JP2017107120A - Lens array optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens array optical system capable of blocking a ghost luminous flux in a sub-arrangement direction.SOLUTION: A lens array optical system 102 is a lens array optical system 102 including a first lens array G1 and a second lens array G2 which are configured by arranging a plurality of lens arrays including a plurality of lenses arranged in a main arrangement direction, in the sub-arrangement direction and a light blocking member which is arranged between the first lens array G1 and the second lens array G2. The lens array optical system 102 forms the erect image of an object in a main arrangement cross section and forms the inverted image of the object in a sub-arrangement cross section. The light blocking member includes an intermediate plate 1083 which is arranged between the adjacent lens arrays of the first lens array G1 in the sub-arrangement direction. The intermediate plate includes a scattering surface 1083b parallel with the main arrangement cross section.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a lens array optical system, and more particularly to a lens array optical system suitable for use in an image forming apparatus or an image reading apparatus.

In recent years, an exposure apparatus and a reading apparatus using a lens array optical system including a lens array configured by arranging a plurality of small-diameter lenses have been used.
The lens array optical system can reduce the number of components and the number of components, which is advantageous for downsizing and cost reduction.

  Patent Document 1 includes a first lens array and a second lens array in which a lens array formed by a plurality of lenses arranged in the main arrangement direction is arranged in a staggered arrangement in the sub arrangement direction. A lens array optical system for forming an inverted image of an object is disclosed. In the lens array optical system disclosed in Patent Document 1, an unnecessary ghost light beam is shielded by providing a light shielding member having a light shielding aperture arranged in the main arrangement direction so as to follow a staggered arrangement. .

  In Patent Document 1, a case is considered where a point light source having a plurality of light emitting points exists on the optical axis of a lens array optical system. Therefore, the light shielding member of Patent Document 1 is emitted from the light source, passes through the predetermined lens array of the first lens array, and then is arranged at the same position in the sub-array direction as the predetermined lens array of the second lens array. The object is to shield only the ghost beam incident on the lens array.

JP 2012-247565 A

However, if the light source is arranged in the sub-array direction from the optical axis of the lens array optical system due to an assembly error or the like in the exposure device or the reading device, the following ghost light beam is generated and a good image is obtained. Can no longer be obtained. That is, a ghost that is emitted from a light source, passes through a predetermined lens array of the first lens array, and then enters a lens array that is arranged at a position different from the predetermined lens array of the second lens array in the sub-array direction. A light beam (sub-array direction ghost light beam) is generated. Patent Document 1 does not disclose anything about shielding the sub-array direction ghost beam.
Therefore, an object of the present invention is to provide a lens array optical system capable of shielding such a sub-array direction ghost beam.

  In the lens array optical system according to one aspect of the present invention, a plurality of lens arrays including a plurality of lenses arranged in a first direction are arranged in a second direction perpendicular to the first direction and the optical axis direction. A first lens array configured in such a manner that a lens array including a plurality of lenses arranged in a first direction is arranged in a second direction; A lens array optical system comprising: a light shielding member disposed between the lens array and the second lens array, wherein the lens array optical system is configured such that an object in the first cross section perpendicular to the second direction An upright image is formed and an inverted image of the object is formed in the second cross section perpendicular to the first direction, and the light shielding member is arranged in the second direction in the adjacent lens array of the first lens array. Having an intermediate plate disposed between them, the intermediate plate being the first Characterized in that it comprises a parallel scattering plane cross section.

  According to the present invention, it is possible to provide a lens array optical system capable of shielding a sub-array direction ghost beam.

1 is a cross-sectional view, a cross-sectional projection view, and a perspective view of an optical device and a lens array optical system according to a first embodiment. The perspective view of the light-shielding member which concerns on 1st embodiment. The main array sectional view and subarray sectional view of a part of the lens array optical system concerning a first embodiment. The figure explaining the optical path in the subarray cross section in the optical apparatus which concerns on 1st embodiment. The figure explaining the optical path in the main array section in the optical device concerning a first embodiment. The figure explaining the optical path in the subarray cross section in the optical apparatus which concerns on 1st embodiment. The schematic diagram which shows the scattering effect of a wrinkle scattering surface. The figure which showed the light quantity ratio of the sub-array direction ghost light beam with respect to the desired image formation light beam in a photosensitive part. The figure explaining the optical path in the subarray cross section in the optical apparatus which concerns on 1st embodiment. FIG. 3 is a sub-scan sectional view of the image forming apparatus on which the lens array optical system according to the first embodiment is mounted. 1 is a schematic cross-sectional view of an image reading apparatus equipped with a lens array optical system according to a first embodiment.

  A lens array optical system according to an embodiment of the present invention will be described below with reference to the drawings. It should be noted that the drawings shown below may be drawn at a scale different from the actual scale so that the present invention can be easily understood.

[First embodiment]
FIGS. 1A, 1B, and 1C respectively show an XY sectional projection view, an XZ sectional view, and a YZ sectional view of the optical device 100 according to the first embodiment.
FIG. 1D is a perspective view of the lens array optical system 102 of the optical device 100 according to the first embodiment.

  The optical device 100 includes a light source 101, a lens array optical system 102, and a photosensitive unit 103. The lens array optical system 102 includes a first lens array 107, a light shielding member 108, and a second lens array 109.

  The light source 101 includes a plurality of light emitting points arranged at equal intervals along a Y direction (hereinafter, referred to as a main array direction) in which a plurality of lenses constituting the first lens array 107 are mainly arranged. ing. In this embodiment, an LED is used as each light emitting point of the light source 101.

