WO2015072284A1

WO2015072284A1 - Lens array optical system, and image forming apparatus and image reading apparatus including the lens array optical system

Info

Publication number: WO2015072284A1
Application number: PCT/JP2014/077761
Authority: WO
Inventors: Yu Miyajima; Takeyoshi Saiga; Masatsugu Koyama
Original assignee: Canon Kabushiki Kaisha
Priority date: 2013-11-14
Filing date: 2014-10-10
Publication date: 2015-05-21
Also published as: JP6677439B2; JP2015118357A

Abstract

This invention provides an imaging optical system that can prevent blocking of a desired imaging light flux and prevent generation of unwanted ghost light. The imaging optical system includes: a first lens array that includes a plurality of lenses arrayed in a first direction and that forms an intermediate image of an object in a first section parallel to the first direction; a second lens array that includes a plurality of lenses arrayed in the first direction and that re-images the intermediate image of the object in the first section; and a light blocking member disposed between optical axes of adjacent lenses of the first and second lens arrays. At least one of the first and second lens arrays has a ghost light suppressing portion between adjacent lens surfaces. A width of the ghost light suppressing portion in the first direction is greater than a width in the first direction of the light blocking member.

Description

DESCRIPTION

Title of Invention

LENS ARRAY OPTICAL SYSTEM, AND IMAGE FORMING APPARATUS AND IMAGE READING APPARATUS INCLUDING THE LENS ARRAY OPTICAL SYSTEM

Technical Field

[0001] The present invention relates to a lens array optical system, and is suitable, for example, for a lens array optical system that is used in an image forming

apparatus or an image reading apparatus .

Background Art

[0002] Recently, image forming apparatuses and image reading apparatuses have been developed that use a lens array optical system that includes a small-diameter lens array. For example, image forming apparatuses and image reading apparatuses which include a built-in unit (optical apparatus) in which a lens array optical system is held together with an array-like light source such as an LED or a line sensor are known. The use of the lens array optical system can reduce the size and cost of such apparatuses.

[0003] However, in the conventional lens array optical system, there has been the problem that unwanted ghost light arises that is different to a light flux (imaging light flux) for performing desired imaging on an image plane (refers to a sensor surface in the case of an image reading apparatus, and refers to a photosensitive surface in the case of an image forming apparatus) .

[0004] PTL 1 discloses a lens array optical system in which a light blocking member that is formed by a light

absorption portion is disposed so as to be sandwiched between two lens arrays. According to this

configuration, light rays that are transmitted between adjacent lenses among a plurality of lenses included in the lens array optical system are blocked to . thereby prevent the generation of unwanted light (ghost light). Citation List

Patent Literature

[0005] PTL 1: Japanese Patent Application Laid-Open No. 2010- 14824

Summary of Invention

Technical Problem

[0006] According to the lens array optical system disclosed in PTL 1, because the light blocking member is not fitted into the lens array, there is the advantage that assembly is easy. However, if an arrangement error occurs at the time of assembly or there is a difference in the linear expansion coefficients between the lens arrays and the light blocking member, it is conceivable that this may result in the relative position between the lens arrays and the light blocking member deviating from the ideal position in a case where the ambient temperature fluctuates. There is thus the problem that the light blocking member will block an imaging light flux, or that the light blocking member will allow the passage of ghost light.

[0007] herefore, an object of the present invention is to

provide a lens array optical system (imaging optical system) that can suppress blocking of an imaging light flux as well as the occurrence of ghost light.

Solution to Problem

[0008] An imaging optical system as one aspect of the present invention for achieving the above described object includes: a first lens array that includes a plurality of lenses arrayed in a first direction, and that forms an intermediate image of an object in a first section that is parallel to the first direction; a second lens array that includes a plurality of lenses arrayed in the first direction, and that re-images the

intermediate image of the object in the first section; and a light blocking member that is disposed between optical axes of adjacent lenses of the first and second lens arrays; wherein: at least one of the first and second lens arrays has a ghost light suppressing portion between adjacent lens surfaces; and a width in the first direction of the ghost light suppressing portion is greater than a width in the first direction of the light blocking member.

Further objects and other features of the present invention will become apparent from exemplary

embodiments that are described hereunder with reference to the attached drawings.

Advantageous Effects of Invention

[0009] According to the present invention, in an imaging

optical system, it is possible to suppress blocking of an imaging light flux as well as the occurrence of ghost light that are due to arrangement errors at the time of manufacture or relative positional fluctuations between a lens array and a light blocking member that are caused by ambient temperature variations, and to also suppress the occurrence of ghost light that is caused .by a characteristic shape of a ghost light suppressing portion provided between lenses.

[ 0010 ] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. Brief Description of Drawings

[0011] Fig. 1A is a schematic sectional view at a main array section of an optical apparatus according to a first embodiment of the present invention.

Fig. IB is a schematic sectional view at a sub-array section of the optical apparatus according to the first embodiment of the present invention.

Fig. 1C is a schematic sectional view at a section that is perpendicular to an optical axis of the optical apparatus according to the first embodiment of the present invention. Fig. 2 illustrates schematic sectional views at the main array section and the sub-array section of one part of a lens array optical system according to the first embodiment of the present invention.

Fig. 3A is a schematic sectional view at a main array section of an optical apparatus according to the conventional technology.

Fig. 3B is a schematic sectional view at the main array section of the optical apparatus according to the conventional technology.

Fig. 4A is a schematic sectional view at the main array section of the lens array optical system according to the first embodiment of the present invention.

Fig. 4B is a schematic sectional view at the main array section of the lens array optical system according to the first embodiment of the present invention.

Fig. 4C is a schematic sectional view at the main array section of the lens array optical system according to the first embodiment of the present invention.

Fig. 5A is an enlarged sectional view at the main array section of a light scattering portion according to the first embodiment . of the present invention.

Fig. 5B is an enlarged sectional view at the main array section of the light scattering portion according to the first embodiment of the present invention.

Fig. 6 is a schematic sectional view at the main array section of the lens array optical system according to the first embodiment of the present invention.

Fig. 7 is a schematic sectional view at the main array section of the light scattering portion and a light blocking member of the lens array optical system according to the first embodiment of the present invention .

Fig. 8A is a schematic enlarged sectional view at the main array section of the light scattering portion and the light blocking member of the lens array optical system according to the first embodiment of the present invention.

Fig. 8B is a schematic enlarged sectional view at the main array section of the light scattering portion and the light blocking member of the lens array optical system according to the first embodiment of the present invention .

Fig. 8C is a schematic enlarged sectional view at the main array section of the light scattering portion and the light blocking member of the lens array optical system according to the first embodiment of the present invention .

Fig. 9A is a schematic sectional view at a main array section of an optical apparatus according to a second embodiment of the present invention.

Fig. 9B is a schematic sectional view at a sub-array section of the optical apparatus according to the second embodiment of the present invention.

Fig. 9C is a schematic sectional view at a section that is perpendicular to an optical axis of the optical apparatus according to the second embodiment of the present invention.

Fig. 10 illustrates schematic sectional views at the main array section and the sub-array section of one part of a lens array optical system according to the second embodiment of the present invention.

Fig. 11A is a schematic sectional view at the main array section of the lens array optical system

according to the second embodiment of the present invention.

Fig. 11B is a schematic sectional view at the main array section of the lens array optical system

according to the second embodiment of the present invention .

Fig. 12A is a schematic sectional view of an image forming apparatus equipped with a lens array optical system according to an exemplary embodiment of the present invention.

Fig. 12B is a schematic sectional view of an image forming apparatus equipped with a lens array optical system according to an exemplary embodiment of the present invention.

Fig. 13 is a schematic sectional view of an image reading apparatus, equipped with a lens array optical system according to an exemplary embodiment of the present invention.

Description of Embodiments

[ 0012 ] Preferred embodiments of the present invention will now be described in detail in accordance with the

accompanying drawings.

[0013] A lens array optical system (imaging optical system)

according to the present invention is described

hereunder based on the accompanying drawings. Note that, in the drawings described hereunder, to enable easy understanding of the present invention, components may be depicted on a scale that is different to the actual scale .

[0014] Figs. 1A, IB and 1C respectively illustrate an XY

sectional view, an XZ sectional view, and a YZ

sectional view of an optical apparatus 100 according to a first embodiment of the present invention. Note that, in Fig. 1C, black circles in the drawing indicate optical axes of respective lens included in a lens array optical system.

[0015] he optical apparatus 100 includes a light source 101, a lens array optical system (imaging optical system) 102, and a photosensitive portion 103. The lens array optical system 102 includes a first lens array 107, a light blocking member 108, and a second lens array 109.

