JP7135423B2 - Microlens array, optical writing device and image forming device - Google Patents

Description

The present invention relates to a microlens array, an optical writing device, and an image forming apparatus, and more particularly to a technique for preventing image deterioration caused by distortion of the microlens array.

2. Description of the Related Art Some electrophotographic image forming apparatuses use a line optical type optical writing device as an optical writing device for forming an electrostatic latent image on a photoreceptor. A line optical type optical writing device uses a microlens array to form an image of light emitted from a large number of light emitting elements on a photoreceptor.

This microlens array is, for example, formed by forming a large number of resin lenses on a glass substrate. Since the resin lens shrinks when it is cured, the position of the resin lens may change if the glass substrate warps due to this shrinkage. As a result, the imaging state on the photoreceptor changes, and the image quality may deteriorate.

To address such a problem, for example, with respect to the out-of-plane warpage of the glass substrate, a technique has been proposed in which resin lenses having the same shape are formed on both sides of the glass substrate (see, for example, Patent Document 1). With this arrangement, the shrinkage force of the resin acting on the glass substrate is the same on both sides of the glass substrate, so warping can be prevented.

In addition, with respect to warping in the in-plane direction of the glass substrate, when the number of resin lenses is sufficiently large, warping can be suppressed by randomly changing the shape of the resin lenses (for example, see Patent Document 2). reference).

JP 2011-118423 A JP 2005-148427 A

In an optical writing device in which light-emitting elements are periodically arranged two-dimensionally in a plan view from the optical axis direction of the microlens array, the distance from the light-emitting elements to the photosensitive member may differ among the light-emitting elements. For example, if a plurality of light-emitting element rows extending in the main scanning direction are arranged side by side in the sub-scanning direction and the distances from the light-emitting element to the photoreceptor are different between the light-emitting element rows, If the same number of resin lens rows extending in the main scanning direction as the light emitting element rows are arranged in the sub scanning direction, the resin lenses belonging to the same resin lens row have the same shape, while the resin lenses belonging to different resin lens rows have the same shape. It is necessary to make the shapes of the resin lenses belonging to each other different.

In such a case, it is not possible to make all the resin lenses have the same shape, and it is not possible to change the shape of the resin lenses at random. cannot be suppressed.

When the glass substrate warps in the in-plane direction, the positional relationship between the resin lenses changes, which causes variations in the positional relationship between the light emitting elements and the resin lenses corresponding to the light emitting elements. end up If there is periodicity in the change in the shape of the resin lens, the periodicity also appears in the density change due to the variation in the imaging performance, making it easier to visually recognize, which inevitably lowers the image quality.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems described above, and provides a microlens array, an optical writing device, and an image forming apparatus that can suppress image degradation caused by distortion of a glass substrate. With the goal.

To achieve the above object, a microlens array according to the present invention comprises a glass substrate, and a plurality of first resin lenses having the same shape are arranged along a first direction on a first substrate surface of the glass substrate. A plurality of resin lens rows are arranged in parallel in a second direction different from the first direction, and a plurality of second resin lenses are arranged on the second substrate surface of the glass substrate, respectively. a first resin layer integrally molded with the first resin lens and sandwiched between the first resin lens and the glass substrate; and the second resin a second resin layer molded integrally with a lens and sandwiched between the second resin lens and the glass substrate, wherein the first resin lens belonging to the plurality of resin lens rows has a large lens shape area The thickness of the first resin lens is different in the second direction and the resin volume is different between the first resin lenses. A resin lens row having a larger lens shape area has a thinner first resin layer interposed between the first resin lens belonging to the resin lens row and the glass substrate.

In this case, it is desirable that the height from the substrate surface of the glass substrate to the top of the first resin lens is the same regardless of the shape of the first resin lens.

Furthermore, regardless of the shape of the first resin lens, any two of the first resin lenses may be arranged from the interface of the lens portion that passes through the optical axis of each first resin lens and is in contact with the first resin layer. The distances to the vertex of the lens optical surface are L1 and L2, respectively, the lens shape areas of the first resin lenses are φ1 and φ2, and the areas of the first resin layer occupied by the first resin lenses are S1 and S2. When the thicknesses of the first resin layer are T1 and T2, it is desirable that the following relational expressions are satisfied but equal.

また、前記第１樹脂層は、前記ガラス基板の第１基板面に沿って複数の第１樹脂レンズに亘って連続的に設けられており、厚さが前記第２の方向に沿って連続的に変化していてもよい。

Further, the first resin layer is provided continuously over the plurality of first resin lenses along the first substrate surface of the glass substrate, and has a thickness that is continuous along the second direction. may have changed to

Further , the total volume of the first resin lens and the first resin layer provided on the first substrate surface is equal to the second resin lens and the second resin layer provided on the second substrate surface. It may be equal to the total volume of the resin layers.

