JP2010164717A - Lens array, lens unit, led head, exposure device, image forming apparatus, and reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent degradation in resolution by suppressing a relative displacement and a shape difference between members, due to contraction and expansion of their materials. <P>SOLUTION: In a lens array in which a plurality of lens elements are arrayed so as to form lines extending in a direction nearly orthogonal to an optical axis. In the lens array, a positioning part that engages with a light shield member is disposed substantially in the middle in the direction that the lens elements are arrayed. A lens unit includes: a lens array in which a plurality of lens elements are arrayed so as to form lines extending in a direction nearly orthogonal to an optical axis; and a light shield member in which a plurality of diaphragms through which the optical axis passes are disposed so as to extend in the direction nearly orthogonal to the optical axis. In the lens unit, the plurality of lens arrays of the identical shape are arranged opposite each other so that the optical axes of the lens elements are aligned with each other. One of the lens array is disposed in the position where this lens array is rotated relative to the other lens array, with a straight line parallel to the array direction of the lens elements as a rotation axis. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lens array, a lens unit, an LED head, an exposure apparatus, an image forming apparatus, and a reading apparatus.

Conventional lens arrays are used to form an image of a read original on an electrophotographic image forming apparatus using an LED head in which a plurality of LEDs (light emitting diodes) are linearly arranged, or on a light receiving portion in which a plurality of light receiving elements are linearly arranged. It is used as an optical system that can form an erecting equal-magnification image of an object in a line on a reading device such as a scanner or a facsimile.
This lens array forms a lens group composed of a plurality of lenses so as to form an erecting equal-magnification image of an object. There is an optical system that can be formed, and a plurality of lenses are integrally formed by injection molding to reduce the number of parts (for example, see Patent Document 1).

JP 2008-92006 A (paragraph “0032” to paragraph “0039”, FIG. 1)

However, in the above-described conventional technology, each member constituting the optical system has a long shape that is long in the lens arrangement direction. Therefore, relative displacement and shape change of each member due to contraction and expansion of the material. Occurs and the resolution of the optical system is lowered.
An object of the present invention is to solve such a problem, and an object of the present invention is to suppress a relative positional shift and a difference in shape of each member due to contraction and expansion of a material, and to prevent a decrease in resolution.

Therefore, the lens array according to the present invention is a lens array in which a plurality of lens elements are arranged so as to form a row extending in a direction substantially orthogonal to the optical axis. A positioning portion that engages with the light shielding member is disposed in the center.
The lens unit according to the present invention includes a lens array in which a plurality of lens elements are arranged to form a row extending in a direction substantially orthogonal to the optical axis, and a plurality of stops through which the optical axis passes. In a lens unit having a light shielding member arranged so as to extend in a direction substantially orthogonal to the optical axis, the optical axes of the lens elements of the plurality of lens arrays having substantially the same shape coincide with each other. The one lens array is arranged at a position rotated with respect to the other lens array about a straight line parallel to the arrangement direction of the lens elements as a rotation axis.

  According to the present invention thus configured, it is possible to suppress the relative position shift and shape difference of each member due to the contraction and expansion of the material, and to prevent the resolution from being lowered.

Exploded perspective view of the lens unit in the first embodiment 1 is a schematic diagram showing the configuration of a printer in a first embodiment. Schematic side view of the LED head in the first embodiment Schematic sectional view of the LED head in the first embodiment Plan view of the lens unit in the first embodiment BB sectional view of the lens unit in the first embodiment CC sectional view of the lens unit in the first embodiment Plan view of the lens array in the first embodiment The top view of the light-shielding member in a 1st Example The top view of the opening part of the light shielding member in a 1st Example Explanatory drawing which shows operation | movement of the lens array in a 1st Example. Explanatory drawing which shows operation | movement of the lens unit in 1st Example. Explanatory drawing of image evaluation of the image forming apparatus in the first embodiment Schematic which shows the structure of the reader in 2nd Example. Schematic which shows the structure of the read head of the reader in 2nd Example. Schematic which shows operation | movement of the read head of the reader in 2nd Example.

  Hereinafter, embodiments of a lens array, a lens unit, an LED head, an exposure apparatus, an image forming apparatus, and a reading apparatus according to the present invention will be described with reference to the drawings.

A printer as an information processing apparatus according to this embodiment will be described with reference to a schematic diagram illustrating a configuration of the printer according to the first embodiment shown in FIG.
In FIG. 2, a printer 100 forms an image on a print medium based on image data with toner made of a resin containing a pigment as a color material.
The printer 100 is provided with a paper feed cassette 60 that stores paper 101 as a printing medium, and includes a paper feed roller 61 that takes out the paper 101 from the paper feed cassette 60, and a transport roller 62 that feeds and transports the paper 101. , 63 are arranged.

  The printer 100 according to the present invention is a color electrophotographic system, and a photosensitive drum 41 as an electrostatic latent image carrier that forms an image of each color of yellow, magenta, cyan, and black as an image forming unit in the printer 100. The electrostatic latent image formed on the photosensitive drum 41 is developed with toner, a developing device 5 that forms a toner image, and a toner cartridge 51 that supplies toner to the developing device 5 are arranged along the conveyance path of the paper 101. Has been placed.

