JPS6148273A - Recording signal correcting method - Google Patents

Abstract

PURPOSE:To eliminate variance in density by preparing n-set of correction coefficients less than the number of recording signals for one line's share and assigning the coefficients to the recording signals for correction. CONSTITUTION:A video synchronizing signal is transmitted to a sample pulse generator 1, where a sampling pulse is formed and transmitted to an A/D converter 2 and a counter 3. A video signal is digitized in the A/D converter 2 and transmitted to an address section of the 2nd memory 4. On the other hand, an output of the counter 3 is transmitted to the address section of the 1st memory 5, which selects a data and gives it to the address section of the memory 4 so as to correct the signal at each corresponding element.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a recorded signal correction method, and is particularly suitable for high-quality image transmission and recording in signal processing devices such as printers and facsimiles. The present invention relates to a recording signal correction method.

[Background of the invention]

Japanese Patent Application Laid-Open No. 56-38279 relating to a conventionally known thermal recording device
The publication described in the publication describes a method for correcting secular changes and variations in the resistance value of the heating element of the thermal head, but for correction of the recording signal, only the output control circuit is used, and there is no specific correction method. has not been stated.

Although it is easy to change the voltage applied to the heating elements all at once, it is extremely difficult to change the voltage applied to each heating element.

The resistance values of the heating elements vary by ±20 even at the initial stage of manufacture, and in order to improve the print quality, it is necessary to correct each heating element, which is especially essential when dealing with gradation images.

In this respect, it can be said that the above-mentioned known examples do not recognize the importance of correction and the difficulty in implementing it.

[Purpose of the invention]

In a thermal head that records line by line, there are variations in the resistance value of each heating element, variations in wiring resistance, variations in the characteristics of the driving transistor, etc., and the density is not uniform even if the same signal is sent. Density unevenness occurs in the image, resulting in a reduction in image quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide a recording signal correction method that can perform the necessary correction for each recording signal so that density unevenness does not occur.

[Summary of the invention]

In the recording signal correction method according to the present invention, n sets (n There is a method in which correction coefficients are prepared (where n is an integer and n≧2), and which one is assigned to the recording signal for correction.

To add more information, the following points are in order.

When there are a large number of recording signals, performing correction calculations for each recording signal will complicate the circuit, and depending on the recording signal, the same correction coefficient may be used.
The correction coefficients are divided into groups according to size, coefficients representing each group are prepared, and the group number is selected based on the recording signal to correct the signal.

[Embodiments of the invention]

Embodiments of the recording signal correction method according to the present invention will be described with reference to the respective figures.

FIG. 1 is a block circuit diagram of a recording signal correction device used to implement a recording signal correction method according to an embodiment of the present invention;
FIG. 2 is a block circuit diagram of a recording signal correction device used for implementing other embodiments, and FIG. 3 is a diagram showing measurement results of recording density variations before and after signal correction, in which (a) The former and (b) are after correction.

First, an embodiment of the recording signal correction apparatus shown in FIG. 1 will be described.The apparatus digitizes a video signal and sends it to a recording apparatus. Further, the video synchronization signal is sent to the sample pulse generator 1, and pulses for sampling are generated.

Therefore, the pulse of the sample pulse generator 1, A/D
It is sent to converter 2 and counter 3.

Then, in the A/D converter 2, the video signal is digitized and sent to the address section of the semiconductor memory 4 related to the second memory.

On the other hand, the output of the counter 3 is sent to another address section of the semiconductor memory 5 related to the first m memory, and
, and sends the selected data to the address section of the semiconductor memory 4.

Therefore, when using a line-shaped thermal head, each heating element (simply referred to as an element) has a resistance.

The wiring resistance, the characteristics of the driving IC, etc. are different, and even if the signal is the same, the printed density is different, so the signal value is corrected for each corresponding element.

In this case, theoretically, the number of correction coefficients is equal to the number of elements, but as a result of measurement, it has been found that there are similar coefficients, ±30
In the case of variation in resistance, if 15 sets of correction coefficients are prepared, the variation can be reduced to ±2 inches, so it has been found that it is sufficient to prepare a smaller number of sets of correction coefficients than the number of elements.

In other words, n sets smaller than the number of signals (n is an integer, n≧2
) was found to be sufficient.

Therefore, in the above case, the correction coefficients corresponding to resistance variations of ±30 are classified into, for example, 15Iiii, representative values are determined for each, and correction results based on these values are written in the semiconductor memory 4.

