JP7287014B2 - Optical writing device and image forming device - Google Patents

Description

The present invention relates to a lens array, a lens array manufacturing method, an optical writing device, and an image forming apparatus.

A light emitting arrangement type optical writing device used in an electrophotographic image forming apparatus has a light emitting point group and an imaging optical system along the axial direction (hereinafter referred to as "main scanning direction") of a cylindrical photoreceptor. are arranged. A lens array having a plurality of lenses is installed in such an optical writing device.

As a technology related to such a lens array, a configuration in which a light shielding plate is embedded in the lens connecting portion is disclosed. With such a configuration, not only is the positional accuracy high, but there is no air layer at the interface between the lens and the light shielding plate. Therefore, it is possible to eliminate ambient light caused by air (see Patent Document 1 below).

JP-A-4-96042

By the way, for lens arrays, integrally molded resin lenses are often used from the viewpoint of flexibility in processing and manufacturing cost. However, resin has a larger coefficient of linear expansion than glass, and deformation occurs when the environmental temperature changes, and the relative positional relationship between the light source and the lens tends to shift. Also, in the lens array, stray light is likely to occur because the optical paths of adjacent lenses are close to each other. The displacement of these relative positional relationships and the occurrence of stray light are factors that cause deterioration in lens performance.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a lens array whose performance is improved regardless of changes in environmental temperature. Another object of the present invention is to provide a method for manufacturing this lens array, and an optical writing device and an image forming apparatus using this lens array.

To achieve these objects, the present invention provides a lens array in which a plurality of lenses are arranged two-dimensionally, comprising: a glass substrate; a light-shielding layer provided, a resin lens layer provided on one main surface of the glass substrate provided with the light-shielding layer and having lens portions arranged corresponding to the respective light ray passage openings, and the glass substrate. and a back resin layer provided on the other main surface. The present invention also provides a method for manufacturing this lens array, an optical writing device and an image forming apparatus using this lens array.

According to the present invention, it is possible to provide a lens array whose performance is improved regardless of changes in environmental temperature. Further, according to the present invention, it is possible to manufacture this lens array and to provide an optical writing device and an image forming device using this lens array.

It is a top view of a lens array of a 1st embodiment. It is a sectional view of a lens array of a 1st embodiment. It is a cross-sectional process drawing which shows the manufacturing method of the lens array of 1st Embodiment. 1 is a diagram for explaining the overall configuration of an image forming apparatus having a lens array; FIG. 1 is a schematic cross-sectional view showing an optical writing device having a lens array; FIG. FIG. 4 is a plan view of a light emitting point group provided in the optical writing device; FIG. 2 is a schematic plan view of an optical writing device having a lens array as viewed from the photoreceptor side; It is a sectional view of a lens array of a 2nd embodiment. It is a sectional view of a lens array of a 3rd embodiment. It is a sectional view of a lens array of a 4th embodiment. It is a top view of the lens array of 5th Embodiment. It is a top view of the lens array of 6th Embodiment. FIG. 4 is a schematic cross-sectional view showing another example of an optical writing device having a lens array;

<<First embodiment>>
A first embodiment according to the present invention will be described below in the order of the configuration of the lens array, the method of manufacturing the lens array, the image forming apparatus provided with the lens array, and the optical writing apparatus provided with the lens array. An image forming apparatus having a lens array is an image forming apparatus having an optical writing device having a lens array.

<Lens array>
FIG. 1 is a plan view of the lens array of the first embodiment. FIG. 2 is a cross-sectional view of the lens array of the first embodiment, which corresponds to the AA cross-sectional view of FIG. The lens array 1 shown in these figures has a plurality of lenses 201 arranged two-dimensionally. Such a lens array 1 includes a glass substrate 1001 , a light shielding layer 1002 provided on one main surface of the glass substrate 1001 , and a resin lens layer 1003 . The lens array 1 also includes a back surface resin layer 1004 provided on the other principal surface side of the glass substrate 1001 . They are structured as follows.

[Glass substrate 1001]
The glass substrate 1001 is made of a glass material having good light transmittance. In particular, the glass substrate 1001 is made of a material having a small refractive index difference with respect to the light of a specific wavelength with which the lens array 1 is irradiated, from the resin material forming the resin lens layer 1003 and the back surface resin layer 1004, which will be described later. It is important that

By reducing the refractive index difference between the glass substrate 1001 and the resin lens layer 1003 and the back resin layer 1004 in this way, reflection of light at the interface between the glass substrate 1001 and the resin lens layer 1003 and the back resin layer 1004 is suppressed. be done. Therefore, it is possible to prevent reflected light from being emitted from the lens array 1 .

A preferable example of the refractive index difference between the glass substrate 1001 and the resin lens layer 1003 and the back resin layer 1004 is 0.1 or less. By setting the refractive index difference to 0.1 or less, the reflectance at the interface between the glass substrate 1001 and the resin lens layer 1003 and the back resin layer 1004 can be suppressed to 0.01% or less. In this case, even if this lens array 1 is installed in an optical writing device of an image forming apparatus, which will be described later, the light reflected at the interface between the glass substrate 1001 and the resin lens layer 1003 will not reach the photosensitive member of the optical writing device. You can prevent it from affecting you.

As described above, examples of the glass material capable of suppressing the difference in refractive index from the resin material forming the resin lens layer 1003 and the back resin layer 1004 include non-alkali glass (refractive index: 1.5145, specific wavelength: 650 nm). ) can be exemplified.

[Light shielding layer 1002]
The light-shielding layer 1002 is a layer provided on one main surface of the glass substrate 1001 and is made of a material (black material) that has a high light-shielding property against light of a specific wavelength with which the lens array 1 is irradiated. The light shielding layer 1002 has a plurality of light ray passage openings 1002a corresponding to the lenses 201 of the lens array 1. As shown in FIG.

Each ray passage opening 1002a preferably has a shape that matches the effective lens region 1003b in the lens portion 1003a of the resin lens layer 1003, which will be described below. Each such ray passage opening 1002a may have, for example, a circular shape in a plan view. In order to suppress the thickness of the entire lens array 1, the light shielding layer 1002 is preferably a thin film as long as the light shielding property is not impaired.

[Resin lens layer 1003]
The resin lens layer 1003 is a layer made of a resin material provided on one main surface of the glass substrate 1001 with the light shielding layer 1002 interposed therebetween, and has a plurality of lens portions 1003a forming the lenses 201 . Each lens portion 1003a has, for example, a convex lens shape.

An effective lens region 1003b occupying the center of each lens portion 1003a has a planar shape similar to that of the ray passage aperture 1002a of the light shielding layer 1002, and is arranged so as to overlap the ray passage aperture 1002a in plan view. It is assumed that As a result, the peripheral edge of each lens portion 1003a becomes a region outside the effective lens region 1003b, and this outside region serves as a laminated portion [d] laminated on the outer peripheral edge of the ray passage opening 1002a of the light shielding layer 1002. Become. By providing such a laminated portion [d], light rays passing through the lens 201 can be limited to light rays passing through the effective lens region 1003b of the lens portion 1003a. Even if the peripheral edge of the lens portion 1003a made of resin, that is, the surface shape of the area outside the effective lens area 1003b deviates from the design value, the peripheral surface shape of each lens 201 can be prevented from affecting the optical performance of

The resin lens layer 1003 is made of a material having a small difference in refractive index from the above-described glass substrate 1001 with respect to light of a specific wavelength with which the lens array 1 is irradiated. Such a resin lens layer 1003 is made of, for example, a cycloolefin polymer when the glass substrate 1001 is made of non-alkali glass. The cycloolefin polymer is preferably composed of, for example, ZEONEX E48R (trade name manufactured by Nippon Zeon Co., Ltd.: refractive index: 1.5285, specific wavelength: 650 nm). In this case, the refractive index difference between the glass substrate 1001 and the resin lens layer 1003 is 0.014, which is 0.1 or less, which is the preferable refractive index difference between the glass substrate 1001 and the resin lens layer 1003 .

The curvature of each lens portion 1003a has a size determined by the lens design of each lens 201, and may be the same among the lens portions 1003a, but need not be the same.

