TWI250782B - Image sensor unit and image reader - Google Patents

Abstract

Illuminators (5, 6) are disposed oppositely on the opposite sides of a lens array (2). Assuming the effective depth of field of the lens array (2) is a, 90% power band width of the quantity of light distribution curve of the illuminators (5, 6) along the optical axis of the lens array (2) is not smaller than a for both illuminators (5, 6). Intersection (B) of the optical axis (Z2) of illumination light from the illuminator (5) and the optical axis (Z1) of the lens array (2) is located closer to the lens array (2) than a document side focal point (A) and the intersection (C) of the optical axis (Z3) of exiting light from the illuminator (6) and the optical axis (Z1) is located farther from the lens array (2) than the document side focal point (A). Distances between the intersections (B, C) and the document side focal point (A) are respectively not longer than a/2.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor unit and an image reading apparatus suitable for image scanners, facsimile machines, and photocopiers, and the like, and particularly for reading a document surface. The image sensor unit and the image reading device of the reflected light. [Prior Art] In the image reading device such as a portrait scanner, a facsimile machine, and a photocopying machine, a contact type image sensor (hereinafter abbreviated as CIS) is used as an image for reading reflected light from the original surface. One of the means of reading. The contact type image sensor has a light source for illuminating a document, receives reflected light through the lens, and converts the reflected light into an electrical image by a light receiving portion formed by a photoelectric conversion element. In recent years, with the increase in the reading speed of the image reading device, it is required to increase the illumination light intensity in order to shorten the reading time. Then, a technique of accommodating a lens array (Lens Array) to face the illumination device of the two systems to increase the amount of illumination is disclosed (for example, Patent Document 1 (JP-A-2002-5 7 8 3)). The contact type image sensor unit (CIS unit) is used under the transparent original support supporting the original. There are two main methods for setting the image sensor unit in the image reading device. (1) A paper-feed type that fixes the sensor unit to the image reading device and moves the original on the original support. (2) Fix the original on the original support of the image reading device, -4- (2) 1250782 Move the sensor unit to read the platform (Flatbed) type. Here, a configuration example of a conventional CIS unit will be described. Fig. 8 is a cross-sectional view showing the structure of a conventional CIS unit. In the conventional CIS list, the frame 11 supports the light source and 15b of the LED used for illuminating the original, and the illumination devices 16a and 16b. The illuminating device 16a 5 is configured to receive the light emitted from the light sources 15a and 15b, respectively, and to illuminate the light to the long light guide of the line of the document reading portion. Further, a sensor substrate 14 having a plurality of light receiving portion sensor arrays 13 for photoelectrically converting an optical image of the original into electrical signals is mounted under the frame 11, and the frame 1 1 supports the optical of the draft. A lens array 12 that is imaged on the sensor array 13. Provided below the sensor substrate 14 is connected to the sensor array 13 and the connector 17 of the machine. Such a conventional CIS unit is placed below the original support 18 as described above. In this CIS unit, in order to increase the amount of illumination device for illuminating the original, the illumination system composed of the light source and the illumination device is provided with two two system clamp lens arrays 12, which are disposed face to face in a symmetrical position. Further, since the light-emitting portions of the illumination devices 16a and 16b are provided with energy, the light utilization efficiency is high. For example, the document side focus A of the lens array 12 is set at a position slightly above the document side surface of the support body 18 and away from the lens 12 to concentrate the light emitted by the illumination device of the two systems. The depth of the written boundary of the lens array 12 is set to be deep. With such a structure, in the paper-feeding image reading device, the speed of the paper feed speed is increased, and the light of the 15a 16b light measurement in the element is used to make the original light, and the light is externally attached; That is to say, the problem of excessive contact friction between the original of the 5-5 (3) 1250782 and the original support can be avoided. Moreover, in the platform type image reading device, the surface irregularity can be easily read. Patent Document 1 provides a configuration in which the position of the illumination light from the light source is placed slightly above the focus of the original side of the lens array to make the original paper slightly float from the original support, and the light reading and output can be stabilized. According to this, the method of illuminating the original by the two faces in the face can increase the amount of light of the original and reduce the shadow caused by the unevenness of the original on the original, thereby improving the quality of the read image. However, such prior art has the following problems to be solved. In order to achieve higher speed reading, it is necessary to increase the light efficiency from the light source. Therefore, it is necessary to concentrate the light emitted from the light emitting portion of the light guide to increase the amount of light. Thus, in