JPH075736Y2 - Thermal printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a thermal printer installed in, for example, a video printer, and more specifically, it enables multi-gradation printing of both color printing and monochrome printing. The present invention relates to an improved thermal printer.

<Prior art> A conventional thermal printer for color is an A / D converter that converts a video signal corresponding to a printed image into gradation and outputs this in parallel as video data, and a color that is related to the contrast adjustment of the printed image. A memory in which gradation conversion data for printing is recorded in advance, and a gradation correction unit that performs gradation correction of video data based on this gradation conversion data and serial conversion of gradation corrected video data At the same time, a thermal head control unit for outputting the pixel data as pixel data and a thermal head for recording a corresponding printed image based on the pixel data are employed.

<Problems to be Solved by the Invention> However, the conventional method described above has a problem in that it is not possible to perform multi-gradation printing on both color printing and black-and-white printing. The reason for this will be described below. The thermal paper used in the thermal printer does not always have a constant color development characteristic, and accordingly, the shading must be adjusted on the thermal printer side. The gradation correction unit described above is for performing the gradation adjustment and corrects the gradation of the image data according to the color development characteristics of the thermal paper. That is, the gradation conversion data recorded in the gradation correction unit is also data corresponding to this thermal paper, and when the black and white printing is performed with the gradation correction data for color printing, the desired print image is obtained as a result. Cannot be obtained. Therefore, there is also a disadvantage that high-cost color printing must be performed where black and white printing is acceptable.

The present invention was created in view of the above circumstances,
An object of the present invention is to provide an improved thermal printer capable of performing multi-gradation printing for both color printing and monochrome printing.

<Means for Solving Problems> A thermal printer according to the present invention includes a printing method setting unit for setting a printing method and a video signal corresponding to a printing image, which is converted into gradation and is output in parallel as video data. A / D converter, and a memory in which gradation conversion data for color printing and black-and-white printing are respectively recorded in advance in order to perform optimum gradation expression regardless of the printing method. A gradation correction unit that performs gradation correction on the basis of gradation conversion data corresponding to the set printing method, and the gradation-corrected gradation conversion data are serially converted and output as pixel data. It is characterized by comprising a thermal head control unit and a thermal head for recording a corresponding printed image based on the pixel data.

<Operation> When the printing method is color, gradation correction is performed on the image data based on the gradation conversion data for color printing, and when the printing method is black and white, the operation for black and white printing is performed. The gradation of the video data is corrected based on the gradation conversion data.

<Example> An example of such a thermal printer will be described below with reference to the following drawings. FIG. 1 is an electrical configuration diagram of a thermal printer.

The thermal printers listed here are equipped with video printers, and video signals that are scanning signals for TV screens, etc.
This is a device that introduces 70 from another circuit and records a corresponding print image in a color or monochrome print system. First, the A / D converter 10 that processes the video signal 70 will be described.

The A / D converter 10 is a circuit that sequentially converts the video signal 70 into 6-bit gradation, and outputs the converted parallel video data in parallel to the gradation correction unit 20 via the video data signal 11. It is supposed to do.

The gradation correction unit 20 is a memory in which gradation correction conversion data for each printing method necessary for gradation correction of video data is recorded in advance. This gradation correction will be described later,
The gradation-corrected image data (hereinafter referred to as corrected image data) is output in parallel to the thermal head controller 50 via the corrected image data signal 21.

The thermal head control unit 50 is a circuit that serially converts the input corrected image data and sequentially outputs this as pixel data to the thermal head 60 via the signal 51 at a predetermined timing. More specifically, the thermal head controller 50 is controlled by a print control signal 42 derived from the printer controller 40, which will be described later, and a reference clock signal 71 derived from another circuit. Of the data, necessary corrected video data is sequentially output at a timing synchronized with the reference clock signal 71.

The thermal head 60 energizes a corresponding heating element group (not shown) based on the corrected image data to record a color or black-and-white printed image. By the way, such a thermal printer is controlled based on an instruction from a control circuit (CPU) of a video printer (not shown). The printer control unit 40 which acts as an interface between the two will be described below. To do.

The printer control unit 40 is provided with a setting signal 31 and a print start signal 411, in addition to the data bus (not shown) to which the command from the control circuit (CPU) of the video printer is sent. Here, the setting signal 31 is an output signal of the printing method setting unit 30 such as a changeover switch for setting and inputting the printing method, and the printing start signal 411 is derived from the printing start setting unit 31 such as a printing start switch. Signal. Based on these input signals, the printer controller 40
Is the print control signal 42 and the print setting signal 41 described above.
And are output as appropriate. The print setting signal 41 is a signal related to the setting signal 31 and may be signal-processed by the printer control circuit 40 depending on the state of the thermal printer side. In the case of color, it is at the H level. Here, the gradation correction unit 20 will be described again.

In the gradation correction section 20, the video data signal 11 is connected to the read address terminals A _{0 to} A ₅ , and the print setting signal 41 is connected to the read address terminal A ₆ . The gradation correction conversion data for black-and-white printing is input to the lower address of the memory space in this memory, and the gradation correction conversion data for color printing is input to the upper address in the same manner.
On the basis of the above, the gradation correction conversion data is appropriately switched. That is, when the print setting signal 41 indicates the black-and-white printing method, gradation correction is performed on the video data based on the grayscale correction conversion data, and the print setting signal 41
Indicates a color printing method, the image data is similarly subjected to gradation correction based on the gradation correction conversion data for color. This means that the gradation correction conversion data for gradation correction of video data is switched according to the printing method, and as a result, a printed image having a desired density can be recorded.

Note that the thermal printer is not limited to the above-described embodiment, and may be applied to, for example, another device instead of the video printer. In this case, the printer controller
40 or the print start setting unit 31 may be omitted,
Further, it goes without saying that the heating element of the thermal head may be a matrix type or the like instead of the one line type.

<Advantages of Device> As described above, the thermal printer according to the present invention is configured to automatically change the optimum gradation correction amount according to the setting of the printing method. Even if there is, it will be the optimum gradation expression. As a result, it is possible to perform both multi-gradation printing on both color and black and white prints, and when performing black and white printing, it is possible to use black and white thermal paper, which is cheaper than the color ink cassette for color printing. Produce an effect.

[Brief description of drawings]

FIG. 1 is an electrical block diagram of an embodiment of a thermal printer according to the present invention. 10 …… A / D converter 20 …… Gradation correction section 30 …… Printing method setting section 40 …… Thermal head control section 50 …… Thermal head 70 …… Video signal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 5/91 7734-5C H04N 5/91 H

Claims (1)

[Scope of utility model registration request] 1. A printing apparatus for performing multi-gradation printing by switching between a color printing method and a black-and-white printing method, and a printing method setting section for setting the printing method and converting a video signal corresponding to the printing image into gradation. Along with the A / D converter that outputs this in parallel as video data, the gradation conversion data for color printing and black-and-white printing are recorded in advance so that optimum gradation expression can be achieved regardless of the printing method. And a gradation correction unit that corrects the gradation of the video data based on the gradation conversion data corresponding to the set printing method, and the gradation-corrected gradation conversion data is serially converted. A thermal printer comprising: a thermal head controller that outputs this as pixel data; and a thermal head that records a corresponding printed image based on the pixel data.