JPS62105649A - Printer - Google Patents

Abstract

PURPOSE:To simply correct accurately temperature over the entire halftone area even at any temperatture by varying a correcting curve itself in response to the variation when the environmental temperature of a thermal head rises or falls to alter the relation of density for a recording pulse width. CONSTITUTION:Pulse generating means 2 for applying a record pulse to head driving means 2 for applying power to the heating element of a thermal head 4, A/D converting means 6 for A/D-converting the output of temperature detecting means 5 for detecting the temperature of the head 4, and input/output characteristic converting means 1 provided on one ROM 12 or RAM 13 with the relation of the recording pulse width for an input gradation data at a plurality of temperature of the head 4 are provided. When the gradation data and the output of the means 6 are applied to the address of the converting means to cause the environmental temperature of the head 4 to rise or fall to vary the relation curve itself is varied in response to the variation. Accordingly the temperature correction of the head can be performed inexpensively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to temperature correction of the recording characteristics of a printer device that performs halftone recording using a thermal head.
It can be widely applied to RT hard copy devices and the like.

Conventional technology A thermal printer that performs halftone recording has a thermal head that integrates multiple heating elements, and by selectively energizing each heating element to generate heat, it prints on thermal paper or from thermal transfer paper to an image receptor. It records images, etc., and halftone recording is performed by controlling the recording pulse width and changing the effective energy, but since the relationship between recording pulse width and recording density is nonlinear, faithful halftone recording is performed. In order to
It is necessary to perform a correction generally called γ correction.

Furthermore, since the recording density when using a thermal head depends on the environmental temperature, correction based on the environmental temperature is also required.

Conventionally, γ correction and environmental temperature correction are performed independently, or ROM table groups for γ correction at multiple environmental temperatures are provided and the output of the ROM table group is selected depending on the environmental temperature (Japanese Patent Laid-Open Publication No. No. 68-164375) has been proposed.

FIG. 4 is a block diagram of a conventional example. The environmental temperature is divided into n levels, and n ROM tables 21 are created for each level.
A ROM table group 21 is composed of 1, 212, . . . 2In. 24 is a temperature sensor that detects the environmental temperature of the thermal head; 23 is an A/D converter that converts the output voltage of the temperature sensor 24 into a digital signal; 22
is R corresponding to the environmental temperature indicated by the output of the A/D converter 23.
OM table to each ROM table 211 212...
. . . This is a table selection circuit that selects and outputs from the output of 2In. In each ROM table, the relationship between the gradation level and the pulse width for energizing the thermal head in order to obtain the recording density corresponding to the gradation level is set at the environmental temperature. A tone level signal is input as an address.

Therefore, when the gradation level signal a is input, each ROM
γ-corrected recording pulse width data for each environmental temperature is output from the table, and based on the environmental temperature data b detected by the temperature detector 24, the table selection circuit selects each of the aforementioned ROMs.
Gamma correction and correction based on the environmental temperature were performed by selecting an output corresponding to the environmental temperature from the output of the table.

Problems to be Solved by the Invention In the conventional example, the outputs of a plurality of ROM tables corresponding to the environmental temperature of thermal and de were selected by the table selection means, but when attempting to perform highly accurate temperature correction, In addition to increasing the number of bits in the A/D converter (RO
It is also necessary to increase the number of M. Furthermore, selection means are also required. This is disadvantageous in terms of circuit scale, cost, etc., especially when the number of elements in one table is small and the number of environmental temperature levels is large.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a thermal head, a head driving means for applying electric power to a heating element of the thermal head, and a pulse for applying recording pulses to the head driving means. A generating means, a temperature detecting means for detecting the temperature of the thermal head, and an output of the temperature detecting means.
and an input/output characteristic converting means that sets in one ROM or one RAM the relationship of the recording pulse width with respect to the input gradation data at a plurality of temperatures of the thermal head. By applying the gradation data and the output of the A/D conversion means to the address of the input/output characteristic conversion means, temperature correction of the thermal head can be performed at low cost.

Function: When the environmental temperature of the thermal head rises or falls and the relationship between the recording density and the recording pulse width changes, the correction curve itself is changed in accordance with the change.
Accurate temperature correction of the thermal head can be performed at low cost over the entire halftone range at any temperature.

Example Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the printer device of the present invention.

1 stores a table of γ correction data for correcting the nonlinearity of the density level corresponding to the input gradation level with respect to the recording pulse width at a certain environmental temperature into one ROM or RAM in the number corresponding to the environmental temperature level. The set input/output characteristic converting means; 2 is a pulse generating means for generating a recording pulse according to the pulse width data output by the input/output characteristic converting means 1; 3 is a head driving means for driving each heating element of the thermal head 4; 6 is a temperature detection means for detecting the environmental temperature of the base of the thermal head or the like and generating a voltage; 6 is an A/D converter for converting the output voltage of the temperature detection means 6 into a digital value; and 7 is for the head drive means 3. This is a power supply that applies voltage to drive each heating element of the thermal head 4.