Further, an optical writing device according to the present invention includes a microlens array according to the present invention, and a light source in which a light emitting point group including a plurality of light emitting points is arranged at each position corresponding to the first resin lens in plan view. and a substrate, wherein the distance from the light emitting point group to the first resin lens corresponding to the light emitting point group is different for each shape of the first resin lens.

In this case, the light source substrate may be composed of a plurality of unit substrates, and the light emitting point groups corresponding to the first resin lenses having different shapes may be arranged on different unit substrates.

Also, the light emitting point may be an OLED.

Further, an image forming apparatus according to the present invention is characterized by comprising the optical writing device according to the present invention.

In this manner, since the resin layer is thinner as the resin lens row has a larger lens shape area, the distortion of the microlens array can be suppressed by making the resin volume distribution uniform on the substrate surface of the glass substrate. can be done.

1 is a diagram showing the main configuration of an image forming apparatus according to an embodiment of the invention; FIG. 1 is a diagram showing the main configuration of an optical writing device 100; FIG. 3 is a diagram showing the main configuration of a light source substrate 230; FIG. 2 is a plan view of a lens array 200a viewed from the light source substrate 200 side; FIG. It is the top view which looked at the resin layer 262c from the optical axis direction. It is a figure explaining the dimension of the lens array 200a. 4 is a table illustrating dimensions of a lens array 200a; It is a figure which shows the structure of the microlens array based on the modification of this invention. It is a top view which illustrates the microlens array to which a P direction and a Q direction orthogonally cross. FIG. 10 is a plan view illustrating a microlens array having four rows of resin lenses in which resin lenses are arranged along the P direction; (a) is a table illustrating preconditions for designing dimensions of resin lenses and resin layers, and (b) is a table illustrating dimensions of resin lenses and resin layers that meet the preconditions shown in (a). is. (a) is a cross-sectional perspective view illustrating a mold in which the core blocks have the same height, and (b) illustrates a mold in which the height of the core blocks is adjusted according to the thickness of the resin layer. It is a cross-sectional perspective view.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a microlens array, an optical writing device, and an image forming apparatus according to the present invention will be described with reference to the drawings.
[1] Configuration of Image Forming Apparatus First, the configuration of an image forming apparatus according to the present embodiment will be described.

As shown in FIG. 1, the image forming apparatus 1 is a so-called tandem color printer. The image forming apparatus 1 includes image forming units 110Y, 110M, 110C, and 110K that form toner images of yellow (Y), magenta (M), cyan (C), and black (K). The imaging units 110Y, 110M, 110C and 110K have photosensitive drums 101Y, 101M, 101C and 101K that rotate in the arrow A direction, respectively.

Charging devices 102Y, 102M, 102C and 102K, optical writing devices 100Y, 100M, 100C and 100K, and developing devices are arranged in order along the outer peripheral surfaces of the photosensitive drums 101Y, 101M, 101C and 101K in the direction of arrow A. 103Y, 103M, 103C and 103K, primary transfer rollers 104Y, 104M, 104C and 104K, and cleaning devices 105Y, 105M, 105C and 105K are provided.

The charging devices 102Y, 102M, 102C and 102K uniformly charge the peripheral surfaces of the photosensitive drums 101Y, 101M, 101C and 101K. The optical writing devices 100Y, 100M, 100C and 100K are so-called OLED-PH (Organic Light Emitting Diode-Print Heads) using organic EL (Electro-Luminescence), and the photosensitive drums 101Y, 101M, 101C and 101K. The peripheral surface is exposed to form an electrostatic latent image.

Since the organic EL has an area in the light emitting portion, it differs greatly from other light emitting methods such as LED in that the beam diameter at the imaging point is determined by the light emitting area×optical magnification. In OLED-PH, even if the optical magnification must be changed for each light-emitting point due to different conjugate lengths, the beam diameter is made uniform by optimizing the light-emitting area and shape according to the optical magnification. be able to.

In addition, when the light emitting units having a large area are arranged in an array, the light source substrate tends to be large. By increasing the mounting area of the circuit components, the substrate area of the light source substrate in plan view from the optical axis direction is reduced.

The developing devices 103Y, 103M, 103C, and 103K supply YMCK color toners to visualize the electrostatic latent image and form YMCK color toner images. Primary transfer rollers 104Y, 104M, 104C and 104K electrostatically transfer the toner images carried by the photosensitive drums 101Y, 101M, 101C and 101K onto the intermediate transfer belt 106 (primary transfer).

The cleaning devices 105Y, 105M, 105C, and 105K remove residual toner as well as charge remaining on the outer peripheral surfaces of the photosensitive drums 101Y, 101M, 101C, and 101K after the primary transfer. It should be noted that the letters Y, M, C, and K will be omitted when describing configurations common to the image forming units 110Y, 110M, 110C, and 110K.