The first and second lens arrays 107 and 109 are configured by arranging a plurality of lenses in the main arrangement direction (first direction) (a lens array is formed). The first and second lens arrays 107 and 109 are in the X direction (hereinafter referred to as the optical axis direction) and the Z direction (hereinafter referred to as the sub-array direction) perpendicular to the main array direction (Y direction). Is configured so that the lenses are arranged in a two-row staggered arrangement.
Here, in the first and second lens arrays 107 and 109, in the sub-array direction (second direction), the lens row on the positive side from the optical axis is the upper row, and the lens row on the negative side is the lower row. It is defined as
The arrangement pitch p in the main arrangement direction of the first and second lens arrays 107 and 109 is 0.76 mm for both the upper and lower lens rows.
The staggered arrangement means an arrangement in which one of the upper and lower lens arrays is shifted from the other in the main arrangement direction by ½ of the arrangement pitch p.
In FIG. 1C, black circles and black triangles in the figure respectively indicate the optical axis of each lens in the upper row and the optical axis of each lens in the lower row.
Here, the shortest distance ΔY between the optical axis of the lens in the upper row and the optical axis of the lens in the lower row is the most in the lens when the optical axis of the lens in the lower row is used as a reference in the main arrangement direction. This is the distance to the optical axis of the adjacent upper row lens.
That is, the upper and lower lens arrays are arranged in a staggered manner by shifting the upper lens array and the lower lens array from each other by ΔY in the main array direction, thereby separating the respective optical axes by ΔY in the main array direction.
In the present embodiment, since the shortest distance ΔY is half the arrangement pitch p in the main arrangement direction of the first and second lens arrays 107 and 109, ΔY = p / 2 (= 0.38 mm).
Since the first and second lens arrays 107 and 109 are arranged in a staggered manner as in this embodiment, the period of the imaging performance viewed in the main array direction of the lenses is half of the array pitch p. As a result, the unevenness in the amount of imaged light is less noticeable.

  The lens array optical system 102 forms an erecting equal-magnification image in the main array section and an inverted image in the sub-array section.

  For example, in the image forming apparatus, the photosensitive unit 103 is a photosensitive drum.

The interval between the light emitting points of the light source 101 is several tens of μm, and at least several hundreds of μm is sufficiently smaller than the arrangement pitch p in the main arrangement direction of the first and second lens arrays 107 and 109. It can be considered that they are arranged almost continuously.
Therefore, since the lens array optical system 102 forms an erecting equal-magnification image within the main array section, as shown in FIG. 1D, the light beam emitted from one light emitting point in the light source 101 is the main array. Even through a plurality of lenses arranged in the direction, the light is condensed at one point on the photosensitive portion 103. For example, in FIG. 1A, the light beam emitted from the light emission point P1 is collected on P1 ′, and the light beam emitted from the light emission point P2 is collected on P2 ′. This characteristic enables exposure corresponding to light emission of the light source.

  FIG. 2 is a perspective view of the light shielding member 108 of the optical device 100 according to the present embodiment.

The light shielding member 108 is disposed between the optical axes of the adjacent lenses in the upper lens row and the optical axes of the adjacent lenses in the lower lens row. A second light shielding wall 1082 is provided.
The plurality of first light shielding walls 1081 and the plurality of second light shielding walls 1082 are respectively coupled to an intermediate plate 1083 extending in the main array direction. The middle plate 1083 is disposed between adjacent lens rows of the first lens array 107 in the sub-array direction.

  The first lens array 107 includes a plurality of first lenses (hereinafter referred to as G1) 1071a, 1071b,... In the upper row, and a plurality of first lenses (hereinafter referred to as G1) in the lower row. 1072a, 1072b,... Are arranged. Similarly, the second lens array 109 includes a plurality of second lenses (hereinafter also referred to as G2) 1091a, 1091b,... In the upper row, and a plurality of second lenses (hereinafter referred to as G2) in the lower row. 1092a, 1092b,... May be arranged. The individual lenses constituting each of the first lens array 107 and the second lens array 109 constitute a pair, and the optical axes of the lenses constituting the pair are configured to coincide with each other.

FIG. 3A is a schematic cross section of the main array section (first section) and the sub array section (second section) of a part 1021a of the lens array optical system 102 of the optical device 100 according to the present embodiment. The figure is shown.
FIG. 3B is a schematic cross-sectional view of the main array section and the sub-array section of a part 1022a of the lens array optical system 102 of the optical device 100 according to the present embodiment.

  A part 1021a of the lens array optical system includes a first lens 1071a, a part of the light shielding member 108, and a second lens 1091a which are arranged so as to be aligned with each other. The part 1022a of the lens array optical system includes a first lens 1072a, a part of the light shielding member 108, and a second lens 1092a, which are arranged so as to be aligned with each other. The cross sections perpendicular to the optical axes of the first lens and the second lens are rectangular.

Within the cross section of the main array, the light beam emitted from one light emitting point of the light source 101 forms an image once on the intermediate image plane 105 after passing through G1. Thereafter, the light passes through G2 and forms an erecting equal-magnification image on the photosensitive portion 103 (forms an erecting equal-magnification image (erecting image) of the object).
The object plane (here, the light source 101) to the intermediate image plane 105 is referred to as a first optical system, and the area from the intermediate image plane 105 to the image plane (here, the photosensitive portion 103) is referred to as a second optical system. .
The first lens array forms an intermediate image of the object in the main array section, and the second lens array re-images the intermediate image of the object in the main array section.
In the sub-array section, the light beam emitted from the light source 101 passes through G1, and then passes through G2 without being imaged on the intermediate imaging surface 105, and forms an inverted image on the photosensitive portion 103 (inverted object). Form an image).
As can be seen from FIG. 3, by adopting an inverted imaging system for the sub-array section, it is possible to increase the light capture angle in the sub-array direction while maintaining the imaging performance. And imaging performance can be achieved.
Note that the imaging magnification in the main array direction of the first optical system is an intermediate imaging magnification β. Note that the intermediate imaging magnification β of the first optical system of the optical apparatus 100 according to the present embodiment is set to −0.45.