[0016] The light source 101 includes a plurality of light- emitting points that are arrayed at regular intervals along a Y direction (hereunder, referred to as "main array direction") in which a plurality of lenses

included in the first lens array 107 are mainly arrayed. Although an LED is used as each light-emitting point of the light source 101 in the present embodiment, the present invention is not limited thereto, and, for example, an organic EL device may be used as the

respective light-emitting points.

The lens array optical system 102 includes a lens array that is arrayed in a single row in a Z direction

(hereunder, referred to as "sub-array direction") that is perpendicular to an optical axis direction (X

direction) of the lens array optical system 102 and the main array direction (Y direction) . The lens array optical system 102 is configured so as to perform erect equal-magnification imaging with respect to the main array direction (first direction) and to perform

inverted imaging with respect to the sub-array

direction (second direction). Note that, an array pitch P is 0.76 mm in the main array direction of the lens array optical system 102.

With regard to the photosensitive portion 103, for example, a photosensitive drum is used in an image forming apparatus.

The interval between LEDs of the light source 101 is several tens of μπι, and since this interval is

adequately small in comparison to the array pitch P of the lens array optical system 102 that is at least several hundreds of μπι, it can be considered that the LEDs are disposed substantially continuously.

Accordingly, a light flux that is emitted from a single LED in the light source 101 is converged at one point on the photosensitive portion 103 even though the light flux passes through a plurality of lenses arranged in the main array direction. For example, in Fig. 1A, a light flux emitted from an LED (Pi) converges at Pi', and a light flux emitted from an LED (P2) converges at P2 ' . Because of this characteristic, exposure that corresponds to the light emission of the light source is enabled.

[0018] ext, the 'lens array optical system 102 will be

described.

[0019] he first lens array 107 is configured so that a

plurality of first lenses (hereunder, may also be described as "Gl") 107a, 107b, ... are arrayed.

Similarly, the second lens array 109 is configured so that a plurality of second lenses (hereunder, may also be described as "G2") 109a, 109b, ... are arrayed.

Lenses included in the first lens array 107 and the second lens array 109, respectively, form pairs, and the optical axes of the lenses forming the pairs are configured so as to match with each other.

[0020] Fig. 2 illustrates a schematic sectional view at a

section (hereinafter, described as "main array

section") that is parallel to the main array direction and optical axis direction of one portion 102a of the lens array optical system 102, and at a section

(hereinafter, described as "sub-array section") that is parallel to the sub-array direction and the optical axis direction.

[0021] he one portion 102a of the lens array optical system includes the first lens 107a, a portion of the light blocking member 108, and the second lens 109a that are disposed so as to be aligned with each other. A section that is perpendicular to the optical axes of the first lens 107a and the second lens 109a is a rectangular shape. The effective diameter of a surface (hereunder, referred to as "G1R1 surface") on the light source 101 side of the first lens 107a and a surface (hereunder, referred to as "G2R2 surface") on the photosensitive portion 103 side of the second lens 109a is 0.76 mm. On the other hand, the effective diameter of a surface (hereunder, referred to as "G1R2 surface") on the light blocking member 108 side of the first lens 107a and a surface (hereunder, referred to as "G2R1 surface") on the light blocking member 108 side of the second lens 109a is 0.69 mm. That is, the effective diameters of the respective surfaces of the lenses are different. Note that, the term "lens surface" as used according to the present invention refers to an

effective region (effective surface) that contributes to imaging on the lens.

A light scattering portion (ghost light suppressing portion) is provided between adjacent lenses. More specifically, a light scattering portion 110 is

provided between the G1R2 surface of the first lens 107a and the G1R2 surface of an unshown first lens adjacent to the first lens 107a. Similarly, the light scattering portion 110 is also provided between the G2R1 surface of the second lens 109a and the G2R1 surface of an unshown second lens adjacent to the second lens 109a. The light blocking member 108 of the present embodiment has a plurality of openings

penetrating therethrough in the optical axis direction that correspond to the number of lenses included in the lens array, and light blocking walls between adjacent openings are positioned between the optical axes of adjacent lenses and are disposed so as to be aligned with the light scattering portion 110.

The light blocking member 108 is disposed between the optical axes of adjacent lenses in the main array section.

Note that the light blocking member 108 may also have a configuration in which light blocking plates are inserted and fixed at regular intervals in a frame that extends in the main array direction so as to define positions in the main array direction.

The first lenses 107a, 107b, ... and the second lenses 109a, 109b, ... are joined, respectively, to form the lens arrays 107 and 109.

ith regard to the main array direction, a light flux emitted from one LED of the light source 101 passes through the first lens 107a, and thereafter temporarily forms an image on an intermediate imaging surface 105. Thereafter, the light flux passes through the second lens 109a and imaging of an erect equal-magnification image on the photosensitive portion 103 is performed based thereon.

In this case, the light blocking member 108 and light scattering portion 110 serve to reduce a light flux towards, for example, the second lens 109b which has a different optical axis, that is, serve to reduce ghost light, after the light flux has passed through the first lens 107a.

Note that the system from the object surface (in this case, the light source 101) to the intermediate imaging surface 105 is referred to as a first optical system, and the system from the intermediate imaging surface 105 to an image plane (in this case, the photosensitive portion 103) is referred to as a second optical system. The first lens array forms an intermediate image of an object in the main array section, and the second lens array re-images the intermediate image of the object in the main array section.

With regard to the sub-array direction, a light flux emitted from the light source 101 passes through the first lens 107a, and thereafter passes through the second lens 109a without forming an image on the intermediate imaging surface 105, and imaging of an inverted image on the photosensitive portion 103 is performed based thereon.

As will be understood from Fig. 2, by configuring the optical system for the sub-array direction as an inverted imaging system, the angle for capturing light can be enlarged with respect to the sub-array direction while maintaining the imaging performance, and

compatibility can be achieved between the imaging light amount and the imaging performance.

Optical design values of the lens array optical system according to the present embodiment are as shown in the following Table 1.

[0024] Table 1

[0025] Here, a point of intersection between each lens surface and the optical axis is taken as an origin, and the optical axis direction is taken as the X axis. Further, the main array direction is taken as the Y axis, and the sub-array direction is taken as the Z axis.

Furthermore, in Table 1, "E-x" means "xl0^~x".

[0026] The G1R1 surface, G1R2 surface, G2R1 surface and G2R2 surface are each formed of an anamorphic aspheric surface, and the shape of the aspheric surface is shown by the following expression (1).

[0027]

[0028]Here, Ci,_j (i, j = 0, 1, 2...) is an aspheric surface

coefficient.

[0029] According to the lens array optical system disclosed in PTL 1, because the light blocking member is not fitted into the lens array, there is the advantage that

assembly is easy. However, if an arrangement error occurs at the time of assembly or there is a difference in the linear expansion coefficients between the lens arrays and the light blocking member at a time that the ambient temperature fluctuates, it is conceivable that, as a result, the relative position between the lens arrays and the light blocking member will deviate from the ideal position. There is thus the possibility that the light blocking member will block a desired imaging light flux, or conversely, will allow the unwanted ghost light to pass through.

[0030] This problem will now be described specifically using Figs. 3A and 3B that are described hereunder.

[0031] Fig. 3A is a schematic sectional view along the main

array direction in a case where a relative position between the lens arrays and the light blocking member of an optical apparatus 200 according to the

conventional technology is the ideal position. [0032] When the relative position between the lens arrays and the light blocking member is the ideal arrangement (the components are disposed in accordance with the design) , an imaging light flux K emitted from the light source 201 passes through the first lens array 207.

Thereafter, the imaging light flux K is not blocked by the light blocking member 208 and passes through the second lens array 209, and imaging is performed on the photosensitive portion 103 based thereon. On the other hand, a ghost light G that is a light flux that passes between lenses of the lens array is emitted from the light source 201, and is blocked by the light blocking member 208 after passing through the first lens array 207.

[0033] Fig. 3B is a schematic sectional view along the main array direction in a case where the relative position between the lens arrays and the light blocking member of the optical apparatus 200 according to the

conventional technology deviated from the ideal

position.

[0034] As shown in Fig. 3B, in a case where the relative

position between the lens arrays and the light blocking member deviated from the ideal position, it is found that after the imaging light flux K emitted from the light source 201 passes through the first lens array 207, the imaging light flux K is blocked by the light blocking member 208. On the other hand, after the ghost light G emitted from the light source 201 passes through the first lens array 207, the ghost light G passes through the second lens array 209 without being blocked by the light blocking member 208, and imaging is performed on the photosensitive portion 103 based thereon. This leads to a deterioration in the image quality.

