JP5239232B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus and an image forming apparatus used for a digital copying machine and an image scanner.

  In recent years, light emitting diodes (hereinafter referred to as LEDs) are being actively developed, and the brightness of LED elements is rapidly increasing. LEDs generally have advantages such as long life, high efficiency, high G resistance, and monochromatic light emission, and are expected to be applied in many lighting fields. As one of such applications, an LED is used in a document illumination device of an image reading apparatus such as a digital copying machine or an image scanner.

  Various methods have been proposed for using LEDs used in image reading apparatuses. For example, in Patent Documents 1, 2, and 4, a large number of LEDs are arranged in parallel to the main scanning direction of the document, and the emitted light from the LEDs is diffused without giving an optical action in the main scanning direction, and the sub-scanning direction In FIG. 2, the illuminance in the reading target area on the document surface is increased by the light collecting action of the reflecting surface. Further, in Patent Document 3, a large number of LEDs are arranged in parallel with the main scanning direction of the document, and the emitted light from the LEDs is diffused without giving an optical action in the main scanning direction, and in the sub-scanning direction, the lens is arranged. The illuminance in the reading target area on the document surface is increased by the light condensing action.

  Now, what kind of illuminance or illuminance distribution is required on the document surface will be described. As shown in FIG. 9, an image reading device used in a digital copying machine or an image scanner is a device that inputs information described in a document to an image sensor such as a CCD through a reading lens. FIG. 10 is a top view of the original surface of FIG. 9 viewed from above. In a state where the optical system is fixed, the image reading apparatus is in a state in which only information on the elongated reading target area 41 shown in FIG. 9 is moved, or the reading target area 41 is moved in the direction of the arrow in FIG. 10 by moving the illumination optical system and the folding mirror in conjunction with each other. By sequentially inputting information to the image sensor 49 while moving the reading target area 41, it is possible to read the entire original. In FIG. 9, reference numeral 42 denotes an original surface, 43 denotes an illumination lamp, 45 to 47 denote folding mirrors, 48 denotes a reading lens, and 50 denotes an optical axis.

  At this time, regarding the illuminance on the document surface, if the reading target area 41 of FIG. 10 is moved at high speed to shorten the reading time per document, the amount of light input to the image sensor 49 per unit time is calculated. Higher illuminance is desirable because it is required to increase. From this point of view, a method of regulating light in the sub-scanning direction as in Patent Documents 1 to 4 is appropriate.

  As for the illuminance distribution, a uniform illuminance distribution is generally desired. FIG. 11 is a diagram showing a conjugate relationship between the document surface 42 and the image sensor 49, and shows an example of the illuminance distribution on the document surface with a solid line and a dotted line. The solid line in the figure is the illuminance distribution on the document surface at a certain point in time, and the dotted line is the illuminance distribution that fluctuates at a certain moment due to the influence of external vibrations. As shown by the solid line or dotted line in the figure, if the illuminance distribution on the document surface is uneven, the position where the illuminance is high on the document surface is high at the corresponding position on the imaging surface, and vice versa. It is. If the relationship between the original and the illumination is always the same during the period in which the reading target area 41 is moved in the direction of the arrow in FIG. 10 and the entire original is read, such uneven illuminance distribution can be corrected by image processing.

  However, if the relationship between the original and the illumination during this period changes from a solid line state to a dotted line state instantaneously, density unevenness occurs in the read image, and the image quality deteriorates. Therefore, in general, as shown in FIG. 12, it is desirable that the entire reading target region 41 has a uniform illuminance distribution. If the illuminance distribution is uniform, the illuminance distribution on the imaging surface does not change even if the positional relationship between the document and the illumination is shifted due to vibration from the outside. As described above, in any case of Patent Documents 1 to 4, the method of uniforming the illuminance distribution in the main scanning direction is a method of diffusing as it is without giving any optical action to the light from the point light source called LED. Met.

JP 2006-67551 A Japanese Unexamined Patent Publication No. 2006-4416 Japanese Patent Laid-Open No. 2005-311662 JP 2005-241681 A

However, in any of the above-described Patent Documents 1 to 4, when the number of light sources is small, a long distance is required from the light sources to the document surface, and the illumination optical system from the light source to the document surface tends to be large. It was. Increasing the number of light sources in order to reduce the size of the illumination optical system has the advantage of improving illuminance and further reducing the size, but has the disadvantage of high cost and high power consumption.
Accordingly, an object of the present invention is to provide an image reading apparatus and an image forming apparatus having a small illumination optical system with a small number of light sources in order to solve the above problems.

