JP2009135917A - Optical device, image reading device, and filter fabricating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the quality of a read image by suppressing output change of a light-receiving element caused by variations in optical wavelength of a light-emitting element. <P>SOLUTION: In an image sensor 1, a filter having a light transmitting region in a narrower optical wavelength range than the optical wavelength range of spectral characteristics of each LED is arranged in an optical path where light emitted by shifting the light-emitting timings of plural LEDs of different optical wavelength ranges of a light source 3 is projected and reflected on an original and then made incident on a CCD array 6 of a light-receiving section 5. Accordingly, even if the optical wavelength ranges of the spectral characteristics of the LEDs vary and an inclination exists in the reflection characteristics of the original, those influences can be absorbed by the optical transparency of the narrow optical wavelength range of the filter, and output of the CCD array 6 can be made stable. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical device and an image reading device, and more specifically, an optical device that uses reflected or transmitted light of light emitted from a light emitting element to an irradiation object, and an image that reads an image of a document as the irradiation object. The present invention relates to a reader and a filter manufacturing method.

  Image reading devices used for color facsimiles, color scanners, color copiers, color composite devices, etc. generally emit light of RGB (red, green, blue) light wavelengths in a color document of a preset size. An optical unit including the element is provided, the light emission timings of the RGB light emitting elements of the optical unit are switched to emit light and the original is irradiated with reading light, and the reflected light reflected by the original is reflected by the reading light. An image is formed on the light receiving element of the optical unit, and an image of the document is output as an electric signal from the light receiving element of the optical unit.

  Generally, an LED (Light Emitting Diode) element is widely used as a light emitting element of an optical unit of the color image reading apparatus (see Patent Document 1).

  However, LED elements generally have variations in the light wavelength range in spectral characteristics due to variations in manufacturing, and when a document image is read using an LED having such a variation in the light wavelength range. Since distortion occurs in image characteristics, various image processing has been conventionally performed on read image data (see Patent Document 2).

JP 2004-144859 A JP 2005-33834 A

  However, in the prior art, variations in manufacturing of LEDs are taken into consideration, but issues that affect the accuracy of other optical systems are not taken into account, such as image reading accuracy. In order to improve the accuracy of use of light reflected on the object to be irradiated, there is a need for improvement.

  That is, even if the same type of LED has a variation in light wavelength, the range of variation in the light wavelength of the LED overlaps with the spectral characteristic of the document even when using a document with an irradiation object having the same spectral characteristic of the color of the document. As a result, the electrical signal level (that is, the output of the image sensor) obtained by photoelectric conversion of the reflected light and transmitted light from the document changes, and the image quality of the read image deteriorates.

  The present invention has been made in view of the above, and an optical device and an image reading device capable of improving the image quality of a read image by suppressing a change in output of the light receiving device due to variations in light wavelength of the light emitting device. An object is to provide an apparatus and a filter manufacturing method.

  In order to solve the above-described problems and achieve the object, an optical apparatus according to the present invention includes a light emitting element having spectral characteristics in a predetermined light wavelength range, and causes the light emitting element to emit light to emit light to an irradiation object. A light source unit that emits light, a light receiving element having sensitivity in a light wavelength range of the light emitting element, a light receiving unit that receives reflected light or transmitted light from the irradiation object by the light receiving element, and performs photoelectric conversion; A range of variation in the light wavelength region of the light emitting element that is disposed on the optical path from the light emitting element through the irradiation object to the light receiving element, narrower than the light wavelength range of the spectral characteristics of the light emitting element. And a filter having a light transmission region including

  In addition, an image reading apparatus according to the present invention includes an optical device that irradiates a document with reading light and photoelectrically converts light reflected or transmitted by the document, and an image of the document is output by an electrical signal output from the optical device. The optical device has a light emitting element having spectral characteristics in a predetermined light wavelength range, emits light from the light emitting element and emits light to an irradiation object, and A light-receiving element having sensitivity in the light wavelength range of the light-emitting element, and receiving and photoelectrically converting reflected light or transmitted light from the irradiation object by the light-receiving element; and from the light-emitting element to the irradiation object And a filter that is disposed on an optical path from the light emitting element to the light receiving element, is narrower than the light wavelength range of the spectral characteristics of the light emitting element, and includes a range of variations in the light wavelength range of the light emitting element. thing And features.

  The filter manufacturing method according to the present invention includes a first measurement step of measuring spectral characteristics of a plurality of light emitting elements of the same type having spectral characteristics in a predetermined light wavelength range, and light from each of the plurality of light emitting elements. A second measuring step of measuring the output characteristics of the light receiving element that receives the reflected light, and the measured spectral characteristics of the plurality of light emitting elements, A third measurement step for obtaining variations in the light wavelength region of the light emitting element based on the output characteristics of the light receiving element; and a light wavelength region of the light emitting element that is narrower than the light wavelength region of the spectral characteristic of the light emitting element. And a manufacturing step of manufacturing a filter having the determined light transmission region.

  The present invention is such that the light emitted from the light emitting element is irradiated on the irradiation object, reflected or transmitted, and is narrower than the light wavelength range of the spectral characteristics of the light emitting element on the light path until it enters the light receiving element. In addition, since a filter having a light transmission region including a variation range of the light wavelength region of the light emitting element is disposed, when light from the light emitting element is irradiated onto an irradiation object having the same spectral characteristics, The conversion of the electrical signal due to the variation in the light wavelength can be absorbed by the light transmission characteristic of the filter in the light wavelength range narrower than the light wavelength range of the spectral characteristic of the light emitting element, and the light reception caused by the variation in the light wavelength of the light emitting element There is an effect that the output quality of the read image can be improved by suppressing the output change of the element.

  Exemplary embodiments of an optical apparatus and an image reading apparatus according to the present invention are explained in detail below with reference to the accompanying drawings. The embodiments described below are preferred embodiments of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. As long as there is no description which limits, it is not restricted to these aspects.

  1 to 24 are diagrams showing an embodiment of an optical apparatus and an image reading apparatus according to the present invention. FIG. 1 is an image sensor to which an embodiment of the optical apparatus and the image reading apparatus according to the present invention is applied. 1 is an exploded perspective view of FIG.

  In FIG. 1, an image sensor 1 includes a light source unit 3, a lens 4, and a light receiving unit 5 housed in an optical housing 2 as shown in FIG. 2, and an upper opening surface of the optical housing 2 is formed by a contact glass 7. It is blocked. The light receiving unit 5 is provided with a CCD (Charge Coupled Device) array 6 as a light receiving element. On the outer surface of the contact glass 7, a document Gp, which is an object to be irradiated, is arranged in a state of being close to the contact glass 7, and the image sensor 1 irradiates the document Gp with light and an electric signal corresponding to the amount of reflected light. Is output.

  The light source unit 3 uses an LED (Light Emitting Diode) element as its light emitting element. As shown in FIG. 3, the light source unit 3 uses a red LED, a green LED, a yellow LED, and three primary colors. Either a multi-chip method (see FIG. 3A), a blue LED and a yellow phosphor (see FIG. 3B), or a single-chip method using an ultraviolet LED and an RGB phosphor (see FIG. 3C) It may be a method.

  As shown in FIGS. 4A and 4B, the light source unit 3 includes an LED unit 3a and a light guide 3b, and transmits light emitted from the LED unit 3a to the light guide 3b. May be of a type in which light is evenly guided in the length direction (document width direction: main scanning direction) to irradiate the document Gp, as shown in FIG. 5 (a) or FIG. 5 (b). The LED array 3c may be provided in the document width direction without the light guide. In the LED array 3c, a plurality of LEDs as light emitting elements are arranged in a row in the document width direction. FIG. 5A shows the case of a two-light configuration, and FIG. 5B shows the case of a one-light configuration.

  As the lens 4, a lens using the SELFOC lens array 4a shown in FIGS. 6A and 6B, the roof mirror lens array 4b and the lens array 4c shown in FIGS. 7A and 7B, respectively. Further, the one using the separation mirror 4d, the one using the plate lens array 4e shown in FIGS. 8A to 8C, or the one using the telecentric lens array 4f shown in FIG. 9 may be used. .

  In the above description, as shown in FIG. 10, the image sensor 1 is a so-called equal-magnification image sensor and is a one-line sensor. However, the image sensor is not limited to a one-line sensor. Alternatively, a multiple line sensor may be used.

  Further, the image sensor 1 is not limited to the equal magnification type, and may be a reduction type optical system image sensor as shown in FIG. In the case of the reduction type optical system, for example, as shown in FIG. 11, RGB LEDs 3sr, 3sg, 3sb are used as the light source 3, and the reflected light reflected by the original Gp through the contact glass 7 is reflected by the mirror 8 to The CCD array 6 is irradiated through 9.

  When the light source unit 3 is a multi-chip type light source and has RGB LEDs 3r, 3g, and 3b as shown in FIG. 12, each of the LEDs 3r, 3g, and 3b includes a drive current Ib, Ir, and Ig. However, the drive currents Ib, Ir, and Ig are supplied at different timings as shown in FIG.

  As shown in FIG. 13, in the image sensor 1, the LEDs 3r, 3g, and 3b are sequentially driven by drive currents Ib, Ir, and Ig supplied at different timings to emit light, and the LEDs 3r are emitted at different timings. Light emitted from 3g and 3b is applied to the original Gp through the contact glass 7 as reading light, and the reflected light reflected by the original Gp is incident on the CCD array 6 of the light receiving unit 5 through the lens 4.

  The CCD array 6 outputs, as a CCD output, an electrical signal having a charge amount corresponding to the amount of reflected light reflected from the original Gp and incident.

  Such an image sensor 1 is applied to an image reading apparatus such as a facsimile apparatus, a copying apparatus, a composite apparatus, and a scanner apparatus. The output of the CCD array 6 is A / D converted by an analog front end unit (not shown). The image is input to the image input unit 21 of the image processing unit 20 shown in FIG.

  As shown in FIG. 14, the image processing unit 20 includes an image input unit 21, a shading correction unit 22, an interline interpolation unit 23, an RGBγ correction 24, an RGB / YCbCr conversion unit 25, a filter unit 26, and a YCbCr / RGB conversion unit 27. , Sub-scan scaling unit 28, main scanning scaling unit 29, error diffusion / dither unit 30, RGB input gray output unit 31, error diffusion / dither unit 32, RGB input RGB output unit 33, RGB / CMYK color space modulation unit 34, a CMYKγ correction unit 35, an error diffusion / dither unit 36, an RGB input CMYK output unit 37, and the like. An RGB image input from the image sensor 1 is output in gray, and an RGB image output line is output. And an image processing line for CMYK output.

  The image processing unit 20 inputs the RGB image data input from the image sensor 1 to the shading correction unit 22, and the shading correction unit 22 determines the distribution variation of the light amount of the light source unit 3 in the main scanning direction and the A from the CCD array 6. The variation in the image signal in the main scanning direction due to the characteristics up to the output of the / D conversion unit is corrected and output to the interline interpolation unit 23. The interline interpolating unit 23 corrects a positional shift between the lines at the same magnification existing in the RGB color signals output from the CCD array 6 of the image sensor 1 and outputs the corrected signals to the RGBγ correcting unit 24 for RGBγ correction. The unit 24 converts the RGB reflectance data into RGB density data and outputs it to the RGB / YCbCr conversion unit 25.

  The RGB / YCbCr conversion unit 25 converts the RGB image data into YCbCr image data and outputs the converted image data to the filter unit 26. The filter unit 26 performs a filtering process on the Y data, and the grayscale image data is obtained. The image data is transferred to the sub-scanning scaling unit 28, and the color image data is transferred to the YCbCr / RGB conversion unit 27.

  The YCbCr / RGB conversion unit 27 converts the YCbCr image data into RGB image data and outputs the converted image data to the sub-scanning scaling unit 28.

  The sub-scanning scaling unit 28 performs scaling processing on the image data in the sub-scanning direction, for example, in the range of 8.0% to 200.0%, and passes it to the main scanning scaling unit 29, where 29, the image data is scaled in the main scanning direction within a range of, for example, 8.0% to 200.0%, the gray scale image data is processed by the error diffusion / dither unit 30, and the RGB image data is processed. And output to the error diffusion / dither unit 32 or the RGB / CMYK color space modulation unit 34.

  The error diffusion / dither unit 30 performs gradation processing on the grayscale image data by error diffusion or dither processing, and passes it to the RGB input gray output unit 31. The RGB input gray output unit 31 performs error diffusion / dither processing. The 8-bit grayscale image data passed from the unit 30 is output.

  The error diffusion / dither unit 32 performs gradation processing on the RGB image data passed from the main scanning scaling unit 29 by error diffusion or dither processing, and passes it to the RGB input RGB output unit 33, where the RGB input RGB The output unit 33 complements the RGB image data from the error diffusion / dither unit 32 in an image memory, or outputs it to an image processing apparatus such as a computer or an image forming apparatus.

  The RGB / CMYK color space modulation unit 34 converts the RGB image data passed from the main scanning scaling unit 29 into CMYK image data and passes it to the CMYKγ correction unit 35, and the CMYKγ correction unit 35 converts the CMYK image data into CMYK image data. On the other hand, γ correction is applied to the error diffusion / dither unit 36.

  The error diffusion / dither unit 36 performs gradation processing on the CMYK image data from the CMYKγ correction unit 35 by error diffusion or dither processing, and passes it to the RGB input CMYK output unit 37. The RGB input CMYK output unit 37 The CMYK image data from the error diffusion / dither unit 32 is output to a printer or the like and used for print output by the printer or the like.

  In the image sensor 1 according to the present embodiment, as described above, the light emitted from the LED unit 3a of the light source unit 3 is applied to the original Gp through the contact glass 7, and the light reflected by the original Gp is reflected in the lens 4. Although not shown, on the optical path from the LED unit 3a to the CCD array 6, an optical wavelength region that overlaps the optical wavelength region of the spectral characteristics of the LEDs arranged in the LED unit 3a. And a filter having a light wavelength region narrower than the light wavelength region of the LED. In this filter, when the LED unit 3a is of the multi-chip system shown in FIGS. 3A and 12 and each of RGB has LEDs 3r, 3g, and 3b, the light of each LED 3r, 3g, and 3b. When the filter having the light transmission region in the wavelength region is disposed and the LED unit 3a is the single chip system shown in FIGS. 3B and 3C, the light transmission region is in the light wavelength region of one LED. A filter is provided.

  The filter may be provided on the optical path from the LED of the light source unit 3 to the document Gp, for example, in the light source unit 3, or on the optical path from the document Gp to the CCD array 6 of the light receiving unit 5, for example, the lens 4. It may be provided in front of the CCD array 6 of the portion or the light receiving unit 5. In addition, when the light source 3 is provided with the light guide 3b when the light source 3 is provided with the filter, the filter may be provided at the incident portion of the light guide 3b. If is provided, the filter area can be reduced.

  Next, the operation of the present embodiment will be described. The image sensor 1 according to the present embodiment has a wavelength region that overlaps the light wavelength region within the range of variation in spectral characteristics of the LED on the optical path from the LED unit 3a to the CCD array 6, and the spectral characteristics of the LED. By disposing a filter whose transmission region is a wavelength region narrower than the light wavelength region, the influence of the light characteristics of the original Gp that is the LED and the irradiation target is suppressed, and the usability of reflected light from the original Gp is reduced. It is improving.

  That is, the LED has variations in the light wavelength range of its spectral characteristics, for example, as shown in FIG. 15 due to variations in manufacturing. In FIG. 15, the spectral characteristics vary as shown by the spectral characteristic curves Hb and Hc with the spectral characteristic curve Ha as the center. In FIG. 15, the horizontal axis is the wavelength (nm), the vertical axis is the spectral characteristic value, and the spectral characteristic curves Ha to Hc in FIG. 15 are black correction and white correction by the shading correction unit 22 of the image processing unit 20. Is normalized with the integrated value.

  When the image sensor 1 is used to irradiate the object to be irradiated and the reflected light is used, for example, when applied to an image reading apparatus, the LED has a variation in the optical wavelength range of the spectral characteristics. In addition, as shown in FIG. 16, there is a document Gp having an inclination in reflection characteristics in a wavelength region overlapping at least the light wavelength of the spectral characteristic of the LED, as shown in FIG. In FIG. 16, the horizontal axis represents the wavelength (nm), and the vertical axis represents the reflection characteristic value of the document Gp.

  When the image sensor 1 is used to irradiate the original Gp having such a reflection characteristic with a light from an LED having a variation in the spectral characteristic shown in FIG. As shown in FIG. 17, the reflection characteristics are characteristic curves ha, hb, hc obtained by multiplying the spectral characteristics of the LED and the reflection characteristics of the original Gp.

  Then, the light emitted from the LEDs having the spectral characteristic curves Ha, Hb, and Hc in FIG. 15 is introduced into the light receiving unit 5 of the image sensor 1 by reflecting the reflected light reflected by the document Gp having the reflection characteristics in FIG. When the photoelectric conversion is performed by the CCD array 6 of the light receiving unit 5, assuming that the light receiving sensitivity of the CCD array 6 of the light receiving unit 5 has a flat characteristic, as shown in FIG. The outputs (CCD array output) Has, Hbs, Hcs of the CCD array 6 corresponding to the light of Hb, Hc are proportional to the values obtained by integrating the characteristic curves ha, hb, hc of the LED of FIG. The CCD array outputs Has, Hbs, and Hcs in FIG. 18 are obtained by setting the integrated values of the LED characteristic curves ha, hb, and hc to “1” and setting the integrated value Has of the characteristic curve ha to “1”. Are integrated values Hbs and Hcs.

  That is, if the light emission wavelength of the LED array 3c of the light source unit 3 is shifted, the output level of the CCD array 6 of the light receiving unit 5 changes even when the LED array 3c of the same color is driven, and the document Gp The scanned image gets worse. That is, there is a problem that the usability of the image sensor 1 is poor.

  As described above, such a problem is caused by the variation in the light wavelength range of the spectral characteristic of the LED and the inclination of the reflection characteristic of the original Gp. In particular, there is no variation in the light wavelength range of the spectral characteristic of the LED itself. Does not occur. However, commercially available LEDs are classified into ranks, and LEDs with small variations have high ranks, and the higher the selection conditions for LEDs used in the image sensor 1, the higher the ranks. However, the higher the rank of the LED, the higher the cost. When incorporating LEDs of a plurality of colors into the LED unit 3a of the light source unit 3 of the image sensor 1, all the LEDs for the number of colors have the same rank. It is necessary to use something. As a result, when the number of colors of the LED increases, the image sensor 1 increases in cost to the power of the number of colors and becomes expensive.

  Therefore, the image sensor 1 of the present embodiment has an optical wavelength region that overlaps the range of variation in the optical wavelength region of the spectral characteristics of the LED on the optical path from the LED unit 3 a of the light source unit 3 to the CCD array 6 of the light receiving unit 5. In addition, a filter having a light transmission region in a light wavelength region narrower than the variation range of the light wavelength region of the spectral characteristics of the LED is disposed. For example, when the LED of the LED unit 3 has variations in its spectral characteristics in the light wavelength region centered around 520 nm as shown in FIG. 15, as shown in FIG. A filter having a light transmission region in a light wavelength region of 500 nm to 550 nm is used.

  If the LEDs of the LED unit 3a have variations as shown in FIG. 15 in their spectral characteristics, a filter having a light transmission region in the light wavelength band shown in FIG. When it is provided on the optical path from 3 to the irradiation of the original Gp, the spectral / transmission characteristics when passing through the filter with each variation in the spectral characteristics of the LED are as shown in FIG. Spectral / transmission characteristic curves haf, hbf, hcf obtained by multiplying the characteristic values (characteristic curves) ha, hb, hc and the transmission characteristic values of the filter (in FIG. 19, the transmission characteristic value is “1”). .

  Assuming that the shading correction unit 22 of the image processing unit 20 performs black correction and white correction on the output of the CCD array 6 of the light receiving unit 5 by the light of the spectral / transmission characteristic curves haf, hbf, hcf. A spectral / transmission / monochrome characteristic curve hafs, hbfs, hcfs as shown in FIG.

  The spectral / transmission / black and white characteristic curves hafs, hbfs, and hcfs having such spectral / transmission characteristic curves haf, hbf, and hcf in consideration of black and white correction are inclined to the reflection characteristics shown in FIG. When the original Gp is irradiated, reflected by the original Gp, incident on the CCD array 6 of the light receiving unit 5, and the shading correction unit 22 of the image processing unit 20 performs black correction and white correction. As shown in FIG. 22, the characteristic values (spectral / transmission / monochrome correction / reflection characteristic values) of light input to the CCD array 6 of the light receiving unit 5 include the spectral characteristic value of the LED, the light transmission characteristic value of the filter, and Spectral / transmission / monochrome correction / reflection characteristic curves hafsg, hbfsg, hcfsg multiplied by the reflection characteristic value of the original Gp.

  Therefore, the output (CCD array output) Hass, Hbss, Hcss of the CCD array 6 of the light receiving unit 5 is obtained by converting spectral / transmission / monochrome correction characteristic curves hafs, hbfs, hcfs of each LED of FIG. 22 as shown in FIG. Even if there is a variation in the spectral characteristics of the LEDs as compared with FIG. 15, fluctuations in the output Hass, Hbss, and Hcss of the CCD array 6 can be suppressed compared to FIG. FIG. 23 shows other characteristic curves with the integral values of the spectral / transmission / monochrome correction / reflection characteristic curves hafs, hbfs, and hcfs of each LED being “1”. This is the normalized integral value of hbfs and hcfs.

  In the above description, the irradiation object is a positive document Gp, and the light from the LED is reflected by the document Gp. However, the irradiation object is not limited to the positive document Gp. For example, a negative document such as a negative film may be used. In the case of such an original such as a negative film, the light receiving unit 5 is disposed at a position facing the light source unit 3, and light from the light source unit 3 is transmitted through the object to be irradiated with the negative so that the negative The light transmitted through the irradiation object is received by the CCD array 6 of the light receiving unit 5, and the film is disposed on the optical path from the LED of the light source unit 3 to the CCD array 6 of the light receiving unit 5.

  As described above, in the image sensor 1 according to the present embodiment, the light emitted from the LED of the light source unit 3 is applied to the irradiation object, reflected or transmitted, and incident on the CCD array 6 of the light receiving unit 5. A filter having a light transmission region of a light wavelength region narrower than the light wavelength region in the light wavelength region of the spectral characteristics of the LED is disposed on the optical path.

  Therefore, even if there are variations in the light wavelength range of the spectral characteristics of the LED and the reflection characteristics and transmission characteristics of the irradiation object are inclined, the influence of the variations in the light wavelength range and the reflection characteristics and transmission characteristics The light can be absorbed by the light transmission characteristics of the filter in the light wavelength range narrower than the light wavelength range of the spectral characteristics of the LED, and the usability of the output from the CCD array 6 can be improved.

  When the LED unit 3a of the light source unit 3 is a multi-chip type and has a plurality of LEDs 3r, 3g, and 3b, the filter has a multi-band pass filter or a light transmission characteristic as shown in FIG. A triple band pass filter can be used. For example, when the LED unit 3a includes three LEDs 3r, 3g, and 3b, the light transmission in a light wavelength region narrower than the light wavelength region in the light wavelength region of the spectral characteristics of each LED 3r, 3g, and 3b. A triple band pass filter having a region is used.

  Further, when a dielectric layer film filter is used as the filter, the dielectric layer film filter reflects light having a wavelength that does not pass through. Therefore, particularly when the filter is formed on the lens or the light receiving unit 5, stray light is used. In order to prevent the influence on flare and flare, a reflected light absorption process such as dispersing an absorbing material that absorbs reflected light is performed.

  In the above-described embodiment, the description has been given of the case where the LED has the dispersion in the light wavelength region of the spectral characteristic and the original Gp that is the irradiation target has the inclination in the reflection characteristic in the wavelength region where the light wavelength of the spectral characteristic of the LED overlaps.

  Further, in addition to the above, even with the same type of LED, there is a variation in the light wavelength. Therefore, even when using a document with an irradiation target having the same spectral characteristic of the color of the document, the range of variation in the light wavelength of the LED and the document Spectral characteristics overlap, and the electric signal level obtained by photoelectrically converting reflected light or transmitted light from the document changes. FIG. 25 is a graph showing spectral characteristics of a cyan document with respect to wavelength. In FIG. 25, the horizontal axis represents the wavelength (nm), and the vertical axis represents the spectral characteristic value (reflection characteristic value) of the document Gp.

  When the image sensor 1 is used to irradiate the original Gp having such spectral characteristics with light from an LED having a variation in the spectral characteristics shown in FIG. 15 of the light source unit 3, the spectral characteristics (reflection) on the surface of the original Gp. As shown in FIG. 26, the characteristic) is characteristic curves ha, hb, hc obtained by multiplying the spectral characteristic of the LED and the reflection characteristic of the original Gp. FIG. 26 is a graph showing the spectral characteristics of reflected light when a cyan original having the spectral characteristics shown in FIG. 25 is irradiated with light of green wavelength from an LED.

  Then, the light emitted from the LED having the spectral characteristic curves Ha, Hb, and Hc of FIG. 15 is introduced into the light receiving unit 5 of the image sensor 1 by reflecting the reflected light reflected by the original Gp having the spectral characteristics of FIG. When photoelectric conversion is performed by the CCD array 6 of the light receiving unit 5, assuming that the light receiving sensitivity of the CCD array 6 of the light receiving unit 5 has a flat characteristic, as shown in FIG. The outputs (CCD array output) Has, Hbs, Hcs of the CCD array 6 corresponding to the Hb, Hc light are proportional to the integrated values of the LED characteristic curves ha, hb, hc in FIG. The CCD array outputs Has, Hbs, and Hcs in FIG. 27 are obtained by setting the integrated values of the LED characteristic curves ha, hb, and hc to “1” and setting the integrated value Has of the characteristic curve ha to “1”. Are integrated values Hbs and Hcs.

  In this way, even in the same type of LED, there is a variation in the light wavelength. Therefore, even when using a document with an irradiation object having the same spectral characteristic of the original color, the range of variation in the optical wavelength of the LED and the spectral characteristic of the original Overlapping, the electric signal level obtained by photoelectrically converting the reflected light and transmitted light from the document changes, causing a change in the output of the image sensor 1 and the image quality of the read image deteriorates.

  Therefore, the image sensor 1 of the present embodiment has an optical wavelength region that overlaps the range of variation in the optical wavelength region of the spectral characteristics of the LED on the optical path from the LED unit 3 a of the light source unit 3 to the CCD array 6 of the light receiving unit 5. In addition, a filter having a light transmission region in a light wavelength region narrower than the variation range of the light wavelength region of the spectral characteristics of the LED is disposed. For example, when the LEDs of the LED unit 3 have variations in their spectral characteristics in the light wavelength region centered around 520 nm as shown in FIG. 15, as shown in FIG. A filter having a light transmission region in a light wavelength region of about 512 nm to 522 nm is used.