[0035] An object of the present invention is to solve the

above described problem in the conventional technology. More specifically, an object of the present invention is to provide a lens array optical system that can prevent blocking of a desired imaging light flux and also prevent the occurrence of unwanted ghost light even if the relative position between a lens array and a light blocking member deviates from an ideal position.

[0036] To solve the above described problem in the

conventional technology, in a lens array optical system according to the present invention a configuration is adopted in which a light scattering portion or a light absorbing portion is provided between lenses of a lens array, and a width of a light blocking member is less than a width of the light scattering portion or a width of the light absorbing portion. As a result, even if the relative position between the lens array and the light blocking member deviates from the ideal position, an effect of preventing blocking of a desired imaging light flux and preventing the occurrence of unwanted ghost light can be obtained.

[0037] ext, the specific configuration of the lens array

optical system according to the present invention will be described.

[0038] Fig. 4A illustrates a schematic sectional view along

the main array direction of the lens array optical system 102 according to the first embodiment of the present invention.

[0039] In this case, a width Bm in the main array direction of the light scattering portion 110 is 0.17 mm, and a width Tm in the main array direction of the light blocking member 108 is 0.1 mm. That is, Bm and Tm satisfy the relation shown by the following expression (2) .

Bm > Tm ... (2)

[0040] That is, the width Bm of the light scattering portion ' 110 along a gap between adjacent lenses is greater than the width Tm of the light blocking member 108 along a gap between adjacent lenses.

[0041] The light scattering portions 110 are provided in the lens array optical system 102. As illustrated in Fig. 4A, the respective light blocking members 108 are disposed so that a center position of the respective light scattering portions 110 and a center position of the respective light blocking members 108 are aligned in the main array direction. Thus, if the relative position between the lens arrays 107 and 109 and the light blocking member 108 is the ideal position, that is, if the relation in expression (2) is satisfied, blocking of the desired imaging light flux K and

imaging of the unwanted ghost light G can be prevented.

[0042] However, in the main array direction, if the relative position between the lens array 107 or 109 and the light blocking member 108 deviates to an extent the light blocking member 108 does not fall within the range of the width in the main array direction of the light scattering portion 110, as illustrated in the aforementioned Fig. 3B, on one hand the desired imaging light flux K is blocked and on the other hand imaging occurs based on the unwanted ghost light G.

[0043] Accordingly, a tolerance AQm of a relative positional deviation along the main array direction between the lens arrays 107 and 109 and the light blocking member 108 is shown by the following expression (3) .

AQm = (Bm-Tm) /2 ... (3)

[0044] In the present embodiment, Bm = 0.17 mm and Tm = 0.1 mm, and hence AQm = 0.035 mm.

Next, a relative positional deviation along the main array direction that accompanies a thermal expansion difference between the lens arrays 107 and 109 and the light blocking member 108 at a time that the ambient temperature fluctuates will be considered specifically.

[0045] First, a linear expansion coefficient XI in the main

array direction of the first lens array 107 and the second lens array 109 is ^'10.0x10⁵(/°C), and a linear expansion coefficient Xs in the main array direction of the light blocking member 108 is 9. OxlO^-5 ( /°C) . These values are standard values in a case where the lens arrays and the light blocking member are made of resin. Note that the linear expansion coefficients in the main array direction of the first lens array 107 and the second lens array 109 may also be different to each other .

The lens array optical system 102 is configured so as to perform exposure across an A4 width (width of 210 mm) . That is, an entire length L in the main array direction of the first lens array 107, the second lens array 109, and the light blocking member 108 is 210 mm. Further, the first lens array 107, the second lens array 109, and the light blocking member 108 are positioned at the respective center portions thereof with respect to the main array direction.

In addition, an operation-guaranteed ambient

temperature of the lens array optical system 102 is

30°C±30°C. This is a standard specification.

[0046] Here, a case will be considered in which the ambient temperature increased by ΔΤ = 30°C. At such time, when the center in the main array direction is taken as a reference, a relative position maximum deviation amount AYmax between the lens arrays 107 and 109 and the light blocking member 108 that arises at both end portions in the main array direction of the lens array optical system 102 is shown by the following expression (4) .

[0047]AYmax = (L/2) x ΔΤ x (XI - Xs)

= (210 mm/2) x 30°C x ( 10.0xl0^"5/°C - 9.0xlO^~5/°C)

= 105 mm x 30°C x ( 10. OxlO^~V°C - 9.0xl0^"5/°C)

= 0.0315 mm ... (4)

[0048 ] Accordingly, a relative positional deviation ΔΥ between the lens arrays 107 and 109 and the light blocking member 108 is 0 mm at the center portion and is 0.0315 mm at both end portions. Further, between the center portion and both end portions, the relative positional deviation ΔΥ between the lens arrays 107 and 109 and the light blocking member 108 is a value between 0 and 0.0315 mm in accordance with the relevant position, and the deviation amount increases in accordance with an increase in the distance from the center portion that is the reference position, and is proportional to the distance from the center portion. The manner in which the relative position deviates is illustrated in Fig. 4B.

[0049] Based on expressions (3) and (4), it is found that the relative position maximum deviation amount AYmax between the lens arrays 107 and 109 and the light blocking member 108 falls within the range of the tolerance AQ . of the relative positional deviation along the main array direction.

Accordingly it is found that, in the lens array optical system 102, even if such a fluctuation in the ambient temperature occurs, blocking of the desired imaging light flux K and occurrence of the unwanted ghost light G can be prevented.

[0050] The above described relation can be generally

represented as shown in the following expression (5). AL x ΔΤ x ΔΧ < AW/2 ... (5)

[0051] Here, AL is the distance to the most distant position from the place at which the lens arrays 107 and 109 and the light blocking member 108 are positioned in the lens array optical system 102. In other words, the most distant position of the light blocking member 108 is the most distant position within a portion that functions as a light blocking member in the light blocking member 108. Further, ΔΤ is a difference between a temperature at the time that the lens arrays 107 and 109 and the light blocking member 108 are positioned and a temperature at the time that the lens array optical system 102 is used. Further, ΔΧ is the larger value between an absolute value of a difference between the linear expansion coefficient of the lens array 107 and the linear expansion coefficient of a member defining a position in the main array direction and the sub-array direction of the light blocking member 108, and an absolute value of a difference between the linear expansion coefficient of the lens array 109 and the linear expansion coefficient of the member defining the position in the main array

direction and the sub-array direction of the light blocking member 108. In addition, AW is a difference (Bm-Tm) between the width Bm of the light scattering portion 110 along a gap between adjacent lenses and the width Tm of the light blocking member 108 along a gap between adjacent lenses.

[0052]At this time, as illustrated in Fig. 4C, a light flux S towards the light scattering portion 110 increases.

Although this kind of scattered light S is not a desired imaging light flux, the scattered light S does not lead to a deterioration of the image since the intensity of the scattered light S is adequately reduced at each position on the image plane as the result of being scattered at the light scattering portion 110.

[0053] Figs. 5A and 5B illustrate a sectional view in the main array direction of the first lens array 107 and the light scattering portion 110, and an enlarged sectional view in the main array direction of the light

scattering portion 110 according to the present

embodiment, respectively.

[0054]As illustrated in Figs. 5A and 5B, the light scattering portion 110 of the present embodiment has a shape in which, for example, 17 triangular prisms having a base a that is 10 μπι and a height h that is 10 μτα are arrayed. By adopting this kind of triangular prism configuration, the advantageous effects are obtained that processing of the light scattering portion 110 is facilitated and the manufacturing costs are lowered. Note that, as the result of thorough studies, the inventors found that the light scattering portion 110 exerts a sufficient scattering effect if the ratio (aspect ratio) h/a of the height h to the base a of the triangular prism is 0.7 or more. Therefore, in the present embodiment an example of the light scattering portion 110 that uses triangular prisms for which the aspect ratio h/a is 1 is described.

[0055] The relation between the widths in the main array

direction of the light blocking member 108 and the light scattering portion 110 has been discussed above. Next, the length in the optical axis direction of the light blocking member 108 will be discussed.

[0056] ig. 6 illustrates a schematic sectional view along the main array direction of the lens array optical system 102 according to the present embodiment.

[0057] Note that, hereunder a case is considered in which it is assumed that the light scattering portion 110 is not provided and the unwanted ghost light G is blocked by the light blocking member 108.

[0058] As illustrated in Fig. 6, after the ghost light G that is emitted from an unshown light source has passed through the lens 107a, the ghost light G is blocked by the light blocking member 108. Note that it is assumed that after the ghost light G passes through the lens 107a, the ghost light G travels towards a certain point Yl on a surface on the lens array 107 side of a light blocking member 108a, a certain point Y2 on a surface on a light blocking member 108b side of the light blocking member 108a, and a point Y3 that is an end portion of the lens 109b.