Further, a charging roller 42 for supplying electric charges to the surface of the photosensitive drum 41 and an LED head 3 as an optical head are disposed so as to face the surface of the photosensitive drum 41, and the LED head 3 is charged by the charging roller 42. An electrostatic image is formed by selectively irradiating light on the surface of the photosensitive drum 41 charged in step S4 based on image data.
Further, a transfer roller 80 formed on the photosensitive drum 41 and transferring a toner image, which is an image obtained by visualizing an electrostatic latent image with toner, onto the paper 101 sandwiches a transfer belt 81 that conveys the paper 101 at the transfer portion. The cleaning blade 43 is disposed so as to face the photosensitive drum 41 and removes the toner remaining on the surface of the photosensitive drum 41 after the sheet 101 passes through the transfer portion. Are arranged.

A fixing device 9 for fixing the toner image formed on the paper 101 with heat and pressure is disposed downstream of the transfer unit, and the conveying roller 64 that conveys the paper 101 that has passed through the fixing device 9 and the conveying roller 64. A discharge roller 65 that discharges the sheet 101 on which the conveyed paper 101 on which the image is formed is stored is disposed.
A predetermined voltage is applied to the charging roller 42 and the transfer roller 80 by a power source (not shown). The transfer belt 81, the photosensitive drum 41, and each roller are rotationally driven by a motor (not shown) and a gear that transmits driving (not shown). Furthermore, a power source and a control device are connected to the developing device 5, the LED head 3, the fixing device 9, and each motor (not shown).

The printer 100 has an external interface that receives print data from an external device, and forms an image on a print medium based on the print data received by the external interface.
The printer 100 configured as described above includes a control unit that stores a control program in a storage unit such as a memory and controls the whole based on the control program, and a control unit as a calculation unit.

Next, the configuration of the LED head 3 as an exposure apparatus will be described based on a schematic side view of the LED head in the first embodiment of FIG.
A lens unit 1 is disposed in the LED head 3, and the lens unit 1 is fixed to the LED head 3 by a holder 34. In addition, the plurality of LED elements 30 as light emitting units are arranged on the wiring board 33 in a substantially straight line.

The lens unit 1 is long and is arranged in parallel with the LED elements 30 arranged in a substantially straight line, and the lens unit 1 and the photosensitive drum 41 on which the electrostatic latent image is formed are arranged in parallel. Furthermore, the optical axis of the microlens of the lens unit 1 is arranged so as to be in the vertical direction in the figure.
FIG. 4 is a schematic cross-sectional view of the LED head in the first embodiment, and is a cross-sectional view taken along AA in FIG.

  In FIG. 4, the optical axis of the microlens 12 of the lens unit 1 is arranged in the vertical direction in the figure, and the LED element 30 and the driver IC 31 are arranged on the wiring board 33. The LED element 30 and the driver IC 31 are connected by a wire 32, and the LED element 30 as a light emitting unit is controlled by the driver IC 31 to emit light. In addition, the LED elements 30 are arranged in a line of a straight line and are arranged at intervals of PDmm (millimeters).

With this lens unit 1, an image of the LED element 30 is formed on the photosensitive drum 41, and an electrostatic latent image is formed on the photosensitive drum 41 by causing the LED element 30 to emit light in accordance with the rotation of the photosensitive drum 41. Is done.
In this embodiment, the LED head 3 has a resolution of 600 dpi (dots per inch), and 600 LED elements 30 are arranged per inch (1 inch is about 25.4 mm). That is, the LED elements 30 are arranged with a spacing PD of 0.0423 mm.

Next, the configuration of the lens unit 1 will be described based on an exploded perspective view of the lens unit in the first embodiment of FIG.
In FIG. 1, the lens unit 1 includes a lens array 10 and a light shielding member 20 as an assembly of lens elements.
In the lens array 10, microlenses 12 as a plurality of lens elements are arranged in two rows substantially parallel to each other as an arrangement interval PY. Further, two lens arrays 10 having substantially the same shape are arranged opposite to the lens unit 1. That is, the lens unit 1 has a configuration in which a lens group including two microlenses 12 arranged so that their optical axes coincide with each other is arranged in two rows in a direction substantially orthogonal to the optical axis. The lens array 10 is formed of a material that transmits the light rays of the light emitting unit.

In the lens unit 1, one lens array 10 out of the two lens arrays 10 is rotated 180 degrees with respect to the other lens array 10 around a straight line 25 parallel to the arrangement direction of the microlenses 12 as a rotation axis. Is done.
The lens array 10 has a long shape that is long in the direction in which the microlenses 12 are arranged, and the characteristics such as composition and density of the material (distribution of material characteristics) are slightly at each position in the arrangement direction of the microlenses 12. Is different. Therefore, when the lens array 10 contracts or expands due to heating and cooling of the lens array 10 in the manufacturing process and changes in temperature and humidity in the usage environment, the contraction rate or expansion rate differs at each position in the arrangement direction of the microlenses 12. Come.

  A lens unit 1 having a conventional configuration different from the present invention, that is, one lens array 10 rotates 180 degrees with respect to the other lens array 10 about a straight line orthogonal to both the arrangement direction of the microlenses 12 and the optical axis as a rotation axis. In the lens unit 1 arranged in this manner, when the lens array 10 contracts or expands due to changes in temperature or humidity, the optical axes of the microlenses 12 of the two lens arrays 10 arranged opposite to each other are A defect that does not match occurs.

  However, in the lens unit 1 configured according to the present invention, of the two lens arrays 10, one lens array 10 has a rotation axis that is a straight line parallel to the arrangement direction of the microlenses 12 with respect to the other lens array 10. Since the material characteristics of one lens array 10 and the material characteristics of the other lens array 10 substantially coincide with each other because they are rotated by 180 degrees, the lens array 10 contracts or expands due to changes in temperature and humidity. Even when this is done, the optical axes of the microlenses 12 coincide.

