JP4098175B2 - Image reading apparatus and assembly method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus that obtains color image data for an image forming apparatus, for example.
[0002]
[Prior art]
An image reading device is used to obtain image data by photoelectrically converting reflected light obtained by illuminating a reading object such as a sheet-like document or a book or a three-dimensional object with an image reading sensor such as a CCD sensor. Is done.
[0003]
In many image reading apparatuses, a reading table (glass plate) that holds a reading object, an illuminating device that illuminates the reading object set on the reading table, reflected light from the reading object illuminated by the illuminating device, It includes an optical device that guides image light to the CCD sensor, an imaging lens that gives predetermined imaging characteristics to the image light guided by the CCD sensor, and the like.
[0004]
As a CCD sensor, a three-line CCD sensor that photoelectrically converts image light corresponding to R, G, and B components that are additive color mixing three primary colors and a black that photoelectrically converts image light corresponding to a monochrome image today. A 4-line CCD sensor in which the (Bk) CCD sensor is integrally formed on the same substrate is used.
[0005]
However, when each of the image light obtained from a monochrome manuscript and the image light obtained from a color manuscript is imaged on a CCD sensor by a single imaging lens, the color component is affected by the effect of lateral chromatic aberration (lateral chromatic aberration). It is known that the focal position is different for each.
[0006]
When a 4-line CCD sensor in which an R, G, B 3-line CCD sensor and a black CCD sensor are formed on the same substrate is used, the line sensor is located on or near the optical axis of the imaging lens. It is known that there is a difference in the distance, that is, the optical path length, between the lens sensor and the line sensor located farthest from the optical axis of the lens.
[0007]
For this reason, in a color image reading apparatus, it has been proposed that one of the outputs from the 3-line CCD sensor is used as a reference, and the remaining two outputs are corrected for lateral chromatic aberration compared to the reference output. (For example, refer to Patent Document 1).
[0008]
Also, in a color document reader, the distance from the document surface to the imaging lens and the optical path length from the imaging lens to the line sensor are colored so that each color has the same imaging magnification based on the chromatic aberration of the imaging lens. It is proposed to change every time (for example, refer to Patent Document 2).
[0009]
Further, it has been proposed that the first image sensor that photoelectrically converts red light is tilted toward the reduction lens side with respect to the third image sensor that photoelectrically converts blue light to suppress color shift due to lateral chromatic aberration ( For example, see Patent Document 3).
[0010]
[Patent Document 1]
JP 2002-112046 A (Summary, FIGS. 4 and 5, paragraphs [0038], [0049] to [0054])
[0011]
[Patent Document 2]
JP 2001-251475 A (summary, FIGS. 2 to 7, paragraphs [0016] to [0018], [0025] to [0030])
[0012]
[Patent Document 3]
JP-A-5-160959 (abstract, claim 1, FIG. 5, FIG. 6, paragraphs [0021] to [0032])
[0013]
[Problems to be solved by the invention]
However, none of the patent documents discloses a positioning method for fixing the CCD sensor to the focal position of the imaging lens or a technique for keeping the process within a certain time.
[0014]
Also, in any document, by using a four-line sensor in which a color three-line sensor and a black line sensor are incorporated on the same substrate, image light given convergence by one imaging lens is used. There is no description about the deviation of the optimum focus position for the color line sensor and the optimum focus position for the black line sensor.
[0015]
If the optimum focus position for the color line sensor and the optimum focus position for the black line sensor deviate from the allowable range, for example, after adjusting the focus of the color three-line sensor, the black line sensor If the focus of the black line sensor is out of the permissible range, there is a problem that the focus of the color three-line sensor must be adjusted again.
[0016]
If the focus of the black line sensor is not within the allowable range even when the focus of the color 3-line sensor is adjusted again, the focus of either the color or black line sensor is allowed. A technique is also widely adopted that suppresses the lower limit level within the range and keeps the focus of the image light imaged on all the line sensors within the allowable range.
[0017]
This has the problem that the time required for the adjustment is greatly increased as well as the time required for the adjustment process cannot be managed (set).
[0018]
An object of the present invention is to provide an image reading apparatus capable of obtaining image data from each of a monochrome image and a color image under optimum imaging conditions.
[0019]
[Means for Solving the Problems]
This invention First to third line sensors that provide convergence to light from an object to be read by a converging lens and photoelectrically convert image light corresponding to R, G, and B color components in parallel with the focal plane of the converging lens. And a fourth line sensor that photoelectrically converts image light corresponding to a black image are integrally arranged on the same plane, and the first line sensor is based on the range of the focal position where the MTF exhibits a predetermined level with the focal plane as the center. Or a black image formed on the fourth line sensor with respect to the center value in the range between the minimum value and the maximum value of the MTF characteristics of the R, G, and B image lights respectively formed on the third line sensor. By tilting the plane on which the first to fourth line sensors are arranged with respect to the focal plane in accordance with the difference in the central value of the MTF characteristic of light and the polarity thereof, the first to third line sensors or the fourth line sensors are arranged. Any of the line sensors The position of the square, by matching the center value associated with the MTF, the position of rest of the line sensor, MTF is set to a predetermined position within a predetermined level Image reading apparatus Assembly method Is to provide.
[0021]
Further, according to the present invention, in the first imaging condition, the first color component light exhibiting the first MTF characteristic managed with the first allowable width around the position at the first distance from the reference position, The second color component light exhibiting the second MTF characteristic managed with the second allowable width centered on the position at the second distance from the reference position, and the reference condition in the third imaging condition A third color component light exhibiting a third MTF characteristic managed with a third allowable width centered on a position at a third distance from the position, and a fourth distance from the reference position in the fourth imaging condition When the fourth color component light exhibiting the fourth MTF characteristic managed with the fourth allowable width around the position of each of the first color component light and the first color component light is incident, A lens imaged around the position of the first distance to the fourth distance; The first to fourth color component lights that are imaged by the lens centered on the position of the first distance to the fourth distance are arranged so as to be able to receive each of the first to fourth color component lights. The first to fourth line sensors that output electrical signals corresponding to each of the first and fourth line sensors and the first to fourth line sensors are integrally supported along a plane that includes the reference position and is orthogonal to the optical axis of the lens. And the difference between the center value of the maximum value and the minimum value range of the first MTF characteristic to the third MTF characteristic with respect to the center value of the allowable width of the fourth MTF characteristic, and the polarity Or based on the difference and polarity of the center value of the allowable range of the fourth MTF characteristic with respect to the central value of the range of the maximum value and the minimum value of the allowable range of each of the first to third MTF characteristics. ,the above An angle adjusting mechanism for changing the angle between the support member and the optical axis, there is provided an image reading apparatus characterized by having a.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
FIG. 1 is a schematic diagram illustrating an example of an image reading apparatus to which an embodiment of the present invention is applied.
[0024]
As shown in FIG. 1, the image reading apparatus 101 includes a transparent plate-like document table 11 typified by glass or the like, formed of a material that transmits light, and having a substantially uniform thickness.
[0025]
On one end side of the document table 11, a size plate 11 a is provided that indicates a reference position when an object to be read (for example, a sheet-like document, hereinafter abbreviated as document) O is set on the document table 11.
[0026]
A CCD sensor 12 that converts image information of the document O transmitted as image light, which will be described later, into an electrical signal (image data) is provided at a predetermined position inside the image reading apparatus 101 below the document table 11.
[0027]
As will be described below with reference to FIG. 2, the CCD sensor 12 detects a color image (reflection from the original O) as R (red), G (green), and B (blue) which are three primary colors of additive color mixture. Color line CCD sensor (hereinafter referred to as a color sensor) 12C, which is integrally formed with three line sensors 12R, 12G and 12B, and a monochrome (achromatic) line sensor (hereinafter referred to as a monochrome sensor). 12M is a composite CCD sensor (4-line CCD sensor) provided in parallel. Hereinafter, mechanisms and elements provided independently for each color component are identified by adding “R”, “G”, “B”, and “Bk” at the end.
