JPS63151469A - Density irregularity correction apparatus of thermal recording apparatus - Google Patents

Abstract

PURPOSE:To correct the density irregularity of a thermal recording apparatus, by a method wherein the information quantity of density irregularity data is reduced to almost 1/4 input density data and, further, the density correcting operation corresponding to a gradation level shown by the input density data is performed on the basis of said density irregularity data. CONSTITUTION:When density irregularity is taken out while paying attention only to the variation component from a reference density level, density irregularity data can sufficiently hold the smoothness corresponding to almost 8 bits on the basis of 6-bit information quantity becoming 1/4 8-bit information quantity. Therefore, the density irregularity data h(n) stored in a memory circuit 21 is set to 6-bits. Next, an operation circuit 22 is constituted of an ROM table, and the 6-bit density irregularity data from the memory circuit 21, the 8-bit density data from a line memory 13 and the 2-bit color code signal from an input terminal 23 are respectively supplied to the operation circuit 22 and predetermined operation is performed to form 8-bit correction data which is, in turn, outputted to a line thermal head control circuit 16.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a density irregularity correction device for a thermal recording device, and particularly to a device for correcting density irregularities in a thermal recording device, and in particular, a device for correcting density irregularities in a thermal recording device. The present invention relates to an edge 1α unevenness correction device for a thermosensitive recording device that corrects density unevenness according to density unevenness.

2. Description of the Related Art Conventionally, thermal transfer type thermal recording devices have been used as hard copy devices for still images for business or consumer use, such as copying machines, facsimile machines, and video printers.

This thermosensitive recording device has a configuration as shown in FIG. Here, the ink film 1 as a transfer paper has a polyester film 2 coated with heat-melting ink or heat-sublimable ink 3 to a predetermined thickness of, for example, 5 to 6 μm.

The recording paper 4 is conveyed along with the ink film 1 in the direction of the arrow by the roller 5, with its recording surface facing the ink 3 surface of the ink film 1. A line thermal head 6 is provided opposite the roller 5 and is in contact with the back surface of the ink film 1.

The line thermal head 6 includes n (n is a natural number) heating resistors R1 to R, which are not shown, on a ceramic substrate.
η are formed in a line, and the ink 3 of the ink film 1 in the portion corresponding to the energized heating resistor is melted and transferred onto the recording paper 4. After passing through the line thermal head 6, the ink film 1 is guided by rollers 7 and separated from the recording paper 4, and then transferred to a take-up spool (not shown).
The ink film is wound up as a used ink film 1a.

The transferred ink 3a remains on the printed recording paper 4a. For convenience of illustration, the transferred ink 3a is shown as having a large area, but it actually consists of a collection of small dots.

One dot is formed by a negative heating resistor element, and the size of the negative dot is determined by the duration of a constant current flowing through the heating resistor element. The shading, or gradation, of the printed figure is determined according to the size of each dot.

However, in the line thermal head 6, there are variations in the resistors and variations in their surface shapes that occur during the manufacturing process of each heating resistor R1 to Rη, and the collector-emitter saturation voltage V of the drive transistor for driving each heating resistor.
Due to variations in c E (sat), etc., temperature unevenness occurs in the printing results.

In order to correct the above-mentioned temperature unevenness, a density unevenness correcting device for a thermal recording apparatus as shown in FIG. 6 has conventionally been used. In FIG. 6, n pieces of density unevenness data of, for example, 8 bits due to variations in the resistance values of the heating resistors are stored in advance in the memory circuit 11, corresponding to the addresses of the heating resistors R1 to RTI. has been done.

On the other hand, to the input terminal 12, for example, 8-bit density data indicating the density of each pixel (each dot) of the image to be transferred is sequentially supplied. The line memory 13 sequentially stores, for example, density data for -lines.

The address generation circuit 14 generates an address signal corresponding to the address of each heating resistor and supplies it to the storage circuit 11 and line memory 13, and generates 8-bit density unevenness data and 8-bit density unevenness data corresponding to the above-mentioned - heating resistor. Temperature data, for example, on the heating resistor R+.