Further, it is preferable that the film thickness [t] of the flat portion between the lens portions 1003a in the resin lens layer 1003 is thin. In the resin lens layer 1003, when the film thickness [t] of the flat portion having no refractive power is increased, the light rays irradiated to the lens array 1 are projected onto the resin lens layer 1003 between the lens portions 1003a and 1003a. The risk of slipping through the portion and reaching the adjacent lens portion 1003a increases. Therefore, the film thickness [t] of the flat portion of the resin lens layer 1003 is preferably set to 0.3 mm or less, which makes it possible to reduce the risk described above.

[Back surface resin layer 1004]
The back surface resin layer 1004 is a layer made of a resin material provided on the other main surface side of the glass substrate 1001 . This back surface resin layer 1004 is a layer for preventing the glass substrate 1001 from warping due to the provision of the resin lens layer 1003 made of a resin material on one main surface of the glass substrate 1001 . Like the resin lens layer 1003, such a back surface resin layer 1004 is made of a material having a small difference in refractive index from the glass substrate 1001 with respect to light of a specific wavelength with which the lens array 1 is irradiated. be done.

The resin material forming the back surface resin layer 1004 does not need to be the same as the resin material forming the resin lens layer 1003, but is preferably the same. Since the coefficients of linear expansion of the resin materials provided on both sides of the glass substrate 1001 are the same, the effect of preventing the warpage of the glass substrate 1001 due to changes in environmental temperature is high.

Further, the back surface resin layer 1004 may have a plurality of lens portions 1004a that constitute the lens 201 together with the lens portions 1003a that the resin lens layer 1003 has. Each lens portion 1004a has a 1:1:1 correspondence with the light passing aperture 1002a of the light shielding layer 1002 and the lens portion 1003a of the resin lens layer 1003, and the center of the light passing aperture 1002a and the center of the lens portion 1004a correspond to each other. are almost the same.

In this case, each lens portion 1004a is assumed to have, for example, a convex lens shape. As a result, the lens 201 composed of the lens portion 1003a of the resin lens layer 1003 and the lens portion 1004a of the back resin layer 1004 becomes a double-sided convex lens. Since the lens 201 is a biconvex lens, the lens array 1 can distribute the refractive power of the lens 201 to both surfaces, thereby suppressing the occurrence of aberrations and reducing the difficulty of processing. ing. In addition, since the rear surface resin layer 1004 and the resin lens layer 1003 having the same shape can be arranged on both sides of the glass substrate 1001, it is highly effective in preventing the glass substrate 1001 from warping due to changes in environmental temperature.

The curvature of each lens portion 1004a has a size determined by the lens design of each lens 201, and may be the same among the lens portions 1004a, but need not be the same.

<Method for Manufacturing Lens Array 1 of First Embodiment>
3A to 3C are cross-sectional process diagrams showing the method of manufacturing the lens array of the first embodiment, and are diagrams showing an example of the method of manufacturing the lens array 1 described with reference to FIGS. 1 and 2. FIG. Hereinafter, the method for manufacturing the lens array 1 will be described in the order shown in FIG.

First, as shown in FIG. 3A, a glass substrate 1001 is prepared, and on one main surface of the glass substrate 1001, a light shielding layer 1002 having a plurality of ray passage openings 1002a is formed. At this time, a light shielding layer 1002 having a plurality of light beam passage openings 1002a is formed by, for example, black material coating or ceramic printing. Further, the formation of the light shielding layer 1002 is, for example, a procedure of forming a light shielding layer material film on one main surface of the glass substrate 1001, and then forming the light beam passage apertures 1002a in the light shielding layer material film by etching. good too.

Next, as shown in FIG. 3B, a glass substrate 1001 having a light shielding layer 1002 formed thereon is sandwiched between two main surfaces by a mold 2000 . A mold 2000 is assumed to have a lens-shaped cavity 2001 . Next, as shown in FIG. 3C, a resin 2002 is injected into the cavity 2001 of the mold 2000, and the injected resin 2002 is cured. As the resin 2002, for example, a photocurable resin or a thermoplastic resin is used, and the resin is cured by a method suitable for each. As a result, a resin lens layer 1003 is formed on one main surface of the glass substrate 1001 by curing the resin 2002 while covering the light shielding layer 1002 . On the other main surface of the glass substrate 1001, a back surface resin layer 1004 is formed by curing the resin 2002. As shown in FIG.

After curing the resin 2002 , the mold 2000 is removed from the glass substrate 1001 . After that, for example, if it is a photocurable resin, the resin 2002 is further cured by light irradiation. Thereby, the lens array 1 described with reference to FIGS. 1 and 2 can be obtained.

<Effect of Lens Array of First Embodiment>
The lens array 1 having the configuration described above has a configuration in which a resin lens layer 1003 is provided on one main surface of a glass substrate 1001 and a rear resin layer 1004 is provided on the other main surface. As a result, while the lens portion 1003a is made of resin and has a high degree of freedom in design, the positional deviation of the lens portions 1003a and 1004a due to changes in the environment can be suppressed by the glass substrate 1001, making it possible to achieve the same degree as a glass lens. Moreover, between the resin lens layer 1003 and the glass substrate 1001, a light shielding layer 1002 having a light beam passage opening 1002a coinciding with the lens portion 1003a is provided. Therefore, the lens portion 1003a and the light beam passing aperture 1002a are not misaligned due to changes in the environment, and the light passing through the lens 201 formed by the lens portions 1003a is transmitted at a position near the lens surface of the lens portion 1003a. Certain limits are possible. As a result, it is possible to prevent stray light from occurring between adjacent lenses 201 . As a result, with this configuration, it is possible to improve the optical reliability of the lens array 1 against environmental changes.

<Configuration of Image Forming Apparatus>
Next, the configuration of an image forming apparatus having the lens array 1 described above will be described. FIG. 4 is a diagram for explaining the overall configuration of the image forming apparatus provided with the lens array of the first embodiment described above, and is a configuration diagram of the image forming apparatus 10 viewed from the front (front). . An image forming apparatus 10 shown in this figure has an optical writing device having a lens array according to each of the first embodiments. Such an image forming apparatus 10 has a housing 11 and includes an image forming section 20 , a transfer section 30 , a fixing section 40 , a paper feeding section 50 and a paper conveying section 60 inside. The configuration of each of these elements is as follows.

[Image forming unit 20]
The image forming section 20 has four image forming units 20y, 20m, 20c, and 20k for forming toner images of, for example, yellow (Y), magenta (M), cyan (C), and black (K). Each of the image forming units 20y, 20m, 20c, and 20k includes a photoreceptor 21, a charging device 22 arranged around the photoreceptor 21, an optical writing device 23, and a developing device 24, respectively.

Each photoreceptor 21 is cylindrical and is rotated around a cylindrical rotating shaft 21φ by a drive motor, and the cylindrical side peripheral surface serves as an image bearing surface 21a. Such a photoreceptor 21 is arranged in contact with an intermediate transfer belt 31 of a transfer section 30 which will be described below. The charging device 22 , the optical writing device 23 , and the developing device 24 are arranged in such a manner that the charging device 22 , the optical writing device 24 , and the optical writing device 24 move downstream from the contact position between the photoreceptor 21 and the transfer unit 30 in the rotation direction of the photoreceptor 21 . The device 23 and the developing device 24 are arranged in this order.

The charging device 22 is for charging the image bearing surface 21a of the photosensitive member 21 by corona discharge.

The optical writing device 23 has the lens array of the first embodiment described above, and irradiates the image bearing surface 21a of the photoreceptor 21 with a laser beam based on the image data to generate an electrostatic latent image. A writer that forms an image. The image data is data generated by an image reading unit (not shown) provided in the image forming apparatus 10, or data received from an external device such as a personal computer connected to the image forming apparatus 10 or another image forming apparatus. It is assumed that A detailed configuration of such an optical writing device 23 will be described later.

The developing device 24 is for causing the stirred and charged toner to adhere to the image bearing surface 21 a of the photoreceptor 21 . Between the contact position between the photoreceptor 21 and the transfer unit 30 and the location where the charging device 22 is arranged, there is a cleaner (not shown) in contact with the image bearing surface of the photoreceptor 21 . It is arranged to remove toner remaining on the image bearing surface 21 a of the photoreceptor 21 .

[Transfer section 30]
The transfer section 30 is arranged in parallel with the image forming section 20 . The transfer section 30 includes an intermediate transfer belt 31 , a primary transfer roller 32 and a pair of secondary transfer rollers 33 .

