JP2018182758A - Image reading apparatus and method of assembling the same - Google Patents

Abstract

An assembly method of an image reading apparatus capable of reading a good image without blur even when the longitudinal direction of the frame is warped. When a lens array 3 and a light receiving element array 5 constituting an equal-magnification optical system are fixed along the longitudinal direction of a frame 2, a measuring instrument 8 and a support mechanism 7 are used, and the support mechanism 7 is attached to the frame 2. Based on the amount of warpage along the optical axis direction of the frame 2 measured by the measuring instrument 8, the frame 2 is symmetric with respect to the frame 2. The distance from the object plane M to the upper end surface of the lens array 3 and the distance from the imaging plane F of the light receiving element array 5 to the lower end surface of the lens array 3 The curvature of the lens array 3 is adjusted so that L1 and L2 are equal to each other (where L2 ≠ L1). [Selection] Figure 5

Description

  The present invention relates to an image reading apparatus such as a contact type image sensor that can be used for a facsimile machine, a copying machine, a scanner or the like, and an assembling method thereof.

  2. Description of the Related Art In recent years, a small-sized image reader has been used for a back side reading sensor of a copying machine, a facsimile machine, a document reading sensor of a scanner, or a bill recognition sensor such as a financial terminal.

  This type of image reading apparatus includes a cover member that regulates the reading position of the document, a lens array for obtaining an erect equal-magnification image of the image of the document, and a light receiving element array for photoelectrically converting the erected equal-magnification image It comprises a substrate on which the light receiving element array is mounted, a cover member as described above, a lens array, a light receiving element array, a frame for positioning the substrate, and the like.

  The above cover member is made of, for example, transparent glass or transparent resin, and the lens array is, for example, a GRIN lens in which a plurality of GRIN lenses having a refractive index distribution defined by a predetermined function in the radial direction are two-dimensionally arrayed. An array or the like is used. The GRIN lens array generally has a structure in which cylindrical lenses (hereinafter simply referred to as lenses) are two-dimensionally arrayed and adhesively fixed in a state in which both sides along the axial direction are sandwiched by side plates. The light receiving element array is configured by two-dimensionally arranging a plurality of light receiving elements on a substrate in order to photoelectrically convert an erect equal-magnification image.

  The respective lenses constituting the lens array have a very shallow depth of focus and can read an original with good contrast without blurring when constituting an equal-magnification optical system for obtaining an erect equal-magnification image. The distance from the reading position (hereinafter referred to as the object plane) to the upper end face of the light incident side of each lens and the distance from the imaging plane of the light receiving element array to the lower end face of the light emission side of each lens are not the same. If the distance between the two is even slightly different, the MTF (Modulation Transfer Function) performance drops significantly. Conversely, for each lens, it is known that if the above two distances are the same, there is little decrease in MTF performance even if the conjugate distance from the object plane to the imaging plane is slightly different (eg, See Patent Document 1 below).

  Here, a structure of an image reading apparatus has been proposed in which a cover member having a plate thickness capable of securing MTF performance is selected in advance, and the lens array is brought into contact with the selected cover member and fixed. According to this structure, the optical path length adjustment operation for securing the MTF performance becomes unnecessary (see, for example, Patent Documents 2 and 3 below).

Unexamined-Japanese-Patent No. 2000-32214 Japanese Patent Application Laid-Open No. 10-190909 International Publication WO2009 / 104602

  In the structure of such an image reading apparatus, the frame for positioning the cover member, the lens array, and the substrate is often formed of a resin molded product in terms of cost. The frame which is such a resin molded product is apt to be slightly distorted due to the influence of heat contraction after heat molding and the like, and in particular, it is easily warped along its longitudinal direction.

  On the other hand, the substrate on which the above-mentioned cover member, lens array and light receiving element array are mounted is assembled with reference to the frame. In particular, in the conventional image reading apparatus described in Patent Document 2, the upper end surface of the light incident side of the lens array is fixed in contact with the lower surface of the cover member. Further, in the conventional image reading apparatus described in Patent Document 3, the lower end surface of the light emitting side of the lens array is fixed in contact with the lower surface of the storage chamber formed in the frame.

  For this reason, when warpage during molding as described above occurs in the frame, along with this, warpage also occurs in the cover member, the lens array, the substrate, and the light receiving element array assembled with reference to the frame. As a result, when viewed with respect to the individual lenses, the object plane in which the contrasts of the respective lenses are aligned is curved in accordance with the warp of the frame. On the other hand, since a document such as a sheet of paper normally passes over the cover member in a flat state, it becomes difficult to make the object surface flat over the entire area along the longitudinal direction of the lens array, and the document is read The image is blurred. In particular, blurring easily occurs along the longitudinal direction of the lens array or the light receiving element array.

  In order to prevent such a defect caused by the warp of the frame, for example, it is conceivable to eliminate the warp by polishing the frame, etc. However, in this case, a precise polishing operation is required, which is unnecessary. It is not preferable because man-hours and labor are required, and cost increases are caused.

  The present invention has been made to solve the above-mentioned problems, and it is possible to cover the entire area along the longitudinal direction of the lens array without requiring extra effort or labor even if the frame is warped. An object of the present invention is to provide an image reading apparatus capable of securing performance and a method of assembling the same.

  In the image reading apparatus according to the present invention, a lens array and a light receiving element array constituting an equal-magnification optical system are fixed along the longitudinal direction of the frame, and a measuring device for measuring the amount of warpage of the frame A support mechanism for supporting and curving the lens array, the support mechanism being disposed at three locations at least at a central position along the longitudinal direction of the frame and at respective positions symmetrical from the central position, the support Based on the measurement result obtained by measuring the amount of warp along the optical axis direction of the frame at the central position in the longitudinal direction of the frame by the mechanism, the document is read at each position of the left-right symmetry of the frame The distance from the object plane, which is the position, to the upper end face of the lens array, and the distance from the imaging plane of the light receiving element array to the lower end face of the lens array The distance from the object plane to the upper end face of the lens array at the center position of the frame is equal to L1 and the distance from the imaging plane of the light receiving element array to the lower end face of the lens array is equal to each other The curvature of the lens array is adjusted to be equal to L2 (where L2LL1).

  In the method of assembling an image reading apparatus according to the present invention, a measuring instrument for measuring the amount of warping of the frame when the lens array and the light receiving element array constituting the equal-magnification optical system are fixed along the longitudinal direction of the frame. And a support mechanism for supporting and curving the lens array, and the support mechanism is arranged at three positions at least at a central position and in symmetrical positions from the central position along the longitudinal direction of the frame, The measuring instrument measures the amount of warping along the optical axis direction of the frame at the central position in the longitudinal direction of the frame, and based on the measurement result, the support mechanism detects each position of the frame in the lateral symmetry. And the distance from the object plane which is the reading position of the original to the upper end face of the lens array, and the image plane of the light receiving element The distance to the surface is equal to L1, and the distance from the object surface to the upper end surface of the lens array at the center position of the frame and the image forming surface of the light receiving element array are below the lens array. It is characterized in that the curvature of the lens array is adjusted so that the distances to the end face become equal to each other as L2 (where L2 ≠ L1).

  According to the image reading apparatus of the present invention, it is possible to flatten the object surface necessary to obtain a good contrast over the entire area along the sub scanning direction without being affected by the warp of the frame. As a result, the object plane can be reliably contained within the flat MTF performance allowable range, so that no blurring occurs in the image read from the original.

  Further, according to the assembling method of the image reading apparatus of the present invention, by applying the measuring instrument and the supporting mechanism, the amount of warpage according to the amount of warpage of the light receiving element array accompanying the warpage of the frame is reliably formed in the lens array. As a result, it is possible to manufacture an image reader of good quality in which no blurring occurs in the image obtained by reading the original.

FIG. 1 is an exploded perspective view showing an image reading apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view along the main scanning direction showing the structure of the image reading apparatus of FIG. 1; It is a perspective view which shows the assembled state of the lens array of the image reading apparatus of FIG. FIG. 6 is a schematic cross-sectional view taken along a sub-scanning direction orthogonal to the main scanning direction for describing the arrangement relationship between the lens array, the light receiving element array, and the frame of the image reading device of FIG. FIG. 8 is a schematic cross-sectional view taken along the sub-scanning direction orthogonal to the main scanning direction for describing the mutual relationship between the object plane, the imaging plane, and the MTF performance allowable range in the equal magnification optical system in the image reading device of FIG. FIG. 10 is a cross-sectional view along the main scanning direction showing the structure of a conventional image reading apparatus. FIG. 10 is a cross-sectional view in the main scanning direction showing the structure of another conventional image reading apparatus. FIG. 10 is a schematic cross-sectional view taken along a sub-scanning direction orthogonal to the main scanning direction for describing the mutual relationship between an object plane, an imaging surface, and an allowable range of MTF performance in the conventional image reading device shown in FIGS. .