When a distance along the main array direction from the point Yl to the point Y3 is taken as a, and a distance along the main array direction from the point Y2 to the point Y3 is taken as β , the ghost light G can be

blocked by the light blocking member 108 if the

relation in the following expression (6) is satisfied, > β . . . (6)

[0059] With respect to connecting portions between the lenses, for example, when a width in the main array direction between the lens 107a and the lens 107b is taken as Bm, the width in the main array direction of the light blocking member 108a is taken as Tm, and the lens array period of the lens arrays 107 and 109 is taken as P, the distance β satisfies the relation in the following expression ( 7 ) .

β = P - (Bm/2-Tm/2) - Tm

= P - Bm/2 - Tm/2 ... (7)

[0060] Let an angle formed by a straight line linking the

points Yl, Y2 and Y3 and the optical axis be taken as Θ, and a length of the light blocking member 108 in the optical axis direction be taken as Ls. Further, when a distance between an end portion of a certain lens of the lens array 107, for example, the lens 107b, and an end portion of a lens of the lens array 109 that is opposite the aforementioned certain lens, for example, the lens 109b (i.e. the longest distance in the optical axis direction between opposing surfaces of the first lens array 107 and the second lens array 109) is taken as Lmax, the distance a is expressed as shown in the following expression (8).

[0061]ct = (Lmax/2 + Ls/2) x tanG

= (Lmax/2 + Ls/2) x (P/Lmax)

= P/2 + (P/2) x (Ls/Lmax) ... (8)

[0062] Thus, the relation shown by the following expression

(9) is obtained based on expressions (6), (7) and (8).

Bm + Tm > P x (1 - (Ls/Lmax) ) ... (9)

[0063] For example, the lens array optical system 102

according to the present embodiment is designed so that Bm is 0.17 mm, Tm is 0.10 mm, P is 0.76 mm, Ls is 1.90 mm, and Lmax is 2.33 mm.

Accordingly,

Bm + Tm = 0.27 mm, and

P x (1 - (Ls/Lmax) ) = 0.14 mm

and it is thus found that the lens array optical system 102 according to the present embodiment satisfies the relation in expression (9).

That is, it is found that in the lens array optical system 102 according to the present embodiment, the light blocking member 108 can block the ghost light G as illustrated in Fig. 6.

[ 0064 ] Further, let a minimum inter-surface interval between a certain lens of the lens array 107, for example, the lens 107a, and an opposing lens of the lens array 109, for example, the lens 109a (i.e. the shortest distance in the optical axis direction between opposing surfaces of the first lens array 107 and the second lens array 109) be taken as Lmin. In this case, the length Ls in the optical axis direction of the light blocking member 108 and Lmin can satisfy the relation in the following expression ( 10 ) .

Ls < Lmin ... (10)

[0065] That is, the length Ls in the optical axis direction of the light blocking member can be less than the minimum inter-surface interval Lmin between a certain lens of the first lens array and a lens facing the

aforementioned certain lens of the second lens array.

[0066] By preparing the lens arrays 107 and 109 and the light blocking member 108 so as to satisfy the relation in expression (10), the light blocking member and the lens arrays do not interfere with each other even if the lens arrays and the light blocking member are assembled while sliding the respective members with respect to each other in the main array direction. Consequently, assembly of the lens array optical system 102 is easy. In contrast, when the relation in expression (10) is not satisfied, if it is attempted to assemble the lens arrays and the light blocking member while mutually sliding the members with respect to each other in the main array direction, the lens arrays and the light blocking member will interfere with each other. There is thus the possibility that a problem such as breakage will occur.

[0067] he width in the main array direction of the light

blocking member 108 and the light scattering portion 110 as well as the length in the optical axis direction of the light blocking member 108 have been discussed thus far. Next, the effective arrangement of the light scattering portion 110 and the light blocking member 108 of the present embodiment will be discussed.

[0068] Fig. 7 illustrates a schematic sectional view at a main array section of the lens array optical system 102 according to the first embodiment of the present invention that includes the light scattering portion 110 and the light blocking member 108.

[0069] ote that in the following description it is assumed that triangular prisms having an aspect ratio of 0.7 or more as illustrated in Figs. 5A and 5B are provided in the light scattering portion 110.

[0070] First, with respect to the triangular prisms of the

light scattering portion 110, there are cases in which edge-like ridge lines are formed at an apex and a base, ridge lines are formed in which a flat portion is intentionally provided to achieve manufacturing

advantages, and ridge lines are formed that are rounded by a transfer and replication process such as in the case of injection molding. Consequently, there is a possibility that light that is transmitted through the vicinity of the ridge lines of the triangular prisms will expand radially, and there is a necessity to ensure unwanted ghost light does not arise. [0071] For example, as a case in which scattered light is incident on a lens without being blocked, a case will be considered in which scattered light is transmitted through a light scattering portion llOab that is between the lenses 107a and 107b of the first lens array 107 in Fig. 7, and travels in the direction of the lens 109a of the second lens array 109.

A light flux emitted from an unshown light source is transmitted through the vicinity of prism ridge lines of the light scattering portion llOab between the lenses 107a and 107b of the first lens array 107, and the light is emitted radially. The intensity of such light is sufficiently lowered as a result of the light being incident again on the light scattering portion and scattered after the light is blocked at a short- side face and a long-side face of a light blocking member 108ab that faces the light scattering portion llOab in the optical axis direction or after the light straddles the lens 109a and is blocked by an adjacent light blocking member. Accordingly, in the case of such light rays, the scattered light is blocked, and hence the light rays do not lead to deterioration of an image .

[0072] However, a case can also be considered in which

scattered light is incident on a facing lens without being blocked. As this kind of case, a case will be considered in which scattered light is transmitted through a light scattering portion llObc that is between the lenses 107a and 107b of the first lens array 107 in Fig. 7, and travels in the direction of the lens 109b of the second lens array 109.

[0073] Light rays emitted from an unshown light source are transmitted through the vicinity of prism ridge lines of the light scattering portion llObc between lenses 107b and 107c of the lens array 107, and the light is emitted radially. At this time, the light is incident on the lens surface of the facing lens 109b without being blocked by the light blocking member 108bc that faces the light scattering portion llObc, and there is the possibility that the light will become unwanted ghost light SG. More specifically, when a corner portion on the lens 107 side of the light blocking member 108 in Fig. 7 is taken as Y4, and the two end portions of the lens 109 are taken as Y5 and Y6, light that is not blocked by the light blocking member 108bc facing the light scattering portion llObc and is incident on the lens surface of the facing lens 109b within a region between a line segment linking Y4 and Y5 and a line segment linking Y4 and Υβ becomes the unwanted ghost light SG.

That is, a condition that light is incident within a predetermined region that takes the corner portion Y4 of the light blocking member 108 as a starting point can be considered.

[0074] he line segment linking Y4 and Y5 has a critical angle Θ1 as shown in expression (11) with respect to the optical axis.

Θ1 = tan^"1 (AQm/ ( (Lmax + Ls)/2)) ...(11)

Further, the line segment linking Y4 and Y6 has a critical angle Θ2 as shown in expression (12) with respect to the optical axis.

Θ2 = tan^"1 ( (P - AQm) / ( (Lmax + Ls) /2) ) ... (12)

[0075] In the present embodiment, the lens array optical

system 102 is designed so that Bm is 0.17 mm, Tm is

0.10 mm, P is 0.76 mm, Ls is 1.90 mm, Lmax is 2.33 mm, and AQm = 0.035 mm.

It is thus determined that,

Θ1 = 0.95° and

Θ2 = 20.5°.

[0076] To suppress the unwanted ghost light SG that arises

from the vicinity of prism ridge lines of the light, scattering portion 110, light rays from the light scattering portion 110 can be prevented from being incident on the region defined by the critical angles Θ1 and Θ2.

[0077] Figs. 8A, 8B and 8C illustrate enlarged views of the

light scattering portion 110 and the light blocking member 108.

[ 0078 ] Reference character Bm denotes the width of the light scattering portion 110, and reference character Tm denotes the width of the light blocking member 108.

Further, reference character Be denotes a distance between ridge lines of the first prisms from the two ends in the light scattering portion 110. That is, this means that the prism ridge lines that are formed in the light scattering portion 110 are only included within the width Be.

[0079] An effective arrangement of the light scattering

portion 110 and the light blocking member 108 for suppressing the unwanted ghost light SG that is

incident on an unshown facing lens will be described based on Figs. 8A, 8B and 8C.

