JPS63153140A - Signal converting method in duplication of medium contrast image - Google Patents

Abstract

PURPOSE:To more well copy the image of a manuscript, by a method wherein the input range of an medium contrast image is compressed and shifted when the reproduction range of duplication output is different from the input range of the medium contrast image to reconstitute a signal converting table which is, in turn, set to a signal converting table for duplication. CONSTITUTION:When the reproduction lens of the duplication table of a copier is different from the input range of the reading medium contrast image of a manuscript with respect to a lookup table set automatically or by other method, that is, when the input ranges of an image to be duplicated are 301, 302, 303 with respect to the reproduction range 300 of the duplicator of a range of the max. value (e.g., density : 1.8) at the min. value 300 Min (e.g., density : 0.03), the following reconstitution is performed to set a gradation converting table. Like the input range 301, when both of the min. value 301 Min (e.g., density : 0.01) and the max. value 301 Max (e.g., density : 2.0) are out of the reproduction range 300, data are respectively compressed so that the min. value 301 Min becomes 300 Min and the max. value 301 Max becomes 300 Max.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a signal conversion method in image copying of a copying machine, a thermal transfer image recording device, a laser beam printer, etc. using a heat-developable photosensitive material.

(Technical background of the invention and its problems).

When an image of a color document, etc. is scanned and read, converted into an electrical signal, processed, and scanned onto a photosensitive recording material using a recording bed to record a halftone image and then copied, the image is faithfully copied to the scanned image. There is a need to. The characteristics of photosensitive recording materials vary depending on the manufacturer, lot, etc. Therefore, if recording is performed under the same conditions, an image that is less faithful to the original image will be recorded.

For this reason, in the past, knobs or keys were provided to adjust the exposure amounts of the three primary colors, and a gradation table for signal conversion was set while checking the copy result. Therefore, each time the recording material or the like changes, the settings must be adjusted, which is cumbersome and requires a great deal of time and effort. Further, if the recording output reproduction range of the copying apparatus is different from the manual range of the image of the original to be copied, it is not possible to record a high-quality image.

For example, if the minimum density of the recorded output is higher than the minimum density of the human image, the highlight tones will be lost. In general, in image formation, it is important that the gradation does not change over the entire depth range. Furthermore, it is desirable to reproduce using a wide gradation range.

(Object of the invention) This invention was made under the above circumstances,
An object of the present invention is to enable the human input range of the original image to be copied to be included in the reproduction range of the copy output of the copying apparatus on the signal conversion table even if the characteristics of the recording material change. An object of the present invention is to provide a signal conversion method in halftone image copying that enables better copying.

(Summary of the Invention) The present invention relates to a signal conversion method for scanning and reading a halftone image, converting it into an electrical signal for processing, and copying the halftone image by scanning a recording material with a recording head. If the reproduction range of the copy output is different from the manual range of the halftone image, the intermediate value is adjusted so that the minimum value or maximum value of the manual range, or the minimum and maximum values are within the reproduction range. Compressing the manual range of tone images,
The signal conversion table is reconstructed by shifting and used as the signal conversion table for copying.

(Embodiments of the Invention) First, a copying machine using a photothermographic material to which the present invention can be applied will be described with reference to FIGS. 1 and 3.

A copying machine 10 using a heat-developable photosensitive material (hereinafter simply referred to as a copying machine) houses a heat-developable photosensitive material 16 on which a machine base 12 and a hemagashin 14 are mounted. is pulled out from its outer circumference, and the cutter 1
8 and cut into a predetermined length, an exposure drum 20, which will be described later.
wrapped around the outer circumference (in the six directions of arrows). exposure tram 20
An exposure head 22 as a recording head is correspondingly provided on the outer periphery of the photothermographic material 16, and after exposure, the exposure drum 20 is reversed and the photothermographic material 16 is removed by a scraper 24! 'J let go,
The water is sent to the development transfer section 28 via the water application section 26.

On the other hand, the image receiving material 32 housed in the tray 30 is sent to the development transfer section 28 and overlapped with the photothermographic material 16, and then heated by a heater in the development transfer section 28. As a result, the heat-developable photosensitive material 16 is developed, and the developed image is transferred to the image-receiving material 32. After the transfer is completed, the photothermographic material 16 is stored in a waste tray 38 through the female part 36, and the image receiving material 32 is sent out through the drying part 40 to a take-out tray 42 provided on the side. It has become.

An image reading unit 100 is provided at the top of the copying machine 10 to scan and read the image of the original f height 101 placed thereon.
The original Ji I 01 is shown in the figure and is placed on a glass portion 103 of a document table 102 that is movable in the E direction for scanning.

