JP2005057383A - Image reading apparatus and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily obtain an image of high precision even if illuminating light has an excess spectrum, with respect to an image reading apparatus for optically reading the image of an transparent original and a program for achieving control for the image reading apparatus by a computer. <P>SOLUTION: The apparatus is provided with an illuminating means for illuminating the transparent original with illumination light corresponding to each of a plurality of predetermined color decomposition components, an image generating means for generating image data corresponding to each of the color decomposition components on the basis of transmitted light of the transparent original obtained at every color decomposition component by the illumination of the illumination light, and a correcting means for applying correction corresponding to a leakage component to the image data which are increased in a concentration level compared to an original state due to the leakage component equivalent to the excess spectrum of the corresponding illuminating light among the image data. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus that optically reads an image of a transparent original, and a program that realizes control of the image reading apparatus by a computer.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, some image reading apparatuses use LEDs that emit red, green, and blue light, respectively, and read a color image of a transparent original in three colors (see, for example, Patent Document 1). . Until now, LEDs used in such image reading apparatuses have mainly been ternary LEDs made of ternary materials.
[0003]
In recent years, quaternary LEDs have been developed that have less drift than ternary LEDs and are superior in wavelength type and quantity of light, and have come to be used as display devices. Use in equipment is expected.
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-223861
[Problems to be solved by the invention]
However, the quaternary LED for red light emission has a secondary peak wavelength (for example, around 880 nm) in the infrared light region in addition to the red color separation wavelength (for example, around 630 nm) which is the original peak wavelength. Have Therefore, when the ternary LED for red light emission of the image reading device is simply changed to the quaternary LED, the secondary peak wavelength of the quaternary LED acts as an extra spectrum (leakage component). Therefore, the density level of the red image data is increased from the original density level of the transparent original. As a result, the linearity in the red reproduction characteristics is impaired, such as the occurrence of red floating in the dark part of the image, and the color balance of the read image is lost.
[0005]
Therefore, it is difficult to use the light of the quaternary LED as the illumination light of the image reading device unless the adverse effect due to such an extra spectrum (leakage component) is eliminated.
In addition, although the secondary peak wavelength of the quaternary LED can be removed by an optical filter to eliminate the above-described adverse effects, such a method may complicate the configuration of the hard wafer, Difficult to adapt to various types of film.
[0006]
Therefore, an object of the present invention is to provide an image reading apparatus that can easily obtain a high-precision image even when an extra spectrum is generated in illumination light. Another object of the present invention is to provide a program that can easily obtain a highly accurate image even when an extra spectrum is generated in the illumination light of the image reading apparatus.
[0007]
[Means for Solving the Problems]
The image reading apparatus according to claim 1, wherein an illumination unit that irradiates a transparent original with illumination light corresponding to each of a plurality of predetermined color separation components, and the color separation component by irradiation of the illumination light. Image generation means for generating image data corresponding to each of the color separation components based on the transmitted light of the transparent original obtained every time, and leakage corresponding to an extra spectrum of the corresponding illumination light in the image data The image processing apparatus includes a correction unit that corrects the image data whose density level increases more than the original component depending on the leakage component.
[0008]
According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the correction means realizes the correction using a correction value that can be changed according to the type of the transparent original. It is characterized by.
The image reading apparatus according to claim 3 is the image reading apparatus according to claim 1, wherein the illuminating unit emits illumination light having substantially the same wavelength range as the leakage component independently of the illumination light. The correction means realizes the correction by using a correction value that can be changed in accordance with information obtained by irradiation of illumination light having substantially the same wavelength range as the leakage component.
[0009]
The image reading apparatus according to claim 4 is the image reading apparatus according to claim 1, wherein the correction unit uses a correction value that can be changed according to a difference in gradation of the image data to be corrected. Thus, the correction is realized.
The image reading device according to claim 5 is the image reading device according to claim 1, wherein the correction unit subtracts a fixed correction value corresponding to the leakage component from the image data to be corrected. Thus, the correction is realized.
[0010]
An image reading apparatus according to a sixth aspect is the image reading apparatus according to any one of the second to fifth aspects, wherein the correction means is for illumination light that increases a density level due to the leakage component. The correction value is determined based on a ratio between the main spectral power and the extra spectral power.
According to a seventh aspect of the present invention, there is provided a program for irradiating a transparent original with illumination light corresponding to each of a plurality of predetermined color separation components, and for each color separation component by irradiation of the illumination light. A program that implements control over an image reading apparatus provided with an image generation unit that generates image data corresponding to each of the color separation components based on the transmitted light of the obtained transparent document, the image data A correction procedure for performing correction according to the leakage component on image data generated based on a density level that increases more than the original due to the leakage component corresponding to the extra spectrum of the corresponding illumination light. It is characterized by that.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
However, in the following description, an image reading apparatus having a film scanner for reading a color image of a film original and a host computer will be described as an example of the image reading apparatus of the present invention. The CPU in the film scanner is recorded in advance in a state where the program of the present invention can be executed.
[0012]
FIG. 1 is a configuration diagram of an image reading apparatus according to the present embodiment.
In FIG. 1, the image reading apparatus 1 includes a film scanner 10, a host computer 30, and a monitor 50, and an operation unit 70 such as a keyboard and a mouse. The monitor 50 and the operation unit 70 are the host computer 30. It is connected to the.
[0013]
The film scanner 10 includes a CPU 11, an LED driver circuit 12, a motor driver circuit 13, an LUT circuit 14, and an interface circuit 15, which are connected to each other via a bus. In particular, the output of the LUT (Look Up Table) circuit 14 is connected to the interface circuit 15, and the interface circuit 15 is connected to the host computer 30.
[0014]
Further, the film scanner 10 includes an LED block 16, a mirror 17, a condenser lens 18, a motor 19, a stage (not shown) for conveying the film original 20, a projection lens 21, a CCD 22, a signal processing circuit 23, and an A / D conversion. The output of the LED driver circuit 12 is connected to the LED block 16, the output of the CCD 22 is connected to the signal processing circuit 23, and the output of the signal processing circuit 23 is connected to the A / D converter 24. The output of the A / D converter is connected to the LUT circuit 14.
[0015]
The LED block 16 is a quaternary LED for red light emission (LED having a secondary peak wavelength in the infrared light region in addition to the red color separation wavelength), green light emission, blue light emission, infrared light. A plurality of quaternary LEDs for light emission are provided. The lighting timing of each LED in the LED block 16 is controlled by a drive signal supplied from the LED driver circuit 12 according to a command from the CPU 11.
[0016]
That is, the LED block 16 has three colors of red, green, and blue illumination light (however, the red illumination light has a secondary peak wavelength in the infrared light range) according to control by the CPU 11 and the LED driver circuit 12. And illumination light in the infrared light region (illumination light in a wavelength region substantially the same as the secondary peak wavelength included in the red illumination light).
Illumination light emitted from the LED block 16 is reflected by the mirror 17 and guided to the condenser lens 18, condensed by the condenser lens 18, and guided to the one line width region of the film document 20.
[0017]
The motor 19 moves a stage (not shown) for transporting the film document 20 (for example, movement to a through position described later or the film document 20 by a drive signal supplied from the motor driver circuit 13 in response to a command from the CPU 11. (Movement in the sub-scanning direction at the time of reading).
The projection lens 21 guides the transmitted light of the film original 20 with respect to each illumination light to the CCD 22 to form an image.
[0018]
The CCD 22 performs photoelectric conversion by light receiving portions of a plurality of pixels arranged in a row inside, and generates a signal charge corresponding to the transmitted light of the film document 20 guided by the projection lens 21. Then, an image signal obtained by scanning the signal charge is generated, and the image signal is supplied to the signal processing circuit 23.
The signal processing circuit 23 performs correlated double sampling processing, gain adjustment processing, and the like on the image signal supplied from the CCD 22 and supplies the image signal to the A / D converter 24.
[0019]
The A / D converter 24 A / D converts the image signal supplied from the signal processing circuit 23 and supplies it to the CPU 11 and the LUT circuit 14 as image data.