  Before describing the first embodiment of the present invention, the contents of the prior art and problems in that case will be described below in order to understand the features of the present invention.

  FIG. 6 is a cross-sectional view along the main scanning direction (Y direction in the figure) in the conventional image reading apparatus described in the above-mentioned Patent Document 2. As shown in FIG. FIG. 7 is a cross-sectional view along the main scanning direction (Y direction in the figure) in the conventional image reading apparatus described in the above-mentioned Patent Document 3. As shown in FIG.

  6 and 7, reference numeral 3 is a lens array for obtaining an erect equal-magnification image of a document, 4 is a cover member for restricting the reading position of the document, and 5 is a light receiving for photoelectrically converting the erect equal-magnification image. The element array 6 is a substrate on which the light receiving element array 5 is mounted, and 2 is a frame for positioning and fixing the lens array 3, the cover member 4 and the substrate 6 described above.

  Then, in the configuration shown in FIG. 6, the lens array 3 is a long hole 2 b in which the lower end face 3 b on the light emission side is formed in the frame 2 in a state of being along the vertical reference surface 2 a formed in the frame 2. And the upper end surface 3a of the light incident side of the lens array 3 is in contact with the lower surface of the cover member 4 and fixed.

  Further, in the configuration shown in FIG. 7, the lens array 3 is a storage chamber 2 c in which the lower end surface 3 b on the light emission side is formed in the frame 2 along the vertical reference surface 2 a formed in the frame 2. The light receiving element array 5 is opposed to the lower surface of the storage chamber 2c through a through hole 2d formed in the bottom of the storage chamber 2c.

  In the image reading apparatus having any of the configurations shown in FIGS. 6 and 7, since the lens array 3, the cover member 4, the light receiving element array 5, and the substrate 6 are integrally fixed to the frame 2, FIG. As shown, in the longitudinal direction of the frame 2, that is, in the sub scanning direction (X direction) orthogonal to the main scanning direction (Y direction), the lens array 3 and the cover according to the degree of warping when the frame 2 is formed. The member 4, the light receiving element array 5, and the substrate 6 have the same warpage. That is, in the sub scanning direction (X direction), the lens array 3 or the light receiving element array 5 is curved with the same curvature together with the frame 2.

  Therefore, at any point near the center and in the vicinity of the end of the frame 2 in the longitudinal direction (X-axis direction), it is necessary to obtain good contrast on the light incident side of the lens array 3 from the object plane M. The distance to the end face 3a and the distance from the imaging surface F of the light receiving element array 5 to the lower end face 3b on the light emission side of the lens array 3 are all equal to L3. That is, when the warp at the time of molding is generated in the frame 2, the object surface M necessary for obtaining a good contrast is in a curved state according to the degree of the warp of the frame 2. On the other hand, a document such as a sheet of paper usually passes over the cover member 4 in a flat state.

  Therefore, it becomes difficult to bring the object surface M necessary for obtaining a good contrast within the flat MTF performance tolerance R over the entire region along the longitudinal direction of the lens array 3. That is, in the case of FIG. 8, the object plane M deviates by ΔR from the flat MTF performance allowable range R near the center in the X-axis direction. As a result, blurring occurs in the image obtained by reading the original. In particular, blurring easily occurs in the sub scanning direction (X-axis direction).

  Next, a first embodiment of the reader of the present invention will be described.

Embodiment 1
FIG. 1 is an exploded perspective view showing an image reading apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a sectional view taken along the main scanning direction (Y-axis direction) showing the structure of the image reading apparatus. The same reference numerals as in the prior art shown in FIG.

  The image reading apparatus 1 according to the first embodiment includes a cover member 4 for regulating the reading position of a document, a lens array 3 for obtaining an erect equal-magnification image of an image of the document, and photoelectrically converting the erected equal-magnification image. A light receiving element array 5, a substrate 6 on which the light receiving element array 5 is mounted, and a frame 2 for positioning and fixing the cover member 4, the lens array 3, the light receiving element array 5 and the substrate 6 described above; The lens array 3, the cover member 4, the light receiving element array 5, and the substrate 6 are integrally fixed to the frame 2 using an adhesive or the like.