The intermediate transfer belt 106 is an endless belt, stretched around a secondary transfer roller pair 107 and driven rollers 108 and 109, and rotates in the arrow B direction. By performing primary transfer in accordance with this rotational movement, toner images of respective colors of YMCK are superimposed on each other to form a color toner image. The intermediate transfer belt 106 conveys the color toner image to the secondary transfer nip of the secondary transfer roller pair 107 by rotating while carrying the color toner image.

Two rollers forming the secondary transfer roller pair 107 are pressed against each other to form a secondary transfer nip. A secondary transfer voltage is applied between these rollers. When the recording sheet S is supplied from the paper feed tray 120 in timing with the conveyance of the color toner image by the intermediate transfer belt 106, the color toner image is electrostatically transferred to the recording sheet S at the secondary transfer nip (secondary transfer nip). transcription).

The recording sheet S carrying the color toner image is conveyed to the fixing device 130 , and after the color toner image is thermally fixed, the recording sheet S is discharged onto the discharge tray 140 .

The image forming apparatus 1 further includes a control section 150 . When receiving a print job from an external device such as a PC (Personal Computer), the control unit 150 controls the operation of the image forming apparatus 1 to form an image.
[2] Configuration of Optical Writing Device 100 Next, the configuration of the optical writing device 100 will be described.

As shown in FIG. 2, the optical writing device 100 includes a microlens array 200 and a light source substrate 230. The microlens array 200 and the light source substrate 230 are supported by a holder (not shown).

As shown in FIG. 3, the light source substrate 230 is obtained by laminating unit substrates 231, 232 and 233 in the optical axis direction. Light-emitting point groups 241 , 242 and 243 are arranged along the main scanning direction on the unit substrates 231 , 232 and 233 , respectively, forming light-emitting point group lines 251 , 252 and 253 . The light emitting point group 243 is obtained by arranging the light emitting points 303 in a zigzag pattern, and the light emitting point groups 241 and 242 are the same.

In this embodiment, an OLED (Organic Light Emitting Diode) is used as the light emitting point 303 . Since the OLED can form a light-emitting region in a planar shape, the beam diameter at the imaging point corresponding to the OLED can be set by setting the multiplication value of the area of the light-emitting region of the OLED and the optical magnification. can. Therefore, even if the optical magnification must be changed for each light-emitting point due to the different conjugate lengths, if the area and shape of the light-emitting region of the OLED are optimized according to the optical magnification, the beam at the imaging point can be reduced. There is an advantage that the diameter can be made uniform. A light-emitting element other than the OLED may be used as the light-emitting point.

In general, all light emitting points are arranged on the same plane, but due to wiring restrictions on the light emitting substrate, manufacturing restrictions, spatial restrictions when arranging the light emitting substrate, etc., all the light emitting points are placed on the same plane. If it is not suitable to dispose them inside, it is effective to distribute the light emitting points on a plurality of planes as in this embodiment.

Further, the light source substrate 230 is divided into unit substrates 231, 232 and 233 for each of the light emitting point group arrays 251, 252 and 253, and the unit substrates 231, 232 and 233 are located at distances L1, L2 and Positioned individually by a holder (not shown) so as to be L3. Distances L1, L2 and L3 are so-called conjugate lengths.

Therefore, the conjugate lengths of the unit substrates 231, 232 and 233 can be individually adjusted. For example, if an error such as a size occurs when manufacturing the microlens array 200 or the light source substrate 230, the light source substrate 230 is not divided into a plurality of unit substrates, and light emitting points with different conjugate lengths are mounted on the same substrate. Therefore, under the condition that the adjustment value is different for each level of conjugate length, the imaging performance in one of the routes must be sacrificed.

On the other hand, if the light-emitting points are grouped for each level of conjugate length and the light-emitting points are mounted on different unit substrates for each group as in the present embodiment, the adjustment value is individually set for each level of conjugate length. Therefore, each level of imaging performance can be optimized without sacrificing other levels of imaging performance. Such a configuration is not limited to the case where the number of unit substrates is three. It is also effective for adjusting the error of the shift component, which is the displacement, and the tilt component of the substrate surface with respect to the optical axis direction.

In addition, not only the conjugate length but also the shift component and tilt component errors can be individually corrected for each of the unit substrates 231 , 232 and 233 . Therefore, deterioration of image quality caused by these errors can be suppressed, and high image quality can be achieved.

In addition, the OLED has a relatively large light emitting point area, and a large number of OLEDs are arranged in an array. On the other hand, by arranging circuits such as wiring other than the OLED at the overlapping portions of the plurality of unit substrates 231, 232, and 233 as described above, the area of the light source substrate 230 viewed from the optical axis direction can be reduced. can be done.
[3] Configuration of Microlens Array 200 Next, the configuration of the microlens array 200 will be described.