Below the glass part 103, light of the three primary colors of RGB is applied to the original 10.
A light source unit 110 is disposed to irradiate the original 1i 101 and receive the reflected light, and inside the light source unit 110 there is a lamp 110 that emits RGB three primary color lights to irradiate the original 1i 101, and a lamp ill that irradiates the original 1i 101 with light reflected from the original 101. A mirror 112 is provided to receive and reflect the RGB light. The light reflected from the mirror 112 of the light source section 110 is transmitted to the mirrors 121 and 122.
After being reflected, the light is imaged by a lens 123 and received by an image reading element 120 such as a CCD. Image reading element 120
The RGB @ image signals of the original document 101 read by the user are sent to the exposure head 22 after being subjected to predetermined image processing.

As shown in FIG. 2, the exposure head 22 is wound around the photothermographic material 16 and is rotated at high speed around its axis to perform main scanning (in the six directions of arrows). . The exposure head 22 is equipped with a light-emitting element 14 such as a light-emitting device with three primary colors of IIGB, and can perform sub-scanning along a guide bar 46 that is arranged parallel to the exposure head 22 and above the glaze (see the arrow). B direction). A pair of pulleys 48 and 50 are arranged parallel to each other in order to sub-scan the exposure head 22, and a wire 52 is wound around these pulleys 48 and 50. That is, the wire 52
One end is fixed to the exposure head 22, and the middle part is attached to the pulley 4.
8 and 50, and is attached to the exposure head 22 via the tension applying means 54.

For example, the tension applying means 54 has a configuration in which the intermediate portion of the wire 52 is cut and the cut portions are connected by an elastic body such as a tension coil spring, and a predetermined tension is generated in the wire 52. Here, the pulley 48 is connected to a driving means such as a motor (not shown) to serve as a driving pulley, and the wire 50 serves as a driven pulley.

In such a configuration, the photothermographic material 16 in the magazine 14 is cut into a predetermined length by the cutter 18 and then wound around the outer periphery of the exposure drum 20 .

Here, the exposure drum 20 is rotated at high speed in the direction of the arrow by the driving force of a motor (not shown).

Further, the exposure head 22 is sub-scanned by rotating the pulley 48 and moved in the direction of arrow B, and this sub-scanning is performed by the light emitting element 44 only when the pulley 48 is driven clockwise (in the direction of arrow C). do the work. In this way, the rotational force of the pulley 48 acts as a tensile force on the wire 52 arranged linearly between the pulley 48, which has relatively high rigidity, and the exposure head 22, so that the response is good and the vibration due to natural vibration is suppressed. rarely occurs. A wire 5 arranged linearly between this pulley 48 and the exposure head
2 has high responsiveness because appropriate tension is applied by the tension applying means 54. After exposure, the exposure drum 20 is reversed, and the heat-developable photosensitive material 16 is transferred to the scraper 24.
The photosensitive material is peeled off from the outer periphery of the exposure drum 20 and sent to the development transfer section 28 via the water coating section 26 .

On the other hand, the image-receiving material 32 taken out from the tray 30 is sent to the development transfer section 28 and overlapped with the heat-developable photosensitive material 16, so that the emulsion surfaces of both materials are brought into close contact. Here, the development transfer section 28
When the heater inside is heated, the image exposed on the photothermographic material 16 is thermally developed, and then the image is transferred to the image receiving material 32.
transcribed to.

This transfer is carried out reliably because water has already been applied to the emulsion surface of the photothermographic material 16 by the water coating section 26. The heat-developable photosensitive material 16 after transfer is placed in a waste tray 3.
8 and is discarded, and the image receiving material 32 is transferred to the drying section 4.
0 and is taken out to the takeout tray 42.

In the above-described copying machine 10, an original (for example, a color image) 101 placed on the image reading section 100 is photoelectrically read and electrically processed, and then the photothermographic material 16 is exposed by the exposure head 22. The image is recorded by heat development. That is, as shown in FIG.
The original fAxot placed on the original No. 102 of No. 0 is photoelectrically scanned and read by the image reading element 120, and the obtained varnish signal is digitized by the A/D converter 131, and then
It is temporarily stored in the frame memory 132. The one-screen image data stored in the frame memory +32 is sequentially read out, converted into data using a lookup table 130, and
/A converter 133, where it is converted into an analog light amount control signal LC for each RGB, and then manually inputted to the exposure head 22, whereby the image on the original 101 is transferred to the photothermographic material 1.
6. The image recorded on the heat-developable photosensitive material 16 is thermally transferred in the development transfer section 28 as described above, and the transferred image on the image-receiving material 32 is output. Therefore, depending on the settings of the lookup table 130, the relationship between the human image and the recorded image will differ greatly. Therefore, the problem is how to set the lookup table 130.