[0080] Fig. 8A illustrates a case in which the width Be is

greater than the width Tm of the light blocking member 108. In Figs. 8A, 8B and 8C, a region indicated by a dotted line is a region, in which light becomes the ghost light SG. Thus, it is found that various light rays are generated that extend radially from the light scattering portion 110, and the ghost light SG arises.

[0081] Next, Fig. 8B illustrates a case where the width Be is less than the width Tm of the light blocking member 108. To satisfy this condition, the triangular prisms of the light scattering portion 110 are formed near to the light blocking member 108. As illustrated in Fig. 8B, it is found that, in comparison to the case illustrated in Fig. 8A, light that is incident inside the region indicated by dotted lines, that is, light rays that become the ghost light SG, are suppressed to a large degree. This is because, as the result of arranging the prism ridge lines close to the light blocking member 108, light rays can be received and blocked at the short-side face of the light blocking member 108. Thus, as the result of such studies the inventors found that the ghost light SG can be effectively suppressed by making the width Be less than the width Tm of the light blocking member 108.

That is, the ghost light SG can be effectively

suppressed by satisfying the relation in expression (13).

Tm > Be ... (13)

In the present embodiment, since Tm is 0.10 mm, Be can be made equal to or less than 0.10 mm.

[ 0082 ] Further , it is necessary that the scattering face and the light blocking member satisfy the relation shown in expression (10) with respect to the distance in the optical axis direction.

In the present embodiment, since the aspect ratio h/a of the respective triangular prisms is 1, it is

necessary that the maximum height of each triangular prism is at least twice the value of AQm. That is, since AQm = 0.035 mm, it is necessary for the maximum height of the triangular prisms to be 0.07 mm. In the present embodiment, since Ls is 1.90 mm and Lmax is 2.33 mm, the maximum height of the triangular prisms can be a height up to 0.215 mm. Accordingly, the triangular prisms can be arranged without interference arising in the optical axis direction.

[0083] In addition, Fig. 8C illustrates an ideal arrangement relation between the light scattering portion 110 and the light blocking member 108. In this case the light scattering portion 110 is formed so that the width Be is less than the width Tm of the light blocking member 108, and ridge lines of the triangular prisms fall within a region that is surrounded by line segments corresponding to the critical angles Θ2 on both sides of the light blocking member 108 and the short-side face of the light blocking member 108. As a result, light rays Sh emitted from the light scattering portion 110 can be blocked at the short-side face of the light blocking member 108, and the light rays Sh that escape from the corner portion of the light blocking member 108 can also be blocked at the long-side face of an adjacent light blocking member 108.

[0084] In the lens array optical system according to the

present embodiment, as illustrated in Figs. 5A and 5B, although the base a of the triangular prisms that are formed is made 10 urn, the length of the base a is not limited thereto as long as the aspect ratio is retained. Since the number of prism ridge lines to be formed is reduced by widening the prism interval, the light rays that are transmitted through the vicinity of prism ridge lines also decrease, and thus ghost light can also be suppressed.

[0085] The lens array optical system according to the present embodiment has a configuration in which the lens arrays are disposed as only one row in the sub-array direction. However, it is not necessary to limit the lens arrays to one row in the sub-array direction, and even in a configuration in which the lens arrays are disposed in a plurality of rows, the advantageous effects of the present invention can be obtained as long as -the

configuration of the present invention is provided in at least one row thereof.

[0086] Although the lens array optical system according to the present embodiment performs erect equal-magnification imaging with respect to the main array direction, the present invention, is not limited thereto. Further, although the lens array optical system according to the present embodiment performs inverted imaging with respect to the sub-array direction, the present invention is not limited thereto.

[ 0087 ] Although the lens array optical system according to the present embodiment includes two lens array and one light blocking member, the number of lens arrays and light blocking members is not limited thereto as long as the configuration of the present invention is

satisfied.

For example, an exemplary embodiment can also be

considered in which a third lens array is provided along the intermediate imaging surface in addition to the first lens array that forms an intermediate image of an object in the main array section and the second lens array that re-images the intermediate image in the main array section.

[0088] In the lens array optical system according to the

present embodiment, the lens arrays and the light blocking member are positioned at the respective center portions thereof with respect to the main array

direction. However, it is not necessary to position the lens arrays and the light blocking member with their respective center portions, and as long as the configuration of the present invention is satisfied, for example, the lens arrays and the light blocking member may be positioned at the respective end portions thereof.

[0089] According to the lens array optical system of the

present embodiment, one light blocking member is

provided between two lens arrays, and a light

scattering portion is provided on a surface on the light blocking member side of each lens array. However, it is not necessary for the present invention to be limited to this configuration. For example, as long as the configuration of the present invention is satisfied, a light scattering portion may be provided on a surface on an opposite side to the light blocking member side of each lens array, or a light scattering portion may be provided on only a surface on the light blocking member side of one lens array.

[0090] Figs. 9A, 9B and 9C illustrate an XY sectional view, an XZ sectional view, and a YZ sectional view,

respectively, of an optical apparatus .300 according to a second embodiment of the present invention.

[0091] The optical apparatus 300 of the present embodiment takes the form of an image reading apparatus. That is, the optical apparatus 300 includes an original 301 that is an object surface, a lens array optical system 302, a sensor portion 303 that is an image plane, and a platen 304. The lens array optical system 302 includes a first light blocking member 308a, a first lens array 307, a second lens array 309, and a second light blocking member 308b. That is, in the present

embodiment the light blocking member 308a (308b) is arranged on an incident side or an emission side of the lens array optical system 302. In other words, the light blocking member 308a is arranged further to the object side than the first lens array 307, and the light blocking member 308b is arranged further to the image side than the second lens array 309. That is, at least one lens array 307 (309) among the lens array 307 and lens array 309 can be arranged on a side that does not face the other lens array 309 (307).

[0092] The lens array optical system 302 is constructed by

arranging a plurality of lenses at a period of 1.50 mm in the main array direction. The lens array optical system 302 is configured so that lenses are arranged in two rows in a staggered arrangement at a period of 1.50 mm in a sub-array direction (Z direction) that is perpendicular to an optical axis direction (X

direction) and a main array direction (Y direction) of the lens array optical system 302. Note that, only a row on a lower side (B-row in Fig. 9C) among the two rows in the sub-array direction is taken into consideration in the following description. Further, it is assumed that the other row (A-row in Fig. 9C) has a similar configuration to that of the B-row.

The lens array optical system 302 is configured so as to perform erect equal-magnification imaging with respect to the main array direction, and is configured so as to perform erect imaging with respect to the sub- array direction.

[0093] A light flux emitted from an unshown illumination

portion is transmitted through the platen.304 to be incident on the original 301, and is then reflected. The light flux that was reflected by the original 301 is transmitted through the lens array optical system 302 and is incident on the sensor portion 303 and detected thereby. The light flux that was reflected by the original 301 is converged at a single point on the sensor portion 303 even if the light flux has passed through a plurality of lenses arranged in the main array direction. For example, in Fig. 9A, a light flux emitted from a light-emitting point C converges at C, and a light flux emitted from a light-emitting point D converges at D'.

[0094] Next, the lens array optical system 302 will be

described.

[0095] The first lens array 307 is configured so that a

plurality of first lenses (hereunder, may be described as "Gl") 307a, 307b ... are arrayed. Similarly, the second lens array 309 is configured so that a plurality of second lenses (hereunder, may also be described as "G2") 309a, 309b ... are arrayed.

[0096] Fig. 10 illustrates a schematic sectional view along each of the main array direction and the sub-array direction of one portion 302a of the lens array optical system 302.

[0097] The one portion 302a of the lens array optical system includes a portion of the first light blocking member 308a, the first lens 307a, the second lens 309a, and a portion of the second light blocking member 308b that are disposed on the same optical axis. Note that a case will be considered in which the light blocking members are disposed between two rows of lens arrays in the sub-array direction. That is, in the present embodiment, since only the lower row among the two rows in the sub-array direction is being taken into

consideration, in the sectional view in the sub-array direction, the light blocking members 308a and 308b are disposed only on the upper side of the lenses 307a and 309a in the drawing. All of the lens surfaces have a circular shape. The effective diameter of a surface

(hereunder, referred to as "G1R1 surface") on the original 301 side of the first lens 307a and a surface

(hereunder, referred to as "G2R2 surface") on the sensor portion 303 side of the second lens 309a is 1.20 mm. Similarly, the effective diameter of a surface

(hereunder, referred to as "G1R2 surface") on the second lens 309a side of the first lens 307a and a surface (hereunder, referred to as "G2R1 surface") on the first lens 307a side of the second lens 309a is also 1.20 mm. An opening cross-section of all the light blocking members is circular, and an opening diameter of both faces of the first light blocking member 308a and of both faces of the second light blocking member 308b is 1.30 mm.