  The output values Hass, Hbss, and Hcss obtained by correcting the output of the CCD array 6 by the shading correction unit 22 using such a filter are as shown in the graph of FIG. As can be seen from FIG. 29, the variations in the output values Hass, Hbss, Hcss are about ½ of the variations in the output values Has, Hbs, Hcs of the CCD array 6 when the filter shown in FIG. 27 is not used. Yes. Therefore, by using the filter, it is possible to suppress the output change of the image sensor 1, that is, the CCD array 6, and to improve the image quality of the read image.

  Here, in order to manufacture such a filter, the step of measuring the spectral characteristics of a plurality of LEDs of the same type having spectral characteristics in the light wavelength range as described above is first performed. Thereby, the spectral characteristic of LED as shown in FIG. 15 is acquired. Then, the light from each of the plurality of LEDs is irradiated onto a predetermined document Gp having the same spectral characteristics as shown in FIGS. Then, the output characteristic of the CCD array 6 that receives the reflected light from the original Gp is measured. Then, a step of obtaining the variation in the light wavelength region of the LED from the measured spectral characteristics of the plurality of LEDs of the same type and the output characteristics of the CCD array 6 that receives the reflected light from the original Gp is performed. Here, the variation in the light wavelength region of the LED is obtained from the outputs Ha, Hb, and Hc shown in FIGS. 17 and 26 and the output values Has, Hbs, and Hcs in FIGS. Then, a step of determining a light transmission region that is narrower than the light wavelength region of the spectral characteristics of the LED and that includes the range of variation of the light wavelength region of the LED is performed. Here, as an example of the light transmission region including the variation range of the light wavelength region of the LED, a range as illustrated in FIGS. 19, 28, and 30 is determined. And the process which manufactures the filter which has the determined light transmission area | region by the method similar to the past is implemented. Thereby, the filter of the present embodiment is manufactured.

  In the example shown in FIG. 28, the filter is configured to have a light transmission region in the light wavelength region of about 512 nm to 522 nm. However, the effect of suppressing the output change of the CCD array 6 is improved as the light transmission region is narrower. To do. However, when the light transmission region is narrowed, the influence on the S / N ratio due to the decrease in the light amount increases. For this reason, you may comprise so that the light transmissive area | region of a filter may be larger than the example shown in FIG.

  FIG. 30 is a graph showing the filter characteristics of a filter having a light transmission region range (about 508 to 528 nm) that is approximately twice the light transmission region range of the filter of FIG. Using such a filter, irradiation light is emitted from an LED having the same spectral characteristics as in the example of FIG. 15 onto the original Gp having the same spectral characteristics as in the example of FIG. FIG. 21 shows output values Hass, HbSS, and Hcss after receiving the light and performing shading correction. As shown in FIG. 31, the variations in the output values Hass, HbSS, and Hcss are somewhat larger than the variations in the output values in the example shown in FIG. 29, but the influence of the S / N ratio can be reduced. It becomes.

  In FIG. 25, the spectral characteristics of a cyan document are taken as an example, and the light transmission range of the filter when this document Gp is used has been described. However, the document for other colors such as yellow and magenta is described. In the case of spectral characteristics, it goes without saying that the light transmission range of the filter can be determined in the same manner as described above.

  FIG. 32 is a graph showing the spectral characteristics of a magenta, cyan, and blue document with respect to wavelength. FIG. 33 is a graph showing the spectral characteristics of yellow, cyan, and green documents with respect to wavelength. FIG. 34 is a graph showing spectral characteristics of yellow, magenta, and cyan originals with respect to wavelength. Even in the case of LEDs having different wavelengths, the light transmission range of the filter may be determined so as to include a range of variation in spectral characteristics using a document having spectral characteristics having an inclination.

  The image sensor 1 according to the present embodiment is applied to an image reading apparatus such as a composite apparatus, a copying apparatus, and a facsimile apparatus.

  Therefore, the image quality of the read image read by the image reading apparatus can be improved, and the usability of the read image data can be improved.

  Furthermore, when the light source unit 3 includes three LEDs 3r, 3g, and 3b having different spectral wavelength ranges, the image sensor 1 according to the present embodiment emits light by shifting the light emission timings of these LEDs 3r, 3g, and 3b. The light emitted from the LEDs 3r, 3g, and 3b is irradiated on the original Gp, reflected, and is incident on the CCD array 6 of the light receiving unit 5 so as to correspond to the LEDs 3r, 3g, and 3b. It is assumed that each filter has a light transmission region having a light wavelength region narrower than the light wavelength region in the light wavelength region of the spectral characteristics of the corresponding LEDs 3r, 3g, and 3b.

  Therefore, even if the LEDs 3r, 3g, and 3b, which are light emitting elements, are inexpensive and low-rank, the spectral characteristics have variations in the light wavelength region, and the reflection characteristics of the original Gp that is the irradiation target are inclined. The influence of the dispersion and reflection characteristics of these spectral characteristics in the light wavelength range can be absorbed by the light transmission characteristics in the light wavelength range narrower than the light wavelength range of the spectral characteristics of the corresponding LEDs 3r, 3g, 3b of each filter. The output of the CCD array 6 can be stabilized. As a result, the quality of the image data output from the CCD array 6 can be improved at a low cost, and the usability can be improved at a low cost.

  Further, the image sensor 1 of the present embodiment has a light transmission region in each light wavelength region of the plurality of LEDs 3r, 3g, 3b as a filter, and the LED 3r corresponding to the light wavelength region of each light transmission region. What is narrower than the light wavelength region of 3g and 3b is used.