However, in this embodiment, in order to simplify the description, image data obtained by illumination light in the infrared light region is supplied only to the CPU 11. Hereinafter, image data obtained by illumination light in the infrared light region and illumination light of three colors of red, green, and blue will be referred to as Ir image data, R image data, G image data, and B image data, respectively.
[0020]
In the LUT circuit 14, an LUT for realizing gradation conversion for R image data, G image data, and B image data is set by the CPU 11 as described later. The LUT circuit 14 performs tone conversion on the image data of each color obtained at the time of the main scan by using such an LUT, and supplies the image data after the tone conversion to the interface circuit 15.
[0021]
The interface circuit 15 supplies the image data supplied from the LUT circuit 14 to the host computer 30 in response to a command from the CPU 11.
The host computer 30 performs image processing for display on the image data supplied via the interface circuit 15 and displays it on the monitor 50.
By the way, as described above, the red illumination light in the present embodiment includes a secondary peak wavelength in the infrared light region in addition to the red color separation wavelength. In general, in the film original 20, a difference in transmittance of illumination light of each color with respect to each of cyan, magenta, and yellow pigments appears as a difference in color. When the transmittance of the cyan dye with respect to the wavelength is different, the secondary peak wavelength acts as an extra spectrum (leakage component), so that the density level of the R image data is increased from the original density level of the film original 20. Resulting in. As a result, the linearity in red reproduction characteristics is impaired, for example, red floating occurs in a dark portion of an image.
[0022]
In the present embodiment, an example is shown in which, when the LUT circuit 14 performs gradation conversion on R image data, the above-described increase in density level due to an extra spectrum is corrected.
Here, in order to simplify the following description, the transmittance of the cyan dye according to the wavelength of red illumination light for any four colors will be described for each type of film document 20. However, here, a black and white film, a normal reversal film, and a special reversal film will be described as examples.
[0023]
As shown in FIG. 2A, when the film original 20 is a black and white film, the transmittance of the cyan dye with respect to the red color separation wavelength and the transmittance of the cyan dye with respect to the secondary peak wavelength are all the colors. Almost matches.
Further, as shown in FIG. 2 (2), when the film original 20 is a normal reversal film, the transmittance of the cyan dye with respect to the secondary peak wavelength is always a constant high value (for example, (Near 100%).
[0024]
Further, as shown in FIG. 2C, when the film original 20 is a special reversal film, the transmittance of the cyan dye with respect to the secondary peak wavelength is the cyan dye with respect to the red color separation wavelength for all colors. The value is higher than the transmittance.
Therefore, when the film original 20 is a black and white film, the density level does not increase due to the above-described extra spectrum. Therefore, the LUT circuit 14 may perform normal gradation conversion without correction, and the CPU 11 may set the data for gradation conversion without correction as an LUT in the LUT circuit 14.
[0025]
Further, when the film original 20 is a normal reversal film, the increase amount of the density level due to the above-described extra spectrum shows a constant value regardless of the gradation as shown in FIGS. 3 (1)-(a). become. For this reason, the LUT circuit 14 only needs to perform correction by subtracting a constant value from the R image data together with normal gradation conversion, and therefore the CPU 11 is data having a shape as shown in FIGS. Is set in the LUT circuit 14 as an LUT.
[0026]
Further, when the film document 20 is a special reversal film, the amount of increase in density level due to the above-described extra spectrum changes according to the gradation as shown in FIGS. For this reason, the LUT circuit 14 may perform correction for subtracting a value that changes according to the gradation of the R image data from the R image data together with normal gradation conversion. Data indicating the shape as in b) may be set in the LUT circuit 14 as an LUT.
[0027]
When the film original 20 is a normal reversal film or a special reversal film, values to be subtracted from the R image data (hereinafter referred to as “correction values”) are the main spectrum power and the extra spectrum in the red illumination light. It is possible to make a determination based on the ratio to the power, and according to the gradation conversion reflecting the correction value determined in this way, linearity in the red reproduction characteristic can be realized.