On the other hand, in another semiconductor memory 5, a table related to the set number of correction coefficients corresponding to each element is written.

With this configuration, the A/D converted signal of the sample pulse is sent to the address section of the semiconductor memory 4 together with the correction coefficient set number written in the semiconductor memory 5, and the correction result is stored as data in the semiconductor memory 4. is what is output.

Even when the video signal changes, some of the addresses in the semiconductor memory 4 change, but similar corrections can be made by writing the corresponding correction results in those addresses.

Here, the signal is (3 bits, the number of elements is 1024, the correction coefficient is Xl, 3.Xl, 25..., Xl, O
,·Mountain··.

Considering 13 ways of ×0.7, the required memory capacity of the semiconductor memory 4 is as follows.

Address...26X13=832 data...
...26=64 Memory amount...832X64=53248bit
On the other hand, in the semiconductor memory 5, the situation is as follows.

Address...1024 Data...13 Memory amount...1024X/3=13312bi
t1 All of these sizes are easily realized.

In this case, if each element has a correction coefficient, 10
It can be seen that this would require 24/13 x 79, or approximately 79 times as much memory, which would be unrealizable.

In this example, the variation in resistance of ±30 coefficients is equivalently reduced to an upper coefficient of 2°5, and the variation can be reduced to 1/16.

Next, in another embodiment using the circuit of FIG. 2, the number of the correction coefficient related to the signal from the semiconductor memory 5 is
The resistor group 7 that gives the amplification degree of the operational amplifier 8 is changed, and the signal is corrected by changing the amplification degree of the operational amplifier 8.The same effect as in the previous embodiment using the circuit shown in FIG. 1 is obtained. That's what you get. Note that the same reference numerals as in FIG. 1 indicate equivalent parts.

It can be seen that both of the devices used in the above two embodiments do not use expensive multipliers, and therefore can be realized at low cost and with a simple configuration.

FIG. 3(a) is an example of measuring density variations before correction when a thin film thermal head is used.

The horizontal axis is the element position, and the vertical axis is the concentration ratio to the average concentration.The overall change in the concentration ratio is mainly due to unevenness in the thin film resistor due to sputtering, and small changes are due to variations in wiring resistance, This is due to variations in the characteristics of the driving IC, and the overall variation is within a factor of ±30.

FIG. 3(b) shows the case after correction using the present invention and using 16 correction coefficients, and it can be seen that the variation in density has been reduced to about ±2 circles.

In this case, even if the average density is changed by changing the voltage commonly applied to the elements to achieve the desired density, the difference in density between the elements cannot be resolved and the image quality will not improve. Also,
It is also possible to divide the elements into several sets of blocks and make corrections for each block, but as can be seen from the actual measurement example in Figure 3 (a), the variation for each element is large and the effect of correction is small. .

Furthermore, in the case of a thick-film head, the variation in resistance value is greater than that of a thin-film head, and there is little correlation with neighboring elements, so
This requires correction for each element according to the present invention.

〔Effect of the invention〕

As described above, according to the present invention, variations in recording density due to variations in resistance of heating elements, variations in wiring resistance, variations in characteristics of drive IC, etc. can be corrected for each heating element, so high-quality printed images can be obtained. can be obtained.

Further, even in recording heads other than thermal heads, by using the method according to the present invention, correction can be made for each heating element, so that high-quality recording without density variations can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a recording signal correction device used to implement a recording signal correction method according to an embodiment of the present invention;
FIG. 2 is a block circuit diagram of a recording signal correction device used for implementing another embodiment, and FIG. 3 is a diagram showing measurement results of variations in recording density before and after signal correction. DESCRIPTION OF SYMBOLS 1... Sample pulse generator, 2... A/D converter, 3... Counter, 4.5... Semiconductor memory,
6...Electronic switch, 7...Resistor group, 8...Operation amplifier.

Claims (1)

[Claims] 1. In a device that performs gradation recording using a recording head that records line by line, for one line of recording signals sent to the recording head, there are n sets (n is an integer) smaller than the number of signals. , n≧2), and allocating the correction coefficient to the recording signal to perform correction. 2. In the thing described in claim 1, the first
and a second memory storing the correction results of the recording signal using the correction coefficients, and the correction results of the second memory are selected according to the number of the correction coefficients read from the first memory. recording signal correction method. 3. The device according to claim 1 is provided with a memory storing a number table of correction coefficients assigned to each recording signal and an amplifier capable of changing the amplification degree, so that the signal from the memory is A recording signal correction method that corrects each recording signal by changing the amplification degree of the amplifier.