  In order to solve the above-described problems, the image reading apparatus of the present invention is controlled by an optical member so as not to diffuse light emitted from the LED in the sub-scanning direction. In the main scanning direction, the illuminance unevenness in the main scanning direction is eliminated by diffusing in the optical member in the same manner as in Patent Documents 1 to 4, but the light entrance and the light exit to the optical member are made common. In the present invention, this is called a light passage opening. The emitted light is reflected at least once in the optical member, thereby doubling the optical path length of the illumination light inside the optical member. Therefore, it is possible to increase the optical path length without changing the distance from the light source to the document surface.

In other words, the image reading apparatus of the invention of claim 1 is one or a plurality of light emitting diodes, a light source for irradiating light on a document surface, and a reading object having a length and a width of light emitted from the light source. An illumination optical system that leads to an area; an imaging optical system that forms an image of light reflected from the document surface ; and a sensor that is provided in an imaging unit of the imaging optical system and reads an image on the document surface. The light emission direction of the emitted light having the highest light intensity out of the emitted light from the light source is emitted in a direction away from the reading target region substantially parallel to the document surface, and the illumination optical system is light has an optical member for regulating the diffusion of the plurality of reflecting members, all said reflecting surface having the optical member is a flat shape, the optical member disposed on at least both ends in the main scanning direction of the image reading apparatus Reflective surface and one light The light source light emitted from the light source is incident on the optical member through the light passage opening and is emitted from the light passage opening, and the member installation area of the illumination optical system is perpendicular to the document surface. When divided into two sections by a virtual plane parallel to the length direction and passing through the reading target area, the plurality of reflecting members are installed at least one in each section, and the plurality of reflecting members The reading target area is illuminated from different directions by reflected light of light emitted from the light passage opening .

According to a second aspect of the present invention, there is provided the image reading apparatus according to the first aspect , wherein the light emitting diode is a one-chip type white light emitting diode using a phosphor.

According to a third aspect of the present invention, there is provided the image reading device according to the first aspect , wherein the light emitting diode is a white light emitting diode that emits white light by color mixing using two or more chips having different light emission colors. It is characterized by that.

According to a fourth aspect of the present invention, there is provided the image reading apparatus according to any one of the first to third aspects, wherein the light emitting diode is mounted on a circuit board, and a sheet having a high surface reflectance is mounted on the mounting surface of the circuit board. Is pasted.

An image reading apparatus according to a fifth aspect of the present invention is the image reading apparatus according to any one of the first to third aspects, wherein the light-emitting diode is mounted on a circuit board, and the mounting surface of the circuit board increases surface reflectivity by coating. It is characterized by.

An image reading apparatus according to a sixth aspect of the present invention is the image reading apparatus according to any one of the first to fifth aspects, wherein the optical member includes a plurality of mirrors.

According to a seventh aspect of the present invention, there is provided the image reading apparatus according to any one of the first to fifth aspects, wherein the optical member is mirror-finished on the surface of a molded product made of an arbitrary material.

An image reading apparatus according to an eighth aspect of the present invention is the image reading apparatus according to the seventh aspect , wherein the arbitrary material is plastic.

An image reading apparatus according to a ninth aspect of the present invention is the image reading apparatus according to the seventh aspect , wherein the mirror finish is a coating that improves surface reflectivity.

According to a tenth aspect of the present invention, in the image reading apparatus according to the ninth aspect , the coating is an aluminum coating.

An image reading apparatus according to an eleventh aspect of the present invention is the image reading apparatus according to the seventh aspect , wherein the mirror finish is a polishing process.

An image reading apparatus according to a twelfth aspect of the invention is characterized in that, in the image reading apparatus of the seventh aspect , the mirror finish is pasting a sheet having a high surface reflectance on a part or all of the surface of the molded product. To do.

An image reading apparatus according to a thirteenth aspect of the present invention is the image reading apparatus according to any one of the first to twelfth aspects, wherein the optical member includes a pair of opposing reflecting plates, and the set of opposing reflecting plates is from a light source. It is characterized in that the distance between the reflecting plates on the side where no light is incident / exited is smaller than the distance between the reflecting plates on the light passing port side where light is incident / exited.