The microlens array 200, as shown in FIG. 2, is a telecentric optical system combining lens arrays 200a and 200b. In the lens array 200a, resin lenses 211a, 212a and 213a are formed on the substrate surface 220a of the glass substrate 220 facing the light source substrate 230. As shown in FIG. The resin lenses 211a, 212a and 213a sandwich resin layers 261a, 262a and 263a with the glass substrate 220. As shown in FIG. If the resin lenses 211a, 212a and 213a and the resin layers 261a, 262a and 263a are integrally molded, the number of molding steps can be reduced, and cost reduction can be achieved.

Resin lenses 211b, 212b and 213b are formed at positions corresponding to the resin lenses 211a, 212a and 213a on the substrate surface 220b of the glass substrate 220 facing the lens array 200b. Resin layers 262b and 263b are sandwiched between the resin lenses 212b and 213b and the glass substrate 220 .

On the other hand, the resin lens 211b is a resin lens whose resin volume is larger than that of the resin lenses 212b, 213b, 211a, 212a and 213a, and is formed directly on the substrate surface 220b of the glass substrate 220 without sandwiching a resin layer. there is In this way, the volume of the resin in the microlens array 200 can be minimized, so the stress applied to the microlens array 200 due to contraction or expansion of the resin can be minimized. Also, the amount of resin used in the microlens array 200 can be reduced to reduce the cost, and the microlens array 200 can be made smaller and lighter. The resin lenses 212a and 212b make the emitted light of the light emitting point group 242 parallel light, and the resin lenses 213a and 213b make the emitted light of the light emitting point group 243 parallel light. The parallel light is imaged on the outer peripheral surface of the photosensitive drum 101 by the lens array 200b. The lens array 200b is obtained by forming resin lenses 251 on both surfaces 220a of a glass substrate 250. As shown in FIG.

The distance from the unit substrates 231 , 232 and 233 to the glass substrate 220 differs for each of the unit substrates 231 , 232 and 233 , while the distance from the glass substrate 250 to the photosensitive drum 101 is constant regardless of the resin lens 251 . there is Therefore, all the resin lenses 251 have the same shape. Therefore, even if the resin lens 251 shrinks or expands, the glass substrate 250 does not warp because the resin lenses have the same amount of contraction or expansion. On the other hand, the resin lenses 211, 212 and 213 formed on the glass substrate 220 have different shapes.

As shown in FIG. 4, the resin lenses 211a, 212a and 213a are arranged in rows in the main scanning direction, forming resin lens rows 401, 402 and 403, respectively.

Resin lens rows 401, 402 and 403 are arranged side by side in the sub-scanning direction. The resin lens rows 401, 402 and 403 are shifted from each other in the main scanning direction, and the optical axis centers of the resin lenses 211, 212 and 213 at the ends of the resin lens rows 401, 402 and 403 in the main scanning direction are connected. The direction Q obliquely intersects the arrangement direction P (main scanning direction) of the resin lenses 211 , 212 and 213 . In FIG. 4, the crossing angle of the directions P and Q is 30 degrees, but if the directions P and Q are not parallel, the crossing angle is 90 degrees (FIG. There may be.

In this manner, a plurality of resin lenses 211a, 212a and 213a are arranged two-dimensionally and periodically on the glass substrate 220, and are arranged side by side so as to correspond to the writing width on the outer peripheral surface of the photosensitive drum 101. there is Adjacent resin lenses along the direction Q have different shapes. These resin lenses are used to form an image of light emitted from light emitting point groups having different distances (conjugate lengths) to an image carrier (photoreceptor).

Resin layers 261a, 262a and 263a are also arranged similarly to resin lenses 211a, 212a and 213a. As shown in FIG. 5, the area occupied by each resin layer in plan view from the optical axis direction is the center 212cc of the resin lens 212c corresponding to the resin layer 262c and the centers of the resin lenses 212r and 212l adjacent in the direction P. Straight lines 502r and 502l passing through the midpoints 501b and 501d of 212rc and 212lc and along the direction Q, the center 212cc, and the centers 211c and 213c of the resin lenses 211 and 213 adjacent to the resin lens 212c in the direction Q. , and is surrounded by straight lines 502b and 502t along the direction P passing through the midpoints 501a and 501c . The regions occupied by the resin layers all have the same shape in plan view from the optical axis direction.

On the other hand, the resin layers 261a, 262a and 263a have different thicknesses, and the resin layers 262b and 263b have different thicknesses. In this embodiment, there is no resin layer corresponding to the resin lens 211b. In this sense, the resin layers corresponding to the resin lenses 211b, 212b and 213b have different thicknesses.

