JPH1148517A - Method for correcting image density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for correcting an image density whereby a density irregularity because of a temperature change is eliminated and images can be thermally recorded to a recording medium favorably. SOLUTION: A patch based on the same density data is formed at each position in a sub scan direction of a recording medium (step S1). A density is measured (step S2). A relationship of measured densities to positions is obtained (step S3). Thereafter, a relationship of the measured density to a reference density is obtained for every position in the sub scan direction from the above relationship (step S4). A density correction amount is obtained from the relationship (step S5), and a density collection LUT(look-up table) is set (step S6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting image density in an image recording apparatus for thermally recording an image on a recording medium.

[0002]

2. Description of the Related Art For example, after image information is recorded on a donor film using a light beam, a recording medium, which is an image receiving sheet, is overlaid on the donor film, and the image information is thermally developed by uniformly heating them. There is an image recording apparatus for transferring the image to a recording medium. This image recording apparatus is used as a dry developing printer that is easy to handle. Also,
An image recording apparatus that directly records image information on a thermosensitive recording medium using a thermal head is also used.

In this case, in order to record image information having a desired density, it is necessary to control the heating temperature of the donor film or the heat-sensitive recording medium with high accuracy. Therefore,
For example, in an image recording apparatus using a donor film, conventionally, a heater is divided and arranged in the main scanning direction of the donor film, and a temperature at each main scanning position is monitored by a sensor and fed back to the heater, thereby providing a donor. The film temperature is adjusted to be uniform.

Meanwhile, since the heat of the heater is absorbed by the donor film, a temperature change occurs in the process of transporting the donor film in the sub-scanning direction, and density unevenness of the developed image occurs in the sub-scanning direction. There is a problem that goes wrong. In particular, the longer the recording distance in the sub-scanning direction is, the more remarkable the effect of temperature fluctuation on the image is.

[0005] It is difficult to control the temperature of the heater with high accuracy and speed in real time, and it is impossible to completely avoid temperature fluctuation in the sub-scanning direction.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems, and has been made in consideration of the above-described problems, and has been made in consideration of the above circumstances. An object of the present invention is to provide a density correction method.

[0007]

An image density correcting method according to the present invention is an image density correcting method for an image recording apparatus for thermally recording an image on a recording medium, wherein the recording is performed based on the same density data. Thermally recording a plurality of test images at different recording positions on a medium; measuring densities of the plurality of test images to obtain a measured density for a recording position; and measuring the measured densities of the plurality of test images with the density data. Calculating density correction data for correcting the density to a desired density with respect to the recording position of each of the test images. It is characterized by correction.

[0008] In this case, the density fluctuation caused by the temperature difference depending on the position on the recording medium is corrected by the density correction data.

[0009]

FIG. 1 shows a schematic configuration of a heat developing apparatus 10 to which an image density correcting method according to the present embodiment is applied.

The thermal developing apparatus 10 includes a photosensitive material magazine 12 for storing a donor film F, which is a photosensitive material wound in a roll, and a receiver for storing an image receiving film G, which is an image receiving material wound in a roll. A material magazine 14, an exposure unit 16 for recording an image as a latent image on a donor film F using a laser beam L, and a control unit 18 for controlling the exposure unit 16
A water application section 20 for applying dampening water to the donor film F on which an image is recorded, a heat development transfer section 22 for superimposing the donor film F and the image receiving film G to perform a heat development transfer process, and a heat development transfer A donor film collecting section 24 for collecting the processed donor film F and a tray 26 for storing an image receiving film G on which an image as a visible image has been transferred are formed, and these are housed in a casing 28.

The donor film F is adapted to make each of the C, M, and Y dyes in a colorable state in response to the laser beam L corresponding to the image information. And a cutter 30 for cutting the donor film F to a predetermined length. The image receiving film G receives an image of the dye of the donor film F that has been colored by being heated, and a cutter 32 that cuts the image receiving film G is disposed near the exit of the receiving material magazine 14 that stores the image. .

The exposure unit 16 includes three laser diodes that output three types of laser beams L having different wavelengths based on the LD control data from the control unit 18, and each laser beam L
And a scanning optical system that scans in the main scanning direction of the donor film F conveyed in the sub-scanning direction.

