JPS61277279A - Printer of television receiver - Google Patents

Abstract

PURPOSE:To attain copying with uniform density by providing a power application time conversion table at each prescribed temperature of a thermal head and at each gradation density so as to decide the actual power application time of the thermal head thereby reducing variation in the density. CONSTITUTION:The address for a video memory 3 is designated by a CPU 8 and a read gradation density signal is converted into a 15-bit density data by the CPU 8. On the other hand, a temperature detection circuit 12 detects a thermal head temperature in a heat sensing printer 6 and the CPU 8 corrects table values x(0)-x(14) of the density (0-14) patterns of the power application time table depending on the detected temperature of the circuit 12. A counter 9 counts the reference clock (f) from a frequency divider 10 and when the count reaches the table value of the density (0) pattern subject to correction, the counting is stopped and when the CPU 8 reaches the state that the table value of the density (1) pattern of the power application time table is subject to count processing, the data transfer of the 1st bit is finished. Thus, the variation in the copy density is eliminated and uniform copying is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printer device for a television receiver.

[Conventional technology]

Generally, when a cooking program is being broadcast on a television receiver, you may want to write down the menu list and ingredients displayed on the screen. This was extremely inconvenient as the person had to take notes on the menu list, ingredients, etc. while looking at the screen each time. In addition, if the cooking program mentioned above is recorded on a VTR, it can be played back again, but even in that case, it is necessary to search for the necessary screen and play it back statically, which is complicated. Ta.

Therefore, the inventor of the present invention has already developed a printer device for a television receiver that can temporarily store the gradation density signal of the image on the television screen in a RAM, read it out, and automatically make a hard copy.

[Problem to be solved by the invention] By the way, this printer device uses a thermal printer widely used in facsimiles, etc., and copies the above-mentioned image by controlling the energization time of the thermal head in the printer. is possible. However, in this case, if the voltage is applied for the energization time set in advance according to the level of the gradation density signal, the copy density of the thermal paper will be affected by changes in the ambient temperature of the thermal head, especially when copying. If it continues for a long time, the temperature of the thermal head itself will rise due to self-heating, so even if the thermal head is energized for a constant time, the copy density will change due to the temperature change of the thermal head itself, as shown in Figure 6. The problem is that it changes drastically.

The present invention has been made in view of the above problems, and provides a printer device for a television receiver that reduces variations in copy density due to temperature changes in the thermal head itself and makes copies with uniform density. It is intended to.

[Means for solving problems]

The printer device for a television receiver according to the present invention includes:
An energization time conversion table is provided for each predetermined temperature of the thermal head and for each gradation density, and the actual energization time of the thermal head is determined based on the table according to the temperature of the thermal head itself.

[Effect]

In this invention, since temperature correction is performed for all gradation densities, there is no variation in copy density due to temperature changes in the thermal head, and since the thermal head temperature is divided into predetermined temperature units and a conversion table is provided, the memory The capacity will not increase.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a printer device for a television receiver according to an embodiment of the present invention. In the figure, 1 is a synchronization separation circuit that synchronously separates the television signal t into a video signal V, a horizontal synchronization signal 31, and a vertical synchronization signal S2;
An A/D converter for converting into a bit-level sub-density signal d; 3 a video memory for storing the gradation density signal d; 4 a CP to be described later.
A write control circuit performs write control to the video memory 3 when a write command e is input from U8, 5 is a reference oscillator that generates a reference clock, 6 is a thermal printer having a thermal head, and 7 is a circuit that controls the pulse width of print data a. This is a head drive circuit that applies a constant voltage to the thermal head for a certain amount of time.

Further, 8 is a CPU having a conversion table for converting the gradation density signal into print data a, and when a copy command C is input from the outside, the CPU 8 outputs a write command e to the write control circuit 4, and the CPU 8 outputs a write command e to the write control circuit 4, When this is completed, the video memory 3 is addressed and the gradation density signal is read out, and the signal is converted into print data a using the conversion table and output. Here, the conversion table consists of a density data conversion table and an energization time table, and the density data conversion table converts the gradation density signal into a number of consecutive "1's" corresponding to the gradation density, and the rest are "1"s. For example, for a signal of gradation density 5, the density data of 15 bits is "11111000000" as shown in FIG.
0000'', and in this Figure 2, the density i pattern (i=0 to 1
4) is data of the i+1th bit of the density data. On the other hand, the energization time table shown in FIG.
~x(14). Here, the transfer time T (1) of the density i pattern is the energization time T (0) to obtain printing with gradation density 1, the energization time T (0) to obtain printing with gradation density 2, and the energization time T (0) to obtain printing with gradation density 1. Difference T from energization time to obtain printing
(1) Similarly, the difference T (14) between the energization time to obtain a print with a gradation density of 15 and the energization time to obtain a print with a gradation density of 14.

In addition, in Figure 1, 9 is a counter, and 10 is 1 from the CPU 8.
．． Frequency divider that divides the 36μsec oscillation signal into 1/4, 1
1 is a paper/rotation speed detection circuit that detects the presence or absence of thermal paper and the morph rotation speed of the thermal printer 6;
U8 further controls the generation of print data a and the reading of gradation density signals according to the motor rotation speed detected by the paper/rotation speed detection circuit 11, and also controls the external warning device (Fig. warning signal g
Output. Further, 13 is a control signal line, 14 is an address bus, and 15 is a data bus.

Reference numeral 12 is a temperature detection circuit for detecting the temperature of the thermal head, and the CPU 8 is a temperature detection circuit 12 that can actually obtain the copy density corresponding to the gradation density signal, regardless of changes in the temperature of the thermal head due to self-heating. The table value x(0) of the above energization time table according to the detection signal of
~Correct X(14).