For example, if the gradation level signal is n bits and the accuracy of environmental temperature correction is m bits, then T correction data that corrects the nonlinearity with respect to the recording pulse width of the density level corresponding to the input gradation level at a certain environmental temperature is The address input of the written table will be n bits. The input/output characteristic converting means 1 has two such γ correction tables prepared according to each temperature level and written in ROM or RAM.
Alternatively, the RAM only needs to have an address of n-J-m bits.

Therefore, when m-bit input gradation level data a is input from an external device or a signal processing section at the front stage of the printer device, a is applied to the lower address of the input/output characteristic conversion means 1. Also, the environmental temperature of the thermal head at that time is measured by the temperature detection means 5, and the output voltage is measured by the A/
The n-bit environmental temperature level data b A/D-converted by the D conversion means e is applied to the upper address of the input/output characteristic conversion means 1. At this time, the input/output characteristic conversion means 1 outputs pulse width data necessary to record a density level corresponding to an input gradation level at an environmental temperature of 1,000 degrees.

When the environmental temperature changes, b given to the upper address of the input/output characteristic converting means 1 changes, so the γ correction table becomes a different temperature one, and temperature-compensated pulse width data can be obtained.

In other words, the input/output characteristic conversion means 1 of the present invention is a two-dimensional dople of input gradation level and environmental temperature, and the ROM
Alternatively, the addresses applied to the RAM are the same regardless of whether a or b is higher-order.

FIG. 2 is a block diagram of another embodiment of the printer device of the present invention.

10 is a CPU 11. ROM12, first RAM13
, second RAM14. First FORTlrs.

It is an input/output conversion means using a microcomputer, which is composed of a second PORT 1s and a third FORT 17, where C is an address bus and d is a data bus.

2 to 7 are similar to the above-mentioned embodiment, 2 is a pulse generating means that generates a recording pulse according to pulse width data, 3 is a head driving means that drives each heating element of the thermal head 4, and 5 is an environmental temperature. temperature detection means that detects and generates voltage;
6 is an A/D converter that converts the output voltage of the temperature detection means 5 into a digital value, and 7 is a power source that drives the head.

Next, the operation of this embodiment will be explained.

The CPU 11 of the microcomputer 10 described above is RO
The first R is set by the program written in M12.
It uses AM13 as a stack and work area to execute instructions. As shown in the flowchart in Figure 3, the CPU
11 creates a two-dimensional γ correction table f corresponding to each temperature level in the second RAM 14 based on the information set and stored in the ROM 12, and then processes each pixel in the following sequence. and record the image.

First, gradation level data input from another device or from a pixel data preprocessing unit is read from the first port and temporarily stored as X. Further, the environmental temperature of the thermal head 4 measured by the temperature detection means 6 is converted into a digital value by the A/D conversion means 6, and the digital value is read from the second port and temporarily stored as Y. The above-mentioned x, l! l: Y as a parameter (calculated by software 1~) Give the address of f, obtain γ correction data A, and pulse width modulation means 2 from the third port 1.
Output to.

In this embodiment, for ease of explanation, the first RAM
Although the above example includes a second RAM, the same RAM may be divided and used as long as the RAM capacity allows.

Effects of the Invention As described above in detail, in a thermal printer that performs halftone recording, according to the present invention, when the environmental temperature of the thermal head rises or falls and the relationship between density and recording pulse width changes, By adjusting the correction curve itself in accordance with the change, accurate temperature correction over the entire halftone range at any temperature can be realized at low cost with an extremely simple configuration. Note that the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the input/output characteristic conversion means is configured using a RAM, and the RAM stores gradation corrections and conversions other than the γ correction described here, as well as complexes of various conversions. Good too.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a printer device according to an embodiment of the present invention, FIG. 2 is a block diagram of a printer device according to another embodiment of the present invention, FIG. 3 is a flowchart of its processing contents, and FIG. 4 is a conventional printer device. FIG. 2 is a block diagram of a printer device in an example. 1... Input/output characteristic conversion means, 2... Pulse generation means, 3... Head driving means, 4...
... Thermal head, 6 ... Temperature detection means, 6 ... A/D conversion means, 7 ... Power supply, 11 ... CPU, 12 ...ROM. 13.14...RAM, 15,16.17...
...Input/output port. Figure 1 Figure 4

Claims (2)

[Claims] (1) a thermal head, a head driving means for applying power to a heating element of the thermal head, a pulse generating means for applying a recording pulse to the head driving means, and a temperature detecting means for detecting the temperature of the thermal head; An A/D conversion means for A/D converting the output of the temperature detection means, and an input device in which the relationship between the recording pulse width and the input gradation data at a plurality of temperatures of the thermal head is set in one ROM or one RAM. 1. A printer device comprising: an output characteristic converting means, the gradation data and the output of the A/D converting means being applied to an address of the input/output characteristic converting means. (2) Equipped with a microcomputer consisting of a CPU, ROM, RAM, and input/output ports, and the ROM or RAM
Allocate an input/output conversion means constituted by a table using a table as the memory of the microcomputer, and refer to the table by giving an address by software from the gradation data read from the input/output port and the output of the A/D conversion. A printer device according to claim 1, characterized in that: