JP2012109876A - Image reading device and image-forming mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce deformation due to a temperature rise of image-forming mirrors in an image-forming optical system comprised of the image-forming mirrors each having an off-axial reflective surface formed thereon.SOLUTION: An image reading device includes reading means for reading an image, and image-forming means for allowing the reading means to form an image. The image-forming means includes image-forming mirrors, each of which is provided with an off-axial reflective surface having a curvature, in which an incident direction and an emission direction of a reference axis ray are different from each other. The image-forming mirrors 6, 7, 8, and 9 have first metal layers 6b, 7b, 8b, and 9b on one surface of mirror bases 6a, 7a, 8a, and 9a, respectively. The off-axial reflective surfaces 6c, 7c, 8c, and 9c are formed on surfaces of these first metal layers, respectively. These image-forming mirrors have second metal layers 6d, 7d, 8d, and 9d on the rear surface of these off-axial reflective surfaces, respectively.

Description

  The present invention relates to an image reading apparatus that reads a document by illuminating a document with a light source device and forming an image with an imaging unit on a photoelectric conversion unit.

  In recent years, in image reading apparatuses such as digital copying machines, image reading employing a non-coaxial optical system (off-axial optical system) that forms an image by reflecting image light as a means for achieving both high image quality and miniaturization. A device has been proposed. In such an off-axial optical system, the off-axial reflecting surface is required to have a highly accurate free-form surface shape, and therefore slight deformation accompanying a rise in temperature of the imaging mirror greatly affects the optical performance.

  In view of this, there has been disclosed a device for preventing the deformation of the imaging mirror by the configuration of the fixed portion of the imaging mirror (see Patent Document 1). These reduce the deformation of the imaging mirror due to the difference in thermal expansion between the mirror restraint points of the mirror holding member for fixing the imaging mirror and the thermal expansion coefficient between the restrained points of the imaging mirror.

  Further, Patent Document 2 discloses a device in which an air blowing unit is provided and cooled in order to suppress a temperature rise of the reflection imaging optical system.

JP 2004-126448 A JP 2004-93655 A

  In Patent Document 1, in an imaging mirror in which a metal layer is formed as an image light reflecting surface on the surface of a resin imaging mirror base, the imaging mirror itself is not affected by the action of bimetal due to the temperature rise of the imaging mirror itself. Deformation could not be prevented. Further, in Patent Document 2, it is difficult to cool a plurality of image forming mirrors according to respective temperature rises. For example, even in one image forming mirror, a cooling effect is obtained on the side close to and far from the blowing unit. Due to the difference, partial thermal deformation may occur.

  An object of the present invention is to provide an image reading apparatus equipped with an off-axial optical system that suppresses thermal deformation of an imaging mirror and reduces optical performance.

  In order to solve the above problems, the present invention has the following configuration. That is, the image reading device includes a reading unit that reads an image and an imaging unit that forms an image on the reading unit, and the imaging unit includes an imaging mirror having a curved reflecting surface, The imaging mirror has a first metal layer on one surface of a mirror base, the reflection surface is formed on the surface of the first metal layer, and a second metal layer is formed on the back surface of the reflection surface. .

  Moreover, this invention has the following structure as another embodiment. That is, an imaging mirror in which an off-axial reflecting surface having a curvature different from an incident direction and an emitting direction of a reference axis ray is formed, and has a first metal layer on one surface of the mirror base, An off-axial reflective surface is formed on the surface of the metal layer, and a second metal layer is provided on the back side surface of the off-axial reflective surface.

  According to the present invention, distortion can be suppressed by reducing the bimetal deformation of the imaging mirror itself due to temperature rise. As a result, the deformation of the reflecting surface of the imaging mirror becomes smaller than before, and the deterioration of the imaging performance due to the temperature rise can be suppressed to a low level.

  In addition, the action of the heat transfer layer increases the speed at which the temperature difference between the metal layers on the front and back of the imaging mirror is eliminated. As a result, it is possible to eliminate the deterioration in imaging performance caused by deformation due to partial thermal expansion of the imaging mirror in a shorter time.

  In addition, since the radiant heat (infrared rays) from the elements on the electric circuit serving as the heat source is reflected by the metal layer provided on the side facing the heat source of the imaging mirror, the thermal expansion on the side facing the heat source of the imaging mirror However, it becomes small compared with the case where there is no metal layer. For this reason, it is possible to suppress a decrease in imaging performance caused by deformation due to partial thermal expansion of the imaging mirror.

1 is a cross-sectional view showing a schematic configuration of an image reading apparatus according to the present invention. The upper view which expanded a part of schematic structure of this invention shown in FIG. The perspective view which expanded a part of schematic structure of this invention shown in FIG. FIG. 3 is a configuration explanatory diagram of an off-axial optical system according to the first embodiment. FIG. 9 is a configuration explanatory diagram of an off-axial optical system according to a second embodiment.

<First embodiment>
As a first embodiment according to the present invention, an example applied to an image reading apparatus mounted on an electrophotographic copying machine will be specifically described with reference to the drawings. Note that since the configuration and function of the image forming apparatus for recording information of the read image in the image reading apparatus are known, the description thereof is omitted.

[Equipment structure]
FIG. 1 is a main cross-sectional view of an embodiment when the present invention is applied to an apparatus such as an image scanner or a copying machine implementing the image reading apparatus of the present invention. FIG. 2 is a view of the carriage 12 of FIG. 1 as viewed from above. Here, the upper side is the side on which the document S is placed.

  The document S is placed on the document table glass 1 in FIG. The illumination light source 2 is composed of, for example, a xenon lamp. The reflection mirrors 3, 4, and 5 are first, second, and third reflection mirrors, respectively, and bend the optical path of the light beam from the document S. The imaging mirrors 6 to 9 are first to fourth imaging mirrors each having only one off-axial reflecting surface. These first to fourth imaging mirrors 6 to 9 fold the light beam based on the image information of the document S and form an image on the photoelectric conversion element 10 serving as a reading unit with air as a medium. The first to fourth imaging mirrors 6 to 9 are formed of a resin such as PC (polycarbonate). The off-axial reflection surface is a curved reflection surface in which the incident direction and the emission direction of the reference axis light beam are different, and has a predetermined curvature on the reflection surface. A photoelectric conversion element (CCD) 10 serving as a reading unit has a configuration in which a plurality of light receiving elements are arranged in a one-dimensional direction (main scanning direction). The housing 11 is a housing of the carriage 12 that houses the illumination light source 2, the first to third reflecting mirrors 3 to 5, the first to fourth imaging mirrors 6 to 9, and the CCD 10. The casing 11 is integrally formed with a lamp support portion 11a, a reflection mirror support portion 11c, and an imaging mirror support portion 11e. Here, the illumination light source 2 is directly connected to the lamp support 11a, the first to third reflection mirrors 3 to 5 are directly connected to the reflection mirror support 11c, and the first to fourth image formation mirrors 6 to 9 are directly connected to the image formation mirror support 11e. Positioned and fixed. The drive motor 13 is a means for moving the carriage 12 in the direction of arrow A shown in FIG. 1 via the drive belt 14 connected to the housing 11 and the drive motor 13 when reading the document S. The carriage 12 is moved to a predetermined reading start position by the drive motor 13.

  In the present embodiment, the light beam emitted from the illumination light source 2 illuminates the document S, and the reflected light beam from the document S passes through the first to third reflecting mirrors 3 to 5 in the carriage 12 through the optical path of the light beam. Bending is further performed by the first to fourth imaging mirrors 6 to 9. As a result, a light beam is imaged on the CCD 10 surface. Then, the image information of the document S is read by moving the carriage 12 in the direction of arrow A (sub-scanning direction) by the drive motor 13.

  FIG. 3 is an enlarged perspective view of a portion where the first to fourth imaging mirrors 6 to 9 in FIGS. 1 and 2 are fixed to the imaging mirror support portion 11 e provided in the housing 11. In FIG. 3, first to fourth imaging mirrors 6 to 9, abutment surface 25 provided on the mirror surface (reflection surface) side of each imaging mirror and determining the position in the mirror surface direction, and the longitudinal direction of each imaging mirror The bosses 26 and 27 and the projections 28 and 29 for determining the position in the short direction, the long holes 30 to 33 provided in the imaging mirror support 11e and the bosses and projections of the imaging mirror are fitted, 4 shows a leaf spring 34 for fixing the four imaging mirrors 6 to 9 to the imaging mirror support 11e.