Among them, the intermediate transfer belt 31 is configured as a rotating endless belt, and its outer peripheral surface serves as an image bearing surface 31a. The intermediate transfer belt 31 rotates in a direction opposite to the rotation of each photoreceptor 21, and is arranged in such a manner that the image bearing surface 31a is brought into contact with all of the photoreceptors 21 sequentially.

The primary transfer roller 32 is applied with a voltage having a polarity opposite to that of the toner, and is arranged in a state in which the intermediate transfer belt 31 is sandwiched between the primary transfer roller 32 and each photoreceptor 21 . As a result, the toner adhering to the image bearing surface 21a of the photoreceptor 21 is transferred to the image bearing surface 31a of the intermediate transfer belt 31, and a color toner image in which the toner images of the respective colors are superimposed on the image bearing surface 31a of the intermediate transfer belt 31 is transferred. An image is formed.

A pair of secondary transfer rollers 33 are arranged to sandwich the intermediate transfer belt 31, and the toner image formed on the image bearing surface 31a of the intermediate transfer belt 31 is conveyed from the paper supply section 50 described below. is transferred onto a sheet-shaped recording medium S.

[Fixing unit 40]
The fixing unit 40 includes a heating unit 41 and a pressing roller 42 facing the heating unit 41, nips the recording medium S conveyed from the secondary transfer roller 33, and transfers toner onto the recording medium S. The image is fixed on the recording medium S.

[Paper supply unit 50]
The paper supply unit 50 includes a cassette 51 that stores the recording medium S, and a feed roller 52 that feeds out the recording medium S stored in the cassette 51 one by one from the cassette 51 . supply to

[Paper transport unit 60]
The paper conveying section 60 conveys the recording medium S supplied from the paper supplying section 50 along a predetermined route, and is composed of a plurality of roller pairs 61 . The paper conveying unit 60 conveys the recording medium S supplied from the paper supplying unit 50 to the secondary transfer roller 33 , the fixing unit 40 , and a tray (not shown) outside the housing 11 in this order. As a result, the recording medium S on which the toner image is formed by the secondary transfer roller 33 is conveyed to the fixing section 40 to fix the toner image on the recording medium S, and the recording medium S with the toner image fixed is transferred outside the housing. transported to a tray.

<Configuration of Optical Writing Device 23>
FIG. 5 is a schematic cross-sectional view showing an optical writing device with a lens array. The optical writing device 23 shown in FIG. 5 and the previous FIG. It is arranged so as to face the image bearing surface 21a formed by a surface.

In the following description of the configuration of the optical writing device 23, at a position where the optical writing device 23 is arranged to face the image bearing surface 21a of the photoreceptor 21, the direction normal to the image bearing surface 21a is , the direction toward the rotation axis 21φ of the photoreceptor 21 is the light incident direction x. A direction perpendicular to the incident direction x and along the rotation axis 21φ of the photosensitive member 21 is defined as a main scanning direction y. The optical writing device 23 is arranged along the main scanning direction y. Further, a direction perpendicular to the incident direction x and the main scanning direction y and along the rotation direction of the photosensitive member 21 is defined as a sub-scanning direction z.

The optical writing device 23 includes a light emitting element substrate 100, a light shielding body 150, a first lens array 200, an aperture substrate 300, and a second lens in order from the far side from the image bearing surface 21a along the light incident direction x. An array 400 is arranged. A window substrate 500 for preventing contamination is arranged between the second lens array 400 and the image carrying surface 21a. As at least one of the first lens array 200 and the second lens array 400, the lens array 1 of the first embodiment described above is used. Here, as an example, the case of using the lens array 1 as the first lens array 200 will be described.

The light emitting element substrate 100, the light blocking member 150, the first lens array 200, the aperture substrate 300, the second lens array 400, and the window substrate 500 are arranged to face the image bearing surface 21a, and are arranged to face the incident direction x. It is perpendicular and parallel to the main scanning direction y and the sub-scanning direction z.

Among them, the light emitting element substrate 100 is provided with a plurality of light emitting point groups 101 along the substrate surface. The light shielding body 150 is provided with a plurality of light shielding openings 151 along its substrate surface. The first lens array 200 is provided with a plurality of first lenses 201 along the substrate surface. Furthermore, the diaphragm substrate 300 is provided with a plurality of diaphragm apertures 301 along the substrate surface. The second lens array 400 is provided with a plurality of second lenses 401 along the substrate surface.

A first lens 201, a light blocking aperture 151, a diaphragm aperture 301, and a second lens 401 are centered on an optical axis [xφ] extending from the center of one light emitting point group 101 along the incident direction x. are arranged in order of 1:1:1:1, and these constitute one writing optical system 23a. Further, in each writing optical system 23a, the first lens 201, the diaphragm aperture 301, and the second lens 401 constitute one imaging optical system 23b.

The details of the light-emitting element substrate 100, the light blocking member 150, the first lens array 200, the diaphragm substrate 300, and the second lens array 400 that constitute the optical writing device 23 will be described below.

[Light emitting element substrate 100]
A light-emitting element substrate 100 is provided with a plurality of light-emitting point groups 101 along the substrate surface. Each light emitting point group 101 is a light emitting element provided two-dimensionally along the substrate surface of the light emitting element substrate 100 .

FIG. 6 is a plan view of the light emitting point group 101 provided in the optical writing device. As shown in this figure, each luminous point group 101 has a configuration in which a plurality of luminous points 102 are arranged in a rectangular region that is long in the main scanning direction y and short in the sub-scanning direction z, for example. Each light emitting point 102 is composed of, for example, an LED (light emitting diode) or an OLED (Organic Light Emitting Diode).

Returning to FIG. 5, in the light emitting element substrate 100, each light emitting point group 101 is a bottom emission type OLED covered with a transparent substrate material such as a silicon oxide substrate. As a result, the light emitting surface 101a of each light emitting point group 101 is located on the surface of the light emitting element substrate 100 and deeper than the light exit surface 100a. However, all the center points of the light emitting point group 101 exist on substantially the same plane. The angle between the plane on which the center point of the light emitting point group 101 exists and the plane perpendicular to the optical axis [xφ] (incident direction x) of the light emitted from the light emitting point group 101 is 0 degree.

[Light shielding body 150]
The light shielding body 150 is, for example, a plate-shaped member with a plurality of light shielding openings 151 formed therein. The light shielding body 150 allows the light emitted from each light emitting point group 101 of the light emitting element substrate 100 to reach the wide surface of the first lens 201 corresponding to each light emitting point group 101 at 1:1, 1 lens 201 is configured so as not to be irradiated. Such a light blocking body 150 has a sufficient height in the incident direction x to fill the space between the light emitting element substrate 100 and the first lens array 200 , and blocks light between the first lenses 201 .

[First lens array 200]
The first lens array 200 is the lens array 1 of the first embodiment. The lens array 1 is arranged with the surface provided with the light shielding layer 1002 facing the diaphragm substrate 300 side. Each lens 201 provided in the lens array 1 is the first lens 201 in the optical writing device 23 . Each first lens 201 corresponds to each light emitting point group 101 of the light emitting element substrate 100 at 1:1, and the center point of the light emitting point group 101 and the center of the lens 201 are arranged on the optical axis [xφ]. It is assumed that

In addition, each first lens 201 preferably has the same core thickness, which is the film thickness at the center. The angle formed with a plane perpendicular to [xφ] (incident direction x) is 0 degrees. Further, in each first lens 201, the distance [d1] between the light emitting surface 101a of the light emitting point group 101 and the incident surface 202 of the light from the light emitting point group 101 is the same.

[Aperture substrate 300]
A diaphragm substrate 300 is provided with a plurality of diaphragm openings 301 along its substrate surface. Each diaphragm opening 301 is an opening provided in a light shielding film. The light shielding film may be formed on one main surface of a transparent substrate such as glass. All diaphragm apertures 301 provided on the diaphragm substrate 300 have the same aperture shape.

The center point of each diaphragm opening 301 exists on substantially the same plane, and the angle between the plane on which the center point of each diaphragm opening 301 exists and the plane perpendicular to the optical axis [xφ] (incident direction x) is 0 degree. is.