The thermal development transfer section 22 includes driving rollers 34, 3
6, two sets of endless belts 38, 40 rotated by
Is provided. These endless belts 38, 40 include
Preheating plates 42 and 44 facing the upper portions on the supply port side of the donor film F and the image receiving film G are provided.
Heating plates 46 and 48 facing the lower portions of the preheating plates 42 and 44 are provided. In this case, one preheating plate 42 and the heating plate 46 are pressed by the springs 50 and 52 toward the other preheating plate 44 and the heating plate 48. A peeling claw 54 for peeling the donor film F from the image receiving film G is provided at the lower end of the thermal development transfer unit 22.

FIG. 2 is a block diagram showing the main components of the control unit 18 shown in FIG. In this case, the control unit 18 converts the R, G, and B image data supplied to the thermal developing device 10 into C, M, and Y density data in a density conversion LUT (lookup table) 56, and then , Density correction L
In a UT (look-up table) 58, correction is performed due to a temperature change of the density data with respect to the sub-scanning position y, and in a LD (laser diode) control data conversion LUT (look-up table) 60, the corrected density is corrected. A process of converting the data into LD (laser diode) control data is performed.

The thermal developing apparatus 10 to which the image density correcting method of the present embodiment is applied is basically configured as described above. Next, an image density correction method in the thermal developing device 10 will be described with reference to the flowchart of FIG.

First, in the thermal developing device 10, n sets of image data R1, G1, B1 to Rn,
A test chart T shown in FIG. 4 is created using Gn and Bn (step S1).

That is, in the control section 18 of the heat developing apparatus 10, the image data R1, G1, B1 to Rn, Gn, B
n is the density conversion DUT 56 and the density data D of C, M and Y
After being converted into C1, DM1, DY1 to DCn, DMn, and DYn, the LD control data conversion LUT 60 converts the data into LD control data for controlling the laser diode. This L
The D control data drives each laser diode included in the exposure unit 16 and irradiates the donor film F derived from the photosensitive material magazine 12 with the laser beam L,
A test chart T as a latent image is formed. The donor film F on which the test chart T is recorded is cut into a predetermined length by the cutter 30, is conveyed to the water application section 20 and is applied with dampening water, and is then taken out of the receiving magazine 14 to be cut out by the cutter 32. Is superimposed on the image receiving film G cut to a predetermined length, and conveyed to the thermal development transfer unit 22.

The donor film F and the image receiving film G conveyed to the thermal development transfer section 22 are preheat-treated by being sandwiched between the preheating plates 42 and 44. Next, the donor film F and the image receiving film G are
Endless belts 38, 4
0, and the entire surface is heated substantially uniformly. In this case, the image of the test chart T recorded as a latent image on the donor film F is visualized by the heat given by the heating plates 46 and 48, and then the visualized image is transferred to the image receiving film G. You.

The image receiving film G to which the image of the test chart T has been transferred is separated from the donor film F by the separating claw 54 and then stored in the tray 26. On the other hand, the donor film F peeled off from the image receiving film G is collected by the donor film collecting section 24.

Here, as shown in FIG. 4, the test chart T includes the respective positions y1 to y in the sub-scanning direction of the image receiving film G.
m, density data DC1, DM1, DY1 to DCn, D
This is formed of n sets of gray patches based on Mn and DYn.

Next, the measured densities DC, DM, and DY of each patch of the test chart T created as described above are obtained for each position y1 to ym in the sub-scanning direction using a densitometer (step S2). . In this case, the temperature on the image receiving film G on which the test chart T is formed becomes the position y1 in the sub-scanning direction.
Ym, the same density data DC
1, even if the patches are based on DM1, DY1 to DCn, DMn, and DYn, the measured densities DC, DM, and DY differ.

Therefore, the relationship between the measured densities DC, DM, and DY of each patch with respect to the positions y1 to ym is expressed by density data DC.
1, DM1, DY1 to DCn, DMn, and DYn are approximated by a polynomial and approximate curves fC1, fM1, fY1 to fC
n, fMn, and fYn are obtained (step S3). FIG.
Are approximate curves fC1, fM1, fY1 to fCn, fM
n and fYn are plotted, the density of the patch differs depending on the positions y1 to ym in the sub-scanning direction, and the approximate curves fC1, fM1, fY1 to fY depend on the density level.
The shapes of Cn, fMn, and fYn are also different.

Next, the approximate curves fC1, fM1, fY
1 to fCn, fMn, and fYn, the density data DC at the positions y1 to yj in the sub-scanning direction divided into j pieces.
1. The relationship between DM1, DY1 to DCn, DMn, and DYn and the measured concentrations DC, DM, and DY is obtained, and this relationship is approximated by a polynomial. Approximate curve gCy
1, gMy1, gYy1 to gCyj, gMyj, gYy
j is obtained (step S4). FIG. 6 shows an approximate curve gCy.
1, gMy1, gYy1 to gCyj, gMyj, gYy
j is plotted.

