JP4089573B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method for forming an image using an image signal output from an image sensor.

  In recent years, a photographic processing apparatus employing a so-called digital exposure method has been widely used. In such a digital exposure method, an image can be formed by exposing a photographic paper with light modulated based on a digital image signal. Here, by adopting the digital exposure method, various image processing such as color correction, density correction, sharpening processing and the like can be performed with a high degree of freedom, and quick reprint processing can be performed. It is possible to obtain a high-quality print excellent in color and density reproducibility and resolution.

  Some digital exposure type photographic processing apparatuses as described above include a flatbed scanner capable of capturing an image formed on a document in order to obtain a digital image signal used for exposure processing. This scanner includes an imaging element such as a CCD (charge coupled device) image sensor for reading an image formed on a document in a housing having a contact glass for placing the document. Then, when the document placed on the contact glass is imaged by the image sensor, an image signal is output from the image sensor. The image signal subjected to various image processing is supplied as print data to an exposure head such as a PLZT (lead lanthanum zirconate titanate) optical shutter array, for example. An image is formed. The PLZT optical shutter array has a large number of optical shutters arranged in the main scanning direction, and each optical shutter functions as a light emitting unit capable of individually controlling the amount of light.

  However, since the sensitivity of a large number of photoelectric conversion units (pixels) included in the image sensor inevitably varies, the image signal output from the image sensor does not necessarily represent the characteristics of the original image that is the object to be imaged. It is not a thing. As a result, if the sensitivity variation of the photoelectric conversion unit is not taken into consideration, the image formed on the photographic paper has a poor quality reflecting the sensitivity variation of the photoelectric conversion unit. In order to cope with such a problem, in Patent Document 1, an image signal obtained by capturing a reference image having a uniform density is decomposed into a high frequency component and a low frequency component, and correction coefficients are respectively obtained for the high frequency component and the low frequency component. And the image signal obtained by the image sensor is corrected using these correction coefficients.

Japanese Patent Laying-Open No. 2002-51211 (FIG. 2)

  On the other hand, the amount of light emitted from each light emitting portion of the exposure head may vary along the main scanning direction due to uneven brightness of the light source or variation in optical shutter performance. In this case as well, the image formed on the photographic paper has a poor quality reflecting the variation in the amount of light. In order to correct this, a test chart (uniformity chart) is produced by the exposure head, the density of the part corresponding to each light emitting part of the exposure head in the produced test chart is detected, and between the detected light emitting parts There is a case where a light amount adjustment method of correcting an image signal based on the density difference so as to eliminate variations in the light amount emitted from each light emitting portion of the exposure head may be used. The test chart is a sheet on which an image including a region having a uniform density extending along the main scanning direction and a region where marks are formed at equal intervals along the main scanning direction is printed.

  However, even when the light amount adjustment using the test chart as described above is performed, if there is a variation in sensitivity in the photoelectric conversion unit in the image sensor used to detect the density of the test chart, it is formed on the photographic paper. The resulting image will be of poor quality. If the technique described in Patent Document 1 is used to solve such a situation, a filter for decomposing the image signal of the reference image into a high-frequency component and a low-frequency component is required, so that the device structure becomes complicated and complicated. This is a disadvantage in terms of cost.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of forming a high-quality image without complicating the apparatus structure even when the photoelectric conversion unit in the image sensor for obtaining an image signal has a sensitivity variation. Is to provide.

  Another object of the present invention is to provide an image forming method capable of forming a high-quality image by a relatively simple procedure even when the sensitivity of photoelectric conversion portions in an image sensor for obtaining an image signal varies. It is to be.

Means for Solving the Problems and Effects of the Invention

In the image forming apparatus of the present invention, a plurality of photoelectric conversion units are arranged, and when a medium supporting an image is imaged, an image sensor that outputs an image signal obtained by photoelectric conversion in the photoelectric conversion unit, and an individual A print head is used as a line exposure head in which a plurality of light emitting units capable of controlling the amount of light are arranged in the main scanning direction and a latent image is formed on the medium by exposing the medium with light rays from the plurality of light emitting units. An image forming unit that forms an image on a medium, a first test chart in which a predetermined image is formed using a part of the plurality of light emitting units of the print head, and the print head a test chart produced control means second test chart for controlling said image forming unit to be manufactured separately to the part of the predetermined image using the light-emitting portion is formed of, When the predetermined image formed on the first test chart and the predetermined image formed on the second test chart are captured by different areas of the image sensor, an image signal output from the image sensor And an offset amount calculating means for calculating an offset amount of a signal level between the different regions of the image sensor, and a medium supporting an image to be formed by the image forming unit is imaged by the image sensor. Correction means for adjusting the signal level of the image signal output from the image sensor by the offset amount corresponding to the relative position of the medium with respect to the image sensor at the time of imaging.