  In the first embodiment, the lens array 3 is formed along the vertical reference surface 2 a formed in the frame 2, and the lower end face 3 b on the light emission side penetrates the long hole 2 b formed in the frame 2. The light receiving element array 5 is opposed to the light receiving element array 5 while maintaining a fixed gap S2. On the other hand, the upper end surface 3a of the light incident side of the lens array 3 is not in contact with the lower surface 4b of the cover member 4 and is fixed in a state in which a fixed gap S1 is secured.

  In that case, the gaps S1 and S2 secured above and below the lens array 3 are set in advance so as to be sufficiently larger than the amount of warpage of the frame 2, and the optical axis direction (Z axis direction) of the lens array 3 The structure is adjustable.

  FIG. 3 is a perspective view showing an assembled state of the lens array of the image reading apparatus according to the first embodiment, and FIG. 4 is a view for explaining an arrangement relationship with the lens array, light receiving element array and frame of the image reading apparatus. FIG. 6 is a cross-sectional view taken along a sub-scanning direction (X-axis direction) orthogonal to the main scanning direction (Y-axis direction).

  When assembling the lens array 3, the warpage amount of the lower surface 2e of the frame 2 along the sub-scanning direction (X-axis direction) which is the longitudinal direction of the frame 2 is measured in advance using the respective measuring instruments 8a, 8b, 8c The result is taken into the controller 9. And based on the measurement result of each measuring instrument 8a, 8b, 8c, by the control of the controller 9, the support mechanisms 7a, 7b, 7c provided with the actuators are driven to bend the lens array 3, and the lens array in that state Fix 3 to the frame 2 with an adhesive or the like.

  In this case, on the lower surface 2e side of the frame 2 along the sub-scanning direction (X-axis direction), each measuring instrument 8a, 8b, 8c is separated from the position P2 at its center and a predetermined distance X0 from the position P2 to the left and right. Are arranged at symmetrical positions P1 and P3. Here, as each of the measuring instruments 8a, 8b, 8c, for example, a light load contact type linear gauge or a noncontact type laser displacement meter can be applied. In particular, the use of a laser displacement meter has an advantage that the warp of the frame 2 can be measured more accurately without contact.

  In addition, in each support mechanism 7a to 7c described above, the support point is included in a vertical plane along the optical axis direction (Z axis direction) of the lens array 3 passing the measurement points of the respective measuring instruments 8a to 8c. Is located in That is, in the upper end face 3a in the longitudinal direction (X-axis direction) of the lens array 3, the vertical plane of each of the central position P5 and symmetrical positions P4 and P6 separated from the central position P5 by a fixed distance X0 respectively to the left and right. Each support mechanism 7a-7c is arrange | positioned, respectively so that it may pass.

  Here, as each support mechanism 7a, 7b and 7c, for example, a mechanism combining an actuator such as a piezo element and a chuck for holding the lens array 3 or an adsorption head for adsorbing the side surface of the lens array 3 is used. be able to. In particular, as shown in FIG. 3, the head portion where each support mechanism 7a, 7b, 7c abuts on the lens array 3 contacts both the upper end surface 3a of the lens array 3 and its side surface, as described later. As described above, when the lens array 3 is bent, it is advantageous because the lens array 3 can be reliably deformed without being damaged.

  The amount of warping D of the imaging surface F along the sub-scanning direction (X-axis direction), which is the longitudinal direction of the frame 2, can be measured as follows based on the measurement results of the measuring devices 8a, 8b, 8c.

  Since the length in the optical axis direction (Z-axis direction) of the light receiving element array 5 is sufficiently smaller than the dimension in the longitudinal direction (X-axis direction) of the frame 2, it follows the longitudinal direction (X-axis direction) of the frame 2 The amount of warpage of the light receiving element array 5 and the amount of warpage of the imaging surface F can be regarded as equivalent to the amount of warpage of the lower surface 2 e of the frame 2. From this, first, the warp amount D of the lower surface 2 e of the frame 2 is measured using the measuring instruments 8 a to 8 c.