Next, the operation will be explained.

In this device, when a copy command C is given, the CPU
8 outputs a write command e to the write control circuit 4, then the television signal t is synchronously separated by the synchronous separator 1, and the video signal V is converted into a 4-bit gradation density signal d by the A/D converter 2. The signal d is then written into the video memory 3 according to the write control of the write control circuit 4.

And one field of video, that is, 280 pixels in the horizontal direction,
When all the gradation density signals d of 234 lines in the vertical direction are written into the video memory 3, the video memory 3 is transferred to the CPU 8.
The gradation density signal addressed by and read out is converted into 15-bit density data by the CPU 8 using a density data conversion table. On the other hand, the temperature detection circuit 12 detects the temperature of the thermal head inside the thermal printer 6,
In the CPU 8, the table values x(0) to x(14) of the density 0 to 14 patterns of the energization time table are detected by the temperature detection circuit 12.
It is corrected according to the detected temperature (every 5°C).

The above density data is first the data of its first bit (
The density O pattern) is transferred from the CPU 8 to the head drive circuit 7, and at the same time, in the CPU 8, the counter 9 counts the reference clock f from the frequency divider 10, and when the count value becomes the corrected daple value of the density 0 pattern, When the counting operation is stopped and the CPU 8 becomes ready to count the table value of one density pattern of the energization time table, the transfer of the first bit data is completed. From then on, each bit of data is transferred for a time determined by the table value. In this way, the number of "1" data corresponding to the gradation density is transferred for a time determined by the table value x (1) of the energization time table and the thermal head temperature, so that the head drive circuit 7 receives the data of the thermal head. Print data a with a pulse width corrected according to the temperature is input, and the circuit 7 applies a constant voltage to the thermal head for a time corresponding to the pulse width of the print data a,
As a result, printing is performed on the thermal paper with a density corresponding to the gradation density signal.

Here, as a temperature correction method, if the energization time table value x (ol~X (14)) is provided for each temperature, the effect of the correction will be maximized, but this will increase the memory capacity. Therefore, we devised a method to do this effectively with a small amount of memory.

One of them is that, unlike the above embodiment, temperature correction is performed only for the energization time table value x(0) with a gradation density of 0, and no correction is made for the other x(1) to x(14). It's a method. Fig. 4 shows the experimental results of determining the change in copy density with respect to the temperature change of the thermal head without temperature correction and with temperature correction in such a method. The solid line c+1 point dashed line 6 shows the relationship when the density is 15 and there is no temperature correction, and there is no temperature correction.

According to FIG. 4, when there is no temperature correction, as can be seen from the slopes of solid lines a and C, the copy density with a gradation density of 15 is more affected by the temperature change of the thermal head than that with a gradation density of 1. is recieving. On the other hand, when temperature correction is applied, the slope of the dashed-dotted line s becomes smaller, while the slope of the dashed-dotted line d becomes negative, but its absolute value remains almost unchanged. It can be seen that the influence of head temperature change is small for both gradation densities of 1 and 15, and that variations in copy density are suppressed to some extent.

However, as can be seen from the slope of the dashed-dotted lines s and d in Figure 4, there is still a difference in concentration between low and high temperatures.

This variation in concentration is determined by the energization time table x(1) to x
This is because the concentration could not be fully corrected because (14) was performed without temperature correction. Therefore, in this embodiment, the energization time table x(0) to X(1
Temperature correction is performed for all of 4). However, if we make this correction for each temperature, the memory capacity will become too large, so we divide the head temperature into 5°C increments.
The temperature correction described above is performed for each unit.

This method is based on the fact that if the temperature change of the thermal head is about 5.degree. C., the change in density will not be noticeable to the human eye even if the same energization time table is used.

When temperature correction is performed using this method, as shown in Figure 5, the energization time table changes at every 5°C interval, resulting in variations in concentration, but these changes are ignored by the human eye. It can be seen that there is no variation in concentration between low and high temperatures of the thermal head as a whole.

〔Effect of the invention〕

As described above, according to the printer device for a television receiver according to the present invention, temperature correction is performed for each gradation density using a conversion table for each predetermined temperature according to the temperature of the thermal head. This makes it possible to eliminate variations in copy density due to temperature changes in the thermal head with a small memory capacity, and has the effect of making uniform copies possible.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a printer device for a television receiver according to an embodiment of the present invention, Fig. 2 is a diagram for explaining the functions of the above device, and Fig. 3 shows the values of the energization time table of the above device. FIG. 4 is a diagram showing the experimental results of changes in copy density with respect to temperature changes of the thermal head with and without temperature correction, and FIG. FIG. 6 is a diagram showing the relationship between temperature change due to self-heating of the thermal head and copy density. 3... Video memory, 4... Write control circuit, 6...
・Thermal printer, 7...head drive circuit, 8...C
PU (drive control circuit), 12... temperature detection circuit (temperature detection means). Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A printer device that prints out images from a television receiver, which includes a video memory that stores gradation density signals of images to be printed out, and controls writing of the gradation density signals to the video memory. a thermal printer having a thermal head, a temperature detection means for detecting the temperature of the thermal head, a density conversion table for converting a gradation density signal into density data according to the signal, and the thermal head. has an energization time conversion table for converting density data into energization time of the thermal head for each predetermined temperature and each gradation density, and the density of the gradation density signal read from the video memory is actually obtained. A printer for a television receiver, comprising: a drive control circuit that determines the actual energization time of the thermal head; and a head drive circuit that applies a constant voltage to the thermal head for the actual energization time. Device.