JP7209178B2 - Image sensor unit and image reader - Google Patents

Description

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

A contact image sensor unit (CIS: Contact Image Sensor) that is brought into close contact with a document and optically reads the document comprises a photoelectric conversion section in which light receiving elements are arranged in a line in the main scanning direction, and A light source that irradiates light onto a document and a rod lens array that forms an image of the light emitted from the light source and reflected by the document on the light receiving element of the photoelectric conversion section are integrated into one housing. be.

The contact-type color image sensor unit, which reads an original for each of the R (red), G (green), and B (blue) color components, reduces sensitivity unevenness in the main scanning direction and suppresses the occurrence of color unevenness. In order to do so, it is required that the variation in sensitivity between R, G, and B is small.

Patent Document 1 below describes a light source switching type image that reads an original in color by providing light sources of R, G, and B colors, and switching the colors of the light sources for one line of photoelectric conversion units in a time division manner. Disclosed is an inspection method and an inspection apparatus capable of easily and accurately evaluating characteristics of variations in sensitivity among R, G, and B for a sensor unit. In this inspection method, the optical output V1 of the image sensor unit when irradiated with light of a first light source (for example, R color) and the light output of the image sensor unit when irradiated with light of a second light source (for example, G color) By calculating the ratio to the output V2, the color balance is inspected by removing the influence of the light amount distribution irradiated to the photoelectric conversion unit.

JP-A-2000-349956

In addition to the above-described light source switching type, the color image sensor unit has line channels composed of light receiving elements for one line in the main scanning direction for each of the R, G, and B color components, which are arranged in parallel and adjacent to each other. There is a so-called color filter system in which reflected light from a document is imaged on a light receiving element of each line channel through a color filter of a color component assigned to the line channel.

Also in this type of color image sensor unit, in addition to suppressing the variation in sensitivity in the main scanning direction, it is required that the variation in sensitivity between R, G, and B is small. In this system, since a plurality of line channels are adjacent in parallel, variations in sensitivity between color components occur due to inherent causes (such as twisting of the rod lens array and the photoelectric conversion section) that are not found in the light source switching type.

That is, as shown in FIG. 19, the line channels of R, G, and B are arranged in this order, and if the light receiving element of G color is on the center of the optical axis in the width direction of the rod lens array, the adjacent R color channels and the light receiving elements of the B color line channels are positioned a little away in the width direction from the center of the optical axis of the rod lens array. Since the rod lens array has a mountain-like light distribution in the width direction with the center of the optical axis as the apex on the imaging plane, the R and B light receiving elements located slightly away from the center of the optical axis receive light The amount of received light is smaller than that of the G-color light-receiving element on the center of the axis. Thus, the amount of light received by the light receiving element of each color decreases as the distance between the light receiving element and the center of the optical axis of the rod lens array increases.

Here, if the main scanning direction of the rod lens array and the main scanning direction of the R, G, B line channels are completely parallel as shown in FIG. The distance from the center of the optical axis of the rod raise array is the same for any pixel in the main scanning direction, and the color balance is constant for any pixel in the main scanning direction.

However, if there is a twist in the main scanning direction of the rod lens array and the main scanning direction of the R, G, B line channels as shown in FIG. Since the distance S1 between the optical axis center of the rod lens array and the R color light receiving element is greater than the distance S2 between the optical axis center of the rod lens array and the B color light receiving element, B color output value>R color output value, At the other end Eb, the distance S4 between the optical axis center of the rod lens array and the B color light receiving element is greater than the distance S3 between the rod lens array optical axis center and the R color light receiving element. B color output value. Thus, if there is a twist in the main scanning direction of the rod lens array and the main scanning direction of the R, G, B line channels, the color balance of R, G, B becomes uneven depending on the pixel position in the main scanning direction.

Similarly, in the light source, light from an LED light source or the like is incident on the end portion of a light guide long in the main scanning direction, and the original is irradiated with uniform light in the main scanning direction through the light guide. Body twist also affects color balance non-uniformity.

Therefore, in the manufacturing and assembly adjustment of this type of contact color image sensor unit, sensitivity variations in the main scanning direction as well as non-uniform color balance due to twisting of the rod lens array and photoelectric conversion section and twisting of the light guide are allowed. It is necessary to keep it within the range, and an appropriate assembly method and inspection method corresponding to it are desired.

In the case of the light source switching type disclosed in Patent Document 1, since the photoelectric conversion unit is composed of one line channel, unevenness in color balance due to the twist between the rod lens array and the photoelectric conversion unit as described above may occur. Such problems do not occur.

Also, even if the image sensor unit has passed the inspection at the time of manufacturing, it must be attached to the image reading device so that the positional relationship with the document is appropriate and maintained in that state. can't get

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems. An object of the present invention is to provide an image sensor unit and an image reading device having the same, which can easily adjust the mounting position of the image sensor unit.

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

[1] A sensor substrate provided with a photoelectric conversion unit in which a first line channel, a second line channel, and a third line channel, which are each made up of light receiving elements for one line, are adjacent in parallel in this order;
an irradiation unit that irradiates a document surface with white light;
a rod lens array that guides the light emitted from the irradiation unit and reflected by the document surface to the photoelectric conversion unit;
a storage unit, a housing, and
has
The irradiation unit, the rod lens array, and the sensor substrate irradiate white light from the irradiation unit, which emits a prescribed amount of light on a white reference plate arranged at a predetermined relative position with respect to the rod lens array. fixed to the housing at a position where the output values of the first line channel, the second line channel, and the third line channel of the photoelectric conversion unit satisfy predetermined acceptance criteria in the state of the photoelectric conversion unit;
The image sensor unit, wherein the storage section stores adjustment information based on the output value of the photoelectric conversion section when fixed.

