JP3407091B2 - Gradation value correction device and gradation value correction method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation value correction method in a gradation printer of a line thermal transfer system, and more particularly, the energization amount for each of a plurality of dots arranged for each line is A printing device that is uniquely determined by the target gradation value,
The present invention relates to a gradation value correction device and a gradation value correction method.

[0002]

2. Description of the Related Art In this type of printing apparatus, since the density (gradation) of the corresponding pixel is determined by the amount of electricity supplied to each dot, the amount of electricity supplied to each dot must be adjusted in order to obtain a high quality print result. Defined gradation value (target gradation value, same hereafter)
Is an important factor. Generally, there is a non-linear relationship between the amount of electricity applied to a dot and the density of a pixel formed as a result, and the relationship between the two changes depending on the recording paper and ink used. Therefore, it is desirable to determine the target gradation value after fully considering the relationship between the energization amount and the resulting pixel density.

As a conventional technique of this kind, for example, Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. 3-116876 discloses a technique in which the non-linear relationship between the energization amount and the pixel density is stored in advance in a ROM cartridge as γ correction data and the control data is read out as needed. Also, JP-A-63-11687
In addition to the ROM cartridge, Japanese Patent Publication No. 5 discloses a technique of displaying on a display or the like what kind of ink and recording paper the control data is based on.

When a dot is actually energized, heat is generated in the dot in accordance with the amount of energization, but when pixels are continuously formed, the heat generated in the previous printing is accumulated, Further, since the heat generated in the surrounding dots is also conducted, the temperature of the dots gradually increases. If energization control is performed ignoring such a state, a desired gradation may not be obtained during printing. Therefore, there is a need for a gradation value correction device that takes into consideration the relationship between the above-mentioned energization amount and the density of the corresponding pixel and the relationship between the heat generated in the surrounding dots.

FIG. 4 shows an example of a functional block of a conventional gradation value correction device in consideration of the above points. The gradation value correction device shown in this figure exists in the gradation data storage unit 1 that stores the gradation data for each pixel, the past gradation value of the pixel corresponding to each dot, and the periphery of that pixel. A correction coefficient storage unit 6 that stores a predetermined correction coefficient that represents the magnitude of the effect of the gradation value of a pixel, a multiplication unit 7 that multiplies the gradation value of each pixel by the correction coefficient, and the respective multiplications. An F ′ calculation unit 4 that adds the results and subtracts the addition result from the target grayscale value of the pixel to be formed (target pixel, the same applies hereinafter).
And a print data storage unit 5 for storing print data of the target gradation value corrected by subtraction.

FIG. 5 is an explanatory view of pixels on a line to be printed and pixels on the line immediately before. In this figure,
f is the target pixel, a and e are adjacent pixels adjacent to the target pixel,
b, c, and d represent the pixels one line before corresponding to a, f, and e, respectively. In this case, the corrected gradation value F ′ of the target pixel f is obtained by the following equation.

[0007]

[Equation 1]   F '= F- (v * A + w * B + x * C + y * D + z * E) ... (1)

However, F is the target gradation value of the target pixel f before correction, A to E are the gradation values of the pixels a to e existing around the target pixel f, and v to z are the above pixels. It is a correction coefficient of ae. This correction coefficient is a numerical value actually measured in consideration of the influence of accumulated heat, conductive heat, etc., and the larger the numerical value, the higher the influence.

The multiplication unit 7 shown in FIG. 4 reads the gradation values A to E from the gradation data storage unit 1, further reads the corresponding correction coefficients v to z from the correction coefficient storage unit 6, and v.
Multiplies A, w · B, x · C, y · D, z · E, and sends the result to the F ′ calculation unit 4.

The F'calculation unit 4 adds the sent multiplication results, subtracts it from the target gradation value F read from the gradation data storage unit 1, and obtains the corrected gradation value F '. And write it in the print data storage unit 5.

[0011]

Although the tone value correction device described above has the effect that the required tone can be printed by the correction that also takes into account the past thermal history, the calculation process for deriving the correction value is performed. Since it contains the multiplication of a number with a large number of digits,
Not only the expensive multiplication circuit is required, but also the calculation time becomes considerably long, which is a factor of prolonging the printing time. In particular, when highly accurate gradation value correction is performed, the number of digits of the numerical value to be calculated becomes large, and since decimal numbers are sometimes handled, there is a problem that the circuit scale becomes large.

