JP2007235737A - Defective pixel correction method, and defective pixel correction system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a defective pixel correction technique for calculating a defect judgment reference for detecting a defect precisely, as easily as possible. <P>SOLUTION: The defective pixel correction system is provided with a defect judgment threshold calculation part 52a which sequentially calculates first visible image data and first infrared ray image data read by each main scanning line in the case of pre-scanning; a defect judgment threshold curve generation part 52b which prepares a defect judgment threshold curve over the whole region in a sub-scanning direction from the defect judgment threshold; and a pixel correction processing part 53 which detects defective pixels in second visible image data read in the case of main scanning using the defect judgment threshold curve and corrects the defective pixel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention results from film scratches in visible light image data using visible light image data read from a photographic film based on visible light and infrared light image data read based on infrared light. The present invention relates to a defective pixel correction technique that determines a defective pixel, detects the determined defective pixel, and corrects the defective pixel.

  A photographic film may have defects such as scratches, dust, and dirt on its surface. Therefore, when reading an image from a photographic film having such defects and outputting a photographic print, such defective portions are referred to as brightness adjustment processing (called density adjustment processing in order to express pixel values of image data by density). However, in order to distinguish it from the density adjustment processing normally performed in photographic image processing, it will be referred to as luminance adjustment processing here) and a technique for correction by image processing such as interpolation processing is known.

  As a brightness adjustment processing method, for example, unlike visible light, infrared light is hardly affected by an image reflected in a photographic film and is only affected by scratches, dust, etc. It is known that correction is performed by luminance adjustment processing. Specifically, infrared light and visible light are transmitted through a photographic film, and a pixel value (expressed by density or brightness) of image data by infrared light is a predetermined threshold value or less. And add the amount of attenuation of the infrared light of the defective portion with respect to the normal portion to the pixel value of each color component (red (R), green (G), blue (B)) of the defective portion. This is a technique for adjusting the luminance of the pixel values of the respective color components in the defective portion according to the normal portion by increasing the luminance (see, for example, Patent Document 1).

  However, since such brightness adjustment processing is based on the premise that the pixel values of the respective color components are attenuated by the same amount in the defective portion, as in the case where the emulsion surface of the photographic film is scratched, When the amount of attenuation of the pixel value for each color component is different, the defective portion cannot be corrected appropriately. In such a case, correction of a defective portion determined as a defect using a threshold value that is the same as or lower than the predetermined threshold value used in the luminance adjustment processing is performed using the pixel values of surrounding normal pixels. The technique of interpolation processing to be performed is used. At that time, simply applying the pixel values of adjacent normal pixels to the defective part cannot be corrected appropriately when there is a pattern or boundary in the defective part. There is known an algorithm that detects and applies a pixel value of a normal pixel that exists along the boundary direction to a defect portion to perform correction reflecting a pattern, a boundary, and the like. Specifically, image feature amounts such as pixel value differences of normal pixels and distances between normal pixels are calculated along a plurality of different directions from the defective portion, and the normal pixels existing in the plurality of directions are further calculated. An interpolated value for each direction is obtained from the pixel value, and a final corrected value is obtained by interpolation by calculating a weighted average of the interpolated values for each direction using the image feature amount as a weight (see, for example, Patent Document 2). .

  As a premise for applying the above-described defective pixel correction algorithm, it is important to first accurately determine a defect determination standard (threshold value) for detecting a defective pixel. For this purpose, the main scanning line extending in the main scanning direction is used to sequentially scan in the sub-scanning direction orthogonal to the main scanning direction so that the photographic film is read and scanned during the first scan (pre-scan). A defect determination criterion is calculated using the first visible light image data read based on the light and the first infrared light image data read based on the infrared light, and a second scan following the first scan ( It is preferable to detect defective pixels in the second visible light image data from the second visible light image data and the second infrared light image data read from the photographic film during the main scan) using the defect determination criterion. . For example, an infrared average value, which is an average value of pixel values of all pixels, is calculated from infrared light image data for one frame (photographed frame image), and the first variable X = red image in consideration of red leakage The pixel value of (red image data) −the pixel value of the infrared image + the infrared average value and the second variable Y = the pixel value of the red image are obtained for each pixel, and the regression equation Y = A method has been proposed in which the coefficients a and b of aX + b are calculated and the defect detection threshold value is obtained as “infrared average value + b” (for example, see Patent Document 3).

JP-A-11-98370 (pages 15-16, FIG. 4) JP 2001-78038 A (Pages 7-8, FIGS. 4-5, FIG. 8) Japanese Patent Laying-Open No. 2005-80237 (paragraphs 0036 and 0046, FIG. 5)

  In the defective pixel correction technique described above, the threshold for defect detection is calculated for each frame (photographed frame image) using the visible light image data and infrared light image data stored in the image memory during the prescan, and the main scan is performed. This is used for defective pixel correction processing of image data at the time. For this reason, it is necessary to cut out a shot frame image from image data having an elongated data area of one photographic film obtained by pre-scanning, and to calculate a threshold value as a defect determination standard for each of the cut out shot frame images.

  In view of the above situation, an object of the present invention is to provide a defective pixel correction technique that calculates a defect determination standard that enables accurate defect detection as easily as possible.

  In order to solve the above-described problem, the photographic film is scanned from the photographic film to the visible light during the first scanning by sequentially scanning in the sub-scanning direction orthogonal to the main scanning direction using the main scanning line extending in the main scanning direction. A defect determination criterion is calculated using the first visible light image data read based on the first infrared light image data read based on the infrared light, and the second scan following the first scan The defective pixel in the second visible light image data is detected from the second visible light image data and the second infrared light image data read from the photographic film by using the defect determination criterion, and the defective pixel is corrected. In the defective pixel correcting method, the first visible light image data read in each main scanning line and the first red are used as defect determination criteria calculated through the first scan. A defect determination threshold is sequentially calculated from the optical image data, a defect determination threshold curve is created from the defect determination threshold over the entire sub-scanning direction, and defect pixels in the second visible light image data are generated using the defect determination threshold curve. Perform detection.

  In this method, in the first scan, also referred to as prescan, the photographic film is read from the start side to the end side in the sub-scanning direction, which is the longitudinal direction of the photographic film, sequentially using main scanning lines that coincide with the transverse direction of the photographic film. However, the defect determination threshold value is calculated one after another from the first visible light image data and the first infrared light image data read in each main scanning line, and the discreteness in the sub-scanning direction thus obtained is obtained. A defect determination curve that connects these discrete defect determination thresholds is created from a plurality of typical defect determination thresholds. Since this defect determination curve is a curve along the longitudinal direction of the photographic film, each main scan used for reading the second visible light image data and the second infrared light image data in the second scan, which is also called a main scan. The defect determination threshold value at the position of the line in the photographic film longitudinal direction (sub-scanning direction) can be obtained from this defect determination curve. That is, instead of obtaining a fixed defect determination threshold value for each photographed frame image and correcting defective pixels in the photographed frame image as in the prior art, it is discrete for each minute region of the photographic film scanned by one main scanning line. A defect determination threshold that is uniquely derived from a continuous defect determination curve created from these discrete defect determination thresholds corresponding to the position in the photographic film longitudinal direction (sub-scanning direction). Using this, defective pixel correction of the shot frame image is performed. Thereby, excellent defect detection becomes possible.

  In particular, the present invention has a feature that a discrete defect determination threshold value is obtained in the longitudinal direction (sub-scanning direction) of the photographic film during the first scan. Therefore, the first scan is performed at rough intervals in the sub-scanning direction. If the second scan is performed at a lower speed than the prescan as the main scan, which sequentially scans the photographic film at a dense interval in the sub-scanning direction as compared to the first scan. The number of discrete defect determination thresholds is reduced, and the processing load for calculating the defect determination threshold is reduced. Further, by speeding up the first scan, the processing time of the entire captured frame image acquisition including the defective pixel correction processing is also shortened. Furthermore, even if the number of discrete defect determination thresholds decreases, the defect determination curve created using a statistical method from these discrete defect determination thresholds is adapted to the position of the processing target image data each time. Therefore, accurate defect detection can be expected.

  In the conventional pre-scan (first scan), a resolution of 70 to 100 DPI was used to obtain the image quality at the monitor display level. However, if only the discrete defect determination threshold is calculated in the first scan, It is also possible to perform interlaced scanning in the sub-scanning direction with a resolution that is very coarse compared to the prior art, for example, 10 DPI or less, and the scanning speed can be significantly increased.