In the above invention, the assembled image sensor unit stores adjustment information based on the output value of the photoelectric conversion unit when it is fixed at a position that satisfies the acceptance criteria in the storage unit. The image reading device can use the adjustment information stored in the storage unit for adjusting the attachment position of the image sensor unit and for shading correction.

[2] The image sensor unit according to [1], wherein the sensor substrate is fixed to the housing to which the irradiation unit and the rod lens array have been attached at a position satisfying the acceptance criteria.

In the above invention, the sensor substrate is adjusted and attached to the housing to which the irradiation unit and the rod lens array have already been attached so as to satisfy the acceptance criteria.

[3] The image sensor unit according to [1] or [2], wherein the adjustment information includes an output value for each pixel of the first line channel, second line channel, and third line channel.

In the above invention, the output value itself of the photoelectric conversion unit when the acceptance criteria are satisfied is stored as the adjustment information.

[4] The acceptance criteria are: (output value of the first line channel - output value of the second line channel), the maximum value of the linear first-order approximation straight line is Amax, the minimum value is Amin, and the output value of the third line channel - the output value of the second line channel), where the maximum value of the linear first-order approximation straight line is Bmax and the minimum value is Bmin, the value of (maximum value Amax - minimum value Bmin) and (maximum value Bmax - minimum value Amin ) are both less than or equal to a predetermined value,
The image sensor unit according to any one of [1] to [3], characterized by:

In the above invention, the sensitivity non-uniformity in the main scanning direction (line direction) is the difference between the linear first-order approximation straight line of (1st ch output - 2nd ch output) and the linear first-order approximation straight line of (3rd ch - 2nd ch output) , and whether or not the required characteristics are satisfied can be determined based on the maximum and minimum range widths of these straight lines.

[5] The adjustment information includes a linear first-order approximation straight line of (output value of the first line channel-output value of the second line channel) and (output value of the third line channel-output value of the second line channel). The image sensor unit according to any one of [1] to [4], including the pixel position of the intersection of the linear first-order approximation straight lines.

In the above invention, the intersection point is the pixel position of the balanced pixel where (1st ch output - 2nd ch output) is equal to (3rd ch - 2nd ch output).

[6] The adjustment information includes the maximum value Amax, minimum value Amin, (output value of the third line channel-th The image sensor unit according to [5], further comprising a maximum value Bmax and a minimum value Bmin of a linear first-order approximation straight line of (2 line channel output values).

[7] An image reading device equipped with the image sensor unit according to any one of [1] to [6].

[8] Measure the output values of the first line channel, the second line channel, and the third line channel while irradiating the white reference plate of the device with the white light emitted from the irradiation unit emitted at the specified light amount. a measuring unit that
a correction information generation unit that generates correction information for the mounting position of the image sensor unit based on the measurement value obtained by the measurement and the adjustment information stored in the storage unit;
The image reading device according to [7], characterized by comprising:

In the above invention, the appropriateness of the mounting position of the image sensor unit is determined by comparing the measurement value obtained when reading the white reference plate under the same lighting conditions as during manufacturing and assembly adjustment and the adjustment information stored in the storage unit. and generate correction information for the mounting position.

[9] Based on the adjustment information stored in the storage unit, the correction information generation unit generates a first-order linear approximation straight line of (output value of first line channel−output value of second line channel), Acquiring the pixel position of the intersection of the linear first-order approximation straight line of (the output value of the third line channel - the output value of the second line channel), and obtaining the pixel position of the intersection based on the measured value of the measuring unit; The image reading apparatus according to [8], wherein correction information is generated that indicates which end position of the image sensor unit in the line direction should be corrected from the comparison of these pixel positions.

In the above invention, the pixel positions of the pixels whose output values match each other are obtained from the adjustment information in the storage section and the measured values obtained by the image reading device, and the correction information is generated by comparing these pixel positions.

According to the image sensor unit and the image reading apparatus having the same according to the present invention, non-uniformity of color balance and non-uniformity of sensitivity in the main scanning direction can be easily adjusted within an allowable range during manufacturing and assembly adjustment. It is possible to easily adjust the mounting position to the image reading device.

1 is a schematic configuration diagram showing an example of an image reading device provided with an image sensor unit according to an embodiment of the invention; FIG. 2 is a block diagram showing the electrical configuration of the image reading device; FIG. 2 is a cross-sectional view showing a schematic configuration of an image sensor unit; FIG. 3 is a perspective view showing the internal configuration of the image sensor unit; FIG. FIG. 4 is a diagram showing light source characteristics (illuminance distribution) of an irradiation section of the image sensor unit; FIG. 4 is a diagram showing wiring connections and the like between the sensor substrate of the image sensor unit and the light source of the irradiating section; FIG. 2 is an enlarged view of a photoelectric conversion unit on a sensor substrate and a part thereof; It is a figure which shows the optical characteristic of a rod lens array. FIG. 10 is a diagram showing an example of a graph showing the illuminance ratio of each pixel in one line in the main scanning direction for each of R, G, and B colors when a white reference plate is read by an image sensor unit having a problem of non-uniform sensitivity; FIG. 10 is a diagram showing an example of a graph showing the illuminance ratio of each pixel in one line in the main scanning direction for each of R, G, and B colors when a white reference plate is read by an image sensor unit with good sensitivity non-uniformity; 4 is a graph (SAMPLE001, 002) showing RGB output values for each pixel position in an image sensor unit that satisfies required characteristics regarding sensitivity non-uniformity; 4 is a graph (SAMPLE003, 004) showing RGB output values for each pixel position in an image sensor unit that does not satisfy required characteristics regarding sensitivity non-uniformity; 4 is a graph (SAMPLE005, 006) showing RGB output values for each pixel position in an image sensor unit that does not satisfy required characteristics regarding sensitivity non-uniformity; FIG. 12 is a graph obtained by calculating (Rch output−Gch output) and (Bch output−Gch output) for SAMPLE001 and 002 shown in FIG. 11; 13 is a graph obtained by calculating (Rch output−Gch output) and (Bch output−Gch output) for SAMPLE003 and 004 shown in FIG. 12. FIG. 14 is a graph obtained by calculating (Rch output−Gch output) and (Bch output−Gch output) for SAMPLE005 and 006 shown in FIG. 13. FIG. FIG. 4 is a flow chart showing the flow of processing in the adjustment process; It is a flowchart figure which shows the flow of the process in an inspection process. FIG. 10 is a diagram showing a comparison between the case where the rod lens array and each line channel of RGB on the sensor substrate are parallel and the case where they are twisted.