The image forming method of the present invention includes a plurality of light emitting units that are included in an image forming unit that forms an image on a medium and that can individually control the amount of light, and are arranged in the main scanning direction, and from the plurality of light emitting units. A first test in which a predetermined image is formed using a part of the light emitting portions of the plurality of light emitting portions of the print head, which is a line exposure head that forms a latent image on the medium by exposing the medium with light rays A step of separately preparing a chart and a second test chart on which the predetermined image is formed using the partial light emitting unit of the print head; and the predetermined image formed on the first test chart. And the predetermined image formed on the second test chart, a plurality of photoelectric conversion units are arranged, and when a medium supporting the image is captured, the photoelectric conversion in the photoelectric conversion unit is performed. Disposing the first and second test charts on the image sensor so as to face different areas of the image sensor that output the image signal obtained in the imaging, and the first and second A step of imaging a test chart by the imaging device, a step of calculating an offset amount of a signal level between the different regions of the imaging device based on an image signal output from the imaging device, and the image forming unit When a medium supporting an image to be formed is imaged by the image sensor, the signal level of the image signal output from the image sensor is set to the offset amount according to the relative position of the medium with respect to the image sensor at the time of imaging. And adjusting step.

  According to this configuration, since the signal level of the image signal is appropriately corrected by the offset amount calculated between different regions of the image sensor, the device structure is complicated even if there is a variation in the sensitivity of the photoelectric conversion unit in the image sensor. In addition, it is possible to form a high-quality image with a simple procedure.

  In the present invention, an average value of signal levels in a range corresponding to the predetermined image formed in the first test chart among the image signals output from the image sensor, and formed in the second test chart. The difference from the average value of the signal level in the range corresponding to the predetermined image may be obtained as the offset amount. According to this, a highly accurate offset amount can be obtained by a simple calculation.

  In the present invention, when the test chart is prepared, a plurality of blocks having different shading levels are formed in the predetermined image, and the offset is set for each of the plurality of blocks having different shading levels formed in the predetermined image. The amount may be calculated. According to this, the image signal can be corrected using an appropriate offset amount corresponding to the light and shade level, so that a higher quality image can be formed.

  A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a photographic processing apparatus which is an image forming apparatus according to the present embodiment. A photographic processing apparatus 1 shown in FIG. 1 has an image processing unit 10 that performs various processes on a captured image signal, and an image on a photographic paper 6 that is a silver halide photosensitive medium based on the image signal from the image processing unit 10. And a print processing unit 30 for printing. The photographic processing apparatus 1 in the present embodiment is known as a so-called digital minilab machine.

  The image processing unit 10 includes a film scanner 11 placed on a table 14 and a flat bed scanner 20 placed on a side table 18. The film scanner 11 is used to capture an image recorded on each frame of the film 5 as a digital signal. The flatbed scanner 20 incorporates a CCD image sensor 20a (see FIG. 3) as an image sensor. A large number of photoelectric conversion units are arranged in the CCD image sensor 20 a along the width direction of the flat bed scanner 20. The CCD image sensor 20a can output a digital signal color-separated into three primary colors of R (red), G (green), and B (blue) by taking an image.

  As shown in FIGS. 2A and 2B, a transparent plate-like contact glass 22 is disposed on the upper surface of the main body 21 of the flat bed scanner 20. A cover 24 is disposed on the contact glass 22. The cover 24 is attached to the main body 21 via a hinge 23 at one end on the upper surface of the main body 21. The cover 24 is pivotable about the hinge 23, and can be freely set in a closed posture covering the contact glass 22 and an open posture opened by the user's manual operation. The CCD image sensor 20 a is supported by the movable part 25 in the main body 21. When the image signal is captured by the flatbed scanner 20, the document 26 is placed on the contact glass 22, and then the cover 24 is closed to place the document 26 between the cover 24 and the contact glass 22. The CCD image sensor 20a scans the image formed on the sheet-like document 26 placed on the contact glass 22 as the movable portion 25 moves horizontally in the direction orthogonal to the longitudinal direction. .

  Image signals and other information captured by the film scanner 11 and the flatbed scanner 20 are displayed on the monitor 12. The monitor 12 is disposed on a table 14 together with a console 13 used by an operator to input various types of information. A control device 15 that controls the operation of the image processing unit 10 is disposed below the table 14.

  FIG. 3 is a block diagram illustrating only the main part of the photo processing apparatus shown in FIG. As illustrated in FIG. 3, the control device 15 includes a CPU 81 that performs various calculations, a RAM 82 that stores image signals and the like output from the CCD image sensor 20 a, and performs various image processes on the image signals stored in the RAM 82. The image processing chip 83 includes a hard disk 84 in which various data and software related to image processing are stored, and a data capturing unit 85 for capturing data from a removable storage medium. As will be described later, the CPU 81 functions as an offset amount calculation unit 81a and a correction unit 81b. A removable storage medium such as a memory card, MO, floppy (registered trademark) disk or the like can be mounted on the data fetching unit 85. The image signal captured from the data capturing unit 85 or the flatbed scanner 20 is processed by the image processing chip 83 and then supplied to the printing unit 30.

