JP7280550B2 - Image reader - Google Patents

Description

The present invention relates to an image reading apparatus using a contact image sensor unit for optically reading a document.

A contact image sensor (CIS), which is brought into close contact with a document and optically reads the document, consists of a light source unit that irradiates the document with uniform light in the main scanning direction, and a light receiving element that is aligned with a line in the main scanning direction. Photoelectric conversion units arranged in a shape and a rod lens array that forms an image on the light receiving element of the photoelectric conversion unit with the light emitted from the light source and reflected by the document are integrated into one housing. . Therefore, by using the contact image sensor unit, it is possible to realize a thin and compact image reading device as compared with the case of adopting a reduction optical system.

An image reading apparatus reads a white reference plate before reading a document, and performs shading correction for correcting light amount unevenness based on the read data. At this time, if dust adheres to the white reference plate or the incident surface of the rod lens array of the contact image sensor unit, appropriate shading correction becomes difficult.

Japanese Patent Application Laid-Open No. 2002-200002 discloses a technique that can reduce the influence of dust, dirt, and noise attached to a white reference member even when shading correction is performed using shading data obtained by reading the white reference member for each document. It is In this reading device, corrected main data obtained by shading correction of image data (main data) using main shading data obtained for each document, and noise components obtained in advance before the start of the job are removed. The sub shading data is used to compare the corrected sub data obtained by shading correcting the same image data, and for portions where the difference between the two is large, the corrected main data is interpolated with the corresponding corrected sub data.

JP 2006-013833 A

In the technique disclosed in Patent Document 1, it is necessary to prepare sub shading data for comparison with main shading data, which complicates the device configuration and correction processing.

By the way, in the contact image sensor unit, the reflected light from the document passes through the rod lens array and is received by the image sensor. A periodic increase/decrease due to optical characteristics (periodic level change due to lens diameter) is shown. Techniques for detecting the adhesion of dust have been devised by utilizing the fact that when dust is attached, the amplitude and cycle of the periodic level increase and decrease are disturbed.

In this detection method, it is not necessary to prepare sub-shading data. It turns out that there is something to show. Furthermore, in the contact image sensor unit, if dust is actually attached and inspected in order to determine whether or not it is suitable for a dust adhesion detection method using optical characteristics, the number of inspection man-hours increases excessively. Further, even if the contact image sensor unit is not suitable for the use of the dust adhesion detection method using optical characteristics, it is desired to incorporate it into the image reading apparatus and use it effectively, as long as the sensor output inspection is passed.

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems, and provides an image that can effectively utilize both a contact image sensor unit that is suitable for a dust adhesion detection method using optical characteristics and a contact image sensor unit that is not suitable. A first object is to provide a reader. A second object of the present invention is to provide an image reading apparatus having a function of determining whether or not a contact image sensor unit is suitable for a dust adhesion detection method using optical characteristics.

The gist of the present invention for achieving this object lies in the following inventions.

[1] a first reading section having a structure in which an image on a curved document is read by a contact image sensor unit from the outside of the document and the contact image sensor unit is movable with respect to a white reference member;
a second reading unit having a structure in which the contact image sensor unit reads an image on the document from the inside of the curved document, and the contact image sensor unit is fixed to a white reference member;
a first dust adhesion detection unit that detects dust adhesion in the first reading unit;
a second dust adhesion detection unit that detects dust adhesion in the second reading unit;
with
The contact image sensor unit of the second reading section reads read data obtained by reading a white reference member in a dust-free state for each sensor IC and for each color, and scans the rod lens array of the contact image sensor unit . Divided into sections corresponding to the lens cycle, find the difference by subtracting the minimum value from the maximum value in each section, and the average value or minimum value of the difference for each sensor IC and for each color is all greater than or equal to a predetermined threshold. It satisfies the condition of
The contact image sensor unit of the first reading unit does not satisfy the conditions,
The second dust adhesion detection section detects the first read data obtained by reading the white reference member in a state where dust is not adhered by the contact image sensor unit at the lens period of the rod lens array of the contact image sensor unit. By comparing the corresponding periodic change characteristic with the periodic change characteristic of the second read data obtained by reading the white reference member with the contact image sensor unit, the reading time of the second read data is determined. Detect dust adhesion,
The image reading device, wherein the first dust adhesion detection section detects adhesion of dust by a detection method different from that of the second dust adhesion detection section.

In the above invention, the second reading section, in which the positional relationship between the white reference member and the contact image sensor unit is fixed, includes the first reading obtained by reading the white reference member with the contact image sensor unit in a dust-free state. Read by comparing the periodic change characteristic corresponding to the lens period of the rod lens array in the read data with the periodic change characteristic of the second read data obtained by reading the white reference member with the contact image sensor unit. A contact image sensor unit equipped with optical characteristics (conditions) that can detect the adhesion of dust at times, and a contact image sensor unit that does not have the optical characteristics It is mounted on the first reading section in which the image sensor unit is movable. The process of determining whether or not the contact image sensor unit has the predetermined optical characteristic value may be performed by the image reading apparatus, or may be performed by an inspection apparatus other than the image reading apparatus.

[2] a collection unit that collects read data by reading the facing white reference member with the contact image sensor unit;
Obtaining the difference for each section from the read data collected by the collecting unit, and determining whether or not the average value or minimum value of the difference for each sensor IC and for each color is equal to or greater than a predetermined threshold value. a computing unit;
The image reading device according to [1], further comprising:

In the above invention, the image reading device has a computing function for determining whether or not the contact image sensor unit satisfies a predetermined condition .