[0028]
The above-described CCD sensor 12 can ensure a high sharpness when reading a monochrome image as compared with a known three-line CCD for color, and stability (reproducibility) when the same image is read a plurality of times. ) Is known to be expensive. In addition, since the monochrome sensor 12M and the color sensor 12C are provided independently, the reading performance of each sensor (single line sensor) is equivalent.
[0029]
In a space below the document table 11, an illumination device 13 that illuminates the document O set on the document table 11, a first carriage 14 that moves the illumination device 13 along the document table 11, and a first carriage 14. A second carriage 15 that guides image light to the CCD sensor 12, which will be described below, is provided.
[0030]
The first carriage 14 is provided with an image extraction mirror 14a that takes out reflected light obtained by illuminating the original O with illumination light from the illumination device 13 and reflects it in a predetermined direction. The image extraction mirror 14 a reflects image light, that is, image information of the original O in which an image included in the original O is converted into light brightness and darkness toward the second carriage 15.
[0031]
The second carriage 15 is provided with first and second mirrors 15 a and 15 b for guiding the image light extracted by the image extraction mirror 14 a to the CCD sensor 12.
[0032]
An imaging lens (convergence lens) 16 between the second carriage 15 and the CCD sensor 12 gives predetermined optical characteristics and imaging magnification to the image light reflected by the second mirror 15b and guided to the CCD sensor 12. Is provided.
[0033]
Note that the optical axis of the imaging lens 16 is on the color sensor 12C side of the 4-line sensor 12, and is on the line sensor 12G located in the center of the three line sensors 12R, 12G, and 12B of the color sensor 12C. Have been matched. That is, in the 4-line sensor 12, the center of the light receiving surface (not shown) of the line sensor 12G at the center of the three line sensors 12R, 12G, and 12B of the color sensor 12C is aligned with the optical axis of the imaging lens 16. Have been placed. The 4-line sensor 12 holds the individual line sensors with respect to the focal plane FP (see FIGS. 6 to 8) orthogonal to the optical axis of the imaging lens 16 by the angle adjustment mechanism (light receiving position adjustment mechanism) 1. An angle of a reference plane (optical axis direction) defined so as to include at least one of a base plate (not shown) or each light receiving surface is supported so as to be arbitrarily settable.
[0034]
The sensitivity of each single line sensor of the CCD sensor 12 and the CCD sensor 12 image of the original O are located at a predetermined position in the vicinity of the size plate 11a or the back surface (inside of the image reading apparatus 101) and can be illuminated by the illumination device 13. Is provided with a white reference plate 17 that is used to correct a threshold level for distinguishing between a white image and a black image.
[0035]
In reading the original image by the image reading apparatus 101 described above, the original O is positioned at a predetermined position of the original table 11 of the image reading apparatus 101, and an image reading is instructed from an operation panel (not shown) or an external apparatus. The lighting device 13 is turned on so as to be able to provide illumination light having a predetermined light intensity.
[0036]
Thereafter, the first and second carriages 14 and 15 are moved along the document table 11 at a predetermined speed corresponding to the reading magnification, so that the image information of the document O is illuminated by illumination light from the illumination device 13. Illuminated sequentially. Therefore, a reflected light including the image information of the original O as light brightness is generated. Hereinafter, this reflected light is referred to as image light.
[0037]
The image light is further reflected by the first mirror 15 a (of the second carriage 15) and the second mirror 15 b by the image extraction mirror 14 a, and given imaging characteristics are given by the imaging lens 16. An image is formed on the light receiving surface.
[0038]
Image light imaged on the light receiving surface of the CCD sensor 12 is photoelectrically converted in order, and is output to an image signal processing unit described below with reference to FIG. 3 at a predetermined timing.