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

Here, the intersection of each lens surface and the optical axis is the origin, and the optical axis direction is the X axis. In addition, the main arrangement direction is a Y axis and the sub arrangement direction is a Z axis. In Table 1, “E-x” means “× 10 ^−x ”.

The G1R1 surface and the G1R2 surface respectively refer to the surface on the light source 101 side and the surface on the light shielding member 108 side of G1, and the G2R1 surface and the G2R2 surface respectively refer to the surface on the G2 light shielding member 108 side and the photosensitive portion 103 side. Points to the side.
The G1R1, G1R2, G2R1 and G2R2 surfaces are each composed of an anamorphic surface having different powers in the main array cross section and the sub array cross section, and the aspheric shape thereof is represented by the following aspheric formula (1). Represented.

Here, X, Y, and Z are the coordinates in the optical axis direction, the main array direction, and the sub array direction, respectively, and C _{i, j} (i, j = 0, 1, 2,...) Are aspheric coefficients.

  When a plurality of light sources with a plurality of light emitting points arranged in the main arrangement direction are arranged in the sub arrangement direction, or when an arrangement error or the like occurs in the light source, the light sources are arranged in the sub array from the optical axis of the lens array optical system. There is a case where it is arranged at a position shifted in the direction.

  For example, consider the case where the light sources are arranged in the + Z direction.

4A and 4B show a case where the light source 101 is arranged on the optical axis of the lens array optical system 102 and a case where the light source 101 is shifted from the optical axis of the lens array optical system 102 by + Z in the sub-array direction. The figure explaining the optical path in a subarray section in the case of arrangement is shown.
Here, G1 and G2 are indicated by arrows as being ideal lenses, and the optical axis of the lens array optical system 102 is indicated by a chain line.

As shown in FIG. 4A, when the light source 101 is disposed on the optical axis of the lens array optical system 102, the total luminous flux travels between G1 and G2 parallel to the optical axis. As a result, the image forming light beam K forms a desired image on the photosensitive portion 103.
On the other hand, as shown in FIG. 4 (b), when the light source 101 is arranged to be shifted by + Z from the optical axis of the lens array optical system 102 in the sub-array direction, the luminous fluxes are G1 and G2. It advances at a predetermined angle with respect to the optical axis in the sub array direction. Therefore, the light beam that has passed through the vicinity of the optical axis among the G1 light beams in the upper row is incident on G2 in the lower row across the optical axis while traveling between G1 and G2. However, in the present embodiment, the lens arrays are in a staggered arrangement, and the optical axis of the upper row G1 and the optical axis of the lower row G2 do not coincide with each other in the main arrangement direction. Therefore, the light beam that has passed near the optical axis among the G1 light beams in the upper row is not the imaging light beam K that forms a desired image on the photosensitive portion 103, but becomes the ghost light beam G.
In FIG. 4, the imaging light beam K and the ghost light beam G are indicated by a thin solid line and a thick solid line, respectively.
Hereinafter, such a ghost beam G is referred to as a sub-array direction ghost beam G.

  As shown in FIG. 4, the ghost beam G in the sub-array direction receives substantially the same condensing power as the desired image beam K in the sub-array direction. It is condensed at a very close position.

  FIGS. 5A and 5B respectively show the imaging light flux K and the sub-array direction ghost in the main array section when the light source 101 is displaced from the optical axis of the lens array optical system 102 in the sub-array direction. The figure explaining the optical path of each light beam G is shown.

As shown in FIG. 5A, the imaging light beam K passes through the upper row G2 when passing through the upper row G1, and passes through the lower row G2 when passing through the lower row G1. pass. For this reason, since the optical axes of G1 and G2 substantially coincide with each other in the main arrangement direction, desired image formation is achieved on the photosensitive portion 103 in the main arrangement direction as shown in FIG. 5B. Is done.
On the other hand, as shown in FIG. 5B, in the sub-array direction ghost light beam G, as described above, the light beam that has passed near the optical axis in the G1 light beam in the upper row is G1. In the course of traveling between G2 and G2, it passes the optical axis and enters G2 in the lower row. At this time, the optical axis of G1 in the upper row and the optical axis of G2 in the lower row do not coincide with each other in the main arrangement direction, so that desired image formation is not achieved on the photosensitive portion 103. As a result, these light beams, that is, the sub-array direction ghost light beam G becomes unnecessary light, which causes image quality deterioration.

  In an inverted imaging system having a plurality of lens rows in the sub-array direction as in this embodiment, it is important to reduce the ghost beam G in the sub-array direction. Note that the apparatus disclosed in Patent Document 1 is premised on a lens array optical system in which a point light source exists on the optical axis, so that the problem of a ghost beam in the sub-array direction does not occur.

Therefore, in the lens array optical system 102 according to the present embodiment, an intermediate plate 1083 is provided on the light shielding member 108.
Thereby, the sub-array direction ghost light beam G exceeding the optical axis can be shielded or scattered during the travel between G1 and G2, and the influence of the sub-array direction ghost light beam G in the photosensitive portion 103 can be reduced.

  FIGS. 6A and 6B are diagrams illustrating optical paths in the sub-array cross section when the light source 101 is disposed by + Z deviation from the optical axis of the lens array optical system 102 in the sub-array direction. ing.

As shown in FIG. 6, the middle plate 1083 of the light shielding member 108 has a light shielding end face 1083a and a light shielding bottom face 1083b.
The light shielding end face 1083a receives the ghost beam G in the sub-array direction relative to it, and shields or scatters it as a light beam having a small incident angle.
The light-shielding bottom surface 1083b receives the ghost beam G in the sub-array direction that could not be shielded by the light-shielding end surface 1083a substantially in parallel, and shields or scatters it as a light beam having a large incident angle.