According to a fourteenth aspect of the present invention, in the image reading apparatus according to any one of the first to fifth aspects, the optical member is a molded article made of a transparent optical material.

An image reading apparatus according to a fifteenth aspect of the present invention is the image reading apparatus according to the fourteenth aspect , wherein the optical material is glass.

An image reading apparatus according to a sixteenth aspect is the image reading apparatus according to the fourteenth aspect , wherein the optical material is plastic.

An image reading apparatus according to a seventeenth aspect of the present invention is the image reading apparatus according to any one of the fourteenth to sixteenth aspects, wherein the optical member is a light guide having at least two planes, and the two planes are arranged to face each other. The two surfaces arranged opposite to each other have a smaller distance between the reflecting plates on the side where no light is incident / exited than the distance between the reflecting plates on the light passing port side where the light from the light source is incident / emitted. It is arranged so that it may be arranged.

Image reading apparatus of the invention 請 Motomeko 18, in any one of the image reading apparatus according to claim 14 or 17, characterized in that the light passage opening is curved.

An image forming apparatus according to a nineteenth aspect includes the image reading apparatus according to any one of the first to eighteenth aspects.

  As described above, according to the present invention, the number of light sources of the illumination optical system in the image reading apparatus and the image forming apparatus is reduced and the size is reduced. Further, the unevenness of illuminance in the main scanning direction is reduced, and the quality of the read image is improved. improves.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a first embodiment according to the image reading apparatus of the present invention will be described. FIG. 1 is a cross-sectional view in the sub-scanning direction showing the configuration of the first embodiment, and FIG. 2 is a cross-sectional view in the main scanning direction showing the configuration of the first embodiment. In the figure, reference numeral 1 denotes an LED, which is arranged on a circuit board 2. A reflection sheet 3 is laid on the surface of the circuit board 2. Reflecting plates 4 to 8 are disposed on the front side where the LED 1 is irradiated. Further, reflectors 9 and 10 are disposed on the back side of the LED 1. The reflecting surfaces of the reflecting plates 4 to 8 are all flat and are joined by an adhesive to form a box-shaped optical member 15.

  In FIG. 1, the length direction is a direction perpendicular to the drawing, and the width direction is the left-right direction of the drawing. The virtual plane is a plane that is perpendicular to the document surface (contact glass 11) and parallel to the length direction and passes through the reading target region 12. That is, a surface through which light reflected from the original and used for image formation passes is defined as a virtual plane 13. Further, when the installation area of the light source and the illumination optical system member is divided into two sections by the virtual plane 13, the section where the light source (LED1) exists is the first area 39, and the section where the light source does not exist is the second section. Region 40 is assumed. The optical path that passes through the virtual plane 13 and is input to the image sensor such as a CCD through the reading lens is described in FIG. 9 in the background art section, and thus illustration and description thereof are omitted.

  A specific example in this embodiment will be described with reference to FIG. In FIG. 1, the virtual plane 13 is a surface serving as a boundary between the first region 39 and the second region 40, and the first region 39 includes the LED 1, an optical member composed of the reflectors 4 to 8, and The reflector 9 is disposed, and the reflector 10 is disposed in the second region 40. In the second to fourth embodiments to be described later, the virtual plane 13, the first region 39, and the second region 40 are used in the same definition as in the present embodiment. More specifically, in the arrangement configuration of the virtual plane 13, the first region 39, and the second region 40, it is the same as this embodiment except that the type of the optical member is changed.

  Here, the configuration of the image reading apparatus according to the first embodiment will be described. As shown in FIG. 1, the LED 1 is installed such that the light emission direction is parallel to the contact glass 11. The light emitted from the LED 1 enters the optical member 15 from the light passage port 14. The light incident on the optical member 15 is reflected on a plurality of surfaces such as the reflecting plate 4, the reflecting plates 4 and 5, or the reflecting plates 4 and 6 in the sub-scanning direction, and then is emitted from the light passage port 14 to be reflected by the reflecting plate 9. Alternatively, the reading target area 12 is illuminated through the reflector 10 or directly.