[0039]
As shown in FIG. 3, the image signals (outputs of the respective line sensors) input to the image signal processing unit 50 are S / N (signal / noise) ratio improving amplifiers (preamplifiers) 51R, 51G, 51B and 51Bk, respectively. Thus, prior to the image processing described below, the signal is amplified to a predetermined level, and the magnitude (gain) between the signals is adjusted by the gain controllers (PGA) 52R, 52G, 52B and 52Bk connected to each preamplifier. .
[0040]
Signals output from the respective gain controllers 52R, 52G, 52B and 52Bk are converted into digital signals by the AD converters 53R, 53G, 53B and 53Bk, and white by the shading correction circuits 54R, 54G, 54B and 54Bk. In accordance with the threshold level set based on the reflected light from the reference plate 17, the white level and black level reference values are corrected and output to the image processing circuit 55.
[0041]
The image signal input to the image processing circuit 55 is processed by known image processing, such as color correction, that is, color balance and density correction, edge enhancement, that is, identification (cutting out) of color boundary portions and character areas, or character specification, that is, character and Various processes such as conversion of the image information of the identified area into character data are performed and output to an image memory (not shown) or an external storage device (external device) 60.
[0042]
Incidentally, as described above, in the 4-line CCD sensor 12, the optical axis of the imaging lens 16 is coincident with the G-line sensor 12G located in the center of the color CCD sensor 12C of the 4-line CCD sensor 12. ing. Therefore, each of the B line sensor 12B and the R line sensor 12R is separated by an equal distance from the G line sensor 12G on the focal plane FP (see FIGS. 6 to 8) orthogonal to the optical axis of the imaging lens 16. It will be located at the position. Further, the Bk line sensor 12Bk is positioned at a position farthest from the optical axis of the imaging lens 16. That is, the image light formed on the light receiving surface of each CCD sensor includes image light (G) guided on the optical axis of the lens 16 and image light (Bk, R, B) guided along other optical paths. ) Have different focus balances as will be described below with reference to FIG. 4 or FIG. The focus balance is a focus (imaging) position of image light of an arbitrary color component (focal length of image light imaged by the imaging lens 16 and is a position where the MTF is maximum here. ) And the defocus position range in which the MTF decreases to a certain level.
[0043]
FIG. 4 is a schematic diagram for explaining an example of the focus balance and its center value when the image light of each color component is imaged on the CCD sensor by the imaging lens. In FIG. 4, the horizontal axis (x axis) is the distance (defocus position) between the origin (reference position, in this example, the optical axis position of the imaging lens) and the center of focus balance when obtaining the focus balance. The vertical axis (y-axis) indicates MTF.
[0044]
As is apparent from FIG. 4, the imaging lens 16 has a distance P from the reference position with respect to Bk, that is, black image light. _Bk [P ₁ ] Has a first MTF characteristic (curve Bk) that is substantially line symmetric.
[0045]
Further, the imaging lens 16 is related to the image light R by a distance P from the reference position. _R The second MTF characteristic (curve R), which is substantially line-symmetric with respect to the position indicated by, and the image light G, the distance P from the reference position. _G About the third MTF characteristic (curve G) that is substantially line-symmetric with respect to the position indicated by, and the image light B, the distance P from the reference position _B And a fourth MTF characteristic (curve B) that is substantially line symmetrical about the position indicated by.
[0046]
It should be noted that the second MTF characteristic (curve R), the third MTF characteristic (curve G), and the fourth MTF characteristic (curve B) are each expressed as a range between the maximum and minimum focus balance values. The range of the color focus balance that can be performed is approximately the same as the range of the first MTF characteristic (curve Bk). Also, the color focus balance center value [P ₂ ] Is the central value [P of the focus balance of the black image light] ₁ ] It is almost equal to.
[0047]
Therefore, by using an imaging lens having a focus balance as shown in FIG. 4, when the CCD sensor 12 is disposed at the focusing position of the imaging lens 16, for example, the position adjustment is performed only once for Bk, that is, black image light. As a result, a focus within a predetermined allowable range can be obtained for each of the remaining color components. That is, the center of the focus balance as shown in FIG. 4 is the same for the focus balance and the color focus balance of the black image light Bk, so that the CCD sensor 12 is focused on the focal position of the imaging lens 16. The alignment becomes very simple.