In the case shown in FIG. 6A, since the light shielding (absorption) performance or scattering performance of the light shielding end face 1083a and the light shielding bottom face 1083b is sufficient, the sub-array direction ghost light beam G is converted into the light shielding end face 1083a and the light shielding bottom face 1083b. Is shielded from light.
On the other hand, as shown in FIG. 6B, if the light shielding (absorbing) performance or scattering performance of the light shielding end face 1083a and the light shielding bottom face 1083b is not sufficient, the sub-array direction by the light shielding end face 1083a and the light shielding bottom face 1083b. There is a possibility that reflected light of the ghost beam G is generated. The reflected light of the sub-array direction ghost light beam G by the light shielding end surface 1083a does not go to the photosensitive portion 103, so there is no problem. However, the reflected light of the sub-array direction ghost light beam G by the light shielding bottom surface 1083b goes to the photosensitive portion 103. It becomes.

In practice, since the deviation amount Z is small, the reflected light of the ghost beam G in the sub-array direction from the light-shielding bottom surface 1083 b reaches a position very close to the desired imaging beam K on the photosensitive portion 103.
Further, from the viewpoint of the light shielding material actually used for manufacturing the light shielding member 108, the incident angle of the ghost light beam G in the sub-array direction on the light shielding bottom surface 1083b is large. It is difficult to suppress the generation of reflected light.

Therefore, in the present embodiment, the light shielding performance or scattering performance is improved by making the light shielding bottom surface 1083b of the middle plate 1083 of the light shielding member 108 a wrinkle scattering surface provided with wrinkles (wrinkle pattern) by wrinkle processing. That is, in the present embodiment, the light shielding bottom surface 1083b of the middle plate 1083 of the light shielding member 108 is a scattering surface parallel to the main array section. Here, the light shielding bottom surface 1083b is not limited to being parallel to the main array section, and may be substantially parallel.
As a result, even in the case where the reflected light that cannot be absorbed by the light-shielding bottom surface 1083b is generated in the sub-array direction ghost light beam G, the reflected light is dispersed as it travels toward the photosensitive portion 103, whereby the sub-array direction ghost light beam G Deterioration of image performance can be prevented.

  FIG. 7 is a schematic diagram showing the scattering effect of the grain scattering surface.

In general, when the incident angle of the light beam incident on the grain scattering surface is θ _in and the scattering angle of the light beam scattered by the grain scattering surface is α, the intensity distribution of the light beam scattered in the direction of the scattering angle α is approximately ,
I∝ (cos (| α−θ _in |)) ^N (where −θ _in ≦ α ≦ 90 °) (2)
It can be expressed as.
In addition, the value of N changes depending on the average depth of the texture on the textured scattering surface, thereby varying the scattering effect. In general, the deeper the average depth of the grain, the smaller N and the greater the scattering effect.

  Here, the effect of the lens array optical system 102 of the optical device 100 according to the present embodiment will be described using specific values.

First, consider a case where the light source is displaced by +0.1 mm in the sub-array direction with respect to the optical axis of the lens array optical system 102 due to an arrangement error.
In this case, the ghost beam G in the sub-array direction takes an optical path as shown in FIG.

FIG. 8 shows the light amount ratio of the ghost beam G in the sub-array direction to the desired imaged beam K in the photosensitive unit 103, which is obtained by simulation based on the formula (2).
Here, the amount of light of the desired imaging light beam K is set to 1 (100%), and the sub-array direction ghost light beam G is a plane on which the shading bottom surface 1083b is not textured, N = 1000000, N = 10000, and N = 100. The case of each wrinkle scattering surface is shown.
The light amounts of the imaging light beam K and the sub-array direction ghost light beam G are indicated by LSF (Line Spread Function) obtained by integrating the light amount in the photosensitive portion 103 in the main array direction for each position in the sub-array direction.
Furthermore, in practice, because the value of N varies according to the incident angle theta _in, the range of incident angle theta _in the sub-array direction ghost light beam G that are considered in this embodiment is narrower, with N constant There is no problem even if simulation is performed.

As shown in FIG. 8, in this embodiment, the sub-array section is an inverted unit magnification system (magnification in the sub-array direction is −1), and the light source is +0.1 mm in the sub-array direction (Z direction). Since it is displaced, the imaging light beam K reaches the position of Z = −0.1 mm of the photosensitive portion 103.
On the other hand, in the present embodiment, G1 and G2 are symmetrical lens optical systems. Therefore, when the sub-array direction ghost light beam G is regularly reflected by the light-shielding bottom surface 1083b that is a non-textured plane, The position reaches Z = + 0.1 mm.
At that time, the peak light amount ratio of the ghost beam G in the sub-array direction to the imaging beam K in the photosensitive unit 103 is about 2.55%, which leads to deterioration in image quality.
On the other hand, when the light-shielding bottom surface 1083b is a grained scattering surface, the peak light quantity ratio is about 0.55% when N = 1000000, about 0.18% when N = 10000, and about 0 when N = 100. It can be seen that the deterioration of image quality can be reduced.
In the present embodiment, since the average depth of the grain on the light shielding bottom surface 1083b is 12 μm, it is substantially equal to the approximate scattering distribution of N = 100.

  From the above, in the lens array optical system according to the present embodiment, which achieves both good imaging light quantity and imaging performance, and reduction of the unevenness thereof, the light source is arranged shifted from the optical axis in the sub-array direction. Even in such a case, the effect of reducing the influence of ghost light can be obtained.

  Next, further effects of the lens array optical system 102 of the optical device 100 according to the present embodiment will be described.