Such an aperture 301 is arranged between the first lens 201 and the second lens 401 at a position where each imaging optical system 23b is telecentric on both sides. Since each imaging optical system 23b is configured to be telecentric on both sides, even if one or both of the position of the image bearing surface 21a and the light emitting surface 101a of the photoreceptor 21 changes in the optical axis direction, the image bearing surface 21a The imaging position of the light does not change, and it is possible to ensure the accuracy of the imaging position.

[Second lens array 400]
The second lens array 400 has second lenses 401 two-dimensionally provided along the substrate surface of a transparent substrate 4001 . Each of these second lenses 401 is a biconvex lens. Each of such second lenses 401 is formed by forming convex lens portions made of resin on both side surfaces of a transparent substrate 4001 made of, for example, a glass material. By making the second lens 401 a convex lens on both sides, the refractive power of the second lens 401 can be allocated to both the light entrance surface 402 and the light exit surface 403, thereby suppressing the occurrence of aberrations and improving processing. The difficulty level is also reduced. Such a layer configuration of the second lens array 400 may be a configuration in which the light shielding layer 1002 is removed from the lens array 1 which is the first lens array 200 .

Further, each second lens 401 preferably has the same core thickness, and the center of the core thickness is arranged on the same plane. ) and the plane perpendicular to it is 0 degrees.

When the lens array 1 of the first embodiment is used as the second lens array 400, the lens array 1 is arranged with the surface provided with the light shielding layer 1002 facing the aperture substrate 300 side. .

<Effects of Optical Writing Device and Image Forming Apparatus of First Embodiment>
The optical writing device 23 described above has a configuration using, as the first lens array 200, the lens array 1 of the first embodiment in which the generation of stray light between adjacent lenses 201 is prevented. As a result, it is possible to obtain the optical writing device 23 capable of optical writing with little streak unevenness due to light irradiation position shift and density unevenness due to ghost rays. Further, according to the image forming apparatus 10 having such an optical writing device 23, it is possible to improve the accuracy of image formation.

<Writing optical system 23a>
Next, a preferred configuration of the writing optical system 23a that constitutes the optical writing device 23 will be described. The writing optical system 23 a is composed of one light emitting point group 101 , a first lens 201 , a diaphragm aperture 301 and a second lens 401 . All the writing optical systems 23a have parallel optical axes [xφ].

In each writing optical system 23a, the first lens 201, aperture 301, and second lens 401 constitute one imaging optical system 23b. These imaging optical systems 23b are for forming images on the image bearing surface 21a of the photoreceptor 21 with the light from the correspondingly arranged light emitting point group 101. The light from the light emitting point group 101 is imaged at each different position of . Each of such imaging optical systems 23b is configured to be telecentric on both sides and configured to have the same imaging magnification.

The imaging magnification of each imaging optical system 23b is [-1] times, and the second lens 401 and the first lens 201 have symmetrical shapes with respect to the diaphragm aperture 301 as will be described later. may be This makes it possible to share the optical design of the first lens 201 and the second lens 401 .

FIG. 7 is a schematic plan view of the optical writing device provided with the lens array as seen from the photoreceptor side. As shown in this figure, the optical writing device 23 has a plurality of writing lines [L] in which a plurality of writing optical systems 23a are arranged along the main scanning direction y. Here, as an example, it is assumed that there are three writing lines [L] in which a plurality of writing optical systems 23a are arranged at predetermined intervals along the main scanning direction y. 5 corresponds to the A-A' section in FIG.

The writing optical system 23a arranged in each writing row [L] overlaps in the main scanning direction y with respect to the writing optical system 23a arranged in another writing row [L] at a predetermined pitch. They are staggered. As a result, the resolution of the electrostatic latent image written on the image bearing surface 21a of the photosensitive member 21 by the writing optical system 23a of each writing line [L] is ensured.

As shown in FIGS. 5 and 7, one of these writing columns [L] is aligned with the normal to the image bearing surface 21a of the photoreceptor 21 and the optical axis [xφ] of the writing optical system 23a. is the matching central column [Lφ]. The remaining two of the writing columns [L] are upstream columns [L− ], and a downstream row [L+] located downstream of the central row [Lφ] in the rotational direction of the image bearing surface 21a and in the sub-scanning direction z. These upstream row [L-] and downstream row [L+] are arranged at regular intervals with respect to the central row [Lφ].

Image points [Pφ], [P−], [P+] on the image bearing surface 21a of the cylindrical photoreceptor 21 in the respective writing optical systems 23a arranged in this manner. are different in height in the optical axis [xφ] direction. That is, the image point [Pφ] on the image bearing surface 21a in the writing optical system 23aφ of the central row [Lφ] and the image point on the image bearing surface 21a in the writing optical system 23a− of the upstream row [L−] [P-] and the image point [P+] on the image bearing surface 21a in the writing optical system 23a+ of the downstream row [L+] are not on the same plane.

Among the three image points [Pφ], [P-], [P+], the center where the normal to the image bearing surface 21a of the photosensitive member 21 and the optical axis [xφ] of the writing optical system 23a coincide The image point [Pφ] of the writing optical system 23aφ in the row [Lφ] is located closer to the light emitting element substrate 100 side than the other two image points [P−] and [P+].

Also, the center of each second lens 401 is arranged on the same plane perpendicular to the incident direction x. Therefore, the conjugate length of the writing optical system 23aφ of the central row [Lφ] is longer than the conjugate length of the writing optical system 23a− of the upstream row [L−] and the writing optical system 23a+ of the downstream row [L+]. is also short.

Among the writing optical systems 23a arranged in this manner, the writing optical system 23aφ arranged in the central row [Lφ], the writing optical system 23a− arranged in the upstream row [L−] and the downstream optical system 23a− The writing optical system 23a+ arranged in the side row [L+] preferably has a configuration in which the shapes of the first lens 201 and the second lens 401 are different, as described below.

The first lens 201 may have a different curvature ratio between the light incident surface 202 and the light exit surface 203, for example, for each writing row [L]. Here, the curvature of the incident surface 202 with respect to the curvature of the exit surface 203 in the first lens 201 is defined as a first curvature ratio [R1].

In this case, the first curvature ratio [R1φ] of the first lens 201φ forming the central row [Lφ] is the first curvature ratio [R1−] of the first lens 201− forming the upstream row [L−] and It is different from the first curvature ratio [R1+] of the first lens 201+ forming the downstream row [L+]. Specifically, the closer the position of the image bearing surface 21a in the optical axis [xφ] direction of the imaging optical system 23b is to the light emitting element substrate 100 side, the smaller the first curvature ratio [R1] of the first lens 201. First curvature ratio [R1φ]<first curvature ratios [R1−], [R1+].

That is, the first curvature ratio [R1φ] of the first lens 201φ in the central row [Lφ] whose image point [Pφ] is close to the light emitting point group 101 and has a short conjugate length is It is smaller than the first curvature ratio [R1−] of the first lens 201− and the first curvature ratio [R1+] of the first lens 201+ in the downstream row [L+]. Also, the first curvature ratio [R1-] of the first lens 201- in the upstream row [L-] is equal to the first curvature ratio [R1+] of the first lens 201+ in the downstream row [L+].

In each of the first lenses 201 as described above, the light [hφ] passing through the first lenses 201φ of the central row [Lφ] becomes parallel light or convergent light, and the upstream row [L−] and the downstream row It is assumed that the [L+] first lenses 201-, 201+ are arranged so that the light [h-], [h+] passing through the first lenses 201-, 201+ becomes divergent light. However, the light [hφ] that passed through the first lens 201φ of the central row [Lφ] became convergent light, and passed through the first lenses 201- and 201+ of the upstream row [L-] and downstream row [L+]. The light [h−] and [h+] may be arranged so as to be parallel light or divergent light.

Each second lens 401 has different distances [d2φ], [d2−], [d2+] between the exit surface 403 and the image points [Pφ], [P−], [P+] on the image bearing surface 21a. It is. That is, the distance [d2φ] between the exit surface 403 of the second lens 401φ in the central row [Lφ] and the image point [Pφ] is the distance [d2φ] between the exit surface 403 and the image point [Pφ] of the second lens 401− in the upstream row [L−]. [P-] and the distance [d2+] between the exit surface 403 of the second lens 401+ in the downstream row [L+] and the image point [P+]. Also, the distance [d2-] of the upstream row [L-] is equal to the distance [d2+] of the downstream row [L+].