The approximate curve gC obtained as described above
y1, gMy1, gYy1 to gCyj, gMyj, gY
Using yj, the density correction amounts ΔDC, ΔDM, and ΔDY are obtained as ΔDC = DC0−DC ΔDM = DM0−DM ΔDY = DY0−DY for each of the positions y1 to yj in the sub-scanning direction (step S5).

The density correction amounts ΔDC, ΔDM,
The density correction LUT 58 is set from ΔDY (step S6). That is, the density correction LUT 58 stores the reference densities DC0, DM0, and DY0 in accordance with the scanning position y.
Data to be converted into ΔDC, DM0−ΔDM, and DY0−ΔDY are set.

After setting the density correction LUT 58 as described above, an arbitrary image is recorded in the heat developing device 10. In this case, the control unit 18 controls the image data R, G, B
Is converted into C, M, and Y density data by a density conversion LUT 56, and then this density data is corrected by a density correction LUT 58 according to the sub-scanning position y. Thereafter, the corrected density data is converted into LD control data by the LD control data conversion LUT 60. The laser diode is driven by the LD control data, and a latent image is recorded on the donor film F. Then, the donor film F conveyed to the thermal development transfer unit 22 is developed by being heated by the heating plates 46 and 48, and the image is transferred and recorded on the image receiving film G. In this case, the image receiving film G
Is adjusted in consideration of temperature unevenness in the sub-scanning direction in the thermal development transfer unit 22, so that an image having extremely high density can be obtained.

In the above-described embodiment, the correction for the temperature unevenness in the sub-scanning direction is performed. However, the density correction amount in the main scanning direction is obtained, and the correction is performed in both the main scanning direction and the sub-scanning direction. Correction can also be performed.

If the temperature of the thermal development transfer section 18 does not depend on the environmental temperature, a density correction LUT 58 is obtained before shipment of the thermal development apparatus 10, and the density correction LUT 58 is obtained.
The UT 58 can be set as a fixed LUT.

Further, as the test chart T, FIG.
Instead of forming the gray color patches shown in FIG. 3, single density patches of C, M, and Y are formed using the density data DC1, DM1, DY1 to DCn, DMn, and DYn, and the respective densities are measured. It may be.

[0030]

As described above, according to the image density correcting method of the present invention, an image having a desired density can be formed on a recording medium without performing complicated temperature control and image correction during recording. Thermal recording can be easily performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a heat developing apparatus to which an image density correction method of the present invention is applied.

FIG. 2 is a block diagram of a main part configuration of a control unit shown in FIG.

FIG. 3 is a flowchart illustrating an embodiment of an image density correction method according to the present invention.

FIG. 4 is an explanatory diagram of a test chart used in an embodiment of the image density correction method of the present invention.

FIG. 5 is a relationship diagram between measured densities of the test chart shown in FIG. 4 and positions in the sub-scanning direction.

FIG. 6 is a graph showing a relationship between a reference density and a measured density of a test chart.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Thermal developing device 12 ... Sensitive material magazine 14 ... Receiving material magazine 16 ... Exposure part 18 ... Control part 20 ... Water application part 22 ... Thermal development transfer part 24 ... Donor film collection part 26 ... Tray 28 ... Casing 42, 44 ... Preheating plates 46, 48 Heating plate 54 Peeling claw 56 Density conversion L
UT 58: density correction LUT 60: LD control data conversion LUT F: donor film G: image receiving film T: test chart

Claims (4)

[Claims] An image density correction method in an image recording apparatus for thermally recording an image on a recording medium, wherein a plurality of test images are thermally recorded at different recording positions on the recording medium based on the same density data. Measuring the densities of the plurality of test images to obtain a measured density for a recording position; density correction data for correcting the measured densities of the plurality of test images to a desired density for the density data; Determining the density data in relation to the recording position of each of the test images, and correcting desired density data with the density correction data selected according to the recording position of the image. 2. The method according to claim 1, wherein the plurality of test images thermally recorded based on the same density data are further thermally recorded based on different density data, and the plurality of test images are thermally recorded based on different density data. An image density correction method characterized by obtaining density correction data. 3. The image density correcting method according to claim 1, wherein the relationship between the measured density and the recording position is obtained as a polynomial approximation curve. 4. The image density correction method according to claim 1, wherein a relationship between the density correction data and the measured density is obtained as a polynomial approximation curve.