Patent Document 1, in order to use a plurality of illuminations to increase the amount of light of the illumination original, the focus of the two light sources is concentrated to increase the amount of light. However, this configuration improves the light collecting property of the light guide body, and the combined light amount distribution of the illumination light is sharpened, and the following side effects are shown in the figure. FIG. 9 is a cross-sectional view showing the high-speed paper-feeding image reading device using the conventional CIS unit. . The image reading device is provided with a platen 27 facing the support 18; the space between the document holder 18 and the platen is a paper feed path 28. Further, a document transport roller 2 5 is provided to hold the paper feed path 2 8 ; the original document 26 is transported by the document transport roller 25 in the paper feed 28 . The height of the platen 27 is set such that the document side focus is located at the center of the paper feed path 28. Even if it comes to the top of the original

In order to make the position of the I-shaped original document 27, the path point A -6 - (4) (4) 1250782 is used for the high-speed paper-feeding image reading device using the CIS unit, and the original 26 is passed. In the paper feed path 28, the position of the document 26 with respect to the optical axis direction of the lens array 12 is changed in the far and near directions (the optical axis direction of the lens array 12) with respect to the document side focus A. The width P of the paper feed path 28 means that the original 26 is shaken, and the maximum amplitude of the position change. On the other hand, if the position of the original document 6 is changed in the optical axis direction of the lens array 12, since the surface of the original document 26 is perpendicular to the optical axis of the lens array 12, the amount of illumination light on the surface of the original sheet 26 changes. Therefore, even if the density of the original document 6 is uniform, the output image of the reading device is likely to undergo a concentration fluctuation due to the height variation of the reading position. Further, as described above, in the conventional floor-type image reading apparatus, generally, the document having the surface unevenness is easily read, and the document-side focus A of the lens array 12 is set in the document holder 18. Above the original side surface position. Therefore, when the position of the document is changed in the optical axis direction of the lens array 12, the concentration fluctuation easily occurs. In order to suppress such a change in concentration, the allowable range of variation in the amount of illumination light is within 10% within the depth of the written boundary of the lens. In the patent document 2 (Japanese Patent No. 2 84 8 4 77), it is described that the light sources of the two systems are arranged such that the irradiation position of each light source slides up and down on the optical axis of the photon element to enable the imaging means. Within the range of the depth of the written world, the illumination of the original surface is roughly maintained. This configuration makes the combined light amount distribution uniform, and the variation of the read light amount can be suppressed even if the original position is shifted. However, although this structure improves the uniformity of the light amount distribution, the synthesis (5) 1250782 does not increase the amount of light itself, so it is not suitable for high-speed reading. Thus, when a complex light source is used, the uniformity of the light amount distribution of the combined light amount is used. There is a dilemma (Trad. That is, when the uniformity is emphasized, the amount of the peak of the combined light quantity distribution is also reduced. (Patent Document 1) Japanese Patent Laid-Open No. 2 0 0 2 - 5 7 8 5 3 (Patent Document 2) Japanese Patent No. 2 8 4 8 4 7 7 SUMMARY OF THE INVENTION The present invention has been made in view of the circumstances, and an object of the present invention is to provide a read image sensor unit and an image reading device that can suppress fluctuations in document height. The image sensor unit according to the present invention is a first and second illumination device, an imaging means for the original document, and a plurality of sensor arrays for converting the reflected light into pixels (S ens 〇r A rray The image is characterized in that the first and second illumination devices are surfaced on both sides of the imaging means; and if the degree of the imaging means is a, 90% of each illumination cloth curve along the optical axis of the imaging means value The amplitudes are all equal to or greater than a; the optical axis of the optical axis of the first light and the optical axis of the optical axis of the imaging means are close to the optical axis of the outgoing light of the second illumination device of the imaging hand and the axis of the axis 2 intersection point, the increase in the original of the above-mentioned image forming means, and the sharpness of the relationship between e - 〇ff) is reduced. The t-page bulletin has a high illumination light amount, and the illumination amount is changed. The intersection of the light-quantity illuminating device disposed oppositely on the effective written boundary device, at the upper position; the optical side focus of the imaging means is away from the upper -8- (6) (6) 1250782 At a position, the distance between the first and second intersections and the document-side focus is equal to or less than a/2. In the present invention, since the first and second intersections are shifted in mutually different directions with respect to the original focus of the original document, fluctuations in the amount of combined light along