Further, in the lens unit 1, one lens array 10 is arranged with a spacing PY / 2 in the arrangement direction of the microlenses 12 with respect to the other lens array 10, so that the light of the microlenses 12 of the one lens array 10 is disposed. The optical axis of the micro lens 12 of the other lens array 10 coincides with the axis.
In the light shielding member 20, an opening 22 as a diaphragm is formed as a through hole so as to correspond to the arrangement of the microlenses 12 of the lens array 10. The arrangement interval of the openings 22 is the same as the arrangement of the microlenses 12 of the lens array 10 and is arranged so that the optical axis of the microlenses 12 and the position of the openings 22 coincide. The openings 22 are arranged in a direction substantially orthogonal to the optical axis.

  Here, in the case where the microlenses 12 are arranged in an even number column in the lens array 10, the lens array 10 is n × interval PY / 2 in the arrangement direction of the microlens 12 with respect to the other lens array 10 (n is an integer other than 0) ) By displacing, the optical axis of each microlens 12 of one lens array 10 and the optical axis of the microlens of the other lens array 10 can be matched.

  Further, the lens unit 1 can be configured by arranging the microlenses 12 in the lens array 10 in an odd-numbered row. In this case, one lens array 10 is arranged without being shifted in the arrangement direction of the microlenses 12 with respect to the other lens array 10, and the optical axis of each microlens 12 of the one lens array 10 and the other lens array 10. The optical axis of the microlens can be matched.

Furthermore, the two lens arrays 10 of the lens unit 1 can be configured using members having different shapes without having the same shape. At this time, it is assumed that the arrangement intervals of the microlenses 12 of the two lens arrays 10 are the same, and the optical axes of the microlenses 12 of the two lens arrays 10 are aligned.
In addition, the lens unit 1 can be constituted by two or more lens arrays 10.

  Further, the lens array 10 is formed with a positioning portion 13 for determining the relative position of the lens array 10 and the light shielding member 20 in the arrangement direction of the microphone lens 12, and the lens array 10 and the microphone lens 12 of the light shielding member 20. A convex portion 14 is formed for determining a position in a direction orthogonal to the arrangement direction. In the lens array 10, ribs 11 are formed on both sides parallel to the arrangement direction of the microlenses 12.

On the other hand, the light shielding member 20 is formed with ribs 21 on both sides parallel to the arrangement direction of the openings 22, and the ribs 21 are formed with concave portions 23 that engage with the positioning portions 13 of the lens array 10 and convex portions of the lens array 10. An abutting portion 24 that contacts the portion 14 is formed.
By inserting the positioning portion 13 of the lens array 10 into the concave portion 23 of the light shielding member 20, the relative position of the lens array 10 and the microlens 12 of the light shielding member 20 in the arrangement direction is determined, and the abutting portion 24 of the light shielding member 20 is placed. By abutting the convex portions 14 of the lens array 10, the positions of the lens array 10 and the light blocking member 20 in the direction orthogonal to the arrangement direction of the microlenses 12 and the optical axis direction are determined.

  FIG. 5 is a plan view of the lens unit in the first embodiment. FIG. 5A is a plan view of the lens unit 1 in FIG. 4 as viewed from above downward (the optical axis direction of the microlens 12). FIG. 5B is a plan view of the lens unit 1 in FIG. It is the top view seen from above to the upper direction (optical axis direction of the micro lens 12). The lens unit 1 shown in FIG. 5B is obtained by rotating the lens unit 1 shown in FIG. 5A 180 degrees about a straight line parallel to the arrangement direction of the microlenses 12 as a rotation axis. The vertical direction in the figure is the direction in which the microlenses 12 are arranged.

In FIG. 5, the positioning portion 13 is disposed at approximately the center in the arrangement direction of the microlenses 12 of the lens array 10, and the recess 23 is disposed at approximately the center in the arrangement direction of the openings 22 of the light shielding member 20.
Since the lens unit 1 has a long and long shape in the arrangement direction of the microlenses 12, a lens unit having a configuration different from that of the present invention, that is, a lens in which the positioning portion 13 and the concave portion 23 are arranged at one end portion of the lens unit. In the case of a unit, since the other end of the lens unit is separated from the positioning unit 13 and the recess 23, the optical axis of the microlens 12 and the aperture as an aperture stop as the optical characteristics change due to the expansion or contraction of the material. It is conceivable that the position of the portion 22 is displaced.

However, in the lens unit 1 of the present invention, the positioning portion 13 and the concave portion 23 are arranged at substantially the center of the lens unit 1, so that the optical axis of the microlens 12 and the aperture as the diaphragm are caused by the expansion or contraction of the material. Deviations in the position of the portion 22 can be suppressed small.
The convex portions 14 are arranged at a plurality of positions along the arrangement direction of the microlenses 12 of the lens array 10, and the abutting portions 24 are arranged in the arrangement direction of the openings 22 of the light shielding member 20 so as to contact the convex portions 14. It is arranged at a plurality of positions along.

  Further, when the microlenses 12 are arranged in an even number of rows in a zigzag pattern so as to form a staggered pattern, the shift amount SH in the arrangement direction of the microlenses 12 of the two lens arrays 10 is set, and the lens array 10 is set to the other lens array. By setting nx interval PY / 2 (n is an integer other than 0) in the arrangement direction of the microlenses 12 with respect to 10, the optical axis of each microlens 12 of one lens array 10 and the other lens array 10 The optical axes of the microlenses 12 can be matched.