Note that a light scattering portion 310 is provided between the G1R1 surface of the first lens 307a and the G1R1 surface of an unshown adjacent first lens. The light scattering portion 310 is also provided between the G1R2 surface of the first lens 307a and the G1R2 surface of an unshown adjacent first lens. Likewise, the light scattering portion 310 is also provided between the G2R1 surface of the second lens 309a and the G2R1 surface of an unshown adjacent second lens. The light scattering portion 310 is also provided between the G2R2 surface of the second lens 309a and the G2R2 surface of an unshown adjacent second lens. The first lenses 307a, 307b ... and the second lenses 309a, 309b ... are joined, respectively, to form the lens arrays 307 and 309.

[0098] With respect to the main array direction, a light flux that is reflected by the original 301 passes through the platen 304 and the first lens 307a, and thereafter temporarily forms an image on an intermediate imaging surface 305. Thereafter, the light flux passes through the second lens 309a and imaging of an erect equal- magnification image on the sensor portion 303 is performed based thereon.

With respect to the sub-array direction also, a light flux that is reflected by the original 301 passes through the platen 304 and the first lens 307a, and thereafter temporarily forms an image on the

intermediate imaging surface 305. Thereafter, the light flux passes through the second lens 309a and imaging of an erect image on the sensor portion 303 is performed based thereon.

In this case, the light blocking members 308a and 308b and the light scattering portion 310 serve to reduce a light flux towards a second lens which has a different optical axis, that is, serve to reduce ghost light, after the light flux has passed through the first lens 307a.

Note that the system from the object surface (in this case, the original 301) to the intermediate imaging surface 305 is referred to as a first optical system, and the system from the intermediate imaging surface 305 to an image plane (in this case, the sensor portion 303) is referred to as a second optical system.

[0099] Optical design values of the lens array optical system according to the present embodiment are as shown in the following Table 2.

[0100] Table 2

[0101] Here, a point of intersection between each lens surface and the optical axis is taken as an origin, and the optical axis direction is taken as the X axis. Further, the main array direction is taken as the Y axis, and the sub-array direction is taken as the Z axis.

Furthermore, in Table 2, "E-x" means "xl0^"x".

[0102] he G1R1 surface, G1R2 surface, G2R1 surface and G2R2 surface are each formed by an anamorphic aspheric surface, and the shape of the aspheric surface is shown by the following expression (14).

[0103]

Here, Ry and Rz represent curvature radii, ky and kz represent conic constants, and Bi and Ci (i = 1, 2, 3, 4, 5...) represent aspheric surface coefficients.

[0104] In the lens array optical system 302 according to the second embodiment also, similarly to the lens array optical system 102 according to the first embodiment, a light scattering portion or a light absorbing portion is provided between lenses of the lens arrays. Further, a configuration is adopted in which the width of the light blocking member is less than the width of the light scattering portion or the light absorbing portion. As a result, even if the relative position between the lens array and the light blocking member deviates from an ideal position, an effect of preventing blocking of a desired imaging light flux and of preventing the occurrence of unwanted ghost light can be obtained.

[0105] Next, the specific configuration of the lens array

optical system according to the present invention will be described.

[0106] Fig. 11A illustrates a sectional view along the main array direction of the lens array optical system 302 according to the second embodiment of the present invention. Note that the second light blocking member 308b is not illustrated in Fig. 11A.

[0107] In a case such as in the present embodiment in which the openings of the light blocking members 308a and 308b are not a rectangular shape, a width Bm in the main array direction of the light scattering portion 310 and a width Tm in the main array direction of the light blocking member 308a are defined by a section that is perpendicular to the sub-array direction at which a distance in the main array direction between the relevant lens surface and the relevant light blocking member is shortest. That is, as illustrated by a chain line LI in Fig. 9C, the openings are defined by a section that is perpendicular to the sub-array direction that includes the optical axis of the lens array on the upper row side.

[0108] In this case, the width Bm in the main array direction of the light scattering portion 310 is 0.30 mm, and the width Tm in the main array direction of the light blocking member 308a is 0.10 mm. That is, Bm and Tm satisfy the relation shown by the following expression (15).

Bm > Tm ... (15)

[0109] That is, the width Bm of the light scattering portion

310 along a gap between adjacent lenses is greater than the width Tm of the light blocking member 308a along a gap between adjacent lenses.

[0110] The light scattering portions 310 are provided in the lens array optical system 302. As shown in Fig. 11A, the respective light blocking members 308 are disposed so as to be aligned with a center position of the respective light scattering portions 310. Thus, when the relative position between the lens arrays 307 and 309 and the light blocking member 308a is the ideal position, if the relation in expression (12) is satisfied, blocking of the desired imaging light flux K and forming of an image by the unwanted ghost light G can be prevented.

[0111] However, if the relative position between the lens

array 307 or 309 and the light blocking member deviates such that the light blocking member 308a exceeds the width in the main array direction of the light

scattering portion 310, on one hand the desired imaging light flux K is blocked and on the other hand imaging of the unwanted ghost light G is performed.

[0112] Accordingly, a tolerance AQm of a relative positional deviation along the main array direction between the lens arrays 307 and 309 and the light blocking member 3.08a is shown by the following expression (16) .

AQ = (Bm - Tm) /2 = 0.10 mm ... (16)

[0113] ext, a relative positional deviation along the main

array direction that accompanies thermal expansion of the lens arrays 307 and 309 and the light blocking member 308a at a time that the ambient temperature fluctuates will be considered specifically.

[0114] First, a linear expansion coefficient XI in the main

array direction of the first lens array 307 and the second lens array 309 is 10. OxlO^-5 ( /°C) , and a linear expansion coefficient Xs in the main array direction of the light blocking member 308a is 9. OxlO^-5 ( /°C) . These values are standard values in a case where the lens arrays and the light blocking member are made of resin. The lens array optical system 302 is configured so as to perform exposure across an A4 width (width of 210 mm) . That is, an entire length L in the main array direction of the first lens array 307, the second lens array 309, and the light blocking member 308a is 210 mm. Further, the first lens array 307, the second lens array 309, and the light blocking member 308a are positioned at one of the end portions thereof with respect to the main array direction.

In addition, an operation-guaranteed ambient

temperature of the lens array optical system 302 is 30°C±30°C. This is a standard specification.

[0115] Here, a case will be considered in which the ambient temperature increased by ΔΤ = 30°C. At such time, a relative position maximum deviation amount AYmax between the lens arrays 307 and 309 and the light blocking member 308a that arises at an end portion that is on an opposite side to the end portion at which the lens arrays 307 and 309 and the light blocking member 308a are positioned is shown by the following

expression ( 17 ) .

[0116]AYmax = L x ΔΤ x (Xl-Xs)

= 210 mm x 30°C x ( 10.0xl0^"V°C - 9.0xl0^~V°C)

= 0.063 mm ... (17)

[ 0117.] Accordingly, a relative positional deviation ΔΥ between the lens arrays 307 and 309 and the light blocking member 308a is 0 mm at the positioned end portion and is 0.063 mm at the end portion on the opposite side. Further, between the positioned end portion and the end portion on the opposite side, the relative position deviates by a value between 0 and 0.063 mm in

accordance with the relevant position, and the

deviation amount increases in accordance with an increase in the distance from the positioned end portion, and is proportional to the distance from the positioned end portion. The manner in which the relative position deviates is illustrated in Fig. 11B.

[0118] Based on expressions (16) and (17), it is found that the relative position maximum deviation amount AYmax between the lens arrays 307 and 309 and the light blocking member 308a falls within the range of the tolerance AQm of the relative positional deviation along the main array direction.

Accordingly it is found that, in the lens array optical system 302, even if such a fluctuation in the ambient temperature occurs, blocking of the desired imaging light flux K and occurrence of the unwanted ghost light G can be prevented.

[0119] The lens array optical system 302 according to the

present embodiment is configured so that lenses are arranged in two rows in a staggered arrangement in the sub-array direction (Z direction).

Accordingly, a relative positional deviation along the sub-array direction between the lens arrays and the light blocking member can also be considered.

[0120] In a case such as in the present embodiment in which the shapes of the openings of the light blocking members 308a and 308b are not rectangular, a width Bs in the sub-array direction of the light scattering portion is defined as follows. That is, the light scattering portion is disposed at a position at which a distance between a lens in the A-row and a lens in the B-row that is adjacent to the aforementioned lens in the A-row is the shortest distance therebetween, and the width Bs in the sub-array direction of the light scattering portion is defined by a component in the sub-array direction that is projected on a sub-array section of the light scattering portion. That is, the width Bs in the sub-array direction of the light scattering portion and the width Ts in the sub-array direction of the light blocking member are defined by a section that is perpendicular to the main array

direction. That is, the aforementioned widths Bs and Ts are defined by a section (sub-array section) that is perpendicular to the main array direction that includes the optical axis of the lens array on the upper row side, as illustrated by a chain line L2 in Fig. 9C.