  The distance between the end of the reflecting plate 5 and the end of the reflecting plate 6 facing each other is smaller than the distance A between the reflecting plates on the light passing port 14 side, and the distance B between the reflecting plates on the side where no light is incident / exited. In such a manner, they are arranged at an angle so that the front end side opens. A reflective sheet 3 is attached on the circuit board 2. If no processing is performed on the circuit board 2, the light directed toward the document surface (contact glass 11) is simply blocked by installing the circuit board 2 on which the LED 1 is mounted in the vicinity of the light passage opening 14. Therefore, an object of the present invention is to return the light emitted from the light passage opening 14 by the reflection sheet 3 to the optical member 15 again and to pass the optical path used for illumination.

  On the other hand, the light that diffuses because it cannot receive an optical action in the main scanning direction, but escapes to the outside of the reflecting plate 5 and the reflecting plate 6 facing each other, is folded back by the reflecting plate 7 and the reflecting plate 8, and the original Effectively used for illumination of the surface (contact glass 11). In order to make the illuminance unevenness in the main scanning direction uniform even with a small number of LEDs 1, a distance for sufficiently diffusing light is necessary in the front direction (left and right direction in FIG. 2) of the light emitting surface of the LED 1. . As in this embodiment, the light source light of the LED 1 is emitted in a direction away from the reading target region 12 and is folded back by the reflectors 4 to 10, so that the optical path length is doubled in the optical member 15 even in the same space. Is possible.

  As for the sub-scanning direction, the light emitting direction of the LED 1 is parallel to the document surface (contact glass 11), the light is regulated in the sub-scanning direction by the optical member 15, and the light is lifted up by the mirror. In the up-and-down direction of 1, it becomes possible to set it as a compact structure. Further, since illumination is performed from two directions, no shadow is produced even if the bonded original is lifted.

Then, the illuminance distribution in the sub-scanning direction is optimized by adjusting the angle of the reflectors 4 to 10 while taking into consideration the light distribution of the LED 1, for example, a flat illuminance distribution of about 3 mm in the vicinity of the reading target region. Such adjustments can be made. At this time, by providing the reflecting plates 4 to 10 with a curvature, the degree of freedom in design increases, and a more desirable light amount distribution can be formed. In FIG. 1, the light emission direction of the LED 1 is indicated by a thick arrow. FIG. 1 shows that B <A. That is, a pair of the reflecting plate 5 and the reflecting plate 6 are arranged on the side where no light is incident / exited with respect to the distance A between the end portions of the reflecting plate on the light passing port 14 side where light from the light source is incident / exited. The reflection plate is arranged so that the distance B between the end portions of the reflector becomes small.

  Next, a second embodiment according to the image reading apparatus of the present invention will be described. FIG. 3 is a sectional view in the sub-scanning direction showing the configuration of the second embodiment, and FIG. 4 is a sectional view in the main scanning direction showing the configuration of the second embodiment. The second embodiment has the same configuration as that of the first embodiment except for the optical member. The difference is that the optical member is replaced with an optical member 17 made of a plastic molded product. As shown in FIGS. 3 and 4, a reflection sheet 18 is attached to the optical member 17 made of a plastic molded product on the inside to form a reflection surface. By replacing the optical member with a molded product, the weight can be reduced as compared with the optical member 15 using the reflecting plate of the first embodiment.

  In the configuration of the first embodiment, as shown in FIG. 1, the optical member 15 has an effect of bringing light emitted from the optical member 15 closer to parallel light by expanding the light passage port 14 side as compared with the reflecting plate 4 side. . On the other hand, in the second embodiment, assuming that the space in which the illumination optical system can be installed is limited in the image reading apparatus, the U-shape is set as shown in FIG. For this reason, since there is no merit of installing the light source near the center of the light passage opening, the circuit board 21 on which the LED 19 is mounted and the reflection sheet 20 is laid is not the center of the light passage opening 22 shown in FIG. Installed in the department. Of course, even a plastic molded product can have the same configuration as that of the first embodiment.

  In addition, the installation position of the circuit board 21 and the angle with respect to the optical member 17 are adjusted while observing the actual illumination device and the optical simulation result so that the illuminance distribution on the document surface (contact glass 11) is in an optimal state. It is desirable.