When two lens arrays 10 having substantially the same shape, which are arranged in an even number of rows in a staggered pattern, are arranged facing each other, at least one of the end portions of the microlenses 12 of the lens array 10 is arranged. This microlens 12 cannot be used because the microlens 12 of the other lens array 10 having the same optical axis does not exist.
FIG. 6 is a cross-sectional view of the lens unit in the first embodiment, and is a cross-sectional view taken along a plane orthogonal to the arrangement direction of the microlenses 12 at the position BB in FIG.

In FIG. 6, in the lens unit 1, the optical axis AX1 of the microlenses 12 of the two lens arrays 10 coincides, and the position of the opening 22 of the light shielding member 20 coincides with the optical axis AX1.
The positioning portion 13 of the lens array 10 is inserted into the concave portion 23 of the light shielding member 20 to determine the relative positions of the lens array 10 and the light shielding member 20 in the arrangement direction of the microlenses 12.

FIG. 7 is a cross-sectional view of the lens unit in the first embodiment, and is a cross-sectional view taken along a plane orthogonal to the arrangement direction of the microlenses 12 at the position CC in FIG.
In FIG. 7, in the lens unit 1, the optical axis AX1 of the microlenses 12 of the two lens arrays 10 coincides, and the position of the opening 22 of the light shielding member 20 coincides with the optical axis AX1.

The convex portion 14 of the lens array 10 is abutted against the abutting portion 24 of the light shielding member 20, and the relative relationship between the lens array 10 and the light shielding member 20 in the direction orthogonal to both the arrangement direction of the microlenses 12 and the optical axis AX1. A position is defined.
FIG. 8 is a plan view of the lens array in the first embodiment.
In FIG. 8, in the lens array 10, a plurality of microlenses 12 are alternately arranged in two substantially straight lines in parallel, that is, zigzag in a zigzag manner, and the intervals between the microlenses 12 arranged in each row are arranged. Is PY, and the interval between two parallel rows, that is, the direction perpendicular to the arrangement direction of the microlenses 12 is PX.

The two rows of microlenses 12 and the straight lines on which the plurality of LED elements 30 (not shown) are arranged are parallel to each other, and the two rows of microlenses 12 and the straight lines on which the plurality of LED elements 30 (not shown) are arranged Are configured to be equal in distance.
The radius of each microlens 12 is RL, and is arranged so as to overlap the adjacent microlens 12 with a distance PN between the centers of adjacent microlenses 12, and the portion in contact with the adjacent microlens 12 is the optical axis. They are connected in a shape cut by parallel planes. In addition, ribs 11 are formed in the lens array 10 in parallel with the arrangement direction of the microlenses 12.

The lens array 10 is formed of a material that transmits the light rays of the LED elements 30.
In this embodiment, the lens array 10 uses an optical resin (trade name: ZEONEX (registered trademark) E48R, manufactured by Nippon Zeon Co., Ltd.), which is a cycloolefin resin, and a plurality of microlenses 12 are integrated by injection molding. Molded into.

  Each curved surface of the microlens 12 (the boundary surface between the microlens 12 and the air layer) is configured by a polynomial aspherical surface expressed by Equation 1. Z (r) represents a rotating coordinate system in which the direction parallel to the optical axis of the microlens 12 is an axis and the coordinate in the radial direction is r, the vertex of each curved surface of the microlens 12 is the origin, and the microlens 12 side The direction of is represented by a positive number, and the direction on the air layer side is represented by a negative number. At this time, the radius r is expressed by Equation 2 using the values of the X coordinate and the Y coordinate. k is a conic constant, C is a radius of curvature, A is an aspherical coefficient, and l and m are positive integers.

図９は、第１の実施例における遮光部材の平面図である。
図９において、遮光部材２０には、複数の開口部２２が略直線に配列され、また開口部２２の配列方向と平行にリブ２１が形成されている。

FIG. 9 is a plan view of the light shielding member in the first embodiment.
In FIG. 9, a plurality of openings 22 are arranged in a substantially straight line on the light shielding member 20, and ribs 21 are formed in parallel with the arrangement direction of the openings 22.

The light shielding members 20 have openings 22 formed at intervals PY, and are arranged in two rows at intervals PX in a direction orthogonal to the arrangement direction of the openings 22. This arrangement interval coincides with the interval between the optical axes of the microlenses 12.
Further, the opening 22 is formed with a distance PN between the centers corresponding to the adjacent microlenses 12, and is further formed so as to hold the interval TB in a direction orthogonal to the arrangement direction of the microlenses 12. .

The light shielding member 20 is formed of a material that shields the light from the LED element 30.
FIG. 10 is a plan view of the opening of the light shielding member in the first embodiment.
In FIG. 10, the opening 22 has a shape composed of a circle with a radius RA and a straight line parallel to the arrangement direction of the microlenses 12 at a position of (interval PX−interval TB) / 2 from the center of the circle with the radius RA. The center of the circle of radius RA of the opening 22 is arranged so as to coincide with the optical axis AX1 of the microlens 22.

The light shielding member 20 of this example was prepared by injection molding using polycarbonate.
Next, details of the lens unit 1 will be described based on an explanatory view showing an operation of the lens array in the first embodiment of FIG. 11 is a cross-sectional view of the lens unit 1 including the lens array 10, the object plane OP, and the imaging plane IP, and is a cross-sectional view of a plane including the optical axis AX1 of two adjacent microlenses 12, that is, FIGS. It is sectional drawing in the position of the straight line DD in.

