JPH09200456A - Image reading device - Google Patents

Abstract

(57) An object of the present invention is to obtain an image reading device in which unevenness of image data due to filament unevenness is prevented. SOLUTION: A halogen lamp having a plurality of light emitting points, an optical system for forming an image of reflected light of an original by the halogen lamp, a photoelectric converter for converting the formed image into an electric signal, and correcting the electric signal. An image reading apparatus is configured to include a shading correction circuit and a reference color plate that serves as a reference during correction. In this configuration, the reference color plate is composed of a reference white plate whose gloss level changes continuously, and the gloss level is selectively switched by moving the position of the reference white plate. By performing shading correction on the basis of data read by selecting and reading a reference color plate that matches the glossiness of the document, it is possible to prevent unevenness in the light amount of illumination from appearing as image unevenness due to the glossiness of the document. The standard color plate is white plate, blackboard, white plate /
For any of the blackboards, the change in gloss may be a gradual change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device, and more particularly to an image reading device having a digital reading optical system and applied to a copying machine, an image scanner or the like.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus generally uses a rod-shaped halogen lamp as a light source of an optical system. This rod-shaped halogen lamp usually has 7 to 8 filaments,
It is arranged in a straight line with a certain space and is enclosed in a glass tube together with a halogen gas. Further, the surface of the glass tube is frosted in the form of frosted glass in order to irradiate uniform illumination light.

However, as a problem due to the use of the rod-shaped halogen lamp, there is light amount ripple due to the filament. The filament portion has a higher amount of light than other portions, and cannot be sufficiently processed by the above frost processing. Therefore, many illumination systems have so-called light amount ripples. In an analog copying machine, light amount ripples cause image unevenness, and some proposals have been made to prevent this.

Japanese Patent Laid-Open No. 3-31839 "Image reading device"
Argues that by arranging the diffusing member in the predetermined optical path so that it can be inserted and removed, the image information can be read with high accuracy regardless of the image information.

In Japanese Utility Model Laid-Open No. 4-135070, "image reading device", a plurality of filaments are arranged in a long tube at predetermined intervals so as to face each other between the filament positions of other halogen lamps. Is characterized by.

In a digital copying machine, a shading plate arranged in the main scanning direction is read by a CCD in advance and stored therein, and data obtained by reading an image is divided by this to correct a light amount ripple, so-called shading correction is performed. . For this reason, it is said that a digital copying machine is unlikely to be affected by light amount ripple due to a filament. In fact, when the document almost diffuses the irradiation light, the shading correction described above can correct the light amount ripple due to the filament.

[0007]

However, when a part of the original document is specularly reflected, the above shading correction may not be successful. Generally, when the original has a glossy surface parallel to the contact glass, the emitted light is totally reflected and the copied image becomes black. However, in the case of a glossy surface that is not parallel, it may be reflected and jump directly into the optical path. In this case, the light amount of the portion where the filament is present is higher than that of the other portions, and the copy image becomes whitish only in the portion where the filament is present, which is called filament unevenness. That is, the correction data for shading correction is data for the diffused reference plate, and the light amount distribution for reflected light is different.

As a document causing such a phenomenon, a product catalog or the like using a paper with fine wrinkles, which is particularly glossy and blackish, is easily affected. In addition, a pattern, such as a printed circuit board, having a raised pattern and having gloss due to resist processing, and having patterns running in parallel in a certain direction is also susceptible to the problem. Both are likely to be originals in color copiers.

It is an object of the present invention to provide an image reading apparatus which prevents the occurrence of image data unevenness due to filament unevenness.

[0010]

In order to achieve the above object, the image reading apparatus of the present invention comprises an illuminating unit having a plurality of light emitting points, and an optical unit for forming an image of reflected light of a document by the illuminating unit. A photoelectric conversion unit that converts the formed image into an electric signal, a shading correction unit that corrects the electric signal, and a reference color plate that serves as a reference during correction, and selectively switches the glossiness of the reference color plate. Is characterized by.

If the above-mentioned reference color plate is used as a reference white plate, and the glossiness varies depending on the position in the sub-scanning direction, the selective switching is executed by moving the reading position of the reference white plate. Good.

Furthermore, the movement of the reading position of the reference white plate may be configured such that the glossiness of the reference white plate changes stepwise or continuously by the movement of the reference white plate.

The reference color plate is a reference white plate and a reference blackboard. Further, the image reading apparatus has an operation unit for operating the operation of reading the original image, and the glossiness is selected by the operation unit. The image reading may be selectively switched between turning off the lighting means and turning on the lighting means when reading the reference blackboard depending on the state of the original.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an image reading apparatus according to the present invention; FIG.
~ Referring to Fig. 16, there is shown a first embodiment and a second embodiment of the image reading apparatus of the present invention. 1 to 5
Is a common view of the first and second embodiments, FIGS. 6 to 11 show the first embodiment, and FIGS. 12 to 16 are supplementary views for explaining the second embodiment. .

FIG. 1 is an embodiment of an overall configuration diagram of an image reading apparatus of the present invention. Further, FIG. 2 is a detailed view of an optical path portion in FIG. In FIG. 1 and FIG. 2, the light of the halogen lamp is condensed by the left and right reflectors and illuminates the original on the contact glass, and the reflected light is reflected by the first, second and third mirrors, and is reflected by the lens. Is imaged on the CCD by. The CCD photoelectrically converts the original image to generate an electric signal. This signal is sent to the scanner substrate as an image signal and subjected to various signal processing. A first scanner including a halogen lamp and a reflector and a second scanner including second and third mirrors move from left to right in the figure to read an original. Prior to the start of reading the original, the reference color plate arranged further to the left is read.
Data in the main scanning direction obtained by reading the reference color plate is stored as data used for shading correction.

Two embodiments of the above-mentioned image reading apparatus will be described below. These two
The difference between the image reading apparatuses of the two embodiments lies in the reference color plate. In the first embodiment, the reference color plate is only the reference white plate. In the second embodiment, the reference white board and the reference blackboard are 2
Configure by type. Therefore, the above-mentioned shading correction is performed in the first embodiment based on the read data of the reference white board, and in the second embodiment, the data in the main scanning direction obtained by reading the reference white board and the reference blackboard are respectively shaded. It is stored as data used for correction. The data used for this shading correction is called white shading data / black shading data.

FIG. 3 is a structural diagram of a halogen lamp. Terminals for applying a voltage are provided at both ends, and there are a plurality of coiled filament parts (7 points in this figure) inside the frosted glass tube. Since the filament portion emits light, the entire lamp is slightly diffused by the frosting of the glass tube, but the filament portion is bright and the other portions are dark, resulting in uneven light emission.

In the case of a non-glossy original (majority of originals), the light emitted from the halogen lamp / reflector diffuses to a high degree, so the CCD output waveform for a white original is:
The flat waveform shown in FIG. 4 is obtained. On the other hand, in the case of a glossy original (a small number of originals), since the degree of specular reflection light from the original is high, uneven light amount due to filament unevenness of the lamp appears, and the CCD output waveform for a white original is The waveform is as shown in FIG.

Conventionally, since a white plate having no gloss is generally used as the reference color plate, the shading correction data stores the waveform data as shown in FIG. If a glossy white plate is used as the reference color plate, the shading correction data will be as shown in FIG.
The waveform data such as is stored. If shading correction is performed using this data when reading the glossy original, it is possible to reduce or eliminate unevenness in the light amount due to filament unevenness by the shading correction.

<First Embodiment> FIG. 6 is an overall block diagram of the first embodiment. R from the color CCD 101
The G and B outputs are amplified and gain adjusted (AGC) by the analog processing circuit 102, and then converted into 8-bit digital signals of each color by the A / D converter 103. After A / D, the shading correction circuit 104 performs shading correction using the data from the line memory 105 that stores the data (3 × 5K × 8 bits) for one line of each color obtained by reading the reference white plate. Shading correction is performed on the Nth pixel in the main scanning direction by input data DNI and post-correction data DNI.
If NO and the shading data from the line memory 105 is DNS, the following equation (1) is calculated. Equation (1)
The 8-bit data for each color after correction based on the calculation of is output as the output of the reading device. DNO = 255 × DNI / DNS (1)

The control unit 106 controls the entire apparatus centering on the CPU. The carriage drive circuit 108 is controlled while controlling the timing signal to each unit related to the image data signal described above.
The optical system is moved by a stepping motor or the like to read the original. Further, as the first embodiment, when the reference white plate is moved, the reference white plate drive circuit 109 is controlled to move the reference white plate with a stepping motor or the like, and the portion having the desired glossiness is brought to the reading position. The operation unit 107 transmits an operator's setting input, start input, and the like to the control unit 106, and performs a reading operation based on the input instruction. As one of the setting inputs, there is an original gloss selection key as shown in FIG. 7, and by adjusting this key to the original gloss,
The control unit 106 controls to read the reference white plate portion having the same glossiness as the shading data.