  Employs the idea of creating a continuous defect judgment curve from discrete defect judgment thresholds, and film characteristics that do not depend on the characteristics of the shot frame image from the snook area formed between the shot frame image areas The first infrared light image data includes at least data read from a snook area formed between the photographed frame image areas formed on the photographic film. This is also a preferred method for obtaining a defect determination threshold value that enables excellent defect detection with a small calculation processing load.

  In the present invention, a program for causing a computer to execute a method for correcting a defective pixel using the above-described defect determination threshold curve and a medium on which the program is recorded are also subject to rights.

  Further, according to the present invention, based on the visible light from the photographic film during the first scan in which the photographic film is read and scanned by sequentially scanning in the sub-scanning direction orthogonal to the main scanning direction using the main scanning line extending in the main scanning direction. A defect determination criterion is calculated using the first visible light image data read in this way and the first infrared light image data read based on the infrared light, and the photo is taken during the second scan following the first scan. When detecting defective pixels in the second visible light image data using the defect determination standard from the second visible light image data and the second infrared light image data read from the film, as described above. A defective pixel correction system that implements a method of correcting a defective pixel using a defect determination threshold curve is also subject to rights, and the defective pixel correction system passes through the first scan. From the defect determination threshold value, a defect determination threshold value calculation unit that sequentially calculates a defect determination threshold value from the first visible light image data and the first infrared light image data read by each main scanning line as a defect determination reference calculated in A defect determination threshold curve generating unit that creates a defect determination threshold curve over the entire sub-scanning direction, and detecting a defective pixel in the second visible light image data using the defect determination threshold curve, and correcting the defective pixel. And a pixel correction processing unit to be performed. Naturally, such a defective pixel correction system can also obtain the effects described in the above-described defective pixel correction method, and can further incorporate the above-described preferred embodiment.

  Other features and advantages of the present invention will become apparent from the following description of embodiments using the drawings.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an external view showing a photographic print system employing a defective pixel correction system according to the present invention. An operation station OS provided with a film scanner 3 that reads a captured image frame (referred to as film) as digital image data, a controller 5 that performs image processing on the acquired image data and creates print information, and the like from the operation station OS The printing station 2 includes a print station PS that performs exposure processing and development processing on the photographic paper 2 based on the print information to create a photo print 2a. The controller 5 is basically composed of a general-purpose personal computer, and is mounted with a defective pixel correction system according to the present invention. The personal computer includes a monitor 4a for displaying an operation screen of the photo print system, a media reader 4b for reading an image from a memory card such as a digital camera, and a keyboard 4c used for operation input by an operator.

  As shown in FIG. 2, the print station PS draws out the roll-shaped photographic paper 2 stored in the two photographic paper magazines 11 and cuts it into a print size by the sheet cutter 12. On the photographic paper 2, print processing information such as color correction information and frame number is printed on the back surface of the photographic paper 2 by the back print unit 13, and the photographed image is exposed on the front surface of the photographic paper 2 by the exposure print unit 14. The exposed photographic paper 2 is sent to a processing tank unit 15 having a plurality of development processing tanks for development processing. After drying, the photographic paper 2, that is, the photographic prints 2a, sent to the sorter 17 from the transverse feed conveyor 16 at the top of the apparatus is collected in a plurality of trays 17a of the sorter 17 in a state of being sorted in order units (FIG. 1). reference).

  A photographic paper transport mechanism 18 is laid to transport the photographic paper 2 at a transport speed in accordance with various processes for the photographic paper 2 described above. The photographic paper transport mechanism 18 is composed of a plurality of nipping and transporting roller pairs including a chucker type photographic paper transport unit 18a disposed before and after the exposure unit 14 in the photographic paper transport direction.

  The exposure print unit 14 applies R (red) and G (green) to the photographic paper 2 conveyed in the sub-scanning direction based on print information such as print data from the operation station OS along the main scanning direction. A line exposure head for irradiating laser beams of the three primary colors B (blue) is provided. The processing tank unit 15 includes a color developing tank 15a for storing a color developing processing liquid, a bleach-fixing tank 15b for storing a bleach-fixing processing liquid, and a stabilizing tank 15c for storing a stable processing liquid.