Such a problem is almost common to the above-mentioned technique of storing the γ correction data in the ROM cartridge, and a multiplication result with a large number of digits is required when performing the γ correction. It is inevitable that the time will be long.

In view of the background described above, an object of the present invention is to provide a gradation value correction device and a gradation value correction method capable of performing highly accurate gradation value correction in a short time.

[0013]

In order to solve the above-mentioned problems, according to the present invention, the energization amount to each of a plurality of pixel-forming heating elements (hereinafter, referred to as dots) arranged in each line is set to the corresponding pixel. A printing device that is uniquely determined by a target gradation value, and a predetermined correction is made to the past gradation value of the target pixel, the gradation value of an adjacent pixel adjacent to the target pixel, and the past gradation value. A device for correcting a target gradation value of the pixel of interest based on gradation correction data obtained by multiplying the coefficient, and a result of multiplication of all gradation values of individual pixels and the correction coefficient. A memory in which the gradation correction data group obtained by the above is stored in association with the identification information of the gradation value of each pixel, the target gradation value of the target pixel and the adjacent pixel, and the past gradation value of each pixel are identified. Pixel-by-pixel gradation value identifying means, and each identified Memory control means for selectively extracting from the memory the gradation correction data corresponding to each tone value; and calculating means for deriving a new target gradation value of the pixel of interest based on the extracted gradation correction data. A gradation value correction device having the same is provided.

The memory includes, for example, a first memory in which each pixel and its gradation value are stored in association with a predetermined address value, and the gradation correction previously generated for each pixel and its gradation value. A second memory that stores the data in association with the identification information of the gradation value of each pixel, and the memory control unit includes the gradation value of the pixel identified by the pixel-specific gradation value identification unit and the first memory. The identification information of the pixel is generated from the corresponding address value of the memory and the gradation correction data related to the generated identification information is selectively extracted from the second memory.

Further, according to the present invention, in the printing apparatus in which the energization amount for each of the plurality of dots arranged for each line is uniquely determined by the target gradation value of the pixel, Of the gradation value of the pixel of interest, the gradation value of the adjacent pixel adjacent to the pixel of interest, and the past gradation value thereof are respectively multiplied by a predetermined correction coefficient, and the pixel of interest is calculated based on the gradation correction data obtained thereby. Is a gradation value correction method for correcting the target gradation value of, and a gradation correction data group is generated based on the multiplication result of all the gradation values of each pixel and the correction coefficient. Is stored in a memory in association with identification information uniquely determined by each pixel and its gradation value, and the target gradation value of the target pixel and the adjacent pixel and the past gradation value of each pixel are stored. At the identification stage and for each identified gradation value And selecting extracting the gradation correction data s corresponding from the memory, even tone value correction method characterized by having provided.

[0016]

In the present invention, for example, the target gradation value and the past gradation value for each pixel are stored in the first memory,
In addition, all target gradation values and past gradation values that can be adopted for each of these pixels and a multiplication value of a predetermined correction coefficient are associated with identification information uniquely derived from the gradation value, and the second memory Remember. The pixel-by-pixel gradation value identification means identifies the target gradation value of the target pixel and the adjacent pixel and the past gradation value of each pixel, and the memory control means determines the corresponding gradation correction data according to the identification result. The first and second memories are searched and selected and extracted. In this way, by storing the gradation correction data based on the multiplication result in a readable manner in advance, it is not necessary to perform complicated multiplication each time. Therefore, the gradation correction data is promptly selected and extracted without using the multiplication circuit, and the device configuration for obtaining the corrected gradation value becomes simple and inexpensive.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings. This embodiment has a gradation value correction device 6
This is an example of a case where an appropriate gradation value correction is performed in a 4-gradation line thermal printer.

FIG. 1 is a block diagram of a gradation value correcting apparatus according to an embodiment of the present invention, in which reference numeral 1 is a floor for storing gradation data of each pixel sent from a host computer or the like. A tone data storage unit (first memory), 2 is an address generation unit, 3 is a gradation correction data storage unit (second memory), 4 is an F ′ calculation unit (calculation unit), and 5 is a print data storage unit. is there. Although not shown, it is assumed that a known pixel-by-pixel gradation value identifying means for identifying the gradation value of each pixel is provided in the preceding stage of the gradation data storage unit 1 or in the host computer. . First, in Table 1, one line is 1024
An example of the contents of the gradation data storage unit 1 having a memory capacity for two lines in a pixel line thermal printer is shown.