  Two photographic paper magazines 32 are placed on the upper surface of the casing 31 of the print unit 30. In the housing 31, a conveyance system 48 (see FIG. 3) that cuts and conveys the photographic paper 6 drawn from the photographic paper magazine 32 to a print size, and the photographic paper 6 cut to the print size as an image signal. An exposure unit 33 that performs exposure, a development processing unit 34 that includes a plurality of development processing tanks that perform development processing of the photographic paper 6 exposed by the exposure unit 33, and a control device 39 that controls the operation of the printing unit 30. Has been placed. The transport system 48 includes a transport roller pair, a paper guide, a cutter that cuts the photographic paper 6, a motor that drives the transport roller pair, and the like. The photographic paper 6 developed by the development processing unit 34 is dried by the drying unit 35 and then discharged outside the drying unit 35. On the downstream side of the drying unit 35, there are provided a conveyor 36 for horizontally feeding the photographic paper 6 and a sorter 37 for dividing and supporting a large number of the photographic paper 6 into a plurality of trays 38.

  As shown in FIG. 3, the control device 39 includes a CPU 91 that performs various calculations, a RAM 92 that stores image signals and the like transmitted from the image processing unit 10, software for various data and test chart production and exposure processing, and the like. Are stored in the hard disk 93. As will be described later, the CPU 91 functions as a test chart production control unit 91a.

  As shown in FIG. 4, the exposure unit 33 surrounds a halogen lamp 40, a dimming filter 41 that adjusts light emitted from the halogen lamp 40 to a desired color balance, and red, green, and blue color filters. A rotary filter 42 that is arranged in a direction and is driven to rotate by a motor (not shown), an integrator 43, an optical fiber bundle 44 that transmits light collected by the integrator 43, and a line exposure connected to the tip of the optical fiber bundle 44. And a head 45. The line exposure head 45 is disposed adjacent to the conveyance path of the photographic paper 6 conveyed by the conveyance system 48. The longitudinal direction of the line exposure head 45 is orthogonal to the conveyance direction of the photographic paper 6. An image signal is supplied from the control device 39 to the line exposure head 45. The line exposure head 45 is an optical shutter array in which several hundreds of PLZT optical shutters 46 (see FIG. 6) are arranged in a line. The photographic paper 6 is exposed only when the PLZT optical shutters 46 are open. The The exposure amount of the photographic paper 6 can be adjusted by controlling the opening time of each optical shutter 46 according to the print data.

  Next, an image forming procedure when printing an image taken from the flatbed scanner 20 will be described with reference to the flowchart shown in FIG.

  In order to print an image captured from the flatbed scanner 20 in the present embodiment, a test chart is prepared in advance using the line exposure head 45 (step S1), and the prepared test chart is placed on the flatbed scanner 20. (Step S2), and the captured test chart is imaged by the flatbed scanner 20 (step S3). Further, the offset between regions of the CCD image sensor 20a in the flatbed scanner 20 from the image signal obtained by the imaging. It is necessary to perform four preparation steps of calculating the amount (step S4). Hereinafter, these four preparation steps will be described in order. These four preparation steps do not need to be performed every time an image captured from the flatbed scanner 20 is printed, and may be performed only once every several days, for example.

  In step S1, the test chart production control unit 91a controls the line exposure head 45 and the transport system 48 to produce three test charts. Specifically, as shown in FIG. 6, three sheets of photographic paper 6 shorter than the line exposure head 45 are arranged so that all the PLZT optical shutters 46 of the line exposure head 45 face at least one photographic paper 6. Then, exposure is performed while sequentially transporting at different timings by shifting the transport paths by the transport system 48. At this time, the PLZT optical shutter 46 in two parts separated from each other (hereinafter referred to as “part R1” and “part R2”) faces the two photographic papers 6 but is outside the parts R1 and R2. The PLZT optical shutter 46 only faces one sheet of photographic paper 6. Therefore, the region near the right end of the photographic paper 6 conveyed at the left end and the region near the left end of the photographic paper 6 conveyed at the center are exposed by the light beam that has passed through the PLZT optical shutter 46 in the region R1, and conveyed at the right end. The region near the left end of the photographic paper 6 and the region near the right end of the photographic paper 6 conveyed in the center are exposed by the light beam that has passed through the PLZT light shutter 46 in the region R2. At this time, each PLZT optical shutter 46 of the line exposure head 45 is controlled to be opened and closed based on the same image signal regardless of which photographic paper 6 is conveyed. Therefore, in the area near the end of the two photographic papers 6 conveyed along the adjacent conveyance path, the same image is obtained by the light beam that has passed through the PLZT optical shutter 46 in the same region R1 or region R2 in the line exposure head 45. A latent image based on the signal is formed. In other words, even if there is a variation in the amount of light passing through the PLZT optical shutter 46 in the regions R1 and R2, the region near the end of the two photographic papers 6 conveyed along the adjacent conveyance path is substantially free. An image is formed with the same average density. Thereafter, three test charts 51, 52, and 53 in which the latent image is visualized are produced through a development process and the like.