This is because the conjugate lengths from the light emitting point groups 241, 242 and 243 to the outer peripheral surface of the photosensitive drum 101 are different from each other, so that the resin lenses 211a, 212a and 213a have different shapes and the resin lenses 211b, 212b and 213b are different from each other. are different from each other, this corresponds to the fact that the volumes of these resin lenses are different from each other.

As for the thickness of each resin layer, the volume of the resin lens and the resin layer sandwiched between the resin lens and the glass substrate 220 is the same between the resin lenses. The thickness of the resin layer increases. In this way, the contraction force of the resin increases as the resin volume increases. can be suppressed.

Further, when the resin lenses are formed only on one substrate surface of the glass substrate 220, the microlens array 200 has a resin-glass two-layer structure. In this two-layer structure, when the temperature changes, the difference in linear expansion between the glass and the resin causes distortion such that the glass substrate 220 bends in the out-of-plane direction. On the other hand, if resin lenses are formed on both substrate surfaces so as to sandwich the glass substrate 220, a resin-glass-resin three-layer structure is obtained, and layers having the same coefficient of linear expansion exist with the glass sandwiched therebetween.

In this way, the difference in linear expansion that occurs on one side of the resin-glass layer acts in a direction that cancels out the difference in linear expansion that occurs in the glass-resin layer on the opposite side. can be done. In particular, in the present embodiment, the total resin volume is the same between substrate surface 220a and substrate surface 220b of glass substrate 220, and the difference in linear expansion between both substrate surfaces of glass substrate 220 is the same. Therefore, the distortion of the glass substrate 220 can be eliminated with higher accuracy.

In FIG. 6, on the substrate surface 220a of the glass substrate 220, the resin lens 211a has a core thickness L1a and a lens shape area φ1a. The resin lens 212a has a core thickness of L2a and a lens shape area of φ2a, and the resin lens 213a has a core thickness of L3a and a lens shape area of φ3a. The core thickness L is the thickness of the resin lens at the optical axis position, and is equal to the protrusion amount from the upper surface of the resin layer. Also, the lens shape region φ is the outer diameter of the region on the glass substrate 220 in which the resin lens has a shape.

The volume of the resin lens is determined by the square of the cross-sectional area of the cross section containing the optical axis, and the cross-sectional area is proportional to the product of the core thickness L and the lens shape area φ. It is proportional to the square of the product of L and the lens shape area φ (L×φ) ² . The volume of the resin layer is T×S obtained by multiplying the thickness T of the resin layer by the area S of the resin layer for each resin lens in plan view from the optical axis direction. As described above, since the area S of the resin layer is constant regardless of the corresponding resin lens, the volume ratio of the resin layer is proportional to the thickness T of the resin layer. Therefore, in order for the total resin volume of the resin lens and the resin layer to be equal, the sum of these ratios (L×φ) ² + T (2)
It is necessary to set the thickness T of the resin layer so that is equal between the resin lenses.

FIG. 7 is a table illustrating dimensions of resin lenses and resin layers according to the present embodiment. The height of the lens surface is the height from the main surface of the glass substrate 220 to the highest position of the resin lens. As shown in FIG. 7, by adopting the dimensions according to the present embodiment, it is possible to set the resin volume ratio of the resin lens and the resin layer to 1.00. Therefore, since warping of the microlens array can be suppressed, excellent image quality can be achieved.
[4] Modifications Although the present invention has been described above based on the embodiments, the present invention is of course not limited to the above-described embodiments, and the following modifications can be implemented. .
(4-1) In the above-described embodiment, the resin lens and the resin layer corresponding to the resin lens have the same resin volume as an example, but the present invention is limited to this. Needless to say, the following may be done in addition to this.

For example, the larger the resin volume of the resin lens, the smaller the resin volume of the resin layer corresponding to the resin lens. In such a microlens array, there are resin lenses with a lens shape area φ1 and resin lenses with a lens shape area φ2.
φ1 > φ2 (3)
Then, the thickness T1 of the resin layer corresponding to the resin lens having the lens shape area φ1 and the thickness T2 of the resin layer corresponding to the resin lens having the lens shape area φ2 are
T1<T2 (4)
It becomes a relationship like

By doing so, it is possible to reduce the difference in the resin volume, which is the sum of the resin lens and the resin layer, between the resin lenses having different resin volumes. Therefore, since the difference in shrinkage force and expansion force of the resin caused by the difference in resin volume is reduced, the amount of cooling shrinkage after injection molding and the amount of expansion when heat is applied can be reduced at any point of the microlens. It becomes isotropic, and the in-plane distortion of the microlens array can be suppressed.

Needless to say, the smaller the difference in the total resin volume between the resin lens and the resin layer, the higher the effect of suppressing the in-plane distortion of the microlens array. Therefore, it is sufficient to make the difference in resin volume small to such an extent that deterioration in image quality caused by distortion of the microlens array cannot be visually recognized.