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 equipped with an image sensor unit according to an embodiment of the invention. The image reading apparatus 10 has a rectangular thin box-like main body 13 on which a platen glass 11 and a translucent glass 12 serving as a reading position during flow reading are fitted. An automatic document feeder 16 that feeds out the documents one by one and conveys them to the discharge tray 15 via the reading position (the surface of the translucent glass 12) on the upper surface of the main body 13, an image sensor unit 17 that reads the back side of the document at the reading position, It has an image sensor unit 18 that reads the surface of the document at the reading position, and a paper discharge tray 15 that also serves as an openable platen cover that covers 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 image sensor unit 17 reads one line at a time in the main scanning direction (in FIG. 1, the direction perpendicular to the paper surface). The image reading apparatus 10 can two-dimensionally read a document by repeating the reading operation for each line while conveying the document in the sub-scanning direction perpendicular to the main scanning direction.

The image sensor unit 17 is disposed in close proximity to the surface of the translucent glass 12, and a white reference plate 19a having a predetermined reflectance is placed at a position facing the image sensor unit 17 with the translucent glass 12 interposed therebetween. It is provided.

Like the image sensor unit 17, the image sensor unit 18 performs line-by-line reading in the main scanning direction (the direction perpendicular to the plane of FIG. 1). The image sensor unit 18 is held by a moving mechanism (not shown), and faces the rear surface of the translucent glass 12 and is located at a home position (the position indicated by the solid line in FIG. 1) adjacent to the downstream side of the first 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 19b for the image sensor unit 18 is provided at a position facing the second image sensor unit 18 at the home position with the translucent glass 12 interposed therebetween.

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 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 image sensor units 17 and 18 as well as the drive section of the automatic document feed section 16, the drive section for reciprocating the 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 processing for adjusting the attachment position of the image sensor unit, which will be described later. 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 corrections such as shading correction and color correction and image processing on data output from the image sensor units 17 and 18 .

When the image reading apparatus 10 reads a document placed on the document table 14, the document is conveyed by the automatic document feeder 16 with the image sensor unit 18 positioned at the home position. By repeating reading in units of lines by the image sensor units 17 and 18 when passing through the reading position, the front and back sides of the document are two-dimensionally read.

When reading a document placed on the platen glass 11 , the image sensor unit 18 is moved along the back surface of the platen glass 11 and the image sensor unit 18 repeats reading line by line. can be read to

The image sensor unit 17 and the image sensor unit 18 have basically the same configuration, and regarding the image sensor unit, the image sensor unit 17 will be described as an example.

FIG. 3 is a cross-sectional view (a cross section perpendicular to the main scanning direction) showing a schematic configuration of the image sensor unit 17, and FIG. 4 is a perspective view showing the inside of the image sensor unit 17. As shown in FIG. The 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 image sensor unit 17 sets a predetermined range centered on the optical axis of the rod lens array 50 as a reading range, and the irradiation unit 40 irradiates a reading range of one line in the main scanning direction with uniform light. 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 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. 32 are fitted. The housing 30 is made of, for example, a highly rigid metal such as aluminum.

The irradiation unit 40 irradiates the reading range with uniform light in the main scanning direction 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.

The irradiation unit 40 has light source characteristics (illuminance distribution) as shown in FIG. 5 in the sub-scanning direction (width direction) in the reading range. Ideally, the illuminance should be uniform within the reading range in the width direction centered on the optical axis of the rod lens array 50. distribution. Depending on the fixing method of the light guide 42 (fixing accuracy of a member for holding and fixing the light guide 42 to the housing 30, twisting of the light guide 42, etc.), the light source characteristics shown in FIG. 5 may not be achieved.

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 an analog signal output from the photoelectric conversion unit 61 into a digital signal, etc., a storage unit (nonvolatile memory) 63 that stores later-described adjustment information based on the output value of the photoelectric conversion unit, and the like. It is an attached electrical board.

Since the drive circuit for controlling the lighting of the light source 44 is mounted on the sensor substrate 60, the light source 44 (LED substrate 44a) of the irradiation unit 40 and the sensor substrate 60 are wired and connected in the configuration shown in FIG. there is A support wall 45 in the drawing is a part that connects the light source 44 to the light guide 42 and serves to exclude light other than the light emitted by the light source 44 from entering the end portion of the light guide 42 . The light guide 42 distributes the light input from the light source 44 to the document surface as a linear light source.

FIG. 7 is an enlarged view of the photoelectric conversion section 61 on the sensor substrate 60 and a part thereof. The photoelectric conversion unit 61 has n−1 line channels (first line channel), n line channels (second line channel), n+1 line channels (n+1 line channels) in which light receiving elements corresponding to the number of pixels for one line are linearly arranged. 3rd line channel) are adjacent in parallel in this order from the upstream side of the document feed. The n−1 line channel (first line channel) is responsible for R color, the n line channel (second line channel) is responsible for G color, and the n+1 line channel (third line channel) is responsible for B color. A color filter is provided in front of the light receiving surface.