In the writing optical system 23aφ in the central column [Lφ], the distance [d2φ] is set to be the distance [d1]. In this case, if the distance [d2φ]<distance [d1], the light [hφ] passing through the first lens 201φ becomes convergent light. As a result, the imaging position of the light that has passed through the second lens 401φ moves toward the second lens 401φ, the conjugate length becomes shorter, and the image point [Pφ] is positioned on the image bearing surface 21a at a closer position. It is configured to be able to form an image. If the image point [Pφ] can be formed on the image bearing surface 21a, the distance [d2φ] may be equal to the distance [d1]. become light.

Further, in the writing optical system 23a− of the upstream side row [L−] and the writing optical system 23a+ of the downstream side row [L+], the distances [d2−], [d2+]>distance [d1] are set. . In this case, the lights [h-] and [h+] that have passed through the first lenses 201- and 201+ become diverging lights. As a result, the imaging position of the light that has passed through the second lenses 401- and 401+ moves away from the second lenses 401- and 401+, the conjugate length increases, and the image is formed on the image bearing surface 21a at a farther position. The configuration is such that the point [P−][P] can be imaged.

The second lens 401 as described above is arranged symmetrically with the first lens 201 with respect to the diaphragm aperture 301 in each imaging optical system 23b, and has a symmetrical shape. ], the curvature ratios of the entrance surface 402 and the exit surface 403 are different. Here, contrary to the definition of the first lens 201, the curvature of the exit surface 403 with respect to the curvature of the entrance surface 402 of the second lens 401 is defined as a second curvature ratio [R2].

In this case, the second curvature ratio [R2φ] of the second lens 401φ forming the central row [Lφ] is the second curvature ratio [R2−] of the second lens 401− forming the upstream row [L−] and It is different from the second curvature ratio [R2+] of the second lens 401+ forming the downstream row [L+]. Specifically, the closer the position of the image bearing surface 21a in the optical axis [xφ] direction of the imaging optical system 23b is to the light emitting element substrate 100 side, the smaller the second curvature ratio [R2] of the second lens 401. Second curvature ratio [R2φ]<first curvature ratios [R2−], [R2+].

That is, the second curvature ratio [R2φ] of the second lens 401φ in the central row [Lφ], which has a short conjugate length and whose image point [Pφ] is close to the light emitting point group 101 side, corresponds to the second curvature ratio [R2φ] of the upstream row [L− ] and the second curvature ratio [R2+] of the second lens 401+ in the downstream row [L+]. Also, the second curvature ratio [R2-] of the second lens 401- in the upstream row [L-] is equal to the second curvature ratio [R2+] of the second lens 401+ in the downstream row [L+].

Also, in such a central row [Lφ], the second curvature ratio [R2φ]=the first curvature ratio [R1φ]. Further, in the upstream side row [L-] and the downstream side row [L+], the second curvature ratios [R2-], [R2+] = the first curvature ratios [R1-], [R1+].

[Specific example of optical writing device 23]
Next, a specific example of the optical writing device 23 described above will be shown. Table 1 below shows the coordinate data of the writing optical system 23aφ in the central column [Lφ] of the writing optical system 23a in the optical writing device 23 of the first embodiment. Table 2 below shows the coordinate data of the writing optical system 23a- in the upstream row [L-] among the writing optical systems 23a in the optical writing device 23 of the first embodiment. Note that the coordinate data of the downstream side row [L+] may have the same incident direction x as the coordinate data of the upstream side row [L−], and the signs of the main scanning direction y and the sub-scanning direction z may be reversed. omitted.

The coordinate data shown in Tables 1 and 2 below are obtained by setting the center position [O] of the light emitting surface 101a of the light emitting point group 101 provided in the central row [Lφ] to the incident direction x=0, the main scanning direction y=0, This is coordinate data with the sub-scanning direction z=0. Regarding the incident surface 202 and the exit surface 203 of the first lens 201, the stop aperture 301, and the entrance surface 402 and the exit surface 403 of the second lens 401, respective center values are shown. Further, for each substrate, the center coordinates of the writing optical system 23aφ in the central row [Lφ] were commonly used. Further, the coordinate data of the photoreceptor 21 are the coordinate data at the image points [Pφ] and [P−] on the image bearing surface 21a of the photoreceptor 21 . This photosensitive member 21 is cylindrical with a radius of 22 mm.

In Table 1, the entrance surface 202 and the exit surface 203 of the first lens 201φ, the aperture 301, the entrance surface 402 and the exit surface 403 of the second lens 401φ have the same values in the main scanning direction y and the sub-scanning direction z. , are aligned along the incident direction x.

Further, in Table 2, the values of the entrance surface 202 and the exit surface 203 of the first lens 201-, the aperture 301, the entrance surface 402 and the exit surface 403 of the second lens 401- in the main scanning direction y and the sub-scanning direction z are It can be seen that they are identical and they are arranged in a straight line along the direction of incidence x.

The angle between the first lens 201, aperture 301, second lens 401, and the substrate on which these are provided and the plane perpendicular to the optical axis [xφ] (incident direction x) is 0 degree. Further, the photoreceptor 21 is cylindrical. For this reason, comparing Tables 1 and 2, it can be seen that the incident direction x of the image bearing surface 21a is greater in the writing optical system 23aφ in the central row [Lφ] than in the writing optical system 23a in the upstream row [L−]. - is smaller than The angle of the image bearing surface 21a is 0 degree in the writing optical system 23aφ in the central row [Lφ], and is oblique in the writing optical system 23a− in the downstream row [L−].

Tables 3(1) to 3(4) below show the aspherical coefficients of the first lens 201φ and the second lens 401φ that constitute the writing optical system 23aφ in the center row [Lφ]. Tables 4(1) to 4(4) below show the aspherical coefficients of the first lens 201- and the second lens 401- that constitute the writing optical system 23a- of the upstream row [L-]. Note that the data of the writing optical system 23a+ in the downstream row [L+] are omitted because they are common.

The surface shapes of the first lens 201 and the second lens 401 shown here are axially symmetrical aspheric surfaces, and there is no spherical term, and the shape formula is as shown in the following formula (1).

Also, the curvature in this case is the paraxial curvature. In the axially symmetrical aspherical surface, paraxial curvature=2×[secondary aspherical surface coefficient]. In Tables 3 and 4, the second-order aspherical coefficient is the [i=2] aspherical coefficient. The first lens 201 and the second lens 401 are configured by providing convex lens portions made of resin with a refractive index of 1.5285 on both main surfaces of a glass substrate with a refractive index of 1.5145. Further, the imaging magnification of each writing optical system 23a configured using the first lens 201 and the second lens 401 is [-1] times.

Table 5 below shows the first curvature ratio [R1φ] for the first lens 201φ and the second curvature ratio [R2φ] for the second lens 401φ in the center row [Lφ] shown in Table 3 above. Also shown are the first curvature ratio [R1-] for the first lens 201- and the second curvature ratio [R2-] for the second lens 401- in the upstream row [L-] shown in Table 4 above. Note that the first curvature ratio [R1] and the second curvature ratio [R2] are shown as absolute values. Also, the first curvature ratio [R1+] for the first lens 201+ and the second curvature ratio [R2+] for the second lens 401+ of the downstream row [L+] are the same as the values of the upstream row [L−]. omitted.

As shown in Table 5, the first curvature ratio [R1φ] of the central row [Lφ] whose image point [Pφ] is close to the light emitting point group 101 and has a short conjugate length is It is smaller than the first curvature ratio [R1−]. Similarly, the second curvature ratio [R2φ] of the central row [Lφ] is smaller than the second curvature ratio [R2-] of the upstream row [L-].

Further, as shown in the coordinate data of Table 1, in the central row [Lφ], the distance [d1] between the light emitting surface 101a and the incident surface 202 of the first lens 201φ is [d1]=3.882. The distance [d2φ] between the exit surface 403 of the second lens 401φ and the image point [Pφ] on the image bearing surface 21a is [d2φ]=19.747−16.118=3.629. Therefore, in the center row [Lφ], distance [d1]>distance [d2φ], and the light [hφ] passing through the first lens 201φ is convergent light.

Further, as shown in the coordinate data of Table 2, in the upstream row [L-], the distance [d1] between the light emitting surface 101a and the incident surface 202 of the first lens 201- is [d1]=3.882. is. The distance [d2-] between the exit surface 403 of the second lens 401- and the image point [P-] on the image bearing surface 21a is [d2-]=20.253-16.118=4.135. be. Therefore, in the upstream row [L-], the distance [d1]<the distance [d2-], and the light [h-] passing through the first lens 201- is divergent light.