In FIG. 11, the first microlens 12a and the second microlens 12b are opposed to the first microlens 12a so that their optical axes coincide with each other at a distance LO from the object plane OP of the lens unit 1, and the distance LS. Are arranged apart from each other. The imaging plane IP of the lens unit 1 is a position separated from the second microlens 12b by a distance LI in the optical axis direction.
The first microlens 12a has a thickness of LT1, and forms an image of the object 30a located at a distance LO1 in the optical axis AX1 direction as an intermediate image 30b on an intermediate image plane IMP separated by a distance LI1 in the optical axis direction. .

The second microlens 12b has a thickness LT2 and forms an image 30c of the intermediate image 30b on the intermediate image plane IMP at the position of the distance LO2 at a position separated by the distance LI2 in the optical axis AX1 direction.
The distance LO from the object plane OP of the lens unit 1 to the first microlens 12a is set equal to the distance LO1, and the distance LS between the first microlens 12a and the second microlens 12b is (distance LI1 + distance LO2). The distance LI from the second microlens 12b to the image plane IP of the lens unit 1 is set equal to the distance LI2.

In addition, the first microlens 12a and the second microlens 12b can be lenses having the same configuration. At this time, both the first microlens 12a and the second microlens 12b have a thickness LT1, and the distance LO from the object plane of the lens unit 1 to the first microlens 12a is set equal to the distance LO1. The
Further, a surface having the same shape as the object surface side curved surface of the first microlens 12a is arranged so as to be a curved surface on the image forming surface side of the second microlens 12b. The distance LO2 to the intermediate image plane IMP is set equal to LI1.

The distance LS between the first microlens 12a and the second microlens 12b is set to (2 × distance LI1), and the distance LI from the second microlens 12b to the image plane of the lens unit 1 is the distance LO1. Equally set, distance LI = distance LO.
Thus, in the lens unit 1, the two lens arrays 10 are held so as to face each other with the light shielding member 20 interposed therebetween, and are opposed to each other so that the image can be formed on the imaging surface. The two microlenses 12 are arranged at conjugate positions with the optical axes coincident with the light shielding member 20 in between, and an optical system with erecting equal magnification is formed. As described above, the optical system including the two microlenses 12 whose optical axes coincide with each other can form the image of the LED element 30 on the surface of the photosensitive drum 41 at an equal magnification.

Further, the light blocking member 20 blocks stray light (part of light) entering from the other optical system into the optical system composed of two microlenses between the lens arrays 10 and having the same optical axis, and also to other optical systems. It is blocked so as not to emit stray light.
The operation of the above configuration will be described.
First, the operation of the printer 100 will be described with reference to FIG.

  The surface of the photosensitive drum 41 of the printer 100 is charged by a charging roller 42 to which a voltage is applied by a power supply device (not shown). Subsequently, when the surface of the photosensitive drum 41 charged by the rotation of the photosensitive drum 41 reaches the vicinity of the LED head 3, the surface is exposed by the LED head 3, and an electrostatic latent image is formed on the surface of the photosensitive drum 41. . This electrostatic latent image is developed by the developing device 5, and a toner image is formed on the surface of the photosensitive drum 41.

On the other hand, the paper 101 set in the paper feed cassette 60 is taken out from the paper feed cassette 60 by the paper feed roller 61 and is transported to the vicinity of the transfer roller 80 and the transfer belt 81 by the transport rollers 62 and 63.
When the photosensitive drum 41 rotates and the toner image on the surface of the photosensitive drum 41 obtained by development reaches the vicinity of the transfer roller 80 and the transfer belt 81, a transfer roller to which a voltage is applied by a power supply device (not shown). The toner image on the surface of the photoconductive drum 41 is transferred onto the paper 101 by 80 and the transfer belt 81.

  Subsequently, the paper 101 on which the toner image is formed is conveyed to the fixing device 9 by the rotation of the transfer belt 81, and the toner image on the paper 101 is heated while being pressed by the fixing device 9 to be melted. And fixed on the sheet 101. The sheet 101 on which the toner image is fixed is discharged to the discharge unit 7 by the transport roller 64 and the discharge roller 65, and the operation of the printer 100 is completed.

Next, the operation of the LED head 3 as an exposure apparatus will be described with reference to FIG.
When a control signal for the LED head 3 is transmitted from the control unit of the printer 100 based on the image data, the driver IC 31 causes the LED element 30 to emit light with an arbitrary light amount based on the control signal. The light beam from the LED element 30 enters the lens unit 1, and an image is formed on the photosensitive drum 41.

Next, the operation of the lens unit 1 will be described with reference to FIG.
The light beam of the LED element 30 as the object 30a enters the first microlens 12a, and the first microlens 12a forms an intermediate image 30b on the intermediate image plane MIP located at a distance LI1 in the optical axis direction. Is done. Further, an image 30c that is an image of the intermediate image 30b is formed on the image plane IP by the second microlens 12b, whereby an image 30c of the object 30a is formed on the image plane IP. At this time, the image 30c is an erecting equal-magnification image of the object 30a.

The intermediate image 30b formed by the first microlens 12a is an inverted reduced image of the object 30a, and the imaging 30c is an inverted enlarged image of the intermediate image 30b by the second microlens 12b.
Further, the first microlens 12a and the second microlens 12b are so-called telecentric in which principal rays of light rays from each point on the object plane are parallel.