  FIGS. 9A and 9B are diagrams illustrating optical paths in the sub-array cross section when the light source 101 is disposed by + Z in the sub-array direction from the optical axis of the lens array optical system 102. FIG. ing.

If an arrangement error does not occur and the light source 101 is not displaced from the optical axis of the lens array optical system 102 in the sub-array direction, the intermediate plate 1083 of the light shielding member 108 may cause a desired imaging light beam K to be absorbed. As a result, the amount of imaged light is reduced.
Therefore, from the viewpoint of the amount of imaged light of the desired imaged light flux K, it is preferable that the thickness D in the sub-array direction of the middle plate 1083 of the light shielding member 108 is thinner.
According to the present embodiment, since the ghost beam G in the sub-array direction can be sufficiently shielded by the light shielding bottom surface 1083b of the middle plate 1083 of the light shielding member 108, in principle, the thickness D is reduced to infinity. It doesn't matter.

Here, conversely, a case is considered in which the sub-array direction ghost light beam G is shielded only by the light shielding end face 1083a of the middle plate 1083 of the light shielding member 108.
That is, as shown in FIG. 9B, a case is considered where the width in the optical axis direction of the middle plate 1083 of the light shielding member 108 is small infinitely small.
The optical paths of the imaging light beam K and the sub-array direction ghost light beam G in this case are shown in FIG.

When a plurality of line-arranged light sources are used for brightness and ease of assembly is taken into consideration, it is preferable that the allowable amount of shift (shift) from the optical axis in the sub-array direction of the light sources 101 is larger.
However, since the light source 101 is arranged shifted from the optical axis in the sub-array direction, the light beam emitted from the light source 101 enters G1 and G2 with an angle.
Here, if the angle formed by the light beam incident on the light shielding member 108 disposed between G1 and G2 with respect to the optical axis with respect to the sub-array direction is θ, aberrations are difficult to remove and imaging performance deteriorates. From the viewpoint, the range in which the angle θ is allowed is normally θ ≦ 10 °.

Therefore, the minimum thickness D _{edge in} the sub-array direction of the middle plate 1083 of the light shielding member 108, which is necessary when the ghost beam G in the sub-array direction is shielded only by the light shielding end surface 1083a, is the surface distance between G1 and G2 is Δ. Then, D _edge = Δtan 10 ° = 0.18Δ.

Therefore, in the present embodiment, the middle plate 1083 of the light shielding member 108 has a light shielding bottom surface 1083b in addition to the light shielding end surface 1083a. Therefore, the thickness D in the sub-array direction of the middle plate 1083 of the light shielding member 108 is It can be seen that even a large D _edge is sufficient.

Therefore, the following equation (3)
D ≦ D _edge = 0.18Δ (3)
By satisfying the following conditions, it can be said that the lens array optical system 102 of the optical device 100 according to the present embodiment can obtain the effects of the present invention from the viewpoint of the amount of imaged light.

  In this embodiment, D = 0.2 mm and Δ = 2.162 mm, and when these values are substituted into Equation (3), D = 0.2 mm <0.18 × 2.162 mm = 0.389 mm It becomes. Therefore, the lens array optical system 102 of the optical device 100 according to the present embodiment satisfies the formula (3), and the effects of the present invention can be obtained.

Next, assuming that the effective diameter in the sub-array direction of the lens array optical system 102 is Rs, the amount of decrease in the imaging light amount at the light emitting point on the optical axis by the middle plate 1083 of the light shielding member 108 is approximately D / Rs. Here, the effective diameter is a diameter of an effective surface through which an effective light beam contributing to image formation passes among the lens surfaces.
In the present embodiment, the intermediate plate 1083 is provided in the light shielding member 108 in order to shield the sub-array direction ghost light beam G. However, due to this, the imaging light amount at the light emitting point on the optical axis is insufficient. Image deterioration occurs.
Therefore, it is important to optimally design the lens array optical system 102 of the optical device 100 according to the present embodiment in consideration of the balance between shielding the ghost beam G in the sub-array direction and reducing the amount of imaged light. It is.
In general, it can be said that if the reduction in the amount of imaged light exceeds 10%, it is not preferable as the performance of the lens array optical system.
Therefore, in this embodiment, the following formula (4)
D / Rs ≦ 0.1 (4)
It is preferable to satisfy the following condition.
If the expression (4) is not satisfied, the amount of imaged light is greatly reduced, and the lens array optical system is not designed with good balance, and the effects of the present invention cannot be obtained.

In this embodiment, D = 0.2 mm and Rs = 2.44 mm. If these values are substituted into the equation (4), D / Rs = 0.2 mm / 2.44 mm = 0.082 <0. .10.
Therefore, it can be said that the lens array optical system 102 of the optical device 100 according to the present embodiment is designed with a sufficient consideration of the balance between shielding the ghost beam G in the sub-array direction and reducing the imaging light amount. .

  Next, the imaging light amount reduction amount in the prior art is compared with the imaging light amount reduction amount in the present embodiment.

Specifically, the effect of using the lens array optical system 102 of the optical device 100 according to the present embodiment if the imaged light amount decrease amount in the present embodiment can be reduced by 5% or more with respect to the image formation light amount decrease amount in the prior art. It can be said that
In the prior art, it can be considered that the ghost light beam in the sub-array direction is shielded only by the light shielding end face of the middle plate of the light shielding member, so that the amount of reduction in the amount of imaging light of the desired imaging light beam is approximately D _edge / Rs = 0.18Δ / Rs.
On the other hand, in the present embodiment, the ghost light beam in the sub-array direction is shielded by the light shielding bottom surface in addition to the light shielding end surface of the middle plate of the light shielding member. And D / Rs.
Therefore, the following equation (5)
0.18Δ / Rs−D / Rs = (0.18Δ−D) /Rs≧0.05 (5)
If this condition is satisfied, it can be said that the effect of using the lens array optical system 102 of the optical device 100 according to the present embodiment can be obtained.