[0048]
However, it is practically difficult to obtain the imaging lens 16 having the focus balance as shown in FIG. 4, and an operation such as “selection” from a plurality of imaging lenses is required. Therefore, the cost is increased.
[0049]
FIG. 5 is a schematic diagram for explaining an example of the focus balance and the center value of the imaging lens in which the center value of the focus balance of the black image light and the center value of the color focus balance do not match. As will be described below with reference to FIG. 5, the focus balance in many imaging lenses often does not match the center value of the black image light focus balance and the center value of the color focus balance, and FIGS. 6 to 8 are used. It is useful to adopt the adjustment method described later.
[0050]
As shown in FIG. 5, the imaging lens that can be easily obtained has a central value [P of black focus balance]. ₁ ] And the color focus balance center value [P ₂ ] Often does not match. However, the imaging lens having the focus balance shown in FIG. 5 is relatively inexpensive, and if the adjustment process can be simplified by devising a method for aligning the CCD sensor with respect to the focal position of the imaging lens, image reading is possible. By mounting on the apparatus 101, a great merit in terms of cost is brought about. Hereinafter, an example of the method will be described.
[0051]
FIG. 6 illustrates a first fixing method in consideration of the focus balance of the imaging lens when fixing the CCD sensor.
[0052]
As shown in FIG. 6, the 4-line CCD sensor 12 is outlined in FIG. 1, but the CCD sensor 12 is not described in detail with respect to a plane (focal plane) FP orthogonal to the optical axis of the imaging lens 16. It is held by an angle adjusting mechanism 1 that can set the angle of the light receiving surface (or a reference surface (not shown) of the CCD sensor) to an arbitrary angle. FIG. 6 shows a case where the angle given by the angle adjustment mechanism 1 is “0 °”.
[0053]
Therefore, the angle of the light receiving surface of the CCD sensor shown in FIG. 6 is set by the center of black focus balance (second physical characteristic) [P ₁ ] And the center of color focus balance (first physical characteristic) [P ₂ ] Is useful for generally matching imaging lenses.
[0054]
FIG. 7 illustrates a second fixing method in consideration of the focus balance of the imaging lens when fixing the CCD sensor.
[0055]
In the example shown in FIG. 7, the 4-line CCD sensor 12 has a predetermined angle by the angle adjustment mechanism 1 in a direction in which the light receiving surface of the black line sensor 12 </ b> Bk moves away from the focal plane FP orthogonal to the optical axis of the imaging lens 16. θ ₁ (G line sensor 12G is positioned on focal plane FP).
[0056]
That is, the angle (θ of the light receiving surface of the CCD sensor shown in FIG. ₁ ) Is set at the center of black focus balance (second physical characteristic) [P ₁ ] And the center of color focus balance (first physical characteristic) [P ₂ ] Does not match, for example, [P ₂ ] Is useful for an imaging lens that is shifted to the “−” side. The angle (θ ₁ ) Is the distance between the rear main plane of the imaging lens 16 and the black line sensor 12Bk with respect to the distance (G focal length) between the rear main plane (not shown) of the imaging lens 16 and the G line sensor 12G. Needless to say, it is set according to the difference from the (Bk focal length).
[0057]
Therefore, when the 4-line CCD sensor 12 is arranged at the focus position of the imaging lens 16, for example, by adjusting the position only once for Bk, that is, black image light, the remaining color components are also within a predetermined allowable range. Can be easily arranged at a position where the focus can be obtained.
[0058]
FIG. 8 illustrates a third fixing method in consideration of the focus balance of the imaging lens when fixing the CCD sensor.
[0059]
In the example shown in FIG. 8, the 4-line CCD sensor 12 has an angle adjustment mechanism in a direction in which the light receiving surface of the black line sensor 12 </ b> Bk approaches the imaging lens 16 rather than the focal plane FP orthogonal to the optical axis of the imaging lens 16. 1 for a predetermined angle θ ₂ Is held by.