  The film scanner 3 is a film scanner provided with components for correcting defective pixels, and as main components, an illumination optical system 31, a zoom lens 32 as an imaging optical system, and incident light as visible light and infrared light. A dichroic mirror 33 for dividing light, a visible light sensor unit 34, and an infrared light sensor unit 35 are provided. The illumination optical system 31 includes a halogen lamp or a light emitting diode as a light source, and a mirror tunnel or a diffusion plate that dimmes light from the light source. The visible light sensor unit 34 includes three CCD arrays 34a each equipped with a color filter suitable for detecting a visible light image composed of three basic color components (for example, R, G, B) of the film 1, and these A visible light signal processing circuit 34 b that processes the visible light signal detected by the CCD array 34 a to generate R, G, B image data composed of basic color components and transfers the image data to the controller 5. On the other hand, the infrared light sensor unit 35 has only infrared light branched from the dichroic mirror 33 in order to detect the state of scratches caused by defective pixels on the film 1 as an infrared light image. CCD array 35a arranged to receive the light, and an infrared light signal processing circuit 35b for processing the infrared light signal detected by the CCD array 35a to generate infrared light image data and transferring it to the controller 5. It has. A film transport mechanism 36 for transporting the film 1 in the longitudinal direction is disposed between the illumination optical system 31 and the imaging optical system, and illumination light from the illumination optical system 31 is transmitted to the film transport mechanism 36. A slit 36a extending in the transverse direction of the photographic film 1 is formed so as to pass through the photographic film 1 positioned on the line 36 in the form of line light. The line-shaped slit 36a serves to cause the photographic film 1 to have a CCD array 34a extending in the direction perpendicular to the film transport direction, that is, in the main scanning direction, in units of a minute width region as a main scanning line extending in the main scanning direction. It is read by the CCD array 35a. The resolution of the CCD array 34a and the CCD array 35a is about 4000 DPI.

  In the film scanner 3 configured as described above, when the film 1 is inserted, illumination light including visible light and infrared light is irradiated onto the film 1 and the transmitted light is photoelectrically converted, whereby a visible light sensor is obtained. Visible light image data is output from the unit 34, and infrared light image data is output from the infrared light sensor unit 35 in units of the main scanning lines described above. By the feeding operation of the film 1 in the sub-scanning direction by the film transport mechanism 36, the film 1 is sequentially read by the visible light sensor unit 34 and the infrared light sensor unit 35 in units of main scanning lines, and R, G, B The color component image signal and the infrared component image signal are photoelectrically converted and sent to the controller 5 as raw digital image data. Such an illumination optical system 31, imaging optical system 32, and visible light sensor unit 34. Each control of the infrared light sensor unit 35 and the film transport mechanism is performed by an operation command from the controller 5.

  The film scanner 3 includes a pre-scan as a first scan for reading and scanning the photographic film 1 at a rough interval in the sub-scanning direction with a line-shaped main scanning line while conveying the film 1 at a high speed, and one side in the pre-scan. A main scan is performed as a second scan in which the photographic film 1 is read and scanned at a fine interval in the sub-scanning direction along the line-shaped main scanning line while the film 1 conveyed at a low speed is conveyed. As schematically shown in FIG. 3A, in pre-scanning, the film 1 is read with several to several tens of main scanning lines in one frame of a captured frame image, and between adjacent captured frame images. Whereas the snook area that is positioned is also treated as a reading target area, in the main scan, the film 1 is read by 1000 or more main scanning lines in one frame of the captured frame image, and only the captured frame image is read. The snooker area is excluded.

  The controller 5 has a CPU as a core member, and a functional unit for performing various processes on input data is implemented by hardware and / or software, but the functional unit particularly related to the present invention. As shown in FIG. 4, visible light image data acquired by the visible light sensor unit 34 and infrared light image data acquired by the infrared light sensor unit 35 during the pre-scan and the main scan. , An input processing unit 51 that performs preprocessing as necessary and develops it at a predetermined address of the memory 50, visible light image data (referred to as first visible light image data) and infrared light image data (previously scanned) A defect determination criterion calculation unit 52 that calculates a defect determination criterion using the first infrared light image data), and a film during the main scan following the pre-scan The defect determination standard calculated by the defect determination standard calculation unit 52 from the visible light image data (referred to as second visible light image data) and the infrared light image data (referred to as second infrared light image data) read from Is used to detect defective pixels in the second visible light image data and correct the defective pixels, and print image data (visible light image data) developed in the memory 50. An image processing unit 54 that performs various image processing such as color correction, filtering (blurring, sharpness, etc.) and trimming on the image, captures image data and other display items into the video memory, and converts the image developed in the video memory into a video. The video signal is converted into a video signal by the controller and sent to the monitor 4a. Print data generation unit 56 that converts image data for printing to print data and transfers it to the exposure print unit 14 of the print station PS, and an operation command input through the keyboard 4c or the like under an operation screen created using the GUI And a print management unit 57 that controls each functional unit based on a preprogrammed operation command.

