R2, R4, R6, . . ., R512 belong to the even group. In the energization cycle of unit energization time, first, the gradation data DATAO for the odd group is transferred to the shift register 10.
2 is input. At this time, each bit is serially input in synchronization with the clock CK (FIG. 6B). The bit structure of this gradation data DATAO is as shown in FIG. 7(A). That is, odd-numbered groups of heating resistive elements R1, R3, R5, . . . are placed in odd-numbered bit positions.
- Gradation bits dl, d3 . d5...d511 are placed, and bits with logical value "0" are placed in all even-numbered bit positions. The shift register 102 outputs this gradation data DATAO as parallel data. Immediately after that, the launch signal LA falls to "L" (Fig. 6C), and the gradation data D
ATAO is latched by the latch circuit 104, and each bit is applied to one input terminal of the analog gate (Al-A) 312. Next, a strobe signal ST that maintains the "H" level for a unit energization time ΔT is applied (FIG. 6D), and the analogue Al-A 312 is enabled. As a result, the heating resistive elements R1, R3...R511 of the odd-numbered group are selectively activated according to the information content of the gradation bits di, d3...d 511 (when the corresponding gradation bit is "1"). It generates heat by energizing it for a unit energizing time △T. On the other hand, even-numbered group heating resistance elements R2, R4...R
512 are not energized. During the period in which the odd-numbered groups are energized, the gradation data DATAE for the even-numbered groups is input to the shift register 102 (FIGS. 6A and 6B). The bit structure of this gradation data DATAE is as shown in Fig. 7 (B), in which all "0" bits are inserted in the odd numbered bit positions, and the even group heat generation is inserted in the even numbered bit positions. Resistance elements R2, R4, RG...R5!2
A gradation bit d having information (1 or "0") as to whether each of the above should be energized for a unit energization time.2.
d4゜d6...d512 are placed. This gradation data DATAE is converted into parallel data by the shift register 102, and latched by the latch circuit 104 after the energization of the odd-numbered groups is completed (FIG. 6C). Then, the strobe signal ST that maintains the "H" level for the unit energization time ΔT is applied again (FIG. 6D), and the AND gate Al-A312 is enabled, and the heating resistive elements R2, R4 of the even group ...R512 is gradation Bi,
7 d2. According to the information contents of d4...d512, electricity is selectively applied (when the corresponding gradation bit is "1") for a unit energization time ΔT to generate heat. However, in the odd number group, any of the heating resistance elements R1, R3...R51
1 does not turn on. In this way, the odd numbered (odd group) heating resistance elements R1, R3...R511 and the even numbered (even numbered group) heating resistance elements R2, R4... By alternately energizing and generating heat, the instantaneous maximum power consumption is halved and the load on the power supply circuit is reduced, and the heat dissipation characteristics of the entire heat-generating resistor element are achieved. The problem of thinning also disappears. [Problem to be Solved by the Invention] However, in the conventional thermal printer as described above, gradation data D in which a "0" bit is inserted in the gradation bit for the odd-numbered heating resistor element as shown in FIG.
ATAO and gradation data D A T' with “0” bits inserted in the gradation bits for even-numbered heating resistor elements.