R2, . . . , Rη are sequentially read out to the arithmetic circuit 15 in this order.

The performance circuit 15 is a read-only memory (ROM) or a random access memory (ROM) with a data manual function.
RAM), and performs a predetermined operation such as multiplication on the incoming temperature data based on the density unevenness data to generate 8-bit correction data. Here, if the notation circuit 15 is realized by a ROM table in which correction data is stored in advance, the input density data and temperature unevenness data are used as address inputs, and the addressed correction data is read out. This correction data corrects the density unevenness and also corrects the actual recorded density! It is set in advance so that the relationship with the third degree data is a straight line or a predetermined curve.

The line thermal head control circuit 16 controls the energization time of a constant current to the heating resistor to be transferred based on the input correction data. As a result, good recording without temperature unevenness is performed.

FIG. 7 shows an example of a temperature characteristic diagram of the transfer paper ink layer or the coloring layer of thermal paper (recording paper) due to heat generated by the line thermal head 6. In this case, for the sake of explanation, the heating resistors RA and R have two types of temperature characteristic curves Δ and B, respectively, due to variations in resistance values and the like.

It is assumed that there are in one line thermal head. In addition, in FIG. 7, T rcr indicates the backflow humidity Iff, and the ink does not melt until the temperature of the transfer paper or thermal paper reaches the sublimation temperature T ref due to the heat generated by the heating resistor RA and R day. No transcription occurs.

Therefore, the time Q in characteristic A and the time in characteristic B do not indicate non-transfer periods.

In this case, if the current is applied for the current application time a, the sublimation temperature T
The transfer period in which printing is actually performed beyond ref is 1 for characteristic A, and 3 for characteristic B. Furthermore, if the concentration level is changed and the current is applied for the current application time d, the sublimation temperature T r
The transfer period during which printing is actually performed beyond ef is characteristic A.
In this case, it becomes e, and in characteristic B, it becomes f.

Conventionally, the arithmetic circuit 15 generates a correction coefficient based on, for example, density unevenness data, and the correction data is the result of multiplying the density data by a single fixed correction coefficient for each heating resistor.

Problems to be Solved by the Invention However, in the above-mentioned conventional density unevenness correction device for a thermal recording device, the input signal data of the arithmetic circuit 15.

Since the input density unevenness data and the output correction data are all expressed in 8 bits, the arithmetic circuit 15 uses, for example, 5 bits.
There was a problem in that a ROM with a large capacity of 12 kbit was required, resulting in an increase in cost.

In addition, in FIG. 6, since the transfer period during which printing is actually performed is S, C (or E, F), correction of temperature unevenness should originally be performed only for this transfer period. In the case of the conventional uniform east exit using a fixed correction coefficient, correction is performed for the energization times a and d including the non-transfer period, resulting in inaccurate correction.

Furthermore, since characteristics A and B are curves each having a certain curve, the ratio of the transfer period described above varies depending on the density level.
As shown in b and f/e, there is a drawback that density unevenness cannot be sufficiently corrected by multiplication by a single correction coefficient that has no relation to the conventional i11 degree level. .

As a method to improve the above drawbacks, the non-transfer period q and h
One possible method is to uniformly add data corresponding to , to the temperature data. That is, if the voltage applied to the line thermal head is constant, the rise in heat generation will be constant for the same heating resistor regardless of its density data, so density unevenness can be corrected by the above addition.

However, even if the energization time is made uniform by the above method, the heat generation states of the heating resistors RA and Re during the transfer period differ, and, for example, the heat generation state at the maximum temperature changes depending on the input density data. Therefore, there is a problem in that the uniform addition method described above does not sufficiently correct density unevenness.

Therefore, the present invention sets the amount of information of the 'Ia degree unevenness data to approximately 1/4 of the input density data, and further uses this temperature unevenness data to perform a density correction calculation corresponding to the gradation level indicated by the input Q degree data. It is an object of the present invention to provide a temperature unevenness correction device for a thermosensitive recording device that solves the above problems.