[ 3 ] In judging the condition, the average value or the minimum value is obtained based on the read data after the moving average processing has been performed in units of the section.
The image reading device according to [1] or [2], characterized by:

According to the image reading apparatus of the present invention, dust adhesion detection is performed using the periodic change characteristic corresponding to the lens period of the rod lens array of the contact image sensor unit in the read data when the white reference member is read. Both the contact image sensor unit suitable for the law and the contact image sensor unit not suitable for the law can be effectively used. Further, it is possible to determine whether or not the contact image sensor unit is suitable for the dust adhesion detection method using the periodic change characteristic .

1 is a diagram showing an example of an image reading device according to an embodiment of the present invention; FIG. 2 is a block diagram showing the electrical configuration of the image reading device; FIG. 2 is a cross-sectional view (a cross section perpendicular to the main scanning direction) showing a schematic configuration of a contact image sensor unit; FIG. 3 is a perspective view showing the inside of the contact image sensor unit; FIG. It is a figure which shows the principle and structure of a rod lens array. FIG. 2 is an enlarged view of a photoelectric conversion unit on a sensor substrate and a part thereof; FIG. 10 is a diagram showing an example of Gch light quantity characteristics when a white reference plate is read in a state where dust is not attached; FIG. 10 is a diagram showing an example of Gch light amount characteristics when a white reference plate is read with small dust or the like adhering to a portion adjacent to a rod lens; FIG. 10 is a diagram showing an example of Gch light amount characteristics when a white reference plate is read with small dust adhering to the central portion (optical axis) of the rod lens; FIG. 10 is a diagram showing an example of Rch light quantity characteristics when a white reference plate is read in a state where dust is not adhered; 4 is a flowchart showing an overview of processing performed by the image reading device in a CIS determination mode; FIG. 4 is a diagram showing a list of channel amplitude values (Ave.) and channel amplitude values (Min.) determined for each sensor IC and for each R, G, and B channel; FIG. 13 is a graph of the R color channel amplitude values (Ave.) of each sensor IC in the list of FIG. 12; FIG. 13 is a graph of G-color channel amplitude values (Ave.) of each sensor IC in the list of FIG. 12 ; FIG. 13 is a graph of B-color channel amplitude values (Ave.) of each sensor IC in the list of FIG. 12 ; FIG. 9 is a diagram showing a list of channel amplitude values (Ave.) obtained for each sensor IC and for each color based on values subjected to moving average processing;

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing an example of an image reading device 10 according to an embodiment of the invention. The image reading apparatus 10 has a rectangular thin box-like main body 13 with a platen glass 11 and a translucent glass 12 serving as a reading position during flow reading. An automatic document feeder 16 that feeds out sheets one by one and conveys them to the output tray 15 via the reading position (the surface of the translucent glass 12) on the upper surface of the main body 13, and a contact image sensor unit 17 that reads the back side of the document at the reading position. , a contact image sensor unit 18 for reading the surface of a document at a reading position, and a paper discharge tray 15 serving also as an openable platen cover covering the platen glass 11 .

The automatic document feeder 16 comprises a pair of delivery rollers 16a for holding the leading edge of the document and delivering it from the document platen 14, a transport roller 16b for transporting the delivered document, and a drive section for rotating these rollers. be done. The document is curved along the outer peripheral surface of the transport roller 16b and is transported approximately halfway around, thereby reversing its path and heading to the reading position. When scanning a document conveyed by the automatic document conveying unit 16, the contact image sensor unit 17 reads an image on the document (image on the back side) from the inside of the document bent by the conveying roller 16b. The image sensor unit 18 reads an image on the document (image on the front side) from the outside of the curved document.

The contact image sensor unit 17 reads one line at a time in the main scanning direction (the direction perpendicular to the paper surface in FIG. 1). The contact image sensor unit 17 is arranged to face and be close to the surface of the translucent glass 12, and a white reference plate with high reflectance is placed at a position facing the contact image sensor unit 17 with the translucent glass 12 interposed therebetween. (White reference member) 19a is provided. The positional relationship between the contact image sensor unit 17 and the white reference plate 19a is fixed.

In this manner, the contact image sensor unit reads the image on the document (the image on the front side) from the inside of the document curved by the conveying roller 16b, and the contact image sensor unit is fixed to the white reference member. A second reading unit is assumed to be the reading unit. The second reading section is composed of the contact image sensor unit 17, the white reference plate 19a, the translucent glass 12 between them, and the like.

Similar to the contact image sensor unit 17, the contact image sensor unit 18 performs line-by-line reading in the main scanning direction (the direction perpendicular to the plane of FIG. 1). The contact image sensor unit 18 is held by a moving mechanism (not shown), and is located at a home position (the position indicated by the solid line in FIG. 1) adjacent to and facing the rear surface of the translucent glass 12 and downstream of the contact image sensor unit 17. to the other end of the platen glass 11 along the back surface of the platen glass 11 . A white reference plate (white reference member) 19b for the contact image sensor unit 18 is provided at a position facing the contact image sensor unit 18 at the home position with the translucent glass 12 interposed therebetween. The white reference plate 19b is fixed, and the contact image sensor unit 18 is movable with respect to the white reference plate 19b.