the optical axis of the imaging means are suppressed. Further, since the magnitude of the offset and the light amount distribution curve of each illumination device are appropriately defined, the effective amount of the imaging means is within 1 〇% of the range of the writing depth depth a, and the peak of the combined light amount is The lighting device is only 180% of the time. Therefore, the amount of high light irradiation is obtained, and the variation in the amount of reading light accompanying the fluctuation of the height of the document is also suppressed. [Embodiment] Hereinafter, embodiments of the present invention will be specifically described with reference to additional drawings. (First embodiment) First, a first embodiment of the present invention will be described. Fig. 1 is a cross-sectional view showing the structure of a CIS unit according to a first embodiment of the present invention. In the present embodiment, the frame 1 supports the illumination devices 5 and 6 for illuminating the original. The sensor substrate 4 having a plurality of sensor arrays 3 for photoelectrically converting the optical image of the original into an electric signal is mounted under the frame 1. The frame 1 also supports the optical image of the original. A lens array (imaging means) 2 imaged on the detector array 3. The sensor array 3 is located at the sensor side focus of the lens array 2. Further, a sensor 7 is connected below the sensor substrate 4 to connect the sensor array 3 to the connector 7 of the external device. And -9- (7) (7) 1250782, LEDs are provided on the illumination devices 5 and 6 as a light source. The illuminating devices 5 and 6 are lenticular lens arrays 12 and are disposed face to face. Further, the horizontal distance x 1 ' of the optical axis Z1 of the lens array 2 and the reference point 5 a of the optical axis Z2 of the illumination device 5 is a horizontal distance x2 from the reference point 6a of the optical axis Z3 of the illumination device 6 short. Further, in the present embodiment, the illumination device 5 is arranged such that the intersection B of the optical axis Z2 and the optical axis Z1 is closer to the lens array than the original side focus A of the lens array 2 and the illumination device 6 is configured to be 'light The intersection C of the axis Z3 and the optical axis Z1 is farther from the lens array 2 than the original side focus A of the lens array 2. Further, the illumination devices 5 and 6 are arranged such that the distance between the focal point A and the intersection B and the distance between the focal point A and the intersection C are substantially equal to each other. Further, if the effective write boundary depth of the lens array 2 is a, the distance between the focal point A and the intersection B, and the distance ′ between the focal point A and the intersection C are both equal to or less than a/2. Further, 90% of the light distribution curves of the illumination devices 5 and 6 along the optical axis of the lens array 2 are all above a. Here, referring to Fig. 2, the 90% amplitude of the light amount distribution curve of the optical axis and the illumination device 5 will be described. The optical axis Z1 of the lens array 2 is a line connecting the original side focal point A of the lens array 2 and the sensor side focal point D. Further, the optical axis Z2 of the illumination device 5 is the optical axis of the light emitted from the illumination device 5, and as shown in Fig. 2, the height of the original document surface calculated by the original support (not shown) is also changed. When the light is projected on the document surface, the line connecting the peak position of the light amount distribution curve S of the reflected light in the direction perpendicular to the document surface 。 is formed. Instead, the sensor array 3 is placed on the sensor side focus -10- (8) (8) 1250782 D. Moreover, the 90% amplitude of the light quantity distribution curve of the illumination device 5 is on the intersection (reading point) of the optical axis Z1 and the document surface 〇 when the document surface is moved along the optical axis Z1 of the lens array 2. In the distribution curve I ( Z ) of the distribution of the illumination light intensity, the illumination light intensity is the movement range width W of the document surface 0 of 90% or more of the peak 値. The optical axis Z3 of the illumination device 6 and 90% of the light amount distribution curve are also the same. 〇 The reference points 5a and 5b have the same height in the optical axis direction of the lens array 2. Such a C I S unit is disposed below the transparent original document support 8 supporting the original. In the CIS unit according to the first embodiment, when the document is positioned near the focus A, the illumination lights of the illumination devices 5 and 6 are substantially equal; the original is illuminated by the sum of the lights. From this state, when the original is shifted toward the direction in which the focus A is closer to the lens array 2, the amount of illumination light of the illumination device 5 is increased, and the amount of illumination light of the illumination device 6 is decreased; the original is illuminated by the sum of these lights. Conversely, when the original is shifted toward the direction in which the focus A is farther from the lens array 2, the amount of illumination light of the illumination device 5 is decreased while the amount of illumination light of the illumination device 6 is increased; the original is illuminated by the sum of the lights. Therefore, regardless of which direction the original A is moved by the focus A along the optical axis Z 1 of the lens array 2, that is, regardless of the change in the height of the original from the original support 8, the illumination light amounts of the illumination