  The positions of the first to fourth imaging mirrors 6 to 9 are determined by fitting the bosses 26 and 27 and the elongated holes 30 and 31 in the short direction. Similarly, the position in the longitudinal direction is determined by the fitting of the projections 28 and 29 and the elongated holes 32 and 33, and the position in the mirror surface direction is determined by abutting the abutting surface 25 against the mirror support 11e. Is done. The first to fourth imaging mirrors 6 to 9 are fixed at the determined positions by the pressing force of the leaf spring 34.

[Off-axial optical system]
FIG. 4 is a diagram illustrating the configuration of the off-axial optical system according to the first embodiment of the present invention. In FIG. 4, imaging mirrors 6, 7, 8, and 9 have metal layers 6b, 7b, and 8b on image light reflecting surfaces that are one surface of mirror bases 6a, 7a, 8a, and 9a made of resin such as polycarbonate (PC). , 9b are formed to form off-axial reflecting surfaces 6c, 7c, 8c, 9c. On the other hand, metal layers 6d, 7d, 8d, and 9d are formed on the back side surfaces 6e, 7e, 8e, and 9e of the off-axial reflecting surfaces 6c, 7c, 8c, and 9c, respectively. The metal layer on the image light reflecting surface is also referred to as a first metal layer, and the metal layer on the back side surface is also referred to as a second metal layer.

  The metal layers 6b, 7b, 8b and 9b on the image light reflecting surface side are generally made of aluminum or silver, and are formed on the mirror bases 6a, 7a, 8a and 9a by a method such as vacuum deposition. Is done. The material of the metal layers 6b, 7b, 8b, 9b on the image light reflecting surface side is not limited to the above-described aluminum or silver as long as it has a desired spectral reflectance. Moreover, regarding the formation method of the metal layers 6b, 7b, 8b, 9b, it is only necessary to obtain a desired off-axial reflective surface shape and spectral reflectance as the characteristics of the reflective surface, and the method is not limited to the above-described vacuum deposition. Absent.

  On the other hand, the metal layers 6d, 7d, 8d, and 9d provided on the back side surfaces 6e, 7e, 8e, and 9e of the off-axial reflecting surfaces 6c, 7c, 8c, and 9c have a bimetallic action due to thermal expansion caused by the metal on the image light reflecting surface side. It is desirable that the bimetal action of the layers 6b, 7b, 8b, 9b is equivalent. That is, it is desirable that the thermal expansion coefficients of the image light reflecting surface and the back side surface are substantially the same. In the present embodiment, the same material as the metal layers 6b, 7b, 8b, and 9b on the image light reflecting surface side is used for the metal layers 6d, 7d, 8d, and 9d on the back side surface. Further, in the method of forming the metal layers 6d, 7d, 8d, and 9d on the back surface side, it is desirable that the bimetal action due to thermal expansion is equivalent to the bimetal action of the metal layers 6b, 7b, 8b, and 9b on the image light reflecting surface side. . In this embodiment, by using the same method as the formation method of the metal layers 6b, 7b, 8b, and 9b on the image light reflecting surface side, the bonding force between the metal layer and the mirror bases 6a, 7a, 8a, and 9a is made substantially the same. ing.

  In the present embodiment, the metal layers 6b, 7b, 8b, 9b on the image light reflecting surface side and the metal layers 6d, 7d, 8d, 9d on the back surface side are made the same. However, even if a different material or a different formation method is used, the off-axial reflective surfaces 6c, 7c, 8c, which cancel each other out of the bimetal effect as compared with the conventional example in which the metal layers 6d, 7d, 8d, 9d on the back side are not provided. If the deformation of 9c is reduced, the imaging performance is improved. Therefore, the metal layers 6b, 7b, 8b, and 9b on the image light reflecting surface side and the metal layers 6d, 7d, 8d, and 9d on the back surface side do not have to be exactly the same, and the desired effect is achieved. What is necessary is just to select suitably according to.