In this invention, step image recording signals SCI of predetermined gradations of C (cyan), 1M (magenta), and Y (yellow) are outputted from the step signal generation circuit 134 and the reference lookup table 135, and then the step image recording signals SCI are outputted to the D/A converter. 133 to convert it into an analog light control signal LC, the exposure head 22 is driven as described above to sequentially expose the photothermographic material 16 set on the exposure drum 20 in a stepwise manner. In this way, the heat-developable photosensitive material 16 is exposed to light for each of RGB with the amount of light corresponding to the predetermined light amount control signal LC. By developing the heat-developable photosensitive material 16 exposed in this way, a density wedge 200 having gradations for each CMY, as shown in FIG. 4, exposed by a known image recording signal SC1 is created. . The step image recording signal SCI from the lookup table 135 that created this density wedge 200 is sent to the table setting circuit 13.
6 is also manually input and its value is memorized.

Here, the step signal of the step signal generation circuit 134 is converted to D/8 by the lookup table 135.
33. The recording characteristics are converted in accordance with the characteristics of the exposure head 22 and the photothermographic material 16 so that a predetermined density step is obtained when the photothermographic material 16 is developed and processed. It is also possible to calculate this in advance and output it directly from the step signal generation circuit 134. Also, lookup table 1
It is also possible to switch and use the lookup table 130 instead of the lookup table 35.

The test density wedge 200 created in this way is placed on the document table 1 of the image reading unit 100 for calibration.
02 and read it by photoelectric scanning. In this case, as shown in FIG. 5, the density step portion 201 for each CMY of the density wedge 200 is searched, but it is confirmed whether or not the lowest density among the densities of each CMY color is equal to or higher than a predetermined value ε. By this, the black frame line 202 is detected. Then, in order to avoid blurring in the density step portion 201, the read values of an area 203 at a position that is larger than the detected black frame line 202 are integrated (averaged). This integration is performed in order to avoid unevenness due to noise, dust, etc. in the D/D conversion. Furthermore, in order to remove shading unevenness, smoothing as described later is applied to the measurement data.

If there is uneven shading within one screen, the data string (SCi, ID1) in the table may be subjected to smoothing processing. As shown in Figure 8, this includes, for example, 20 points including three points before and after the point of interest (S(:+, ID+)).
Quadratic curve ID = f I (SC) using least squares method for points
, and the coordinates 101 of the point of interest are f, (SC,)
, and then shift the points of interest one by one to obtain smoothed values over all points. In general, such smoothing processing may be performed by simply obtaining a smoothed value over one die point, or may be repeated several times. Therefore, as a condition for determining whether to stop iteratively, we use the smoothed value group (5Ci, fk(SG, )) obtained by the smoothing process for the second time, and (
The smoothed value group obtained by the k-1)th smoothing process (
SC1, f''-' (SCi)) S・Σ(f''(SCI)-f+ (Sc+)+2
and the standard value δ given empirically,
When S becomes smaller than δ, the smoothing process is stopped. In this way, a smoothed human force concentration signal IDC is obtained with respect to the known step tablet signal SC.

In this way, the document table 102 is moved and the light source unit 110 is moved.
For testing (43 degree wedge 20
The read value IDI from the image reading element 120 of 0 is input to the A/D converter 131 . And A/D converter 131
The read values IDD+ (ID+) digitized in are sequentially input to the table setting circuit 136 via the frame memory 132, and each range 203 of the density wedge 200 in FIG.
After being averaged and further smoothed by h%, lookup table! Correspondence is made with the known step image recording signal SC sent from 35 and stored, and a look-up table 130 or C for gradation conversion is made.
It is set to MY @.

The correspondence between the step image recording signal SC and the read value IDD is as shown in FIG. and ask. That is, for the step image recording signals SC1 to SCo as shown in FIG. 7(A), the read values IDC, or IDD of the density wedge 200.

IDD3. ..., In the case of IDDo, continuous reading values IDD1. IDD2. ID
D3.・=, Step image recording corresponding to IDDo SC+, SC+-j, SC2.

502-b, SC3, . . . , SC2 are determined by interpolation (for example, proportional allocation). In this way, the lookup table 130 is set to output continuous read values IDD+, that is, signals SC corresponding to all image information that may be read. In this case, so-called bleeding of the photothermographic material 16 can be eliminated by setting the predetermined value SC□8 of the step image recording signal SCI as the maximum value. In addition, the reading value ■DD
The correspondence relationship below the minimum value IDDIIIo of + is indicated by the broken line A.
The relationship may be determined by estimating the same slope as shown in FIG. This is to ensure stability of the image quality of the copied image against fluctuations in the signal from the reading section.

After processing and smoothing both ends of the data as described above,
If the table data corresponding to all the obtained manual reading values IDDI is set as the lookup table 130, the correspondence with the image actually recorded on the photosensitive material 16 by the exposure head 22 is established, so that the image Reading section 10
0 can also be read and copied by recording a faithful image.