devices 5 and 6 are changed to each other. Offset, the amount of combined light that is incident on the original is almost constant. As a result, -11 - (9) (9) 1250782 According to this embodiment, the concentration variation of the output image of the image reading device can be reduced. Next, the inventors of the present application actually produced a paper-feeding image reading apparatus having a c I S unit having the same structure as that of the first embodiment, and measured the result of the light amount distribution. In the paper-feeding image reading apparatus, the effective writing depth a of the lens array 2 is ±0.3 mm, the position variation width P at the time of paper feeding is 〇.6 mm, and the position of the original side focus A of the lens array 2 is The surface of the original support body 8 is at a point of 0.3 mm. At this time, the positional change of the original in the optical axis direction of the lens array 2 is such that the maximum is up 0 · 3 mm from the original side focus A. Accordingly, in this range, the variation of the illumination light quantity distribution must be small. Further, the distance between the optical axis Z1 and the reference point 5a in the illumination device 5 is smaller than the distance χ2 between the optical axis Z1 and the reference point 6a in the illumination device 6 by about 0·3 mm. Fig. 3 is a diagram showing the depth of the written boundary of the paper-feeding type image reading device (embodiment) produced as described above and the paper-feeding type image reading device (previous example) having the configuration shown in Fig. 8. Characteristics (lighting depth characteristics). Fig. 3 is a graph showing the relationship between the height dL from the surface of the original support 18 and various relative amounts of light. In the relative light amount distribution curve (· and the solid line) of the previous example, about 5% of the light amount fluctuation occurred in the range of ± 0.3 m m of the positional fluctuation range P of the original 槁. On the other hand, the amount of light in the relative light amount distribution curve (〇 and the solid line) of the examples fluctuated by about 2%, which was extremely small. -12- (10) (10) 1250782 The light quantity distribution of the embodiment is obtained by synthesizing the relative light amount distribution caused by the illumination device 5 and the relative light amount distribution by the illumination device 6, and is shown in FIG. The relative light amount is such that the light amount distribution of the illumination light of the illumination device 5, the light amount distribution of the illumination light of the illumination device 6, the light amount distribution obtained in the embodiment, and the light amount distribution obtained in the previous example are the maximum light amount. Relative amount of light. Fig. 4 is a graph showing the relationship between the height dL from the surface of the original support 18 and the relative amount of light based on the amount of light irradiated by one illumination device. In the previous example, since the focus positions of the two illumination devices are the same, the amount of peak light of the light quantity distribution obtained by combining them is about 2.0, but the sharpness of the light amount distribution is large. Therefore, the offset of the original position causes the amount of light to change rapidly. On the other hand, in the embodiment, the amount of peak light (1·9 1 ) is slightly smaller than that of the previous example, but the sharpness of the light amount distribution curve is small, and the change in the amount of light in the depth of the boundary of the lens array 2 is remarkably lowered. That is, even if the original position is shifted, the amount of light does not change much. Thus, the difference in the amount of light read is also small. Also, if the amount of light is 1. 9 1 ', very high speed reading is also possible. As described above, according to the first embodiment, the intersections B and C are slid from the document-side focus A of the lens array 2, so that the light amount distribution spring can be obtained. Moreover, when the depth of the write-on boundary of the lens array 2 is a, if the offset between the original-side focus A and the intersections B and C is a/2, '13-(11) 1250782 is applied to the illumination device 5 and The 90% of the light quantity distribution curve of each of the illumination lights is equal to or greater than a. Therefore, if the amount of the peak light of each of the illumination devices 5 and 6 is 1, the amount of light of the light irradiated on the original is at least 1. 8 . Therefore, a sufficient amount of light can be obtained, and high-speed reading becomes possible. On the other hand, it is suspense that if the offset size exceeds a/2, or the 90% amplitude of the light amount distribution curve does not reach a, even if the illumination light of the illumination device 5 and the illumination light of the illumination device 6 are added up, It is also impossible to obtain a sufficient peak light amount 〇 offset size as described above. When the depth of the written boundary is a, it is preferably within ± a / 2, but even in the range, even if there is slight variation, the same effect can be obtained. In other words, in the first embodiment, not only the intersection points B and C are slid from the document side focus A of the lens array U 2 , but also the magnitude of the offset and the light amount distribution curve of the illumination light of the illumination devices 5 and 6 are appropriately adapted. By specifying, it is possible to ensure a sufficient amount of combined light and to obtain a gentle light distribution curve. (Second embodiment) Next, a second embodiment of the present invention will be described. Fig. 5 is a