When measuring the lens shape area φ of the resin lens constituting the microlens array, if the boundary between the resin lens and the resin layer is circular, the diameter of the boundary corresponds to the lens shape area φ, and a microscope or the like is used to measure the lens shape area φ. can be measured by optical observation. Further, when the boundary between the resin lens and the resin layer is polygonal, the polygon is approximated by a circle, and the lens shape area φ can be obtained by measuring the diameter of the approximated circle.

Regarding the thickness T of the resin layer, the thickness T of the resin layer can be measured with high precision by cutting the microlens array and optically observing the cross section of the microlens array using a microscope or the like. As a method for measuring the thickness T of the resin layer without destroying the microlens array, there is thickness measurement using a white light interferometer.

By measuring the lens shape area φ of the resin lens and the thickness T of the resin layer using the above method, it is confirmed whether the measured values satisfy the relationships of the above formulas (1) and (2). can do.
(4-2) Although not specifically mentioned in the above embodiment, the height from the substrate surface of the glass substrate 220 to the top of the resin lens may be the same for the resin lenses.

When molding the resin lens and the resin layer by injection molding using a mold, the core block is fitted into the mold to form the optical surface of the resin lens. By adjusting the position of this core block, the height of the top of the resin lens is adjusted. When molding a microlens array, the same number of core blocks as the number of resin lenses are fitted into a mold to mold the resin lenses. Therefore, if the height of the top of each resin lens is different, the height of the core block must be adjusted for each resin lens. becomes difficult to adjust accurately.

In addition, if the height of the apex is different for each resin lens, the thickness of the resin will be different for each resin lens. As a result, if resin lenses having different thicknesses are arranged in the pressurizing direction during molding of the microlens array, the load applied to the glass substrate during molding becomes non-uniform. As a result, there is also the problem that if the glass substrate cracks, the yield decreases.

To solve these problems, if the height from the substrate surface of the glass substrate 220 to the top of the resin lens is the same for each resin lens, it becomes unnecessary to adjust the height of the core block for each resin lens. , the dimensional accuracy of the microlens array can also be improved. In addition, since the load applied to the glass substrate during molding can be made uniform, cracking of the glass substrate can be suppressed and molding stability can be enhanced.
(4-2) In the above embodiment, the case where the thickness of the resin layer changes discontinuously between the resin lens rows has been described as an example. Alternatively, you can do the following:

For example, as shown in FIG. 8, on the substrate surface 220a of the glass substrate 220, resin lenses 211a, 212a, and 213a belonging to different resin lens rows are continuously provided along the substrate surface 220a. 260a, and the thickness of the resin layer 260a varies continuously along the sub-scanning direction. Similarly, on substrate surface 220b of glass substrate 220, resin lenses 211b, 212b, and 213b belonging to different resin lens rows are arranged on resin layer 260b that is continuously provided along substrate surface 220a. , and the thickness of the resin layer 260b changes continuously along the sub-scanning direction.

Therefore, needless to say, the thicknesses of the resin layers 260a and 260b other than the resin lenses change continuously in plan view from the optical axis direction. In order to continuously change the heights of the resin layers 260a and 260b, it is desirable that the conjugate lengths change monotonously along the sub-scanning direction.

In this way, the removal resistance during injection molding of the lens array can be reduced, so that the releasability can be improved. Therefore, when the same mold is repeatedly used to continuously mold a large number of microlens arrays, the shape of these microlens arrays can be stabilized and the life of the mold can be extended.
(4-3) In the above embodiment, the case where the resin lens 211b is directly formed on the substrate surface 220b of the glass substrate 220 has been described as an example. Alternatively, a resin layer may be sandwiched between all the resin lenses of the microlens array and the glass substrate.

With such a configuration, the resin layer becomes continuous for all the resin lenses formed on the same substrate surface. can be uniform along the Therefore, it is possible to more effectively suppress the occurrence of distortion in the in-plane direction of the glass substrate 220 .
(4-4) In the above embodiment, the three types of resin lenses 211a, 212a and 213a having mutually different shapes form the resin lens rows 401, 402 and 403 which are displaced from each other in the main scanning direction. has been described as an example, but the present invention is of course not limited to this, and may be replaced with the following.

For example, as shown in FIG. 9, the resin lens rows 401, 402 and 403 are not shifted in the main scanning direction, and the resin lenses 211, 212 and 213 at the ends of the resin lens rows 401, 402 and 403 in the main scanning direction. may be arranged so that the direction Q connecting the centers of the optical axes coincides with the sub-scanning direction.