In this manner, the contact image sensor unit reads the image on the document (back side image) from the outside of the document curved by the conveying roller 16b, and the contact image sensor unit moves relative to the white reference member. The provided reading unit is referred to as a first reading unit. The first reading section includes the contact image sensor unit 18, the white reference plate 19b, the translucent glass 12 between them, the moving mechanism for moving the contact image sensor unit 18, the platen glass 11, and the like. The first reading section can read a plurality of locations on the white reference plate 19b by moving the contact image sensor unit 18 in the sub-scanning direction.

Since the contact image sensor unit 18 of the first reading section is movable, it is less susceptible to paper dust than the non-movable contact image sensor unit 17 of the second reading section.

FIG. 2 is a block diagram showing the electrical configuration of the image reading device 10. As shown in FIG. The image reading device 10 connects a CPU (Central Processing Unit) 21, a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 23, an I/F (Interface) section 24, an image processing section 25, and the like via a bus. It has a control circuit unit 20 with a It also has an operation display unit 26 for receiving various operations from the user and for displaying setting screens, operation screens, device status, and the like. The operation display unit 26 displays the determination result of the CIS determination process, which will be described later.

The operation display section 26 is connected to the control circuit section 20 . The I/F section 24 of the control circuit section 20 is connected to the contact image sensor units 17 and 18, the driving section of the automatic document feeder 16, the driving section for reciprocating the contact image sensor unit 18, and the like. .

The ROM 22 stores programs executed by the CPU 21 and various fixed data. The CPU 21 executes various processing/calculations based on programs stored in the ROM 22 . In addition, the CPU 21 executes a program to read the opposing white reference plate with the contact image sensor unit of the inspection object and collect the read data, and based on the read data collected by the collection unit, It functions as a calculation section that derives a predetermined optical characteristic value for each sensor IC constituting the contact image sensor unit. Further, the CPU 21 performs dust adhesion detection processing for detecting whether or not dust is adhered to the incident surfaces of the contact image sensor units 17 and 18 .

The RAM 23 has the function of temporarily storing various data when the CPU 21 executes the program. The image processing unit 25 performs various image processing such as shading correction and color correction on data output from the contact image sensor units 17 and 18 .

When the image reading apparatus 10 reads a document placed on the document platen 14 (when skimming), the document is transported by the automatic document transport section 16 with the contact image sensor unit 18 positioned at the home position. Then, when the document being conveyed passes the reading position, the contact image sensor units 17 and 18 repeatedly perform line-by-line reading to simultaneously read the front and back sides of the document two-dimensionally.

When the image reading apparatus 10 reads a document placed on the platen glass 11 , the contact image sensor unit 18 is moved along the back surface of the platen glass 11 and the contact image sensor unit 18 reads line by line. is repeated to two-dimensionally read one side of the original (the side facing the platen glass 11).

The contact image sensor unit 17 and the contact image sensor unit 18 have basically the same configuration, and the contact image sensor unit 17 will be taken as an example in the following description of the structure of the contact image sensor user unit.

FIG. 3 is a cross-sectional view (cross section perpendicular to the main scanning direction) showing the schematic configuration of the contact image sensor unit 17, and FIG. 4 is a perspective view showing the inside of the contact image sensor unit 17. As shown in FIG. The contact image sensor unit 17 includes a housing 30 and an irradiation section 40 , a rod lens array 50 and a sensor substrate 60 mounted inside the housing 30 .

The contact image sensor unit 17 has a reading range of a predetermined range in the width direction (sub-scanning direction) around the optical axis of the rod lens array 50 at each position in the main scanning direction. Illuminates a uniform light over a minute read range. The rod lens array 50 plays a role of converging the light emitted from the irradiation unit 40 and reflected by the object to be read (original document) existing in the reading range onto the light receiving surface of the photoelectric conversion unit 61 provided on the sensor substrate 60. .

The housing 30 has a hollow quadrangular prism shape elongated in the main scanning direction, and has a long opening in the main scanning direction corresponding to the reading range at the center of the upper surface in the width direction. A permeable body 32 is fitted. The housing 30 may be made of a highly rigid metal such as aluminum, or may be made of reinforced plastic.

The irradiation unit 40 irradiates a reading range with uniform light through the transmissive body 32 . As shown in FIG. 4 , the irradiation unit 40 has a light guide 42 elongated in the main scanning direction and a light source 44 such as an LED (Light Emitting Diode) that irradiates light toward the end of the light guide 42 . For high-speed scanning, as shown in FIGS. 3 and 4, the light guide 42 and the light source 44 are arranged symmetrically in the width direction (sub-scanning direction) about the optical axis of the rod lens array 50. preferably. Note that the irradiation unit 40 may be provided only on one side of the rod lens array 50 as long as the required amount of light can be obtained. Further, although FIG. 4 shows an example in which the light sources 44 are provided at both ends of the light guide 42, the light source 44 may be provided only at one end of the light guide 42. FIG.

It is ideal that the irradiation unit 40 irradiates a reading range centered on the optical axis of the rod lens array 50 with uniform light. It may have a wide irradiation range such that the illuminance distribution is slightly mountain-like.

The sensor substrate 60 receives the light reflected by the object to be read and converged by the rod lens array 50 after being illuminated by the irradiation unit 40, and converts the light into an electric signal, and drives the photoelectric conversion unit 61. A circuit, an analog front end (AFE) that converts analog signals output from the photoelectric conversion unit 61 into digital signals, etc., and a storage unit (nonvolatile memory) 63 that stores various data related to the contact image sensor unit 17 are attached. It is an electrical board. The storage unit 63 stores relative position information between the rod lens array 50 and the photoelectric conversion unit 61, characteristic data of the photoelectric conversion unit 61, and the like.

