JP2008199255A - Image reader, and image correction method and image correction program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compensate reduction in resolution caused by a variation in an optical system of an image reader. <P>SOLUTION: The image reader includes: a film holder having a photographic film holding part and a reference hole piercing the film holder in a direction orthogonal to a photographic film held in the holding part; a reading carriage on which a fluorescent tube irradiating the photographic film held in the film holder from one side of the film with illuminating light and a CCD receiving light from the fluorescent tube by which the photographic film is irradiated and which has transmitted through the photographic film and obtaining image information by converting the light to electric signals per line and per wavelength band are mounted and which scans the photographic film in a direction orthogonal to lines to read an image on the photographic film; and a correction part detecting the positional deviation of images formed by wavelength bands different from each other in the received light to perform such correction as to reduce the positional deviation in image information. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, a correction method, and a correction program. More specifically, the present invention relates to an image reading apparatus that receives light emitted from a light source and transmitted through a transparent original to generate image information, and a correction method and a correction program that can be executed in the image information reading apparatus.

  There is an image reading apparatus that reads an image from a transparent original and converts the image information into electronic information. This type of image reading apparatus includes a light source that emits light from one surface of a transparent original and a sensor that receives the transmitted light and converts it into an electrical signal on the other surface of the transparent original.

  Many of the image reading apparatuses include a line sensor that converts an image of a linear region into an electrical signal, and reads a two-dimensional image by scanning the surface of a transparent original with the line sensor. On the other hand, as a light source, there are a case where a surface light emitting element having an area equivalent to that of a transparent original is used and a case where a linear light source that scans a transparent original in synchronization with a line sensor is used. In this way, an image can be accurately read under uniform brightness.

  One example of a transparent original is a developed negative film and a reversal film (hereinafter collectively referred to as “photographic film”) in a silver halide photographic system. Since the resolution of silver halide photographs exceeds 5000 dpi even in the case of a film of about ISO 100, an image reading apparatus that reads the film is required to have a very high optical resolution. On the other hand, with the advancement of semiconductor technology, the resolution of line sensors has also increased considerably. However, the resolution of the image reading apparatus depends on factors other than the resolution of the line sensor.

  The following Patent Document 1 and Patent Document 2 describe the structure of a film holder that can automatically determine the type of transparent document to be held. That is, when reading an image from a photographic film, a transparent original is held flat by using a film holder for accurate reading. However, the type of film holder used differs depending on the type of transparent original. Therefore, each film holder is provided with a physical shape indicating the type of photographic film held by the film holder, whereby the image reading apparatus performs reading under appropriate conditions.

  Patent Document 3 below describes a film scanner that can individually adjust the focus of an optical system of an image reading apparatus in accordance with the color of an image read from a transparent original. Thereby, it is possible to prevent the resolution from being lowered due to the difference in the focus distance between the colors.

Further, in Patent Document 4 below, in an image reading apparatus having a function of detecting dust adhering to a transparent original using an infrared light band included in illumination light that illuminates the transparent original, the infrared light band and An image processing method for correcting a positional shift due to a difference in optical characteristics between visible light bands is described. Thereby, noise generated in the image information due to dust can be removed without damaging the image of the transparent original.
JP 09-266524 A JP 2006-184885 A JP 2000-196817 A JP 2004-318425 A

  However, since the image reading apparatuses described in Patent Document 1 and Patent Document 2 select a preset reading condition according to the type of document, resolution caused by mechanical and optical variations of each part of the reading apparatus. Cannot compensate for the decline. Further, the apparatus described in Patent Document 3 exclusively corrects the change in the focusing distance according to the color difference. Furthermore, since the method described in Patent Document 4 performs image processing with a large load, the environment in which the method can be executed is limited.

  In order to solve the above problems, as a first embodiment of the present invention, a light source that irradiates illumination light having a predetermined wavelength bandwidth from one surface of a transmission original, and light that is emitted from the light source and passes through the transmission original is used. A line sensor that receives light and outputs an electrical signal corresponding to an image included in the linear area on the transparent original, and moves the transparent original by moving in the sub-scanning direction intersecting the longitudinal direction of the linear area. A scanning carriage that scans an image of the entire transparent original as image information by scanning, an opening that contains the image formed on the transparent original, a holding part that holds the edge of the transparent original around the opening, and a holding A holder having a plurality of reference holes formed so as to penetrate in a direction perpendicular to the transparent original held by the scanning unit and arranged along the scanning direction of the reading carriage, and reference light that passes through the reference hole among illumination light. Receive light By detecting at least one of the known shape and arrangement of the reference hole in the read image formed by the line sensor, and making the detected at least one coincide with at least one of the known shape and arrangement of the reference hole An image reading apparatus is provided that includes a correction unit that executes image correction processing for each of different wavelength bands included in the reference light to generate image information. As a result, in an image reading apparatus that performs reading of a transparent original that requires a particularly high resolution, it is possible to easily reduce the resolution caused by the optical variation from the light source for illumination to the line sensor and the optical variation occurring in the line sensor. It can be compensated effectively by the structure and method. Even when the optical characteristics are distributed in the scanning direction of the reading carriage, it is possible to effectively correct each area of the read image.

  Furthermore, in the image reading apparatus, the plurality of reference holes may be arranged along a pair of sides parallel to the scanning direction of the reading carriage among the sides of the opening. Thereby, it is possible to detect the distribution of optical characteristics for the entire image of the transparent original and effectively correct each area of the read image.