[0121] In this case, the width Bs in the sub-array direction of the light scattering portion is 0.30 mm, and the width Ts in the sub-array direction of the light blocking member is 0.10 mm. That is, Bs and Ts satisfy the relation shown by the following expression (18). Bs > Ts ... (18)

[ 0122 ] Accordingly, similarly to the discussion regarding

expression (16), when it is assumed that the light blocking member is disposed at the center portion of the light scattering portion, a tolerance AQs of a relative positional deviation along the sub-array direction between the lens arrays and the light blocking member is shown by the following expression (19).

AQs = (Bs - Ts)/2 = 0.10 mm ... (19)

[0123] Let us assume that a relative positional deviation ΔΖ along the sub-array direction between a lens array and a light blocking member has arisen accompanying an arrangement error at the time of assembly. Even in this case, as long as the relation ΔΖ < AQs is

satisfied, an effect that prevents blocking of a desired imaging light flux and also prevents generation of unwanted ghost light can be obtained with respect to the sub-array direction also.

[0124] Although the optical apparatus 300 according to the present embodiment takes the form of an image reading apparatus, naturally the present embodiment is also applicable to an image forming apparatus.

[0125] The lens array optical system 302 according to the

present embodiment has a configuration in which one of the two light blocking members 308a and 308b is

provided between the first lens array 307 and the original 301, and the other of the two light blocking members 308a and 308b is provided between the second lens array 309 and the sensor portion 303. However, it is not necessary to limit the lens array optical system 302 according to the present embodiment to this

configuration, and as long as the configuration of the present invention is satisfied, the advantageous effects of the present invention can also be obtained with, for example, a configuration that includes only either one of the light blocking members.

[0126] According to the lens array optical system 302 of the present embodiment, the configuration of the present invention has been discussed with respect to only one row of two rows in the sub-array direction, and it has been assumed that the other row has the same

configuration. However, it is not necessary to limit the lens array optical system 302 according to the present embodiment to this configuration, and the advantageous effects of the present invention can be obtained even when only one of the rows satisfies the configuration of the present invention.

[0127] ote that, besides including either a light scattering portion or a light absorbing portion, the ghost light suppressing portion may include a reflection portion for reflecting unwanted light to prevent the unwanted light from reaching the image plane. The reflection portion is constructed by, for example, forming a reflective film between the lens surfaces.

[ 0128 ] Further , the advantageous effects of the present

invention can be obtained as long as at least one of the first and second lens arrays has a ghost light suppressing portion.

[0129] Finally, a black and white image forming apparatus, a color image forming apparatus, and an image reading apparatus that are equipped with the lens array optical system according to the present invention will be described.

[0130] Fig. 12A illustrates a schematic sectional view of a black and white image forming apparatus 5 that is equipped with the lens array optical system according to the present invention.

[0131] The image forming apparatus 5 receives code data Dc that is input from an external apparatus 15 such as a personal computer. The code data Dc is converted to image data (dot data) Di by a printer controller 10 provided in the apparatus. The image data Di is input to an exposure unit 1 that is equipped with the lens array optical system according to the present invention. The exposure unit 1 then emits an exposure light 4 that is modulated in accordance with the image data Di, and a photosensitive surface of a photosensitive drum 2 is exposed by the exposure light 4.

[0132] The photosensitive drum 2 that serves as an

electrostatic latent image bearing body (photosensitive body) is rotated clockwise by a motor 13. A charging roller 3 which causes the surface of the photosensitive drum 2 to be uniformly charged is provided on the upper side of the photosensitive drum 2 so as to be in

contact with the surface of the photosensitive drum 2. The surface of the photosensitive drum 2 that has been charged by the charging roller 3 is irradiated with the exposure light 4 by the exposure unit 1.

[0133] As described above, the exposure light 4 is modulated based on the image data Di, and an electrostatic latent image is formed on the photosensitive surface of the photosensitive drum 2 by irradiation of exposure light 4 thereon. The thus-formed electrostatic latent image is developed as a toner image by a developing device 6 which is arranged so as to come in contact with the photosensitive drum 2 at a position that is further on the downstream side in the rotational direction of the photosensitive drum 2 than the position irradiated with the exposure light 4.

[0134] The toner image developed by the developing device 6 is transferred onto a sheet 11 that serves as a transfer material on the lower side of the photosensitive drum 2 by a transfer roller 7 (transfer device) which is arranged so as to oppose the photosensitive drum 2.

Although the sheet 11 is contained in a sheet cassette 8 disposed in front of (on the right side in Fig. 12A) the photosensitive drum 2, it is also possible to feed the sheet 11 manually. A sheet feeding roller 9 is arranged at an end portion of the sheet cassette 8 so as to feed the sheet 11 in the sheet cassette 8 to a conveying path.

[0135] The sheet 11 onto which the unfixed toner image has

been transferred as described above is further conveyed to a fixing device 16 which is disposed on the rear side (on the left side in Fig. 12A) of the

photosensitive drum 2. The fixing device 16 includes a fixing roller 12 which includes therein a fixing heater (not shown) , and a pressure roller 18 that is arranged so as to be in pressure contact with the fixing roller 12. The sheet 11 that has been conveyed from a

transfer portion 17 is heated while being pressurized at a pressure contact portion between the fixing roller 12 and the pressure roller 18, to thereby fix the unfixed toner image onto the sheet 11. Further, sheet discharging rollers 14 are arranged to the rear of the fixing device 16, and discharge the sheet 11 on which the toner image was fixed to outside of the image forming apparatus 5.

[0136] The printer controller 10 also controls the motor 13

and other components within the image forming apparatus 5, and not just the conversion of data.

[0137] By using the lens array optical system according to the present invention, the exposure unit can be made

compact, and as a result an effect such that the

overall image forming apparatus can also be made

compact can be obtained.

[0138] Fig. 12B illustrates a schematic sectional view of a

color image forming apparatus 33 equipped with the lens array optical system according to the present invention.

[0139] The color image forming apparatus 33 is a tandem-type color image forming apparatus in which four optical apparatuses are arranged so as to respectively record image information in parallel on the surface of photosensitive drums that each serve as an image bearing body. The color image forming apparatus 33 includes optical apparatuses 17, 18, 19, and 20 that are equipped with the lens array optical system of the present invention, photosensitive drums 21, 22, 23, and 24 as image bearing bodies, developing devices 25, 26, 27, and 28, and a conveying belt 34.

[0140] The color image forming apparatus 33 receives red (R) , green (G) , and blue (B) color signals that are input from an external apparatus 35 such as a personal computer. These color signals are converted to cyan (C) , magenta (M) , yellow (Y) , and black (K). image data (dot data) by a printer controller 36 provided inside the apparatus. The cyan, magenta, yellow, and black image data are respectively input to the corresponding optical apparatus among the optical apparatuses 17, 18, 19, and 20. The aforementioned optical apparatuses emit exposure light 29, 30, 31, and 32 that has been modulated in accordance with the corresponding image data. Photosensitive surfaces of the photosensitive drums 21, 22, 23, and 24 are exposed by the

corresponding exposure light.

[0141] The exposure lights are modulated based on the image data, and the corresponding exposure lights are

irradiated onto the surfaces of the photosensitive drums 21, 22, 23, and 24 that were electrostatically charged by an unshown charging apparatus, to thereby form electrostatic latent images thereon. The thus- formed electrostatic latent images are developed as toner images by the developing devices 25, 26, 27, and 28 which are arranged so as to come in contact with the corresponding photosensitive drums at a position that is further on the downstream side in the rotational direction of the photosensitive drums than the position irradiated with the exposure light.

[0142] The toner images developed by the developing devices are transferred in sequence onto a sheet 39 that serves as a transfer material. Although the sheet 39 is contained in a sheet cassette 38 disposed in front of (on the right side in Fig. 12B) the photosensitive drums, it is also possible to feed the sheet 39

manually.

[0143] The sheet 39 onto which the unfixed toner images have been transferred as described above is further conveyed to a fixing device 37 which is disposed on the rear side (on the left side in Fig. 12B) of the

photosensitive drums 21, 22, 23 and 24. The fixing device 37 includes a fixing roller which includes therein a fixing heater (not shown) , and a pressure roller that is arranged so as to be in pressure contact with the fixing roller. The sheet 39 that has been conveyed is heated while being pressurized at a

pressure contact portion between the fixing roller and the pressure roller, to thereby fix the unfixed toner images onto the sheet 39. The sheet 39 on which the toner images were fixed is then discharged to outside of the image forming apparatus 33.