AE had to be created on the board side outside the thermal line head, and the signal processing for this was complicated and required an expensive and complicated circuit. The present invention has been made in view of this problem, and it is possible to time-divisionally energize heating resistive elements by odd number Φ even number groups by controlling within the thermal line head without performing complicated signal processing on the board side. The purpose of the present invention is to provide a density gradation control type thermal printer. [Means for Solving the Problems] In order to achieve the above object, the present invention divides a plurality of heating resistive elements into a plurality of groups, which correspond one-to-one to a plurality of pixels on one printing line, and A 4-degree scale in which density gradation is given to each pixel by energizing each heating resistor element for each group in a time-sharing manner for an energizing time that is an integral multiple of the ψ position energizing time during a fixed energizing interval for the printing line. In a control type thermal printer, a strobe signal generating means time-divisionally provides a first strobe signal and a second strobe signal for energizing for a unit energizing time; a first energizing means for energizing only the resistive element;
The structure includes second energization enabling means for energizing only the even-numbered heating resistor elements in response to the second strobe signal. [Operation] In each unit energization cycle, when the first strobe signal is first applied, the first energization enabling means operates in response to this to enable energization of only the odd-numbered heating resistor elements. As a result, each of the odd-numbered heating resistance elements is
Signal corresponding to 2H degree of pixel recording, e.g. gradation level /)
The power is selectively energized for a unit energization time depending on the information content. During this period, since the second strobe signal has not yet been applied, the second energization enabling means does not work, and therefore none of the even-numbered heating resistive elements are energized. When the duration of the first strobe signal expires, the second strobe signal then
strobe signal is given. Then, the second energization enabling means operates to enable energization of only the odd-numbered heating resistance elements, and each of these heating resistance elements receives a signal (for example, a gradation bit) corresponding to the recording degree of the pixel. Electricity is selectively energized for a unit energization time according to the information content. On the other hand, since the first energization enabling means does not work in the odd-numbered heating resistance elements, no current is applied to any of the heating resistance elements. [Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 shows the circuit configuration of a thermal line head 1 according to this embodiment. The output terminal of the inverting circuit N1-N512 and the power supply voltage terminal (+
Heat-generating resistance elements R1 to R512 are connected between the terminals and VB). Input terminals of inverting circuits N1 to N512 are connected to output terminals of AND gates Al to A312, respectively. One input terminal of each AND gate is connected to each corresponding bit/node output terminal of the launch circuit 4, but the other output terminal differs between odd and even numbers. That is, the odd-numbered AND gate A1. The other input terminals of A3...A311 are connected to the first strobe input terminal 6, and the even-numbered AND gates A2...A311 are connected to the first strobe input terminal 6. A4...A312
The other input terminal of is connected to the second strobe input terminal 8. The latch circuit 4 has a capacity of 512 bits, and its 512 (bits) input terminals are connected to the 512 (bits) output terminals of the 7-foot register 2, respectively. The shift register 2 has a capacitance of 512 pins, inputs the gradation data DATA serially from the data input terminal 12, converts it to parallel data 17, and transfers it to the latch circuit 4 side.
It is designed to be output. Nao, clock input terminal 14 has bits of gradation data.
A clock CK with a frequency corresponding to the rate is applied, a latch signal LA for causing the launch circuit 4 to latch the output data of the soft register 2 is applied to the latch input terminal 10, and the first and second strobe terminals 6 ,8
are given first and second strobe signals STI and ST2 for energizing odd-numbered heating resistance elements and even-numbered heating resistance elements, respectively. These signals GK, LA, STI, and ST2 are all generated by a circuit on the substrate side, which will be described later. Next, the operation of this thermal line head will be explained with reference to FIGS. 2 and 3. At the beginning of each unit energization cycle, 512-bit gradation data DATA is applied to the data input terminal 12 (FIG. 2A).
). This gradation data DATA has a bit configuration as shown in FIG. That is, all of the 512 bits are composed of gradation bits CK Plj to CK P512j each having information (°°1” or “0”) as to whether or not the corresponding heating resistive element should be energized for a unit energizing time. When inputting this gradation data DATA, apply black and red CK to the clock input terminal 14 (FIG. 2B).
Synchronized with this clock, each gradation bit is serially set to 1.
After the gradation data DATA is input to the soft register 2, a "L" launch signal LA is given to the latch circuit 4, which causes the shift The parallel gradation data DATA from the register 2 is latched by the latch circuit 4, and each of the gradation data CK Plj-CK P5+2j is applied to one input terminal of the corresponding analog gates A1 to A312. Immediately after this, the first strobe signal STI (“H”
) is given. The duration (pulse width) of this signal is selected to be the unit energization time ΔT. This strobe signal S
Odd numbered anime game by TI) AI, A3...