  In the image reading apparatus, a plurality of reference holes may be further provided along the longitudinal direction of the linear region read by the line sensor. Thereby, even when there is a variation in the optical characteristics inside each of the linear regions, effective correction can be executed.

  In the image reading apparatus, a plurality of reference holes may be arranged along three sides including a side parallel to the scanning direction of the reading carriage among the sides of the opening. Thereby, the two-dimensional distribution of optical characteristics can be effectively corrected.

  In the image reading apparatus, the wavelength band includes three bands of red, blue, and green among visible light bands included in the illumination light, and the line sensor includes a light receiving element that receives each of the three bands. And one position of the transparent original may be received at different timings in the movement in the sub-scanning direction. Thereby, when synthesizing images received at different timings for each band, it is possible to effectively compensate for a decrease in resolution of image information caused by a shift in the moving speed of the line sensor in the sub-scanning direction.

  In the image reading apparatus, the wavelength band may include a specific band in the visible light band included in the illumination light and a specific band included in the infrared band included in the illumination light. Thereby, the deviation based on the difference in optical characteristics between the visible light band and the infrared band is eliminated, and reading in the infrared region can be used with high accuracy.

  Further, in the image reading apparatus, the correction unit may perform the reference light based on a light receiving interval of reference light that has passed through a pair of adjacent reference holes among a plurality of reference holes and a known interval between the pair of reference holes. The change in the optical path length may be detected, and the image information may be corrected so as to cancel the change in the image information due to the change. Thereby, it is possible to effectively compensate for the deformation of the image information by detecting the optical path length change caused by the mechanical accuracy in the image reading apparatus.

  In the image reading apparatus, the innermost circumference of each of the plurality of reference holes may have a reduced thickness in the propagation direction of the reference light. Thereby, the deformation | transformation of the reference image by the irradiation angle with respect to the reference hole of reference light can be reduced, and the detection accuracy of the shift | offset | difference using reference light can be improved.

  In the image reading apparatus, the correction unit corrects the image information read from each area of the transparent document based on a positional deviation detected from a reference hole closest to each of the areas among the plurality of reference holes. May be. Thereby, the chromatic aberration generated in each area of the read image can be accurately corrected according to the generation amount in each area.

  Further, in the image reading apparatus, the correction unit calculates the correction amount calculated based on the positional deviation detected from the pair of reference holes that sandwich the area among the plurality of reference holes. You may correct | amend based on. As a result, the two-dimensional chromatic aberration distribution on the read image can be accurately corrected according to the amount of occurrence in each region.

  Further, as a second embodiment of the present invention, a light source that irradiates illumination light having a predetermined wavelength bandwidth from one surface of a transmission original, and light that is emitted from the light source and transmitted through the transmission original is received and the transmission original is received. Equipped with a line sensor that outputs an electrical signal corresponding to the image contained in the upper linear area, and moves in the sub-scanning direction intersecting the longitudinal direction of the linear area to scan the transparent original and transmit A reading carriage that reads an image of the entire document as image information, an opening that contains an image formed on the transparent document, a holding unit that holds an edge of the transparent document around the opening, and a holding unit A correction method for correcting image information in an image reading apparatus including a holder having a plurality of reference holes formed in a direction orthogonal to a transparent original and arranged along a scanning direction of a reading carriage A procedure for forming a read image by the line sensor by receiving reference light that has passed through the reference hole in the illumination light, a procedure for detecting at least one of the known shape and arrangement of the reference hole from the read image, A correction method is provided that includes a process of correcting the detected at least one to match at least one of a known shape and arrangement of a reference hole for each different wavelength band included in the reference light. Is done. Thereby, the above effects can be enjoyed without being limited by hardware.

  Further, as a third embodiment of the present invention, a light source that irradiates illumination light having a predetermined wavelength bandwidth from one surface of the transmission original, and light that is emitted from the light source and transmitted through the transmission original is received and the transmission original is received. Equipped with a line sensor that outputs an electrical signal corresponding to the image contained in the upper linear area, and moves in the sub-scanning direction intersecting the longitudinal direction of the linear area to scan the transparent original and transmit A reading carriage that reads an image of the entire document as image information, an opening that contains an image formed on the transparent document, a holding unit that holds an edge of the transparent document around the opening, and a holding unit An image reading process for correcting image information in an image reading apparatus comprising a holder having a plurality of reference holes formed so as to penetrate in a direction orthogonal to the transparent original and arranged along the scanning direction of the reading carriage. A correction program executed by the apparatus, comprising: a step of forming a read image by a line sensor by receiving reference light that has passed through a reference hole in illumination light; and a known shape and arrangement of the reference hole from the read image. A step of detecting at least one and a process of correcting the detected at least one to match at least one of the known shape and arrangement of the reference hole for each different wavelength band included in the reference light An image correction program is provided. Accordingly, the above-described effects can be enjoyed even in an existing image reading apparatus by supplying as software.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all combinations of features described in the embodiments are essential for the solution of the invention.

  FIG. 1 is a perspective view illustrating an appearance of an image reading apparatus 100 according to an embodiment. As shown in FIG. 1, the image reading apparatus 100 includes a lower case 110 and an upper case 120 that form a substantially cubic housing, and a document presser 130 having one end coupled to the upper case 120.