  Here, the test charts 51 to 53 produced in step S1 will be described. FIG. 7 is a plan view of the test chart 51. As shown in FIG. 7, the test chart 51 has a rectangular shape, and the longitudinal direction thereof coincides with the longitudinal direction of the line exposure head 45. The test chart 51 has a cut line 55 (broken line with scissors marks) along the longitudinal direction. The cut line 55 becomes a mark when the operator cuts the test chart 51 into two along the longitudinal direction. When the test chart 51 is cut along the cut line 55, the test chart 51 is divided into a chart part 51a and a cut-off part 51b. The chart unit 51a is used in step S2, but the truncation unit 51b is discarded. Thus, since the cut line 55 is displayed on the test chart 51, it is difficult for an operator to make a mistake in the cutting operation using the scissors and the cutter knife, and the cutting operation can be performed in a short time.

  The chart unit 51a includes a position information display zone 60 in which three marks 61, 62, and 63 called register marks are printed at equal intervals, and an optical information display zone 70 including seven blocks 71 to 77 having different density levels. have. Here, both the position information display zone 60 and the optical information display zone 70 are band-like regions formed over the entire length along the longitudinal direction of the test chart 51 (the vertical direction in FIG. 7).

  The three marks 61 to 63 formed in the position information display zone 60 are identified by the difference in the number of short lines orthogonal to the long lines. The position information display zone 60 is used for identifying the position of the test chart 51 in the longitudinal direction, and for discriminating the inclination of the test chart 51, the orientation of the test chart 51 (incorrect pasting direction), and the like. It can also be used.

  The blocks 71 to 77 formed in the optical information display zone 70 have the same width. In the present embodiment, the block 71 has the lightest density (“white” in FIG. 7), and the block 77 has the darkest density (“black” in FIG. 7). The densities of the blocks 72 to 76 between the block 71 and the block 77 gradually change from a light density to a dark density in that order. The density of the blocks 71 to 77 corresponds to the amount of light passing through the PLZT optical shutter 46 of the exposure head 45.

  The test charts 52 and 53 have substantially the same configuration as that of the test chart 51, and each includes a chart part 52a and 53a (see FIG. 8) and a cut-off part (not shown). In the chart portions 52a and 53a, a position information display zone 60 and an optical information display zone 70 are formed as in the chart portion 51a. The configuration of the optical information display zone 70 in the three chart portions 51a to 53a is the same. On the other hand, the position information display zone 60 of the chart portion 51a is formed with three marks 61, 62, 63 each having one to three short lines, whereas the position information display zone 60 of the chart portion 52a is formed. Are formed with three marks 63, 64 and 65 each having 3 to 5 short lines, and the position information display zone 60 of the chart portion 53a has 3 marks each having 5 to 7 lines. 65, 66, and 67 are formed. The long lines of the marks 63, 64, 65 formed on the chart portion 52a and the marks 65, 66, 67 formed on the chart portion 53a are the same as the long lines of the marks 61, 62, 63 formed on the chart portion 51a, respectively. In position.

  Since the test charts 51 to 53 are produced as described above, the mark 63 formed on the chart portion 51a and the mark 63 formed on the chart portion 52a are provided with the same one or a plurality of PLZT optical shutters 46. It is formed by the light rays that have passed. Similarly, the mark 65 formed on the chart portion 52a and the mark 65 formed on the chart portion 53a are formed by light rays that have passed through the same one or more PLZT light shutters 46.

  Next, in step S <b> 2, the three chart parts 51 a to 53 a produced in step S <b> 1 are arranged on the flat bed scanner 20. At this time, as shown in FIG. 8, the adapter 28 having three openings 28a having the same width as the chart portions 51a to 53a is used, and the three chart portions 51a to 53a are fitted into the openings 28a in order from the left. At this time, all the position information display zones 60 of the chart portions 51a to 53a are directed in the same direction (in this embodiment, the left direction in FIG. 8). The end positions in the longitudinal direction of the three chart portions 51a to 53a may coincide with each other or may be different from each other. Thus, the adapter 28 in which the three chart portions 51 a to 53 a are fitted is placed on the contact glass 22. At this time, the adapter 28 is oriented so that the longitudinal direction of the chart portions 51a to 53a is orthogonal to the extending direction (main scanning direction) of the CCD image sensor 20a.

  Subsequently, when the flatbed scanner 20 is operated in step S3, the movable part 25 in the main body 21 scans the entire area of the three chart parts 51a to 53a while moving in parallel with the longitudinal direction of the chart parts 51a to 53a. To go. As a result, image signals relating to the three chart portions 51 a to 53 a are output from the CCD image sensor 20 a and stored in the RAM 82 in the control device 15. Thereafter, the image processing chip 83 may perform a correction process on the image signal stored in the RAM 82.

  As can be seen from the above description, the end area A (including the mark 63) of the chart portion 51a and the end area B (including the mark 63) of the chart portion 52a are both PLZT in the region R1 of the line exposure head 45. Both the end area C (including the mark 65) of the chart portion 52a and the end area D (including the mark 65) of the chart portion 53a are exposed by the light beam that has passed through the optical shutter 46. It is exposed by the light beam that has passed through the PLZT optical shutter 46 within the region R2. Therefore, even if there is a variation in the amount of light passing through the PLZT optical shutter 46 in the region R1, the average density of the blocks 71 to 77 in the end region A is equal to the blocks 71 to 77 in the end region B. The average concentration of each is the same. Similarly, the average density of the blocks 71 to 77 in the end area C is the same as the average density of the blocks 71 to 77 in the end area D. Further, since the longitudinal direction of the chart portions 51a to 53a and the extending direction (main scanning direction) of the CCD image sensor 20a are orthogonal to each other, the end region A, the end region B, and the end region C The end areas D are respectively imaged by different areas of the CCD image sensor 20a.