Further, as shown in FIG. 10, four types of resin lenses 1011a, 1012a, 1013a and 1014a having different shapes form resin lens rows 1001, 1002, 1003 and 1004 which are displaced from each other in the main scanning direction. may be In any case, the effect of the present invention can be obtained by setting the thickness of the resin layer so that the resin volume of the resin lens and the resin layer corresponding to the resin lens is the same between the resin lenses. can be done.
(4-5) In the above embodiment, the resin lens rows 401, 402 and 403 are arranged on different unit substrates 231, 232 and 233, but the present invention is limited to this. Needless to say, the following may be used instead. For example, when there are a plurality of resin lens rows having the same conjugate length, it is desirable that the resin lens rows having the same conjugate length be arranged on the same unit substrate. In this way, the positions and inclinations of the unit substrates can be adjusted collectively for resin lens rows having the same conjugate length, so that the microlens array 200 can be efficiently manufactured without the need for adjustment.
(4-6) In the above embodiments, examples of dimensions of the resin lens and the resin layer have been described, but the present invention is not limited to this, and the following alternatives may be adopted. FIG. 11A shows dimensions that are prerequisites to be considered when determining the dimensions of the resin lens and the resin layer. where NAO is the F-number and NA is the effective F-number. The panel thickness, panel refractive index n, and panel-lens distance are dimensions related to the light source substrate, and the lens diameter R is the radius of curvature when the lens surface is the Kyo plane.

FIG. 11(b) exemplifies the dimensions of the resin lens and the resin layer that meet the above preconditions. For example, the distance between the apexes of the lens surface represents the distance in the P direction between the adjacent resin lenses. Further, the lens portion surface vertex distance (secondary) is the distance in the Q direction between adjacent resin lenses. In this way, the resin volume obtained by combining the resin lens and the resin layer can be perfectly matched in two significant digits, so that distortion of the microlens array can be suppressed and excellent image quality can be realized. can be done.
(4-7) In the above modified example, the case where the height of the core block is easily adjusted by aligning the tops of the resin lenses has been described as an example, but it goes without saying that the present invention is not limited thereto. Instead of this or in addition to this, the following may be done.

As shown in FIG. 12A, when molds 1201 and 1202 and core blocks 1200a, 1200b, and 1200c are used to mold a microlens array, resin lenses having resin layers with different thicknesses are separated from each other. If all of the core blocks used for molding have a height h, the height of each core block must be adjusted by the thickness of the resin layer.

For example, the top surface of core block 1200a is height Ha from the top surface of mold 1202, the top surface of core block 1200b is height Hb from the top surface of mold 1202, and the top surface of core block 1200c is height from the top surface of mold 1202. The heights of the core blocks 1200a, 1200b and 1200c must be individually adjusted so that the height is Hc. For this reason, it takes time and effort to adjust the height, and it is difficult to adjust the height with high accuracy.

On the other hand, as shown in FIG. 12(b), if the heights ha, hb and hc of the core blocks 1200a, 1200b and 1200c are set according to the thickness of the resin layer corresponding to the resin lens to be molded, the core blocks It is sufficient to individually adjust the heights of core blocks 1200a, 1200b and 1200c so that the top surfaces of 1200a, 1200b and 1200c are all at height H from the top surface of mold 1202. FIG. Therefore, it is possible to save the trouble of adjusting the height and improve the height accuracy.
(4-8) In the above embodiments, the resin layer of each resin lens has a parallelogram shape when viewed from above in the direction of the optical axis. However, the present invention is limited to this. Needless to say, it may be a shape other than a parallelogram. Further, the thickness of the resin layer corresponding to each resin lens does not need to be constant, and the smaller the resin volume of the resin lens, the larger the resin volume of the resin layer corresponding to the resin lens. If so, it is possible to obtain the effect of suppressing distortion of the microlens array due to expansion and contraction of the resin.

In order not to affect the optical characteristics of the resin lens, light rays passing through the lens surface of the resin lens must pass through interfaces other than the interface between the resin layer and the glass substrate among the interfaces between the resin layers. It is desirable to design the shape of the resin layer so that it does not occur. Specifically, it is preferable that all the lower surfaces of the resin lenses (virtual plane facing the glass substrate) are in contact with the upper surface of the resin layer (virtual surface in contact with the resin lenses).
(4-9) Although not specifically mentioned in the above embodiments, the following conditions must be satisfied in order for resin lenses to have the same resin volume, which is the sum of the resin lens and the resin layer.

In the resin volume VL of the resin lens, the distance from the interface of the lens portion that passes through the optical axis of the resin lens and is in contact with the resin layer to the apex of the lens optical surface is L, and the lens shape area of the resin lens is φ. sometimes,

である。

is.

Further, when the area is S and the thickness is T, the resin volume VT of the resin layer is

であるので、樹脂レンズと樹脂層とを合わせた樹脂体積は、

Therefore, the total resin volume of the resin lens and the resin layer is

である。

is.