  The lower case 110 supports the entire image reading apparatus 100 and also supports an internal mechanism 200 described later. Further, the upper case 120 protects the internal mechanism 200 and includes a document table 122 formed on its upper surface by a transparent glass plate, a plastic plate or the like.

  Further, the document presser 130 can be opened and closed on the upper case 120 using one side coupled to the upper case 120 as a hinge. As a result, the original 140 can be placed on the original table 122 and the original 140 can be pressed from above and brought into close contact with the original table 122. A pressure plate 132 that holds the original 140 is attached to the lower surface of the original holder 130.

  Furthermore, the image reading apparatus 100 can remove the pressure plate 132. When the pressure plate 132 is removed, a light source 136 that illuminates a transparent original (not shown) such as a photographic film 480 placed on the original table 122 from above appears. The light source 136 reciprocates in synchronization with a reading carriage 300 (to be described later) within an elongated illumination window 134 formed in the longitudinal direction on the lower surface of the document holder 130.

  FIG. 2 is a plan view showing the internal mechanism 200 of the image reading apparatus 100, and shows a state where the document presser 130 and the upper case 120 are removed from the image reading apparatus 100 shown in FIG. As shown in the figure, the image reading apparatus 100 includes a reading carriage 300 formed by a substantially rectangular reading carriage case 310 extending in the short side direction of a document 140. The reading carriage case 310 has, on its upper surface, a groove 314 that accommodates the fluorescent tube 350 that illuminates the original, and a reading unit 312 that reads an image of the original illuminated by the fluorescent tube 350.

A guide rail 210 is arranged in parallel with the long side of the lower case 110. The guide rail 210 is inserted into the reading carriage 300 and both ends thereof are fixed to the lower case 110 by a pair of brackets 212. Thus, reading carriage 300 is guided by the guide rails 210, as shown by the arrow M ₁ in FIG, it moves parallel to the long side of the lower case 110. In the following description, the moving direction of the reading carriage 300 is referred to as “sub-scanning direction”. In addition, the longitudinal direction of the reading unit 312 in the reading carriage 300 is referred to as a “main scanning direction”.

  Further, a timing belt 222 that is stretched between a pair of pulleys 224 is disposed in the vicinity of the guide rail 210. The timing belt 222 travels in parallel with the guide rail 210 between the pulleys 224. The timing belt 222 is coupled to the reading carriage 300. On the other hand, one of the pulleys 224 is rotationally driven by a stepping motor 226 via a gear 228. Therefore, the reading carriage 300 can be moved along the guide rail 210 by controlling the rotation amount of the stepping motor 226.

  The reading carriage 300 is coupled to a circuit board 230 disposed on the bottom surface of the lower case 110 via a flat cable 240 and a connector 234. Since the flat cable 240 is flexible, it does not hinder the movement of the reading carriage 300.

  The circuit board 230 is also connected to the outside of the image reading apparatus 100 via the connector 232. Thereby, the image information read by the reading carriage 300 can be transmitted to an external information processing apparatus 510 (see FIG. 3) or the like.

  The circuit board 230 includes a correction unit that corrects the read image. The correction unit can also execute image processing in cooperation with the information processing apparatus 510 or the like connected via the connector 232. Further, the circuit board 230 includes a control unit that controls operations of the stepping motor 226, the reading carriage 300, and the like. Note that power for driving the circuit board 230, the stepping motor 226, the fluorescent tube 350, and the like is supplied from the power supply unit 250.

  FIG. 3 is a diagram showing a structure of a system 500 formed when image reading is executed from the reflective original 142 using the image reading apparatus 100. As shown in the figure, in this system 500, the image reading apparatus 100 is connected to an information processing apparatus 510 as a host apparatus via a connection cable 518 connected to the connector 232 thereof. The information processing apparatus 510 includes both a keyboard 512 and a mouse 514 that are input devices from the user, and a display device 520 that displays an image to the user.

  The information processing apparatus 510 also includes a disk drive 516 that reads and writes information from and on a recording medium such as a magnetic disk and an optical disk, and a communication line (not shown) that can exchange information by communicating with the outside. Accordingly, by installing a program via a recording medium, a communication line, or the like loaded in the disk drive 516, the image reading apparatus 100 can execute correction processing described later.

  By forming the system 500 as described above, the user can convert the image into information and display it on the display device 520. Furthermore, the obtained image information can be stored and arbitrary processing can be executed. Further, an error, a next operation guidance, and the like that have occurred on the image reading apparatus 100 side can be displayed as messages on the display device 520.

  FIG. 4 is a diagram showing the internal structure of the reading carriage 300 of the image reading apparatus 100 as a cross section viewed from the viewpoint indicated by the arrow X in FIG. In addition, an optical system formed in the image reading apparatus 100 when the reflective original 142 is read is also shown. For the purpose of clarifying the explanation, a reflection original 142 pressed on the original table 122 by the original presser 130 is also drawn.

  As shown in the figure, on the upper surface of the reading carriage case 310, a reading unit 312 sealed with a transparent plate is formed in the approximate center in the sub-scanning direction. Further, a groove 314 that accommodates a fluorescent tube 352 as an illumination light source is formed adjacent to the reading unit 312.

  On the other hand, inside the reading carriage case 310, a reflecting mirror 322 is arranged below the reading unit 312 and further a lens unit 330 is arranged below the reflecting mirror 322. The lens unit 330 includes a lens 332 supported by the lens holder 334. A plurality of reflecting mirrors 324, 326, and 328 and a CCD 340 are disposed at each corner inside the reading carriage case 310. The CCD 340 is an example of a line sensor, and a plurality of light receiving elements are arranged in a direction perpendicular to the paper surface of FIG.