[Action by temperature rise]
In the present invention, the operation when the temperature of the imaging mirror increases will be described below. When the mirror bases 6a, 7a, 8a, 9a are extended by thermal expansion, the metal layers 6b of the mirror bases 6a, 7a, 8a, 9a are caused by the difference in thermal expansion coefficient from the metal layers 6b, 7b, 8b, 9b. On the 7b, 8b, and 9b sides, an effect of inhibiting the extension of the mirror substrate occurs. However, at this time, the metal layers 6d, 7d, 8d, and 9d also have the same action on the back side of the off-axial reflecting surfaces 6c, 7c, 8c, and 9c, so that the imaging mirrors 6, 7, 8, and 9 themselves Bimetal deformation can be reduced. As a result, the deformation of the off-axial reflecting surfaces 6c, 7c, 8c, and 9c becomes smaller than that of the conventional one, and the deterioration of the imaging performance due to the temperature rise can be suppressed to a small level. When the thermal expansion coefficient of the material used for the metal layer on the reflective side of the image light and the metal layer on the back side is smaller than the thermal expansion coefficient of the material of the mirror base, An effect of inhibiting the metal layer on the reflection side and the metal layer on the back surface side occurs. In addition, when the thermal expansion coefficient of the material used for the metal layer is larger than the thermal expansion coefficient of the material in the mirror base, an action of promoting the extension of the mirror base occurs due to the thermal expansion of the metal layer. However, in both cases, the bimetal deformation can be reduced. Therefore, the deformation of the off-axial reflecting surfaces 6c, 7c, 8c, and 9c becomes smaller than the conventional one, and the deterioration of the imaging performance due to the temperature rise can be suppressed small.

  In this embodiment, the metal layer 6b provided on the off-axial reflecting surface 6c side of the first imaging mirror 6 and the metal layer 6d provided on the back side thereof have substantially the same thermal expansion coefficient and thickness. It is configured. The relationship between the metal layer 7b and the metal layer 7d in the second imaging mirror 7, the metal layer 8b and the metal layer 8d in the third imaging mirror 8, and the relationship between the metal layer 9b and the metal layer 9d in the fourth imaging mirror is also the first result. This is the same as the relationship between the metal layer 6b and the metal layer 6d in the image mirror. Thereby, the effect | action which suppresses the said bimetal acts more effectively, and can suppress the fall of the imaging performance by a temperature rise smaller.

  In this configuration, during the image reading operation, the element 40 on the substrate 18 of the electric circuit on which the photoelectric conversion element 10 is mounted generates heat, so that the imaging mirror 6 disposed at the position facing the element 40 is turned off. Radiant heat from the element 40 acts on the back side of the axial reflecting surface 6c. Further, radiant heat from the illumination light source 2 acts on the imaging mirror 7 facing the illumination light source 2 on the back side of the off-axial reflection surface 7c. When the side close to the heat source of the imaging mirrors 6 and 7 is warmed by these radiant heats, the thermal expansion on the side close to the heat source of the imaging mirror in the transition period of temperature rise causes the side far from the heat source (off-axial reflecting surface 6c, 7c) is increased with respect to thermal expansion.

  In the present invention, the metal layer 6d is provided on the surface (back side surface 6e) facing the element 40 of the imaging mirror 6 facing the element 40 on the substrate 18 serving as a heat source. Thereby, since the radiant heat (infrared rays) from the element 40 is reflected by the metal layer 6d, the thermal expansion of the surface (back side surface 6e) of the mirror base 6a facing the element 40 is the conventional example without the metal layer. It becomes small compared. For this reason, it is possible to suppress a decrease in imaging performance caused by deformation due to partial thermal expansion of the imaging mirror 6. In the present invention, the metal layer 7d is provided on the surface (back side surface 7e) facing the illumination light source 2 of the imaging mirror 7 facing the illumination light source 2 serving as a heat source. Thereby, similarly to the imaging mirror 6 described above, it is possible to suppress a decrease in imaging performance caused by deformation due to partial thermal expansion of the imaging mirror 7.

  Moreover, in this embodiment, although it has four image formation mirrors, the effect | action degree of the radiant heat from a heat source differs with respect to each. Therefore, it is not necessary to use the same material constituting the metal layer in all four imaging mirrors. That is, it is only necessary that the relationship between the reflection surface and the back side surface thereof corresponds, and it is not necessary to have the same characteristics between the coupling mirrors.

<Second embodiment>
FIG. 5 is a diagram illustrating the configuration of an off-axial optical system according to the second embodiment of the present invention. In FIG. 5, a metal layer 6 b provided on the off-axial reflecting surface 6 c side of the first imaging mirror 6 and a metal layer 6 d provided on the back side thereof are heat transfer layers provided on the side surfaces of the first imaging mirror 6. It is connected by 6f. Thereby, when the temperature of the metal layer 6d partially rises, heat flows to the metal layer 6b side through the heat transfer layer 6f due to the heat conduction action, and the speed at which the temperature difference between the front and back metal layers 6b and 6d is eliminated increases. .