Ideally, the G-color line channel (Gch) is positioned at the center of the optical axis of the rod lens array 50, and the R-color and B-color line channels (Rch, Bch) are equally spaced in front of and behind it (with a resolution of 600 DPI). 42 μm intervals). Based on such an optical arrangement, in assembling the image sensor unit 17, the output values of Rch, Gch, and Bch are adjusted aiming at a relationship of Gch<Rch=Bch. Note that the photoelectric conversion section 61 is actually configured by arranging a plurality of sub-photoelectric conversion sections in charge of a partial range in the main scanning direction in the main scanning direction.

8 shows the optical characteristics of the rod lens array 50. FIG. In FIG. 8, the object plane is the document plane (read object), and the imaging plane is the position where the light reflected by the object plane converges through the rod lens array 50 and forms an image. In the rod lens array 50, the focal distance L1 between the object surface and the lens surface on the object surface side is equal to the focal distance L2 between the imaging surface and the lens surface on the imaging surface side.

The portion corresponding to the amount of light on the imaging plane forms a mountain-like shape centering on the optical axis in the sub-scanning direction (the Y direction in FIG. 8). In the main scanning direction (the X direction in FIG. 8), since the rod lens array 50 is configured by arranging a large number of rod lenses in the main scanning direction, a wavy shape having a period equal to the arrangement interval of the rod lenses in the main scanning direction. distribution.

In the rod lens array 50, the reflected light from the original forms an image correctly on the light receiving surface when the distance L1 and the distance L2 are equal. Therefore, the distance L1 slightly changes as the position of the document slightly changes due to the transport. On the other hand, the distance L2 between the light receiving surface of the light receiving element and the lens surface on the side of the light receiving element is fixed and does not change when the sensor substrate 60 and the rod lens array 50 are fixed to the housing 30 . Therefore, uniformity in the main scanning direction between the sensor substrate 60 and the rod lens array 50, which are fixed during manufacturing and assembly, leads to an improvement in non-uniform sensitivity in the main scanning direction.

Next, non-uniform sensitivity required for the image sensor unit 17 and adjustment of the non-uniform sensitivity during manufacturing and assembly will be described.

<Sensitivity non-uniformity based on lighting system members>
9 and 10 are graphs showing the illuminance ratio of each pixel in one line in the main scanning direction for each color of R, G, and B when the image sensor unit 17 reads the white reference plate. The horizontal axis is the pixel number in the main scanning direction, and the vertical axis is the illuminance ratio. The illuminance ratio is the ratio of the light emitted from the light guide 42 and the light reflected by the white reference plate. A suitable adjustment value for the fixed position of the white reference plate is around 96% of the illumination ratio, and since the document reading surface is closer to the image sensor unit 17 than the white reference plate, the illumination ratio on the document reading surface is 98 to 99%. (less than 100%).
9 and 10 show the characteristics of the image sensor unit, which differs only in the light guide 42 among the constituent parts of the image sensor unit 17, and the other parts such as the rod lens array 50 and the sensor substrate 60 are the same.

In the contact image sensor unit 17, in which RGB color filters are provided on the photoelectric conversion section 61 side of the sensor substrate 60, the illumination color characteristics are such that the same color information can be obtained at any pixel position. Uniformity of chromaticity and spectral wavelength is required over the entire range. To minimize this non-uniformity in chromaticity characteristics, R , G, and B are required to fall within a certain range.

In the graph shown in FIG. 9, the illumination in the main scanning direction is uneven, and the sensitivity non-uniformity in the main scanning direction is poor. The cause is the optical characteristics of the light guide 42 (uniformity of the amount of light in the effective reading width) and the fixing method of the light guide 42 . FIG. 10 is a graph showing measurement results of good products in which these problems have been resolved.

The light guides shown in FIG. 10, which can be regarded as good products, can be sorted out by judging the characteristics (uniformity of light quantity) as individual components before assembling them as an image sensor unit.

However, even if a light guide that has been determined as a non-defective product by sorting is used, it can be assembled as a non-defective product as shown in FIG. Therefore, it takes a long time to adjust the image sensor unit 17 during manufacture and assembly. Therefore, it is difficult to realize a process for mass-producing contact image sensor units with good sensitivity non-uniformity and uniform characteristics in a short period of time.

11 to 13 show examples of mounting adjustment information for the sensor substrate 60 used in the conventional mass production process. The vertical axis in the graph of each figure represents the output of the photoelectric conversion section 61 when the white reference plate is irradiated with a predetermined amount of light from the light guide member 42 of the image sensor unit 17 and the reflected light is received, which is converted into a digital signal. The horizontal axis is the pixel number in the main scanning direction. A gray background region sandwiched between a pair of upper and lower horizontal dashed lines indicates the allowable range of sensitivity non-uniformity. Graphs showing the relationship between the pixel number and the output value of each pixel for each color shown in FIGS. 11 to 13 are referred to as output value graphs.

SAMPLE001 and 002 shown in FIG. 11 are measurement results of an image sensor unit that satisfies the required non-uniform sensitivity characteristics required to acquire high-definition color information. SAMPLE003 to 006 shown in FIGS. 12 and 13 are measurement results of an image sensor unit that does not satisfy the required characteristics regarding sensitivity non-uniformity due to variations in the light guide and misalignment of the sensor substrate 60 during assembly.