In the present embodiment, Δ = 2.162 mm, D = 0.2 mm, and Rs = 2.44 mm. When these values are substituted into the equation (5), (0.18 × 2.162-0. 2) /2.44=0.078≧0.05.
Therefore, it can be said that the effect of using the lens array optical system 102 of the optical device 100 according to the present embodiment is obtained.

In the present embodiment, the light shielding bottom surface 1083b of the middle plate 1083 of the light shielding member 108 is a textured scattering surface, and the average depth of the textured surface is 12 μm.
Therefore, as shown above, the intensity distribution of the light beam scattered by the light-shielding bottom surface 1083b, which is a grain scattering surface, is expressed by Equation (2) where N = 100. Therefore, the peak light amount ratio of the ghost light beam in the sub-array direction to the imaging light beam in the photosensitive portion is about 0.05%, and the deterioration of the image quality can be almost ignored.
In general, if the average depth of the grain is 8 μm or more and 30 μm or less, the intensity distribution of the light beam scattered by the grain scattering surface can be expressed by the equation (2) where N = 100.
Therefore, if the light-shielding bottom surface 1083b of the middle plate 1083 of the light-shielding member 108 is a textured scattering surface having such a textured average depth, it can be said that it is suitable for use in this embodiment.
If the average depth of the wrinkles is less than 8 μm, the scattering effect is reduced (that is, N becomes larger). On the other hand, if the average depth of the wrinkles is larger than 30 μm, the mold release at the time of molding the light shielding member 108 is performed. Becomes difficult.

  As described above, the aperture shape of the lens surface of each lens constituting the lens array optical system 102 of the optical device 100 according to this embodiment is rectangular. By making the aperture surfaces of the on-axis object high light fluxes of the first optical system and the second optical system rectangular, the lens surfaces can be arranged with no gap as much as possible, and the light utilization efficiency can be improved. In addition, the rectangular shape here is an approximate shape such as a shape in which at least one of the sides constituting the rectangle is curved, a shape in which each vertex is eliminated and a substantially circular shape or a substantially elliptical shape, etc. Includes a rectangular shape.

  In the present embodiment, in the first and second lens arrays 107 and 109 of the lens array optical system 102, two lens rows are arranged in the sub-array direction, but not limited to this, three or more lens rows are arranged. May be arranged. That is, in this embodiment, two or more lens rows may be arranged.

  In the present embodiment, the shape of the lens constituting the upper lens row of the first and second lens arrays 107 and 109 of the lens array optical system 102 and the shape of the lens constituting the lower lens row are the same. However, the present invention is not limited to this, and the shape of the lens constituting the upper lens row of the first lens array 107 and / or the second lens array 109 may be different from the shape of the lens constituting the lower lens row. I do not care.

  In the present embodiment, the optical axis of each lens constituting the lens array optical system 102 is on the connection between the upper lens row and the lower lens row of the first and second lens arrays 107 and 109 in the sub-array direction. . However, the present invention is not limited to this, and the optical axis of each lens constituting the lens array optical system 102 is other than the connecting portion between the upper and lower lens arrays of the first and second lens arrays 107 and 109 in the sub-array direction. You may be in the position.

  The intermediate imaging magnification β of the first optical system of the optical device 100 according to the present embodiment is set to −0.45. However, the intermediate imaging magnification β is equal to this value as long as erecting equal magnification imaging can be achieved. Not limited to.

  In the present embodiment, the lenses constituting the upper lens row and the lower lens row of the first and second lens arrays 107 and 109 of the lens array optical system 102 are the same lens in the optical axis direction and main array. It is obtained by cutting a main array section parallel to the direction. However, the present invention is not limited to this, and if the lenses constituting the upper and lower lens arrays of the first and second lens arrays 107 and 109 of the lens array optical system 102 are surfaces parallel to the optical axis, the main array It may be obtained by cutting a cross section other than the cross section.

  In the present embodiment, the lens surface shapes of the lenses of the first and second lens arrays 107 and 109 of the lens array optical system 102 are symmetric with respect to the optical axis. It may be an asymmetric shape.

  In the present embodiment, for at least one of the first and second lens arrays 107 and 109, when the distance in the main array direction between the optical axes of two adjacent lenses in the sub array direction is zero, the two The lens surface of the lens can be expressed by equation (1).

  In the present embodiment, the lens surface shape of the lenses constituting the first lens array 107 of the lens array optical system 102 and the lens surface shape of the lenses constituting the second lens array 109 are symmetrical to each other. However, the present invention is not limited to this, and the lens surface shape of the lenses constituting the first lens array 107 and the lens surface shape of the lenses constituting the second lens array 109 may not be symmetrical to each other.

  In the present embodiment, the arrangement pitch p in the main arrangement direction of the upper lens rows of the first and second lens arrays 107 and 109 of the lens array optical system 102 is the same as the arrangement pitch p in the main arrangement direction of the lower lens rows. is there. However, the arrangement pitch p is not limited to this, and the arrangement pitch p in the main arrangement direction of the upper lens row of the first lens array 107 and / or the second lens array 109 is different from the arrangement pitch p in the main arrangement direction of the lower lens row. It doesn't matter.

  In the present embodiment, the sub-array direction effective range of the lenses in the upper lens row of the lens arrays 107 and 109 and the sub-array direction effective range of the lenses in the lower lens row are parallel to the main array direction at any position in the sub-array direction. There is only one on the axis. However, the present invention is not limited to this, and both may be on an axis parallel to the main arrangement direction at any position in the sub arrangement direction.