  The heat transfer layer 6f is desirably made of a material having a higher thermal conductivity than the mirror base 6a. For example, when the material of the mirror base 6a is a resin, the heat transfer layer can be made of a metal such as aluminum having a higher thermal conductivity and formed on the mirror base 6a by a forming method such as vacuum deposition. In the present embodiment, the metal layer 6b, the metal layer 6d, and the heat transfer layer 6f are all made of aluminum, and are formed on the mirror base 6a by vacuum deposition. In the process of vacuum deposition, the metal layer 6b, the metal layer 6d, and the heat transfer layer 6f can be integrally and simultaneously formed by performing deposition while rotating the mirror base 6a in a vacuum chamber. .

  With this configuration, the loss of heat conduction at the interface can be reduced compared to the case where there is an interface between the metal layer 6d and the heat transfer layer 6f and an interface between the heat transfer layer 6f and the metal layer 6b. The material or the formation method of the heat transfer layer is such that the total thermal conductivity at the interface between the metal layer 6d and the heat transfer layer 6f, the heat transfer layer 6f itself, and the interface between the heat transfer layer 6f and the metal layer 6b is It may be smaller than the overall thermal conductivity at the interface between the metal layer 6d and the mirror base 6a, the mirror base 6a itself, and the interface between the mirror base 6a and the metal layer 6b. For this reason, you may select suitably a material and a formation method not only in the above-mentioned aluminum and vacuum evaporation.

  Further, the heat transfer layer may be formed on the entire surface of the mirror base except for the reflection surface and the back side surface thereof, or the heat transfer layer may be formed only on two opposing surfaces of the mirror base. . The relationship between the metal layer 7b and the metal layer 7d in the second imaging mirror 7, the metal layer 8b and the metal layer 8d in the third imaging mirror 8, and the relationship between the metal layer 9b and the metal layer 9d in the fourth imaging mirror 8 This is the same as the relationship between 6b and the metal layer 6d. That is, the corresponding metal layers are connected by the heat transfer layer 7f, the heat transfer layer 8f, and the heat transfer layer 9f, respectively.

  As described above, a decrease in imaging performance caused by deformation due to partial thermal expansion of the imaging mirror can be eliminated in a shorter time.

Claims (6)

An image reading apparatus including an image forming mirror on which a curved reflecting surface is formed, the image forming unit including an image reading unit configured to form an image on the reading unit;
The imaging mirror has a first metal layer on one surface of a mirror base, the reflection surface is formed on the surface of the first metal layer, and a second metal layer is formed on the back surface of the reflection surface. An image reading apparatus.   The image reading apparatus according to claim 1, wherein the first metal layer and the second metal layer are formed of a material having substantially the same thermal expansion coefficient.   The image reading apparatus according to claim 1, wherein the imaging mirror further includes a heat transfer layer that connects the first metal layer and the second metal layer. An image reading apparatus comprising: an illuminating unit; a reading unit that reads an image; and an imaging unit that forms an image on the reading unit, wherein the imaging unit includes a plurality of imaging mirrors each having a curved reflecting surface. Because
In each of the plurality of imaging mirrors, the mirror base has a first metal layer on one surface, and the reflective surface is formed on the surface of the first metal layer.
An image reading apparatus comprising: a second metal layer on a rear side of the reflecting surface on an imaging mirror arranged at a position where radiation heat from the illumination unit acts among the plurality of imaging mirrors. An image reading apparatus comprising: an electric circuit; reading means for reading an image; and image forming means for forming an image on the reading means, wherein the image forming means includes a plurality of image forming mirrors each having a curved reflecting surface. Because
In each of the plurality of imaging mirrors, the mirror base has a first metal layer on one surface, and the reflective surface is formed on the surface of the first metal layer.
The image reading mirror having a second metal layer on the back side of the reflecting surface on the image forming mirror disposed at a position where radiation heat from the elements of the electric circuit acts among the plurality of image forming mirrors. apparatus. An imaging mirror in which an off-axial reflecting surface having a curvature different from an incident direction and an exit direction of a reference axis ray is formed,
It has a first metal layer on one surface of a mirror base, an off-axial reflection surface is formed on the surface of the first metal layer, and a second metal layer is formed on the back side surface of the off-axis reflection surface. The imaging mirror.

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