  In the reading carriage 300 as described above, the reflected light of the reflective original 142 illuminated by the fluorescent tube 352 enters the reflecting mirror 322 via the reading unit 312. As a result, of the image formed on the flat reflective original 142, an image of a linear region facing the reading unit 312 enters the reflecting mirror 322.

  The light reflected by the reflecting mirror 322 is sequentially reflected by the reflecting mirrors 324, 326, and 328, and enters the CCD 340 through the lens unit 330. As a result, a sufficiently long optical path length can be obtained, so that the reflected light having a linear beam cross section is reduced, and the reflected light corresponding to the entire width of the original is incident on the CCD 340 having a narrow width with respect to the width of the reflective original 142. The When the reflected light enters the CCD 340 in this way, the CCD 340 generates an electrical signal having a strength corresponding to the intensity of the reflected light. Thus, an electrical signal corresponding to the image on the reflective original 142 is obtained. Further, as already described, the reading carriage 300 moves in the sub-scanning direction along the guide rail 210, so that the entire image of the lower surface of the reflective original 142 is read.

  FIG. 5 is a plan view showing the shape of a film holder 400 used when the image reading apparatus 100 shown in FIGS. 1 and 2 reads an image from a photographic film 480 as a transparent original. As shown in the figure, the film holder 400 includes a main body 410 that is a substantially rectangular plate as a whole, and a positioning tab 450, a film holder detection region 460, and a light source light reference region 430 that are disposed along the outer periphery of the main body 410. Is provided.

  When the film holder 400 is placed on the document table 122 of the image reading apparatus 100, the positioning tab 450 serves as a guide for positioning the film holder 400 itself by matching with the alignment marks provided around the document table 122. In the film holder detection area 460, the surface facing the CCD 340 in a state of being placed on the document table 122 is painted white. When the reading carriage 300 reads the film holder detection area 460, it is detected that the film holder 400 is placed on the document table 122. Thereby, it is possible to automatically switch to the operation of reading the transparent original. In the light source light reference region 430, a notch region is formed in the film holder 400, and the illumination light of the light source 136 provided on the side of the document holder 130 is transmitted as it is. As a result, the CCD 340 can be used to detect the intensity of light source light, the spectral distribution, and the like.

  In addition, a rectangular transmission window 412 and a film presser 420 surrounding the periphery of the transmission window 412 are disposed inside the main body 410. The film presser 420 can be opened by operating the tab 424 with one side as a hinge, and grips the edge of the photographic film 480 of the Broni plate in cooperation with the main body 410.

  By mounting the photographic film 480 on the film holder 400 having the above structure, the flexible photographic film 480 can be handled while being kept flat. Further, the film holder 400 holding the photographic film 480 can be positioned at a predetermined position on the document table 122 of the image reading apparatus 100 by using the positioning tab 450. Furthermore, since the area | region in which the image was formed among the photographic films 480 is located in the permeation | transmission window 412, the light irradiated with respect to the photographic film 480 is permeate | transmitted to the back surface.

  The main body 410 of the film holder 400 includes an identification hole 440 in the vicinity of the edge adjacent to the light source light reference region 430. A plurality of identification holes 440 are provided in a unique arrangement associated with the type of photographic film 480 held by the film holder 400. Thus, the image reading apparatus 100 can automatically identify the type of the photographic film 480 held by the film holder 400 placed on the document table 122.

  The film holder 400 includes a plurality of reference holes 470 arranged along the longitudinal side of the transmission window 412. As will be described later, when the film holder 400 is placed on the document table 122 of the image reading apparatus 100, the arrangement direction of the reference holes 470 coincides with the sub-scanning direction. The reference hole 470 is formed through the main body 410 and the film presser 420. Therefore, the light irradiated from one surface of the film holder 400 passes through the reference hole 470 and is emitted to the back surface.

  FIG. 6 is a view showing the structure of a film holder 401 that can hold another type of photographic film 480 that can be used in place of the film holder 400 shown in FIG. As shown in the figure, this film holder 401 is composed of a pair of positioning tabs 451, 453 and a single main body 410, which is a generally rectangular plate member, disposed along the outer periphery thereof. A pair of light source light reference regions 431 and 433 is provided.

  The film holder 401 includes a plurality of transmission windows 411 and 413 having different dimensions and shapes. One transmission window 411 has a size of a 35 mm film to which a mount is attached. The other transmission window 413 has a size of a 35 mm film strip in which six frames are continuous. As a result, by reversing the direction of placing on the document table 122, two types of photographic film 480 can be handled by a single film holder 401. Therefore, the identification holes 441 and 443 formed in the vicinity of the light source light reference regions 431 and 433 have a different arrangement from the identification holes 440 of the film holder 400 and different arrangements from each other.

  Around the transmissive window 413 on which the film strip is mounted, a film presser 423 that can be opened and closed is attached together with the main body 410 to hold the film strip. Thereby, a flexible film strip can be hold | maintained in a flat state. On the other hand, since the flatness of the film is secured by the mount, the film presser 423 is not provided in the transmission window 411 on which the film with mount is mounted. However, a notch 421 is formed on the surface of the main body 410 for the purpose of easily removing the mounted film with mount.