  The defect determination reference calculation unit 52 sequentially sets a defect determination threshold value for each main scanning line from the first visible light image data and the first infrared light image data read in each main scanning line in the sub-scanning direction during pre-scanning. Defect determination threshold value calculation unit 52a to be calculated, and continuous defect determination from the group of discrete defect determination threshold values calculated in the defect determination threshold value calculation unit 52a in the sub-scanning direction (longitudinal direction of the film 1) A defect determination threshold curve generation unit 52b that creates a threshold curve is constructed.

Since the defect detection in the present invention uses a phenomenon in which the pixel value (density value or luminance value) corresponding to the defect area is lower than the average pixel value, the defect determination threshold is the first infrared. The value depends on the average value of the pixel values of all the pixels included in the light image data. Various algorithms for calculating the defect determination threshold have been proposed, and the following algorithm is used for calculation of the defect determination threshold by the defect determination threshold calculator 52a.
(1) An infrared average value, which is an average value of pixel values included in one line, is calculated from the first infrared light image data for one main scanning line.
(2) A red pixel value is read from the first visible light image data for one main scanning line.
(3) The corresponding infrared pixel value is subtracted from the red pixel value and the infrared average value calculated in (1) is added to obtain the first variable: X. Further, the red pixel value is set as a second variable: Y.
(4) The least variable method is applied to the first variable group: X and the second variable group: Y obtained for one main scanning line to obtain the coefficients a and b of the regression equation Y = aX + b.
(5) The coefficient b (Y-intercept) obtained in (4) represents the amount of decrease in the infrared average value due to the influence of defects such as scratches and dust and from the values of pixels without defects. Therefore, a value obtained by adding the value of b to the infrared average value is set as a defect determination threshold value.

  The defect determination threshold value calculated in this way is obtained for each main scanning line as schematically shown in FIG. 5, and these are determined as a group of discrete defect determination threshold values extending in the film longitudinal direction. Become. The discrete defect determination threshold value group becomes a defect determination threshold curve which is a continuous curve using a well-known mathematical method by the function of the defect determination threshold curve generation unit 52b. This defect determination threshold curve is handled in the form of a curve equation or a linear equation group, or in the form of a calculation table for the convenience of computer processing. The defect determination threshold curve as the defect determination standard in the present invention can be implemented in all forms including such a form.

  In the defective pixel correction processing unit 53, the sub-scanning direction of the main scanning line for each second infrared visible light image data sent in units of main scanning lines that are sub-scanned at dense intervals during the main scan. The defect determination threshold obtained from the defect determination threshold curve based on the position is used to find a defective pixel and the address is recorded, and the defect determination threshold obtained from the defect determination threshold curve is made more strict. The second defective pixel map 53b recorded using the threshold value, the luminance adjustment processing unit 53c for correcting the defective pixel by the luminance adjustment processing using the first defective pixel map 53a, and the interpolation using the second defective pixel map 53b And an interpolation processing unit 53d for correcting defective pixels by processing.

  The luminance adjustment processing executed by the luminance adjustment processing unit 53c is a difference between the average value of the pixel values of all the normal pixels included in the second infrared light image data and the pixel value of each defective pixel. The amount of attenuation of the pixel value due to the scratch is added to the pixel value for each color component (RGB) of each defective pixel included in the second visible light image data, so that all defective pixels included in the visible light image data are added. This is a process for adjusting the brightness, and various algorithms are known (for example, Japanese Patent Laid-Open No. 2000-115464, page 5, FIG. 3, Japanese Patent Laid-Open No. 2001-078038, pages 16-17). Here, as schematically shown in FIG. 6, here, the difference between the pixel value of the pixel regarded as the defective portion in the infrared data and the pixel value of the surrounding normal pixel Infrared defect depth based on Dfm, n And calculating the visible light defect depth Rfm, n, Gfm, based on the difference between the pixel value of the corresponding pixel in the visible light data of each of the R light, G light, and B light and the pixel value of the surrounding normal pixels. n, Bfm, n are calculated, and based on these, the influence of visible light data due to defects and the influence of infrared light data due to defects due to the difference in wavelength or refractive index between visible light and infrared light An algorithm (for example, Japanese Patent Application Laid-Open No. 2005-142621) that calculates a correction coefficient for correcting the shift of the defect pixel and corrects the defect pixel by brightness adjustment based on the correction coefficient and the infrared defect depth Dfm, n of each defective pixel. Publication) is adopted.