In FIG. 8, a reference white plate whose gloss level changes continuously is provided, and the position of the reference white plate of gloss level matched to the original is shown.
6 illustrates an embodiment for reading shading data. In the case of a non-glossy normal document, the control unit 106 controls the carriage drive 108 and the line memory 105 so that the shading data is read and stored at the left end position where the glossiness is the minimum. If the shading data is read in a position on the right side as the glossiness of the original becomes higher, shading correction can prevent image unevenness due to filament unevenness.

9 to 11 show examples in which the position where the optical system reads the reference white plate is constant, the reference white plate moves, and the glossiness of the reference white plate is changed. In FIG. 9, a flat reference white plate (reference blackboard) moves left and right. The reference white plate is a white plate whose glossiness changes in four steps. FIG. 10 shows an example in which the belt-shaped reference white plate is rotated to switch the glossiness. FIG. 11 shows an example in which the cylindrical reference white plate rotates to switch the glossiness. In each case, the reference white plate is a white plate whose glossiness changes in four steps. Of course, it is also possible to use a stepwise reference white plate in the embodiment of FIG.
It is also possible to use a continuous reference white plate in the first embodiment, and the combination is free.

<Second Embodiment> The second embodiment is a case where the reference color plates are a reference blackboard and a reference white plate. Based on this configuration, the reference color plate of FIGS. 1 and 2 becomes a reference blackboard / reference white plate as shown in FIG.

The CCD output waveform obtained by reading the reflected light of the reference blackboard using a blackboard having no gloss as the reference color plate has a waveform as shown in FIG. Since there is almost no reflected light, the waveform has a variation in the output of each pixel of the CCD (nonuniformity of output in the dark). If a glossy blackboard is used, the light intensity unevenness component due to the filament unevenness of the lamp is superimposed on the waveform of FIG. 13 due to the higher degree of specular reflection light, resulting in a waveform as shown in FIG. As black shading data, waveform data as shown in FIG. 13 or 14 is stored according to the glossiness of the original. These white and black shading
If the shading correction is performed using the data when reading the glossy original, it is possible to reduce or eliminate the uneven light amount due to the filament unevenness by the shading correction.

FIG. 15 is an overall block diagram of the second embodiment. The difference between the second embodiment and the first embodiment lies in the reference white board / blackboard drive circuit. When moving the reference whiteboard or the reference blackboard in the present embodiment, the reference whiteboard reference blackboard driving circuit 109 is controlled to move the reference whiteboard or the reference blackboard with a stepping motor or the like, and the portion having the desired glossiness is moved to the reading position. I will bring. By adjusting the gloss of the original using the original gloss selection key shown in FIG. 7, the control unit 106 reads the reference blackboard portion and the reference whiteboard portion having the same glossiness as black shading data and white shading data. Control. FIG.
2 is a standard white plate (standard blackboard) whose glossiness changes continuously
A standard white board (standard blackboard) with a gloss level that matches the original
At the position of, shading data is read.

The shading correction is performed on the N-th pixel in the main scanning direction with the input data DNI, the corrected data DNO, and the (white shading.
Data is DNWS, black shading data is DNBS)
Then, the calculation of the following equation (2) is performed. The corrected 8-bit data of each color is output as the output of the reading device. DNO = 255 × (DNI−DNBS) / (DNWS−DNBS) (2)

In the case of a normal original having no gloss, the controller 106 drives the carriage 108 so that the shading data is read and stored at the left end position where the glossiness is the minimum.
And the line memory 105 are controlled. If the shading data is read in a position on the right side as the glossiness of the original becomes higher, shading correction can prevent image unevenness due to filament unevenness.

It is also possible to continuously use the reference whiteboards of FIGS. 9 to 11 described in the first embodiment as reference blackboards / whiteboards.

FIG. 16 shows a flowchart of the operation example 1 of the second embodiment in the above-described hardware configuration. Upon receiving the reading start command, the lamp is turned on and the carriage is started. If the original is a non-glossy original,
The black shading data and the white shading data are read and stored at the minimum glossiness positions of the reference blackboard and the reference whiteboard, respectively. If the original is glossy, the gloss level is input from the operation unit, and black shading data and white shading data are read and stored at the appropriate glossiness positions of the reference blackboard and reference whiteboard accordingly. To do. After that, when the reading of the original is started, the original is read while executing the shading correction.