- A311 (first energization enabling means) is enabled. On the other hand, the even numbered and date A2. A4...A3
12 (second energization enabling means) are both in a disabled state since the second strobe signal ST2 remains "L". As a result, when PIJ is "1" in an odd-numbered gradation bit, for example C, the output signal of the AND gate Al is "H", and therefore the output signal of the inverting circuit N+ is "L".
The heating resistance element R1 is energized and generates heat. This energization time is a unit energization time ΔT defined by the strobe signal ST1. However, when CK Plj is "O", the output signal of the AND gate A+ is "L", and therefore the output signal of the inverting circuit N1 is "I("), so the heating resistor element R1 is not energized and does not generate heat. Then, the other odd-numbered heating resistive elements are also selectively energized for a unit energizing time ΔT according to the contents of the corresponding gradation vias. However, in the even-numbered heating resistance elements R2, R4...R512, the even-numbered inverting circuits Ni, N3...N511
Since all of the output terminals are 41", none of the heating resistive elements generates heat. When the duration of the first strobe signal STI expires, the second strobe signal ST2 is immediately activated. (14H”)
is given (Fig. 2E). This strobe signal ST2
The duration (pulse width) of is also selected as the unit energization time Δ'r. Therefore, this time, this strobe signal ST2
The even-numbered AND gate A2. A4...A
312 is enabled, and even-numbered heating resistive elements R2, R
4... R512 corresponds to each gray scale bit CK
P2J, CK P4J... According to the contents of CKP512j, electricity is selectively energized for a unit energization time △T to generate heat. However, even-numbered heating resistance elements R1, R3...
・In R511, odd-numbered AND gate Al,
Since A3...A311 are all in a disabled state, all output terminals of the inverting circuits NLN3...N511 are at "1", so none of the heat generating resistor elements is energized and generates heat. In this way, this thermal line head can process gradation data D in which gradation bits are placed at all bit positions as shown in FIG.
ATA is input, and the odd-numbered heating resistance elements and the even-numbered heating resistance elements in the hend are divided and energized for each unit energization time ΔT in a time division manner. Therefore, on the board side, there is no need to create grayscale data for odd-numbered heating resistor elements and grayscale data for even-numbered heating resistive elements separately, which simplifies signal processing and simplifies circuit configuration. . FIG. 4 shows the overall configuration of a one-degree gradation control type thermal printer according to the present embodiment. Circuits other than the above-mentioned thermal line node 10 are provided on the substrate side. First, tone data DATA (C
K Plj-CK P512j) is generated as follows. A digital video signal DV is input to the frame memory 20 as pixel data. Each row of the frame memory 20 corresponds to a horizontal scanning line of a television image, and pixel data is written in an order corresponding to rask scanning. Next, starting from the first column of the frame memory 20, one line of pixel data a[1a2L......a 51
2j is read. These pixel data are once taken into the line buffer 24 and then input to the color processing circuit 28, where they are subjected to image processing such as inverse gamma correction and then converted into 8-bit density data blj,
b2j. ......converted to b512j. These 1
Each of the degree data, for example

0] (minimum concentration) ~ [6
4] It has a value (gradation level) according to the density of the corresponding pixel within the range of (twice the maximum). Density data for one printing line generated by the color process circuit 28 blJ, b2j, . . .
b 512j is supplied to a LUT (look-up table) 30 for 1 degree - energization time conversion, where each 1 degree data bnJ indicates the energization time <N) corresponding to the gradation level [N]. For example, it is converted into 8-bit energization time data Bnj. Current application time data Blj for one printing line generated from the LUT 30. B2'', . . . B512j are taken into the line buffer 34 and provided from there to the data comparison circuit 38. The data comparison circuit 38 is given an 8-bit comparison standard (MCP) whose value is incremented by one from (1) to (64) at regular intervals during the energization interval from the gradation counter 40. , this comparison reference value CP is compared with each energization time data, and when the latter is equal to or larger than the former, a "1" bit (gradation bit) is generated. For example, energization time data B Ij, B 2j...
・The values of B 512j are <10>, <1>, etc., respectively.