  Therefore, the dispersion of the spectral characteristics of the LEDs 3r, 3g, 3b and the influence of the reflection characteristics of the original Gp can be absorbed by an inexpensive and small filter, and the image data output from the CCD array 6 can be absorbed. The quality can be improved at a low cost, and the image sensor 1 can be downsized.

  Furthermore, in the image sensor 1 of the present embodiment, the filter is disposed on the optical path from the LEDs 3r, 3g, and 3b of the light source unit 3 to the document Gp.

  Therefore, it is possible to absorb the variation in the light irradiated to the document Gp, suppress the variation in the light reflected from the document Gp to the CCD array 6, and stabilize the output of the CCD array 6. As a result, the quality of the image data output from the CCD array 6 can be improved at a low cost, and the usability can be improved at a low cost.

  In the image sensor 1 of the present embodiment, the light source unit 5 includes the light guide 3b that guides the light from the LED to the document Gp, and the filter transmits the light that enters the light guide 3b from the LED. On the optical path, for example, the light guide 3b may be disposed at the incident portion.

  If it does in this way, a filter area can be made small and the image sensor 1 can be reduced in size.

  Furthermore, in the image sensor 1 of the present embodiment, the filter may be disposed on the optical path from the document Gp to the CCD array 6.

  In this way, it is easy to attach the filter, and the filter can be added even when the image reading apparatus is assembled without being influenced by the configuration of the light source unit 3, and a manufacturing process without a filter is possible. Therefore, versatility can be improved by easily changing to a manufacturing process with a filter.

  Further, the filter may be provided at the entrance to the CCD array 6 or in the vicinity of the CCD array 6.

  If it does in this way, attachment of a filter will be easy, and it will not be influenced by the structure of the light source part 3, but versatility can be improved.

The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. Needless to say.
It should be noted that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  INDUSTRIAL APPLICABILITY The present invention can be used for a light irradiation apparatus and an image reading apparatus that irradiate an irradiation target such as a document from a light emitting element having a variation in spectral characteristics and use reflected light from the irradiation target.

It is a disassembled perspective view of the image sensor of this Embodiment. It is side surface sectional drawing of the image sensor of this Embodiment. It is explanatory drawing of the structure system of LED of the light source part of the image sensor of this Embodiment. It is the front view in the case of having the light guide of the light source part of the image sensor of this Embodiment, and a top view. FIG. 4 is a side sectional view of a two-lamp configuration and a side sectional view of a one-lamp configuration when the light guide of the light source unit of the image sensor of the present embodiment is not provided. It is a perspective view of the SELFOC lens array as a lens of the image sensor of this Embodiment. It is a perspective view of a roof mirror lens array, a lens array, and a separation mirror as lenses of the image sensor of the present embodiment. It is the schematic perspective view of the plate-shaped lens array as a lens of the image sensor of this Embodiment, a front view, and a top view of a plate glass lens. It is a perspective view of the telecentric lens array as a lens of the image sensor of this Embodiment. It is a schematic block diagram of a contact type image sensor. It is a schematic block diagram of the image sensor of a reduction type optical system. It is drive explanatory drawing of RGB LED of the image sensor of this Embodiment. 4 is a timing chart of RGB LED drive timing, output clock, and CCD output of the image sensor of the present embodiment. It is a block block diagram of the image process part which processes the output image data of the image sensor of this Embodiment. It is a graph which shows the spectral characteristic which has the variation of LED. It is a graph which shows an example of the reflective characteristic of an original. FIG. 18 is a graph showing the spectral / reflective characteristics of reflected light when the LED having the spectral characteristics shown in FIG. It is a graph which shows the output characteristic at the time of carrying out photoelectric conversion of the reflected light of the spectrum and reflection characteristic of FIG. 17 with the CCD array of the image sensor of this Embodiment. It is a graph which shows the transmission characteristic of the filter arrange | positioned at an image sensor with respect to LED which has the spectral characteristic of FIG. FIG. 20 is a graph showing the spectral / transmission characteristics when the light of each LED having the spectral characteristics of FIG. 15 passes through the filter having the transmission characteristics of FIG. 19. FIG. 21 is a graph showing spectral / transmission / monochrome correction characteristics when black-and-white correction is considered for the light of spectral / transmission characteristics shown in FIG. 20. FIG. 22 is a graph showing the spectral, transmission, black and white correction, and reflection characteristics of reflected light when the original having the spectral, transmission, and black and white correction characteristics shown in FIG. It is a graph which shows the output characteristic at the time of carrying out the photoelectric conversion of the light of the spectral / transmission / monochrome correction / reflection characteristics of FIG. 22 by the CCD array of the image sensor of the present embodiment. It is a graph which shows the transmission characteristic of the filter of another example. 6 is a graph illustrating another example of spectral characteristics of a cyan document. It is a graph which shows the output characteristic at the time of carrying out photoelectric conversion of the reflected light of the spectrum and reflection characteristic of FIG. 25 with the CCD array of the image sensor of this Embodiment. It is a graph which shows the transmission characteristic of the filter arrange | positioned at an image sensor with respect to LED which has the spectral characteristic of FIG. FIG. 28 is a graph showing the spectral / transmission characteristics when the light of each LED having the spectral characteristics of FIG. 15 is transmitted through the filter having the transmission characteristics of FIG. 27. FIG. 29 is a graph showing spectral / transmission / monochrome correction characteristics when monochrome correction is taken into consideration for the light of spectral / transmission characteristics shown in FIG. 28. 6 is a graph showing another example of spectral / transmission characteristics of a filter. FIG. 31 is a graph showing spectral / transmission / monochrome correction characteristics when black-and-white correction is taken into consideration for the light of spectral / transmission characteristics shown in FIG. 30. It is a graph which shows the other example of the spectral characteristic of the original of a magenta color, a cyan color, and a blue with respect to a wavelength. It is a graph which shows the other example of the spectral characteristic of the original of yellow, cyan, and green with respect to a wavelength. 6 is a graph showing another example of spectral characteristics of yellow, magenta, and cyan originals with respect to wavelengths.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image sensor 2 Optical housing 3 Light source part 3a LED part 3b Light guide 3c LED array 3r, 3g, 3b LED
4 Lens 4a Selfoc lens array 4b Roof mirror lens array 4c Lens array 4d Separating mirror 4e Plate lens array 4f Telecentric lens array 5 Light receiving unit 6 CCD array 7 Contact glass 8 Mirror 9 Lens 20 Image processing unit 21 Image input unit 22 Shading Correction unit 23 Interline interpolation unit 24 RGBγ correction 25 RGB / YCbCr conversion unit 26 Filter unit 27 YCbCr / RGB conversion unit 28 Sub-scanning scaling unit 29 Main scanning scaling unit 30 Error diffusion / dithering unit 31 RGB input gray output unit 32 Error diffusion / dither section 33 RGB input RGB output section 34 RGB / CMYK color space modulation section 35 CMYKγ correction section 36 Error diffusion / dither correction section 37 RGB input CMYK output section Gp Document Ib, Ir, Ig Drive current a to Hc Spectral characteristic curve ha, hb, hc Characteristic curve Has, Hbs, Hcs CCD array output haf, hbf, hcf Spectral / transmission characteristic curve hafs, hbfs, hcfs Spectral / transmission / monochrome correction characteristic curve hafsg, hbfsg, hcfsg spectral・ Transmission / monochrome correction / reflection characteristics curve Hass, Hbss, Hcss CCD array output