  FIG. 7 shows the state of the system 500 when reading an image from the photographic film 480 in the system 500 shown in FIG. As shown in the figure, when reading an image from the photographic film 480, the pressure plate 132 of the document holder 130 is removed, and the illumination window 134 and the light source 136 are exposed on the lower surface of the document holder 130. The film holder 401 holding the photographic film 480 that is a transparent original is placed on the original table 122 with the longitudinal direction thereof coinciding with the sub-scanning direction in the image reading apparatus 100. Accordingly, the reference holes 470 formed in the film holder 400 are arranged in the sub-scanning direction in the image reading apparatus 100.

  FIG. 8 is a diagram showing the optical system formed in the image reading apparatus 100 when reading an image on the photographic film 480, in contrast to FIG. As shown in the figure, a photographic film 480 that is a reading document is pressed by the document table 122 while being mounted on the film holder 400, and is positioned above the reading carriage 300. Further, the pressure plate 132 is removed from the document holder 130, and the transparent document illumination unit 302 is exposed on the upper surface of the photographic film 480.

Transparent document illumination unit 302 is guided by the guide rails 212 within the document pressing 130, parallel to the sub scanning direction is a moving direction M ₁ of the reading carriage 300, illumination moving in the direction of the arrow M ₂ in FIG. A carriage 354 is included. The fluorescent tube 352 serving as a light source for illumination is held in illumination carriage 354 moves in the direction of the arrow M ₂ in Fig together lighting carriage 354. Further, the movement of the illumination carriage 354 is synchronized with the movement of the reading carriage 300. Therefore, the area where the reading unit 312 of the reading carriage 300 reads an image is always illuminated by the fluorescent tube 352.

  Thus, the light emitted from the transmissive original illumination unit 302 toward the photographic film 480 passes through the photographic film 480 and then enters the carriage case 310 through the reading unit 312. The function of the optical system in the reading carriage case 310 is the same as that described with reference to FIG. 3, and thus the image on the photographic film 480 that is a transparent original is converted into an electrical signal by the CCD 340 and becomes image information.

  FIG. 9 is a diagram schematically illustrating an optical phenomenon that occurs in the optical system in the reading carriage 300 with respect to the illumination light emitted from the transparent original illumination unit 302. In order to simplify the explanation, the optical system is drawn by a single reflecting mirror 320 in FIG.

As shown in the figure, illumination emitted from the fluorescent tube 352 with respect to the fluorescent tube 352, the reflecting mirror 320, and the CCD 340 that move in synchronization with each other in the directions indicated by arrows M ₁ and M ₂ with the photographic film 480 interposed therebetween. The light passes through the photographic film 480 which is a transmission original, is reflected by the reflecting mirror 320, and is received by the CCD 340. Here, one point F ₁ on the photographic film 480 forms an image at one point F ₂ on the surface of the CCD 340 and is converted into an electrical signal according to the illuminance.

  The relationship between the image on the photographic film 480 and the read image obtained from the CCD 340 as described above is constant through the movement of the fluorescent tube 352 and the reading carriage 300 in the sub-scanning direction. However, in practice, the movement speed of the reading carriage 300 and the fluorescent tube 352 is inevitably changed. For this reason, the read image may be deformed along the sub-scanning direction.

  FIG. 10 is a diagram for explaining deformation and misalignment that occur in a read image obtained by the CCD 340 and a correction method thereof when the traveling speed of the reading carriage 300 changes. However, here, a single color read image is shown.

As shown in the figure, when the moving speeds of the reading carriage 300 and the fluorescent tube 352 change with respect to the fixed photographic film 480, the reading clock of the CCD 340 is constant, so that the reading position on the photographic film 480 is shifted. . Further, the shape of the read image is expanded and contracted in the sub-scanning direction according to the speed fluctuation. In the example shown in FIG. 10, for example, since the carriage 300 read at time t ₂ has progressed before the ideal position, CCD340 is before the movement direction than the original position reference holes 470 should be read at time t ₂ Read by side. Further, in the example shown in the figure, for example, since the carriage 300 read at time t2 has a great rate in the positive direction of the moving direction, CCD340 shrank the reference holes 470 should be read at time t ₂ in the direction of movement ellipse Read as.

  However, since it is known in advance that the shape of the reference hole 470 is, for example, a perfect circle and arranged at equal intervals, the shape and position of the image obtained by the illumination light that has passed through the reference hole 470 are determined. By applying a correction process equivalent to the process of correcting to match the shape and position to the image read from the photographic film 480, the read image resulting from fluctuations in the moving speed of the reading carriage 300 and the fluorescent tube 352 is obtained. Can be corrected. Here, both the shape and position of the reference hole 470 may be corrected, but one may be simply corrected.

  FIG. 11 is a diagram showing the optical phenomenon shown in FIG. 9 in more detail. As shown in the figure, the illumination light incident on the CCD 340 is separated into three primary colors of red light (R), green light (G) and blue light (B) by the color filter 341, and a dedicated light receiving element for each color band. Light is received by 342, 344, and 346 and converted into an electrical signal. Therefore, at a certain timing, light transmitted through different positions on the photographic film 480 is received by the light receiving elements 342, 344, and 346 corresponding to the respective colors. Note that a plurality of light receiving elements 342, 344, and 346 are arranged in a direction perpendicular to the paper surface of FIG. 11 to read a linear image.