  Here, for each of the measuring instruments 8a to 8c arranged along the sub scanning direction (X-axis direction), the coordinates of the measuring points of the measuring instrument 8a are P1, the coordinates of the measuring points of the measuring instrument 8b are P2, and the measuring instruments Assuming that the coordinate of the measurement point 8c is P3, the amount of warpage D of the lower surface 2e of the frame 2 is given by the following equation as the difference of the coordinate in the optical axis direction (Z-axis direction).

  D = (P1 + P3) / 2-P2 (1)

  As described above, when the amount of warpage D of the lower surface 2e of the frame 2 is determined, the controller 9 drives the support mechanisms 7a to 7c disposed corresponding to the measurement points P1, P2, and P3 described above to The amount of warpage at the central position in the longitudinal direction (X-axis direction) of the upper end face 3a of the array 3 is adjusted so as to be curved to about one half of the amount of warpage D obtained by the above equation (1).

  Here, the coordinates of the respective positions where the support mechanisms 7a to 7c contact the upper end face 3a of the lens array 3 are P4, P5 and P6, respectively, and the distances connecting the coordinate positions P1 and P4 and P6 and P3 are both If it sets beforehand as L0, each coordinate P4, P5, P6 will be obtained by the following formula.

P4 = P1 + L0 (2)
P6 = P3 + L0 (3)
P5 ≒ (P4 + P6) / 2-D / 2 (4)

  Then, under the control of the controller 9, the support mechanisms 7a to 7c are moved along the sub-scanning direction (X-axis direction) so that the upper end surface 3a of the lens array 3 passes the position of the coordinates P4, P5, and P6. It is driven to bend the lens array 3.

In this way, when assembling the image reading apparatus 1, the lens on the vertical reference surface 2 a of the frame 2 is maintained while holding the state in which the lens array 3 is bent by the support mechanisms 7 a to 7 c in the above procedure. The array 3 is abutted and fixed with an adhesive or the like. After the lens array 3 is fixed to the frame 2, the support mechanisms 7a to 7 and the measuring instruments 8a, 8b and 8c are removed.
Next, the substrate 6 on which the light receiving element array 5 is mounted is fixed to the lower surface 2 e of the frame 2. Subsequently, the gap S1 of the lower surface 4b of the cover member 4 with respect to the upper end surface 3a of the light incident side of the lens array 3 is adjusted, and then the cover member 4 is fixed to the upper surface 2f of the frame 2. The substrate 6 may be fixed after the cover member 4 is fixed to the frame 2.

  FIG. 5 is a schematic cross-sectional view along the sub-scanning direction (X-axis direction) for describing the mutual relationship between the object plane M, the imaging plane F, and the MTF performance allowable range R in the equal-magnification optical system.

  As described with reference to FIGS. 3 and 4, when fixing the lens array 3 to the frame 2, the amount of warpage of the lower surface 2 e of the frame 2 along the sub-scanning direction (X-axis direction) which is the longitudinal direction of the frame 2 D is measured in advance using the measuring devices 8a, 8b, 8c, and the controller 9 drives the support mechanisms 7a, 7b, 7c based on the measurement results of the measuring devices 8a, 8b, 8 to obtain a lens array The amount of warpage at the central position in the longitudinal direction (X-axis direction) of the upper end face 3a of 3 is adjusted to be curved to approximately one half of the amount of warpage D obtained by the above equation (1). Then, as shown in FIG. 5, in the vicinity of both ends in the longitudinal direction (X-axis direction) of the frame 2, the distance from the object plane M to the upper end surface 3a of the lens array 3 necessary for obtaining good contrast The distance from the image plane F of the element array 5 to the lower end face 3b of the lens array 3 is equal to L1. In the vicinity of the center of the frame 2 in the longitudinal direction (X-axis direction), the distance from the object plane M to the upper end face 3 a of the lens array 3 necessary for obtaining good contrast, and the imaging plane of the light receiving element array 5 The distance from F to the lower end face 3b of the lens array 3 is equal to L2 in all cases.

  That is, when warpage at the time of molding occurs in the frame, the conjugate distance of each lens constituting the lens array 3 is different in the vicinity of both ends and in the vicinity of the center of the frame 2 in the longitudinal direction (X axis direction) ( L1 ≠ L2) The object plane M necessary to obtain good contrast is all flat along the longitudinal direction (X-axis direction) of the frame 2 without being affected by the warp of the frame 2. On the other hand, a document such as a sheet usually passes above the cover member 4 in a flat state.