Claims (8)

Having a light emitting element having spectral characteristics in a predetermined light wavelength region, and emitting a light to the irradiation object by causing the light emitting element to emit light; and
A light-receiving element having sensitivity in the light wavelength region of the light-emitting element, and receiving and photoelectrically converting reflected light or transmitted light from the irradiation object by the light-receiving element;
A range of variation in the light wavelength region of the light emitting element that is disposed on the optical path from the light emitting element through the irradiation object to the light receiving element, narrower than the light wavelength range of the spectral characteristics of the light emitting element. A filter having a light transmissive region comprising:
An optical apparatus comprising: An image reading apparatus that includes an optical device that photoelectrically converts light reflected or transmitted by a document by irradiating the document with reading light, and that reads an image of the document by an electrical signal output from the optical device,
The optical device comprises:
Having a light emitting element having spectral characteristics in a predetermined light wavelength region, and emitting a light to the irradiation object by causing the light emitting element to emit light; and
A light-receiving element having sensitivity in the light wavelength region of the light-emitting element, and receiving and photoelectrically converting reflected light or transmitted light from the irradiation object by the light-receiving element;
A range of variation in the light wavelength region of the light emitting element that is disposed on the optical path from the light emitting element through the irradiation object to the light receiving element, narrower than the light wavelength range of the spectral characteristics of the light emitting element. A filter containing
An image reading apparatus comprising: The light source unit includes a plurality of light emitting elements having different light wavelength ranges of the spectral characteristics, and causes the plurality of light emitting elements to emit light at different light emission timings,
A plurality of the filters are disposed corresponding to the plurality of light emitting elements,
Each of the plurality of filters has the light transmission region that is narrower than the light wavelength region of the spectral characteristics of the light emitting element corresponding to the filter and includes a range of variation of the light wavelength region of the light emitting element. The image reading apparatus according to claim 2, wherein: The light source unit includes a plurality of light emitting elements having different light wavelength ranges of the spectral characteristics, and causes the plurality of light emitting elements to emit light at different light emission timings,
The filter has a light transmission region that is narrower than each light wavelength region of the spectral characteristics of each of the plurality of light emitting elements and includes a variation range of each light wavelength region of the plurality of light emitting elements. The image reading apparatus according to claim 2.   The image reading apparatus according to claim 2, wherein the filter is disposed on an optical path from the light emitting element of the light source unit to the irradiation target. The light source unit further includes a light guide that guides light from the light emitting element to the irradiation object,
The image reading apparatus according to claim 2, wherein the filter is disposed on an optical path of light incident on the light guide from the light emitting element.   The image reading apparatus according to claim 2, wherein the filter is disposed on an optical path from the irradiation object to the light receiving element. A first measurement step of measuring spectral characteristics of a plurality of light emitting elements of the same type having spectral characteristics in a predetermined light wavelength range;
A second measuring step of irradiating a document having predetermined identical spectral characteristics with light from each of the plurality of light emitting elements and measuring output characteristics of the light receiving element that receives the reflected light;
A third measurement step for obtaining a variation in the light wavelength region of the light emitting element based on the measured spectral characteristics of the plurality of light emitting elements and the output characteristics of the light receiving element;
A determination step of determining a light transmission region that is narrower than the light wavelength region of the spectral characteristics of the light emitting element and includes a range of variation of the light wavelength region of the light emitting element;
A manufacturing process for manufacturing a filter having the determined light transmission region;
The filter manufacturing method characterized by including.

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