...Assume that <2). In this case, in the first comparison, the comparison reference value CP is (1), and the first
gradation data [CI Plj, CI P2J,...
...CIP512j becomes [1, 1, ... 1]. In the second comparison, the comparison reference value CP is (2), and the second tone data [C2Plj, C
2P2j. ...C2P512J is [:1. O,...1]
becomes. In the third comparison, the comparison standard value CP is (
3), the third gradation data [C3Plj, C3P2j
,...C3P512j is ci, o, ...0
Becomes Ko. In this way, 64 comparisons are performed during the energization interval, and 64 (pieces) of gradation data [CI PIJ, CI P2j. ...CI P512j] ~ [CG4PIj, CG
4P2j,...CB4P512J] are continuously transferred serially to the thermal line to the shift register 2 of node 1.
supplied to Therefore, in the thermal line head 1, the heat generating resistive elements R1, R2...R512 are selectively energized for a unit energizing time △T according to the information content of the corresponding gradation bit to generate heat. do. Then, by repeating such energization operation for the gradation data 64 times (K=1 to 64), energization is performed for a cumulative time length equivalent to 64 times the unit energization time ΔT at maximum, and one One of 64 density gradation levels is given to each pixel on the print line. The DMA controllers 22, 26.36 each have a frame memory 20.36. Controls write and read operations of line buffers 24.34. The CPU 50 controls each section via the DMA controllers 22, 28, and 36. Then, in synchronization with the gradation counter 40, the clock circuit 16 generates a clock CK, and the latch strobe circuit 18 (
The strobe signal generating means) is the first strobe signal generating means. Second strobe signal ST1. ST2 and a launch signal LA are generated. [Effects of the Invention] By having the above-described configuration, the present invention provides the following effects. In response to two non-simultaneous strobe signals, the odd-numbered heating resistance elements and the even-numbered heating resistance elements are enabled to be energized sequentially for each unit energization time, so that the odd-numbered and even-numbered heating resistance elements in the thermal line head are It is possible to perform time-division energization. Therefore, on the board side,
There is no need to create grayscale data for odd-numbered heating resistive elements and grayscale data for even-numbered heating resistive elements separately, which simplifies signal processing and requires a simple circuit configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the circuit configuration of a thermal line head according to an embodiment of the present invention, FIG. 2 is a timing chart of signals of each part to explain the operation of the thermal line head of the embodiment, and FIG. 4 is a diagram showing the bit configuration of gradation data supplied to the thermal line head of the embodiment, FIG. 4 is a block diagram showing the overall configuration of a density gradation control type thermal printer according to an embodiment of the present invention, Fig. 5 is a block diagram showing the circuit configuration of a thermal line head used in a conventional density gradation control type thermal printer. Fig. 6 is a timing diagram of signals of each part to explain the operation of the conventional thermal line head. , FIG. 7 is a diagram showing the bit configuration of gradation data supplied to a conventional thermal line head. In the drawings, 1... thermal line head, 2... shift register, 4... latch circuit, 6... first strobe input terminal, 8... second
Strobe input terminal, 10... Launch input terminal, 12... Data input terminal, 18... Latch strobe circuit, 40... Gradation counter, 50... CPU1 Rl~ R512...Heating resistance element, N1-N512
...Inverting circuit, Al-A312...And gate.

Claims (1)

[Scope of Claims] A plurality of heat generating resistive elements corresponding one-to-one to a plurality of pixels on one printing line are divided into a plurality of groups, and each group is divided into a plurality of groups in a time-sharing manner during a fixed energization interval for the printing line. Separately, in a density gradation control type thermal printer in which density gradation is given to each pixel by energizing each heating resistor element for a energizing time that is an integral multiple of the unit energizing time, in order to cause energization to occur for the unit energizing time. strobe signal generation means for time-divisionally providing first and second strobe signals; and first energization enabling means for enabling energization of only odd-numbered heat generating resistor elements in response to the first strobe signal. A density gradation control type thermal printer comprising: a second energization enabling means for energizing only even-numbered heating resistor elements in response to the second strobe signal.