Furthermore, since the imaging magnification of each writing optical system 23a is [−1] times, as can be seen from the coordinates and aspheric coefficients of the construction data in Tables 1 to 5, the central row [Lφ] and the upstream row [ L-], the first lens 201 and the second lens 401 are arranged symmetrically with respect to the diaphragm aperture 301, have symmetrical surface shapes, and have the configuration shown in the first embodiment.

In the writing optical system 23a shown in such a specific example, each imaging optical system 23b is telecentric on both sides, so that the imaging position accuracy on the image carrying surface 21a is ensured. Moreover, each writing optical system 23a corrects the curvature ratios [R1] and [R2] of the first lens 201 and the second lens 401 according to the height position of the image bearing surface 21a in the direction of the optical axis [xφ]. By adjusting the conjugate length, image points [Pφ], [P−], and [P−] are formed on the image carrying surface 21a. Therefore, it is possible to suppress variation in the amount of exposure at each position on the image bearing surface 21a of the cylindrical photoreceptor 21. FIG. Furthermore, by correcting the curvature ratios [R1] and [R2] of both the first lens 201 and the second lens 401, it is possible to keep the magnification of each imaging optical system 23b uniform.

<<Second embodiment>>
FIG. 8 is a cross-sectional view of the lens array of the second embodiment. The lens array 2 of the second embodiment shown in this figure differs from the lens array of the first embodiment in the shapes of the resin lens layer 1003' and the rear surface resin layer 1004', and other configurations are the same.

That is, the resin lens layer 1003' may have a configuration in which each lens portion 1003a is independently provided in an island shape. When forming such a resin lens layer 1003', for example, an uncured resin is dripped onto each lens portion 1003a and then cured. The shape of each lens portion 1003a is adjusted according to the viscosity of the uncured resin and the dropping amount.

Similarly, the back surface resin layer 1004' may have a configuration in which each lens portion 1004a is independently provided in an island shape. When forming such a back surface resin layer 1004', for example, an uncured resin is dripped onto each lens portion 1004a and then cured. The shape of each lens portion 1004a is adjusted according to the viscosity of the uncured resin and the dropping amount.

The lens array 2 having such a configuration can be installed and used in an optical writing device and an image forming device, like the lens array described in the first embodiment.

According to the lens array 2 of the second embodiment as described above, the positional accuracy of each lens 201 composed of lens portions 1003a and 1004a provided independently on the glass substrate 1001 in the form of islands is determined by the expansion coefficient of the glass substrate 1001. will depend only on Therefore, the lens array 2 of the second embodiment is more effective in suppressing positional deviation of the lens units 1003a due to environmental changes than the lens array 1 of the first embodiment.

In the second embodiment, both the resin lens layer 1003′ and the back surface resin layer 1004′ are island-shaped. may be

<<Third Embodiment>>
FIG. 9 is a cross-sectional view of the lens array of the third embodiment. The lens array 3 of the third embodiment shown in this figure differs from the lens array of the first embodiment in the configuration of the light shielding layer 1002', and other configurations are the same.

That is, the light shielding layer 1002 ′ may be formed in the surface layer on one main surface side of the glass substrate 1001 . Such a light shielding layer 1002' is formed, for example, by altering or dyeing the surface layer of the glass substrate 1001, and the portion of the surface layer of the glass substrate 1001 that is not altered or dyed serves as the ray passage opening 1002a. Such a light shielding layer 1002' is formed by, for example, laser marking, staining, or coloring by light irradiation such as X-rays or ultraviolet rays.

The lens array 3 having such a configuration can be installed and used in an optical writing device and an image forming apparatus, like the lens array described in the first embodiment.

Even with the lens array 3 of the third embodiment as described above, effects similar to those of the lens array of the first embodiment can be obtained. It should be noted that the third embodiment can be combined with the second embodiment, and the effect of the second embodiment can be obtained by combining them.

<<Fourth Embodiment>>
FIG. 10 is a cross-sectional view of the lens array of the fourth embodiment. The lens array 4 of the fourth embodiment shown in this figure differs from the lens array of the first embodiment in that the back surface resin layer 1004'' is a flat film, and the rest of the configuration is the same. , each lens 201 ′ provided in the lens array 4 is a single-sided convex lens consisting only of each lens portion 1003 a of the resin lens layer 1003 .

Even with the lens array 4 of the fourth embodiment as described above, effects similar to those of the lens array of the first embodiment can be obtained. It should be noted that the fourth embodiment can be combined with other embodiments, and the effects of the other embodiments can be obtained by combining them.

<<Fifth Embodiment>>
FIG. 11 is a plan view of the lens array of the fifth embodiment. The lens array 5 of the fifth embodiment shown in this figure differs from the lens array of the first embodiment in the shape of the light ray passing opening 1002a' provided in the light shielding layer 1002, and other configurations are the same.

That is, the ray passage opening 1002a' provided in the light shielding layer 1002 does not have a circular shape in plan view, but an oval shape elongated in one direction. For example, assume that this lens array 5 is provided as the first lens array 200 or the second lens array 400 of the optical writing device 23 described with reference to FIGS. In this case, each light-emitting point group 101 provided on the light-emitting element substrate 100 has a configuration in which a plurality of light-emitting points 102 are arranged in a rectangular area that is long in the main scanning direction y and short in the sub-scanning direction z. Therefore, as shown in FIG. 11, when the lens array 5 is installed in the optical writing device 23, the aperture shape of the light ray passing aperture 1002a' is made to be an elliptical shape elongated in the main scanning direction y.

As a result, in the optical writing device 23 using this lens array 5 as the first lens array 200 or the second lens array 400, the aperture diameter of the light beam passing aperture 1002a' is [size in the main scanning direction y]≧ [size in sub-scanning direction z].

In the lens array 5 of the fifth embodiment, the planar shape of the light-emitting point group 101 of the optical writing device 23 provided with the lens array 5 is matched with the planar shape of the light-ray passing opening 1002a′ provided in the light shielding layer 1002. Configuration. As a result, while allowing the light generated from the corresponding light emitting point group 101 to pass through the ray passing aperture 1002a' without waste, the ray passing aperture 1002a' is limited to the minimum size, and harmful light is transmitted through the lens 201. can be prevented from passing through The fifth embodiment can be combined with other embodiments, and the effects of other embodiments can be obtained by combining them.

<<Sixth embodiment>>
FIG. 12 is a plan view of the lens array of the sixth embodiment. The lens array 6 of the sixth embodiment shown in this figure is a modification of the lens array of the fifth embodiment, and is the first lens array 200 or the second lens array of the optical writing device 23 described with reference to FIGS. It is assumed that a two-lens array 400 is provided. In this lens array 6, the planar shape of the lens portions 1003a' of the resin lens layer 1003 and the lens portions 1004a' of the back resin layer 1004 is different from each of the light emitting point groups 101 and the ray passage openings 1002a provided on the light emitting element substrate 100. ' has an oval shape that is long in one direction.

Even if the lens surfaces of the lens portions 1003a' and 1004a' are axisymmetric aspherical surfaces and are oval in plan view, the lens surfaces are free-form surfaces (that is, YZ surfaces having no axis of rotational symmetry). polynomial surface).

Further, when the lens array 6 is provided in the optical writing device 23, for example, if the distance between the lenses 201'' in the sub-scanning direction z is sufficiently large, the light-shielding layer 1002'' is elongated in the main scanning direction y. It may be separated into a shape. In this case, the space between the separated light shielding layers 1002″ becomes a light ray passage area, but light rays passing through this portion are limited to light rays having a considerable angle with respect to the optical axis [xφ] (see FIG. 5). and does not reach the photoreceptor 21 .

Even in such a sixth embodiment, the same effect as in the fifth embodiment can be obtained. In addition, if the light shielding layer 1002'' is separated, the area of the light shielding material portion of the light shielding layer 1002'' is reduced. Cost can be reduced.