In this way, the lens unit 1 forms an erecting equal-magnification image of the LED element 30.
Further, after the light beam from the LED element 30 is emitted from the first microlens 12 a, the light beam that does not contribute to image formation is blocked by the light blocking member 20.
On the other hand, when the first microlens 12a and the second microlens 12b are lenses having the same configuration, the lens unit 1 forms an erecting equal-magnification image of the object 30a.

  The light beam of the LED element 30 as the object 30a is incident on the first micro lens 12a, and is intermediate on the intermediate image plane MIP located at a position (LS / 2) away in the optical axis direction by the first micro lens 12a. An image 30b is formed. Further, an image 30c that is an image of the intermediate image 30b is formed on the image plane IP by the second microlens 12b. At this time, the image 30c is an erecting equal-magnification image of the object 30a.

Further, the first micro lens 12a and the second micro lens 12b are telecentric.
In this way, even when the first microlens 12 a and the second microlens 12 b have the same configuration, the lens unit 1 forms an erecting equal-magnification image of the LED element 30.
In the lens unit 1 of the present invention, one of the two lens arrays 10 is rotated 180 degrees with respect to the other lens array 10 around a straight line parallel to the arrangement direction of the microlenses 12 as a rotation axis. Therefore, even if the lens array 10 contracts or expands due to changes in temperature and humidity, the distribution of the material characteristics of one lens array 10 and the distribution of the material characteristics of the other lens array 10 are substantially the same. The optical axes of the microlenses 12 coincide.

Further, in the lens unit 1 of the present invention, the positioning portion 13 and the concave portion 23 are arranged at substantially the center of the lens unit 1, so that the optical axis of the microlens 12 and the aperture as the diaphragm are caused by the expansion or contraction of the material. Deviation from the position of the portion 22 can be kept small.
Further, the operation of the lens unit 1 will be described based on the explanatory views showing the operation of the lens unit in the first embodiment of FIGS.

12A shows the lens unit 1 in the first embodiment. In FIG. 12A, the first microlens 12a and the second microlens 12b of the two lens arrays 10 of the lens unit 1 are the same. Of the configuration. The magnifications of the first microlens 12a and the second microlens 12b on the lens array 10 are m1 and m2.
Here, the magnifications m1 and m2 are ratios of the size of the intermediate image formed by the microlens 12 to the size of the object. Specifically, in FIG. 11, the intermediate image separated from the first microlens 12a by the distance LI1. This is the ratio of the size of the intermediate image 30b formed on the surface IMP to the size of the object 30a on the object plane OP that is a distance LO1 away from the first microlens 12a.

  In addition, m1 represents a plurality of first microlenses 12a (second microlenses 12b) near one end in the arrangement direction of the first microlenses 12a (second microlenses 12b) in FIG. The magnification m2 is the magnification of the plurality of first microlenses 12a (second microlenses 12b) near the other end in the arrangement direction of the first microlenses 12a (second microlenses 12b). It is. The lens array 10 has a long shape, and the optical characteristics such as the shape and refractive index of the microlens 12 are different at each position in the longitudinal direction. Therefore, the magnification m1 and the magnification m2 are slightly different, and m1 ≠ m2. It has become.

  In FIG. 12A, Sa is the size of the object 30a, and Sc1 is a plurality of first microlenses 12a near one end in the arrangement direction of the first microlenses 12a (second microlenses 12b). The size of the image 30c formed by the (second microlens 12b), Sc2 is a plurality of first portions near the other end in the arrangement direction of the first microlens 12a (second microlens 12b). In the lens unit 1 having the configuration of the present embodiment, the sizes Sc1 and Sc2 of the imaging 30c are Sc1 = Sc1 = Sc1 = Sc1 = Sc1 = Sc1 = Sc1 = Sc1 = Sc1 = Sc1 = Sa × m1 / m1 = Sa and Sc2 = Sa × m2 / m2 = Sa.

  On the other hand, FIG. 12B shows the lens unit 1 in which one lens array 10 is rotated 180 degrees with respect to the other lens array 10 with a straight line orthogonal to the lens element arrangement direction as a rotation axis. ing. In this case, the sizes Sc1 and Sc2 of the imaging 30c are Sc1 = Sa × m1 / m2 ≠ Sa and Sc2 = Sa × m2 / m1 ≠ Sa, respectively, and an erecting equal-magnification image cannot be formed.

Therefore, in the case of the lens unit 1 in which one lens array 10 is rotated 180 degrees with respect to the other lens array 10 with a straight line orthogonal to the lens element arrangement direction as a rotation axis, the magnification m1 = m2. Thus, the accuracy of the optical characteristics such as the shape and refractive index of the microlens 12 at each position in the longitudinal direction must be strictly managed.
In the present embodiment, the accuracy of the optical characteristics such as the shape and refractive index of the microlens 12 at each position in the longitudinal direction can be relaxed.

With respect to the LED head 3 using the lens array 10 of this example, MTF (Modulation Transfer Function) indicating the resolution of image formation was measured, and a value of 80% or more was measured.
Here, MTF indicates the resolution of the exposure apparatus, and indicates the contrast of image formation of the LED element 30 that is lit in the exposure apparatus. 100% indicates that the imaging contrast is the highest and the resolution as the exposure apparatus is high. The smaller the contrast, the smaller the contrast of the light amount, and the lower the resolution of the exposure apparatus.