  Therefore, if there is no sensitivity variation in the photoelectric conversion unit of the CCD image sensor 20a, the average of the blocks 71 to 77 in the end area A calculated based on the image signal obtained by imaging with the flatbed scanner 20 is used. The density and the average density of the blocks 71 to 77 in the end area B are the same. Similarly, the average density of the blocks 71 to 77 in the end area C and the blocks 71 to 77 in the end area D are the same. The average concentration is the same. However, since there is actually a sensitivity variation in the photoelectric conversion unit of the CCD image sensor 20a, an offset (deviation) occurs in the average density.

  Therefore, in step S4, the offset amount calculation unit 81a obtains the average density offset amount. FIG. 9 is a flowchart showing a detailed procedure in the offset amount calculation step performed in step S4.

  Before describing each step in FIG. 9, the relationship between the arrangement direction of the photoelectric conversion units in the CCD image sensor 20 a and the shutter arrangement direction in the exposure head 45 will be described. FIGS. 10A and 10B are schematic plan views of the optical information display zone 70 in the end area A of the chart portion 51a and the end area B of the chart portion 52a, respectively. In FIGS. 10A and 10B, the seven blocks 71 to 77 constituting the optical information display zone 70 in the end area A and the end area B are illustrated as “blocks Z1 to Z7”. Yes. FIG. 11 is a diagram showing the relationship between the arrangement direction of the PLZT optical shutter 46 and the arrangement direction of the photoelectric conversion units of the CCD image sensor 20a in the block Z1 in the end area A. In FIG. 11, the block Z1 in the end area A is drawn with a solid line, the photoelectric conversion units arranged in the main scanning direction of the flatbed scanner 20 are shown as symbols Y1 to Y9, and the PLZT of the exposure head 45 is shown. The optical shutter 46 is indicated by symbols X1 to Xm. Further, along the conveyance of the photographic paper 6, the trajectories of the photoelectric conversion units Y1 to Y9 are drawn by broken lines, and the trajectories of the PLZT optical shutters X1 to Xm are drawn by dashed lines. In this embodiment, as can be seen from FIG. 11, the arrangement direction of the PLZT optical shutter 46 and the arrangement direction of the photoelectric conversion units are orthogonal to each other. Therefore, the images in the block Z1 in the end area A formed by exposure with the light beams that have passed through the m PLZT optical shutters X1 to Xm are read by the nine photoelectric conversion units Y1 to Y9. Note that, also in the blocks Z2 to Z7 in the end area A, the relationship between the shutter arrangement direction and the photoelectric conversion unit arrangement direction is the same as that in the block Z1 in the end area A.

  First, in step S101 of FIG. 9, the signal level of the image signal photoelectrically converted by the nine photoelectric conversion units Y1 to Y9 intersecting the elongated region which is the locus of the optical shutter X1 for the block Z1 in the end region A ( The average value of the light intensity value is obtained.

FIG. 12A shows the locus of the optical shutter X1 that has exposed the block Z1 in the end area A. FIG. On the trajectory shown in FIG. 12A, symbols of nine photoelectric conversion units Y1 to Y9 intersecting with the trajectory are given. In FIG. 12B, the signal level of the image signal corresponding to the photoelectric conversion units Y1 to Y9 that image the portion exposed to the light beam that has passed through the optical shutter X1 in the block Z1 in the end area A is A ( X1, Yk, Z1) (k is a natural number from 1 to 9). In addition, the average value of the signal levels of the image signals corresponding to the photoelectric conversion units Y1 to Y9 that image the portion exposed to the light beam that has passed through the optical shutter X1 in the block Z1 in the end area A is A (X1, Z1). ). The average value A (X1, Z1) is calculated based on the following formula.
A (X1, Z1,) = {A (X1, Y1, Z1) + A (X1, Y2, Z1)
+ A (X1, Y3, Z1) + A (X1, Y4, Z1)
+ A (X1, Y5, Z1) + A (X1, Y6, Z1)
+ A (X1, Y7, Z1) + A (X1, Y8, Z1)
+ A (X1, Y9, Z1)} / 9
= (S1 + S2 + S3 + ... + S9) / 9
= T1

  Subsequently, in step S102, by performing the same calculation as described above, photoelectric conversion is performed by imaging the portion exposed to the light beam that has passed through the optical shutters X2, X3,. Average values A (X2, Z1), A (X3, Z1), A (X4, Z1),..., A (Xm, Z1) of the image signal levels corresponding to the sections Y1 to Y9 are obtained. FIG. 12C corresponds to photoelectric conversion units Y1 to Y9 that image portions exposed by light rays that have passed through the optical shutter Xi (i is a natural number of 1 to m) in the block Z1 in the end area A. The average value A (Xi, Z1) of the signal level of the image signal is shown.