[0028]
In the present embodiment, the ratio of the main spectrum power to the extra spectrum power in the final red illumination light is obtained in consideration of the spectrum power that varies depending on the condenser lens 18, the projection lens 21, and the CCD 22, and based on the ratio. Thus, the correction value is determined for each type of film document 20. The data (hereinafter referred to as “LUT data”) set in the LUT in order to realize the gradation conversion reflecting the correction value determined in this way by the LUT circuit 14 is classified according to the type of the film document 20. Suppose that it is stored in the host computer 30 in advance.
[0029]
The ratio between the main spectral power and the extra spectral power in the red illumination light is slightly different for each quaternary LED for red light emission. In addition, it is desirable to store a value for adjusting the individual difference calculated in advance for each quaternary LED for red light emission.
[0030]
Further, in the host computer 30, not only LUT data for performing gradation conversion reflecting the correction value for R image data, but also normal gradation conversion for image data of other colors. It is assumed that LUT data to be stored is stored in advance for each type of film document 20. Further, in the host computer 30, when the film original 20 is a black and white film, LUT data for performing normal gradation conversion on the image data of three colors of red, green and blue is also stored in advance. I will be there.
[0031]
4 and 5 are operation flowcharts of the image reading apparatus 1 in the present embodiment.
Hereinafter, the operation of the image reading apparatus 1 of the present embodiment will be described with reference to FIGS. 4 and 5.
First, when a main power supply (not shown) is turned on, the CPU 11 performs a predetermined initialization process so that the illumination light emitted from the LED block 16 is guided to a transparent position without the film document 20. A stage (not shown) is moved through the circuit 13 and the motor 19 (S1 in FIG. 4).
[0032]
Then, the CPU 11 calculates the white balance exposure amount and shading correction data for each color of red, green, and blue based on the data obtained from the transmitted light from the transparent position (S2 in FIG. 4).
Note that the white balance exposure amount is data used when determining the optimum exposure amount for each of the three illumination lights of red, green, and blue, and such white balance exposure amount and shading correction data are calculated. Since it can be performed in the same manner as an existing image reading apparatus, detailed description is omitted here.
[0033]
Next, the CPU 11 controls each part in the film scanner 10 and performs reading with illumination light of three colors of red, green, and blue based on the prescan resolution (for example, 300 dpi) and the exposure amount. In accordance with the image data of each color obtained by such reading and the above-described white balance exposure amount, an optimum exposure amount is determined for each illumination light of each color (S3 in FIG. 4).
[0034]
Then, the CPU 11 controls each part in the film scanner 10 and performs reading with illumination light of three colors of red, green, and blue based on the prescan resolution and the optimum exposure amount determined as described above. Then, the image data of each color is acquired (S4 in FIG. 4).
Further, the CPU 11 controls each part in the film scanner 10 and performs reading with illumination light in the infrared region based on the resolution and exposure amount for pre-scanning to obtain Ir image data (S5 in FIG. 4). .
[0035]
Next, the CPU 11 calculates the standard deviation σIr of the histogram of Ir image data and the standard deviation σR of the histogram of R image data (S6 in FIG. 4).
Here, the relationship between these standard deviations and the type of film document 20 will be described. However, here, a black and white film, a normal reversal film, and a special reversal film will be described as examples.
[0036]
As described above, the illumination light in the infrared light region is illumination light in a wavelength region that is substantially the same as the secondary peak wavelength included in the red illumination light.
Therefore, when the film original 20 is a black and white film, the transmittance of the cyan dye with respect to the illumination light in the infrared light region is the red color separation wavelength as in the transmittance with respect to the secondary peak wavelength in FIG. It almost coincides with the transmittance for. Therefore, the histogram of Ir image data shows the same shape as the histogram of R image data. Therefore, when the histogram of the R image data shows a shape as shown in FIG. 6A, the shape of the histogram of the Ir image data becomes as shown in FIG. 6B.
[0037]
Further, when the film original 20 is a normal reversal film, the transmittance of the cyan dye for the illumination light in the infrared light region is always constant, similar to the transmittance for the secondary peak wavelength in FIG. High value. Accordingly, the gradation frequency of Ir image data is concentrated in the vicinity of the maximum gradation. Therefore, when the histogram of the R image data shows a shape as shown in FIG. 6A, the histogram of the Ir image data becomes as shown in FIG. 6C.