MTF (%) is EMAX as the maximum value of the amount of imaged light, and EMIN as the minimum value of the amount of light between two adjacent images.
MTF = (EMAX−EMIN) / (EMAX + EMIN) × 100 (%)
Is defined as follows.
In this MTF measurement, an image formed at a distance LI (mm) away from the apex of the image forming surface side lens of the second microlens 12b on the image forming surface IMP of the lens unit 1 of the LED head 3 is microscopic digital. The MTF was calculated by photographing with a camera, analyzing the light distribution of the image of the LED element 30 from the photographed image.

Further, in the MTF measurement, the LED head 3 in which the arrangement interval PD of the LED elements 30 is 0.0423 mm was used.
Further, the MTF value and the image quality of the image forming apparatus will be described.
Originally, the portion of the image formed by the image forming apparatus where no toner is applied must have a sufficiently high potential in the electrostatic latent image. In addition, the image formed by the LED head must be dark. However, if the MTF value is small, the light beam is incident on a portion that must be dark in the image formed by the LED head.

When the light beam enters, the potential of the electrostatic latent image where the potential must be sufficiently high is lowered, and the toner adheres to the portion of the image forming apparatus where the toner is not originally placed.
In the image forming apparatus image, the portion where no toner is applied is originally composed of the white color of the paper, but the portion where the toner is attached appears to be mixed with the toner color, so image formation The image quality of the device is degraded.

As a result of various evaluations, when the MTF was 80% or more, the image of the image forming apparatus was a good image without streaks or light and dark spots.
Next, when an image of the image forming apparatus on which the lens unit of this example was mounted was evaluated using a color LED printer, a good image free of streaks and shading was obtained. In the image evaluation of the image forming apparatus, an image in which dots are formed every other pixel among all the pixels shown in FIG. 13 is formed on the entire surface of the printing area, and the quality of the image is evaluated. In FIG. 13, reference numeral 301 denotes a dot on which toner is placed, and 302 denotes a dot on which toner is not placed.

In the present embodiment, the microlens 12 is composed of a rotationally symmetric high-order aspheric surface, but the present invention is not limited to this, and a spherical surface may be formed. Moreover, you may form curved surfaces, such as an anamorphic aspherical surface, a paraboloid, an ellipsoid, a hyperboloid, a conic surface.
Further, although the lens array 10 is created by general injection molding, a molding method such as compression injection molding may be used. Furthermore, although the material of the lens array 10 uses resin, glass may be used.

Moreover, although the light shielding member 20 was produced by injection molding using polycarbonate, it is not limited to this, and may be produced by cutting, or may be produced by etching a metal.
In addition, an LED array in which a plurality of LED elements 30 are arranged is used as a light emitting unit. However, for example, an organic EL may be used as a light emitting unit, a semiconductor laser may be used, and a light emitting unit such as a fluorescent lamp or a halogen lamp is used. An exposure apparatus using a shutter composed of a liquid crystal element may also be used.

  As described above, in the first embodiment, of the two lens arrays of the lens unit, one lens array is 180 degrees with a straight line parallel to the arrangement direction of the microlens as the rotation axis with respect to the other lens array. By rotating the lens array, the distribution of the material characteristics of one lens array and the distribution of the material characteristics of the other lens array are substantially the same, and the difference in shape due to contraction or expansion of the lens array can be suppressed. The effect that the fall of the resolution can be prevented is obtained.

In addition, since the positioning portion of the lens array and the concave portion of the light shielding member are arranged at the approximate center of the lens unit, the displacement between the optical axis of the microlens and the position of the aperture as a diaphragm due to the expansion or contraction of the material is prevented. It is possible to reduce the resolution and to prevent the resolution from being lowered.
As a result, it is possible to obtain a favorable contrast in the image formation of the exposure apparatus and to obtain a clear image with the image forming apparatus.

In the first embodiment, the lens unit according to the present invention has been described as applied to a printer as an image forming apparatus. In the second embodiment, an example in which the lens unit is applied to a reading apparatus will be described.
The configuration of the second embodiment will be described with reference to the schematic diagram showing the configuration of the reading apparatus in the second embodiment of FIG. Note that parts similar to those of the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

In FIG. 14, reference numeral 500 denotes a scanner as a reading device that reads an original and generates electronic data as image data.
The scanner 500 includes a reading head 400, a lamp 501, a document table 502, a rail 503, a driving belt 505, a motor 506, and the like.
The reading head 400 takes in a light beam irradiated by a lamp 501 as an illuminating device and reflected by the surface of the document, and converts it into electronic data. The lamp 501 is arranged so that the irradiated light is reflected by the surface of the document and taken into the reading head 400.

The document table 502 is used to place a document 507 on which electronic data is generated, and is formed of a material that transmits visible light.
The rail 503 is disposed below the document table 502 and allows the reading head 400 to move. The reading head 400 is connected to a driving belt 505 partially stretched by a plurality of pulleys 504, A driving belt 505 driven by a motor 506 is configured to be movable on the rail 503.

Next, the configuration of the reading head 400 will be described based on a schematic diagram showing the configuration of the reading head of the reading apparatus in the second embodiment of FIG.
In FIG. 15, the read head 400 includes the lens unit 1, a line sensor 401, and a mirror 402.
The mirror 402 bends the optical path of the light beam reflected by the document 503 and causes the light beam to enter the lens unit 1.