  FIG. 5 is a cross-sectional view in the sub-scanning direction showing a case where a part of FIG. 3 is changed. The illustrated example is an example in which the circuit board 21 is installed obliquely with respect to the optical member 17. By tilting the angle of the circuit board 21, it is possible not only to change the behavior of light inside the optical member 17, but also to adjust the balance of the amount of light entering each of the reflector 9 and the reflector 10. become.

  Next, a third embodiment according to the image reading apparatus of the present invention will be described. FIG. 6 is a cross-sectional view in the sub-scanning direction showing the configuration of the third embodiment, and FIG. 7 is a cross-sectional view in the main scanning direction showing the configuration of the third embodiment. The third embodiment has the same configuration as that of the first embodiment except for the optical member, and the difference is that the optical member is replaced with an optical member 24 made of a transparent plastic molded product. The optical member 24 made of a transparent plastic molding is provided with aluminum coatings 27 and 28 as shown in FIG. 6 on the surface facing the light passage 25 and the paraboloid 26. Light incident on the optical member 24 from the light source 25 from the light source is reflected on the surface on which the aluminum coatings 27 and 28 are applied, and is restricted by total reflection on the other surfaces.

  As shown in FIG. 6, the optical member 24 is set to have a flat bottom surface and a top surface that is wide on the side of the light passage opening 25 for the purpose of increasing the parallelism of light emitted from the light passage opening 25. It is what. In this embodiment, no reflective sheet is attached to the circuit board 30 that holds the LEDs 29. This is because the case where the cost concerning a reflective sheet did not match the effect was assumed. In this case, the surface reflectance can be increased by coating the surface of the circuit board 30. Moreover, it is preferable that the part which gave the aluminum coatings 27 and 28 of the surface of the optical member 24 is mirror-finished by grinding | polishing. The material of the optical member 24 can be glass.

  Next, a fourth embodiment according to the image reading apparatus of the present invention will be described. FIG. 8 is a sectional view in the sub-scanning direction showing the configuration of the fourth embodiment. The fourth embodiment has the same configuration as the third embodiment except for the optical member, and the difference is that the shape and coating of the optical member made of a molded product in the third embodiment are replaced. As shown in FIG. 8, the light passage port 32 of the optical member 31 was formed into a curved surface. In this way, when the light from the LED 37 is once condensed in the optical member 31 and the condensing point is handled as a secondary light source, it is reflected by any of the aluminum coatings 34 to 36 shown in FIG. Light can be emitted from the light passage port 32 with high parallelism. In the fourth embodiment, the surface on which the aluminum coatings 34 to 36 are applied is a flat surface, but it can also be a parabolic surface where the secondary light source is in focus.

  In addition, the LED in each embodiment mentioned above may be one installation or several installation. The LED can also be a one-chip white light emitting diode using a phosphor. Furthermore, as the LED, it is also possible to use a white light emitting diode that emits white light by mixing two or more types of chips that emit different colors.

1 is a cross-sectional view in the sub scanning direction of a first embodiment of an image reading apparatus of the present invention. 1 is a cross-sectional view in the main scanning direction of a first embodiment of an image reading apparatus of the present invention. It is sectional drawing of the subscanning direction of 2nd Embodiment of the image reading apparatus of this invention. FIG. 6 is a cross-sectional view in the main scanning direction of a second embodiment of the image reading apparatus of the present invention. FIG. 4 is a sectional view in the sub-scanning direction showing a case where a part of FIG. FIG. 6 is a cross-sectional view in the sub-scanning direction of a third embodiment of the image reading apparatus of the present invention. FIG. 6 is a cross-sectional view in the main scanning direction of a third embodiment of the image reading apparatus of the present invention. FIG. 10 is a cross-sectional view in the sub-scanning direction of a fourth embodiment of the image reading apparatus of the present invention. It is a figure which shows a prior art example. It is a figure which shows a prior art example. It is a figure which shows a prior art example. It is a figure which shows a prior art example.