  As the interpolation processing executed by the interpolation processing unit 53d, the distance from the plurality of normal pixels around the defective pixel recorded in the second defective pixel map 53b is obtained, and the pixel value of the normal pixel is determined according to the distance. The process of correcting the defective pixel by calculating the weighted average and calculating the correction value of the defective pixel, and in order to perform an appropriate interpolation process that reflects the boundary of the image as accurately as possible, the direction of each defective pixel in multiple directions The interpolation value based on the pixel value of the normal pixel existing along the line and the weighting coefficient in each direction based on the pixel value of the normal pixel existing along each direction line are obtained, and the weighted average value using this An algorithm (for example, Japanese Patent Application Laid-Open No. 2005-252559) that corrects defective pixels by calculating the above can be adopted. In any case, since the interpolation processing algorithm is complicated and the processing load is large, this interpolation processing unit 53d is omitted when precise defective pixel correction is not required.

A processing procedure for correcting defective pixels in the photo print system configured as described above will be described below with reference to FIG.
First, the film scanner 3 is driven in the pre-scan mode, and the first visible light image data and the first infrared light image data in units of main scanning lines acquired by the visible light sensor unit 34 and the infrared light sensor unit 35 are used. Is expanded in the memory 50 (# 01). The defect determination threshold value calculation unit 52a calculates the defect determination threshold value in each main scanning line using the first visible light image data and the first infrared light image data (# 02). When the calculation of the defect determination threshold values for all the main scanning lines is finished, the defect determination threshold curve generation unit 52b creates a defect determination threshold curve from these discrete defect determination threshold groups and forms a table (# 03). Next, the film scanner 3 is driven in the main scan mode, and the second visible light image data and the second infrared light image data acquired by the visible light sensor unit 34 and the infrared light sensor unit 35 are developed in the memory 50. (# 04). The defect determination threshold value for each scanning point in the sub-scanning direction is read from the defect determination threshold curve tabulated, and the address of the defective pixel detected using this defect determination threshold value as the defect detection reference is recorded in the first defective pixel map 53a (# 05). When performing the interpolation process, the address of the defective pixel detected using the defect determination threshold stricter than the defect determination threshold for the brightness adjustment process as a defect detection reference is recorded in the second defective pixel map 53b (# 06). Next, the luminance adjustment processing unit 53c sets the defective pixel using the first defective pixel map 53a, and the pixel value of each color component (red (R), green (G), blue (B)) of the defective pixel. On the other hand, the defective pixel is corrected by the above-described luminance adjustment process in which the luminance is increased by adding the attenuation amount of the infrared light of the defective pixel to the normal pixel (# 07). Further, the interpolation processing unit 53d performs defective pixel interpolation processing using the above-described interpolation processing algorithm (# 08).

  In this way, when the defective pixel in the shot frame image data due to scratches or dust attached to the film 1 is corrected, color correction and density correction for each shot frame image unit are performed individually. Thereafter, exposure processing and development processing based on the corrected photographed frame image data are performed, and a photographic print 2a is output.

  In the present invention, the main scanning is performed from the first visible light image data and the first infrared light image data obtained from the area covered by the main scanning line that is sub-scanned at a rough interval by the pre-scan that transports the film 1 at a high speed. A defect determination threshold value in units of lines is sequentially calculated, a continuous defect determination threshold curve is created from these discrete defect determination threshold values over the entire sub-scanning direction, and a second scan obtained by the main scan that precisely scans the film 1. By using the defect determination threshold derived from the defect determination threshold curve for the visible light image data and the second infrared light image data, excellent defective pixel detection is performed, and pixel correction for the defective pixel is realized. . At that time, the width of the main scanning line in the sub-scanning direction (longitudinal direction of the photographic film) is generally one pixel, but may be a plurality of pixels. An important point of the present invention is to create a continuous defect determination threshold curve from the discrete defect determination threshold over the entire sub-scanning direction.