In SAMPLE003, Bch has the worst non-uniformity of sensitivity, which is 45.4%. Non-uniform sensitivity is defined as the maximum variation in the output voltage (V) of each pixel with respect to the average output voltage (Vave) of each pixel when the white reference plate is irradiated with 50% of the uniform light that saturates the sensor output. sex (%). The formula is as follows.
(MAX｜V－Vave｜) ÷ Vave × 100 (%)
|V-Vave| indicates the absolute value of (V-Vave). Here, the permissible value of sensitivity non-uniformity (%) is set to 40%. In FIGS. 12 and 13, the upper right of each graph shows the channels and their values in which the non-uniformity of sensitivity exceeds the allowable value.

Even if a non-defective light guide that has been selected as described above is used, the non-uniformity in sensitivity can be caused by the fixing method of the light guide (fixing accuracy of the member that holds and fixes the light guide 42 to the housing 30, This occurs due to the twist of the light guide 42, etc.) and the mounting state of the sensor substrate.

Of these factors, those caused by the fixing accuracy of the members that hold and fix the light guide can be determined based on the output value graphs shown in FIGS. That is, since the position where the light guide is held by the member that holds and fixes the light guide can be specified from the dimensions of the mechanism design, it can be easily determined by checking the output characteristics around the corresponding pixel position. can be done. For example, in SAMPLE004 shown in FIG. 12 and SAMPLE005 shown in FIG. 13, there is a change in the output characteristics at a specific point surrounded by a dashed line that can be identified from the dimensions of the mechanism design. It can be seen that this is due to the fixing accuracy of the member to be fixed.

On the other hand, SAMPLE003, SAMPLE004 shown in FIG. 12, and SAMPLE006 shown in FIG. With respect to such sensitivity non-uniformity abnormality, the pixel position where it occurs cannot be specified from the mechanical design dimensions, etc., and it cannot be determined directly from the output value graphs shown in FIGS. It should be noted that in the installation and adjustment work of the sensor substrate 60 in the assembly of the image sensor unit, if it is possible to quickly determine which of the light guide body and the sensor substrate 60 is the main cause of the sensitivity non-uniformity due to twisting, etc. It leads to realization of mass production.

Therefore, in the present invention, the calculation results of (Rch output-Gch output) and (Bch output-Gch output) are obtained from the data of the output value graphs shown in FIGS. 14 to 16 are graphs obtained by calculating (Rch output-Gch output) and (Bch output-Gch output) for SAMPLE001 to 006 shown in FIGS. 11 to 13. FIG. Graphs of the type shown in FIGS. 14-16 shall be referred to as difference graphs. As described above, the sensor output values have the relationships of Gch<Rch and Gch<Bch.

The difference graph reveals the following.

(1) It is possible to specify RGB balanced pixels (origin pixels of sensitivity non-uniformity) of the adjusted contact image sensor unit. Specifically, a pixel where the value of (Rch output-Gch output) and the value of (Bch output-Gch output) are equal is the RGB balance pixel (origin pixel of non-uniform sensitivity), and (Rch output-Gch The pixel at the intersection of the approximate straight line (RG approximate straight line) of the graph of (output) and the approximate straight line (BG approximate straight line) of the (Bch output-Gch output) graph is the RGB balance pixel.

(2) The sensitivity nonuniformity in the main scanning direction is the difference between the approximate straight line (RG approximate straight line) of the (Rch output - Gch output) graph and the approximate straight line (BG approximate straight line) of the (Bch output - Gch output) graph. , and whether or not the required characteristics are satisfied can be determined based on the maximum/minimum range width of the straight line.

(3) Image sensor unit as the final adjustment result data (adjustment information) at the time of assembling the origin pixel of sensitivity non-uniformity and the approximate straight line graph data of (Rch output - Gch output) and (Bch output - Gch output) of the image sensor unit 17 in the image reading device 10 by comparing the measurement result obtained by performing the same measurement with the image reading device 10 and the data stored in the storage part. It is possible to determine whether the mounting position is good or bad, assist position adjustment, and perform pre-reading processing (shading processing) in consideration of the comparison result, thereby realizing high-definition reading of color originals.

The reason why the RG approximation straight line and the BG approximation straight line always intersect is as follows. The sensor substrate 60 is arranged so that Gch is the center position of the optical axis of the rod lens array 50, and Rch and Bch are arranged symmetrically in front of and behind it. , and the main scanning direction of the photoelectric conversion unit 61 are almost never completely parallel, and a slight twist (inclination) occurs. Therefore, for example, if there is a twist such that Rch is closer to the optical axis center of the rod lens array 50 than Bch on the first pixel side, Bch is closer to the optical axis center of the rod lens array 50 than Rch on the final pixel side. (See FIG. 19(b)).

On the other hand, as shown in FIGS. 8 and 19(b), the rod lens array 50 exhibits a mountain-shaped light amount distribution with the top of the optical axis center in the width direction (Y direction in FIG. 8). Regarding the positional relationship with the sensor substrate 60, for example, Rch is closer to the optical axis center of the rod lens array 50 than Bch on the first pixel side, and Bch is closer to the optical axis center of the rod lens array 50 than Rch on the final pixel side. If there is a twist in the approaching direction, Rch output>Bch output on the first pixel side, and Rch output<Bch output on the final pixel side. Therefore, (Rch output-Gch output)>(Bch output-Gch output) on the first pixel side, and (Rch output-Gch output)<(Bch output-Gch output) on the final pixel side. An RGB balanced pixel (intersection point) where (Rch output-Gch output)=(Bch output-Gch output) always exists somewhere between the pixels.