FIG. 5 is a diagram showing the principle and structure of the rod lens array 50. As shown in FIG. In FIG. 5, a rod lens array 50 is configured by connecting a plurality of cylindrical rod lenses in parallel. The left side of the rod lens array 50 is the document surface, and the right side is the imaging surface (the light receiving surface of the photoelectric conversion section 61). The imaging plane is a position where the light reflected by the document surface converges through the rod lens array 50 and forms an image. The rod lens array 50 has the characteristic that the focal distance L1 between the document surface and the lens surface on the document surface side is equal to the focal distance L2 between the imaging surface and the lens surface on the imaging surface side.

Therefore, when the distance L1 and the distance L2 are equal, the reflected light from the document forms an image correctly on the light receiving surface. , the distance L1 slightly fluctuates. On the other hand, the distance L2 is fixed and does not change when the sensor substrate 60 and the rod lens array 50 are fixed to the housing 30 .

In the rod lens array 50, images are formed by superimposing images formed by adjacent rod lenses. Therefore, when the white reference plate is read, periodic fluctuations in output characteristics due to the diameter size of the rod lenses can be confirmed. be done. That is, since the rod lens array 50 is configured by arranging a large number of rod lenses in the main scanning direction, there is a periodic light amount distribution in the main scanning direction due to the arrangement interval (lens diameter size) of the rod lenses. optical characteristics. When the white reference plate is read, the light amount distribution in the sub-scanning direction on the imaging plane forms mountains around the optical axis.

FIG. 6 is an enlarged view of the photoelectric conversion section 61 on the sensor substrate 60 and a part thereof. The photoelectric conversion unit 61 includes n−1 channel, n channel, and n+1 channel in which light receiving elements corresponding to the number of pixels of one line are arranged in a straight line and adjacent to each other in parallel. The n−1 channel is in charge of R color, the n channel is in charge of G color, and the n+1 channel is in charge of B color, and color filters of corresponding colors are provided in front of the light receiving surface.

The G color channel (Gch) is positioned at the center of the optical axis of the rod lens array 50, and the R and B color channels (Rch, Bch) are positioned on both sides thereof at intervals corresponding to the reading resolution (42 μm when the resolution is 600 DPI). spaced apart). Also, the photoelectric conversion unit 61 is configured by arranging a plurality of sensor ICs in the main scanning direction. For example, when using a sensor IC of 600 DPI, if it is A4 size, the number of effective pixels is about 5168, and the number of pixels in one sensor IC is about 300 pixels, so about 17 sensor ICs are arranged in a line.

It should be noted that it is difficult to arrange and fix a plurality of sensor ICs so that the pixels are aligned perfectly in a straight line. If the deviation falls within the tolerance of the deviation between the sensor ICs in the main scanning direction and the sub-scanning direction), the inspection is passed.

Next, a method for detecting dust adhesion on the incident surface based on the optical characteristics of the contact image sensor unit will be described. The optical characteristics referred to here refer to periodic output changes due to the diameter size of the rod lens when a white reference plate is read.

FIG. 7 is a graph showing the light amount characteristics (output characteristics) of the G color channel (Gch) when reading the white reference plate in a state where no dust adheres. The horizontal axis indicates the pixel number of the main scanning, and the vertical axis indicates the sensor output value (a value obtained by A/D conversion with 10 bits and expressed in decimal notation). As a result of the influence of a plurality of adjacent lens elements, a peak period can be confirmed that is assumed to be due to the diameter factor of the lens elements. The peak corresponds to the optical axis center of each lens element.

FIG. 8 is a graph showing the light intensity characteristics of the G color channel (Gch) when the white reference plate is read with small dust or the like adhering to the portion adjacent to the rod lens. As in FIG. 7, the horizontal axis indicates the main scanning pixel number, and the vertical axis indicates the sensor output value (a value obtained by A/D conversion with 10 bits and expressed in decimal notation). A dotted line frame in FIG. 8 is a portion where the output characteristics are changed due to slight adhesion of dust.

It can be seen that the drop around the 165th pixel is remarkable as compared with the case where dust is not adhered in FIG. As described above, in the portion adjacent to the rod lens where dust is attached, the level at that portion tends to be lower and the amplitude of the output characteristic tends to be larger than when no dust is attached.

FIG. 9 is a graph showing the light amount characteristics of the G color channel (Gch) when the white reference plate is read with small dust adhering to the central portion (optical axis) of the rod lens. As in FIG. 7, the horizontal axis indicates the main scanning pixel number, and the vertical axis indicates the sensor output value (a value obtained by A/D conversion with 10 bits and expressed in decimal notation). A dotted line frame in FIG. 9 is a portion where the output characteristics have changed due to slight adhesion of dust.

Compared to the case where no dust is attached in FIG. As a result, the amplitude of the output characteristic becomes smaller, and at the same time, the period seems to become longer.

From the examples in FIGS. 7 to 9, if we have the optical characteristics (period/amplitude characteristic values due to the rod lens) in the state where no dust adheres as initial information, we can use the white reference plate before the image reading operation. By comparing the information obtained by the reading operation and the initial information (checking the amount of change in the period/amplitude characteristic value due to the rod lens), it is possible to detect whether dust or the like is attached. A dust adhesion detection method based on this method will be referred to as a first dust adhesion detection method.