  In the description of the above-described embodiment, the defective pixel correction technique according to the present invention is incorporated in a photo print system called a minilab installed in a DP shop, but is incorporated in a single film scanner. May be.

  In the above-described embodiment, the print station PS as the image output means exposes the photographic paper 2 to the photographic paper 2 by the exposure printing unit 14 equipped with a laser-type exposure engine, and uses the photographic paper 2 after the exposure. A so-called silver salt photographic printing system that employs a plurality of development processes has been adopted. Of course, the print station PS in the present invention is not limited to such a system. For example, ink is ejected onto film or paper. Various photographic printing methods such as an inkjet printing method for forming an image and a thermal transfer method using a thermal transfer sheet can be employed.

External view of photo print system incorporating defect pixel correction technology according to the present invention Schematic configuration diagram of photo print system Explanatory drawing showing the sub-scanning step of the main scanning line in the pre-scan and main scan Functional block diagram of controller Explanatory drawing which shows the procedure which calculates | requires a defect determination threshold curve Schematic explanatory diagram of the principle of brightness adjustment Flow chart of defect image correction processing

Explanation of symbols

3: Film scanner 5: Controller 34: Visible light sensor unit 35: Infrared light sensor unit 50: Memory 52: Defect determination reference calculation unit 52a: Defect determination threshold calculation unit 52b: Defect determination threshold curve generation unit 53: Image Correction processing unit 53a: first defective pixel map 53b: second defective pixel map 53c: luminance adjustment processing unit 53d: interpolation processing unit

Claims (5)

First read from the photographic film based on visible light during the first scan in which the photographic film is read and scanned by sequentially scanning in the sub-scanning direction orthogonal to the main scanning direction using the main scanning line extending in the main scanning direction. Defect determination criteria are calculated using visible light image data and first infrared light image data read based on infrared light, and read from the photographic film during a second scan following the first scan. In a defective pixel correction method for detecting defective pixels in the second visible light image data from the two visible light image data and the second infrared light image data using the defect determination criterion, and correcting the defective pixels. ,
A defect determination threshold value is sequentially calculated from the first visible light image data and the first infrared light image data read in each main scanning line as a defect determination reference calculated through the first scan,
Create a defect determination threshold curve across the entire sub-scanning direction from the defect determination threshold,
A defective pixel correction method, wherein defective pixels in the second visible light image data are detected using the defect determination threshold curve.   The first scan is performed at high speed as a pre-scan that sequentially scans the photographic film at coarse intervals in the sub-scanning direction, and the second scan sequentially scans the photographic film at a finer interval in the sub-scanning direction than the pre-scan. The defective pixel correction method according to claim 1, wherein the main scan is performed at a lower speed than the pre-scan.   3. The defective pixel correction method according to claim 1, wherein scanning is sequentially performed in the sub-scanning direction at a resolution of 10 DPI or less using the main scanning line.   The first visible light image data and the first infrared light image data include at least data read from a snook area formed between photographing frame image areas formed on the photographic film. The defective pixel correction method according to any one of claims 1 to 3, wherein First read from the photographic film based on visible light during the first scan in which the photographic film is read and scanned by sequentially scanning in the sub-scanning direction orthogonal to the main scanning direction using the main scanning line extending in the main scanning direction. Defect determination criteria are calculated using visible light image data and first infrared light image data read based on infrared light, and read from the photographic film during a second scan following the first scan. In a defective pixel correction system that detects a defective pixel in the second visible light image data from the two visible light image data and the second infrared light image data using the defect determination criterion, and corrects the defective pixel. ,
A defect determination threshold value calculation unit that sequentially calculates a defect determination threshold value from the first visible light image data and the first infrared light image data read in each main scanning line as a defect determination reference calculated through the first scan;
A defect determination threshold curve generation unit that creates a defect determination threshold curve across the entire sub-scanning direction from the defect determination threshold;
A defective pixel correction system comprising: a pixel correction processing unit that detects a defective pixel in the second visible light image data using the defect determination threshold curve.

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