In step S103, an average value for the average value A (Xi, Z1) is obtained. In FIG. 12C, the average value for the average value A (Xi, Z1) is represented as the average value A (Z1). The average value A (Z1) is calculated based on the following formula.
A (Z1) = {A (X1, Z1) + A (X2, Z1) + A (X3, Z1)
+ A (X4, Z1) +... + A (Xm, Z1)} / m
= (T1 + T2 + T3 + ... + Tm) / m
= Tave

In step S104, the average value of the signal levels of the image signals corresponding to the photoelectric conversion units Y1 to Y9 that image the portion exposed to the light beam that has passed through the optical shutter X1 in the block Z1 in the end region B is obtained. FIG. 13A shows the trajectory of the optical shutter X1 that exposes the block Z1 in the end region B. FIG. On the trajectory shown in FIG. 13A, symbols of nine photoelectric conversion units Y1 to Y9 intersecting with the trajectory are given. In FIG. 13B, the signal levels of the image signals corresponding to the photoelectric conversion units Y1 to Y9 that image the portion exposed to the light beam that has passed through the optical shutter X1 in the block Z1 in the end region B are B ( X1, Yk, Z1) (k is a natural number from 1 to 9). In addition, the average value of the signal levels of the image signals corresponding to the photoelectric conversion units Y1 to Y9 that image the portion exposed by the light beam that has passed through the optical shutter X1 in the block Z1 in the end area B is B (X1, Z1). ). The average value B (X1, Z1) is calculated based on the following formula.
B (X1, Z1,) = {B (X1, Y1, Z1) + B (X1, Y2, Z1)
+ B (X1, Y3, Z1) + B (X1, Y4, Z1)
+ B (X1, Y5, Z1) + B (X1, Y6, Z1)
+ B (X1, Y7, Z1) + B (X1, Y8, Z1)
+ B (X1, Y9, Z1)} / 9
= (U1 + U2 + U3 + ... + U9) / 9
= V1

  Subsequently, in step S105, by performing the same calculation as described above, the photoelectric conversion obtained by imaging the portion exposed to the light beam that has passed through the optical shutters X2, X3,. Average values B (X2, Z1), B (X3, Z1), B (X4, Z1),..., B (Xm, Z1) of the image signal levels corresponding to the portions Y1 to Y9 are obtained. FIG. 13C corresponds to photoelectric conversion units Y1 to Y9 that image portions exposed by light rays that have passed through the optical shutter Xi (i is a natural number of 1 to m) in the block Z1 in the end region B. The average value B (Xi, Z1) of the signal level of the image signal is shown.

In step S106, an average value for the average value B (Xi, Z1) is obtained. In FIG. 13C, the average value for the average value B (Xi, Z1) is represented as the average value B (Z1). The average value B (Z1) is calculated based on the following formula.
B (Z1) = {B (X1, Z1) + B (X2, Z1) + B (X3, Z1)
+ B (X4, Z1) +... + B (Xm, Z1)} / m
= (V1 + V2 + V3 + ... + Vm) / m
= Vave

Next, in step S107, by calculating the difference between the average value A (Z1) and the average value B (Z1), an offset amount AB (Z1) of these average values is obtained. The offset amount AB (Z1) for the block Z1 is calculated based on the following equation.
AB (Z1) = Tave-Vave = P1

Here, when the offset amount AB (Z1) is added to the average value B (Xi, Z1) shown in FIG. 13C (see FIG. 13D), each optical shutter in the block Z1 in the end area B is obtained. A corrected average value B ′ (Xi, Z1) of the signal level of the image signal corresponding to the photoelectric conversion units Y1 to Y9 that image the portion exposed by the light beam that has passed through Xi is obtained. The average value B ′ (Z1) for the average value B ′ (Xi, Z1) is calculated based on the following equation.
B ′ (Z1) = {B ′ (X1, Z1) + B ′ (X2, Z1) + B ′ (X3, Z1)
+ B ′ (X4, Z1) +... + B ′ (Xm, Z1)} / m
= {(V1 + P1) + (V2 + P1) + ... + (Vm + P1)} / m
= Vave '
The average value B ′ (Z1) is equal to the average value A (Z1). That is, the relationship shown in the following formula is established.
B ′ (Z1) = Vave ′ = Tave = A (Z1)
Since such a relationship is established, it is possible to correct the signal level of an arbitrary image signal using the offset amount AB (Z1) as follows.

  Subsequently, in step S108, the offset amount AB (Zj) (j is a natural number of 2 or more and 7 or less) for each of the blocks Z2 to Z7 is calculated in the same manner as described above. FIG. 14 shows a list of offset amounts AB (Z1) to AB (Z7) for the blocks Z1 to Z7.

  Next, in step S109, the offset amount CD (Zj) between the end region C and the end region D is calculated in the same manner as the offset amount AB (Zj) is calculated. The procedure for calculating the offset amount CD (Zj) is the same as the procedure for calculating the offset amount AB (Zj) (steps S101 to S108), and thus the description thereof is omitted. FIG. 15A shows a list of offset amounts CD (Zj).