In order to accurately detect the presence or absence of dust adhesion by the first dust adhesion detection method, the optical characteristics (period and amplitude characteristic values due to the rod lens) in the state where dust is not adhered are appropriate (amplitude is above a certain level). However, even contact image sensor units that have passed the manufacturer's inspection may not be suitable for the first dust adhesion detection method.

For example, in a contact image sensor unit having R, G, and B color channels, the G color channel in the center is positioned approximately on the optical axis of the rod lens, as described above. Since the color channel is separated from the optical axis of the rod lens by the reading resolution (42 μm in the case of 600 DPI), the amount of light received is small and the amplitude tends to be small as a whole. In addition, as described above, the plurality of sensor ICs constituting the photoelectric conversion unit 61 are allowed to vary in layout within a predetermined layout rule. Due to variations, the period/amplitude characteristics due to the rod lens may change to such an extent that they are not suitable for the first dust adhesion detection method. In particular, the R-color and B-color channels far from the center of the optical axis have poor optical characteristics, and the influence of arrangement fluctuations is significant. FIG. 10 shows an example thereof.

FIG. 10 shows the output characteristics of the R color channel. Since the R color channel is separated from the optical axis of the rod lens by a resolution in the width direction, the amplitude is smaller than the G color output characteristic shown in FIG. In addition, in the portion surrounded by the dotted line in the drawing, a periodicity different from the periodicity caused by the rod lens appears. Although not shown, it is obvious that a phenomenon similar to that of the R color can occur in the B color channel, because the B color channel is located at a resolution-separated location in the opposite direction to the R color channel from the optical axis of the rod lens. be.

The present invention provides a determination method (CIS determination process) for determining whether or not the contact image sensor unit has optical characteristics (amplitude characteristics) suitable for the first dust adhesion detection method. This determination method will be described below.

Here, 17 sensor ICs having three channels of R, G, and R colors are arranged in a line and have a resolution of 600 DPI (effective pixels: 5,168 pixels) and a rod lens array. A single-row type contact image sensor unit will be described as an example.

Since the number of effective pixels (5168 pixels) is equally shared among the 17 sensor ICs, the number of pixels per sensor IC is 304 pixels. Also, since the rod lens array has one row and the resolution is 600 DPI (pixel pitch 42 μ), the lens periodicity (corresponding to the diameter) is set to about 9 pixels.

When replacing the contact image sensor unit installed in the image reading apparatus 10 with a new one, the service person replaces the new contact image sensor unit (the contact image sensor unit to be inspected) with the first contact image sensor unit. 1 (or second reading unit), a predetermined operation is performed from the operation display unit 26 to operate the image reading apparatus 10 in the CIS determination mode.

FIG. 11 is a flowchart showing an outline of processing (CIS determination processing) performed by the image reading apparatus 10 in the CIS determination mode. In the CIS determination mode, the image reading device 10 reads the facing white reference plate with the contact image sensor unit to be inspected, and A/D converts the sensor output data at that time to obtain a digital value. It is assumed that a 10-bit (0 to 1023) digital value is output from the A/D converter. Then, the read value (read data) obtained by subtracting the black correction value from the sensor output data, which is a 10-bit digital value, is temporarily stored in the RAM 23 (step S101). Here, read values are primarily stored as an array for each RGB color, R(x), G(x), B(x): x=1 to 5168, where x is the pixel number.

Next, the image reading apparatus 10 partitions the above array for each sensor IC and stores them again (step S102). Assume that the sensor IC numbers are (1) to (17),
Sensor IC (1): R(x), G(x), B(x): x=1 to 304
Sensor IC (2): R(x), G(x), B(x): x=305 to 608
Sensor IC (3): R(x), G(x), B(x): x=609 to 912
Sensor IC (4): R(x), G(x), B(x): x=913 to 1216
Sensor IC (5): R(x), G(x), B(x): x=1217 to 1520
Sensor IC (6): R(x), G(x), B(x): x=1521 to 1824
Sensor IC (7): R(x), G(x), B(x): x=1825 to 2128
Sensor IC (8): R(x), G(x), B(x): x=2129 to 2432
Sensor IC (9): R(x), G(x), B(x): x=2433 to 2736
Sensor IC (10): R(x), G(x), B(x): x=2737~3040
Sensor IC (11): R(x), G(x), B(x): x=3041 to 3344
Sensor IC (12): R(x), G(x), B(x): x=3345 to 3648
Sensor IC (13): R(x), G(x), B(x): x=3649 to 3952
Sensor IC (14): R(x), G(x), B(x): x=3953 to 4256
Sensor IC (15): R(x), G(x), B(x): x=4257 to 4560
Sensor IC (16): R(x), G(x), B(x): x=4561 to 4864
Sensor IC (17): R(x), G(x), B(x): x=4865 to 5168
becomes.

Next, the image reading device 10 obtains an amplitude characteristic value (optical characteristic value) for each sensor IC. Here, the rod lens periodicity (corresponding to the diameter) is set to 9 pixels, and the array of the interval maximum value, the interval minimum value, and (the interval maximum value - the interval minimum value) is obtained with the interval of 9 pixels in the sensor IC (step S103). At this time, since the leading 4 pixels and trailing 4 pixels of the sensor IC are excluded from the array pixels of the interval maximum value and interval minimum value, the array of 304 pixels for each sensor IC becomes an array of 296 pixels. . By calculating (maximum value of section - minimum value of section), the amplitude value in that section can be obtained.