Therefore, the following relational expression must be satisfied in order to equalize the resin volumes of the resin lenses and the resin layers of different resin lenses.

ここで、各樹脂レンズの光軸を通過して樹脂層と接しているレンズ部界面からレンズ光学面頂点までの距離がそれぞれＬ１、Ｌ２であり、各樹脂レンズのレンズ形状域がφ１、φ２であり、各樹脂レンズが占有する樹脂層の面積がＳ１、Ｓ２であり、当該樹脂層の厚さがＴ１、Ｔ２である。

Here, the distances from the interface of the lens portion that passes through the optical axis of each resin lens and is in contact with the resin layer to the apex of the lens optical surface are L1 and L2, respectively, and the lens shape areas of each resin lens are φ1 and φ2. , the area of the resin layer occupied by each resin lens is S1 and S2, and the thickness of the resin layer is T1 and T2.

By doing so, it becomes possible to optimize the thickness of the resin layer and the lens parameters when minimizing the difference in resin volume between the resin lenses.
(4-10) In the above embodiment, the image forming apparatus 1 is a tandem color printer, but the present invention is not limited to this. It may be a color printer or a monochrome printer. The present invention can also be applied to a single-function machine such as a copier equipped with a scanner, a facsimile machine further equipped with a facsimile communication function, or a multi-function peripheral (MFP: Multi-Function Peripheral) having these functions. effect can be obtained.

INDUSTRIAL APPLICABILITY The microlens array, optical writing device, and image forming apparatus according to the present invention are particularly useful as devices that can prevent image deterioration caused by distortion of the microlens array due to contraction or expansion of the resin.

1................................................................. Image forming apparatus 100................................................................. . ……Microlens arrays 220, 250 …………………………Glass substrates 211a, 212a, 213a…………Resin lenses 211b, 212b , 213b, 251......Resin lenses 261a, 262a, 263a, 262b, 263b...Resin layer 230....................................................................Light source substrate 231, 232, 233 ……………… Unit substrates 241, 242, 243 ……………… Light emission point group 303 ……………… ……………………Light emitting point (OLED)
L1, L2, L3 ………………………… Conjugation length

Claims (9)

a glass substrate;
On the first substrate surface of the glass substrate, a plurality of resin lens rows in which a plurality of first resin lenses having the same shape are arranged along a first direction are arranged in a second direction different from the first direction. Along with being arranged in rows,
a lens optical system in which a plurality of second resin lenses are arranged at positions corresponding to the first resin lenses on the second substrate surface of the glass substrate;
a first resin layer integrally molded with the first resin lens and sandwiched between the first resin lens and the glass substrate;
a second resin layer integrally molded with the second resin lens and sandwiched between the second resin lens and the glass substrate;
The first resin lenses belonging to the plurality of resin lens rows have different lens shape area sizes in the second direction, and the first resin lenses have different resin volumes. In order to reduce the difference in resin volume including 1. A microlens array characterized by having a thin resin layer. 2. The microlens array according to claim 1, wherein the first resin lenses have the same height from the substrate surface of the glass substrate to the tops of the first resin lenses regardless of their shapes. Regardless of the shape of the first resin lens, between any two first resin lenses,
L1 and L2 are the distances from the interface of the lens portion passing through the optical axis of each first resin lens and in contact with the first resin layer to the apex of the lens optical surface,
The lens shape regions of the respective first resin lenses are φ1 and φ2,
When the areas of the first resin layers occupied by the respective first resin lenses are S1 and S2, and the thicknesses of the first resin layers are T1 and T2,
satisfies the following relations

3. The microlens array according to claim 1 or 2, characterized in that: The first resin layer is provided continuously over the plurality of first resin lenses along the first substrate surface of the glass substrate, and has a thickness that varies continuously along the second direction. 4. The microlens array according to any one of claims 1 to 3, characterized by: The sum of the volumes of the first resin lenses and the first resin layer disposed on the first substrate surface is the sum of the volumes of the second resin lenses and the second resin layer disposed on the second substrate surface. 5. The microlens array according to any one of claims 1 to 4, wherein is equal to . a microlens array according to any one of claims 1 to 5;
a light source substrate on which a light emitting point group composed of a plurality of light emitting points is arranged at each position corresponding to the first resin lens in plan view,
The optical writing device according to claim 1, wherein the distance from the group of light emitting points to the first resin lens corresponding to the group of light emitting points is different for each shape of the first resin lens. The light source substrate is composed of a plurality of unit substrates,
7. The optical writing device according to claim 6, wherein the light emitting point groups corresponding to the first resin lenses having different shapes are arranged on different unit substrates. 8. An optical writing device according to claim 6, wherein said light emitting point is an OLED. An image forming apparatus comprising the optical writing device according to claim 6 .

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