  In the image reading apparatus 100, the difference in position of the light receiving elements 342, 344, and 346 for each color in the CCD 340 as described above is regularly corrected as “correction between RGB lines”. However, since an image at one position on the photographic film 480 is read at different timings, the reading condition varies depending on the color due to fluctuations in the traveling speed of the reading carriage 300 and the fluorescent tube 352, backlash between the movable members, and the like. It may change. In particular, when a very high reading resolution is required as in reading a photographic film 480, the quality of the read image is not negligible.

  FIG. 12 is a diagram showing the positional deviation and deformation of the read image shown in FIG. 10 together with red light (R), green light (G), and blue light (B). As shown in the figure, when the traveling speeds of the reading carriage 300 and the fluorescent tube 352 change and deviate from the ideal positions, the misalignment and deformation of the reading image occur for each reading pixel 342, 344, 346 of each color. .

FIG. 13 is a diagram for explaining a resolution reduction of a read image caused by the phenomenon shown in FIG. 12 and a correction method thereof. As shown in the figure, the read image is formed by combining the read pixels for each color for each of the read pixels 342, 344, and 346. However, when attention is paid to each of the lines L _{2 to} L ₆ on the image, a color shift and a deformation different from each other occur simultaneously for each pixel. When such read pixels are combined, the quality of the read image is significantly reduced.

  On the other hand, as described with reference to FIG. 10, it is known in advance that the shape and arrangement of the reference holes 470 are constant. Accordingly, by correcting the shape of the read image obtained in each of the read pixels 342, 344, and 346 by the illumination light that has passed through the reference hole 470 so as to match the shape of the reference hole 470, it is possible to deform the images of the colors. The difference is eliminated. Further, by applying such correction to the read image read from the photographic film 480, effective correction can be performed on an image having an arbitrary shape and color. In this way, it is possible to correct deterioration of the read image due to fluctuations in the moving speed of the reading carriage 300 and the fluorescent tube 352, and to improve the resolution of the read image.

  FIG. 14 is a plan view showing a film holder 402 having another structure. As shown in the figure, the shape of the film holder 402 is similar to the film holder 400 shown in FIG. The film holder 402 shown in FIG. 14 has a plurality of reference holes 475 along the short side of the transmission window 412 in addition to the reference holes 470 formed along the long side of the transmission window 412. That is, when the film holder 402 is placed on the document table 122 of the image reading apparatus 100, the reference holes 475 are arranged in the main scanning direction. By using such a reference hole 475, the resolution distribution for the photographic film 480 can be detected and corrected two-dimensionally in detail as will be described later.

  Furthermore, as described with a dotted line in the drawing, a reference hole 477 can be further provided at a position symmetrical to the reference hole 475 with respect to the transmission window 412. Thereby, as will be described later, the distribution of deviation in the sub-scanning direction can be detected in more detail. However, the correction amount using the reference hole 477 arranged on the end side in the sub-scanning direction is detected after all the transmission windows 412 are scanned. Accordingly, the correction for the read image is executed in a lump after completing the reading operation.

FIG. 15 is a diagram illustrating a method of correcting the resolution when using a film holder 402 having a plurality of reference holes 470, 475, and 477 arranged in the sub-scanning direction and the main scanning direction, respectively. As shown in the figure, the region of the transmission window 412 of the film holder 402 is separated from the reference holes 470,475,477 adjacent to one another equidistant _D X, at the position of _{D Y,} it is arranged two-dimensionally It is divided into a plurality of small areas. As the correction amount for the image included in each small region, a correction amount calculated from the correction amount detected in the reference holes 470, 475, and 477 corresponding to each small region is used. That is, for example, as the correction amount in the region R _JK indicated by hatching in the drawing, a value calculated by dividing the displacement detected by the reference holes J and K according to the distance to the region R _JK is used. Thereby, an appropriate correction amount is used for both the sub-scanning direction and the main scanning direction, and the read image can be corrected more precisely.

  FIG. 16 is a cross-sectional view illustrating one cross-sectional shape of the reference holes 470, 471, 475, and 477 used in the above-described application. As shown in the figure, in the film holders 400, 401, 402, reference holes 470, 471, 475, 477 are formed in the vicinity of the transmission windows 411, 412. For this reason, the reference holes 470, 471, 473 are formed around the transmission windows 411, 412 having the film holders 420, 423, through holes 472 formed in the film holders 420, 423, and through holes formed in the main body 410. 474 and 474.

  The light incident on the light receiving elements 342, 344, and 346 of the CCD 340 does not necessarily pass through the reference hole 470 vertically. For this reason, when the reference hole 470 has a cylindrical inner surface shape, the shape of the image formed by the light transmitted through the reference hole changes due to the change in the incident angle of the light. On the other hand, as shown in FIG. 15, by reducing the thickness of the innermost peripheral tip E in the through hole 474 forming the reference hole 470, deformation of the transmitted light image due to the incident angle of light can be suppressed. .

Therefore, as shown in FIG. 16, by making the inner surface shape of at least one of the through holes 472 and 474 into a tapered shape, vignetting due to the inner wall of the reference hole is eliminated, and the image by transmitted light is always the tip of the innermost circumference. E is formed as a projected image. Further, as shown in the figure, in the tapered through-hole 474, the innermost peripheral tip E that determines the shape of transmitted light is the same as the surface of the photographic film 480 on which the image is formed in the light propagation direction. Preferably, the film holder 470 is formed so as to be positioned at the boundary F ₀ between the main body 410 and the film presser 420 in the film holder 470.