Further, the average value (channel amplitude value (Ave.)) of the amplitude values (maximum value of section - minimum value of section) is obtained for each sensor IC and for each color. Alternatively, the minimum amplitude value (channel amplitude value (Min.)) is obtained for each sensor IC and each color (step S104).

Specifically, the calculations in steps S103 and S104 are performed as follows. The reason why the optical characteristic values (channel amplitude value (Ave.) and (channel amplitude value (Min.)) are obtained for each sensor IC is that deviations in placement within the layout rules occur for each sensor IC.

In the R color channel of sensor IC (1),
The array of interval maxima is Red_Max(x) = Max(x-4, x-3, x-2, x-1, x, x+1, x+2, x+3, x+4); x = 4 to 296
The interval minimum array is Red_Min(x) = Min(x-4, x-3, x-2, x-1, x, x+1, x+2, x+3, x+4); x = 4 to 296
(Maximum value of interval - Minimum value of interval) is (Red_Max(x)-Red_Min(x)); x=4~296
becomes.

An average value of the amplitude values (maximum value of the section - minimum value of the section) is obtained and used as the Red channel amplitude value (Ave.) of the sensor IC (1). Alternatively, the minimum value of this amplitude value is obtained and set as the Red channel amplitude value (Min.) of sensor IC (1).

Similarly, in the G color channel of sensor IC (1),
The array of interval maxima is Green_Max(x)=Max(x-4, x-3, x-2, x-1, x, x+1, x+2, x+3, x+4); x = 4 to 296
The interval minimum array is Green_Min(x) = Min(x-4, x-3, x-2, x-1, x, x+1, x+2, x+3, x+4); x = 4 to 296
(Maximum value of interval - Minimum value of interval) is (Green _Max (x) - Green _Min (x)); x = 4 to 296
becomes.

The average value of these amplitude values is obtained and taken as the Green channel amplitude value (Ave.) of the sensor IC (1). Alternatively, the minimum value of this amplitude value is obtained and set as the Green channel amplitude value (Min.) of the sensor IC (1).

Similarly, in the B color channel of sensor IC (1),
The array of interval maxima is Blue_Max(x)=Max(x-4, x-3, x-2, x-1, x, x+1, x+2, x+3, x+4); x = 4 to 296
The interval minimum array is Blue_Min(x)=Min(x-4, x-3, x-2, x-1, x, x+1, x+2, x+3, x+4); x = 4 to 296
(Maximum value of section - Minimum value of section) is (Blue _Max(x) - Blue _Min(x)); x = 4 to 296
becomes.

The average of these amplitude values is obtained and taken as the Blue channel amplitude value (Ave.) of sensor IC (1). Alternatively, the minimum value of this amplitude value is obtained and set as the Blue channel amplitude value (Min.) of the sensor IC (1).

For the sensor ICs (2) to (17), the same calculation as above is performed to obtain the amplitude characteristic value (optical characteristic value) for each of the R, G, and B channels for each sensor IC. The size of the section is preferably the number of pixels corresponding to the rod lens period (equivalent to the diameter), but is not limited to this. For example, it may be twice the rod lens period.

In addition to the processing of FIG. 11, the results of verifying whether or not dust adhesion can be detected by the first dust adhesion detection method for a large number of contact image sensor units are compared with the above calculation results. As a result of obtaining the first threshold value for determining whether or not the image sensor unit is suitable for the first dust adhesion detection method based on the channel amplitude value (Ave.), the first threshold value is '40'. rice field. Note that the first threshold and the second threshold are set to values according to the measurement system. For example, depending on how many bits of digital value is output from the A/D converter, the reflectance of the white reference plate, light source conditions, circuit parameters (amplifier circuit gain settings) in analog front-end processing, etc. A threshold can be set.

FIG. 12 shows channel amplitude values (Ave.) and channel amplitude values, which are optical characteristic values obtained for each of the R, G, and B channels, for sensor ICs (1) to (17) of a contact image sensor unit to be inspected. It is a list of values (Min.). In this contact image sensor unit, the channel amplitude value (Ave.) in the R color channel of sensor ICs (1) to (3) is less than or equal to '40', which is the first threshold value. In the judgment method based on (Ave.), it is judged that the R color channel of the sensor ICs (1) to (3) is not suitable for the first dust adhesion detection method.

When this contact image sensor unit was verified whether or not dust could be detected by the first dust adhesion detection method, the result was the same as the determination based on the channel amplitude value (Ave.). In FIG. 12, locations where the channel amplitude value (Ave.) is less than or equal to the first threshold are indicated by a gray background color.

13 is a graph of the R color channel amplitude value (Ave.) of each sensor IC in the list of FIG. 12, and FIG. 14 is the G color channel amplitude value of each sensor IC in the list of FIG. Amplitude values (Ave.) are graphed, and FIG. 15 is a graph of B-color channel amplitude values (Ave.) of each sensor IC in the list of FIG. It can be seen that '40', which is the first threshold value, is an appropriate value in determination based on the channel amplitude value (Ave.).

The image reading device 10 calculates the channel amplitude value (Ave.) and the first threshold value (or the channel amplitude value (Min.) and the second threshold value) obtained for each sensor IC of each color of the contact image sensor unit to be inspected. If any one of them is equal to or less than the first threshold value (or the second threshold value) (step S105; Yes), the contact image sensor unit to be inspected is subjected to the first dust adhesion. It is determined that it is not suitable for the detection method (step S106), and this process is terminated.