Means for Solving the Problems The density unevenness correction device for a thermal recording device according to the present invention includes a storage means for storing Fuchimaro unevenness data in advance, and a correction calculation for the density data based on the density unevenness data. It is comprised of a calculation means for generating correction data, and a control means for controlling the energization time of each heating resistor to be transferred based on the correction data.

Effect: The above-mentioned density unevenness data indicates a fluctuation component of recording density with respect to a reference Fuchimaro due to a plurality of heating resistors arranged in a line constituting a line thermal head. The calculation means is supplied with density data indicating the temperature to be recorded by each heating resistor and density unevenness data from the storage means. The calculation means performs a correction calculation σ between the correction coefficient generated based on the density unevenness data and the density data, and generates correction data for each heating resistor.

Thereafter, the control zero means largely controls the energization time of each heating resistor to be transferred based on the correction data. This corrects temperature unevenness.

Embodiment FIG. 1 shows a block system diagram of an embodiment of a depth unevenness correction device for a thermal recording apparatus according to the present invention. In the figure, the same components as those in FIG. 5 are denoted by the same reference numerals, and the explanation thereof will be omitted. Here, before explaining the block system shown in FIG. 1, the m1 degree unevenness data stored in the storage circuit 21 will be explained in conjunction with FIG.

The density unevenness data is set by measuring the printing results in advance, prior to the actual printing operation. Here, a certain recording density (
Density data corresponding to the reference density) DR is input into the thermal recording device, the line thermal head is energized for a predetermined period of time, and each heating resistor is adjusted to the target recording density DR of the recording density actually recorded on the recording paper. Fluctuation components for each R1 to RTI are measured. This fluctuation component corresponds to the variation in the resistance value of the heating resistor that causes density unevenness, so this fluctuation component is stored in the storage circuit as density unevenness data h(n) unique to each heating resistor. 21 in advance.

By the way, the density unevenness in the sub-scanning direction (line direction) of the line thermal head that generally occurs during recording is the total density level (i.e., the maximum density level), even including the difference in temperature distribution between the edge and center of the line thermal head. It is about 174 (tonal density level). Here, if the total temperature level that can be expressed is assumed to be 8 bits, and if m degrees unevenness is extracted by focusing only on the variation component from the reference density level as described above, the density unevenness data will be 1/4 of the information amount of 8 bits. For practical purposes, 6 bits of information can be used to maintain smoothness equivalent to approximately 8 bits. Therefore, the density unevenness data h (n) stored in the storage circuit 21 is 6 bits in this embodiment. Next, the readout circuit 22 is composed of a ROM table, etc., like the readout circuit 15, and stores 6-bit density unevenness data from the storage circuit 21 and 8-bit density data from the line memory 13. and input terminal 2
The 2-bit color code signals from 3 are respectively supplied, perform predetermined calculations to be described later, generate 8-bit correction data, and output the generated 8-bit correction data to the line thermal head control circuit 16.

Here, the above-mentioned 2-bit color code signal is not necessarily necessary, and in that case, since the density unevenness data has been changed from 8 bits to 6 bits compared to the conventional case, the required capacity of the arithmetic circuit 22 is Capacity of circuit 15 51'2 k
It becomes 128 kbit of 174 bits.

By the way, the above color code signal represents each of the three recording primary colors Y (yellow), 1M (magenta), and C (cyan) depending on its value.For example, when recording a color image sequentially, it is used to balance each color. This is used to perform gain adjustment for each color. In other words, the three primary colors Y, M, and C have different input levels (densities to be transferred) and output levels (as shown in FIG. There is a drawback that good color reproduction cannot be obtained because the actual recording density differs from the actual recording density. Therefore, the arithmetic circuit 22 performs predetermined gain adjustment calculations for each color, as shown in FIG.
), correction is performed so that the input and output levels of the density data of each color match.

In this way, in this embodiment, the arithmetic circuit 22 is provided with a data conversion function for correcting the recording density linearity of each color in color recording without increasing the capacity ω.
Furthermore, density characteristics that differ between each color can also be corrected.