[0019]

[Table 1]

As shown in Table 1, when the target gradation value F of the target pixel f is stored at the address 402h of the gradation data storage unit 1, the pixel one line before the target pixel f and the target pixel f are selected. The gradation values A to E of the pixels a to e adjacent to the present and one line before are 401h, 002h, and 003, respectively.
h, 403h. The address generator 2
The gradation values A to E of the pixels a to e are read from the gradation data storage unit 1 and the addresses (identification information) are generated. FIG. 2 is an explanatory diagram of these addresses, and FIG. 3 shows a concrete example of their contents.

As shown in FIG. 2, each address is composed of 9 bits, the upper 3 bits thereof indicate the type of the pixels a to e, and the lower 6 bits thereof are the gradation values AE as they are. Further, as shown in FIG. 3, when the gradation value of the pixel b is “52”, the generation address is 074h.

In the gradation correction data storage unit 3, v.multidot.A to z.multidot.E (gradation correction data) of the equation (1) are preliminarily multiplied and stored. However, in this example, since the values of v · A to z · E are decimals, it is assumed that they are stored by multiplying them by 1024 and discarding the fractional part. In Table 2, the correction factors are v = 0.05, w = 0.03, x = 0.
1, the contents of the gradation correction data storage unit 3 when y = 0.03 and z = 0.05 are shown.

[0023]

[Table 2]

In Table 2, the column corresponding to the address generated in the address generator 2 is stored in the address column, and (correction coefficient × gradation value × 1024) is stored in the data column.
A value obtained by converting the value of the integer part of the value of H into a hexadecimal number is stored in association with the above address. For example, in the case of the pixel a, the value of the correction coefficient v is “0.05”, so if the gradation value is “63”, the value of (correction coefficient × gradation value × 1024) is “3225.6”. Become. Therefore, in the data column, "0C99" which is a value obtained by converting "3225" into a hexadecimal number.
“H” is the address “03” that represents the pixel a with the gradation value “63”.
It is stored in association with “Fh”.

Next, the operation of the apparatus for deriving the corrected gradation value F'will be described in detail using the numerical values in Tables 1 and 2. To obtain the corrected gradation data F ′ of the pixel of interest f,
The address generator 2 uses the gradation data storage 1 to acquire the gradation values “52”, “58”, “21”, “3” of the pixels a to e.
9 ”and“ 5 ”are read out, and the corresponding addresses 034h, 13Ah, and 215 are read into the gradation correction data storage unit 3, respectively.
It outputs h, 327h, and 405h. The gradation correction data storage unit 3 stores the data 0A66h (2
662), 06F5h (1781), 9866h (21
50), 04AEh (1198), 0100h (25
6) is selectively extracted and output to the F ′ calculation unit 4.

The F'calculation unit 4 sequentially adds the data sent from the gradation correction data storage unit and divides the total by 1024 to obtain the gradation correction value "7". At this time, the fractional part is truncated. The F ′ calculation unit 4 further reads the gradation value “43” of the pixel f from the gradation data storage unit 1 and subtracts the gradation correction value “7” from this gradation value “43” to obtain the corrected floor. The key value "36" is obtained. Therefore, the corrected gradation value F ′
Is calculated by the following equation 2.

[0027]

[Equation 2] F '= 43-[(2662 + 1781 + 2150 + 1198 + 256) / 1024] = 43-7 = 36

The same operation and calculation are performed for all the pixels on one line of the thermal head, and the calculation results are sequentially stored in the print data storage unit 5.

In this way, the corrected tone value can be obtained without performing multiplication. Therefore, as is clear from the structural comparison with the conventional tone value correction apparatus shown in FIG. 4, the multiplication unit 7 which requires expensive and complicated processing is not required, and the apparatus is downsized and simplified, and Cost reduction is possible. In addition, the printing time can be shortened at the same time. It is needless to say that the above numerical values are convenience values for explaining the operation of the gradation value correction device of the present invention and are not intended to limit the content of the present invention.