  Therefore, even if the frame 2 is warped, the object plane M necessary for obtaining a good contrast can be made flat over the entire area along the sub scanning direction (X-axis direction) without being affected by this. Therefore, the object plane M can be reliably contained within the flat MTF performance allowable range R, and no blurring occurs in the image obtained by reading the document.

  The inclination with respect to the optical axis of each lens of the lens array 3 forming the equal-magnification optical system is 1 ° or less. For example, the length of the sub-scanning direction (X-axis direction) of the frame 2 is mounted on a copying machine of A4 size In the case of such a size, the amount of warpage of the lens array 3 is 2.5 mm or less. Even if the frame 2 is a resin material, it is not difficult to set the amount of warpage of the lens array 3 to 2.5 mm or less. Further, since the lens array 3 is a resin material, the residual stress in the case of fixing with the amount of warping of 2.5 mm is sufficiently smaller than the shear stress of bonding and fixing, so there is no problem.

  The present invention is not limited to only the configuration of the first embodiment, and various modifications may be made to the configuration of the first embodiment without departing from the scope of the present invention. Can be partially omitted.

Reference Signs List 1 image reading apparatus, 2 frame, 3 lens array, 3a upper end surface, 3b lower end surface, 4 cover member, 5 light receiving element array, 6 substrate, 7a to 7c support mechanism,
8a-8c Instruments, 9 controllers, R MTF performance tolerance, M object plane,
F imaging plane.

Claims (4)

A method of assembling an image reading apparatus in which a lens array constituting an equal-magnification optical system and a light receiving element array are fixed along the longitudinal direction of a frame,
A measuring instrument for measuring the amount of warpage of the frame and a support mechanism for supporting and curving the lens array are applied, and the support mechanism is laterally symmetrical from at least a central position along the longitudinal direction of the frame and the central position The amount of warping along the optical axis direction of the frame at the central position in the longitudinal direction of the frame is measured by the measuring device, and the support mechanism is used based on the measurement result. A distance from an object plane which is a reading position of an original at each of the left-right symmetrical positions of the frame to an upper end surface of the lens array, and a distance from an imaging surface of the light receiving element array to a lower end surface of the lens array; Are equal to each other, and the distance from the object plane to the upper end surface of the lens array at the center position of the frame and the light receiving element array Method of assembling an image reading apparatus for adjusting the curvature of the lens array as the distance from the imaging surface to the lower end surface of the lens array is equal to each other L2 (although, L2 ≠ L1) becomes. The support mechanism is driven to curve the lens array so that the upper end surface along the longitudinal direction of the lens array passes through the position of coordinates P4, P5 and P6 obtained by the following equations (2) to (4) A method of assembling an image reading apparatus according to claim 1.
D = (P1 + P3) / 2-P2 (1)
P4 = P1 + L0 (2)
P6 = P3 + L0 (3)
P5 ≒ (P4 + P6) / 2-D / 2 (4)
here,
P2: Coordinates of measurement points in the optical axis direction by the measuring device at the center position in the longitudinal direction of the frame P1, P3: Coordinates of measurement points in the optical axis direction by the measuring device at each position symmetrical with the center position in the longitudinal direction of the frame D: Warpage along the optical axis near the longitudinal center of the frame L0: Pre-set distance The method of assembling an image reading apparatus according to claim 1, wherein the frame is formed of a resin molded product. In an image reading apparatus in which a lens array and a light receiving element array constituting an equal magnification optical system are fixed along the longitudinal direction of a frame,
A measuring device for measuring the amount of warping of the frame; and a supporting mechanism for supporting and curving the lens array, the supporting mechanism being symmetrical at least at a central position along the longitudinal direction of the frame and from the central position The frame is disposed at three locations at each position, and the support mechanism measures the amount of warpage along the optical axis direction of the frame at the central position in the longitudinal direction of the frame by the measuring device. The distance from the object plane, which is the reading position of the document, to the upper end surface of the lens array at each position of the left-right symmetry and the distance from the imaging surface of the light receiving element array to the lower end surface of the lens array are equal to each other L1, and the distance from the object plane to the upper end face of the lens array at the central position of the frame, and the connection of the light receiving element array And the distance to the lower end surface of the lens array are equal to each other from the surface L2 (although, L2 ≠ L1) become as the lens array curvature adjusted image reading apparatus.

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