14 to 16 respectively show a graph of (Rch output-Gch output) and a graph of (Bch output-Gch output). The slopes of the (Rch output-Gch output) graph and the (Bch output-Gch output) graph are always opposite directions as described above, and at some pixel position between the first pixel and the last pixel (Rch There always exists an intersection (RGB balanced pixel) where (output-Gch output)=(Bch output-Gch output). This is the same for the graphs of the linear first-order approximation straight line (RG approximation straight line) of (Rch output-Gch output) and the linear first-order approximation straight line (BG approximation straight line) of (Bch output-Gch output).

Next, the flow of the adjustment process when manufacturing and assembling the image sensor unit 17 will be described. The adjustment step is the final step of attaching, adjusting, and fixing the sensor substrate 60 to the housing 30 to which the irradiation unit 40 (the light guide 42 and the light source 44) and the rod lens array 50 have already been attached.

FIG. 17 is a flow chart showing the processing procedure of the adjustment process. In the adjustment process, first, the housing 30, to which the irradiation unit 40 (the light guide 42 and the light source 44) and the rod lens array 50 are already attached, is placed on the adjustment table of the inspection system so as to face the surface of the transmitting body 32. It is fixed so that it is parallel to the white reference plate and the distance between them is a predetermined distance (step S101). Next, the sensor substrate 60 is temporarily fixed to the housing 30 at a position symmetrical to the white reference plate with the rod lens array 50 interposed therebetween (step S102).

In the temporarily fixed state, the light source 44 is turned on with a predetermined amount of light, and the output signals of the R, G, and B channels are captured and stored in the memory device of the inspection system (step S103). The inspection system includes the above-described adjustment table, information processing section, display section, operation section, and the like. The information processing unit includes the above-described memory device and CPU, and is used to drive the image sensor unit to be assembled and adjusted, capture output values, perform various calculations on the captured output values, store adjustment information in the storage unit 63, and display unit. to control the display, etc.

The information processing section of the inspection system performs arithmetic processing on the output signals of the R, G, and B channels stored in the memory device based on a predetermined inspection program to obtain output values as shown in FIGS. Graph array data (array of pixel numbers and R, G, and B output values: R(n), G(n), B(n), n=pixel number) is generated (step S104).

Using the data of the output value graph generated in step S104, the information processing unit uses the previously known light guide member fixing member positions (fixed positions n*, n**, . By comparison, it is determined whether or not there is a decrease in output (one of the acceptance criteria) (step S105).

If the determination confirms that the predetermined value has decreased (step S106; Yes), the information processing section notifies the light guide member of abnormality (step S107), and terminates the inspection.

In the case of non-defective product determination (step S106; No), the information processing unit of the inspection system starts determination processing based on a difference graph as shown in FIG. Specifically, approximate linear arrays of (Rch output-Gch output) and (Bch output-Gch output) are generated (step S108).

In the case of the rod lens array 50, a wave-like output fluctuation occurs in the output signal in the main scanning direction corresponding to the lens array cycle. The results of moving average processing are used as array data (the graphs in each figure are obtained by performing moving average processing in 26-pixel intervals).

The information processing unit of the inspection system obtains a linear first-order approximation straight line (RG approximation straight line ) Calculate the maximum value Amax and minimum value Amin of the data, and calculate the maximum value Bmax and minimum value Bmin of the (Bch output-Gch output) linear first-order approximation straight line (BG approximation straight line) data (step S109). . Then, it is determined whether or not both the maximum value Amax−minimum value Bmin and the maximum value Bmax−minimum value Amin are equal to or less than a predetermined threshold value (one of the acceptance criteria) (step S110).

As described above, the slopes of the RG approximation straight line and the BG approximation straight line are always opposite to each other. and the pixel with the maximum value Bmax of the BG approximate line and the pixel with the minimum value Amin of the RG approximate line are also the same pixel (the other pixel among the first pixel and the last pixel). . Since the RG approximation straight line and the BG approximation straight line have opposite slopes and always have an intersection at an intermediate pixel position, the pixel with the most uneven color balance on the first pixel side of the intersection is the first pixel. The last pixel is the pixel with the most uneven color balance on the last pixel side. Therefore, if the values of (maximum value Amax−minimum value Bmin) and (maximum value Bmax−minimum value Amin), which indicate non-uniformity of RGB balance in pixels at the edge, are both equal to or less than a predetermined threshold, the main It can be confirmed that the non-uniformity of the RGB output values is within the threshold value at any pixel position in the scanning direction.

Therefore, if either one of (maximum value Amax−minimum value Bmin) and (maximum value Bmax−minimum value Amin) is not equal to or less than the threshold value (step S110; No), the information processing unit of the inspection system notifies that effect. After the operator is notified and the operator completes the fine adjustment of the temporarily fixed position of the sensor substrate 60 (step S111), the process returns to step S103 to continue the process.

When both (maximum value Amax−minimum value Bmin) and (maximum value Bmax−minimum value Amin) fall below the threshold value (step S110; Yes), the information processing unit of the inspection system notifies the operator of the completion of adjustment. , to fix the sensor substrate 60 to the housing 30 (step S112). Then, the information processing unit of the inspection system stores the data of the linear first-order approximation straight line (RG approximation straight line) of (Rch output-Gch output) when fixed (when adjustment is completed), the maximum value Amax, the minimum value Amin, (Bch output-Gch output) data of linear first-order approximation straight line (BG approximation straight line), maximum value Bmax, minimum value Bmin, pixel number of intersection of RG approximation straight line and BG approximation straight line, etc. are used as adjustment information. The data is stored in the storage unit 63 (step S113), and the adjustment process ends.

Next, an inspection and adjustment process for the mounting position of the image sensor unit 17 in the image reading apparatus 10 on which the image sensor unit 17 manufactured and adjusted as described above is mounted will be described.