  FIG. 17 is a diagram schematically illustrating the form of an optical system in a reading carriage 304 having another structure. As shown in the figure, in the image reading apparatus 100, a device outside the visible light band, for example, in the infrared light band included in the light emitted from the fluorescent tube 352 is received by the CCD 340 and converted into an electrical signal. is there. An electrical signal based on this type of infrared light is used for the purpose of detecting dust or the like adhering to the photographic film 480. Thereby, clean image information can be obtained by removing noise due to the detected dust.

  However, as described above, since light having different wavelengths is received by different regions of the CCD 340, the position and shape of the detected dust may be different from the true position. Therefore, by executing the correction method described with reference to FIG. 12 also for the infrared light band, the positional deviation between the visible light band and the infrared band is corrected and the position of the dust can be detected accurately. Can do.

  FIG. 18 is a diagram schematically illustrating another correction method for variations in optical characteristics using the reference hole 470 in the optical system 305. As shown in the figure, the reading carriage 300 that moves when scanning may shift in the height direction H due to inevitable variations in mechanical accuracy. As a result, the reading carriage 300 approaches or moves away from the film holder 400 on the fixed document table 122. In the drawing, such a transition is indicated by a dotted line as a transition on the film holder 400 side.

When the shift in the height direction H of the reading carriage 300 as described above occurs, the optical path length between the film holder 400 and the CCD 340 changes. For this reason, the size of the read image obtained by the CCD 340 also changes. On the other hand, it is known that the interval W ₀ between the reference holes 470 in the film holder 400 is constant. Thus, the image information obtained from CCD340, it detected that distance _{W 1} reference hole 470 adjacent to the transition when changing the spacing _{W 2,} a high reading carriage 300 in the direction H.

  As described in detail above, the reference holes 470, 471, 473, 475, and 477 are formed in the film holders 400, 401, and 402, and the light that has passed through the holes is read by the CCD 340 to detect the deviation generated in the optical system. Therefore, it is possible to effectively compensate for a decrease in resolution due to various causes. When this process is executed, no special hardware resources are used other than providing the reference holes 470, 471, 473, 475, and 477 in the film holders 400, 401, and 402. Therefore, the existing image reading apparatus 100 is not used. Can be easily executed. The original to be corrected is not limited to photographic film, but can be effectively compensated for any type of original as long as it is held by a holder having a reference hole and is subject to image reading. Can do.

  Although the invention has been described using the embodiment, the technical scope of the invention is not limited to the scope described in the embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. Further, it is apparent from the description of the scope of claims that the embodiment added with such changes or improvements can be included in the technical scope of the present invention.

1 is a perspective view illustrating an appearance of an image reading apparatus 100 according to an embodiment. 2 is a plan view showing an internal mechanism 200 of the image reading apparatus 100. FIG. 1 is a diagram illustrating a structure of a system 500 that performs image reading using an image reading apparatus 100. FIG. 2 is a cross-sectional view showing an optical system formed when a reflective original 142 is read by the image reading apparatus 100. FIG. 4 is a plan view showing the shape of a film holder 400 used when reading an image from a photographic film 480 that is a transparent original in the image reading apparatus 100. FIG. It is a top view which shows the structure of the film holder 401 which can hold | maintain another kind of photographic film 480. FIG. The state of system 500 when reading an image from photographic film 480 is shown. 4 is a cross-sectional view showing an optical system formed when an image on a photographic film 480 is read by the image reading apparatus 100. FIG. FIG. 6 is a diagram schematically illustrating an optical phenomenon that occurs with illumination light emitted from a transparent original illumination unit 302. FIG. 6 is a diagram for explaining a deformation of a read image caused by a change in moving speed of a reading carriage and a correction method thereof. It is a figure explaining the other cause in which the resolution of a reading image deteriorates. FIG. 6 is a diagram for explaining a deformation of a read image caused by a change in moving speed of a reading carriage and a correction method thereof. It is a figure explaining the fall of the reading resolution resulting from the phenomenon shown in FIG. 12, and its correction method. It is a top view which shows the film holder 402 which has another structure. It is a figure which illustrates the correction method at the time of using the film holder 402. It is a figure which shows the cross-sectional shape of one reference hole 470,471,473. It is a figure which shows typically the optical system in the reading carriage 304 which has another structure. It is a figure which shows typically the other optical phenomenon which a deformation | transformation of a read image produces.

Explanation of symbols

100 image reading device, 110 lower case, 120 upper case, 122 document table, 130 document pressing, 132 pressure plate, 134 illumination window, 136 light source, 140 document, 142 reflection document, 200 internal mechanism, 210, 212 guide rail, 212 bracket , 222 timing belt, 224 pulley, 226 stepping motor, 228 gear, 230 circuit board, 232, 234 connector, 240 flat cable, 250 power supply unit, 300, 304 reading carriage, 302 transmission original illumination unit, 305 optical system, 310 carriage Case, 312 Reading unit, 314 Groove, 320, 322, 324, 326, 328 Reflector, 330 Lens unit, 332 Lens, 334 Lens holder, 340 CCD, 341 Color filter 342, 344, 346 Light receiving element, 350, 352 Fluorescent tube, 354 Illumination carriage, 400, 401, 402 Film holder, 410 Main body, 411, 412, 413 Transmission window, 420, 423 Film press, 421 Notch, 424 Tab 430, 431, 433 Light source light reference area, 440, 441, 443 Identification hole, 450, 451, 453 Positioning tab, 460 Film holder detection area, 470, 471, 473, 475, 477 Reference hole, 472, 474 Through hole 480 Photo film, 500 system, 510 information processing device, 512 keyboard, 514 mouse, 516 disk drive, 518 connection cable, 520 display device