The arithmetic circuit 22 outputs correction data obtained by multiplying a high-density portion by a low-level correction coefficient (or vice versa) according to the density unevenness data, and then A detailed explanation will be given in conjunction with FIG.

FIG. 4 is a schematic diagram of FIG. 7.

In the figure, ■ and ■ are the heating resistors RA, respectively.

The temperature characteristic curve of Re is shown. Further, for convenience of illustration and explanation, temperature characteristics (1) and (2) are shown as approximately linear characteristics, but in reality they have curves as shown in characteristics A and B in FIG.

Here, it is assumed that the heating resistor R8 is a resistor having a density of 14 ty with a variation in the lowest concentration, and the time constant of heat radiation (cooling) for both characteristics 1 and n is Ic=a.

/C0 (however, aO is the maximum temperature reached by the heating resistor R,
Co indicates the heat dissipation time). Now, the energization time is Do, and the heating time constant at the same applied energy is τ.
A (=80/Do), 1 day (=bo/Do), left, maximum temperature a of heating resistors RA and RB. +b
O is as shown in equations (1) and (2), respectively.

ao = Is Do - (1
) bo = 18 Do −Q
) By the way, the four-way temperature is Y (equivalent to +n T ref)
And characteristic 1. The maximum temperature arrival time of II is A+ respectively.

Assuming that the times at which the sublimation temperature is reached during BIN heating are A21B2, and the times at which the sublimation temperature is reached during heat dissipation are A3°G3, characteristic 1. The time during which the gastric temperature is exceeded at I, that is, the time at which recording is actually performed, eo and do are respectively (3
) and (4).

eo = (31+e2= (bo-Y)/box(D
o + (t)o Co ) / ao ) −Q
;) do = d+ + dz = (ao-Y)/ao
x(Do+Co)...(4)
Here, the triangular parts At A2 A3 and B in FIG.
+82 The areas SA and G8 of G3 indicate the energy applied to the heating resistors RA and R8, respectively, in excess of the sublimation humidity Y, and these values are given by the following equations.

S8-(1/2)・(ao-Y)・d0= (1/2)
・(ao Y)2 ・(Do +Co)/ao
...■So = (1/2)
・(bo Y) ・e.

=(1/2)・(bo−Y)2・(Do+(bo
Co) / ao) / b o -(6
) Now, determine the energization time of the heating resistor R^ based on the reference heating temperature of the heating resistor Ra. A case of correcting from bl to bl will be explained. Here, heating resistors RA, RB
The ratio of the above-mentioned areas S^ and Ss shall be expressed by the ratio of the above-mentioned areas S^ and Ss, and the energization time of the heating resistor R^ after correction is D.
If the recorded temperature of 17 degrees when 1 is the same as 81 degrees obtained by heating the heating resistor Ra for the energizing time Do, then the following relational expression is established from equations (5) and (6). do.

(ao −Y) 2 ・(DI +Co )/aO=
(t)o Y) 2 ・ (Do +
When the above equation (7) of (bo Co )/ao )bo... is rearranged with respect to Dl, it becomes as follows.

DI-(ao/bo)・(bo-Y)2　・D.

/(ao-Y)2+((bo Y)2/(ao Y
)21)・G.

=(τA/τB)・(τaDo Y)2・Do/(τ
ADOY)2 + ((τaDo Y)2/(τADO-Y)2-1)
-(τA Do /τc) −(B) In the above explanation, the correction sieve regarding the two heating resistors RA and Re was obtained, but below, a case where the above formula (8) is generalized will be explained. Here, the heat generating resistor Rs is used as a reference for correction, and the energization time of each of the heat generating resistors R+-Rη constituting the line thermal head 6 is corrected instead of the heat generating resistor RA. Now, let D be the energization time corresponding to the 11 degree data of each heating resistor, let τη be the heating time constant of each heating resistor, and furthermore, let D be the energization time corresponding to the 11 degree data of each heating resistor.
1 Anti-mura data h (n) and correction coefficient G+ (D)
, G2 (D) shall be defined as follows.

h (n) −rTllrday −(
9) G+(D)=(τBD-Y)2/(τη-Y)2・
...(10) G2(D)=((τeD-Y)2/(τnD-Y)2
-11(τAD/τC) (11) When the above equation (8) is generalized using the above equations (9) to (11) and the corrected energization time D(n) is obtained, (12) It becomes as shown in the formula.