When the image sensor unit 17 is incorporated in the image reading apparatus 10 or the like shown in FIG. The distance from the image sensor unit 17 is adjusted and fixed by a spacer member as required. Although the approximate position is set by the mechanical design, the above distance is slightly different due to the cross-variation of the part accuracy. This slight variation affects the resolving power (MTF (Modulation Transfer Function)) when reading a document. In the replacement work when it occurs), etc., the inspection and adjustment process of the mounting position is carried out.

At this time, in the present invention, the adjustment information stored in the storage section 63 in the image sensor unit 17 is used at the time of assembly manufacturing. That is, the rod lens array 50 employed in the image sensor unit 17 has a one-to-one relationship between the focal distances on both lens surfaces, as described with reference to FIG. In addition, regardless of the state of attachment to the image reading device 10, the positional relationship between the rod lens array 50 and the sensor substrate 60 inside the image sensor unit 17 remains the same as when it was fixed in the adjustment process during manufacturing.

For this reason, in the inspection adjustment process on the image reading device 10 side, the white reference plate is read under the same illumination conditions (light source adjustment values, AFE calculation parameters, etc.) as in the adjustment process at the time of manufacturing, and the data of the RG approximate straight line and the BG approximate straight line are obtained. The parallelism between the white reference plate surface and the image sensor unit 17 in the image reading device 10 can be determined by comparing the data of the RG approximate straight line and the BG approximate straight line stored in the storage unit 63 in the adjustment process at the time of manufacturing. It can be appreciated how the relationships have changed from their parallel relationships when the sensor substrate 60 was fixed during the alignment process during manufacturing. Therefore, in the inspection and adjustment process performed by the image reading apparatus 10, it is determined whether or not the mounting position of the image sensor unit 17 needs to be finely adjusted based on the above comparison. Notify the operator of the adjustment method. If the adjustment process during manufacturing and assembly of the image sensor unit 17 differs from the reflectance characteristics of the white reference plate in the mounted image reader, the Gain adjustment value of the AFE calculation parameter is changed and the image sensor unit In some cases, the AFE parameters are corrected so that the stored data in 17 can be utilized.

FIG. 18 shows the flow of the inspection adjustment process performed by the image reading apparatus 10. As shown in FIG. After initializing the system by turning on the power (step S201), the CPU 21 of the image reading device 10 reads adjustment information from the storage section 63 of the image sensor unit 17 (step S202). This adjustment information is stored in the storage unit 63 in step S113 of FIG.

Next, the CPU 21 of the image reading apparatus 10 sets the light source adjustment values and AFE calculation parameters in the sensor board 60 of the image sensor unit 17 so that the illumination conditions are the same as those in the manufacturing adjustment process (step S203). Then, the light source 44 of the irradiation unit 40 is turned on to read the white reference plate, and the output signal values of the R, G, and B channels at the time of reading are temporarily stored in the RAM 23 (step S204).

Then, the CPU 21 of the image reader 10 generates approximate linear arrays of (Rch output-Gch output) and (Bch output-Gch output) based on the data temporarily stored in the RAM 23 in step S204 (step S205). Similar to the adjustment process at the time of manufacturing, approximate linear arrays of (Rch output-Gch output) and (Bch output-Gch output) are created based on moving averaged data.

Next, the CPU 21 of the image reading apparatus 10 calculates the maximum value Cmax and the minimum value Cmin of the linear first-order approximation straight line (RG approximation straight line) data of (Rch output-Gch output) from the approximate straight line array created in step S205. At the same time, the maximum value Dmax and the minimum value Dmin of the data of the linear first-order approximation straight line (BG approximation straight line) of (Bch output-Gch output) are calculated, and the pixel number M of the intersection of these two approximation straight lines is obtained. (Step S206).

Next, the CPU 21 of the image reading device 10 compares the adjustment information read from the storage unit 63 with the data calculated in step S206 of the inspection adjustment process (step S207). If there is no difference between them, the positional relationship between the white reference plate and the image sensor unit 17 in the image reading device 10 matches their parallel relationship in the adjustment process.

When the above parallel relationships do not match, that is, when the mounting position of the image sensor unit 17 in the image reading device 10 deviates from the normal position, the aforementioned comparison results show the following tendencies.

(1) When the first pixel side is lower than the normal position (the distance between the lens surface of the image sensor unit 17 and the white reference plate is large), the output of the first pixel side is decreased and the pixel number of the intersection point is the final pixel side. shift to

(2) If the last pixel side is lower than the normal position, the output of the last pixel side is lowered and the pixel number of the cross point is shifted to the first pixel side.
Note that when the fixed position is higher than the normal position in the adjustment process (the distance between the lens surface of the image sensor unit 17 and the white reference plane is short), the maximum and minimum values of the RG approximate straight line and the BG approximate straight line are stored in the storage unit 63. tends to be larger than the value stored in .

From the above tendencies (1) and (2), the CPU 21 of the image reading device 10 determines the difference between the intersection pixel number N indicated by the adjustment information and the intersection pixel number M obtained in the inspection and adjustment process on the image reading device 10 side. is equal to or less than the reference value α (α is a positive integer, for example, the reference value α≈52) (step S208; Yes), the mounting position of the image sensor unit 17 needs to be finely adjusted. The inspection process is terminated by determining that there is no such condition. At this time, the operation display unit 26 may display that fine adjustment is unnecessary.

When the absolute value of the difference between the pixel number N and the pixel number M exceeds the reference value α (step S208; No), the CPU 21 of the image reading device 10 compares N and M (step S209).