<<Other Examples of Optical Writing Device>>
FIG. 13 is a schematic cross-sectional view showing another example of an optical writing device provided with a lens array, and is a diagram for explaining the seventh embodiment. The optical writing device 23' shown in this figure differs from the optical writing device 23 described in the first embodiment in that the light emitting element substrate 100', the light blocking member 150', the first lens array 200, the diaphragm substrate 300, and the second lens array 400 are arranged. The luminous point group 101, the first lens 201, the diaphragm aperture 301, the second lens 401, and other optical configurations provided therefor are the same as those described in the first embodiment. For example, the relationship between the light emitting point group 101, the first lens 201, the aperture 301, and the second lens 401 in each optical writing device 23' is the same as the relationship shown in the first embodiment.

That is, the optical writing device 23' includes the light emitting element substrate 100', the light blocking member 150', the first lens array 200, the diaphragm substrate 300, and the second lens array 400, and the optical axis [xφ] (incident direction x ) is not 0 degree, but has the following inclination.

[Light emitting element substrate 100']
The light emitting element substrate 100′ has a plurality of light emitting point groups 101 provided two-dimensionally along the substrate surface of the light emitting element substrate 100′. It is provided on a plane that is perpendicular to the direction x and parallel to the main scanning direction y and the sub-scanning direction z.

Moreover, the center points of all the light emitting point groups 101 exist on substantially the same plane. The angle [θ1] formed between the plane 107 on which the center point of the light emitting point group 101 exists and the plane 108 perpendicular to the optical axis [xφ] (incident direction x) is not 0 degrees but has an inclination.

In the light-emitting element substrate 100′ on which such light-emitting point groups 101 are arranged, the light-emitting point groups 101 are provided for each of the central row [Lφ], the upstream row [L−], and the downstream row [L+]. It has a structure in which substrates are provided and these substrates are stacked in the direction of the optical axis [xφ] (incident direction x).

[Light shielding body 150']
The light shielding body 150' allows the light emitted from each light emitting point group 101 of the light emitting element substrate 100' to reach the wide surface of the first lens 201 corresponding to each light emitting point group 101 at 1:1, The first lens 201 is configured so as not to be irradiated. Such a light blocking member 150′ is provided, for example, on the surface of the light emitting element substrate 100′ facing the photoreceptor 21, and has a sufficient height in the incident direction x to fill the space between the light emitting element substrate 100′ and the first lens array 200. and shields the space between the first lenses 201 .

[First lens array 200]
The first lens array 200 is, for example, the lens array 1 of the first embodiment, and is arranged with the light shielding layer 1002 facing the diaphragm substrate 300 side. This lens array 1 has a plurality of first lenses 201 two-dimensionally provided along the substrate surface. Each of these first lenses 201 has a core thickness parallel to the incident direction x and has the same size.

Also, the centers of the core thicknesses of all the first lenses 201 are arranged on the same plane. The angle [θ2] formed between the plane 207 on which the center of the core thickness is arranged and the plane 208 perpendicular to the optical axis [xφ] (incident direction x) has an inclination within the range of angle [θ2] < [θ1]. . Even in this case, the position of the image bearing surface 21a in the optical axis [xφ] direction of the imaging optical system 23b is closer to the light emitting element substrate 100′ side. is the first curvature ratio [R1−] of the first lens 201− forming the upstream row [L−] and the first curvature ratio [R1−] of the first lens 201+ forming the downstream row [L+] Being smaller than 1 curvature ratio [R1+] may be the same as in the first embodiment.

When the lens array 1 of the first embodiment is used as the second lens array 400, the lens array 1 may be arranged with the surface provided with the light shielding layer 1002 facing the aperture substrate 300 side. It is similar to the embodiment.

[Aperture substrate 300]
The diaphragm substrate 300 has a plurality of diaphragm apertures 301 two-dimensionally provided along the substrate surface. These diaphragm openings 301 have their center points on substantially the same plane. The angle [θ3] formed between the plane 307 on which the center point of the diaphragm aperture 301 exists and the plane 308 perpendicular to the optical axis [xφ] (incident direction x) is an angle [θ3] < [θ2]. have.

[Second lens array 400]
The second lens array 400 has second lenses 401 two-dimensionally provided along the substrate surface. Each of these second lenses 401 has a core thickness parallel to the incident direction x and the same size.

Further, the centers of the core thicknesses of all the second lenses 401 are arranged on the same plane. The angle [θ4] formed between the plane 407 on which the center of the core thickness [t2] is arranged and the plane 408 perpendicular to the optical axis [xφ] (incident direction x) is within the range of angle [θ4] < [θ3]. have an inclination. Even in this case, the position of the image bearing surface 21a in the direction of the optical axis [xφ] of the imaging optical system 23b is the second lens 401φ that constitutes the central row [Lφ] closer to the light emitting element substrate 100′ side. is the second curvature ratio [R2−] of the second lens 401− forming the upstream row [L−] and the second curvature ratio [R2−] of the second lens 401+ forming the downstream row [L+] Being smaller than 2 curvature ratio [R2+] is the same as in the first embodiment.

<Specific example of optical writing device 23'>
Next, a specific example of the above-described optical writing device 23' will be shown. Table 6 below shows the coordinate data of the writing optical system 23aφ of the central column [Lφ] in the optical writing device 23' of the second embodiment. Table 7 below shows the coordinate data of the writing optical system 23a- in the upstream row [L-] in the optical writing device 23' of the second embodiment. Further, Table 8 below shows the coordinate data of the writing optical system 23a+ in the downstream row [L+] in the optical writing device 23' of the second embodiment.

The coordinate data shown in Tables 6 to 8 below are obtained by setting the center position [O] of the light emitting surface 101a of the light emitting point group 101 provided in the central row [Lφ] to the incident direction x=0, the main scanning direction y=0, This is coordinate data with the sub-scanning direction z=0. Regarding the incident surface 202 and the exit surface 203 of the first lens 201, the diaphragm 301, and the entrance surface 402 and the exit surface 403 of the second lens 401, respective center values are shown. Further, for the substrate materials of the first lens array 200 and the second lens array 400, the central coordinates of the incident surface side of the writing optical system 23aφ in the central row [Lφ] are commonly used. The coordinates of the exit surface of the substrate material of the first lens array 200 and the second lens array 400 are the coordinates in the normal direction to the entrance surface at the center coordinates on the entrance surface side. Since the light-emitting element substrate 100′ has a configuration in which substrates provided with light-emitting point groups 101 for each of the central row [Lφ], the upstream row [L−], and the downstream row [L+] are stacked, the coordinates are each showing

Further, the coordinate data of the photoreceptor 21 are the coordinate data at the image points [Pφ], [P−], and [P+] on the image bearing surface 21a of the photoreceptor 21 . This photosensitive member 21 is cylindrical (cylindrical) with a radius of 22 mm.

As shown in Tables 6 to 8, each of the writing optical systems 23aφ, 23a−, 23a+ includes the entrance surface 202 and the exit surface 203 of the first lens 201, the diaphragm 301, the entrance surface 402 of the second lens 401 and the exit surface. It can be seen that the values of the main scanning direction y and the sub-scanning direction z of the surface 403 are the same, and they are arranged on a straight line along the incident direction x.

In addition, the angle formed by the first lens 201, the diaphragm 301, the second lens 401, and the substrate on which these are provided with the plane perpendicular to the optical axis [xφ] (incident direction x) is not 0 degrees but has an inclination. ing. Further, the photoreceptor 21 is cylindrical. Therefore, when the coordinates of the image bearing surface 21a in Tables 6 to 8 are compared, with respect to the incident direction x, the writing optical system 23aφ of the central row [Lφ] is the writing optical system 23aφ of the upstream row [L−]. It is smaller than the optical system 23a- and the writing optical system 23a+ of the downstream row [L+]. The angle of the image bearing surface 21a is 0 degrees in the writing optical system 23aφ of the central row [Lφ], and the writing optical system 23a− of the downstream row [L−] and the writing optical system 23a− of the downstream row [L+]. The optical system 23a+ is oblique.

Tables 9 (1) to (4) below show the aspherical coefficients of the first lens 201φ and the second lens 401φ that constitute the writing optical system 23aφ in the center row [Lφ]. Tables 10(1) to 10(4) below show the aspherical coefficients of the first lens 201- and the second lens 401- that constitute the writing optical system 23a- of the upstream row [L-]. Furthermore, Tables 11(1) to 11(4) below show the aspheric coefficients of the first lens 201+ and the second lens 401+ that constitute the writing optical system 23a+ of the downstream row [L+].