Explanation of symbols

1 LED
DESCRIPTION OF SYMBOLS 2 Circuit board 3 Reflective sheet 4-8 Reflector 9,10 Reflector 11 Contact glass 12 Reading object area | region 13 Virtual plane 14 Light passage 15 Optical member 17 Optical member 18 Reflective sheet 19 LED
20 Reflective sheet 21 Circuit board 22 Light passage port 24 Optical member 25 Light passage port 26 Parabolic surface 27, 28 Aluminum coating 29 LED
30 Circuit board 31 Optical member 32 Light passage 34-36 Aluminum coating 37 LED
38 Circuit board 39 First area 40 Second area

Claims (19)

One or a plurality of light emitting diodes, and a light source for irradiating the document surface with light;
An illumination optical system for guiding light emitted from the light source to a reading target region having a length and a width;
An imaging optical system for imaging light reflected from the document surface;
In the image reading apparatus having a sensor for reading an image of the document surface is provided on the imaging unit of the imaging optical system,
The light emission direction of the emitted light having the strongest light intensity among the emitted light from the light source is emitted in a direction away from the reading target area substantially parallel to the document surface,
The illumination optical system has an optical member that regulates diffusion of light and a plurality of reflecting members,
All of the reflecting surfaces of the optical member have a planar shape,
The optical member has at least reflection surfaces provided at both ends in the main scanning direction of the image reading apparatus and one light passage opening, and light source light emitted from the light source is emitted from the light passage opening to the optical element. Entering the member and exiting from the light passage opening ,
When the member installation area of the illumination optical system is divided into two sections by a virtual plane that is perpendicular to the document surface and parallel to the length direction and passes through the reading target area, the plurality of reflecting members At least one in each compartment,
An image reading apparatus that illuminates the reading target region from different directions by reflected light of light emitted from the light passage port by the plurality of reflecting members . The image reading apparatus according to claim 1 ,
The image reading apparatus according to claim 1, wherein the light emitting diode is a one-chip type white light emitting diode using a phosphor. The image reading apparatus according to claim 1 ,
2. The image reading apparatus according to claim 1, wherein the light emitting diode is a white light emitting diode that emits white light by color mixture using two or more kinds of chips that emit different colors. The image reading apparatus according to any one of claims 1 to 3 ,
The light-emitting diode is mounted on a circuit board, and a sheet having a high surface reflectance is attached to a mounting surface of the circuit board. The image reading apparatus according to any one of claims 1 to 3 ,
2. The image reading apparatus according to claim 1, wherein the light emitting diode is mounted on a circuit board, and the mounting surface of the circuit board has a surface reflectance increased by coating. The image reading apparatus according to any one of claims 1 to 5 ,
The image reading apparatus, wherein the optical member includes a plurality of mirrors. The image reading apparatus according to any one of claims 1 to 5 ,
An image reading apparatus, wherein the optical member is mirror-finished on the surface of a molded product made of an arbitrary material. The image reading apparatus according to claim 7 .
The image reading apparatus, wherein the arbitrary material is plastic. The image reading apparatus according to claim 7 .
The image reading apparatus according to claim 1, wherein the mirror finish is a coating that improves surface reflectance. The image reading apparatus according to claim 9 .
An image reading apparatus, wherein the coating is an aluminum coating. The image reading apparatus according to claim 7 .
The image reading apparatus according to claim 1, wherein the mirror finish is a polishing process. The image reading apparatus according to claim 7 .
The mirror reading is characterized in that a sheet having a high surface reflectance is attached to a part or all of the surface of a molded product. The image reading apparatus according to any one of claims 1 to 12 ,
The optical member includes a pair of opposing reflectors, and the pair of opposing reflectors is incident / exited with respect to the distance between the reflectors on the light passage opening side where light from the light source is incident / exited. An image reading apparatus, wherein the distance between the reflection plates on the side where there is no light is arranged to be small. The image reading apparatus according to any one of claims 1 to 5 ,
The image reading apparatus, wherein the optical member is a molded product made of a transparent optical material. The image reading apparatus according to claim 14 .
The image reading apparatus, wherein the optical material is glass. The image reading apparatus according to claim 14 .
An image reading apparatus, wherein the optical material is plastic. The image reading device according to any one of claims 14 to 16 ,
The optical member is a light guide having at least two planes, the two planes are arranged to face each other, and the two planes arranged to face each other are on the side of the light passage where light from a light source enters and exits An image reading apparatus, wherein the distance between the reflection plates is arranged such that the distance between the reflection plates on the side where no light enters or exits is small. The image reading device according to any one of claims 14 to 17 ,
The image reading apparatus, wherein the light passage opening has a curved surface. An image forming apparatus, comprising an image reading apparatus according to any one of claims 1 to 18.