[0144] For example, a color image reading apparatus equipped with a CCD sensor may be used as the external apparatus 35. In such case, a color digital copier is formed by the color image reading apparatus and the color image forming apparatus 33. Further, the lens array optical system according to the present invention may be used in the color image reading apparatus.

[0145] Fig. 13 illustrates a schematic sectional view of an image reading apparatus 50 equipped with the lens array optical system according to the present invention.

[0146] The image reading apparatus 50 includes an image

reading portion 41, a frame 42, and a platen 43. The platen 43 is formed of a transparent member, and is supported by the frame 42. An original 40 is disposed on the upper face of the platen 43.

The image reading portion 41 reads image data of the original 40 by moving in the arrow directions in the drawing. The image reading portion 41 includes an illuminating unit that illuminates the original 40 through the platen 43, an imaging unit that images a light flux that was reflected from the original 40, and a sensor unit (light-receiving portion) which receives the imaged light flux and converts the imaged light flux into image data.

[0147] By using the lens array optical system according to the present invention, the imaging unit can be made compact and as a result an effect such that the overall image forming apparatus can also be made compact can be obtained.

[0148] The lens array optical system according to the present invention has a configuration in which a light

scattering portion is provided between a lens surface and an adjacent lens of a lens array. However, it is not necessary to limit the configuration according to the present invention to a light scattering portion, and the advantageous effects of the present invention can be obtained even when a light absorbing portion is provided instead of a light scattering portion.

[0149] A light blocking member in the lens array optical

system according to the present invention has been described as an integrally formed member having a plurality of openings that penetrate in the optical axis direction that correspond to the number of lenses included in the lens array, and in which a light blocking wall between adjacent openings is positioned between the optical axes of adjacent lenses, and which is disposed so as to be aligned with a light scattering portion. However it is not necessary to limit the light blocking member to this kind of integrally formed member, and for example, the light blocking member may be configured as a light blocking member unit that is obtained by adopting a configuration in which a frame member holds a plurality of plate-shaped members which can block ghost light so as to define the positions in the main array direction and sub-array direction of the plurality of plate-shaped members.

[0150] The lens array optical system according to the present invention is configured so as to have an entire length of an A4 width (width of 210 mm) . However, it is not necessary to limit the entire length of the lens array optical system to the A4 width, and the lens array optical system may be configured. to have an entire length of an arbitrary width.

[0151] The lens array optical system according to the present invention has the configuration of the present

invention across the entire length of the A4 width. However, it is not necessary to have the configuration of the present invention across the entire length of the lens array optical system, and the advantageous effects of the present invention can be obtained even in a case where only a part of the lens array optical system has the configuration of the present invention. For example, in the lens array optical system according to the first embodiment, components are positioned at the center portion thereof with respect to the main array direction. Accordingly, even if the ambient temperature fluctuates, a relative positional deviation between the lens arrays and the light blocking member in the vicinity of the center portion is small.

Therefore, as long as at least lenses in the vicinity of both end portions of the lens array optical system have the configuration of the present invention, the advantageous effects of the present invention can be obtained.

[0152] In the lens array optical system according to the present invention, there is a difference in the linear expansion coefficients between the respective lens arrays and the light blocking member. However, the linear expansion coefficients of both may be the same. In a case where the linear expansion coefficients of both are the same, although a relative positional deviation does not arise between the lens array and the light blocking member when the ambient temperature fluctuates, a relative positional deviation between the lens array and the light blocking member that is caused by an arrangement error when assembling is always present. Therefore, the present invention has an effect even in a case where the linear expansion coefficients of a lens array and a light blocking member are the same.

[0153] While the present invention has been described with reference to exemplary embodiments, it is to be

understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest

interpretation so as to encompass all such

modifications and equivalent structures and functions.

[0154] This application claims the benefit of Japanese Patent Application No. 2013-235569, filed November 14, 2013 and Japanese Patent Application No. 2014-108094, filed May 26, 2014 which are hereby incorporated by reference herein in their entirety.

Reference Signs List

[0155] 102 Lens array optical system (imaging optical system)

107 First lens array

108 Light blocking member

109 Second lens array

110 Light scattering portion (ghost. light suppressing portion)

Claims

[Claim l]An imaging optical system comprising:

a first lens array that includes a plurality of lenses arrayed in a first direction, and that forms an intermediate image of an object in a first section that is parallel to the first direction;

a second lens array that includes a plurality of lenses arrayed in the first direction, and that re- images the intermediate image of the object in the first section; and

a light blocking member that is disposed between optical axes of adjacent lenses of the first and second lens arrays;

wherein:

at least one of the first and second lens arrays has a ghost light suppressing portion between adjacent lens surfaces; and

a width in the first direction of the ghost light suppressing portion is greater than a width in the first direction of the light blocking member. [Claim 2] An imaging optical system, comprising:

a first lens array that includes a plurality of lenses arrayed in a first direction and in a second direction that is perpendicular to the first direction, and that forms an intermediate image of an object in a first section that is parallel to the first direction;

a second lens array that includes a plurality of lenses arrayed in the first and second directions, and that re-images the intermediate image of the object in the first section; and

wherein :

a width in the second direction of the ghost light suppressing portion is greater than a width in the second direction of the light blocking member.

[Claim 3] he imaging optical system according to claim 1,

wherein :

each of the first and second lens arrays include a plurality of lenses arrayed in the first direction and in a second direction that is perpendicular to the first direction; and

a width in the second direction of the ghost light suppressing portion is greater than a width in the second direction of the light blocking member. [Claim ] The imaging optical system according to any one of claims 1 to 3, wherein a condition given by: AL x AT x ΛΧ < AW/2

is satisfied, where AL (mm) is a distance to a portion of the imaging optical system at a furthest distance from a portion at which the imaging optical system is positioned in the first direction, ΔΤ (°C) is a difference between a temperature at a time that the imaging optical system is positioned and a temperature at a time that the imaging optical system is used, ΔΧ (/°C) is a larger value among an absolute value of a difference between a linear expansion coefficient of the first lens array and a linear expansion

coefficient of a member that positions the light blocking member and an absolute value of a difference between a linear expansion coefficient of the second lens array and the linear expansion coefficient of the member that positions the light blocking member, and AW (mm) is a difference between a width of the ghost light suppressing portion and a width of the light blocking member in the first direction.

[Claim 5] The imaging optical system according to claim 4, wherein, the light blocking member is disposed between the first lens array and the second lens array, and a condition given by:

Bm + Tm > P x (1 - (Ls/Lmax) )

is satisfied, where Bm (mm) is a width in the first direction of the ghost light suppressing portion, Tm . (mm) is a width in the first direction of the light blocking member, P (mm) is an array period of the first and second lens arrays, Ls (mm) is a length of the light blocking member in the optical axis direction, and Lmax (mm) is a longest distance in the optical axis direction between facing lens surfaces of the first lens array and the second lens array. [Claim 6] The imaging optical system according to claim 5,

wherein the length of the light blocking member in the optical axis direction is less than a shortest distance in the optical axis direction between facing lens surfaces of the first lens array and the second lens array.

[Claim 7 ] The imaging optical system according to any one of claims 4 to 6, wherein a condition given by: 105 mm x 30°C x AX < AW/2

is satisfied.

[Claim 8 ] The imaging optical system according to any one of claims 1 to 7, wherein the light blocking member is disposed at least at one of a position that is further on an object side than the first lens array and a position that is further on an image side than the second lens array.

[Claim 9] The imaging optical system according to any one of claims 1 to 8, wherein the ghost light suppressing portion is a light scattering portion that scatters light.

[Claim 10] The imaging optical system according to claim 9,

wherein the light scattering portion includes a plurality of prisms. [Claim 11] The imaging optical system according to claim 10, wherein a condition given by:

Tm > Be

is satisfied, where Be (mm) is a distance between ridge lines of prisms at both ends of the light scattering portion.

[Claim 12] The imaging optical system according to any one of claims 1 to 8, wherein the ghost light suppressing portion is a light absorbing portion that absorbs light.

[Claim 13]An image forming apparatus, comprising:

an imaging optical system according to any one of claims 1 to 12;

a developing device that develops, as a toner image, an electrostatic latent image that is formed on a photosensitive surface of a photosensitive body by the imaging optical system;

a transfer device that transfers the developed toner image to a transfer material; and

a fixing device that fixes the transferred toner image to the transfer material.

[Claim 14] An image reading apparatus, comprising:

an imaging optical system according to any one of claims 1 to 12; and

a light-receiving portion that receives light from an original that is converged by the imaging optical system.