If the channel amplitude value (Ave.) is greater than the first threshold value (or the channel amplitude value (Min.) is greater than the second threshold value) for all R, G, and B colors of all sensor ICs (step S105; No ), it is determined that the contact image sensor unit to be inspected is suitable for the first dust adhesion detection method (step S106), and the process ends.

Note that the determination based on the channel amplitude value (Ave.) detects objects unsuitable for the first dust adhesion detection method with higher accuracy (up to gray zone) than the determination based on the channel amplitude value (Min.). be able to. Determination based on the channel amplitude value (Min.) detects cases where the first dust attachment detection method has fatally unfavorable optical characteristics.

The determination result is displayed on the operation display section 26 . Further, the contact image sensor unit determined to be suitable for the first dust adhesion detection method is used in the image reading apparatus 10 as the contact image sensor unit 17 whose relative position to the white reference plate is fixed. That is, it is used as the contact image sensor unit 17 mounted on the second reading section. On the other hand, the contact image sensor unit determined as not suitable for the first dust adhesion detection method is used as the contact image sensor unit 18 whose relative position is movable with respect to the white reference plate. That is, it is used as the contact image sensor unit 18 mounted on the first reading section.

Further, the image reading apparatus 10 is determined to be suitable for the first dust adhesion detection method, and the contact image sensor unit 17 mounted on the second reading section is determined to be suitable for the first dust adhesion detection method (first dust adhesion detection method). Attachment detection processing) detects the presence or absence of dust attachment at the time of shading correction. On the other hand, since the contact image sensor unit 18 mounted on the first reading section is not suitable for the first dust adhesion detection method, the second dust adhesion detection method is used to detect dust adhesion. In this manner, the image reading apparatus 10 switches dust adhesion detection processing between the contact image sensor unit 18 mounted on the first reading section and the contact image sensor unit 17 mounted on the second reading section.

An example of a second dust adhesion detection method is shown. The white reference plate is read multiple times while moving relative to the white reference plate. Then, the presence or absence of dust adhesion is detected by comparing the read data with previously registered read data in the case of no dust adhesion. Furthermore, even if the relative positions of the white reference plate and the contact image sensor unit are moved, if dust is still detected at the same position, the dust may have adhered to the incident surface of the contact image sensor unit. determine that there is On the other hand, if dust detected at a certain relative position is no longer detected by moving the relative position between the white reference plate and the contact image sensor unit, it means that the dust is attached to the white reference plate. judge.

When dust adhesion is detected by the first or second dust adhesion detection method, the image reading device 10 corrects the shading correction data of the dust adhesion portion, replaces it with initial data without dust adhesion, or For example, a display requesting the user to clean the location where dust is adhered is displayed. In particular, it is desirable to display a warning when it is detected that dust is attached to the incident surface of the contact image sensor unit.

Next, in order to correct the sensitivity variation of the measurement system and the sensor IC end pixels for each sensor IC, the value d(n) obtained by reading the white reference plate: n is the pixel number, the sensor IC unit A case will be described in which D(n), which is the result of the measurement data correction process in , is obtained, and optical characteristics are determined based on D(n). Here, the moving average is used as the measurement data correction process for each sensor IC. By subjecting the read data to moving average processing that has a low-pass filter effect, sensor output value variations (the flatness of the white reference plate is rough) can be effectively corrected in the inspection and measurement system.

The leading and trailing edges of the sensor IC (the range of 4 to 8 pixels from the leading edge and trailing edge for a 304-pixel sensor IC) serve as joints between the sensor ICs, so sensitivity variations are more likely to occur than near the center. . Further, since the joints of the sensor ICs are arranged with a predetermined distance therebetween in order to achieve a predetermined linearity, there are cases where the sensor ICs are affected by variations in the light receiving sensitivity. With such sensor IC characteristics,
D(n)=(d(n-4)+d(n-3)+d(n-2)+d(n-1)+d(n)+d(n+1)+d(n+ 2) +d(n+3)+d(n+4))÷9
Such moving average processing is performed.

After that, in the same manner as in step S103 and subsequent steps in FIG. 11, an array of the maximum value of the section and the minimum value of the section (the maximum value of the section - the minimum value of the section) is obtained. The average value (channel amplitude value (Ave.)) and minimum value (channel amplitude value (Min.)) of (maximum value - interval minimum value) are calculated, compared with the corresponding threshold value, and detected by the first dust adhesion detection method. determine whether it is suitable. Note that the parameters for the moving average process are preferably set to 9 pixels, which corresponds to the rod lens diameter distance in the rod lens array, but are not limited to this.

Based on the value (D(n)) after moving average processing, the result of obtaining the channel amplitude value (Ave.) for each sensor IC and for each color for the contact image sensor unit to be inspected which is the same as in FIG. 12 is shown in FIG. show. Even with the same measurement system (white reference plate, light source setting, AFE circuit parameters, etc. are the same), the numerical value to be judged becomes smaller due to moving average processing correction, and the threshold value is also corresponding to this. Set small. In this example, the R color channel of sensor ICs (1)-(3) should be detected as non-conforming, so the threshold is set to '7'. In FIG. 16, as in FIG. 12, the background of locations where the channel amplitude value (Ave.) is equal to or less than the threshold is shown in gray.