[0038]
Further, when the film original 20 is a special reversal film, the transmittance of the cyan dye with respect to the illumination light in the infrared light region is similar to the transmittance with respect to the secondary peak wavelength in FIG. The value is higher than the transmittance with respect to the decomposition wavelength. Therefore, the gradation frequency of the Ir image data is dispersed in a certain range at a gradation higher than that of the R image data. Therefore, when the histogram of R image data shows a shape as shown in FIG. 6A, the histogram of Ir image data becomes as shown in FIG. 6D.
[0039]
Therefore, when the standard deviation σIr of the histogram of Ir image data and the standard deviation σR of the histogram of R image data satisfy the following condition 1, it can be determined that the film document 20 is a black and white film.
σIr / σR> K0 (where K0 is a value of about 1)... Condition 1
If the standard deviation σIr of the histogram of Ir image data and the standard deviation σR of the histogram of R image data do not satisfy both the condition 1 and the following condition 2, the film document 20 is determined to be a normal reversal film. it can.
[0040]
σIr / σR> K (where K is a value of about 0.2 to 0.3) Condition 2
Further, when the standard deviation σIr of the histogram of Ir image data and the standard deviation σR of the histogram of R image data do not satisfy the condition 1 but satisfy the condition 2, it can be determined that the film document 20 is a special reversal film.
[0041]
Therefore, in this embodiment, the type of film document is determined based on these conditions.
That is, when calculating the standard deviation σIr of the histogram of Ir image data and the standard deviation σR of the histogram of R image data as described above, the CPU 11 determines whether or not the condition 1 described above is satisfied (S7 in FIG. 5). If the condition 1 is not satisfied, the CPU 11 determines whether the condition 2 is satisfied (S8 in FIG. 5).
[0042]
Then, as a result of these determinations, if the film document 20 is a black and white film (YES side in FIG. 5 S7), the CPU 11 performs LUT data corresponding to the black and white film stored in advance in the host computer 30 as described above. Is obtained via the interface circuit 15 and set in the LUT in the LUT circuit 14 (S9 in FIG. 5).
[0043]
Further, when the film document 20 is a normal reversal film (NO side in FIG. 5 S8), the CPU 11 stores the LUT data corresponding to the normal reversal film stored in advance in the host computer 30 as described above. Obtained via the interface circuit 15 and set in the LUT in the LUT circuit 14 (S10 in FIG. 5).
[0044]
Further, when the film document 20 is a special reversal film (YES side in FIG. 5 S8), the CPU 11 stores the LUT data corresponding to the special reversal film stored in advance in the host computer 30 as described above. Obtained via the interface circuit 15 and set in the LUT in the LUT circuit 14 (S11 in FIG. 5).
[0045]
Next, the CPU 11 controls each part in the film scanner 10 to read with illumination light of three colors of red, green, and blue based on the resolution for the main scan and the optimum exposure amount determined as described above. This is performed (S12 in FIG. 5).
[0046]
Then, the CPU 11 performs gradation conversion by the LUT set as described above on the image data of each color obtained by such reading through the LUT circuit 14 (S13 in FIG. 5).
Finally, the CPU 11 supplies the image data of each color after gradation conversion to the host computer 30 via the interface circuit 15 (S14 in FIG. 5).
[0047]
As described above, in the present embodiment, according to the type of the film document 20, the CPU 11 increases the density level due to the extra spectrum simultaneously with the gradation conversion by the LUT data set in the LUT in the LUT circuit 14. Can be corrected.
Therefore, according to the present embodiment, even when a quaternary LED is used as the light source of the image reading apparatus, the linearity in the red reproduction characteristic can be maintained by software, and the configuration of the hard wafer is complicated. A high-accuracy image can be easily obtained without conversion. In addition, the characteristics of the quaternary LED superior to the ternary LED (such as less drift and a large number of wavelengths and a large amount of light) can be utilized.