The surface shapes of the first lens 201 and the second lens 401 shown here are axisymmetric aspheric surfaces similar to those shown in the first embodiment, and the curvature is paraxial curvature. In the axially symmetrical aspherical surface, paraxial curvature=2×[secondary aspherical surface coefficient]. In Tables 9 to 11, the secondary aspherical coefficient is the aspherical coefficient of i=2. The first lens 201 and the second lens 401 are configured by providing convex lens portions made of resin with a refractive index of 1.5285 on both main surfaces of a glass substrate with a refractive index of 1.5145. Further, the imaging magnification of each writing optical system 23a configured using the first lens 201 and the second lens 401 is [-1] times.

Table 12 below shows the first curvature ratio [R1] for each first lens 201 and the second curvature ratio [R2] for the second lens 401 shown in Tables 9 to 11 above. Note that the first curvature ratio [R1] and the second curvature ratio [R2] are shown as absolute values.

As shown in Table 12, the first curvature ratio [R1φ] of the central row [Lφ] whose image point [Pφ] is close to the light emitting element substrate 100′ and has a short conjugate length is and the first curvature ratio [R1+] of the downstream row [L+]. Similarly, the second curvature ratio [R2φ] of the central row [Lφ] is the second curvature ratio [R2−] of the upstream row [L−] and the second curvature ratio [R2+] of the downstream row [L+] less than

Further, as shown in the coordinate data of Table 6, in the central row [Lφ], the distance [d1φ] between the light emitting surface 101a and the incident surface 202 of the first lens 201φ is [d1φ]=4.257. The distance [d2φ] between the exit surface 403 of the second lens 401φ and the image point [Pφ] on the image bearing surface 21a is [d2φ]=21.247−17.243=4.004. Therefore, in the center row [Lφ], distance [d1φ]>distance [d2φ], and the light [hφ] passing through the first lens 201φ is convergent light.

Further, as shown in the coordinate data of Table 7, in the upstream row [L-], the distance [d1-] between the light emitting surface 101a and the incident surface 202 of the first lens 201- is [d1-]=5 .381-1.500=3.881. The distance [d2-] between the exit surface 403 of the second lens 401- and the image point [P-] on the image bearing surface 21a is [d2-]=21.753-17.619=4.134. be. Therefore, in the upstream row [L-], the distance [d1-]<the distance [d2-], and the light [h-] passing through the first lens 201- is divergent light.

Further, as shown in the coordinate data of Table 8, in the downstream row [L+], the distance [d1+] between the light emitting surface 101a and the incident surface 202 of the first lens 201+ is [d1+]=3.132−( −1.500)=4.632. The distance [d2+] between the exit surface 403 of the second lens 401+ and the image point [P+] on the image bearing surface 21a is [d2+]=21.753-16.868=4.885. Therefore, in the downstream row [L+], distance [d1+]<distance [d2+], and the light [h-] that has passed through the first lens 201+ is divergent light.

Furthermore, since the imaging magnification of each writing optical system 23a is [-1] times, as can be seen from the coordinates and aspheric coefficients of the construction data in Tables 6 to 12, the central row [Lφ] and the upstream row [ L-], and the first lens 201 and the second lens 401 in the downstream row [L+] are arranged symmetrically with respect to the diaphragm 301, and have symmetrical surface shapes, and have the configuration shown in the second embodiment. It belongs to

<Effects of the seventh embodiment>
Even in the optical writing device 23' having such a configuration, the optical writing device 23' according to the first embodiment uses the lens array 1 according to the first embodiment as the first lens array 200 and the second lens array 400. It is possible to obtain the same effect as that of the loading device 23 . Further, as the first lens array 200 and the second lens array 400, it is possible to use any one of the lens arrays of the second to sixth embodiments. effect can be obtained.

Also, in this optical writing device 23', the relationship between the light emitting point group 101, the first lens 201, the diaphragm 301, and the second lens 401 is the same as in the optical writing device of the first embodiment. Therefore, similarly to the optical writing device 23 described in the first embodiment, the image forming position accuracy on the image bearing surface 21a is ensured, and the exposure amount at each position on the image bearing surface 21a of the cylindrical photosensitive member 21 is reduced. can be suppressed, and the magnification of each imaging optical system 23b can be kept uniform. Further, according to the image forming apparatus 10 having the optical writing device 23', it is possible to improve the accuracy of image formation.

1, 2, 3, 4, 5, 6... Lens array 10... Image forming device 21... Photoreceptor 21a... Image carrying surface 23, 23'... Optical writing device 23b... Imaging optical system 100, 100'... Light emitting element Substrate 101 Light emitting point group 102 Light emitting point 200 First lens array 300 Diaphragm substrate 301 Diaphragm aperture 400 Second lens array 1001 Glass substrate 1002 Light shielding layer 1002a, 1002a' Ray passing aperture 1003 Resin lens Layers 1003a, 1003a'... Lens portion (resin lens layer)
1004... Back surface resin layer 1004a, 1004a'... Lens part (back surface resin layer)

Claims (13)

An optical writing device provided opposite to an image bearing surface formed of a side peripheral surface of a cylindrical photoreceptor for performing optical writing on the image bearing surface,
a light-emitting element substrate having light-emitting point groups arranged two-dimensionally ;
an imaging optical system that forms an image of the light from each light emitting point group on each different position on the image bearing surface;
The imaging optical system has a first lens array, a diaphragm substrate provided with a diaphragm aperture, and a second lens array, which are arranged in order from the light emitting element substrate side,
The first lens array and the second lens array are lens arrays in which a plurality of lenses are arranged two-dimensionally,
The first lens array is
a glass substrate;
a light shielding layer provided on one main surface side of the glass substrate and having a plurality of light ray passage apertures;
a resin lens layer provided on one main surface of the glass substrate provided with the light shielding layer and having lens portions arranged corresponding to the respective light ray passage openings;
and a back surface resin layer provided on the other main surface of the glass substrate ,
arranged with the light shielding layer facing the aperture substrate side,
The light emitting element substrate has a height sufficient to fill the space between the light emitting element substrate and the first lens array on the side of the first lens array, and a group of light emitting points provided on the light emitting element substrate. A light shielding body is provided that has a light shielding aperture with an enlarged aperture diameter toward the lens provided in the first lens array and shields the space between the lenses of the first lens array.
Optical writing device. The optical writing device according to claim 1, wherein the light shielding layer is a layer provided on one main surface of the glass substrate. The optical writing device according to claim 1, wherein the light shielding layer is a layer provided on a surface layer on one main surface side of the glass substrate. 4. The peripheral edge of each of the lens portions is arranged outside the light beam passage opening, and the light shielding layer and the peripheral edge of the lens portion overlap each other in a plan view. 2. The optical writing device according to item 1. 5. The optical writing device according to any one of claims 1 to 4, wherein each of said ray passage openings has an opening diameter that is long in one direction. 6. The optical writing device according to claim 5, wherein the lens portion has an elliptical shape in a plan view that is elongated in the same direction as the light beam passage opening. The optical writing device according to any one of claims 1 to 6, wherein the lens portion has a convex lens shape. 8. The optical writing device according to any one of claims 1 to 7, wherein the back resin layer has lens portions provided at positions respectively corresponding to the plurality of light passage apertures. The optical writing device according to any one of claims 1 to 8, wherein differences in refractive index between the glass substrate and the resin lens layer and the back resin layer are each 0.1 or less. The resin lens layer according to any one of claims 1 to 9, wherein the resin lens layer has a flat portion provided between the plurality of lens portions, and the thickness of the flat portion is 0.3 mm or less. optical writing device . 10. The optical writing device according to any one of claims 1 to 9, wherein the lens layer is formed in an island shape from which the lens portions are independent. each light-emitting point group of the light-emitting element substrate is formed by two-dimensionally arranging light-emitting points in an elongated shape along the axial direction of the photoreceptor;
2. The optical writing device according to claim 1 , wherein each ray passage opening of the light shielding layer has an opening diameter that is long in a direction along the axial direction of the photoreceptor, and is provided corresponding to the light emitting point group. . a cylindrical photoreceptor having a side peripheral surface as an image bearing surface;
an optical writing device provided opposite to the image bearing surface for performing optical writing on the image bearing surface;
An image forming apparatus, wherein the optical writing device is the optical writing device according to any one of claims 1 to 12 .

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