  The lens array optical system 102 of the optical device 100 according to the present embodiment is designed to perform inverted equal magnification imaging within the sub-array cross section, but is not limited thereto, and performs non-equal magnification inverted imaging. It may be designed to.

  According to the lens array optical system 102 of the optical device 100 according to the present embodiment, even when the light source is deviated from the optical axis in the sub-array direction while reducing the unevenness of the imaging light quantity and the imaging performance. The effect of ghost light can be reduced.

[Monochrome image forming apparatus]
FIG. 10A is a cross-sectional view of the main part of the monochrome image forming apparatus 5 on which the lens array optical system according to the first embodiment is mounted.

  Code data Dc is input to the image forming apparatus 5 from an external device 15 such as a personal computer. The input code data Dc is converted into image data (dot data) Di by the printer controller 10. The converted image data Di is input to the exposure unit 1 including the light source and the lens array optical system according to the first embodiment. The exposure unit 1 emits exposure light 4 modulated according to the image data Di, and the exposed surface of the photosensitive drum 2 is exposed by the emitted exposure light 4.

  The photosensitive drum 2 serving as an electrostatic latent image carrier (photoconductor) is rotated clockwise by a motor 13. With this rotation, the photosensitive surface of the photosensitive drum 2 moves in the sub-scanning direction with respect to the exposure light 4. Above the photosensitive drum 2, a charging roller 3 that uniformly charges the surface of the photosensitive drum 2 is provided so as to contact the surface. The exposure unit 4 irradiates the surface of the photosensitive drum 2 charged by the charging roller 3 with exposure light 4.

  As described above, the exposure light 4 is modulated based on the image data Di, and an electrostatic latent image is formed on the surface of the photosensitive drum 2 by irradiating the exposure light 4. The formed electrostatic latent image is developed as a toner image by a developing device 6 disposed so as to contact the photosensitive drum 2 further downstream of the exposure light 4 irradiation position in the rotational direction of the photosensitive drum 2. .

  The toner image developed by the developing unit 6 is transferred onto a sheet 11 as a transfer material by a transfer roller (transfer unit) 7 disposed below the photosensitive drum 2 so as to face the photosensitive drum 2. The paper 11 is stored in the paper cassette 8 in front of the photosensitive drum 2 (on the right side in FIG. 10A), but can be fed manually. A paper feed roller 9 is disposed at the end of the paper cassette 8, and the paper feed roller 9 sends the paper 11 in the paper cassette 8 to the transport path 16.

  As described above, the sheet 11 on which the unfixed toner image is transferred is further conveyed to the fixing unit 12 behind the photosensitive drum 2 (left side in FIG. 10A). The fixing device 12 includes a fixing roller 12a having a fixing heater (not shown) therein and a pressure roller 12b disposed so as to be in pressure contact with the fixing roller 12a. The sheet 11 conveyed from the transfer unit 7 is heated while being pressed by the pressure contact portion between the fixing roller 12a and the pressure roller 12b, whereby the unfixed toner image on the sheet 11 is fixed. Further, a paper discharge roller 14 is disposed behind the fixing device 12, and the paper discharge roller 14 discharges the fixed paper 11 out of the image forming apparatus 5.

  Although not shown in FIG. 10A, the printer controller 10 performs not only the data conversion described above but also controls each part in the image forming apparatus 5 including the motor 13.

[Color image forming apparatus]
FIG. 10B is a sub-scan sectional view of a main part of 33 on which the lens array optical system according to the first embodiment is mounted.

The image forming apparatus 33 is a tandem type color image forming apparatus in which four exposure apparatuses are arranged in parallel, and image information is recorded on each photosensitive drum surface as an image carrier.
The image forming apparatus 33 includes exposure devices 17, 18, 19, and 20, photosensitive drums 21, 22, 23, and 24 as image carriers, and a developing device, each of which includes a light source and the lens array optical system according to the first embodiment. 25, 26, 27, 28. Further, the image forming apparatus 33 includes a conveyance belt 34, a printer controller 36, and a fixing device 37.

  The image forming apparatus 33 receives R (red), G (green), and B (blue) color signals from an external device 35 such as a personal computer. The input color signal is converted into C (cyan), M (magenta), Y (yellow), and K (black) image data (dot data) by a printer controller 36 in the image forming apparatus 33. The converted image data is input to the exposure devices 17, 18, 19, and 20, respectively. The exposure devices 17, 18, 19, and 20 emit exposure lights 29, 30, 31, and 32 that are modulated according to each image data, and the photosensitive drums 21, 22, 23, 24 photosensitive surfaces are exposed.

  A charging roller (not shown) for uniformly charging the surfaces of the photosensitive drums 21, 22, 23, and 24 is provided so as to contact the surface. The exposure devices 17, 18, 19, and 20 are irradiated with exposure light 29, 30, 31, and 32 on the surfaces of the photosensitive drums 21, 22, 23, and 24 charged by the charging roller.

  As described above, the exposure lights 29, 30, 31, and 32 are modulated based on the image data of each color, and the photosensitive drums 21, 22, and 23 are irradiated by irradiating the exposure lights 29, 30, 31, and 32. , 24 are formed on the surface. The formed electrostatic latent image is developed as a toner image by developing units 25, 26, 27, 28 arranged so as to abut on the photosensitive drums 21, 22, 23, 24.

  The toner images developed by the developing devices 25 to 28 are not shown as transfer materials conveyed on the conveyor belt 34 by a transfer roller (transfer device) (not shown) disposed so as to face the photosensitive drum 2. Multiple transfer onto a sheet of paper, forming a full color image on the sheet.