If the reproduction lens of the copy output of the copying device differs from the manual range of the halftone image for reading of the original to be copied for the lookup table set automatically or by other methods as described above, In other words, for the reproduction range 300 of the copying machine ranging from the minimum value 300M+o (for example, density 0.03) to the maximum value (for example, density 1.8) as shown in FIG. 9, the manual range of the image to be copied is 301M+o.
．． 302.30:l, the following reconstruction is performed to create a gradation variation table. Human power range 3
Like 01, the minimum value is 301! I! +n (for example, concentration 0.01) and maximum value 301M, ll (for example, concentration 2
．． 0) are both outside the reproduction range 300, the data is compressed so that the minimum value 301M+n becomes 300M,n, and the maximum value 301M,l,l becomes 300M,X, respectively. This data compression is performed as follows.

Here, select the input range. -11, Set the reproduction range to Oo~
0, 11, and the values of the lookup table 130 corresponding to the reproduction range On to 0IIl are set to SCn to 5C.
Let it be l11. Then, it corresponds to the input range ■A~In, and corresponds to the reproduction range 0°~OIN, and the reproduction range 0°~In.
The values of the look amplifier table 130 corresponding to ° to 0□ are SCo' to SCl. Thereafter, the corrected values SC,' (P-n~m) of the lookup table 130 are determined as follows. First, find Q such that YOo-, ≦Yl, ≦YO0... old (4), and calculate the following. Expressions (4) and (5) above as P = nxm
Let's go about it. However, sco'-sco, scl
, ,'-SC, , .

As in the manual range 302, the minimum value is 302 M, ,,
If the chisel is protruding, please check the number! Either you can deal with it by only shifting as shown in A in Figure 0, or you can deal with it by changing the minimum value to 302M, o as shown in Figure 8.
This can be dealt with only by data compression. Alternatively, after shifting the entire data as shown in FIG. 1C, only the minimum data may be compressed. Furthermore, if only the maximum value 303M, . Alternatively, the maximum value side may be compressed after the entire shift as shown in FIG. In either case, the above (4)
and can be modified using equation (5).

Here, since there may be cases where there are no highlights or shadows in the human-powered image, this compression/expansion is performed only when the minimum human-powered image is below a certain value (e.g., equivalent to a density of 02), and when the human-powered image does not have highlights or shadows. Shadow processing may be performed when the maximum value is equal to or greater than a predetermined value (for example, equivalent to a density of 1.5).

Furthermore, in the case of color images, it is important to maintain gray balance. Therefore, in detecting highlights and shadows, a highlight point is determined for each pixel when all CMY values are less than a predetermined value, and a shadow point is determined when the values are greater than a predetermined value. Then, highlight processing is performed if there is a highlight point, and shadow processing is performed if there is a shadow point. In this case, compression and expansion may be performed for each color, or the same processing may be applied to the previous color. In the former case, it is necessary to obtain the gray balance of highlights and shadows in the reproduction area in advance.

In the latter case, it is best to find the minimum amount of compression/expansion for each color, and apply the same amount of compression/expansion to the other colors.

(Effects of the Invention) As described above, according to the method of the present invention, since the reproduction range of the copy output of the copying device includes the manual range of the original image to be copied, a higher quality image can be recorded. be able to.

In particular, it is possible to prevent blurring of highlight parts and parts of shadows.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a copying machine using a heat-developable photosensitive material to which the present invention can be applied, FIG. 2 is a perspective view showing the exposed portion thereof, and FIG. 3 is a configuration diagram of a circuit for realizing the method of the present invention. Fourth
The figure is a diagram used for this invention, FIG. 8 is a diagram for explaining an example of processing for data in a look-up table, and FIGS. 9 and 10 are diagrams for explaining this invention in detail. . IO... Copying machine using heat-developable photosensitive material, 100...
- Image reading unit, 101... Original, 102... Original table, 103... Glass unit, 130, 135... Lookup table, 133... D/8 converter, 134.
...Step signal generation circuit, 200...4 degrees. Applicant's agent Yasugata Yu Mijin / Hard CM Y Haya 4 2'' Article 5 Figure et IDD Peng. Brown 6 Figure No. 7 DD

Claims (1)

[Claims] In a method of scanning and reading a halftone image, converting it into an electrical signal, processing it, and scanning the recording material with a recording head to copy the image, the reproduction range of the copy output is different from the input range of the halftone image. If the input range of the halftone image is compressed or shifted so that the minimum value or maximum value of the input range, or the minimum value and maximum value are within the reproduction range, the signal conversion table is reconstructed. 1. A signal conversion method for halftone image copying, characterized in that the signal conversion table for copying is obtained by using the signal conversion table.