The line sensor 401 has a plurality of light receiving elements arranged in a straight line at intervals PR, and converts the image of the original image formed by the lens unit 1 into an electrical signal.
FIG. 16 shows the configuration of the reading head 400 of this embodiment and the positional relationship between the object plane OP (original 507) and the imaging plane IP. The configuration of the lens unit 1 of this embodiment is the same as that of the first embodiment.

In this embodiment, the line sensor 401 has a resolution of 600 dpi, and 600 light receiving elements are arranged per inch. That is, the interval PR of the light receiving elements is 0.0423 mm.
The operation of the above configuration will be described.
First, the operation of the reading apparatus will be described with reference to FIG.

When the lamp 501 is turned on and the surface of the original 507 is irradiated, the light beam reflected by the surface of the original 507 is taken into the reading head 400. The driving belt 505 is driven by the motor 506 to move the reading head 400 and the lamp 501 in the left-right direction in FIG. 14, and the reading head 400 takes in the light beam reflected from the entire surface of the document 507.
Next, the operation of the read head 400 will be described with reference to FIG.

The light beam reflected by the original 507 passes through the original table 502, the optical path is bent by the mirror 402, and enters the lens unit 1. The image of the document image formed by the lens unit 1 is formed on the line sensor 401, and the line sensor 401 converts the formed image of the document image into an electrical signal to generate electronic data.
When image data was formed from a document using the reading apparatus according to this embodiment, the same good image data as the document was obtained. Note that a document read using the reading apparatus of this embodiment has a dot interval PD = 0.0423 mm and a resolution of 600 dpi as shown in FIG. In other words, a manuscript was used in which an image in which every other dot was formed on the entire printing area on the medium out of all dots having a spacing of PD = 0.0423 mm and a resolution of 600 dpi.

In this embodiment, a scanner is described as an example of a reading device that converts an original image into electronic data. However, sensors and switches that convert optical signals into electric signals, input / output devices using them, and biological It may be an authentication device, a communication device, a dimension measuring device, or the like.
As described above, in the second embodiment, the same effect as that of the first embodiment can be obtained in the reading apparatus, and the same image data as that of the original can be read.

DESCRIPTION OF SYMBOLS 1 Lens unit 3 LED head 5 Developing device 7 Ejection part 9 Fixing device 10 Lens array 11 Rib 12 Micro lens 13 Positioning part 14 Convex part 20 Light shielding member 21 Rib 22 Opening part 23 Concave part 24 Abutting part 30 LED element 31 Driver IC
32 Wire 33 Wiring board 34 Holder 41 Photosensitive drum 42 Charging roller 43 Cleaning blade 51 Toner cartridge 60 Paper feed cassette 61 Paper feed roller 62, 63, 64 Transport roller 65 Discharge roller 80 Transfer roller 81 Transfer belt

Claims (17)

In a lens array in which a plurality of lens elements are arranged to form a row extending in a direction substantially orthogonal to the optical axis,
A lens array, wherein a positioning portion that engages with a light shielding member is disposed at a substantially center in a direction in which the lens elements are arranged. The lens array of claim 1,
The lens array, wherein the lens elements are integrally formed. An LED head using the lens array according to claim 1. An exposure apparatus using the lens array according to claim 1. An image forming apparatus using the lens array according to claim 1. A reading apparatus using the lens array according to claim 1. A lens unit comprising the lens array according to claim 1 or claim 2 and a light shielding member in which a plurality of stops are arranged,
A plurality of the lens arrays are arranged so that the optical axes of the lens elements coincide with each other,
Between the lens arrays, the light-shielding members in which the respective apertures are arranged to extend in a direction substantially orthogonal to the optical axis so that the optical axes of the respective lens elements pass are disposed. Lens unit characterized by A lens array in which a plurality of lens elements are arranged to form a row extending in a direction substantially orthogonal to the optical axis, and a plurality of stops through which the optical axis passes are substantially orthogonal to the optical axis In a lens unit having a light shielding member arranged to extend in the direction,
A plurality of the lens arrays having substantially the same shape are arranged facing each other so that the optical axes of the lens elements coincide with each other,
A lens unit, wherein one lens array is arranged at a position rotated with respect to another lens array with a straight line parallel to the arrangement direction of the lens elements as a rotation axis. The lens unit according to claim 8, wherein
The lens unit, wherein the lens array is integrally formed. The lens unit according to claim 8 or 9,
2. The lens unit according to claim 1, wherein the lens array is two lens arrays. The lens unit according to claim 8, 9 or 10,
The lens elements are arranged in a staggered pattern so as to form a plurality of rows in a direction perpendicular to the optical axis of the lens elements,
When the arrangement interval in each column of the lens elements is PY and n is an integer other than 0, one lens unit is arranged in parallel with the arrangement direction of the lens elements with respect to the other lens units. / Lens unit characterized by being shifted by two. At least two lenses having a plurality of lens arrays in which a plurality of lens elements are arranged in a staggered manner, one of the lens arrays is inverted, and the optical axes of the respective lens elements are substantially aligned. In a lens unit having an array,
The one lens unit is arranged so as to be shifted in parallel with the arrangement direction of the lens elements with respect to the other lens units, and at least one of the lens elements is arranged not to be used. Lens unit characterized by The lens unit of claim 12,
The lens unit is characterized in that the two lens arrays have a common shape. An LED head using the lens unit according to claim 7. An exposure apparatus using the lens unit according to any one of claims 7 to 13. An image forming apparatus using the lens unit according to claim 7. A reading apparatus using the lens unit according to claim 7.

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