According to the above embodiment, since the glossiness of the reference color plate is selected and the shading correction of the read data is performed by the correction data of the selected reference white plate / reference blackboard,
It is possible to accurately correct light amount unevenness and image unevenness caused by the glossiness of the original. Further, the reference color plate is a reference white plate, the glossiness is different depending on the position in the sub-scanning direction, and the switching is performed by moving the reading position of the reference white plate.

A flowchart of another operation example 2 is shown in FIG. Carriage start in response to the scan start command. If the original is a non-glossy original, the black shading data is read and stored at an arbitrary position while the lamp is off. Since it is an arbitrary position, it may be performed before the carriage start. Next, the lamp is turned on, and the white shading data is read and stored at the minimum glossiness position of the reference white plate. If the original is glossy, the lamp is turned on, and the black shading data and the white shading data are read and stored at the proper gloss positions of the reference blackboard and the reference white plate in response to the input from the operation unit. Then, the original is read while shading correction is performed.

Since a lamp is turned off for a long time in a normal original having no gloss, heat generation can be suppressed during a large number of continuous copies. It also saves power.

[0034]

As is apparent from the above description, the image reading apparatus of the present invention has a reference color plate which serves as a reference when shading correction is performed on an imaged electrical signal, and the glossiness of the reference color plate is selected. Switch. Therefore, by selecting the reference color plate that matches the glossiness of the original and reading the data,
By performing the shading correction, it is possible to prevent the unevenness of the light amount of the illumination from appearing as an uneven image due to the glossiness of the original.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an image reading apparatus of the present invention.

FIG. 2 is a detailed view of an optical path portion in FIG.

FIG. 3 is a configuration diagram of a halogen lamp.

FIG. 4 is a correction data example 1 for explaining shading correction.

FIG. 5 is a correction data example 2 for explaining shading correction.

FIG. 6 is an overall block diagram of the first embodiment.

FIG. 7 is a plan view of a selection key.

FIG. 8 is a diagram showing a configuration example using a reference white plate whose glossiness changes continuously.

FIG. 9 is a diagram showing a configuration example in which a reference color plate moves to change glossiness.

FIG. 10 is a diagram showing a configuration example of a belt-shaped reference color plate.

FIG. 11 is a diagram showing a configuration example of a cylindrical reference color plate.

FIG. 12 is a diagram showing a configuration example in which a reference color plate is composed of a reference white plate and a reference blackboard.

FIG. 13 is a diagram showing an example of correction data of reflected light on a reference blackboard having no gloss.

FIG. 14 is a diagram showing an example of correction data of reflected light on a glossy reference blackboard.

FIG. 15 is an overall block diagram of a second embodiment.

FIG. 16 is a flowchart of an operation example 1 of the second embodiment.

FIG. 17 is a flowchart of an operation example 2 of the second embodiment.

[Explanation of symbols]

 101 CCD 102 Analog processing circuit 103 A / D converter 104 Shading correction circuit 105 Line memory 106 Control unit 107 Operation unit 108 Carriage drive unit 109 Reference whiteboard drive unit 209 Reference blackboard / whiteboard drive unit

Claims (9)

[Claims] 1. An illuminating unit having a plurality of light emitting points, an optical unit for forming an image of reflected light of a document by the illuminating unit, a photoelectric conversion unit for converting the formed image into an electric signal, and the electric signal. An image reading apparatus comprising: a shading correction unit that corrects the color difference and a reference color plate that serves as a reference during the correction, and selectively switches the glossiness of the reference color plate. 2. The image reading apparatus according to claim 1, wherein the reference color plate is a reference white plate. 3. The reference white plate is configured so that the glossiness varies depending on the position in the sub-scanning direction, and the selective switching is executed by moving the reading position of the reference white plate. Item 2. The image reading device according to item 2. 4. The movement of the reading position of the reference white board is
The image reading apparatus according to claim 3, wherein the image reading apparatus is executed by moving a reference white plate. 5. The image reading apparatus according to claim 2, wherein the reference white plate is configured so that the glossiness changes stepwise. 6. The image reading apparatus according to claim 2, wherein the reference white plate has a glossiness that continuously changes. 7. The image reading apparatus according to claim 1, wherein the reference color plates are a reference white plate and a reference blackboard. 8. The image reading apparatus according to claim 1, wherein the image reading apparatus further includes an operation unit for operating a reading operation of a document image, and the glossiness is selected by the operation unit. . 9. The reading of the original image is selectively switched between turning off the lighting unit and turning on the lighting unit when reading the reference blackboard depending on the state of the original. The image reading apparatus according to claim 8.