Note that the process of determining whether or not the contact image sensor unit is suitable for the first dust adhesion detection method may be performed by an inspection device separate from the image reading device 10 . In the image reading apparatus according to the present invention, the contact image sensor unit determined to be suitable for the first dust adhesion detection method is subjected to the second reading method in which the relative position between the white reference plate and the contact image sensor unit 17 is fixed. A contact image sensor unit that is mounted in the unit and determined to be unsuitable for the first dust adhesion detection method is mounted in the first reading unit that has a mechanism in which the contact image sensor unit is movable with respect to the white reference plate. The process of determining whether the first dust adhesion detection method is suitable (CIS determination process) may be performed by the image reading apparatus 10 or may be performed by a separate inspection apparatus.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configurations are not limited to those shown in the embodiments, and modifications and additions may be made without departing from the scope of the present invention. is also included in the present invention.

In the embodiment, the case where the image reading device 10 is a single device was exemplified, but the present invention is a device having the functions of the image reading device 10, for example, the image reading device 10 is provided as a scanner section for reading a document. , a copy function, a printer function, a FAX function, and the like. The CIS determination process may be performed by the main control unit of the multifunction machine.

In the embodiments, an image sensor unit having three channels of R, G, and B has been described as an example. The number of channels is not limited to this.

In the embodiment, the contact image sensor unit to be inspected reads the white reference plate and temporarily stores the sensor output in determining whether or not the first dust adhesion detection method is suitable. is stored in advance in the storage unit 63 of the contact image sensor unit (for example, when the corresponding data is written in the storage unit during the manufacturing process or inspection process of the contact image sensor unit). ), the sensor output value read from the storage unit 63 may be subjected to the processing from step S102 in FIG. 11 to determine whether or not it is suitable for the first dust adhesion detection method.

Alternatively, optical characteristic values (channel amplitude value (Ave.) and channel amplitude value (Min.)) for determining whether or not the first dust adhesion detection method is suitable are stored in the storage unit 63 of the contact image sensor unit. is stored, whether or not the contact image sensor unit is suitable for the first dust adhesion detection method may be determined by comparing the value with a threshold value.

Alternatively, if the determination result as to whether or not the first dust adhesion detection method is suitable is already stored in the storage section 63 of the contact image sensor unit, the image reading apparatus 10 reads out the determination result. , whether or not the contact image sensor unit is suitable for the first dust adhesion detection method.

In the embodiments, as an example of a mechanism in which the contact image sensor unit is movable with respect to the white reference plate, a flatbed type reading unit that reads a document placed on the platen glass was exemplified. For example, the reading unit may be configured to be movable relative to the white reference plate within the area of the white reference plate.

DESCRIPTION OF SYMBOLS 10... Image reading device 11... Platen glass 12... Translucent glass 13... Main body part 14... Document table 15... Paper discharge tray 16... Automatic document conveying part 16a... Feeding roller 16b... Conveying roller 17... Contact type image sensor unit (first 2 installed in the reading unit)
18... Contact image sensor unit (installed in the first reading unit)
19a, 19b... White reference plate 20... Control circuit section 21... CPU
22 ROM
23 RAM
DESCRIPTION OF SYMBOLS 24... I/F part 25... Image processing part 26... Operation display part 30... Housing 32... Transmissive body 40... Irradiation part 42... Light guide 44... Light source 50... Rod lens array 60... Sensor substrate 61... Photoelectric conversion part 63... Storage unit

Claims (3)

a first reading unit having a mechanism for reading an image on the document from the outside of the curved document with a contact image sensor unit and moving the contact image sensor unit with respect to a white reference member;
a second reading unit having a structure in which the contact image sensor unit reads an image on the document from the inside of the curved document, and the contact image sensor unit is fixed to a white reference member;
a first dust adhesion detection unit that detects dust adhesion in the first reading unit;
a second dust adhesion detection unit that detects dust adhesion in the second reading unit;
with
The contact image sensor unit of the second reading section reads read data obtained by reading a white reference member in a dust-free state for each sensor IC and for each color, and scans the rod lens array of the contact image sensor unit . Divided into sections corresponding to the lens cycle, find the difference by subtracting the minimum value from the maximum value in each section, and the average value or minimum value of the difference for each sensor IC and for each color is all greater than or equal to a predetermined threshold. It satisfies the condition of
The contact image sensor unit of the first reading unit does not satisfy the conditions,
The second dust adhesion detection section detects the first read data obtained by reading the white reference member in a state where dust is not adhered by the contact image sensor unit at the lens period of the rod lens array of the contact image sensor unit. By comparing the corresponding periodic change characteristic with the periodic change characteristic of the second read data obtained by reading the white reference member with the contact image sensor unit, the reading time of the second read data is determined. Detect dust adhesion,
The image reading device, wherein the first dust adhesion detection section detects adhesion of dust by a detection method different from that of the second dust adhesion detection section. a collecting unit that collects read data by reading the facing white reference member with the contact image sensor unit;
Obtaining the difference for each section from the read data collected by the collecting unit, and determining whether or not the average value or minimum value of the difference for each sensor IC and for each color is equal to or greater than a predetermined threshold value. a computing unit;
The image reading device according to claim 1, further comprising: 3. The image reading method according to claim 1, wherein in determining the condition, the average value or the minimum value is obtained based on the read data after performing moving average processing in units of the section. Device.

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