  As described above, the sheet on which the unfixed toner image is transferred is further conveyed to the fixing unit 37 behind the photosensitive drums 21, 22, 23, and 24 (left side in FIG. 10B). The fixing device 37 includes a fixing roller having a fixing heater (not shown) therein and a pressure roller arranged so as to be in pressure contact with the fixing roller. The sheet conveyed from the transfer unit is heated while being pressed at the pressing portion between the fixing roller and the pressure roller, whereby the unfixed toner image on the sheet is fixed. Further, a paper discharge roller (not shown) is disposed behind the fixing roller, and the paper discharge roller discharges the fixed paper to the outside of the image forming apparatus 33.

The color image forming apparatus 33 includes four exposure devices 17, 18, 19, and 20 that correspond to the colors C, M, Y, and K, respectively, and in parallel with the photosensitive drums 21, 22, 23, and 24, respectively. An image signal (image information) is recorded on the photosensitive surface, and a color image is printed at high speed.
As the external device 35, for example, a color image reading apparatus including a CCD sensor may be used. In this case, the color image reading apparatus and the color image forming apparatus 33 constitute a color digital copying machine.

[Image reading device]
FIG. 11 is a schematic cross-sectional view of an image reading apparatus 50 equipped with the lens array optical system according to the first embodiment.
The image reading device 50 has a configuration in which a reading unit 41 reads a document 40 arranged on the upper surface of a document table 43 made of a transmissive member. The document table 43 is supported by a frame 42, and the upper surface of the document table 43 coincides with the document surface of the document 40.

Here, the reading unit 41 includes an illumination unit that illuminates the document 40 via the document table 43, the lens array optical system according to the first embodiment, and the reflected light from the document 40 collected by the lens array optical system. A light receiving portion for receiving light.
Since the reading unit 41 is configured to be movable in the sub-scanning direction by a driving unit (not shown), the relative position between the document 40 and the lens array optical system can be changed in the sub-scanning direction. With this configuration, the reading unit 41 can sequentially read the document surface of the document 40 in the sub-scanning direction, and can acquire image data of the entire document surface of the document 40.

  At this time, the upper surface of the document table 43, that is, the document surface of the document 40 is disposed on the object surface of the lens array optical system, and the light receiving surface (sensor surface) of the light receiving unit is disposed on the image surface of the lens array optical system. Has been. As the light receiving unit, for example, a line sensor constituted by a CCD sensor, a CMOS sensor, or the like can be used.

  Note that the image reading apparatus 50 may be configured to receive the transmitted light from the document 40 illuminated by the illumination unit by the light receiving unit. Further, the illumination unit is not limited to the one including the light source, and a configuration in which light from the outside is guided to the document 40 may be adopted.

102 lens array optical system 107 first lens array 108 light shielding member 109 second lens array 1083 middle plate 1083b light shielding bottom surface (scattering surface)

Claims (14)

A first lens array configured by arranging a plurality of lens arrays including a plurality of lenses arranged in a first direction in a second direction perpendicular to the first direction and the optical axis direction;
A second lens array configured by arranging a plurality of lens rows including a plurality of lenses arranged in the first direction in the second direction;
A light shielding member disposed between the first lens array and the second lens array;
A lens array optical system comprising:
The lens array optical system forms an erect image of an object in a first cross section perpendicular to the second direction, and forms an inverted image of the object in a second cross section perpendicular to the first direction. Formed,
The light shielding member has an intermediate plate disposed between adjacent lens rows of the first lens array in the second direction,
The lens array optical system, wherein the intermediate plate includes a scattering surface parallel to the first cross section.   The lens array optical system according to claim 1, wherein the lens array optical system forms an erecting equal-magnification image of the object in the first cross section.   The lens array optical system according to claim 1, wherein the scattering surface is provided with a texture.   The lens array optical system according to claim 3, wherein an average depth of the texture on the scattering surface is 8 μm or more and 30 μm or less. When the length of the intermediate plate in the second direction is D, and the distance in the optical axis direction between the first lens array and the second lens array is Δ,
D ≦ 0.18Δ
The lens array optical system according to claim 1, wherein the following condition is satisfied. When the length of the intermediate plate in the second direction is D, and the effective diameter of the lens array optical system in the second direction is Rs,
D / Rs ≦ 0.1
The lens array optical system according to claim 1, wherein the following condition is satisfied. The length of the intermediate plate in the second direction is D, the distance in the optical axis direction between the first lens array and the second lens array is Δ, and the second direction of the lens array optical system. When the effective diameter at is Rs,
(0.18Δ-D) /Rs≧0.05
The lens array optical system according to any one of claims 1 to 6, wherein the following condition is satisfied.   The plurality of lens rows of the first lens array and the second lens array are staggered in the second direction, according to any one of claims 1 to 7. The lens array optical system described.   9. The first lens array and the second lens array have a symmetrical shape with respect to an intermediate image plane on which an intermediate image is formed. The lens array optical system according to 1. For at least one of the first and second lens arrays, when the distance between the optical axes of two lenses adjacent in the second direction in the first direction is 0, the lenses of the two lenses The surface is

(Where X, Y, and Z are optical axis directions, the coordinates of the first direction and the second direction, and C _{i, j} is an aspheric coefficient), respectively, The lens array optical system according to any one of claims 1 to 9.   11. The lens array optical system according to claim 1, wherein each of the plurality of lenses includes a lens surface having a rectangular aperture shape. 11.   The lens according to claim 1, wherein the plurality of lenses include anamorphic surfaces having different powers in the first cross section and in the second cross section. Array optical system.   13. The lens array optical system according to claim 1, a developing device that develops an electrostatic latent image formed by the lens array optical system as a toner image, and the developed toner image. An image forming apparatus comprising: a transfer device that transfers to a transfer material; and a fixing device that fixes the transferred toner image to the transfer material.   An image reading apparatus comprising: the lens array optical system according to any one of claims 1 to 12; and a light receiving unit that receives a light beam from a document condensed by the lens array optical system. .

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