[0030]

As is apparent from the above description, according to the present invention, the gradation value of each pixel is identified, and corresponding gradation correction data is selectively extracted from the memory according to the identification result. Since it is possible to correct the target gradation value of the pixel of interest using only the extracted gradation correction data and a simple adder / subtractor circuit, there is no need to perform complicated multiplication processing each time as in the past, and the calculation speed and thus the printing time It is possible to obtain the same effect as is greatly shortened. Further, since the multiplication circuit is not required, the device configuration is extremely simplified, which is advantageous in terms of cost.

[Brief description of drawings]

FIG. 1 is a functional block diagram of a gradation value correction apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of address bits according to the present embodiment.

FIG. 3 is an explanatory diagram of a specific example of address bits according to the present embodiment.

FIG. 4 is a functional block diagram of a gradation value correction device according to a conventional example.

FIG. 5 is an explanatory diagram of pixels for each line.

[Explanation of symbols]

1 Gradation data storage 2 Address generator 3 Correction data storage 4 F'calculator 5 Print data storage 6 Correction coefficient storage 7 Multiplier

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-270976 (JP, A) JP-A-3-264 (JP, A) JP-A-6-196967 (JP, A) JP-A-5- 14128 (JP, A) JP-A-4-323910 (JP, A) JP-A-4-252586 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41J 2/36 B41J 2 / 52 H004N 1/407

Claims (2)

(57) [Claims] 1. A printing apparatus in which the amount of electricity to each of a plurality of pixel-forming heating elements (hereinafter referred to as dots) arranged on each line is uniquely determined by a target gradation value of the pixel. , The past gradation value of the pixel of interest, the gradation value of an adjacent pixel adjacent to the pixel of interest, and the past gradation value thereof are respectively multiplied by a predetermined correction coefficient, and the gradation correction data obtained by this is multiplied. A gradation value correction device for correcting a target gradation value of the pixel of interest based on a gradation correction data group obtained by multiplying each of the gradation values of individual pixels by the correction coefficient. A memory that stores the gradation value of each pixel in association with the identification information of the gradation value; and a pixel-by-pixel gradation value identifying means for identifying the target gradation value of the target pixel and the adjacent pixel and the past gradation value of each pixel. , The gradation corresponding to each identified gradation value Memory control means for selectively extracting correction data from the memory; and computing means for deriving a new target gradation value of the pixel of interest based on the extracted gradation correction data . Predetermine each pixel and its gradation value
The first memory stored in association with the address value of
Therefore, the gradation correction data generated for each pixel and its gradation value
Stored in association with the identification information of the gradation value of each pixel.
A second memory, wherein the memory control means is
The gradation value of the pixel identified by the gradation value identifying means for each pixel and the image
The identification information of the pixel is generated from the element type and generated.
The gradation correction data related to identification information is stored in the second memory.
Grayscale characterized by being selectively extracted from memory
Value correction device. 2. A printing apparatus, wherein an energization amount for each of a plurality of pixel-forming heating elements (hereinafter referred to as dots) arranged for each line is uniquely determined by a target gradation value of the pixel. , The past gradation value of the pixel of interest, the gradation value of an adjacent pixel adjacent to the pixel of interest, and the past gradation value thereof are respectively multiplied by a predetermined correction coefficient, and the gradation correction data obtained by this is multiplied. A gradation value correction method for correcting a target gradation value of the pixel of interest based on: a gradation correction data group based on a result of multiplication of each gradation value of each pixel and the correction coefficient. Then, storing these gradation correction data in a memory in association with identification information uniquely determined by each pixel and its gradation value, and a target gradation value of the target pixel and an adjacent pixel and each pixel Of identifying past gradation values of , Possess and selecting extracting the gradation correction data, each corresponding to the identified tone values from said memory, and said memory, a predetermined individual pixel and the gradation value add
The first memory stored in association with the response value and the pixel in advance.
And the gradation correction data generated for each gradation value
The second stored in association with the identification information of the gradation value of each pixel
And a memory for selecting and extracting from the memory.
Identification information of the pixel based on the elementary gradation value and the type of the pixel
And the gradation correction data related to the generated identification information.
Data is selectively extracted from the second memory.
Tone value correction method for.