[0060]
That is, the angle (θ of the light receiving surface of the CCD sensor shown in FIG. ₂ ) Is set in the same manner as described with reference to FIG. 5, the center of the black focus balance (second physical characteristic) [P ₁ ] And the center of color focus balance (first physical characteristic) [P ₂ ] Does not match and is not shown in FIG. ₂ ] Is useful for an imaging lens in which it is shifted to the “+” side in the opposite direction to FIG. The angle (θ ₂ ) Is the distance between the rear main plane of the imaging lens 16 and the black line sensor 12Bk with respect to the distance (G focal length) between the rear main plane (not shown) of the imaging lens 16 and the G line sensor 12G. Needless to say, it is set according to the difference from the (Bk focal length).
[0061]
Therefore, when the 4-line CCD sensor 12 is arranged at the focus position of the imaging lens 16, for example, by adjusting the position only once for Bk, that is, black image light, the remaining color components are also within a predetermined allowable range. Can be easily arranged at a position where the focus can be obtained.
[0062]
Although the center value of the focus balance for each color component in the imaging lens 16 is not shown, it can be obtained by being attached to an inspection jig (not shown) for detecting the characteristics of the imaging lens 16 or the imaging lens 16. It can be easily identified or acquired from the inspection data.
[0063]
Further, the angle adjusting mechanism 1 is a micro actuator (not shown) (for example, a displacement mechanism capable of displacing the reference surface of the CCD sensor with respect to the focal plane by supplying a current having a predetermined polarity, or a linear motion motor). Needless to say, it may be set for each reading device according to the intensity of the image signal for each color component obtained by receiving light by the CCD sensor.
[0064]
For example, in the image signal processing unit 50 described above with reference to FIG. 2, for example, before the gain controllers (PGA) 52R, 52G, 52B, and 52Bk, any output of the preamplifiers 51R, 51G, 51B (three color sensors). The output of the line sensor having the maximum output) is compared with the output of the preamplifier 51Bk, and the polarity (+ or-) and the absolute value (size) of the difference are obtained, thereby controlling the microactuator described above. The amount can be set easily.
[0065]
In order to describe the above-described embodiment, an example of the operation has been described by taking an image reading apparatus (scanner) as an example. However, an image output unit such as a scanner and a page printer (color printer) is integrally formed. Needless to say, the present invention can also be used for a color copying machine, a similar composite image processing apparatus, a facsimile machine, or the like.
[0066]
The present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the invention when it is implemented. Moreover, each embodiment may be implemented in combination as appropriate as possible, and in that case, the effect of the combination can be obtained.
[0067]
【The invention's effect】
As described above in detail, according to the present invention, the image light given the convergence by the imaging lens is generated by using the 4-line sensor in which the color 3-line sensor and the black line sensor are integrated. The optimum focus position for the black line sensor can be matched with the optimum focus position for the color line sensor. Therefore, the process required for the adjustment work when fixing the CCD sensor to the focus position of the imaging lens is shortened. This greatly reduces the assembly cost of the image reading apparatus.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an example of an image reading apparatus to which an embodiment of the present invention is applied.
FIG. 2 is a schematic diagram for explaining an example of a 4-line CCD sensor incorporated in the image reading apparatus shown in FIG.
3 is a schematic diagram illustrating an example of a configuration of an image signal processing unit incorporated in the image reading apparatus illustrated in FIG.
FIG. 4 is a schematic diagram illustrating focus balance for each color component of an imaging lens incorporated in the image reading apparatus illustrated in FIGS. 1 to 3;
FIG. 5 is a schematic diagram illustrating focus balance for each color component of an imaging lens incorporated in the image reading apparatus illustrated in FIGS. 1 to 3;
6 is a schematic diagram for explaining a first fixing method in consideration of focus balance of an imaging lens when fixing a CCD sensor incorporated in the image reading apparatus shown in FIGS. 1 to 3; FIG.