  In step S110, an offset amount AD (Zj) between the end area A and the end area D is calculated. The offset amount AD (Zj) may be obtained by performing the same procedure as that for calculating the offset amount AB (Zj), or by adding the offset amount AB (Zj) and the offset amount CD (Zj). It may be calculated. FIG. 15B shows a list of offset amounts AD (Zj).

  After completing the four preparation steps as described above, in step S5, the photographic processing apparatus 1 reads a document on which an image to be printed is read by the flatbed scanner 20. At this time, the image signal output from the CCD image sensor 20 a is stored in the RAM 82 in the control device 15. The image processing chip 83 may perform a correction process on the image signal stored in the RAM 82. As a modification, step S5 may be executed before performing the four preparation steps.

  Subsequently, in step S6, the correction unit 81b adjusts the signal level of the image signal stored in the RAM 82 by the offset amount obtained in step S3. At this time, which of the offset amount AB (Zj), the offset amount CD (Zj), and the offset amount AD (Zj) is used depends on the location where the document is placed in step S5. In the present embodiment, the same location as the chart portion 51a on the contact glass 22 is treated as a reference position. Therefore, if the document is placed at the same location as the chart portion 51a, the image signal is corrected by the offset amount. Is not done. If the document is placed at the same location as the chart portion 52a, the offset amount AB (Zj) is added to the image signal. If the document is placed at the same location as the chart portion 53a, the offset amount AD (Zj) (or both the offset amount AB (Zj) and the offset amount CD (Zj)) is added to the image signal. The image signals corrected in this way are sequentially supplied from the RAM 82 to the print processing unit 30 and stored in the RAM 92 of the control device 39. The reference position may be the same location as the chart portion 52a or the same location as the chart portion 53a.

  As the offset amount used in the correction in step S6, out of the seven offset amounts AB (Zj) (or the offset amount AD (Zj)), it corresponds to the signal level (gradation) of the image signal to be corrected. Things are used. That is, the image signal in the region with the highest signal level is corrected with the offset amount AB (Z7), the image signal in the region with the lowest signal level is corrected with the offset amount AB (Z1), and the image signal with the signal level in between is corrected. Correction is appropriately made with the offset amounts AB (Z2) to AB (Z6). By doing so, correction with higher accuracy is realized.

  In step S7, the image signal corrected in step S5 and stored in the RAM 92 of the print processing unit 30 is sequentially supplied to the exposure head 45 while the transport system 48 is driven, so that the image signal is corrected. The photographic printing paper 6 is exposed with the amount of light. In this manner, a latent image in which the sensitivity variation of the photoelectric conversion unit of the CCD image sensor 20a for capturing an image signal is eliminated can be formed on the photographic paper 6. Thereafter, through a development process or the like, a photographic print in which the latent image formed on the photographic paper 6 is visualized can be obtained.

  As described above, according to the present embodiment, the signal level of the image signal is appropriately adjusted according to the offset amount calculated between different regions of the CCD image sensor 20a, and thus the sensitivity of the photoelectric conversion unit in the CCD image sensor 20a. Even if there is a variation, it is possible to form a high-quality image with a simple procedure without complicating the apparatus structure.

  Further, in the present embodiment, the average signal level difference in each of the blocks Z1 to Z7 between the two end regions is obtained as the offset amount, so that a highly accurate offset amount can be obtained by a simple calculation. Moreover, by obtaining the offset amount for each of the blocks Z1 to Z7 having different gray levels, the image signal can be corrected using an appropriate offset amount according to the gray level of the image signal, so that a higher quality image can be obtained. It becomes possible to form.

  The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various design changes can be made as long as they are described in the claims. . For example, in the above-described embodiment, the seven linear blocks 71 to 77 having the same width and different densities from each other in the optical information display zones 70 of the chart portions 51a to 53a of the test charts 51 to 53 are provided. Although the case where it is included is described, the configuration of the optical information display zone can be arbitrarily changed as long as the light amount of the exposure head can be appropriately corrected. Therefore, the optical information display zone does not necessarily include seven blocks, and the number of blocks can be arbitrarily changed. Therefore, the optical information display zone may have only one block representing any gray level (for example, an intermediate gray color corresponding to the average value of each density of the blocks 71 to 77).

  In addition to the seven blocks 71 to 77 for each output tone of the exposure head, the optical information display zone 70 is another block for determining the amount of incorrect color on the photographic paper when the photographic paper is exposed by the exposure head. May be included. Specifically, the test chart has, for example, yellow (yellow), magenta (red purple), and cyan (blue-green) blocks adjacent to the seven blocks 71 to 77. The incorrect color amount may be obtained based on the light amount data obtained by reading the corresponding area with the scanner.

In the present invention, the number of test charts to be produced may be two, or four or more. Furthermore, the offset amount may be calculated based on calculating some representative value of the block other than the average value.