cross-sectional view showing the structure of a CIS unit according to a second embodiment of the present invention. The same components as those in the first embodiment shown in Fig. 1 are assigned the same reference numerals. In the present embodiment, the height h1 of the reference point 5a from the surface of the sensor array 3 is lower than the height h2 of the reference point 6a from the surface of the sensor array 3. Further, in the present embodiment, the illumination device 5 is also configured by -14-(12)(12)1250782 such that the intersection B of the optical axis Z 2 and the optical axis Z1 is closer to the lens array 2 than the original-side focus A of the lens array 2. The illumination device 6 is also arranged such that its intersection C with the optical axis Z3 and the optical axis Z1 is farther from the lens array 2 than the original focus A of the lens array 2. Further, in the present embodiment, the illumination devices 5 and 6 are also arranged such that the distance between the focus A and the intersection B and the distance 'the distance A between the focus A and the intersection C are substantially equal. Further, if the effective writing depth of the lens array 2 is a, the distance between the focal point A and the intersection B, and the distance between the focal point A and the intersection C are both equal to or less than a/2. According to the second embodiment having such a configuration, the same effects as those of the first embodiment can be obtained. (Third embodiment) Next, a third embodiment of the present invention will be described. Fig. 6 is a cross-sectional view showing the structure of a CIS unit according to a third embodiment of the present invention. The same components as those in the first embodiment shown in Fig. 1 are assigned the same reference numerals. In this embodiment, the optical axis Z1 is at the same distance from the reference points 5a and 6a, and the heights of the reference points 5a and 6a of the surface of the sensor array 3 are also the same; however, the part of the frame 1 supporting the illumination device 5 Tilting inward, the portion of the frame 1 supporting the illumination device 6 is inclined outward. Therefore, the illumination devices 5 and 6 are rotated in the clockwise direction as compared with the first embodiment, and the optical axes Z2 and Z3 of the illumination light are also rotated in the clockwise direction. Therefore, the optical axis Z2 and the optical axis Z1 form an angle of -15- (14) (14) 1250782 wire 7.5 mechanically actuate to move the c IS unit 7 1 in the reading direction (scanning direction), and can be read A portrait of the original. The structure of the CIS unit 71 is a sensor unit in which the illumination unit is integrated; the light reflected by the light-irradiated original is collected by the photoelectric conversion element by the lens array (not shown) in the CIS unit 71, each The scan line is output as portrait information. In this way, the image information of the output page can be read. In the image scanner according to the fourth embodiment, since the CIS unit 171 is provided, it is less likely to be affected by the positional variation of the document paper and unevenness, and stable image information can be output. The inventors of the present application actually produced an image scanner having the same structure as that of the fourth embodiment; the density distribution of the read image obtained by the image scanner is significantly improved as compared with the prior art, and even when the document is uneven Good reading portraits. Further, since the amount of light is increased, even if the reading speed of the scanner is increased by about two times, a good image can be obtained. Next, the amount of light obtained by the structure (prior art) described in Patent Document 2 will be described. The first diagram shows a schematic diagram of the structure (prior art) described in Patent Document 2. Further, Fig. 1 is a graph showing the light amount distribution obtained by the structure shown in Fig. 10. With this configuration, in order to achieve the object of the invention described in Patent Document 2, the half-width of the light amount distribution curve of the illumination light is the same as the depth of the written-out depth a of the lens array 12 as the illumination device i 6 a And 1 6 b ; at the same time, the optical axis of the illumination light of each illumination device is shifted in the parallel direction of the optical axis of the lens array 2 from the focus A by a / 2 to determine the photo - 17 - (15) (15 ) 1250782 The height of the devices 16a and 16b. In the composite light quantity distribution curve (solid line in the second figure) obtained by such a structure, the shape of the peak becomes flat, and the variation in the amount of light on the original in the depth a of the writing boundary is improved by about 2%, and the shape of the peak is sharp. It is flattened to achieve flattening of the combined light quantity distribution. However, even if the light source of the two systems is used, as shown in Fig. 1, the amount of combined light is only increased by 5% when compared with the light source. Therefore, according to the invention described in Patent Document 2, when the height of the irradiation device of each optical axis is moved only in consideration of the flattening of the combined light amount distribution, the amount of combined illumination light on the original is not sufficient for high-speed reading. Industrial Applicability According to the present invention, it is possible to obtain a high amount of light to be irradiated and to suppress variations in the amount of reading light accompanying fluctuations in the height of the document. Therefore, it is possible to speed up the reading speed in the image reading device such as a scanner. Moreover, the concentration distribution of the read image can be reduced within the depth range of the written boundary. Therefore, it is quite useful for an image reading apparatus such as a high speed scanner. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing the structure of a CIS unit according to a first embodiment of the present invention. Fig. 2 is a schematic view showing a 90% amplitude of the optical axis distribution curve of the optical axis and the illumination device 5. Fig. 3 is a graph showing the relationship between the height -18-(16) (16) 1250782 dL from the surface of the original support 18 and various relative amounts of light. Fig. 4 is a graph showing the relationship between the height dL from the surface of the original support 18 and the relative amount of light based on the amount of light irradiated by one illumination device. Fig. 5 is a cross-sectional view showing the structure of a CIS unit according to a second embodiment of the present invention. Fig. 6 is a cross-sectional view showing the structure of a CIS unit according to a third embodiment of the present invention. Fig. 7 is a perspective view showing the appearance of a platform type image scanner according to a fourth embodiment of the present invention. Fig. 8 is a cross-sectional view showing the structure of a conventional CIS unit. Fig. 9 is a cross-sectional view showing a high-speed paper-feeding type image reading apparatus using a conventional CIS unit. Fig. 10 is a schematic view showing a structure (prior art) described in Patent Document 2. Fig. 1 is a graph showing the distribution of the light amount obtained by the configuration shown in Fig. 1 . [Main component symbol description] 1 Frame 2 Lens array 3 Sensor array 4 Sensor substrate 5 Lighting device -19-

Claims (1)

(1) (1) 1250782 X. Patent application scope 1. An image sensor unit having first and second illumination devices for illuminating a document, and imaging means for imaging reflected light from a document, and having a plurality of image forming means An image sensor unit for converting the reflected light into a sensor array of an electrical signal; wherein the first and second illumination devices are disposed face to face on both sides of the imaging means; When the effective depth of the means is a written depth, the 90% amplitude of the light quantity distribution curve of each illumination device along the optical axis of the imaging means is above a; the optical axis of the outgoing light of the first illumination device and the imaging means The first intersection of the optical axis is closer to the imaging means than the original side focus of the imaging means; and the second intersection of the optical axis of the second illumination device and the optical axis of the imaging means is The document side focus of the image forming means is away from the position of the image forming means; and the distance between the first and second intersections and the document side focus is equal to or less than a / 2. 2. The image sensor unit according to claim 1, wherein the distance between the first and second illumination devices and the imaging means is different in a direction perpendicular to an optical axis of the imaging means. The image sensor unit according to claim 1, wherein the first and second illumination devices in the parallel direction of the optical axis of the imaging means are provided. The location is different. 4. The image sensor unit according to claim 1, wherein the optical axes of the illumination light of the first and second illumination devices are different from the optical axes of the imaging means. The image sensor unit according to claim 1, wherein the distance between the first and second intersections and the document side intersection is substantially equal. 6. An image reading apparatus comprising: first and second illumination devices for illuminating a document; imaging means for imaging reflected light from the document; and a plurality of pixels for converting the reflected light into an electrical signal An image reading device of the image sensor unit of the sensor array; wherein the first and second illumination devices are disposed face to face on both sides of the imaging means; if the imaging means is effectively written When the depth is a, the 90% of the light quantity distribution curves of the illumination devices along the optical axis of the imaging means are all above a; the optical axis of the outgoing light of the first illumination device and the optical axis of the imaging means 1 intersection point, closer to the position of the imaging means than the original side focus of the above imaging means; -22- (3) (3) 1250782 The optical axis of the outgoing light of the second illumination device and the optical axis of the imaging means The second intersection is located farther from the image forming means than the original side focus of the image forming means; and the distance between the first and second intersections and the document side focus is equal to or less than a / 2The image reading device according to claim 6, wherein the distance between the first and second illumination devices and the imaging means is different in a direction perpendicular to an optical axis of the imaging means. The image reading device according to claim 6, wherein the position of the first and second illumination devices in the parallel direction of the optical axis of the imaging means is different. The image reading device according to claim 6, wherein the optical axes of the illumination light of the first and second illumination devices are different from the optical axes of the imaging means. The image reading device according to claim 6, wherein the distance between the first and second intersections and the intersection of the document sides is substantially equal.