D(n)-D-G+ (D) ・h (n)+02(
D) ... (12) The above-mentioned energization time is a value determined in accordance with λ1 of the concentration data of 8 pips 1- for each heating resistor from the line memory 13. On the other hand, the heating time constant τη is a value measured in advance for each heating resistor, and the sublimation temperature Y, reference heating time constant τB, and heat radiation time constant τC are each known values, so the correction coefficient 01 (D ) and G2 (D) are values uniquely determined according to the concentration data D for each heating resistor.

In this way, Equation (12) uses density unevenness data h (n) that is fixed for each heating resistor, and correction coefficients G+ (D) and G2 (D
), the correction calculation is performed.

Therefore, in this embodiment, more accurate correction can be achieved than in the conventional method, which is based on simple tightening or multiplication of m-degree unevenness data, or calculation using a fixed correction coefficient. As mentioned above, the change in heat is as shown in Figure 4 (although some correction is necessary because it is not linear).
The general formula of equation 12) is not compromised.

Note that the present invention is not limited to this embodiment, and the correction calculation in the calculation circuit 22 is not necessarily limited to the general formula (12), and it goes without saying that other correction calculations may be performed. It is.

Effects of the Invention As described above, according to the present invention, since the information group of the m degree unevenness data is approximately 174 times the input density data, the capacity of the memory for the correction calculation table from which the correction calculation results are read out using both data as addresses can be reduced. In addition, since the density correction calculation corresponding to the gradation level indicated by the input density data is performed using the 'Q degree unevenness data, correction of density unevenness data that differs depending on the F15a level can be performed with high precision and even roughness can be reduced. Another advantage is that the specification for variations in the line thermal head can be relaxed with the FF1 configuration, thereby making it possible to reduce the cost of the line thermal head.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the device of the present invention;
Figure 2 is a diagram for explaining 111 unevenness data, Figures 3 and 4 are diagrams for explaining the density correction method in the apparatus of the present invention, and Figure 5 is a diagram for explaining the configuration of a general thermal recording apparatus. 6 is a block system diagram showing an example of a conventional device, and FIG. 7 is a temperature characteristic diagram of an example of a line thermal head. 12... Density data input terminal, 13... Line memory, 14... Address generation circuit, 16... Line thermal head control circuit, 21... Storage circuit, 22...
... Arithmetic circuit, 23... Color code signal input terminal. Special Engineering 1 Applicant: Victor Company of Japan] Figure 1 Figure 2 Address Figure 3 Input Level Input Level jI4 @ Figure 5

Claims (3)

[Claims] (1) A storage means for storing density unevenness data in advance corresponding to each heating resistor, which indicates a fluctuation component of recording density with respect to a reference density due to a plurality of heating resistors arranged in a line constituting the line thermal head; , density data indicating the density to be recorded by each heating resistor and the density unevenness data from the storage means are respectively supplied, and a correction calculation is performed between the correction coefficient generated based on the density unevenness data and the density data. and a control means for controlling the energization time of each heating resistor to be transferred based on the correction data from the calculating means. A density unevenness correction device for a thermal recording device, characterized by: (2) The calculation means performs a correction calculation based on the density unevenness data of m (however, m is a natural number smaller than l) bits on the density data of l (where l is a natural number) bits. , 1 bits of the correction data is generated. 2. The density unevenness correction device for a thermal recording device according to claim 1, wherein the correction data is of 1 bit. (3) The calculating means generates a different correction coefficient for each level of the density data based on the density unevenness data, and calculates the correction coefficient and the density data for each heating resistor. A density unevenness correction device for a thermal recording device according to claim 1, wherein correction data corresponding to the recording density level is generated.