1 is a perspective view of a photographic processing apparatus that is an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view of a flatbed scanner included in the photo processing apparatus shown in FIG. 1 in a state where a cover is opened and a state where the cover is closed. FIG. 2 is a block diagram illustrating only a main part of the photo processing apparatus shown in FIG. 1. It is a perspective view of the exposure part contained in the photographic processing apparatus shown in FIG. It is a flowchart which shows the procedure of the image formation in the case of printing the image taken in from the flat bed scanner. It is the model which drawn the positional relationship of the exposure head at the time of test chart preparation, and three printing papers. It is a top view of a test chart. FIG. 8 is a plan view illustrating a state in which a chart portion, which is a part of the test chart illustrated in FIG. 7, is fitted into an opening provided in an adapter that is used when being placed on a flat bed scanner. It is the flowchart which showed the detailed procedure in the offset amount calculation step performed by step S4 of FIG. It is a typical top view of the optical information display zone formed in the edge part area of a different chart part. It is a figure which shows the relationship between the arrangement direction of the PLZT optical shutter in the block Z1 of the edge part area A, and the arrangement direction of the photoelectric conversion part of a CCD image sensor. FIG. 6 is a diagram for explaining a procedure for calculating an average value of signal levels of image signals in a block Z1 in an end area A. FIG. 6 is a diagram for describing a procedure for calculating an average value of signal levels of image signals in a block Z1 in an end area B. It is the figure which displayed the offset amount AB (Z1)-AB (Z7) about block Z1-Z7 as a list. It is the figure which displayed as a list the offset amount CD (Z1)-CD (Z7), AD (Z1)-AD (Z7) about blocks Z1-Z7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Flatbed scanner 20a CCD image sensor 28 Adapter 33 Exposure part 45 Line exposure head 46 PLZT optical shutter 48 Transport system 51, 52, 53 Test chart 51a Chart part 51b Cut-off part 60 Position information display zone 61, 62, 63 Mark 70 Optical Information display zone 71 to 77 block 81a offset amount calculation unit 81b correction unit 91a test chart production control unit

Claims (6)

A plurality of photoelectric conversion units are arranged, and when a medium supporting an image is imaged, an image sensor that outputs an image signal obtained by photoelectric conversion in the photoelectric conversion unit,
A print head which is a line exposure head in which a plurality of light emitting units capable of individually controlling the amount of light are arranged in the main scanning direction and a latent image is formed on the medium by exposing the medium with light rays from the plurality of light emitting units. An image forming unit that forms an image on a medium using,
A first test chart in which a predetermined image is formed using a part of the plurality of light emitting units of the print head, and the predetermined image using the part of the light emitting unit of the print head. Test chart production control means for controlling the image forming unit so that the second test chart on which is formed is separately produced;
When the predetermined image formed on the first test chart and the predetermined image formed on the second test chart are captured by different regions of the image sensor, an image signal output from the image sensor An offset amount calculating means for calculating an offset amount of a signal level between the different regions of the image sensor,
When a medium supporting an image to be formed by the image forming unit is imaged by the image sensor, the signal level of the image signal output from the image sensor is set to a relative position of the medium with respect to the image sensor at the time of imaging. An image forming apparatus comprising: a correction unit that adjusts according to the corresponding offset amount.   The offset amount calculating means includes an average value of signal levels in a range corresponding to the predetermined image formed on the first test chart, among the image signals output from the image sensor, and the second test. The image forming apparatus according to claim 1, wherein a difference from an average value of signal levels in a range corresponding to the predetermined image formed on the chart is obtained as the offset amount. The test chart production control means controls the image forming unit so that a plurality of blocks having different gray levels are formed in the predetermined image,
The image forming apparatus according to claim 1, wherein the offset amount calculating unit calculates the offset amount for each of the plurality of blocks formed in the predetermined image and having different gray levels. A plurality of light emitting units included in an image forming unit that forms an image on the medium and individually controllable in light quantity are arranged in the main scanning direction, and the medium is exposed by light rays from the plurality of light emitting units. A first test chart in which a predetermined image is formed using a part of the light emitting units of the plurality of light emitting units of the print head that is a line exposure head that forms a latent image on a medium; and Separately producing a second test chart on which the predetermined image is formed using the partial light emitting unit ;
A plurality of photoelectric conversion units are arranged in the predetermined image formed on the first test chart and the predetermined image formed on the second test chart, and a medium supporting the image is captured. And disposing the first and second test charts on the image sensor so as to face different areas of the image sensor that output an image signal obtained by photoelectric conversion in the photoelectric conversion unit during imaging. ,
Imaging the first and second test charts with the imaging device;
Calculating an offset amount of a signal level between different regions of the image sensor based on an image signal output from the image sensor;
When a medium supporting an image to be formed by the image forming unit is imaged by the image sensor, the signal level of the image signal output from the image sensor is set to a relative position of the medium with respect to the image sensor at the time of imaging. And an image forming method characterized by comprising: a step of adjusting according to the corresponding offset amount. In the step of calculating the offset amount, an average value of signal levels in a range corresponding to the predetermined image formed on the first test chart among the image signals output from the image sensor, and the second 5. The image forming method according to claim 4 , wherein a difference from an average value of signal levels in a range corresponding to the predetermined image formed on the test chart is obtained as the offset amount. In the step of preparing the test chart, a plurality of blocks having different shading levels are formed in the predetermined image,
6. The image forming method according to claim 4 , wherein in the step of calculating the offset amount, the offset amount is calculated for each of the plurality of blocks formed in the predetermined image and having different gray levels.

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