[0048]
In this embodiment, the CPU 11 sets the LUT data stored in the host computer 30 in the LUT in the LUT circuit 14, thereby correcting the increase in density level due to the extra spectrum simultaneously with the gradation conversion. For example, the above-described correction value is stored in the host computer 30 and the CPU 11 performs a process of subtracting the correction value from the R image data, thereby separately from the gradation conversion in the LUT circuit 14. Correction of an increase in density level due to an extra spectrum may be realized.
[0049]
Further, in the present embodiment, an example has been shown in which an increase in density level caused by the secondary peak wavelength in the infrared light region existing in the quaternary LED for red light emission acting as an extra spectrum is corrected. However, even when a light source having a secondary peak wavelength in the light region not related to the color reproduction of the film original 20 in addition to the original peak wavelength is used, the density level is the same as in the present embodiment. Can be compensated for.
[0050]
【The invention's effect】
As described above, according to the present invention, a high-accuracy image can be easily obtained even when an extra spectrum is generated in the illumination light. Therefore, for example, a light source that has superior performance as compared with a conventional light source but cannot be used for an image reading apparatus due to generation of an extra spectrum can be used for an image reading apparatus.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an image reading apparatus.
FIG. 2 is a diagram illustrating an example of a change in the transmittance of a cyan dye according to the wavelength of red illumination light.
FIG. 3 is a diagram for explaining a correction method;
FIG. 4 is an operation flowchart of the image reading apparatus.
FIG. 5 is an operation flowchart of the image reading apparatus.
FIG. 6 is a diagram for explaining a difference in histogram between R image data and Ir image data.
[Explanation of symbols]
1 Image Reading Device 10 Film Scanner 11 CPU
12 LED driver circuit 13 Motor driver circuit 14 LUT circuit 15 Interface circuit 16 LED block 17 Mirror 18 Condenser lens 19 Motor 20 Film document 21 Projection lens 22 CCD
23 Signal Processing Circuit 24 A / D Converter 30 Host Computer 50 Monitor 70 Operation Unit

Claims (7)

Illuminating means for irradiating a transparent original with illumination light corresponding to each of a plurality of predetermined color separation components;
Image generating means for generating image data corresponding to each of the color separation components based on the transmitted light of the transmission original obtained for each of the color separation components by irradiation of the illumination light;
Correction means for performing correction according to the leakage component on the image data in which the density level is increased due to the leakage component corresponding to the extra spectrum of the corresponding illumination light in the image data. An image reading apparatus. The image reading apparatus according to claim 1,
The correction means includes
An image reading apparatus that realizes the correction using a correction value that can be changed according to the type of the transparent original. The image reading apparatus according to claim 1,
The illumination means includes
Independently of the illumination light, illuminate the transmissive original with illumination light in a wavelength region substantially the same as the leakage component,
The correction means includes
An image reading apparatus that realizes the correction by using a correction value that can be changed according to information obtained by irradiation of illumination light in a wavelength region substantially the same as the leakage component. The image reading apparatus according to claim 1,
The correction means includes
An image reading apparatus that realizes the correction using a correction value that can be changed according to a difference in gradation of image data to be corrected. The image reading apparatus according to claim 1,
The correction means includes
An image reading apparatus that realizes the correction by subtracting a fixed correction value corresponding to the leakage component from the image data to be corrected. The image reading apparatus according to any one of claims 2 to 5,
The correction means includes
An image reading apparatus, wherein the correction value is determined based on a ratio between a main spectral power and an extra spectral power in illumination light that increases a density level due to the leakage component. Illuminating means for irradiating illumination light corresponding to each of a plurality of predetermined color separation components with respect to the transmission original, and transmission light of the transmission original obtained for each color separation component by irradiation of the illumination light A program for realizing, on a computer, control over an image reading apparatus comprising image generation means for generating image data corresponding to each of the color separation components,
Among the image data, correction for performing correction according to the leakage component on the image data generated based on the density level that is increased more than the original due to the leakage component corresponding to the extra spectrum of the corresponding illumination light A program characterized by having a procedure.

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