Claims (12)

A light source that irradiates illumination light having a predetermined wavelength bandwidth from one side of a transmissive original, and an image included in a linear region on the transmissive original by receiving light emitted from the light source and transmitted through the transmissive original. And a line sensor that outputs an electrical signal corresponding to the above, and moves in the sub-scanning direction intersecting the longitudinal direction of the linear area to scan the transparent original, thereby reading the image of the entire transparent original as image information. A reading carriage;
An opening that encloses an image formed on a transparent original, a holding part that holds an edge of the transparent original around the opening, and a through-hole in a direction perpendicular to the transparent original held in the holding part A holder having a plurality of reference holes arranged along the scanning direction of the reading carriage;
At least one of the known shape and arrangement of the reference hole is detected for the read image formed by the line sensor by receiving the reference light that has passed through the reference hole in the illumination light, and the detected at least one of the at least one detected And a correction unit for generating image information by executing a process of correcting the reference hole so as to match at least one of the known shape and arrangement of the reference hole for each of different wavelength bands included in the reference light. Image reading device.   The image reading apparatus according to claim 1, wherein the plurality of reference holes are arranged along a pair of sides parallel to a scanning direction of the reading carriage among the sides of the opening.   The image reading apparatus according to claim 1, wherein a plurality of reference holes are further provided along a longitudinal direction of a linear region read by the line sensor.   The image reading apparatus according to claim 3, wherein a plurality of the plurality of reference holes are respectively arranged along three sides including a side parallel to a scanning direction of the reading carriage among the sides of the opening. The wavelength band includes three bands of red, blue, and green among visible light bands included in the illumination light,
The image reading apparatus according to claim 1, wherein the line sensor includes a light receiving element that receives each of the three bands, and receives a position of the transparent original at different timings in the movement in the sub-scanning direction.   The image reading apparatus according to claim 1, wherein the wavelength band includes a specific band in a visible light band included in the illumination light and a specific band included in an infrared band included in the illumination light.   The correction unit changes the optical path length of the reference light based on a light receiving interval of reference light that has passed through a pair of adjacent reference holes among the plurality of reference holes and a known interval between the pair of reference holes. The image reading apparatus according to claim 1, wherein the image information is detected and corrected so as to cancel the change in the image information due to the change.   The image reading apparatus according to claim 1, wherein the innermost circumference of each of the plurality of reference holes is reduced in thickness in the propagation direction of the reference light.   2. The correction unit according to claim 1, wherein the correction unit corrects image information read from each region of the transparent original based on a positional deviation detected from a reference hole closest to each of the plurality of reference holes. Image reading device.   The correction unit corrects image information of each area of the transparent document based on a correction amount calculated based on a positional deviation detected from a pair of reference holes sandwiching the area among the plurality of reference holes. Item 2. The image reading apparatus according to Item 1. A light source that irradiates illumination light having a predetermined wavelength bandwidth from one side of a transmissive original, and an image included in a linear region on the transmissive original by receiving light emitted from the light source and transmitted through the transmissive original. And a line sensor that outputs an electrical signal corresponding to the above, and moves in the sub-scanning direction intersecting the longitudinal direction of the linear area to scan the transparent original, thereby reading the image of the entire transparent original as image information. A reading carriage;
An opening that encloses an image formed on a transparent original, a holding part that holds an edge of the transparent original around the opening, and a through-hole in a direction perpendicular to the transparent original held in the holding part A holder having a plurality of reference holes arranged along the scanning direction of the reading carriage;
A correction method for correcting image information in an image reading apparatus comprising:
A procedure for forming a read image by the line sensor by receiving the reference light that has passed through the reference hole in the illumination light;
Detecting at least one of the known shape and arrangement of the reference hole from the read image;
A correction method comprising a step of correcting the detected at least one to match at least one of the known shape and arrangement of the reference hole for each different wavelength band included in the reference light . A light source that irradiates illumination light having a predetermined wavelength bandwidth from one side of a transmissive original, and an image included in a linear region on the transmissive original by receiving light emitted from the light source and transmitted through the transmissive original. And a line sensor that outputs an electrical signal corresponding to the above, and moves in the sub-scanning direction intersecting the longitudinal direction of the linear area to scan the transparent original, thereby reading the image of the entire transparent original as image information. A reading carriage;
An opening that encloses an image formed on a transparent original, a holding part that holds an edge of the transparent original around the opening, and a through-hole in a direction perpendicular to the transparent original held in the holding part A holder having a plurality of reference holes arranged along the scanning direction of the reading carriage;
A correction program for causing the image reading apparatus to execute processing for correcting image information in an image reading apparatus comprising:
Forming a read image by the line sensor by receiving reference light that has passed through the reference hole in the illumination light; and
Detecting at least one of a known shape and arrangement of the reference hole from the read image;
And performing a process of correcting the detected at least one to match at least one of the known shape and arrangement of the reference hole for each of different wavelength bands included in the reference light. program.

Images