If the pixel number M obtained in the inspection process is greater than the pixel number N indicated by the adjustment information (step S209; Yes), the intersection point is shifted toward the final pixel side (the first pixel side is lower than the normal position). Therefore, an instruction to add a correction member to the final pixel side is displayed on the operation display unit 26 (step S210), and the inspection process is finished. By adding the correction member on the final pixel side, the final pixel side is moved away from the white reference plate, and the image sensor unit 17 approaches parallel to the white reference plate.

If the pixel number M obtained in the inspection and adjustment process is smaller than the pixel number N indicated by the adjustment information (step S209; No), the pixel number at the intersection is shifted toward the first pixel (the final pixel is lower than the normal position). ), an instruction to add a correction member to the first pixel side is displayed on the operation display unit 26 (step S211), and the inspection process ends. By adding the correction member to the first pixel side, the first pixel side moves away from the white reference plate, and the image sensor unit 17 approaches parallel to the white reference plate.

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 embodiments, an example of an image sensor unit having three line channels of R, G, and B has been described. The number of line channels is not limited to this, and may be three or more.

The configuration of the image reading device 10 to which the image sensor unit is attached is not limited to that shown in FIG. The device may be configured to be capable of reading only by the skimming method, or may be a device having only the function of reading the original on the platen glass without the skimming function.

Further, in the embodiment, an example in which the sensor substrate 60 is attached to the housing 30 to which the irradiation unit 40 and the rod lens array 50 are already attached and the position is adjusted is shown, but the assembly order is not limited to this. The lens array may be mounted and aligned last.

In the embodiment, an example is shown in which the adjustment information stored in the storage unit 63 during manufacturing and assembly is used for fine adjustment of the mounting position of the image sensor unit 17 in the image reading device 10, but the application is not limited to this. For example, if the adjustment information stored in the storage unit 63 of the image sensor unit 17 is used for shading correction (correction of sensitivity non-uniformity) in the image reading apparatus 10, a color document can be read with high definition and little color shift. becomes possible.

DESCRIPTION OF SYMBOLS 10... Image reader 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... Image sensor unit 18... Image sensor Units 19a, 19b... White reference plate 20... Control circuit section 21... CPU
22 ROM
23 RAM
24 -- I/F section 25 -- Image processing section 26 -- Operation display section 30 -- Housing 32 -- Transmissive body 40 -- Irradiation section 42 -- Light guide 44 -- Light source 44a -- LED substrate 45 -- Support wall 50 -- Rod lens array 60 ... Sensor substrate 61 ... Photoelectric conversion unit 63 ... Storage unit

Claims (9)

a sensor substrate provided with a photoelectric conversion unit in which a first line channel, a second line channel, and a third line channel each composed of a light receiving element for one line are adjacent in parallel in this order;
an irradiation unit that irradiates a document surface with white light;
a rod lens array that guides the light emitted from the irradiation unit and reflected by the document surface to the photoelectric conversion unit;
a storage unit, a housing, and
has
The irradiation unit, the rod lens array, and the sensor substrate irradiate white light from the irradiation unit, which emits a prescribed amount of light on a white reference plate arranged at a predetermined relative position with respect to the rod lens array. fixed to the housing at a position where the output values of the first line channel, the second line channel, and the third line channel of the photoelectric conversion unit satisfy predetermined acceptance criteria in the state of the photoelectric conversion unit;
The image sensor unit, wherein the storage section stores adjustment information based on the output value of the photoelectric conversion section when fixed. 2. The image sensor unit according to claim 1, wherein the sensor substrate is fixed to the housing to which the irradiation unit and the rod lens array have been attached at a position satisfying the acceptance criteria. 3. The image sensor unit according to claim 1, wherein the adjustment information includes output values for each pixel of the first line channel, second line channel, and third line channel. The acceptance criteria are as follows: (output value of the first line channel - output value of the second line channel), the maximum value of the linear first-order approximation straight line is Amax, the minimum value is Amin, (the output value of the third line channel - the second (maximum value Amax - minimum value Bmin) and (maximum value Bmax - minimum value Amin), where Bmax is the maximum value and Bmin is the minimum value of the linear first-order approximation straight line of line channel output value) are both less than or equal to a predetermined value,
The image sensor unit according to any one of claims 1 to 3, characterized in that: The adjustment information includes a linear first-order approximation straight line of (output value of first line channel−output value of second line channel) and a linear first-order approximation straight line of (output value of third line channel−output value of second line channel). 5. The image sensor unit according to any one of claims 1 to 4, further comprising a pixel position of an intersection point of the next approximation straight line. The adjustment information includes the maximum value Amax, minimum value Amin, (output value of the third line channel−second line channel 6. The image sensor unit according to claim 5, further comprising a maximum value Bmax and a minimum value Bmin of a linear first-order approximation straight line of (output value of ). An image reading apparatus equipped with the image sensor unit according to any one of claims 1 to 6. A measurement unit that measures the output values of the first line channel, the second line channel, and the third line channel while irradiating the white reference plate of the device with the white light from the irradiation unit that emits light at the specified light amount. When,
a correction information generation unit that generates correction information for the mounting position of the image sensor unit based on the measurement value obtained by the measurement and the adjustment information stored in the storage unit;
8. The image reading device according to claim 7, comprising: Based on the adjustment information stored in the storage unit, the correction information generation unit generates a linear first-order approximation straight line of (output value of first line channel−output value of second line channel) and (third The pixel position of the intersection of the linear first-order approximation straight line (output value of the line channel - output value of the second line channel) is obtained, and the pixel position of the intersection is obtained based on the measured value of the measuring unit, and these pixels 9. The image reading apparatus according to claim 8, wherein correction information indicating which end position of the image sensor unit in the line direction should be corrected is generated from the position comparison.

Images