7 is a schematic diagram illustrating a second fixing method in consideration of the focus balance of the imaging lens when fixing the CCD sensor incorporated in the image reading apparatus shown in FIGS. 1 to 3; FIG.
FIG. 8 is a schematic diagram for explaining a third fixing method in consideration of the focus balance of the imaging lens when fixing the CCD sensor incorporated in the image reading apparatus shown in FIGS. 1 to 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Angle adjustment mechanism, 11 ... Document table, 12 ... 4-line CCD sensor, 12C ... Color CCD sensor, 12M ... Line sensor for black, 12R ... R line sensor, 12G ... G line sensor, 12B ... B line sensor, 13 DESCRIPTION OF SYMBOLS ... Illuminating device, 14 ... 1st carriage, 14a ... 1st image mirror, 15 ... 2nd carriage, 15a ... 2nd image mirror, 15b ... 3rd image mirror, 16 ... Imaging lens, 17 ... White reference board, 50 ... Image signal processing unit, 101 ... Image reading apparatus.

Claims (5)

Convergence lens gives the light from the object to be converged,
Parallel to the focal plane of the converging lens, first to third line sensors that photoelectrically convert image light corresponding to the R, G, and B color components and a fourth line that photoelectrically converts image light corresponding to the black image Place the sensor and the sensor on the same plane,
The minimum and maximum values of the MTF characteristics of the R, G, and B image lights formed on the first to third line sensors based on the range of the focal position where the MTF exhibits a predetermined level around the focal plane. The first to fourth line sensors are arranged according to the difference in the central value of the MTF characteristic of the black image light imaged on the fourth line sensor with respect to the central value of the range between the values and the polarity thereof. By tilting the plane with respect to the focal plane, the position of one of the first to third line sensors or the fourth line sensor is made to coincide with the center value associated with the MTF, thereby remaining line sensors. The image reading apparatus is assembled at a predetermined position where the MTF falls within a predetermined level . 2. The method of assembling an image reading apparatus according to claim 1, wherein the first to third line sensors are three-line color CCD sensors that receive the three primary colors of additive color mixing independently and photoelectrically convert each of them. . When the difference between the center value of the MTF characteristics of the black image light and the center value of the range between the minimum value and the maximum value of the MTF characteristics of the R, G, B image light is “0”, the line sensor is arranged. 3. The image reading apparatus assembling method according to claim 1, wherein the plane is parallel to the focal plane. In the first imaging condition, the first color component light exhibiting the first MTF characteristic managed with the first allowable width around the position of the first distance from the reference position, and in the second imaging condition The second color component light exhibiting the second MTF characteristic managed with the second allowable width around the position at the second distance from the reference position, and the third color from the reference position in the third imaging condition. In the third color component light exhibiting the third MTF characteristic managed with the third allowable width around the position of the distance and the fourth imaging condition, the position of the fourth distance from the reference position is the center. When the fourth color component light exhibiting the fourth MTF characteristic managed by the fourth allowable width is incident, the first to fourth color component lights are respectively transmitted to the first distance or A lens that is imaged about the position of the fourth distance;
The first to fourth color component lights are arranged so as to be able to receive the first to fourth color component lights focused on the positions of the first distance to the fourth distance by the lens, respectively. First to fourth line sensors that output electrical signals corresponding to each of the
A support member that integrally supports the first to fourth line sensors along a plane including the reference position and orthogonal to the optical axis of the lens;
The difference and polarity of the center value of the maximum value and the minimum value range of each of the first to third MTF characteristics with respect to the center value of the allowable width of the fourth MTF characteristic, or the first Based on the difference and polarity of the center value of the allowable width of the fourth MTF characteristic with respect to the central value of the maximum value and minimum value range of the allowable width of each of the MTF characteristics to the third MTF characteristics of An angle adjustment mechanism for changing the angle formed by the optical axis;
Images reader you, comprising a. It said angle adjustment mechanism, based on the difference and the polarity of the central value, the image reading equipment according to claim 4, wherein said support member and wherein the tilting with respect to the optical axis.

Images